SOIL TES'I TIIEORY anld CALIBRATION for Cottonl, Corn, Soibean and Coastal Berniudagrass )~A! (, N BULLETIN 375 FEBRUARY 1968 AGRICULTURAL EXPERIMENT STATION A UB U RN E. V. Smith, Director U NI V ERS IT Y Auburn, Alabama CONTENTS Page W HAT Is SOIL TESTING?------------------Samp le .- - - - - - - - - - - - - ----4 Th e -- - - ---- --- -5 -- --- --- ---The M easurem ent - - - -- - - -- - - -- - - -- - - -- - - -- - - - 5 The Recommendation ----------------------6 FOR COTTON- SOIL TEST CALIBRATION 10 Relationship Between Soil Test P and Relative YieldRelationship Between Soil Test K and Relative YieldResponse to P and K at Various Soil Test Levels-12 - - --- ---- --Value of Soil Fertility--Fertility Depletion, Maintenance, and Buildup Effect of Fertility on Factors Other Than Yield-17 Rate of Fertilizer Needed vs. Soil Fertility-17 Method of Fertilizer Application-Effect of Weather on ResponseSkip-Row Planting-- - - --- -- --- -- --- - --- -- -Irrig ation -- - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - - - - Nitrogen Soil Acid ity -- - -- - -- - -- - - -- - -- - -- - - - -- -- - Magnesium Micronutrients --- --- --- --- -- --- --- --- -- --- --- -SOIL TEST 10 11 -14 15 19 20 -21 -21 - 22-----23 25----------------25 25 Corn Response to N-P-K Compared with Cotton-26 Relationship Between Soil Test P and Relative YieldRelationship Between Soil Test K and Relative YieldResponse to P and to K at Various Soil-Test Levels-28 Fertility Depletion, Maintenance, and Buildup-29 Effect of Fertility on Factors Other Than Yield-29 Rate of Fertilizer Needed vs. Soil Fertility-30 Method of Fertilizer Application-31 -Effect of Weather on ResponseIrrigation Corn Silage -- -- - -- -- - -- - -- -- - -- -- - -- - -- -- -- -- -- - -- -- --Nitrogen and Spacing--Soil Acidity-33---------------Magnesium .------------------------Micronutrients-34--------FOR SOYBEANS-35 CALIBRATION FOR CORN-- 27 27 31 2--32 -33 34 SOIL TEST CALIBRATION Relationship Between Soil Test P and K and Relative Yield Response at Various Soil Levels .-- --------------- 35 Fertility Depletion, Maintenance, and Buildup--------------37 Rate of Fertilizer Needed vs. Soil Test---------------------38 M ethod of A pplication-----------------------------------38 N itro ge n -- - - - - - - - - - - - - - - - - - - - - - -. - - - - - - - - - - - - - - - - - - - - - - -3 8 S o il A cidity -- - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - 3 8 M icronu trients --- - -- - - - - - - -- - -- - -.- -- - -- - - -- - - - - - - - - - - - -- 39 SOIL TEST CALIBRATION FOR COASTAL BERMUDAGRASS ----------- 39 Relationship Between Soil Test P and K, and Relative Yield Response at Various Soil Levels-------------------40 Fertility Depletion, Maintenance, and Buildup -------------. 42 Effect of Fertility on Factors Other Than Yield-------------43 Nitroge n . - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 45 S o il A cidity -- - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - -- - - - - - - - 4 5 O ther Elem ents ----------------------------------------- 46 SUMMARY AND CONCLUSIONS---------------------------------46 ACKNOW LEDGM ENTS-----------------------------------------4 LITERATURE CITED------------------------------------------47 6 A PPEN D IX - - - - - - - - - - - - - - - - - - - - -- -- ----- -- -- -- -- --I- - - --FIRST PRINTING 5M, February 1968 51 SOIL TEST THEORY and CALIBRATION for Cotton, Corn, Soybeans and Coastal Bermnudagrass R. D. ROUSE* THE 1930's soil testing has increased steadily in the United States. Nearly 3 million soil samples were tested in this country in 1963 (15), which is twice the number in 1955. A soil testing laboratory was established for Alabama at Auburn University in February, 1953. The increase in number of samples tested annually is shown in Figure 1. In 1963 the Alabama State Board of Agriculture and Industries offered a certification program for commercial laboratories operating in Alabama. This program provides a means of officially recognizing laboratories equipped and staffed to produce reliable analyses and to make recommendations based on the latest research available from the Agricultural Experiment Station. Despite availability of the Auburn University Laboratory and the certified facilities, the number of soil samples submitted for analysis and recommendations has never approached the number needed to provide a reliable guide for use of lime and fertilizers on all fields. For;instance, the total number of samples processed in 1965 by the University and commercial laboratories represent only about 1 sample for each 5 farmers, 1 sample for each 200 acres of crop and pasture land. One major reason for this is not understanding the basis for soil testing and the benefits from it in practical farm operations. Soil scientists recognize that there is nothing comparable to soil testing as a guide for lime and fertilizer use. This bulletin presents a general theory of soil testing as the basis for lime and fertilizer recommendations in Alabama. Four crops are used to represent a wide range of plant requirements and value per acre. SINCE Director, formerly Professor, Department of Agronomy and Soils, Auburn University Agricultural Experiment Station. *Associate 4 ALABAMA AGRICULTURAL EXPERIMENT STATION 32 24 YEARS FIG. 1. Annual number of soil samples received in Soil Testing Laboratory at Auburn University. WHAT IS SOIL TESTING? To the grower soil testing is the process of collecting a sample of soil, sending it to a laboratory, and receiving an evaluation of fertility together with lime and fertilizer recommendations. To the soil scientist soil testing involves the process of quantitatively relating all known soil fertility information influencing plant growth to soil properties that can be measured in the laboratory. It also involves consideration of the response of crops to fertilizer materials and how this response is influenced by method and time of application with respect to various soil properties. This is considered in a general way under three headings: (a) The soil sample. How can a sample be collected that will represent a field or plot of ground? (b) The chemical measurement. How can chemical values be obtained that will give an indication of the relative availability of the element in the soil to plants? (c) The recommendation. What is required to arrive at a treatment that will be the best soil fertility management practice? SOIL TEST THEORY and CALIBRATION 5 The Sample Proper collection of a soil sample is one of the most important steps in soil testing. A valid sample must represent the area that is sampled. The probability that one scoop of soil from a field will be representative of all soil in that field is extremely small- even in an apparently uniform field. To increase the probability of a sample representing the soil in a field, either size of the sampled area must be reduced or scoops of soil collected from several places in the field and mixed to form a composite sample. Research conducted to determine practical limits to size of fields and number of places from which soil should be collected to make a composite sample shows that on a field scale regardless of acreage soil from about 20 sites would be required to make a single sample representative of the field (14,22,27,30,37,46). The area that can be fairly represented by one composite sample decreases with increased variability of the soil within the area. It may be a few square feet or a hundred acres. A basic concept of good soil sampling is that one sample can represent only one condition. Results of soil sampling studies show that, in general, large and apparently uniform fields must be sampled to represent no more than 10 acres at first sampling. If samples from such areas are found similar in soil test values and if the separate areas are subsequently managed similarly, a composite sample can be taken thereafter to represent the larger area. For high value crops or special situations, smaller size sampling areas may be justified. In any field an apparent nonuniformity of significant size would require separate sampling. Frequently a corrective treatment can be made that will justify subsequent treatment of the unusual area the same as the large area. In short, a scil sample can be collected that represents a field, but for it to be a valid sample of the area it must be deliberately collected to represent the field. The Measurement Although soil and plant scientists for more than 100 years have been studying procedures by which chemical characteristics of soil can be related to plant growth, it was not until 1930 when it became apparent that extractions made with salt solution or weak acids gave chemical values of some meaning. With this 6 ALABAMA AGRICULTURAL EXPERIMENT STATION as a basis, a number of chemical procedures have been devised that give values highly correlated with the soil's capacity to supply a given nutrient. Methods being used currently in the Southern Region are summarized in Southern Cooperative Series Bulletin 102 (34). The Recommendation With suitable extractants and analytically accurate methods of analysis, it is possible to relate soil chemical values to lime and fertilizer needs. To accomplish this, the soil test value must give a measure of two interrelated soil properties (7): (a) the severity of the deficiency, i.e., how much yield increase will be obtained if the deficiency of the nutrient is corrected; and (b) the amount of fertilizer required to correct the deficiency. Extensive research is required to accurately relate soil test values to severity of deficiency and to the required addition of fertilizer. The experimental process whereby these two relationships are established and combined to provide the basis for recommendation is termed soil test calibration. Discussion of the two primary steps follows. How Deficient is the Soil? To establish the relationship between a soil test value and response to additions of this nutrient requires that yield responses of a crop be obtained on the same soil type but having a wide range of soil test values. Unfortunately, the necessary range of values cannot usually be obtained at a single experimental site, but results from several locations must be used. Since other environmental conditions vary from site to site, actual yields cannot be used as a basis for comparisons. Yield response can be compared by converting actual yields to relative yields (the highest yield at each location is assigned a value of 100 and all other yields at that location are then related to the highest). Justification for this has been adequately described by Bray (9). The relationship between chemical soil test values and soil fertility levels are usually described in such terms as low, medium, or high. Additional terms may be desirable sometimes, e.g., very low, low, medium, high, very high, and very, very high. For soil testing to be quantitative, the terms used to describe the chemical values must be defined in terms of sufficiency for plant growth. In Alabama soil test terms have been defined as follows: SOIL TEST THEORY and CALIBRATION 7 (a) "very, very high" means an excessive amount of the nutrient in the soil and further additions may be detrimental; (b) "very high" means the nutrient supply is adequate and further additions should not be made until the soil test value is lowered; (c) "high" means the nutrient supply is adequate for highest yields, but there might be some advantage to a starter application or a maintenance application of fertilizer to keep the soil fertility level high; (d) "medium" means the soil will produce 75 to 100 per cent of the yield potential without addition of the element; (e) "low" means the soil will produce 50 to 75 per cent of the yield potential; (f) "very low" means the soil