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NITIROGEN and MOISTURE
of COASTAL BERMUDA and PENSACOLA BAIHIA
BULLETIN 337 DECEMBER 1961

AGRICULTURAL EXPERIMENT STATION

AU BU RN
E. V. Smith, Director

UNI V ER SIT Y
Auburn, Alabama

CONTENTS
Page
RESULTS OF EXPERIMENTS ------------------4

Greenville Fine Sandy Loam, Thorsby-4 Sumter Clay, Marion Junction-Cecil Sandy Loam, Auburn-----Dewey Silty Clay Loam, Belle Mina-11 Humphreys Silt Loam, Belle Mina-11 Norfolk Sandy Loam, Headland-D Isc Uss Io N -- - - - -- - - - -- - - - -- - - - --

----10

10

13
-14

Irrig atio n - - - - - - - - - - - - - - - -- - - - -- - - - - - - - - - - - - - - - - - - - 1 4 N itrog e n-- - - - - - - - - - - - - - - -- - - - -- - - - - - - - - - - - - - - - - - - - 1 5 Effect of Nitrogen on Soil Acidity, Phosphorus, and Potassium ---------------------- 15
SU M M AR Y -- - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

17

LITERATURE CITED ------------------------------------

18

ACKNOW LEDGMENT------------------------------------19

FIRST

PRINTING

5M,

DECEMBER

1961

Nitrogen and Moisture Requirements of Coastal Bermuda and Pensacola Bahia
E. M. EVANS', L. E. ENSMINGER', B. D. DOSS', and O. L. BENNETT'

Pensacola Bahiagrass (Paspalum notatum Flugge) are popular forage crops. Wide acceptance of these grasses has come about because of their potential for high production. Present acreage of Coastal Bermuda in Alabama is approximately 150,000 while that of Bahia is more than 300,000. Expansion in Coastal Bermuda acreage has been slowed because the grass must be established by sprigging. Most of the increase of Coastal Bermuda acreage in Alabama has occurred since 1955. The southern part of the State had a considerable acreage of Bahiagrass as early as 1950. Several workers have shown Coastal Bermuda to be highly responsive to applied nitrogen (1,2,3,5). Removal of large tonnages of herbage produced by Coastal should increase the mineral requirements beyond the amounts previously considered adequate for forage crops. Summarized in this bulletin are results of field tests and grazing trials conducted in Alabama showing the response of Coastal Bermuda and Bahia grasses to nitrogen and irrigation on specific soil types. Also covered are some of the fertility problems associated with high production. Some of the experiments reported were cooperative between Auburn University Agricultural Experiment Station and the Soil and Water Conservation Research Division, USDA Agricultural Research Service.
SAssociate Agronomist and Soil Chemist, respectively, Auburn University Agricultural Experiment Station. 2 Soil Scientists, Agricultural Research Service, U.S. Department of Agriculture, Thorsby, Alabama.

C

OASTAL BERMUDAGRASS (Cynodon dactylon (L.)

