Research Update =60 1990 QRAIN ROPS FRST WNRA N CROPS RESEARC H PD-ATi EI S This is the first grain crops research report publshed m a new series. Rv s arch Update ' inaugu- S9 by th,' Alabama :-)" /,.; v ( Statioi (iAAES., This new series is meant to promote imel/ mportin of research ir '" crop t0on to ai proc ers of tnat particular commodity. in this ,ase, tne targe audience is -o: more information about grain crops production -di. the latest recommen- ,our county Extension Service office. I Grain Disease Ratings Available in Variety Reports Corn Incidence of virus diseases, maize chlorotic dwarf (MCD) and maize dwarf mosaic (MDM), was deter- mined in corn variety tests at four locations in central and northern Alabama. Levels of MDM were I to 3 percent in all tests, which was unusually low. Incidence of MCD was about 0.5 percent in two tests in central Alabama and ranged from 4 to 6 percent at the two northern loca- tions. Several hybrids showing no symptoms of either disease were found at all locations. All virus dis- ease ratings were included in the 1989 Corn Variety Report, which is available upon request from the Department of Research Informa- tion, 110 Comner Hall, Auburn Uni- versity, Alabama 36849. Wheat Several fungicides were evaluated forcontrol of foliar diseases on wheat at three locations in the State. Gen- orally, one or two applications of each fungicide were made between the time of flag leaf appearance and emergenceof the grain heads. At the Gulf Coast Substation in Fairhope, most of the 30 fungicidal treatments tested gave good to excellent control of leaf rust on susceptible cultivars. Yield increases associated with fungicidal treatments ranged from 0 to 24 bushels per acre. Similarly, several of the 15 fungicides evalu- ated at the Sand Mountain Substa- tion in Crossville gave good control of Septoria blotch. No yield increases were associated with any treatment at this location, presumably because the disease did not appear until late in the season. In additional tests at Fairhope and at the Wiregrass Substation in Head- land, initial applications of fungi- cides were made just after wheat began to tiller, followed by applica- tions at flag leaf or head emergence in an effort to control powdery mil- dew. The lack of continued devel- opment of the disease obviated any evaluation of fungicidal control; however, most of the fungicides controlled leaf rust. Meaningful evaluations of disease control and yield responses in these tests were confounded by heavy infestations of Hessian fly at both locations. Entries in small grain variety tests at 12 substations and experiment fields throughout the State were A LABAMA AGRICULTURAL EXPERIMENT STATION AUBURN UNIVERSITY LOWELL T. FROBISH, DIRECTOR AUBURN UNIVERSITY, ALABAMA rated for disease reactions. Gener- ally, disease incidence and severity were higher at most locations than in recent years. Powdery mildew was severe on wheat in most tests during winter and early spring but often did not progress beyond the lower leaves. Leaf rust and Septoria blotch were severe on some wheat entries at many locations. Stem rust occurred on some wheats in south Alabama, but usually at low levels. Downy mildew, an unusual and apparently insignificant disease, occurred sporadically in some wheat entries at one location in north Ala- bama. All disease ratings were in- cluded in the 1989 Small Grain Vari- ety Report, which also is available upon request from the Department of Research Information. R.T. Gudauskas, A.K. Hagan, and J.M. Mullen Tropical Corn A Late Season Option Tropical corn has been grown in Florida for grain and silage for sev- eral years. In north Florida, opti- mum planting date is from June 10 to July 10. AAES research is looking at how tropical corn can fit into crop- ping systems in Alabama. Reseeding Clover Provides Corn Nitrogen Requirements Nitrogen fertilizers make up the single largest portion of the total synthetic energy required to pro- duce an acre of corn in the United States. One alternative is growing legumes to offset the N needs of subsequent corn crops, but the cost of establishing legume cover crops has been too high and yields of these crops too low to be economically feasible. This need for reduced N fertilizer and increased legume production led to a series of tests at the Sand Mountain Substation at Crossville and the Wiregrass Substation at Headland. Crimson clover was se- lected as a legume crop because of its reseeding ability and potentially high yields. Treatments included continuous corn with no winter crops, soybean-corn rotation with no winter crops, continuous corn with fall-planted crimson clover, and soybeans with reseeding crimson clover. Subplots were treated with varying rates of commercial N fertil- izer. At Crossville, soybeans were more effective in providing early-season N, and clover was more effective in providing late-season N. When combined, the system