will yield less than 50 per cent of maximum. Where the value of the crop is high in relation to cost of fertilizer or when only a small amount of fertilizer is needed even for a "low" value, only three categories are needed: (a) "low" to mean that a yield increase is expected from an application of the element; (b) "high" to mean that a maintenance or starter application is desirable; (c) "very high" to mean that no fertilizer is needed. Use of descriptive terms such as low, medium, and high in soil test calibration has a serious limitation. During the period that soil testing has been developing, varying concepts have been associated with these terms. This problem has been recognized for more than 30 years. In 1935 Morgan (32) suggested a scale of 1-10 with 8 equal to the point of no response. Illinois (7) has long related-soil test to relative yield with 100 assigned to the point of no response. Relative yield was selected as a basis for describing soil test calibration in Alabama. This has the desirable connotation of indicating the expected relative yield without additions of the element whereas above 100 indicates the relative margin of adequacy or the nearness to an excessive level. To eliminate the need for a per cent sign, the values are referred to as "Fertility Index." The Fertility Index can be related to the previous definitions of low, medium, and high as follows: less than 50, very low; 50-75, low; 75-100 medium; 100-300 high; 300600, very high; and greater than 600 very, very high. Since this will be new to many readers of this publication, both Fertility Index and low, medium, and high are shown in Figure 2a. Research results have shown that a given chemical value has a different means in regard to crop response to additions of the element for different soils with a given crop and for different crops with a given soil (16,35,41,49). Based on this research, Alabama 8 ALABAMA AGRICULTURAL EXPERIMENT STATION i rRelative Yield ivv E -- -ow- --- i--- .-- 50 II 50 Hih I ,5 lb nex? 0 160 2b 75-100 150 3b4 Fertility Index I4 100 -RelativeYield Sail Test Value (a) Yield related to sail test value Medium Sail Inde Low Sail Index C 75 50 I lx 5x Fertilizer Rate 4x 3x 2x Fertilizer Rate (b) Yield related ta fertilizer rate at 3 different sail I 1ilInc~p5-0 test levels I 4x \ 3x f Imo-Medium-~ 2x LowH g --50 75 lb 100 Soil Test Ra ting 150 Fertility Index 4b 2b 3b SailI Test Value (c) Fertilizer rate related to soil test value by combining the relationship found in (a) and (b) FIG. 2. Three steps in soil calibration. SOIL TEST THEORY and CALIBRATION 9 soils have been grouped into three general categories for the purpose of calibrating chemical soil tests (41). I. Sandy Coastal Plain soil - Soils of this group have exchange capacities less than 6 meq. per 100 g. II. Clay Loam Coastal Plain soils, Piedmont soils, Appalachian Plateau soils, grey and brown soils of the Limestone Valleys, Highland Rim soils, and lime soils of the Black Belt and Limestone Valleys - Soils of this group, in general, have exchange capacities between 6 and 12 meq. per 100 g. However, the lime soils of the Black Belt and Limestone Valleys have exchange capacities up to 30 or 40 meq. per 100 g. III. Red soils of the Limestone Valleys and acid soils of the Black Belt Soils of this group have exchange capacities greater than 12 meq. per 100 g.; frequently the acid clay soils of the Black Belt will have exchange capacities up to 40 meq. per 100 g. Results from studies in this laboratory have shown that relationship between these three soil groups change with soil test methods. The phosphorus (P) values obtained from extracting acid soils with a weak acid (0.05 N HCl + 0.025 NH 2SO4 ) using a 1:4 soil-solution ratio, shaking for 5 minutes, and filtering immediately can be converted to approximate Truog P values by multiplying Group I and II soils by 0.8 and Group III soil by 1.60. Potassium (K) values for acid soils can be converted approximately to exchangeable K values by multiplying Group II soils by 1.25 and Group III soils by 1.33. Group I soils require no factor. The acid-extracting solution is not suitable for use on high lime soils. Sodium bicarbonate (0.5 N NaHCO3, pH 8.5) is used for P and ammonium acetate (1.0 N, pH 7) is used for K and Mg. Differences in the relationship between chemical soil test values and soil fertility is discussed later by crops. Yield Response to Application of Fertilizer. After chemical soil test values have been related to relative yield, results of field experiments are needed to show response to applications of the element at various soil test values as shown diagrammatically in Figure 2b. This provides information on efficiency of applied fertilizer at various soil tests for the particular method of fertilizer application employed. The information is necessary to predict the amount of nutrient required to obtain practical maximum yields. Such response studies must be carried out under soil conditions similar to those where the crop will be grown because soil in place has an effect on actual nutrient availability and on root distribution. This means that to recommend a soil 10 ALABAMA AGRICULTURAL EXPERIMENT STATION management treatment, the chemical values must be related to data collected from field experiments (10,11). When relative yield of the crop has been related to chemical soil test values and relative yield of the crop related to rate of application of the nutrient needed to obtain maximum response, then the relationship desired for calibration can be described, i.e., soil test value vs. rate of application of the nutrient required for maximum yield. The data available indicate that this is a linear relationship; however, in plotting, the calibration curve, the need for soil fertility buildup with a low fertility index and maintenance under high fertility index are taken into consideration. This is illustrated diagrammatically in Figure 2c. Data available in Alabama on cotton, corn, soybeans and Coastal bermudagrass are presented similarly. These crops vary in response to applications at given soil test values and in amounts of the elements required to maintain soil levels and yields. SOIL TEST CALIBRATION for COTTON The research data on phosphorus (P) and potassium (K) for cotton are more comprehensive than for other crops. It serves as a basis for cotton recommendation and as a guide for research on other crops and other elements. Farmers have not made full use of this information since no more than one sample for each 140 acres of cotton has been tested annually. In spite of this, the state average yield of cotton has increased significantly in recent years. This has been the result of limiting acreage and adoption of several improved production practices. However, considering changes in lime and fertilizer use, there can be no question but soil testing has had its influence. Relationship Between Soil Test P and Relative Yield The relationship between soil test P and yield of cotton based on data obtained where yields range between 11/4 and 13/4 bales of cotton per acre is shown in Figure 3. The numbers in the plotted points in the figure refer to the experiments described in Appendix Table 1. The data from Groups I and II and Group III soils have been equated by adjusting the scale of the x-axis. The curve shown is calculated by a modification of Mitcherlich's equation, as proposed by Bray (8). The equation is as follows: SOIL TEST THEORY and CALIBRATION SOIL TEST THEORY and CALIBRATION 11 11 FIG. 3. Relationship between soil test P, and relative yield of cotton. Log (A-y) = log A - cb; where A = 100%; y the percentage yield of the no P or no K treatment; b = the soil test value of the corresponding plot; and c - the proportionality constant. By solving for c on each experiment and averaging the values, a mean c value was obtained. This value was used to calculate response curves. The fit of the data around the curve indicates that the equation describes the relationship with reasonable accuracy. Using the definitions previously given, a soil test P for Group I and II soils below 5 ppm would be very low and have a fertility index of 50 or less, 5 to 10 ppm would be low and have a fertility index between 50 and 75, 10 to 30 ppm between 75 and 100 or medium, 30 to 90 ppm between 100 and 300 or high, 90 to 270 ppm between 300 and 600 or very high. Values for Group III soil would be one-half that of Group I and II soils. This is shown in Figure 3. Relationship Between Soil Test K and Relative Yield The relationship between yield and soil test K is shown in Figure 4. The points in the figure refer to experiments described in Appendix Table 2. The three different soil groups are equated by adjusting the scale on the x-axis. The dotted line shown is the curve calculated by Mitscherlich's equation. The calculated line from Bray's equation does not provide the best possible fit of the data since the equation forces a zero intercept for (x, y). Based on observation and experience of the writer, a soil test K of about 15 ppm for Group I soils is the 12 12ALBM ALABAMA AGRICULTURAL EXPERIMENT STATION AGIUTRLEPRMNSTTN IGroup K (ppm) FERTILITY INDEX Group I Soils II Soils Group III Soils FIG. 4. Relationship between soil test K and relative yield of cotton. minimum level to which the soil can be depleted by cotton. If Mitscherlich's equation is modified to Log A-yLog A-c (b-15), then the curve approaches y= 0 at x- 15 and appears to provide the best estimate of relationship described by available data. For soil test K on Group I soils using the relationship as calculated by the modified Mitscherlich equation 20 ppm would be assigned a fertility index of 40, 30 ppm would be assigned a fertility index of 75, and 60 ppm would be assigned a fertility index of 100. Response to P and K at Various Soil Test Levels The foregoing information provides a basis for describing soil test P and K in terms of sufficiency in the soil for maximum production. It does not indicate the addition needed to produce the yield potential on a soil that is deficient in some degree. To provide a basis for recommending specific rates at certain soil test values, rate studies have been carried out at several soil test levels in recent years. The response to P at different soil test levels is shown in Figure 5 and to K in Figure 6. The differences SOIL TEST THEORY and CALIBRATION 13 SOIL TEST THEORY and CALIBRATION 100 RELATIVEYIELD M Hig 1 L o F 90 ILow Roting- L ow_ 3 L ocotionsWthFrtlt Index .75 Medium/ L ocation Wt etlt 80 Index Between 75 and /00 High _7 Locations With Fertility Index ~/00 024060 P Lb/A. (P x2.24=P2 0 5 ) 80 FIG. 5. Response of cotton to rates of P on soils testing low, medium, or high. 100 90 80 7060 50 410 RELATIVE YIELD High Medium Low 20 10 0 RatingLow- 6 /Lo ?ca/ions With Fertility /ndex r 75__ Med-9 /Lo ca/ions With Fertility xBetween 75 .and /00 /neHigh2 Lc wcations With Fertility 100 /nde Odx C ) 40 60 120 80 K Lb./A. (K X I2= K20) 200 FIG. 6. Response of cotton to rates of K on soils testing low, medium, or high. 14 ALABAMA AGRICULTURAL EXPERIMENT STATION in amount of P and amount of K required to correct a deficiency reflects the more usual soil conditions found at the time these studies were initiated, i.e., low P sites were relatively not as deficient in P as low K sites were in K and high P sites were more common than high K. It also reflects a difference in amounts of elements required to cause a given change in production. With these two sets of results, (a) the relationship between relative yield and soil test value and (b) the amount needed as fertilizer to supplement what the soil can supply, the information needed for making a recommendation is available. This is true if the yield level is satisfactory. However, since