Pers.) and

4

ALABAMA AGRICULTURAL EXPERIMENT STATION

RESULTS of EXPERIMENTS
Greenville Fine Sandy Loam, Thorsby

An experiment was begun in 1956 to determine the response of Coastal Bermuda and Pensacola Bahia to fertilizer nitrogen with and without irrigation. The irrigated plots received an average of 12 applications of water totaling 11 inches each year. Water was applied by sprinkler irrigation when 30 per cent of available water in the upper 24 inches of soil was used. Ammonium nitrate was the source of nitrogen in this experiment as well as in others reported in this publication. One-fifth of the total nitrogen was applied before growth started in the spring; the remainder was applied in four equal applications following the first four harvests:. All plots received fertilizer equivalent to 225 pounds of P 2 0 5 and 450 pounds of K20 per acre annually in 1956 and 1957. In 1958 and 1959, mineral fertilization was increased to 280 pounds of P 20 5 and 560 pounds of K20 per acre annually. Phosphate and potash were applied in three equal applications made before growth started in the spring and after the first and third cuttings. All plots received 1 ton of lime per acre in each of the years of 1955, 1957, and 1958. Yields. The effects of nitrogen fertilization and irrigation on forage yields are shown in Table 1 and Figure 1. Average yields of both species in the 4-year period show a large response to nitrogen with or without irrigation. During the dry summer of 1956, Coastal Bermuda was much more responsive to nitrogen without irrigation than was Bahia. Average response of both species to, irrigation in the 4-year period was relatively small. However, this differed from year to year and within seasons of a given year depending on amount and distribution of rainfall during the growing season. The greatest response to irrigation occurred in 1956, which was the driest of the 4 years. However, there were periods of 2 weeks or more without rainfall during the other years when there was a response to, irrigation. Total rainfall during each of the growing seasons (April-September) was 19.9, 29.7, 31.3, and 25.3 inches for 1956, 1957, 1958, and 1959, respectively. The long-time average for the same period was 28.2 inches of rain. According to a recent study of

z
0
TABLE

0
1.
EFFECT OF NITROGEN ON HERBAGE YIELDS OF COASTAL BERMUDA AND GREENVILLE FINE SANDY LOAM, THORSBY, ALABAMA BAHIA GRASSES GROWN ON

0n

z
Q

SeisIrrigation Seistreatment

Nitrogen applied annually, lb./ acre 1956 Lb. 1,348 4,940 8,473 9,837 1,971 8,350 13,622 17,816 1,263 3,652 3,554 3,746 2,547 8,364 11,514 15,432

Dry forage yield per acre 1957 Lb. 3,341 11,169 15,531 19,911 3,117 10,437 16,346 18,811 4,069 10,442 14,620 18,127 3,845 9,238 15,001 20,756 1958 Lb. 4,190 10,152 15,559 19,234 3,861 9,592 15,959 20,174 3,239 9,268 15,033 19,831 2,893 8,255 14,001 19,918 1959 Lb., 3,034 8,066 11,922 18,232 4,250 10,649 17,326 21,795 2,386 7,310 12,617 17,503, 3,406 8,491 14,571 20,016 Average 1956-59 Lb. 2,978 8,582 12,871 16,804 3,300 9,757 15,813 19,649 2,739 7,668 11,456 14,802 3,173 8,587 13,772 19,030

Dry matter produced per pound of N within each increment of N Lb. 37 33 23 43 42 27 33 29 20 ,36 35 26

Coastal Bermuda

Nonirrigated

Coastal Bermuda

Irrigated

Bahia

Nonirrigated

Bahia
Ilil~li l ~-I Illllllil

Irrigated
IVil ~-I

0 150 300 600 0 150 300 600 0 150 300 600 0 150 300 600

10

m

rn

z
0

0
Hn

Wn

6

ALABAMA AGRICULTURAL

EXPERIMENT

STATION

§9~

P!i

FIG. 1. Coastal Bermudagrass on left did not receive any nitrogen, whereas that on right got 600 pounds of N annually. Neither area was irrigated.

dItinlt;It oc~ticurreces inl .\Alala

(6), there

is ani c\ c.ii chiaice that

D ata on (if ects of iiitr)o('en avid i rri ation i l XXatei tuse cfficielleX for~ 1956 anid 19.57 are aj\ cii inl fale 2. \\ah I. IIse cief 91ic- is ('xpressed as pottld~s of (lr\ mllatter produt ced per acre incrh of water u sed. Thcre wXas a mar-ked incerease 1 sef(fhiiccX Xith ill rcasil) Y rates of tii tr01lI.11 exepft ill X aiter-tis rri for titirri !rated Bal iamyass in 195(6. 1 gationI decreased wXatcr15Xas 1 )1olal \ the resutl of' ('\essiX c isc effeiei cX inl 1957. Tis

Wa~ter-Utse FfficiencN.

Ixtl2.