resulted in an even more effective contribution to corn grain yield than that of continu- ous corn, regardless of N fertilizer rate. At Headland, the benefits of crop- ping systems were not as pro- nounced, and the responses were eliminated by N fertilizer. This sug- gested that increased yields were due to N and not to a rotation effect. However, the clover and soybean systems combined had an additive effect on corn yield. At both locations, reseeding crim- son clover, in combination with a soybean-corn rotation, consistently produced the highest yields of the systems studied. The two-year test was conducted under both optimal and inadequate rainfall conditions, and inclusion of reseeding clover in the rotation produced the highest yields in both circumstances. By adding reseeding crimson clover to the soybean-corn rotation, research- ers were able to provide from 60 to 140 pounds of N per acre for corn. Under inadequate rainfall condi- tions, reseeded clover behind soy- beans produced 33 percent more dry matter and 31 percent more total N than planted clover at the two loca- tions. Under optimal rainfall condi- tions, reseeded clover produced 73 percent more dry matter and 72 percent more total N. At Headland, reseeded clover produced up to 140 percent more total N than planted clover. When reseeding clover was first established after corn, there were no significant differences in either whole-plant dry weights or N pro- duction, which indicates the differ- ences in subsequent years were due to reseeded versus planted corn, and not to the previous summer crop. L.J. Oyer and J.T. Touchton A study at the Sand Mountain Substation in Crossville wasdesigned to determine the optimum nitrogen rate and applica- Tropical Corn Grain Yiel Clover and Fallow Syste Yield/acre. bv I System 0 45 Bu. Bu. Clover................ 45 59 Fallow................ 11 39 tion time for tropical corn in a fallow system and a system with reseeding crimson clover. The late planting date of tropical corn allows clover to naturally reseed, eliminating the cost of annual seeding. Two hybrids, Dekalb X678C and Pioneer X304C, were planted with a no-till planter with in-row subsoil- ers on June 28 at a seeding rate of 23,000 seed per acre. Yields were reduced due to drought in July and September, and to an early frost (the earliest ever recorded). Grain yields averaged 57 bushels per acre for the Dekalb hybrid, regardless of N application time. The Pioneer hy- brid averaged 50 bushels per acre when all N was applied at planting, and 57bushelsper acre when N was split applied (one-third at planting and two-thirds when corn was 12 inches tall). In the clover system, N applica- tion time was not critical. Tropical corn averaged 60 and 62 bushels per acre, respectively, when N was applied at planting versus applied in split applications. In the fallow system, yields were reduced from 53 to 46 bushels per acre when N was applied at planting rather than as a split application. The beneficial ef- fect of the clover mulch is shown in the table. 1 The benefits of the clover mulch are more striking considering the system eliminates seed costs after initial establishment. Preliminary test results indicate that June 7-20 would be a good "window" for plant- ing tropical corn in north Alabama, and 7 to 14 days later for central and south Alabama, respectively. Based on the Auburn test, it ap- pears that other nonreleased varie- ties of tropical corn may per- form better than the only variety currently available (Pioneer X304C). Planting depth of Pioneer X304C is 180 critical. In the Auburn tests, plant stands were erratic Bu. when seed were planted 64 deeper than 1 inch. 59 D.W. Reeves, P.L. Mask, and J.T. Touchton Managing N Fertilizer On Winter Wheat Nitrogen (N) is the most limiting factor in the production of winter wheat in the Southeast. Winter wheat is planted in Alabama in late October to mid-December. About one-third of the fertilizer is applied at planting and the re- Whet mainder in a late win-teror Nitrogen early spring, applied, when rapid Ib. /acre plant growth starts. Winter rains will of- Brewton ten delay the 6o .................. application of 90 ----------------- ----------- application .. ............ N and this can 150........... ......... 150 ............................ result in re- duced yields, Monroeville therefore it 60 ............................. 90 ............................. would be ad- 120 ............. vantageous to 150 ........................ apply all of '30 pounds per acr the N in the 2 All nitrogen appliec fall. Unfortunately, fall-applied N can be lost in some winters through leaching and denitrification. If nitrification inhibitors could be used to prevent the loss of fall-ap- plied nitrogen, all of the N could be applied at planting and delayed spring application due to wet fields would not be a yield-reducing vari- able. The objective of this study was to determine if nitrification inhib- itors (N-Serve and DCD) would permit fall-only N application. Wheatwasplanted inlateautumn with N rates ranging from 60 to 150 pounds per acre. N treatments in- cluded fall-spring split application and fall application only with no inhibitor (None), N-Serve (NS), and DCD. Wheat yields given in the table indicate that the standard fall-spring split application of N is superior to fall-applied N, with or without an inhibitor. With fall-spring split applications, yields peaked with 120 pounds per acre N at Brewton and 90 pounds per acre at Monroeville. At these optimum N rates, the inhib- itors improved yields when com- pared to the fall-only N application at Brewton, but they resulted in infe- rior yields when compared to the fall-spring split application. R.R. Sharpe and J.T. Touchton at Yields as Affected by Nitrogen Treatments nd Nitrification Inhibitors, 4-year Average Fall- spring - Bu. Yield/acre, by N treatment Fall Fall, none 2 NS Monitoring Nitrogen in Wheat Some states and private consult- ants advocate intensive monitoring of wheat during late winter and spring growth to determine whether supplemental nitrogen applications are needed. However, interpreta- tion of plant nitrogen concentrations in wheat is difficult during this pe- riod of rapid growth. Tests at four locations in 1986 showed that conventional N fertili- zation in late winter resulted in slightly higher N concentrations but considerably higher grain yields than when fertilization was based on weekly monitoring of plant N con- centrations. Experiments at the E. V. Smith Research Center in Shorter since 1987 and at the Tennessee Valley Substation in Belle Mina in 1989 have attempted to correlate grain yield with plant N concentra- tion during Feeke's growth stage (GS) 6 to 10.1 (early jointing to grain fill). Regardless of the time or amount of topdress N applied, N concentration in wheat plants in- creased rapidly in mid-February (GS4) to mid-March (GS8). Highest grain yields were associated with DC B 34 36 4; 44 .................... 34 30 30 .................... 42 31 36 ................... 48 32 39 ----------........ 49 42 42 .................... 49 47 49 .................... 56 55 44 - 56 53 56 ................... 54 54 53 e applied at planting and the remainder applied in spring. I at planting. maximum plant N concen- trations above 4.0 percent during GS 6 through GS 10.1. Although plant nitro- gen analyses can indicate all, severe deficiencies, theyare ,D of little value in making u. supplemental N recom- mendations. These tests 4 indicate that applying all 6 of the topdress nitrogen at or before rapid spring growth begins (GS4), which is the conventional 8 way of topdressing nitro- gen on wheat in Alabama, gives best results. C.C. Mitchell and P.L. Mask d In ms N rate 90 Bu. 60 51 Maximum Wheat Yields Require Sulfur Fertilization A study to determine sources, rates, and time of sulfur application was conducted at the Brewton Ex- periment Field and at the Wiregrass Substation in Headland to investi- gate ways of preventing and/or correcting sulfur deficiencies on wheat. Although grain yields were low on the sandy soils at both locations, sulfur deficiencies were observed in 2 of the 3 years the test was con- ducted. At least 20 pounds per acre of topdress sulfate sulfur, such as amnmonium sulfate or gypsum, was necessary to consistently prevent yield losses from sulfur deficiencies. Fall-applied sulfate sulfur may be leached out of the rooting zone by the time rapid late-winter and spring growth begins. Elemental sulfur, such as wettable sulfur powder, is not effective when topdressed in late winter, but may be applied at planting. Elemental sulfur must be oxidized to the sul- fate form by soil bacteria before it can be taken up by plants, and bacte- rial activity in soils is low in cool, winter weather. Sulfur deficiency is difficult to correct once symptoms are observed. Ammonium sulfate and gypsum always resulted in near maximum yields when topdressed at Feeke's growth stage GS 4 (late tillering). When application was delayed until GS8 (late jointing), yields were about the same as the check, where no sulfur was applied. Deficiencies were easily diagnosed with plant analysis, but soil tests for sulfur were difficult to interpret because of sul- fur's mobility in the soil. C.C. Mitchell and P.L. Mask Hessian Fly Damage to Wheat Hessian fly damage has been as- sociated with poor wheat yields over the past 10 years in Alabama. Prior to 1980, out- breaks of Hessian fly occurred only every 7 or8years,but during the last decade this species has been a regular pest of small grains. Extensive field collec- tions of Hes- sian fly in many differ- ent wheat va- rieties were taken during April and May 1989. Most of the damaging infestations of Hessian fly occurred in central and south Ala- bama. In wheat examined at several locations in the Tennessee Valley, infestations were low or absent in both susceptible and resis- tant cultivars. Wheat samples taken from Tallassee, Camden, Dothan, and Fairhope were heavily infested. Commonly planted varieties such as FL 301, FL 302, and Hunter had 80 per- cent to 93 percent of the stems infested, table 1. In many in- stances the wheat was a total loss. A Hessian fly rear- ing and testing pro- cedure has now been developed and Hes- sian fly taken from the variety collec- tions are being tested in the labora- tory for biotype. Heavy parasite in- festation of Hessian fly reduced the Cultivar Central South Stems Flies/ Stems Flies/ infested stem infested stem Pct. No. Pct- No Auburn .............................. 