these relationships are presented on the basis of relative yield, no assurance is given in the data as presented that actual yield potential is at the level desired. Therefore, it is logical to ask if there would be a yield or quality advantage for a higher soil test value than that found. This leads to three additional questions: (a) Should the recommendation take into consideration a need for soil fertility building? (b) Is the soil supply sufficient that some soil depletion can be tolerated? (c) Should the recommendation provide for soil fertility maintenance even though none is needed for yield or quality? Value of Soil Fertility Studies have been conducted to determine the value of K soil fertility. In general, if the soil level is sufficient to produce 75 per cent or more of the yield potential, there would not be a yield benefit from applying more of the element than needed for direct yield response and to maintain soil fertility. However, if the fertility index is less than 75, a yield benefit to succeeding crops can be expected from applying a treatment to increase soil fertility (38,41). Data from P studies have not shown the advantage for soil buildup where the fertilizer is drilled, as evidenced in K studies. Considering the difference in the chemistry of these two elements, the need for P buildup using drilled fertilizer should not be as critical as that for K even though the plant obtains both elements primarily by diffusion to the roots. Ensminger and Hood' have shown this is not true from broadcast applications. Where P is broadcast fertility buildup is important. There is evidence that continued soil P buildup can have an adverse effect on yield. At location 3 (Prattville) where P was well in 1 Unpublished data. SOIL TEST THEORY and CALIBRATION 15 the high range, yields of cotton, even after 8 years of continuous cropping, were highest where no P was applied. Earlier studies showed that Fusarium wilt increased as P increased but decreased with increasing K (48,55). There was no indication that this accounted for lower yields in this study where a wilt-resistant variety was used. Fertility Depletion, Maintenance, and Buildup The previous sections have shown that soil fertility is important in crop production and that fertility buildup and depletion 60-Soil Test P (ppm) Fertility Index Soils Grc I II I 0 IQ 20 30 P Annually Ib/A 40 FIG. 7. Change in soil test P from eight annual applications to continuous cotton. 16 ALABAMA AGRICULTURAL EXPERIMENT STATION does occur. Therefore, knowledge concerning rate of depletion and buildup under a particular cropping practice is needed to develop a recommendation designed to build, maintain, or prevent depletion of soil fertility to an undesirable level. The buildup and depletion of P and K associated with cotton grown annually are illustrated in Figures 7 and 8. These show a Soil Test K (ppm) Index Soils Group II III Group Group II Initial 1954Initial 1954 /0 L0 110 0 / / / 1 7 / 6O / IO01 SInitial 1954 0 / Group I75 0 20 40 60 K Annually lb/A 80 FIG. 8. Change in soil test K from eight annual applications to continuous cotton. SOIL TEST THEORY and CALIBRATION 17 summary of buildup and depletion data at 7 locations over an 8-year cropping period, 1954-61.2 In this study about 5 pounds of P and 10 pounds of K per acre annually would have prevented depletion. Buildup during 8 years for both P and K averaged approximately 0.2 pounds for each pound applied annually. The comparison of the individual data from these experiments is presented in the Appendix Figures 1-7. Similar results have been shown in previous studies (16,39,41). These data show that buildup and depletion of P and K are gradual processes when rates of application are in the range of 0 to 5 times the annual removal. These elements are held by the soil and are capable of being built-up since cotton is relatively nondepleting. This means (a) if the soil is just above the point where a response to additions is obtained, then an annual maintenance application about equal to that removed by the harvested crop would maintain fertility; and (b) if the soil value is well above the point of no response, there need be no fear or depleting fertility in a single year, and no benefit would be derived from applying a maintenance application if resampling is done every 3 years. Effect of Fertility on Factors Other Than Yield Effect of soil fertility level or treatment on quality of product or plant characteristics that affect quality or suitability for harvest is of practical concern. Studies conducted to determine the effect of increasing applications of N and K and irrigation on fiber quality and lint percentage of cotton have shown no effect on fiber quality above a fertility index of 75 or a medium rate of application although lint percentage was decreased by increasing each of these factors (6,43). There has been no indication of the effect of K on resistance to lodging or stem strength as has been reported for some other crops. There has been evidence of delayed maturity from high applications of K, N, and water. However with boll weevil control and timely defoliation to control boll rot, delayed maturity should not necessarily result in an adverse effect on yield or quality. Rate of Fertilizer Needed vs. Soil Fertility Soil test values have been related to rates of P and K needed 2N-P-K experiments conducted at Brewton Experiment Field, Brewton, Ala.; Monroeville Experiment Field, Monroeville, Ala.; Prattville Experiment Field, Prattville, Ala.; Wiregrass Substation, Headland, Ala.; Upper Coastal Plain Substation, Winfield, Ala.; Sand Mountain Substation, Crossville, Ala.; and Tennessee Valley Substation, Belle Mina, Ala. 18 18 ALABAMA ALABAMA AGRICULT AGRICULTURAL EXPERIMENT STATION FIG. 9. Annual rate of P for various soil test values-cotton. by considering the rate of fertilizer from which a response is obtained at various soil test values and need for soil fertility improvement and maintenance. In Figures 9 and 10 the points FIG. 10. Annual rate of K for various soil test values-cotton. SOIL TEST THEORY and CALIBRATION 19 show rate to which a response was obtained. The straight line is the best estimate of average yield response to direct application. The scatter of points about this line indicates the need for further research to define the exact position of this line. The line is drawn without giving weight to the points where only 1-year yield response was obtained. The calibration curve is drawn to allow for needed buildup at low soil test values and maintenance at high values. It is deliberately drawn above the line showing actual yield response as a safety precaution to allow for some field variation and sampling error. Method of Fertilizer Application Data reported here were obtained in experiments with all of the fertilizer except N applied in a band at planting time. Usually one-third or one-fourth of the N was applied at planting and the remaining N was applied as sidedressing 4 to 6 weeks after planting. For other methods all factors influencing fertilizer needs of the crop would be expected to be the same except where method of application changes response to rate of application. Studies have shown that fertilizer applied in a band at planting should be applied 2 to 3 inches to the side and 2 to 3 inches below the seed to promote early growth and prevent salt injury, especially fertilizer containing ammonium phosphate (17,18,25,26)). Studies to compare the efficiencies of broadcast and drill applied fertilizers have shown that phosphorus efficiency on soils low in P is 3 times greater for drill than for broadcast application (25). The difference decreases as P fertility increases. The effect of placements is much less for other elements. Sidedress application of N after plants are up to a stand has been a standard practice. Sidedress application of P would not be expected to be effective in supplying P. Part of the K needs can be met by sidedress application (41), but except on very sandy soils broadcast or drill applications are more effective. Studies were conducted on soil medium or high in P and K, where little or no response to applications of these elements would be expected, to determine if method of application affected yields. Two years results, Table 1, show little or no yield advantage to drill application of P or K over broadcast application. There was no advantage in applying all P and K at planting over applying most of the P and K broadcast and only a starter application of N-P-K at planting time. An early growth response 20 ALABAMA AGRICULTURAL EXPERIMENT STATION Six TABLE 1. EFFECT OF N-P-K PLACEMENT ON YIELD OF SEED COTTON, LOCATIONS IN 1964 AND ANOTHER Six LOCATIONS IN 19651 No. Broadcast N-P-K 0-0-0 0-9-30 0-18-50 0-18-50 0-27-75 0-0-0 0-0-0 90-18-50 At planting dress N-P-K 20-18-50 20-9-20 20-9-20 0-0-0 0-0-0 20-0-50 20-18-0 0-0-0 N 70 70 70 90 90 70 70 0 SideA Yield of treatment 1 and relative yield of all other treatments Locations D B C E F Av. 1. 2. 3. 4. 5. 6. 7. 8. 2,600 100 100 94 101 96 87 872 Pounds per acre 2,359 2,963 2,724 2,736 1,997 2,576 Relative yield pct. 93 102 100 102 100 101 100 98 98 102 95 106 88 100 95 97 96 96 95 96 98 99 99 102 100 96 101 88 103 97 96 99 98 97 96 101 98 96 99 982 1012 103 1All treatments at each location were applied on basis of soil test and soil type. Soil test treatment listed is a typical example for a Coastal Plain soil with a high P, medium K soil test rating. All locations were high in P except one that was medium. Three locations were high in K and three were medium. 2 Second year only. Locations: A-Norfolk fsl, Headland, Ala., Soil Test HM; B-Magnolia, fsl, Monroeville, Ala., Soil Test HH; C-Norfolk, sl, Auburn, Ala., Soil Test HM; D-Greenville, scl, Prattville, Ala., Soil Test HH; E-Decatur, cl, Belle Mina, Ala., Soil Test MM; and F-Hartsells, fsl, Crossville, Ala., Soil Test HH. occurred on sandy soils to a starter application of nitrogen in 1964 when temperature and moisture were favorable. This response was reflected in final yield. Based on this study for soils with a medium or high soil test for P and K, all P and K may be applied broadcast as needed for yield and to build or maintain fertility. The N may be applied broadcast before planting or as a sidedressing early after emergence. Effect of Weather on Response Concern is often expressed that the response data obtained under average weather conditions may not apply for better than average weather conditions. The data in Figure 11 showing the average yield for seven locations indicate that under a normal range of weather conditions this is not a valid concern; the magnitude of yield response varies slightly with weather conditions but the rate of fertilizer from which a response is obtained does not vary. Bray (9,12) explains this as a characteristic of immobile nutrients. In more favorable seasons root ramification is increased so that the soil supplies a proportionally larger amount. That this does not hold once an environmental factor is markedly SOIL TEST THEORY and CALIBRATION 21 SOIL TEST THEORY and CALIBRATION 21 FIG. 11. Effect of yield level on response from N, P, and K in a 3-year period at seven locations. altered is illustrated by the response obtained under irrigation in a later section of this report. Skip-Row Planting All work cited has been with solid planted cotton with stands between 20,000 and 40,000 plants per acre. Data obtained from skip-row planting show that skip-2-plant-2 can result in yields about one-third higher per allotted acre (47) than solid planted cotton. Rates studies with the individual elements have not been made under skip-row conditions. Considering the mobility concepts of nutrients and the basis on which plants absorbed nutrients, there should be no need to change the rate of application of P and K per allotted acre. However, because of higher yield potential, the rate of N should be increased. Irrigation The elimination of soil moisture as a factor limiting plant growth might be expected to change fertilizer requirements. The yields obtained from irrigation experiments (36,45) showed that the yield potential was increased from about 2 bales per acre for solid-planted cotton in Alabama to nearly 4 bales, Figure 12. When the environment is modified sufficiently to result in yield differences of this magnitude, interpretations of soil test must be changed. Above ground portion of plants from irrigated plots contained as much as 400 pounds of K per acre as compared 22 22 ALABAMA AGRICULTURAL EXPERIMENT STATION ALABMA AGRICUILTUA XEIMNTTO N Lb./A. FIG. 12. Cotton response to rates of N with and without irrigation, 3-year aver- age, Thorsby, Alabama (Ref. 26). with 100 pounds per acre in those from unirrigated plots (6). Even though relative yield and soil test calibration data obtained under a wide range of natural climatic conditions can be pooled, a different calibration must be developed when the environment is changed appreciably such as with irrigation. Nitrogen Soil test procedures have not been developed that provide information on soil N available to meet requirements of crops under soil and climatic conditions prevailing in Alabama. All recommendations that are made for N are general and assume the normal range of weather conditions and good management practices conducive to yields of 11/2 to 2 bales per acre. The SOIL TEST THEORY and CALIBRATION 23 SOIL TEST THEORY and CALIBRATION L IL~I I~hUK~ ann LnLiaKniiriN 23 20 N Lb./A. FIG. 13. 