Eii

ll(:i alixn

Arnor; \iiuii : Ni

, Hxuni

lIum..sIrioN (;ii\OI~

o\'
Gm(iti\

ui Ns

Sv LIiuN( I'l N 0N11"10

(i

(Co5 \sIi,

A Ei t

Nitioe ussIi

m)xatte prodced per 19146 LI). 81 297 592 59 219 5.32 1957 Lb. 1964 6455 1,1648 114 383
6490

acr

inchs of xxater

II).
\utirigatcd

ce
II

I1)56j Lb 1. 764 '20 225 76 2503 161

1957 1,h. 2:39 612 1,06143 1-11 7142

50
600)1

lriiUatt(

Il 150 600)1

Scal led wa ter'-use eitcienoc.

NITROGEN and MOISTURE REQUIREMENTS

of GRASSES

7

water at times, since some irrigations were immediately followed by heavy rains. Seasonal Distribution of Forage. During the dry season of 1956, irrigation increased yields from nitrogen rates shown, Figure 2, at all harvest dates except the last. The response to irrigation was especially large at the 600-pound rate of nitrogen during the first half of the season. The higher yields from nonirrigated plots for the last harvest may be a result of less removal of nitrogen and other nutrients in previous harvests because of low yields. Irrigation had little effect on seasonal distribution at either rate of nitrogen during the 1958, season, which had the highest rainfall of any season in the 4-year period, Figure 3. The response to 600 pounds of nitrogen over 150 pounds was much larger for the first half of the season than for the last half. Neither nitrogen nor irrigation kept yields from declining during the latter part of the season. The problem of declining yields after July needs further study. Nutrient Removal. The production and removal of high yields of forage may create fertility problems much earlier than under less intensive management. Percentage of nitrogen, phosphorus, and potassium in the plant material and total removal of these
Dry matter

Lb./A. 5,000

4,000

Irrigated

3,000

-

2,000
Nonirrigated

""0 -. -

150 Lb. N
-"

J-'
"--Nonrrigaed0 Lb.N

1,000
-

irrigated

June 1

July

August 1 Harvest Dates

Sept.1

c0t.1

FIG. 2. Seasonal yields of Coastal on Greenville fine sandy loam at Thorsby in 1956, a dry season, show some response to irrigation at two levels of N.

8

ALABAMA AGRICULTURAL EXPERIMENT STATION

Harvest

Dates

FIG. 3. These seasonal yields of Coastal Bermudagrass on Greenville fine sandy loam at Thorsby show little response to irrigation in 1958, a wet year.

elements are reported in Table 3. Nitrogen content, as well as
total uptake of N, increased with increasing nitrogen fertilization. Seventy per cent of the added nitrogen was recovered in the Coastal clippings and 58 per cent in the Bahia where 600 pounds of nitrogen was added. Recovery was about the same at the 150pound rate of nitrogen. At the 600-pound rate of N, the nitrogen content of Coastal was equivalent to 15 per cent protein and that of Bahia was 12.25 per cent.
TABLE 8. EFFECT OF NITROGEN APPLICATIONS ON PERCENTAGE COMPOSITION AND TOTAL UPTAKE OF NITROGEN, PHOSPHORUS, AND POTASSIUM BY COASTAL BERMUDAGRASS AND BAHIAGRASS, GREENVILLE FINE SANDY LOAM, THORSBY, ALABAMA, 1957

Nitrogen N Species applied Speciesannually, Content Total lb./acre uptake Pct. Lb./a. Coastal Bermuda Pensacola Bahia 0 150 600 0 150 600 1.23 1.45 2.45 1.27 1.43 1.96 89 150 457 44 120 394

P05
2

KO 20 Content ntent Pct. 1.58 2.05 1.80 1.70 2.04 2.05 Total uptake Lb./a. 49 214 330 62 182 414

ContentTotal Content uptake Pct. 0.60 0.64 0.62 0.55 0.58 0.48 Lb./a. 18 66 115 21 48 101