20.0 Caldwell .................... 26.7 Coker 916 .......................... 86.7 Coker 9766 ............................ 46.7 C om pton ................................ 0.0 F illm o re .................................. 20 .0 Florida 30 1 ............................. 93.3 Florida 301H ................. -- Florida 302 .................. 80.0 Hunter ....................... .. M assey .............................. 13.3 M cNair 1003 .......................... 53.3 P ioneer 2548 ......................... .. Pioneer 2550 ......................... 0.0 Saluda .................... 6.7 Stacy .................... 0.0 Terral 817 .......................... 66.7 Tyler ....................... 60.0 efficiency of biotype deter during the winter of 1989 (1990) fly collections will b the laboratory for biotype. Results of insecticide scre shown in Table 2. 1.0 2.6 2.9 1.7 0.1 4.4 7.6 0.3 5.5 3.5 0.2 0.9 7.5 0.1 0.3 0.0 mination Spring tested in eningare P.M. Estes Table 2. Effects of Planting Date and Disulfoton Treatment on Wheat Grain Yield, 1987 Cultivar Treatment' FI 3022 ....... No Yes Terral 8172 ....... No Yes Masseys ............ No Yes Stacys Yield/acre, by planting date Sept. Oct. Nov. Av. Bu. Bu. Bu. Bu. ...... No Yes 'In-furrow treatment of disfuloton at 0.75 pound ai per acre 'Susceptible to Hessian fly. 'Some tolerance or resistance to Hessian fly. Table 1. Hessian Fly Infestation of Selected Cultivars, 1989 Requests, by region of Alabama Ryegrass control in Wheat Weed control is a primary concern in wheat production. Annual ryegrass is a common weed species known to reduce wheat yield and quality, and it infests some areas in almost every county in the State. Two experiments were initiated in the fall of 1988 to evaluate two rates and four application timings of Hoelon? (diclofop) for annual ryegrass control. At the Prattville Field, annual ryegrass seeds were sown broadcast at 20 pounds per acre to the surface of a prepared Lu- cedale fine sandy loam soil. Saluda wheat seeds were then planted at 70 pounds per acre in 7-inch rows. Hoelon was applied preemergence on September 23, and postemergence on October 13, October 26, and No- vember 11. At Tallassee, planting was identi- cal to that at Prattville except wheat and ryegrass seeds were planted Oc- tober 28 into a Norfolk sandy loam soil. Preemergence treatments were applied November 1. Postemergence treatments were applied November 1 and December 8, 1988, and January 12,1989. Ryegrass control on May 5, 1989, with Hoelon was good to excellent (82 to 99 percent) with all applica- tions. Wheat yield was good with all Wheat Yield as Affec Hoelon treat- Application and ments rang- ing from 38 to Rate and time' F 41 bushels a per acre, see thetable. W here rye- 1.5 pints, PRE ............ grass was not 3.0 pints, PRE ............ controlled, 1.5 pints, POT 2 ......... wheat yield 3.0 pints, POT 2 ......... 1.5 pints, POT 4 ......... averaged 30 3 pints, POT 4 ......... bushels per 1.5 pints, POT 8 ......... acre, see the 3.0 pints, POT 8 ......... Hand weeded ............. table. N ontreated ................. Tank mix- ing Hoelon 'POT 2 = postemerg with 2,4-D 2 Hoelon 3 EC; 2,4-D resulted in less ryegrass control, ranging from 53 to 87 percent. This antagonism was reduced some by increasing the Hoelon rate. Although ryegrass control with Hoelon plus 2,4-D was considerably less, wheat yield was only slightly less in some instances. Ryegrass control on May 3, 1989, was excellent (93 to 99 percent) for all Hoelon treatments except for the 1.5 pints per acre rate applied post to ryegrass at the 8-leaf stage (83 percent). Wheat yield for treat- ments receiving only I-oelon ranged from 22 to 31 bushels per acre. Yield data indicate reduced yields three out of four times when the higher rate (3 pints per acre) was used. The bestapplicationrate for Hoclon alone was 1.5 pints per acre and the best time for this application was when the ryegrass had four leaves. When Hoelon was tank mixed with 2,4-D, ryegrass control was gener- ally reduced. Control was always better with the higher rate of Hoelon, and the larger the ryegrass was at time of application the less control. These data,like those from Prattville, show that adding 2,4-D to Hoelon causes antagonism. When 2,4-D was tank mixed with Hoelon, wheat yield was reduced by an average of 4 to 8 bushels per acre. This reduction was related to less ryegrass control and a moderate degree of 2,4-D injury. Robert H. Walker cted by Hoelon and Hoelon + 2,4-D Time of Rate, Prattville and Tallassee, 1988-89 Prattville yield/acre Hoelon Hoelon ilone 2 + 2,4-D 2 Tallassee yield/acre Hoelon Hoelon alone 2 + 2,4-D 2 Bu. Bu. Bu. Bu. ..38 ..38 ..39 ..40 ..41 .40 41 .. 