8 I0 Response of cotton to applications of N, 1959-1961. yield response obtained in recent cotton experiments is shown in Figure 13 for three different general groups of soils. better adapted varieties are available and better means of reducing boll rot and insects are developed, higher rates of N may be justified. Soil Acidity When Research over the years has shown that soil acidity is im- 24 ALABAMA AGRICULTURAL EXPERIMENT STATION portant in crop production (1). Figure 14 shows the relationship between soil acidity and cotton yield on two Coastal Plain soils (2). In addition to its general effect on yield, soil acidity has an adverse effect on stand under certain weather conditions (40). On some soils cotton is tolerant of a wide range of soil acidity conditions, but, because of the effect of acidity on leaching losses (33) and the availability of plant nutrients soils at a pH of less than 5.8 generally would need to be limed. 5.0 5.2 5.4 5.6 5.8 6.0 6.2 SOIL pH 6.4 6.6 6.8 FIG. 14. Yields of cotton at various soil pH levels, Experiment Fields (Ref. 2). Brewton and Monroeville SOIL TEST THEORY and CALIBRATION 25 Magnesium Studies have shown that magnesium (Mg) deficiency occurs in cotton on certain soils in Alabama. The point of deficiency has not been accurately calibrated, but it appears to be near 5 per cent Mg saturation of cation-exchange capacity of the soil. The typical response pattern for Mg (3) is presented in Table 2. The most economical source of Mg for cotton is dolomitic lime. However, where soil pH is above 6.2, dolomite will not react sufficiently with the soil, and other sources of Mg must be used. TABLE 2. YIELD INCREASE OF SEED COTTON FROM ADDITION OF MAGNESIUM SULFATE AT 4 LOCATIONS, 2-YEAR AVERAGE Location and soil type Exchangeable magnesiumgYield increase p.p.m. Pounds per acre 0 80 280 360 Alexandria Experiment Field, Decatur clay loam Monroeville Experiment Field, Magnolia fine sandy loam Sand Mtn. Substation, Crossville Hartsells fine sandy loam Brewton Experiment Field, Kalmia sandy loam 55 20 14 10 Micronutrients Boron. Boron (B) deficiency occurs in cotton on many soils of the State (52,53). Since analysis for B is expensive and the amount of the element needed per acre is small, the practical solution would be to add one-half pound of B per acre annually. This can be applied in the starter fertilizer, in the preemerge herbicide, or at a rate of one-tenth pound per acre for not more than five applications in the insecticide. Other Elements. Examples of deficiency of Mn, Zn, or Mo have not been observed on cotton in Alabama. Manganese (Mn) toxicity has been observed on very acid soils. The practical solution to this is liming to desirable pH range. SOIL TEST CALIBRATION for CORN Research data for corn are sufficient to provide a dependable recommendations based on soil tests for yields up to 100 bushels per acre. During the past 10 to 12 years, State average corn yields have increased from less than 20 bushels to more than 40 26 ALABAMA AGRICULTURAL EXPERIMENT STATION bushels per acre. Some factors which have been responsible for this were a reduction in total acreage, an increase in use of hybrid seed, closer spacing, and higher rates of N. In 1965 soil samples for corn recommendations were received for less than 10 per cent of the corn acreage planted in the State. Therefore, maximum use was not being made of information that could be provided by soil test. Corn Response to N-P-K Compared with Cotton The response characteristics of corn to N, P, and K as compared with those of cotton at the same test sites are shown in Figure 15. These are the average relative yields of the two crops at seven locations in the State where cotton was grown one year and followed by corn the next. The figure shows that the response characteristics of corn are different than those of cotton; therefore soil test calibration developed for cotton cannot be applied to corn. The response characteristics of the two crops to P are similar. Corn gave greater relative total response to N than cotton particularly at high rates. The greatest difference between the two crops was in response to K. Corn shows little response and to only a small rate of application at soil levels where cotton almost completely failed without the addition of K. 0 30 60 90 120 N Lb./A. 150 P Lb./A. K Lb./A FIG. 15. Comparative response of cotton and corn to N, P, and K, average of seven locations. SOIL TEST THEORY and CALIBRATION SOIL TESTr THuEORY and CALIBATION 27 27 Group I&II Soils Group III Soils P (Pom) FIG. 16. Relationship between soil test P and relative yield of corn. Relationship Between Soil Test P and Relative Yield Using data obtained from sites where yields above 40 bushels per acre were produced, the relationship between soil test P and yield of corn is shown in Figure 16. The points in the figure refer to experiments described in Appendix Table 3. This relationship practically duplicates that shown in text Figure 3 for cotton. This would be expected considering the similarity in response of the two crops to this element. Relationship Between Soil Test K and Relative Yield The relationship between yield and soil test K is shown in Fgure 17. The points in the figure refer to experiments described in Appendix Table 4. Sufficient data were not available to provide a reliable estimate of the minimum K values for corn. However, based on data from other crops, the minimum value was estimated to be 10 ppm K. Using the modified Mitscherlich equation of the form Log (A-y) = Log A-c(b-10), "c" values were calculated. The curve obtained using average "c" value of the unadjusted data is represented by a dotted line. The solid line obtained using the modified equation appears to provide the best estimate of the relationship. Compared with cotton, 28 28 ALABAMA AGRICULTURAL EXPERIMENT ALBAAA IC L STATION - 100 90 - Relative YieIId I j 1713 2 Is 0 5® * i19 C20 _ 80 2826 70 22 ,/ 2 v / - II 60 -' I I- I I - -Log g(A-y)= Group / Soils 9 v/i Group Soils p //l Group Soils 40 I 30 - + Log (A- cb) c =O.041 c = .03/ c= 0.020 -Loy g(A-y) =LogA-c(b-/0)_ p c =0.085 Group/Soils p c =O.064 Group /Soils Groi /i Soils c=0.042 10 i 0 0 0 133 20 75 26.7 40 1 40 60 105 K<(ppm) 53.3 80 66.7 tOO Frlyn Group II Soils GroupIll Soils FIG. 17. Relationship between soil test K and relative yield of corn. the same relative yield of corn could be expected with a soil K level almost one-half of that required for cotton. These data show that 34 ppm K represents a fertility index of 100 and 17 ppm a fertility index of 75. 20 I Response to P and to K at Various Soil Test Levels I__ Responses to rates of application of P and K at certain soil test values are shown in Figues 18 and 19. These data indicate 100 80 70 RELATIVE YIELD MEDIUM 90 LOW Low Med. - 2 locations wi/h fertility index ~75 5 -- locatlions wi/h fertility wi/h index between 75 and /00 -High - 3 /0cc/ions Index /00 fer/ility- 0 30 20 10 RATE, OF P ANNUALLY Response of corn FIG. 18. to lb/A 50 40 (Px2.24= P205) rates of P on soils testing low, medium, or high. SOIL TEST THEORY and CALIBRATION 29 100 RELATIVEI YIELD HI MEDIU LOW 80 70 Low Med. High20 RATE FIG. 19. --- 4 locations with fertility 75 index 3 -locations with fertility index between75 and/00 2 locations with fertility index & /00 40 60 K ANNUALLY Ib/A 80 100 (Kx I.2= K20) OF Response of corn to rates of K on soils testing low, medium, or high. that the efficiency with which corn is able to use soil K is carried over to applied K; however, studies are not available showing response where soil levels of K are too low to support relative yields of more than 15 to 20 per cent. Data from such soils are needed to better characterize the efficiency with which corn can utilize applied K. Fertility Depletion, Maintenance, and Buildup Critical studies showing the value of soil fertility buildup of P and K for corn are not available. Soil buildup and depletion by corn has been found to be similar to cotton. Figures 7 and 8 previously presented showing a summary of buildup and depletion for 7 locations over an 8-year cropping period was with cotton. This study was followed by 3 years cropping to corn. There was no apparent change in rate of buildup or depletion under corn. Effect of Fertility on Factors Other Than Yield Lodging of corn probably affects harvest more than any other one factor. K fertility has been credited with affecting lodging. Studies in Alabama have shown this effect only at very deficient K levels. When K is sufficient for 50 per cent relative yields additional K has not influenced lodging. Nutritional studies with swine have shown corn grown on low-zinc (Zn) soils may not contain sufficient amount of the micronutrient to prevent development of Zn deficiency (49). Other characteristics such as oil content or protein content of 30 ALABAMA AGRICULTURAL EXPERIMENT STATION grain may be modified slightly by fertility, but these are primarily varietial characteristics. Rate of Fertilizer Needed vs. Soil Fertility The relationship between soil test value and rate of fertilizer P and K needed to prevent these elements from limiting yield is illustrated in Figure 20 and 21. The straight line shows actual response. Data are not available to show that corn yields are influenced by soil buildup of P and K. Therefore, only rates to 30 PLb./A.