NITROGEN and MOISTURE REQUIREMENTS

of GRASSES

9

Potassium content of herbage increased only with the first increment of nitrogen, whereas potassium uptake increased through all rates of nitrogen. The uptake of potassium at the 600-pound rate of N was equivalent to 414 pounds of K20 per acre by Bahia and 330 pounds by Coastal Bermuda. Removals of this magnitude would soon deplete the available potassium supply in most Alabama soils unless properly fertilized. Large tonnages of hay also remove considerable phosphorus. The herbage produced at the 600-pound rate of nitrogen contained phosphorus equivalent to over 100 pounds of P 20 5 . Soil Analysis. Data showing effects of nitrogen applications and crop removal on acidity and levels of soil phosphorus and potassium are given in Table 4. The effect of nitrogen applications on acidity was pronounced in the upper 3-inch soil layer and was evident in the 3- to 6-inch layer. In the 0- to 3-inch layer, the pH dropped from 6.6 with no nitrogen to 5.4 with 600 pounds of nitrogen, even though 3 tons of lime had been applied during the 4-year period. However, there was no effect below 6 inches as indicated by pH values. Soil phosphorus and potassium decreased with increasing nitrogen applied. Much of the decrease can be accounted for by greater removal in herbage, which increased as a result of nitrogen fertilization. Most of the change in soil potassium was found in the upper 9 inches of soil, whereas the phosphorus change was limited to the upper 3 inches. Some of the decrease in extractaTABLE 4. EFFECT OF AMMONIUM NITRATE APPLICATIONS TO COASTAL BERMUDAGRASS ON CERTAIN CHEMICAL PROPERTIES OF SOIL SAMPLES COLLECTED IN 1958, GREENVILLE FINE SANDY LOAM, THORSBY, ALABAMA

Depth of sample, inches
0-3 3-6 6-9

pH
6.6 6.5 6.2

12 Acidity and P2 0 5 and K2O levels, three rates of N 300 pounds N 600 pounds N No N P20 5 K2 0 pH PO5 K20 pH P2 0 5 K2 0

-.

-.

p.p.m. 198 22 3

p.p.m. 248 189 114

6.1 6.3 6.3

p.p.m. 118 40 6

p.p.m. 135 96 57

5.4 6.1 6.2

p.p.m. p.p.m. 98 126 22 73 8 46

12-15 -..... 5.4 15-18 -... 5.3 18-24..... 5.2
1 Original

9-12-....

5.9

0
0 0 0

50
36 33 27

6.0
5.7 5.4 5.3

0
0 0 0

32
24 21 19

5.8
5.6 5.4 5.2

0
0 0 0

32
25 21 21

soil sample collected in 1955 had a pH of 6.1 and contained 85

p.p.m. P20 5 and 76 p.p.m. K20. SAll plots received 2,250 pounds of 0-10-20 the first 2 years and 2,800 pounds of 0-10-20 the second 2 years. All plots received 1 ton of lime per acre in 1955,

1957, and 1958.

10

ALABAMA

AGRICULTURAL

EXPERIMENT

STATION

ble phosphorus may be caused by greater chemical fixation of phosphorus resulting from increased acidity.
Sumter Clay, Marion Junction

An experiment was established on Sumter Clay to determine the response of Coastal Bermuda to rates and frequencies of nitrogen applications. Yield data are given in Table 5 for 1957. Caley peas (Lathyrus hirsutus) were grown in the Coastal sod the previous winter but were grazed closely in the spring to keep to a minimum the effect of legume nitrogen on the grass. Although there was a response to as much as 600 pounds of nitrogen, it was probably not economical beyond 160 pounds. There was no yield advantage from split applications of nitrogen on this soil.
TABLE

5.

YIELDS

AND NITROGEN

CONTENT OF

COASTAL BERMUDAGRASS RATES AND

HERBAGE OF

GROWN ON SUMTER CLAY AT VARIOUS

NITROGEN APPLICATIONS,

FREQUENCIES BLACK BELT SUBSTATION

Rates and frequencies of nitrogen, pounds per acre1 First 0 40 40 40 80 120 200 100 80 0 Second 0 0 40 40 0 0 200 100 80 0 Third 0 0 0 40 0 0 200 0 0 0 Total 0 40 80 120 80 120 600 200 160 0

Dry forage yield per acre Lb. 4,878 5,505 6,492 8,440 7,171 8,444 11,632 9,894 9,878 5,106

Nitrogen content by harvests First Pct. 1.54 1.74 1.78 1.73 1.92 2.03 2.14 1.87 1.84 1.65 Second Pct. 1.41 1.33 1.57 1.42 1.33 1.41 2.06 1.78 1.76 1.44 Third Pct. 1.55 1.66 1.70 1.74 1.60 1.74 2.14 1.71 1.71 1.68

SNitrogen was applied one-third before growth started in spring and the remainder in split applications after first and second cuttings.

There was a tendency for nitrogen content of herbage to increase with increasing nitrogen rates, Table 5. However, the effect of nitrogen treatment on nitrogen content was not as striking as at other locations.
Cecil Sandy Loam, Auburn

At the Dairy Research Unit near Auburn an experiment was begun in 1955 to determine the effect of nitrogen and irrigation on Coastal Bermuda and Bahia grasses. Both showed a response to 200 pounds of nitrogen, but neither responded to irrigation,

NITROGEN and MOISTURE REQUIREMENTS

of GRASSES

11

TABLE 6. YIELDS OF COASTAL BERMUDA AND BAHIA GRASSES AT Two LEVELS OF NITROGEN AND IRRIGATION ON CECIL SANDY LOAM, DAIRY RESEARCH UNIT, AUBURN, ALABAMA, 1956-59 AVERAGES

Nonirrigated Lb. 2,265 2 00 - - - - - - - - - - - - - - - - - 8,488

Nitrogen applied annually, lb./acre

Dry forage yield per acre Coastal Bermuda Irrigated Lb. 8,133 8,872 Bahia Nonirrigated Lb. 8,510 8,445 Irrigated Lb. 4,744 8,675

Table 6. The nitrogen rate may not have been high enough to permit an irrigation response under prevailing natural rainfall. Dewey Silty Clay Loam, Belle Mina An experiment was conducted on Dewey silty clay loam from 1956 through 1959 to determine the response of Coastal Bermuda and Bahia grasses to irrigation. Average yield data show that Coastal did not respond to irrigation and that Bahia produced a little over a ton more dry matter when irrigated, Table 7. All plots received 200 pounds of nitrogen per acre. Humphreys Silt Loam, Belle Mina A study identical to the one on Dewey silty clay loam was conducted on Humphreys silt loam.. Results for the 4-year period show that irrigation increased yields of Bahia by about 3,000 pounds, but the increase was only about 1,000 pounds for Coastal, Table 7.
TABLE 7. EFFECT OF IRRIGATION ON HERBAGE YIELDS OF COASTAL BERMUDA BAHIA GRASSES ON Two SIrES, TENNESSEE VALLEY SUBSTATION AND

Species

r Irrigation treatment 1956 Lb.

Dry forage yield per acre 1957 Lb. 8,621 10,455 10,606 15,351 1958 Lb. 7,853 8,594 7,487 8,758 1959 Lb. 9,188 6,411 11,261 9,512 Average Lb. 9,598 9,882 9,473 11,771

Dewey silty clay loam Coastal Bermuda Nonirrigated Irrigated Pensacola Bahia Nonirrigated Irrigated Humphreys silt loam

18,212 14,070 8,589 18,464

Coastal Bermuda
Pensacola Bahia

Nonirrigated
Irrigated Nonirrigated Irrigated

11,982
14,448 7,047 11,816

9,390
10,659 7,477 11,425

6,154
7,128 4,330 7,161

8,863
8,237 13,861 14,223

9,097
10,118 8,054 11,156

TABLE

8.