(P X2.25P , IRote 0 5) 2 I for a Soil Fertil/ty Index Less Than 75 20 Rote for a Soil Fertility Index Between 75 And /OO Rote for a Soil Fertility lndexMore Than /oo 0 ___ _ _ __ FIG. 20. Annual rate of P for various soil test values-corn. FIG. 21. Annual rate of K for various soil test values-corn. SOIL TEST THEORY and CALIBRATION 31 which a response can be obtained plus allowance for maintenance can be justified. However, considering that rates data are available only from soils containing sufficient P and K for 60 per cent or more relative yield, the curve is drawn to allow for soil buildup for soil test values below 8 ppm P or 18 ppm K. It is also drawn above the actual yield response line as a safety precaution to allow for some field variation and sampling error. Method of Fertilizer Application Data reported here were obtained in experiments with all P and K together with 20 to 30 pounds of N applied as a band application at or before planting. The remainder of the N was applied as a side application. Other methods of application would be expected to result in similar response patterns provided placement did not damage seedling and the rate of application was adjusted where broadcast applications of P were substituted for drill applications on soils low in P. Studies showing comparative effectiveness of sidedressed K with drill K are not available, but, considering that 90 per cent of the plant's total K needs are required by tasseling (23,24,31), it is reasonable to expect that for a sidedressing of K to be as efficient as drill applications it would have to be applied within 30 days of planting. Broadcast applications of K before planting should be as effective as drill applications. Effect of Weather on Response Yield data from seven locations comparing response when yields were highest with that when yields were lowest in a 3-year period on the same locations, Figure 22, shows that under a normal range of weather conditions the rate of application of P and K to which a response was obtained did not vary appreciably. Although the fertilizer rate to which a yield response would be obtained at any particular soil level might not be changed appreciably by weather differences, the greater crop removal associated with higher yields would need to be offset in the rate of fertilizer applied to maintain fertility. 32 13 ALABAMA AGRICULTURAL EXPERIMENT STATION 120 N L b./A. 1500 10 20 30 P Lb./A. 40 500 20 40 60 80 K Lb./A. 100 FIG. 22. Effect of yield level for a 3-year period on response of corn to N, P, and K, average of seven locations. Irrigation All data referred to concerning yield have been obtained without irrigation. With irrigation to maintain a high level of moisture, yield responses from an additional 50 to 100 pounds N have been obtained. 3 Studies have not been made to determine the phosphorus and potassium requirements for sustained corn yields greater than 100 bushels per acre. However, under irrigation, in view of the added investment in the crop and the limited data, it has been considered practical to increase the normal rate of P and K. Corn Silage The fertilizer required to produce corn for silage is no different than that required to produce corn for gain. The difference is in crop removal, hence soil depletion. With corn for grain the minerals contained in the stover is left on the land whereas when harvested for silage, the entire above ground portion of the plant is removed. Thus, an adjustment should be made in the rate of fertilizer to take into consideration removal. If the soil is already in a good state of fertility, the adjustment can be most efficiently made to the following crop. 3 Unpublished data. SOIL TEST THEORY and CALIBRATION 33 Nitrogen and Spacing Recent studies in Alabama have shown that increasing plant population up to 16,000 plants per acre increases the yield potential with present varieties (44). With stands of 16,000 stalks per acre, N rates of 100 to 150 pounds per acre are required for maximum yields, depending on the yield potential of the field. The interaction between stand and rate of N for two different yield potentials are shown in Figure 23 (44). This shows that N Lb./A. N Lb./A. FIG. 23. Response of corn to N at different plant populations under two yield levels (Ref. 44). yield in the range of 60 to 80 bushels per acre 120 pounds is adequate for top yields even with 12,000 to 16,000 plants per acre; however, where the yield potential is 100 bushels, a response may be obtained to 150 pounds N. Studies are in progress to determine response at higher populations. Soil Acidity Corn is recognized as a crop with a wide tolerance to soil acidity. However, yield is limited on some soils because of acidity when the pH drops below 5.4 (Figure 24)). Data are not available from a sufficient number of experiments to define a critical point. This exact point would be expected to vary with soil because it is governed by soil characteristics that determine the 34 34 ALABAMA AGRICULTURAL EXPERIMENT STATION ALABAMA AGRICULTURAL EXPERIMENT STATION FIG. 24. Relationship of soil pH and yield of corn as compared with yields where acidity was not a limiting factor. amount of aluminum (Al) becoming active. Considering all factors associated with soil acidity, the practical solution is to apply lime as needed to maintain pH in the range of 5.5 to 6.5. Magnesium Magnesium (Mg) deficiency has been observed on corn as the visual deficiency symptom of chlorosis between veins. This deficiency has not been calibrated sufficiently to indicate limiting values. Micronutrients Zinc. Zinc (Zn) defficiency occurs in corn on many of Alabama's sandy soils that have been limed to pH 6.0 and above or soil P is high or both (50,51). Studies are currently underway to calibrate soil level with response and thus to provide a basis SOIL TEST THEORY and CALIBRATION 35 SOIL TEST THEORY and CALIBRAION 3 for recommending Zn based on soil test for Zn. Presently, recommendations for Zn are based on soil texture, pH, and soil test P. When Zn is recommended, 3 pounds per acre per year is sufficient. After 2 or 3 applications of 3 pounds of Zn per acre, the soil level will usually be sufficient to prevent deficiency in corn. Other Elements. Examples of deficiencies of manganese (Mn), boron (B), molybdenum (Mo), or copper (Cu) on corn have not been reported in Alabama. SOIL TEST CALIBRATION for SOYBEANS Compared with the calibration data for cotton and corn, data available on soybeans is limited (5,42); however, the data on soybeans appear to agree with calibration data for cotton and corn. Because of this apparent agreement, greater weight can be assigned than if no comparison could be made. Soybeans is recognized as a crop influenced by soil fertility but where direct application of fertilizer is not a critical production factor. Research results show that many acres of soybeans are being grown below optimum levels of soil fertility or rates of fertilizer application. Very few soil samples are received annually in the Auburn Soil Testing Laboratory for soybeans. This indicates very little consideration is given to direct fertilization of soybeans by most growers. Relationship Between Soil Test P and K, and Relative Yield Response at Various Soil Levels Data available relating soil test P and K needs are shown in Figures 25 and 26, and response to direct application of these elements at various fertility levels in Figures 27 and 28. The points in the figures refer to experiments described in Appendix Tables 5 and 6. These data show that soybeans are similar to corn and cotton in soil fertility requirements and in response to applications of P. The response to K appears to be intermediate between these two crops. 36 ?~ ALABAMA AGRICULTURAL EXPERIMENT Al ARA~~A ArblrlllT STATION 0 10 5 20 10 30 15 P (ppm) 40 20 50 25 60 30 Group And II Soils Group III Soils FIG. 25. Relationship between soil test P and relative yield of soybeans. 10010 i 80, O aionhi O I 70 -- @/IEL ,, Log A-y= LogA-cIA group l Soil C =0.03 6 ISoil C =0024 1/l So)l C r00/8 Log A -y= Log A- c(b-/12) Group / Soil C =0.078 // Soil C= Ill Soil C= 0.036 0054 120 FERTILITY INDEX 30 40 60 80 90 120 K (ppm) 120 160 Ioo 150 200 180 240 Group I Group II Group III Fig. 26. Relationship between soil test K and relative yield of soybeans. SOIL TEST THEORY and CALIBRATION 37 rRELATIVE YIELD I Rating- 80 Low- 0 Locations with fertility index less than 75 Med.- 0 Locotions withfertility index 75 to /00 High-3 Locations w'ith fertiliy indexobove O0 70 00 5 I) 15 P Lb./A. 20 25 30 FIG. 27. high. Response of soybeans to rates of P on soils testing low, medium, or -. K Lb./A. FIG. 28. high. Response of soybeans to rates of K on soils testing low, medium, or Fertility Depletion, Maintenance, and Buildup Based on removal in harvested crops, P buildup and depletion with soybeans should be comparable to that with cotton and corn for grain. Potassium removal is greater by soybeans than by either cotton and corn. Therefore, a higher rate of application may be required for maintenance and buildup. The limited data available indicate about one-tenth pound buildup per pound applied annually over the 4- or 5-year-period as compared with one-fifth pound in cases of cotton and corn. 38 ALABAMA AGRICULTURAL EXPERIMENT STATION Rate of Fertilizer Needed vs. Soil Test Rate response data have not been obtained at a sufficient range in soil levels to define completely the relationship between soil test level and rate at which a response can be obtained. However, the data available indicate that rates of P and K adequate for cotton would be sufficient for soybeans. Method of Application Method of applying fertilizer to soybeans is extremely important, not because of the need for proper placement for response but because of the sensitivity of the seed to salt injury. Obtaining a stand-is of major significance with this crop because extreme sensitivity of germinating soybean seed to even low concentration of soluble salt, fertilizer for soybeans applied at planting must be broadcast or placed 2 or more inches to the side of seed (42). Nitrogen Crop yields in the favorable range of 35 bushels per acre require approximately 200 pound N per acre just to provide that contained in the soybean seed at harvest. Properly inoculated soybeans can fix atmospheric N to meet most of this need. Research has not often shown a yield response to application of nitrogen, either from starter applications or from applications at blooming time when the soil is inoculated from previous soybean crops or when the seed are properly inoculated. It is not unusual to observe a visual response in plant growth to a starter application of N, but as a rule this does not result in increased seed yield. About the only exception is on very sandy soils where soybeans have not grown previously. Even under this condition yield increases of only 2 or 3 bushels have been obtained from application of N. This has led to the belief that a starter application may decrease fixation of atmospheric N. However, no yield response has been obtained from nitrogen applications made at blooming time. (42). 4 Soil Acidity Soybeans like most other N-fixing leguminous crops will not produce top yields at extreme levels of acidity except on soil SAlso more recent unpublished data. SOIL SOIL TEST THEORY TEST THEORY and and CALIBRATIN CALIBRATION 39 *RLAIVFYL~lfl.-. 