...) YIELDS OF COASTAL BERMUDA AND PENSACOLA BAHIA GRASSES AND STEER GAINS Or NITROGEN ON GRAZING PADDOCKS, WIREGRASS SUBSTATION AT VARIOUS RATES

Species

Nitrogen applied annually,

Dry forage yield per acre 1953 Lb. 8,989 10,220 14,555
16,107

lb. /acre
0 80 160
320

1954 Lb. 3,243 5,757 9,642 3,071 4,252 5,503

1955

1956

1957

Coastal Bermuda

Lb. 4,950
8,432

Lb. 3,216
7,028

Lb. 4,941
7,836

Average 1953-57 Lb. 5,050
7,813

Average steer gain per acre, 1953-57 Lb. 254
337

ac

10,1243

11,028
13,458

10,632
13,602

11,241
14,093

11,303
13,419

482
625

Pensacola Bahia

0 80 160

4,414 6,670 7,802

3,338 6,260 7,362

2,559 5,892 5,108

2,734 4,540 6,590

3,205 5,482 6,473

221 291 353

w

a
TABLE

9.

EFFECT OF

NITROGEN ON HERBAGE YIELDS OF COASTAL

BERMUDA AND BAHIA

ON SMALL PLOTS, WIREGRASS

SUBSTATION

Nitrogen
Species

Dry forage yield per acre
1953

C

annually,

applied

lb. /acre Coastal Bermuda 0 80 160 320 0 80 160 320

1954 Lb. 2,710 4,688 7,321 9,035 3,230 4,929 5,258 6,525

1955 Lb. 2,846 5,884 9,154 14,214 2,706 6,264 9,108 12,483

1956 Lb. 3,359 5,769 9,113 11,937 4,120 6,642 9,272 11,276

1957 Lb. 1,488 2,908 5,037 9,972 2,043 4,263 8,578 12,411

1958 Lb. 1,698 3,312 5,382~ 8,473 1,548 3,617 5,401 9,462

1959 Lb. 1,480 4,418 6,516 8,948 1,570 3,988 4,408 8,653

Lb. 7,226 8,920 11,170 11,769 6,822 7,926 8,133 9,476

Average 1953-59 Lb. 2,972 5,128 7,670 10,625 3,148 5,376 7,165 10,041

-- C
m

-I

z
-I

Pensacola Bahia

--1

a z

NITROGEN and MOISTURE REQUIREMENTS

of GRASSES

13

Norfolk Sandy Loam, Headland In 1952 a grazing test was begun at the Wiregrass Substation with Coastal Bermudagrass at four rates of nitrogen and Pensacola Bahiagrass at three rates. The experiment was laid out in a randomized block design with two replications. The paddocks were 1.75 acres in size. Nitrogen was applied in three applications, March 1, May 15, and August 1. Beef gains were determined by grazing yearling steers. Cages were used to measure amounts of forage produced and amounts consumed by steers. Small plots adjacent to the paddocks were clipped to determine the forage yield response of Coastal Bermuda and Bahia to nitrogen. Results from Grazing Paddocks. Coastal Bermuda produced more forage and beef than Bahia at all nitrogen rates, Table 8. The low yields of Bahia may have resulted in part from a weakening of the stand brought about by disking each fall for establishment of legumes:. Also, part of the higher production of Coastal was from a partial stand of crimson clover in the Coastal, as compared with little or no crimson in the Bahia sod. Clipping Yields from Small Plots. Forage yields were about the same for the two grasses at all rates of nitrogen, Table 9.
TABLE 10. EFFECT OF NITROGEN APPLICATIONS TO COASTAL BERMUDAGRASS GROWN ON NORFOLK SANDY LOAM ON SOIL ACIDITY AND PHOSPHORUS AND POTASSIUM LEVELS, WIREGRASS SUBSTATION

Nitrogen applied annually, lb./acre

Depth of a so il sample, inches

pH

P20 5 p.p.m.

K20 p.p.m.

0
0 0 80 80 80

0-6
6-12 12-18 0-6 6-12 12-18

5.8
5.5 5.3 5.7 5.6 5.0

229
42 31 147 28 15

55
96 62 49 43 36

160 160
160 320 320 320

0-6 6-12
12-18 0-6 6-12 12-18

5.5 5.3
4.9 4.6 5.1 4.7

181 63
14 88 31 12

55 68
81 23 26 20

annually. Original surface soil had a pH of 5.0 and contained 58 p.p.m. P 05s.
2

' Area limed in 1952 and again in 1955.

All plots received 1,000 pounds 0-14-14

14

ALABAMA

AGRICULTURAL

EXPERIMENT

STATION

These data are in line with results from other locations showing that Coastal and Bahia will produce about the same amount of herbage when managed alike. Soil Analysis. Nitrogen applications to the small plots affected some chemical properties of a Norfolk sandy loam, Table 10. Although the plots were limed according to soil test recommendations at the beginning of the test and again at the end of the 1955 season, plots receiving the highest rate of nitrogen (320 pounds N annually from ammonium nitrate) had become highly acid by 1960. There was a tendency for soil phosphorus and potassium to decrease with increasing nitrogen applications. DISCUSSION Both Coastal Bermuda and Bahia grasses have a high yield potential when given adequate nitrogen and water. Either grass can produce 10 tons or more of dry forage per acre annually. With a yield potential of this magnitude, production of feed can be increased without increasing acreage. How much can profitably be spent for fertilizer and water will not only depend on the cost of these production practices, but also on the quality of forage produced and how it is utilized. Irrigation The average response of either grass to irrigation was not large at any of the locations. However, average response of Bahia to irrigation was greater than that of Coastal at three of the four locations where irrigation was a variable. Bahia gave a much greater response to irrigation than Coastal Bermuda at Thorsby during the 1956 season, which was unusually dry. If both grasses are grown and there is a choice of land, Coastal should be established on the drier areas and Bahia on the wetter ones. The economics of irrigating grasses is complex. A few inches of water during extended dry periods may be profitable. Because rainfall is unpredictable, moisture applications are often ineffective. Rain following irrigation destroys the value of irrigating. Results of these experiments indicate that irrigation is usually not an economically sound practice in the production of forage from Coastal Bermuda and Bahia grasses.

NITROGEN and MOISTURE REQUIREMENTS of GRASSES

15

Nitrogen Results show that both grasses are responsive to nitrogen applications. The amount of nitrogen that can be used to advantage will vary from farm to farm. Workers in Georgia (5) found that Coastal Bermuda showed a yield response to as much as 900 pounds of nitrogen during a favorable season. However, they concluded there was not enough response above the 600-pound rate to pay for the additional nitrogen. Protein content of grasses can be increased by nitrogen fertilization, but it is difficult to determine the value of the additional protein. Until more is known about the value of higher protein contents, nitrogen fertilization should be based mainly on yield response. Assuming a gross return of $2 should be realized for each $1 spent for nitrogen, each additional pound of nitrogen should produce at least 22 pounds of dry matter (based on dry herbage valued at $20 per ton and N at 11 cents per pound). At two locations with four or more rates of nitrogen, the response of Coastal Bermuda decreased to 22 pounds or less at nitrogen rates of about 200 and 800 pounds per acre on Norfolk and Greenville soils, Figure 4. These figures are based on results from unirrigated plots. The average response curve for the two soils is also shown in Figure 4. This curve shows that a gross return of $8 can be obtained for each $1 spent for nitrogen up to 200 pounds per acre. The next 100 pounds returned only $2 for each $1 spent for nitrogen. Additional N will increase the lime, phosphorus, and potassium requirements, which will narrow the margin of profit from nitrogen. Effect of Nitrogen on Soil Acidity,
Phosphorus, and Potassium

Ammonium nitrate was the source of nitrogen at all localities. The acid-forming nature of ammonium nitrate and certain other nitrogen fertilizers has been recognized for many years (4). Acidity developed by 300 or more pounds of nitrogen annually will rapidly lower the pH of sandy soils to the point that grass yields may be lowered. The lime necessary to counteract this acidity must be figured in the cost of producing grass. Use of high rates of nitrogen and the subsequent removal of large amounts of herbage will create the need for higher rates of phosphorus and potassium. The data show that 10 tons of hay

16 16

ALABAMA

AGRICULTURAL

EXPERIMENT

STATION

ALABAMA AGRICULTURAL EXPERIMENT STATION

Dry forage 1,000 Lb. IA.

$1.10

Greenville

f.s.I.