100 90 so 70 60- @ 50 40 O 4.0 45 5.0 Soil 5.5 pH 6.0 65 7.0 FIG. 29. Relationship between soil pH and relative yield of soybeans. with very low capacity to release Al into the soil solution. Fig. 29 indicates that soybean yields are influenced by acidity below 5.4 but this varies with location. Micronutrients Molybdenum. Molybdenum (Mo) is one of the micronutrients that has been added to the list of essential elements sometimes deficient in soils. For many years it has been known that Mo was required in the process of N fixation by bacteria. Only in recent years has it been shown to be deficient for growth of certain plants on some soils. Response in soybean yields from applications of Mo have been reported in other Southeastern States on very acid soils. Several experiments have been conducted in Alabama to determine the likelihood of a Mo deficiency; to date no response has been obtained. Other Elements. Examples of deficiencies of other elements have not been observed in Alabama with the exception of Mg. Deficiency of this element probably falls in the same category as that with cotton and corn; for this reason consideration is given to use of dolomitic limestone on soils low in Mg when liming is needed. SOIL TEST CALIBRATION for COASTAL BERMUDAGRASS Coastal bermudagrass is one crop in the broad category of summergrass pasture ranging from carpetgrass and crabgrass 40 ALABAMA AGRICULTURAL EXPERIMENT STATION through forage sorghum, millets, sudan and johnsongrass, bahiagrass, and various bermudagrasses. Some data are available on all of these crops, but not enough to provide complete calibration. The data available indicate some variation in calibration depending on rooting characteristics and total removal of harvested plant parts. Because of the interest in livestock production in this State, the fact that this category of crops is supported by A.S.C.C. assistance and perhaps other reasons, the number of soil samples sent to Auburn Soil Testing Laboratory for summergrass pastures is appreciable. There is an estimated 1,500,000 acres devoted to production of summergrass pasture. Samples tested in 1965 averaged one for each 220 acres. The calibration of Coastal bermudagrass will be limited to loamy sand and sandy loam soils of the Coastal Plains where this crop is well adapted and where an intensive study has been made during the past 5 years (29). Relationship Between Soil Test P and K, and Relative Yield Response at Various Soil Levels The relationship between soil P and K in the surface 2 inches and relative yield is presented in Figures 30 and 31. The points 13 0 0 initial O final year year Log (A-cb) c = Log (A-y) Group I Soils 0.054 201 0 I I o0 0 20 30 40 50 60 70U Group I Soils !. -' I- SOIL TEST P(ppm) FIG. 30. Relationship between soil test P in the top 2 inches of soil and relative yield of Coastal bermudagrass. SOIL TEST THEORY and CALIBRATION SOIL TrEST TEORY and CALI~RATIN 41 4 ®IVI O ~II\III o 1 ®___ Ioo r " . -a . . . . 1 . 80 0 ._J r /O 60 0 "ofinal ,0initial O year year w J 40 w 61 J - Log (A-y) = Log(A-cb) Group / Soils c = 0.037 = LogA-c(b-l c = 0.067 /0) 20 1 / / ---- Log (A-y) Group / Soils V 0 10 I 20 · 30 40 50 rI , 60 i i 70 Group i Soils SOIL TEST K(ppm) FIG. 31. Relationship between soil test K in the top 2 inches of soil and relative yield of Coastal bermudagrass. in the figures refer to Appendix Tables 7 and 8. Since Coastal bermudagrass is a deep rooted crop, a question of depth of sample is frequently raised. Studies have been conducted to determine if the calibration could be improved by analyzing other fractions of the surface 24 inches. It was found samples of the surface 2 inches from established stands of Coastal on sandy Coastal Plain soils that had not received unusual treatments in the last few years gave as good an indication of expected response as the 0-6, 0-12 or 0-24 inches of the profile (29). Therefore, from a practical standpoint, calibration for this and all other sod crops is based on the analysis of the surface 2 inches of soil. Such samples cannot be expected to give a valid indication of the available supply of the nutrients in the soil when radical changes in treatment have been recently made. Several experiments have been conducted and others are in progress to determine rate of application needed at various initial soil levels. It appears that when the soil level is in the range where a response can be expected the rate of application will need to approach rate of removal. 42 ALABAMA AGRICULTURAL EXPERIMENT STATION Fertility Depletion, Maintenance, and Buildup No benefit has resulted from applying a sufficiently high rate to maintain the soil at a level of fertility above the point where a response to application is no longer obtained. When the soil level is above this point, it appears that the most profitable practice is to apply less than that removed until the soil level approaches the value where a response will be obtained and then apply amounts required to offset removal. The effect of 4 years treatment and removal of hay with 200 pounds of N is shown in Figures 32 and 33. The intermediate rate was planned to approximate rate of removal. The average data for all locations indicate this was accomplished. The data show that at a ;OIL TESTED P (ppm) ,fremval, FERTILITY INDE: S30( Ls acompish 60 ES -r 40 20 0 i I I P annually II Ib/A \I FIG. 32. Change in soil test P from four annual applications to Coastal bermudagrass. SOIL TEST THEORY and CALIBRATION 43 I TEI ERY n CLIRAN 60 -Soil Tested K (ppm) Fertility Index - 40 S100 S75 20 _ ____ _ __ 75 0 I I 0 64 K ANNUALLY 128 lb/A FIG. 33. Change in soil test K from four annual applications to Coastal bermudagrass. high soil level there was a decrease from a rate equal to removal, but at low soil levels there was an increase; the medium soil level did not change. Effect of Fertility on Factors Other Than Yield Luxury consumption of both P and K occurs when the amount available is in excess of the amount required for maximum growth as is indicated in Figures 34 and 35. The amount of P involved is small and may be beneficial for animal nutrition. The amount of K removal in excess of needs can be appreciable. This study shows that where hay production without irrigation is not more than 5 tons per acre 20 pounds P per acre would more than offset removal, for K about 80 pound per acre would be needed. These data suggest that after a medium or high level of P and K is obtained, the use of N, P, and K in the ratio of 10-1-4 (N, P2 0 5 , K20 in ratio of 4-1-2) should provide adequate amounts of each 44 ALABAMA AGRICULTURAL EXPERIMENT STATION 44 AL ABAMA AGICLTUALEPEIMN SATO 00 90 0 O 016 13 15 80 !70 70 J >60 0 I-50. o Oinitial year final year 40 30 .10 .12 .14 .16 .22 FIG. 34. Relationship between P content of Coastal bermudagrass and relative yield showing luxury consumption above 0.16 per cent P. ILI 00 90 - Q 80 @O 70 60 J -50 ~ final year Q 40 JL 30 20 10 0 0.4 0.6 0.8 % K Oinitial year 1.0 1.2 1.4 1.6 FIG. 35. Relationship between K content of Coastal bermudagrass and relative yield showing luxury consumption above 1.0 per cent K. SOIL TEST THEORY and CALIBRATION 45 element. This has been predicted by several writers. (13,21,28, 29,54). However, the data suggest that this will not hold over a wide range of N rates and will vary with production and utilization of forage. It has been established that a fungus disease attacks Coastal bermudagrass and other grasses when available K is below the amount required for top production at the rate of N and level of moisture available (20). This weakens the stem and root system to such an extent that stands are reduced. These studies have shown that if K levels are kept sufficiently high to maintain yield that the stand reductions does not occur (4,20). Maximum yield can be obtained from K applied as needed. These same studies show that K efficiency is increased by dividing the annual application. Nitrogen Grasses such as Coastal bermuda have production potentials that are limited essentially by the rate of N applied and the amount of available water. Evans et al. (19) reported that under normal climatic conditions of Alabama, except where very high protein levels are desired, N applications in the range of 200 to 400 pounds per acre give the highest return for investment. Higher rates are profitable only where available moisture is high and the forage is utilized to take advantage of high N content. These studies show that yields are limited more by N than by water under Alabama rainfall conditions. However, there are years when moisture definitely limits yield. Soil Acidity Coastal bermuda is very tolerant to soil acidity. A response to lime was not obtained in the studies reported in Figures 30 and 31, although the minimum soil pH was about 5.0. Response to lime has been obtained in other studies where the pH of the total profile approaches 4.5.5 Where the rate of N applied is 200 pounds per acre or more annually, the soil can become very acid throughout the profile. Since it is normally impractical to incorporate lime into the subsoil once it becomes very acid, the question is should not an effort be made to maintain soil pH in a reasonable range to prevent very acid conditions developing in the subsoil. Over a long period subsoil acidity will become a 6 Unpublished ARS-USDA research. 46 ALABAMA AGRICULTURAL EXPERIMENT STATION factor in production of this crop. Consideration might also be given to change of crop that is not as tolerant to acidity. Some of the other summer grass crops in the millet and sorghum families are more sensitive to acidity. Considering these factors, lime is presently recommended for Coastal bermudagrass when soil acidity is below 5.5. Other Elements Examples of deficiency of any of the secondary or minor elements under normal management have not been demonstrated at this time. SUMMARY and CONCLUSIONS A theory of soil test calibration presented here relates chemical soil test values to relative yield and expresses these fertility levels as a "Fertility Index" in which 100 represents the soil value where a yield response to application of the element is no longer obtained. The response to applications of the mineral element is then related to Fertility Index. This information along with other factors considered in arriving at a soil fertility program is presented for cotton, corn, soybeans and Coastal bermudagrass. The research reported here shows that chemical soil test values can be related to crop response in the field and to rate of application of mineral elements needed to prevent limiting yield. ACKNOWLEDGMENTS Much of the credit for information in this bulletin is given the Substation and Experiment Field Superintendents, who supervised the field phase of many of the studies. Especially recognized are J. K. Boseck, C. A. Brogden, W. W. Cotney, S. E. Gissendanner, H. F. Yates, F. E. Bertram, F. T. Glaze, and J. W. Richardson. The N-P-K study with cotton and corn was jointly planned and supervised by J. T. Cope, Jr., L. E. Ensminger, C. E. Scarsbrook, and the author. Most of the corn calibration data was collected by J. I. Wear and Doyle Ashley. The Coastal bermudagrass study reported was conducted by C. E. Evans, C. W. Jordan, G. W. Crowley, J. T. Eason, and the author. SOIL TEST THEORY and CALIBRATION 47 LITERATURE CITED (1) ADAMS, FRED. 1958. Response of Crops to Lime in Alabama. Auburn Univ. (Ala.) Agr. Exp. Sta. Bull. 301. (2) _......... . 1962. Lime and Cotton. Highlights of Agr. Res. 9:No. 4. Auburn Univ. (Ala.) Agr. Exp. Sta. (3) -. 1963. Cotton Grown on Gray, Sandy Soils Needs Magnesium. Highlights of Agr. Res. 10:No. 3. Auburn Univ. (Ala.) Agr. Exp. Sta. ADAMS, W. (4) on Winter Killing of Coastal Bermudagrass. Agron. E. AND MARVIN TWERSKY. 1959. Effect of Soil Fertility J. 52:325-326. Au- (5) AUTHORED BY STAFF. 1967. Research for Soybean Producers. burn Univ. (Ala.) Agr. Exp. Sta. Bull. 3738. (6) (7) BENNETT, O. L. ET AL. 1965. Yield, Fiber Quality and Potassium Content of Irrigated Plants As Affected by Rates of Potassium. Agron. J. 57:296-299. BRAY, ROGER H. 1948. Correlation of Soil Test with Crop Response to Added Fertilizers and with Fertilizer Requirement. Diagnostic Techniques for Soils and Crops. Chapt. II. The Amer. Potash Inst. Washington, D.C. . 1944. Soil-Plant Relations: I. The Quantitative Relation of Exchangeable Potassium to Crop Yields and to Crop Response to Potash Additions. Soil Sci. 58:305-324. 1954. A Nutrient Mobility Concept of Soil Plant (9) Relationships. Soil Sci. 78:9-22. 1959. The Correlation of a Phosphorus Soil Test (10) .... with the Response of Wheat Through a Modified Mitscherlich Equation. Soil Sci. Soc. Amer. Proc. 22:314-317. (11 ) -------------. 