/

/

...

Norfolk s.I.

Dollar values refer to returns per dollar spent for N figuring hay at $20 per ton and N at 11 per lb.

Pounds

N

per acre

FIG. 4. Response of Coastal Bermudagrass to nitrogen and returns per dollar spent for nitrogen are shown above for two soil types. Return for each dollar spent for nitrogen is shown for each 100-pound increment of N.

NITROGEN and MOISTURE REQUIREMENTS of GRASSES

17

will remove phosphorus and potassium equivalent to about 120 pounds of P20~ and 400 pounds of K20. Increased acidity from certain nitrogen sourees may increase the loss of potassium by leaching and decrease the. availability of soil phosphorus. The soil. analysis data show that soil phosphorus and potassium decreased appreciably with increasing rates of nitrogen applied. This emphasizes the need for periodic soil tests as a guide to proper fertilization. SUMMARY Field tests have been conducted the past 8 years to determine (1) the fertility and moisture requirements of Coastal Bermuda and Pensacola Bahia grasses, and (2) the effect of nitrogen fertilization on certain chemical properties of soils. The results are summarized as follows: 1. Both grasses are responsive to nitrogen fertilization and have a yield potential of 10 tons or more of hay per acre. 2. The average response to irrigation was not large for either grass at any location. It ranged from almost no increase to as much as 2 tons per acre. 3. Soil acidity increased with increasing rates of nitrogen applied. Rates of nitrogen in excess of 300 pounds per acre rapidly increased acidity of sandy soils to, a level considered unfavorable for forage crops. 4. The use of high rates of nitrogen and the removal of large tonnages of herbage will result in rapid depletion of soil potassium and phosphorus unless adequate amounts are supplied as fertilizers.

18

ALABAMA AGRICULTURAL

EXPERIMENT

STATION

LITERATURE CITED
(1)

E., AND STELLY, MATTHIAS. A Comparison of Coastal and Common Bermudagrasses (Cynodon dactylon (L.) Pers.) in the Piedmont Region: I. Yield Responses to Fertilization. Soil Sci. Soc. Amer. Proc. 50:457-459. 1958.
ADAMS, WILLIAM FISHER, F. L., AND CALDWELL, A. G.

(2)

The Effects of Heavy Rates of

Fertilizers on Forage Production and Quality of Coastal Bermudagrass. Agron. Jour. 51:99-102. 1959.

(3)

HOVELAND,

C.

S.

Bermudagrass

for Forage

in Alabama.

Auburn

(4)
(5)

Univ. Agr. Expt. Sta. Bul. 328. 1960. PIERRE, W. H. Nitrogenous Fertilizers and Soil Acidity: I. The Effect of Various Nitrogenous Fertilizers on Soil Reaction. Jour. Amer. Soc. Agron. 20 (3):254-269. 1928.
PRINE, C. M., AND BURTON, W. The Effect of Nitrogen Rate and Clipping Frequency upon the Yield, Protein Content and Certain

GC.

Morphological Characteristics of Coastal Bermudagrass (Cynodon dactylon (L.) Pers.). Agron. Jour. 48(7):296-301. 1956. (6) WARD, HENRY S., VAN BAVEL, C. H. M., COPE, J. T. JR., WARE, L. M., AND BOUWER, HERMAN. Agricultural Drought in Alabama. Auburn Univ. (API) Agr. Expt. Sta. Bul. 316. 1959.

NITROGEN and MOISTURE REQUIREMENTS

of GRASSES

19

ACKNOWLEDGMENT For their valuable contributions in helping to collect the data on which much of this publication is based, the authors are grateful to the following: W. R. Langford, formerly of the Agronomy and Soils Department; R. M. Patterson, Agronomy and Soils Department; G. H. Rollins, Dairy Science Department; L. A. Smith, superintendent, and H. W. Grimes, assistant superintendent, Black Belt Substation; J. K. Boseck, superintendent, Tennessee Valley Substation; and C. A. Brogden, superintendent, and J. G. Starling, assistant superintendent, Wiregrass Substation.

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