1961. You Can Predict Fertilizer Needs with Soil Test. Better Crops 6. ............. Confirmation of the Nutrient Mobility Con1968. (12) cept of Soil Plant Relationships. Soil Sci. 95:124-180. (13) BURTON, G. W. 1954. Coastal Bermudagrass. Ga. Agr. Exp. Sta. Bull. N.S. 2. (14) CLINE, M. G. 1945. Method of Collecting and Preparing Soil Samples. Soil Sci. 59:3-5. (15) ENFIELD, G. H. 1964. Soil Testing Gains Ground - Key DecisionMaking Tool. Plant Food Rev. 10:No. 4. (16) ENSMINGER, L. E. 1960. Residual Value of Phosphates. Auburn Univ. (Ala.) Agr. Exp. Sta. Bull. 322. (17) ENSMINGER, L. E. AND J. T. HooD. 1964. High Analysis vs. Low Analysis Fertilizers. Highlights Agr. Res. 11:No. 4. (18) ENSMINGER, L. E., J. T. HOOD AND G. H. WILLIS. 1965. The Mechanisms of Ammonium Phosphate Injury to Seeds. Soil Sci. Soc. Amer. Proc. 29:320-322. (8) 48 ALABAMA AGRICULTURAL EXPERIMENT STATION (19) EVANS, E. M., R. D. ROUSE, AND R. T. GUDAUSKAS. 1964. Low Soil Potassium Sets up Coastal for Leafspot Diseases. Highlights of Agr. Res. 11:No.2. (20) EVANS, E. M., L. E. ENSMINGER, B. D. Doss AND O. L. BENNETT. 1961. Nitrogen and Moisture Requirements of Coastal Bermuda and Pensacola Bahia. Auburn Univ. (Ala.) Agr. Exp. Sta. Bull. 337. (21) FISHER, F. L. AND A. G. CALDWELL. 1959. The Effect of Continued Use of Heavy Rates of Fertilizer on Forage Production and Quality of Coastal Bermudagrass. Agron. J. 51:99-102. (22) HAMMOND, L. E., W. L. PICKETT AND V. CHEW. 1958. Soil Sampling in Relation to Soil Heterogenity. 552. Soil Sci. Soc. Amer. Proc. 22:548- (23) HANWAY, J. J. ET AL. 1962. North Central Regional Potassium Studies III. Field Studies with Corn. No. Central Reg. Pub. 135. (24) HANWAY, J. J. 1964. The Marvelous Corn Plant. Plant Food Rev. 10:No. 1. (25) HOOD, J. T. AND L. E. ENSMINGER. 1959. Fertilizer Placement Critical for Cotton. Highlights of Agr. Res. 6:No. 1. . 1964. The effect of Ammonium (26) Phosphate and Other Chemicals on The Germination of Cotton and Wheat Seeds. Soil Sci. Soc. Amer. Proc. 28:251-253. (27) JONES, J. B. 1962. Agronomy Abstracts. Amer. Soc. Agron. (28) JACKSON, J. E., N. E. WALKER, AND R. L. CARTER. 1959. Nitrogen, Phosphorus, and Potassium Requirements of Coastal Bermudagrass on a Tifton Loamy Sand. Agron. J. 51:129-181. (29) JORDAN, C. W., C. E. EVANS, AND R. D. ROUSE. 1966. Coastal Ber- mudagrass Response to Applications of P and K as Related to P and K Levels in the Soil. Soil Sci. Soc. Amer. Proc. 30:477-480. (30) KEOGH, J. L. 1963. Soil Sampling Study. Agron. Dept. Mimeo. Univ. of Arkansas. (31) LUTZ, J. A., H. M. CAMPER, G. E. JONES, AND M. T. CARTER. 1963. Fertilizer Placement Effects on Stand, Growth, Maturity, and Yield of Corn. Va. Agr. Exp. Sta. Bull. 549. (32) MORGAN, M. F. 1941. Chemical Soil Diagnosis by The Universal Soil Testing System. Conn. Agr. Sta. Bull. 450. (33) NOLAN, C. N. AND W. L. PRITCHETT. 1960. Certain Factors Affecting the Leaching of Potassium from Sandy Soils. Soil and Crop Sci. Soc. of Fla. Proc. 20:139-145. (34) PAGE, N. R. ET AL. 1965. Procedures Used by State Soil Testing Laboratories in the Southern Region of the United States. So. Coop. Series Bull. 102. (35) PEARSON, R. W. 1952. Potassium-Supplying Power of Eight Alabama Soils. Soil Sci. 74:301-309. . 1963. Moisture and Nitrogen Relations of Cotton, (36) Plant Food Rev. 9:8-11. SOIL TEST THEORY and CALIBRATION 49 (37) REED, J. F. AND J. A. RIGNEY. 1947. Soil Sampling from Fields of Uniform and Non-Uniform Appearance and Soil Types. J. Amer. Soc. Agron. 39:26-40. (38) ROUSE, R. D. 1956. Maintaining Enough Soil Potassium Important. Highlights of Agr. Res. 3:No. 1. 1958. The Potassium Status of Hartsells Fine Sandy (39) -. Loam as Affected by Potassium Fertilization. Soil Sci. Soc. Amer. Proc. 22:334-336. (40) RousE, R. D. AND FRED ADAMS. 1958. Lime for Good Stand and Yield of Cotton. Highlights of Agr. Res. 5:No. 4. (41) RousE, R. D. 1960. Potassium Requirements of Crops on Alabama Soils. Auburn Univ. (Ala.) Agr. Exp. Sta. Bull. 324. .---------------------1961. Soybeans for Oil in Alabama. Auburn Univ. (42) (Ala.) Agr. Exp. Sta. Cir. 138. (43) SCARSBROOK, C. W., O. L. BENNETT, AND R. W. PEARSON. 1959. The Interaction of Nitrogen and Moisture on Cotton Yields and Other Characteristics. Agron. J. 51:718-721. (44) SCARSBROOK, C. E. AND J. T. COPE, JR. 1966. (45) SCARSBROOK, C. E. ET AL. 1961. Spacing and Rates of Nitrogen for Corn. Auburn Univ. (Ala.) Agr. Exp. Sta. Cir. 152. Management of Irrigated Cotton. Auburn Univ. (Ala.) Agr. Exp. Sta. Bull. 332. (46) SOWELL, W. F. 1965. Soil Testing on the Farm. Auburn Univ. (Ala.) Ext. Ser. Cir. P-9A. (47) STURKIE, D. G. AND J. K. BOSECK. 1962. Skip Row Cotton Produces Highest Yields. Highlights of Agr. Res. 9:No. 4. (48) TISDALE, H. B. AND J. B. DICK. 1939. The Development of Wilt in a Wilt-Resistant and In A Wilt-Susceptable Variety of Cotton as Affected by N-P-K Rates in Fertilizer. Soil Sci. Soc. Amer. Proc. 4:333-334. (49) (50) TUCKER, H. F. AND W. D. SALMON. 1955. Parakeratosis or Zinc (51) (52) (53) Deficiency Disease in the Pig. Soc. Exp. Biol. Med. 88:618. VOLK, N. J. 1942. Relationship of Exchangeable Potassium in Alabama Soils to Needs of the Cotton Crop. J. Amer. Soc. Agron. 84:188198. WEAR, J. I. 1959. Zinc Deficiency a Common Disorder of Corn. Highlights of Agr. Res. 6:No. 4. Minor Elements for Plants in Alabama Soils. .1963. Highlights of Agr. Res. 10:No. 2. 1964. Boron for Cotton Profitable in Alabama. Highlights of Agr. Res. 11:No. 4. -------------. (54) WOODHOUSE, W. W., JR. 1959. Fertilizing Coastal Bermudagrass and Sericea for Optimum Production. N.C. Dept. of Soils Information Series No. 2. (55) YOUNG, V. H. AND W. H. THARP. 1941. Relation of Fertilizer Balance to Potash Hunger and the Fusarium Wilt of Cotton. Ark. Agr. Exp. Sta. Bull. 410. O r I -. / / . -1 0 -I 0 / I ___ / .1 / /1, 3; I Cotton Corn O I i I I -- I "U a z Z m z v X I N Lb./A. P Lb/A. K Lb./A. APPENDIX FIG. 1. N-P-K experiment at Brewton Experiment Field; Cotton Index, Location 1, App. Table 1; Corn Index, Location 27, App. Table 3; soil, Kalmia sandy loam, limed 1954. Average from highest yielding treatments: seed cotton (8 yr.) 1,874 lb.; corn (3 yr.) 70 bu. U' X ,, I // ' ,//-- N / / V- -Cotton 0 Corn a r a a -I C Ia I- x m m 40 60 60 90 N Lb./A. z -4 P Lb./A. K Lb/A. -I -I APPENDIX FIG. 2. N-P-K experiment at Monroeville Experiment Field; Cotton Index, Location 2, App. Table 1; Corn Index, Location 28, App. Table 3; soil, Magnolia sandy loam, limed 1954. Average from highest yielding treatments: seed cotton (8 yr.) 1,675 lb.; corn (3 yr.) 47 bu. z I IEI I --C I 0 m m 0 a ____Corn w Cotton 0 Corn 0 20 40 60 80 000 150 9 8 P 27 36450 17 34 K Lb/A_ 51 68 85 30 60 Nihb/A. 90 120 Lb/A. APPENDIX FIG. 3. N-P-K experiment at Prattville Experiment Field; Cotton Index, Location 3, App. Table 1; Corn Index, Location 24, App. Table 3; soil, Greenville sandy clay loam, limed 1954, 1962. Average from highest yielding treatments: seed cotton (8 yr.) 1,806 lb., corn (3 yr.) 43 bu. oe ~ / -- --Cotton ____Corn C m Cotton0 Corn 0 20 30 40 60 60 90 80 120 150 000 9 18 27 36 450 17 34 51 6885 z APPENDIX FIG. 4. N-P-K experiment at Wiregrass Substation; Cotton Index, Location 4, App. Table 1; Corn Index, Location 23, App. Table 3; soil, Norfolk sandy loam, limed 1954. Average corn (3 yr.) 88 bu. from highest yielding treatments, seed cotton (8 yr.) 1,947 lb; RELATIVE .00- YIELD 0 m 80 -I 60 40 -_ 0 o a r m a20 -_ Coltton Corn 3 A Ol O Z 0 z Cotton O Corn 20 30 40 60 60 90 N Lb./A. 5. N-P-K 80 120 100 0 150 9 18 27 36 45 0 17 34 51 68 85 P Lb./A. experiment at Upper Coastal Plain K Lb./A. Substation; Cotton Index, Location 5, App. U' APPENDIX FIG. Table 1; Corn Index, Location 29, App. Table 3; soil, Savannah silt loam, limed 1964. Average from highest yielding treatments: seed cotton (8 yr.) 1,559 Ib.; corn (3 yr.) 82 bu. U' U 0% YI / /I / 'II_ I- w C c 0 IC in m m x Cotton 0 Corn 0 20 30 40 60 60 90 N Lb./A. 80 120 100 0 150 9 18 27 36 45 0 17 34 51 68 85 m z P Lb./A. K Lb./A. O APPENDIX FIG. 6. N-P-K experiment at Sand Mountain Substation; Cotton Index, Location 6, App. Table 1; Corn Index, Location 26, App. Table 3; soil, Hartsells fine sandy loam, limed 1954, 1963. Average from highest yielding treatments: seed cotton (8 yr.) 2,056 lb.; corn (3 yr.) 114 bu. o z rRELATIVE YIELD . . --- - . . t . I O 0 I- -I m -I O 40 a 20 70 rw 05 651 m O Z Cotton 0 Corn 0 20 30 40 60 60 90 N Lb./A. 80 120 100 0 150 9 18 27 36 45 0 17 34 51 68 85 P Lb./A. K Lb./A. APPENDIX FIG. 7. N-P-K experiment at Tennessee Valley Substation; Cotton Index, Location 7, App. Table 1; Corn Index, Location 25, App. Table 3; soil, Decatur silty clay loam, limed 1954, 1962. Average from highest yielding treatments: seed cotton (8 yr.) 1,677 lb.; corn (3 yr.) 64 bu. U' U' APPENDIX TABLE 1. INDEX OF P CALIBRATION DATA FOR COTTON' Seed cotton yield/acre Location Soil type p2 Relative No Ctoile- P Maximum P Lb. gory I Rt No. 6 Vl ppm. 1 2 3 4 5 6 7 8a 8b 8c 8d 8e 9 10 11 12 13 Brewton '60 Monroeville '60 Prattville '60 Wiregrass '60 Upper Coastal Plain '60 Sand Mt. '60 Tenn. Valley '60-------Sand M t. '57----------. Sand Mt. '57----------. Sand Mt. '57----------. Sand Mt. '57----------. Sand Mt. '57----------. Monroeville '64--------Tenn. Valley '64-------Prattville '64-----------W iregrass '64----------Main Station '64-------AVERAGE --------------- Pct. 88 Lb. 1, 656 Kalmia Magnolia Greenville Norfolk Savannah Hartsells sl sl scl sl tl 9 Decatur Hartsells Hartsells fsl fsl 14 46 39 29 8 4 84 100 92 95 68 85 1,426 1,806 1,784 1,478 1,396 1,435 1,1874 .1024 1,675 1,753 1,947 1,559 2,056 tcl f sl fsl Hartsells Hartsells fsl Hartsells f sl Magnolia Decatur Greenville Norfolk Norfolk sl cl sci sl sl 3 8 16 28 43 35 20 62 67 47 57 84 92 100 99 100 1,062 1,850 II 2 .1322 1,555 1,850 II 2 .0396 1,710 1,850 II 2 .1212 1,850 1,850 II 2 .0702 1,845 1,850 II 2 .0460 1,992 1,894 I 2 .0572 77 2,168 2,830 III 2 .0160 100 2,549 2,513 II 2 .0322 92 2,561 2,784 I 2 .0164 100 3,050 3,030 I 2 .0426 ---- -- ---- -- -- -- -- -- -- -- 06 ---------- --- -- -- -- --- -- -- -- .- 2 ----- - - - -- 1,677 I II I II II III 6 6 6 6 6 6 .0548 .0480 .0506 .0690 .0618 .1030 >tI. I- 0 r 1r IC C 1r m x M 1Summary of experimental data on file in Soil Testing Laboratory. Detailed data in Annual Report, Agronomy and Soils Department, Auburn University Agricultural Experiment Station. 2 Extraction 1 + 4 with 0.05 N HCl + 0.025 N H 50 4 not corrected for soil category. 2 3 Coastal Plain equivalent. m z OI ZI APPENDIX TABLE 2. INDEX OF K CALIBBATION DATA FOR COTTON' Location Soil type Sol SoilCae K2 Yield seed cotton tive 32 27 84 53 90 67 91 28 50 74 100 17 37 82 20 38 65 76 65 55 52 77 100 93 96 86 100 No Cae Relatv Pct. K mum K Lb. Maxiu gory I II II 1 II II III II II II II I II II I I I I III I III III I III II I I Rates Value .0098 .0125 Value' .0825 .0186 0 P-I r m H 12 1 2 3 4 5 6 7 8a 8b 8c 8d 9 10a 10b 11 12a 12b 12c 13 14 15 16 Brewton'60. Monroeville '60 Prattville '60 Wiregrass '60 Upper C. Plain '60 Sand Mt. '60 Tenn. Valley '60 Sand Mt. '57 Sand Mt. '57 Sand Mt. '57 Sand Mt. '57 Auburn (6.2) '57 Sand Mt. '57 Sand Mt. Auburn (7.0) '57 Brewton '59 Brewton '59 _______ Brewton '59_______. Tenn. Valley '49 Tborsby (Irrigated) Tenn. Valley '50---Tenn. Valley '51---- Kalmia Magnolia Greenville Norfolk Savannah Hlstun Decatur Hartsells Hartsells Hartsells Hartsells 17 19 21 Monroeville '64.____ Tenn. Valley '64 18 20 Prattville '64_______ Wiregrass '64 Main Station '64 --- ------- Norfolk Hartsells Hartsells Chesterfield Kalmia Kalmia Kalmia Decatur Orangeburg Decatur Decatur Magnolia Decatur Greenville Norfolk Norfolk sl sl si sl tl fsl tcl fsl fsl fsl fsl sl f sl fsl sl sl sl sl tl sl tcl tcl sl cl scl sl sl p.p.m. 17 11 84 34 69 42 72 23 29 41 66 8 24 41 17 20 33 53 61 27 61 71 72 120 132 42 27 Lb. 608 458 1,456 1,072 1,404 1,413 1,531 510 915 1,346 1,816 370 484 1,265 333 542 934 1,151 1,380 2,657 757 1,411 1,892 2,646 2,411 2,387 3,188 1,874 1,675 1,742 2,030 1,562 2,096 1,681 1,816 1,816 1,816 1,816 2,126 1,303 1,536 1,679 1,438 1,437 1,523 2,135 4,866 1,460 1,827 1,894 2,830 2,513 2,784 3,030 No. 7 7 7 7 .0090 m 7 7 7 2 2 2 2 .0096 .0194 .0196 .0290 .0082 .0136 .0196 .0404 .0096 .0174 .0306 .0328 .0446 .0328 .0501 .0418 .0345 .0753 0 Q a n 4 4 5 ---0 5 5 5 5 5 7 4 2 3 3 3 3 3 AVERAGE __________ .0240 .0056 .0102 .0136 .0116 .0148 .0126 .0104 .0177 .0277 .0194 .0160 .0204 .0074 ________ .016 .0108 .0432 .0484 .0415 .0253 .0163 .0254 .0289 .0178 .0276 .0351 .0244 .0188 .0316 .1670 .041 z 'Summary of experimental data on file in Soil Testing Laboratory. Detailed data in Annual Report, Agronomy and Soils Department, Auburn University Agricultural Experiment Station. Extraction 1 + 4 with 0.05 N HCi-- 0.025 N H 50 4 not corrected for soil category. 2 ' Coastal Plain equivalents. 2 Coastal Plain equivalents (b-15). APPENDIX TABLE 3. INDEX OF P CALIBRATION DATA FOR CORN' Location Soil type soil p 2 Relative iI.ct. Corn yield/acre No P mum P Bu. Maxi- Cate- gory I I II II Rates No. 3 3 4 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 «C" value 3 0% 0 pp. 1 2 3 4 5 6 7 Brewton '59 Wiregrass '59 Gulfcoast '57 Gulfcoast '59 Gulfcoast '59 Gulfcoast '59 Gulfcoast '59 Bu. Kalmia Norfolk 8 9 10, 10a 11 12 Coop. '56 Coop. '56 Coop. '56 Coop. '56 Coop. '55 Coop. '56 Marlboro Marlboro Marlboro Marlboro Marlboro Kalmia Norfolk Appling Ruston Kalmia Norfolk sl sl fsl fsl fsl fsl fsl sl sl sl 40 42 11 11 93 100 86 77 79.4 70.4 56.0 60.5 85.0 70.8 65.0 78.2 .029 .048 .078 16 19 29 48 43 62 35 84 89 99 95 87 105 94 97 100 70 102 87 65.4 69.8 77.1 58.8 51.0 68.0 105.8 61.0 77.4 51.3 65.8 50.3 78.2 78.2 78.2 63.6 63.8 64.8 112.0 62.9 88.9 72.8 64.6 57.7 II II II I I II I .080 .050 .050 .068 .026 .020 .032 sl sl sl sl fsl 13 14 15 16 17 Coop. Coop. Coop. Coop. '55 '55 '55 '56 Greenville Kalmia Norfolk Norfolk 43 19 16 17 28 I I I I I .024 .028 .078 .122 fsl sl sl fsl .030 .072 Coop. '56--------- Kalmia Hartsells Hartsells Hartsells Hartsells Hartsells Norfolk Greenville Decatur Hartsells 18 19 Sand Mt. '59-----Sand Mt. '59------ fsl fsl fsl fsl sl scl cl fsl sl sl 20 21 Sand Mt. '59----Sand Mt. '59-----_ 11 15 8 17 26 34 82 91 66 89 93 94 61.0 85.1 56.8 76.4 79.8 81.1 74.1 99.7 85.9 85.9 85.9 85.9 I I II II II II .068 .072 22 23 24 25 26 27 28 Sand Mt. 57-----Wiregrass '64----Prattville '64.----Tenn. Valley '64._-Sand Mt. '64----Brewton '64------Monroeville '64-- 8 19 90 100 65.0 88.0 72.0 86.0 II I 29 19 Upper C. --Plain '6459.___________________ Kalmia Magnolia Savannah tl 52 5 5 10 14 27 17 100 92 56 87 100 96 & 43.0 59.0 64.0 61.0 50.0 80.0 38.0 64.0 114.0 70.0 47.0 82.0 II III II I I II .058 .056 .044 .036 .080 .106 .038 I m m 3 3 4 3 2 3 .100 .071 .088 AVERAGE---------SadMt Hrs1~_fl .150 .052 .062 z ' Summary of experimental data on file in Soil Testing Laboratory. Detailed data in Annual Report, Agronomy and Soils Department, Auburn University Agricultural Experiment Station. 'Extraction 1 + 4 with 0.05 N HCl + 0.025 N H20 4 not corrected for soil category. z Location r-rv~urivrl 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 22 23 24 25 Soil type I Kalmia Norfolk Marlboro Marlboro Marlboro Marlboro Marlboro Kalmia Norfolk Appling Kalmia Norfolk Greenville Kalmia Norfolk Norfolk Kalmia Hartsells Hartsells Hartsells Ruston Hartsells Norfolk Greenville Decatur Hartsells Kalmia Magnolia Savannah Norfolk sl sl fsl fsl fsl fsl f sl sl sl si Soil K2 19 42 25 25 ppm 31 38 53 47 53 90 22 12 38 24 24 19 35 24 43 86 44 24 39 87 64 24 26 15 53 8 Brewton '59 Wiregrass '59 Culfcoast '57 Gulfcoast '59 Gulfcoast '59 Gulfcoast '59 Gulfcoast '59 Coop. '56 Coop. '56 Coop. '56 Coop. '55 Coop. '56 Coop. '55 Coop. '55 Coop. '55 Coop. '56 Coop.'56Sand Mt. '59 Sand Mt. '59 Sand Mt. '57-----. Wiregrass '64.----Prattville '64 -_--Tenn. Valley Brewton '64 si sl sl sl sl si si 26 27 28 29 30 '64--- Sand Mt. '64_------ ------ Monroeville '64--.- ITpper C. Plain '64_ Auburn '58.------AVERAGE----------- fsl fsl fsl si fsl sl 's1 ci fsl si sl tl si Corn Relative ~YI Pct. 58 100 88 86 90 89 94 100 100 90 84 64 100 83 96 93 100 87 97 100 87 93 94 90 96 78 84 76 100 10 yield /acre No MaxiK mum K Bu. Bu. 49.1 85.0 70.0 60.5 57.0 65.0 67.6 78.2 70.2 78.2 69.6 78.2 73.4 78.2 63.6 62.0 63.8 58.9 58.6 64.8 94.1 112.0 40.0 62.9 88.9 77.3 60.2 72.8 62.2 64.6 69.0 74.1 99.7 93.4 75.1 85.9 83.0 85.9 85.6 85.9 50.4 57.7 67.0 72.0 80.0 86.0 34.0 38.0 62.0 64.0 89.0 114.0 57.0 70.0 35.0 47.0 84.0 82.0 7.0 68.0 Category Rates No. 3 3 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 4 1 1 1 1 3 4 3 4 4 5 3 4 Value 3 Value4 0 -I 1 I II II II II I II II I I I I I II II II 53I II II I II II II II I II II .020 .048 .058 .053 .050 .038 .035 .042 .036 .018 .038 .038 .052 .032 .060 .060 .056 .055 .053 .035 .020 .072 .032 .017 .044 .041 .030 .042 .050 .006 .041 .041 .062 .153 .143 .100 .064 .049 .054 .047 .020 .066 .222 .071 .055 .100 .128 .080 .147 .083 .043 .026 .092 .042 .204 .063 .110 .050 .124 .067 .046 .085 m 0 a a 0 z of experimental data on file in Soil Testing Laboratory. Detailed data in Annual Report, Agronomy and Soils Department, Auburn University Agricultural Experiment Station. 2Extraction 1 + 4 with 0.05 N HCl + 0.025 N 50 not corrected for soil category. 3Coastal Plain equivalents. 1Summary 'Coastal H 2 4 Plain equivalents (b-10). f0N APPENDIX TABLE 5. INDEX OF P CALIBRATION DATA FOR SOYBEANS' Location Soil type p2 i Sol Relative Pct. Soybean yield/acre~ No P MaxiBu. ae ae goryeValue mum P p.p.m. 1 2 8 Brewton____ Gulf coast---C. N. CookC. N. Bu. No. I II II II III II 4 4 2 2 2 2 2 4 .026 .035 .200.254 .058 .095 .081 .080 --------.097 U- wo Kalmia Marlboro Colbert Lindside Hollywood Robertsville Talbott Marlboro is fsl tl tl clay tl cl fsl 44 57 5 6 5 21 11 50 98 100 90 97 74 100 25 34 17 27 18 18 27 84 19 28 25 17 5 6 4 7 McCarva____ Clements---Gulf AVERAGE Cook- Whitcher____ 8 coast---. ---- 100 97 20 87 18 88 II II G) M F- 1 Summary of experimental data on file in Soil Testing Laboratory. Detailed data in Annual Report, Agronomy and Soils Department, Auburn University Agricultural Experiment Station. 2 Extraction 1 + 4 with 0.05 N HCl + 0.025 N H 50 4, not corrected for soil category. 2 SCoastal Plain equivalent. x m z -"1 0 z F00 aIAPPENDIX TABLE 6. INDEX OF K CALIBRATION DATA FOR SOYBEANSI-I m m 0 Location Soil type Soil K° Soybean yield! acre Relative Pct. No K Ru. 17 33 Maximum K Ru. 27 34 Categojy Rates No. "C" Value' "C" Value' Q c- p.pm. 1 2 3 4 Brewton____ Gulfcoast--C. N. Cook. C. N. Kalmia Marlboro 5 Cook- McCarva 6 7 8 Whitcher___ Clements ___ L. K. Colbert Lindside Hollywood Robertsxille Talbott fsl tl tl c tc ls 17 58 63 97 I II 9 Bins-- Gulfcoast--AVERAGE ___ Lakeland Marlboro cl ls 22 34 37 44 40 71 80 89 80 100 13 22 22 14 20 19 28 25 17 20 II II II II II fsl 9 63 47 100 14 38 30 38 I II 3 3 2 2 2 2 2 4 4 .025 .035 .032 .028 .035 .021 .067 .031 .048 036 ---------. .086 .056 .. 179 .063 .073 .041 .133 --.067 .078 n -I 0 Z 1 Summary of experimental data on file in Soil Testing Laboratory. Detailed data in Annual Report, Agronomy and Soils Department. Auburn University Agricultural Experiment Station. Extraction 1 4 with 0.05 N HCI + 0.025 N H 50 4 not corrected for soil category. 2 3 Coastal Plain equivalents. 4Coastal Plain equivalents (b-12). + 0a Wl S0% APPENDIX TABLE 7. INDEX OF P CALIBRATION DATA FOR COASTAL BERMUDAGRASS' Location Soil type Soil P2ReaieN Pct. Yield /acre Maximum Tons Relaive o P Tons p.pm. 1 2 3 4 5 6 7 8 Auburn '60 3 Initial 4 5 6 7 8 9 10 p Category Rates No. 3 3 3 3 3 3 3 2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 «c" Value 3 .016 .035 .036 .034 .087 .111 .020 .022 9 10 11 12 13 14 15 Auburn '61 11 12 ----- -13 ------14 ------15 ----- -16 ------17 ------18 17 18 16 ----- Auburn '63 3 Final-. 19 20 21 22 23 4 -----5 .----6 ----7----8-----9------ - Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk sl sl sl sl sl sl sl sl si sl sl sl sl sl sl sl sl sl sl sl sl sl sl 67 57 34 25 3 18 86 89 43 26 46 1 17 15 40 34 33 21 9 7 2 16 30 92 99 94 86 45 100 98 100 100 85 100 95 92 99 86 100 94 94 82 65 38 76 100 6.2 6.8 6.8 5.6 3.0 6.6 7.3 8.6 6.2 3.1 7.0 7.5 5.9 6.0 4.5 4.7 3.4 3.5 3.6 2.3 1.9 3.4 5.1 6.8 6.9 7.2 6.5 6.6 6.6 7.5 8.6 6.2 3.6 7.0 7.9 6.4 6.1 5.3 4.7 3.6 3.7 4.4 3.5 5.0 4.5 5.1 I I I I I I I I I I I I I I I I I I I I I I I a- r a .047 a .032 .044 C I- .065 .133 .021 .059 .037 .058 .083 .065 .104 .039, .067 (Continued) I z IN 0 -4 m m APPENDIX TABLE 7. (Gont'd.) INDEX OF P CALIBRATION DATA FOR COASTAL BERMUDAGRASS' 0 Value 3 0 Location Soil type Soil Yield/acre"C Reatv2N Maxi- Category Rates p.p.m. 24 25 26 27 28 29 Pct. 100 98 97 91 89 85 Auburn '64 10.------------------------------11.------------------------------12.------------------------------13 .------------------------------14---------------15---------------- Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk si si si si si si 66 33 26 40 17 13 Tons 5.3 4.6 4.8 4.7 5.6 4.6 Tons 5.3 4.7 5.0 5.2 6.3 5.4 No. I I I I I I 3 3 3 3 3 3 .033 .053 .059 .026 .056 .063 0 z 30 31 32 1 16---------------17---------------18 .--------------A VERAGE ------------- Norfolk Norfolk Norfolk si si sl 11 40 43 93 94 100 4.2 4.0 5.6 4.5 4.3 5.6 I I I ----------------- 3 3 3 .105 .036 .047 .054 Summary of experimental data on file in Soil Testing Laboratory. Detailed data in Annual Report, Agronomy and Soils Department, Auburn University Agricultural Experiment Station. 2 Extraction 1 ± 4 with 0.05 N HCl + 0.025 N H 50 4 not corrected for soil category. 2 , 3Coastal Plain equivalents. 1U' 0% APPENDIX TABLE 8. INDEX OF, K CALIBRATION DATA FOR COASTAL BERMUDAGRASS' Location Soil type Soil K2 ppm. 36 36 33 36 46 17 44 86 59 32 61 19 42 41 50 46 19 14 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Auburn '60 Auburn '61 Auburn '63 3 Initial 4 5 6 7 8 9. 10 11 12-------13 ----- -14 ------15 ------16 ----- -17 ----- -18 ----- -3 Final-4 ------ 5 ------6 ------ 7------ 8 ------ 9------ - Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk si si sl si si sl sl sl sl sl sl sl si sl sl sl sl sl sl si sl sl sl Relative Pct. 90 100 95 95 100 81 100 100 92 97 97 94 100 95 100 100 90 81 45 6 Yield/acre No MaxiK mum K Tons Tons 6.7 6.0 6.9 6.9 6.8 7.2 6.0 6.3 5.7 5.7 5.2 6.4 7.5 7.5 8.6 8.6 6.2 5.7 3.5 3.6 7.0 6.8 7.7 7.2 6.4 6.4 5.8 6.1 5.3 5.3 4.7 4.8 3.3 3.7 3.0 3.7 2.0 4.8 0.2 3.4 gory No. Value 3 Value 4 I I I I 3 3 3 3 .028 .056 .039 .017 .039 .077 .057 .056 I 3 .044 I I I I I I I I I I I I I I I 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 .042 .046 .023 .058 .048 .025 .064 .048 .032 .040 .044 .053 .052 .012 .003 .103 .059 .026 .122 .069 .030 .122 .063 .042 .050, .056 .111 .180 .065 .029 C 28 14 10 70 3.5 5.0 I 3 .028 ---M z -I m 24 73 91 2.8 4.7 4.0 5.2 I I 3 3 .041 .142 .043 .075 (Continued) -O 0 F- -I -I m -I APPENDIX TABLE 8. (Comt'd.) INDEX OF K CALIBRATIONS FOR COASTAL BERMTJDAGRASS' m 0 Yied/cr /Cate- Rates "C" "C" Location Soil type r irr.r. RelaNo Maxitive r Iiuiin.r Iin I\ ~.ui.i~~-\uiiiiiu Kniirr mum K Soil K2 gory Rae No. 3 3 3 3 3 3 3 3 3 Value 3 Value 4 - 24 25 26 Auburn '64 1011_ 121314. 15. 1617. 18_ pp.m. Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk Norfolk sl sl sl sl sl sl sl sl sl 41 33 44 44 14 14 14 32 41 Pct. Tons Tons G 27 28 29 30 31 32 98 80 100 90 18 73 74 85 100 5.2 3.8 5.0 4.8 1.1 3.9 3.3 3.7 5.5 5.3 4.7 5.0 5.3 6.3 5.4 4.5 4.3 5.5 AVERAGE________ .041 .021 .045 .022 .006 .041 .042 .026 .039 _______ .037 .055 .030 .059 .029 .021 .142 .146 .037 .065 .067 0 z 1Summary of experimental data on file in Soil Testing Laboratory. Detailed data in Annual Report, Agromony and Soils Department, Auburn University Agricultural Experiment Station. ' Extraction 1 + 4 with 0.05 N HCl -1 0.025 N H20 4 not corrected for soil category. , Coastal Plain equivalents. 4Coastal Plain equivalents (b-10). 0%V