40 ..38 ..30 ence to ryegrass with two leaves, etc. amine 3.8. Heavy Midge Infestation Causes Greatest Sorghum Damage Sorghum midge is a frequent in- sect pest of grain sorghum in Ala- bama and causes serious yield re- ductions if plants are infested dur- ing critical growth periods. To de- termine the relationship among dif- ferent population densities of sor- ghum midge and damage caused to the crop, sorghum bloom stage was monitored to better understand the critical period for midge attack. Seventy-five percent of the plants (Northrup King Savanna 5 hybrid) grown in the field required 17-18 days to finish flowering when plant growth was uniform, and 65 percent to 69 percent of the plants required 22 days to finish flowering when crop growth was uneven or affected by low temperatures. Flower pro- duction was not affected by the in- secticides (Lorsban or Sevin) used to control sorghum midge. Midge infestation was estimated by sampling panicles throughout the period of greatest flower produc- tion (about 8 days for uniform sor- ghum plots and 12 days for uneven plots). Midge populations were not abundant through the bloom period in any of the four planting dates, but the greatest damage occurred in plots with the longest bloom period. Obviously those sorghum plantings were exposed to midgeattack longer. Midge population densities varied markedly in the field from one day to another. The mean population densities per sorghum head were 1.8, 2.6, 0.9, and 1.4 adult females in the first, second, third, and fourth plantings, respectively. Midge sampling started 5 to 6 days after sorghum began to flower or when approximately 20-35 percent of the plants were in full bloom. Yield losses of 3.8 percent, 36.0 percent, 12.1 percent, and 23.7 per- cent were apparently caused by 1.8, 2.6, 0.9, and 1.4 midges per panicle, respectively. No significant correla- tion was found between number of ovipositing midges and damage caused to sorghum in the field. However, all plantings except the first one exhibited the greatest yield losses with higher midge densities. Probably the great day-to-day dif- ference in midge populations was responsible for the large variation in yield data. A. Torres and P.M. Estes Seeding Rates, Fertility For Grain Sorghum Grain sorghum is often grown in Alabama as an alternative crop, and is frequently planted in situations in which environmental conditions delay corn planting. Wide ranges in seeding rates and N fertilizer rates are commonly used for sorghum, and research sought to determine if the N fertilizer requirements are related to seeding rates. Pioneer B8516 grain sorghum was planted on June 26, 1989, at seeding rates ranging from 50,000 to 140,000 seed per acre. N fertilizer (prilled ammonium nitrate) wasbanded next to the row on July 24 at N rates ranging from 0 to 120 pounds per acre. EDITOR'S NOTE Mention of company or trade names does not indicate endorsement by the Alabama Agricultural Experiment Station or Auburn University of one brand over another. Any mention of non label uses or applications in excess of labeled rates of pesticides or other chemicals does not constitute a recommendation. Such use in research is simply part of the scientific in- vestigation necessary to fully evaluate materials and treatments. Information contained herein is avail able to all persons without regard to race, color, sex, or national origin. Funds provided by the Alabama Legislature provide the major fi- nancial support for Alabama Agri- cultural Experiment Station re- search. Hatch funds from the U.S. government also represent an im- portantfundingsource. Since these funds are limited, however, many areas of research would go unsup- ported except for financial support from various granting agencies, commodity groups, and other friends of the Experiment Station. Contributions of these supporters to AAES research programs are ac- knowledged with gratitude. Among these supporters of AAES As shown in the table, grain yields were relatively low, but were in the expected range for late June-planted sorghum in south Alabama. Peak yields of 64 bushels per acre occurred with the 80 pounds per acre N rate, which is the recommended rate for grain sorghum. Seeding rates had no influence on yields or N fertilizer requirements. M. Abdoulkadri and J.T. Touchton research, the following are recog- nized and thanked for their contri- butions to grain crops research: Alfa Wheat and Feed Grain Producers Allied Signal Corporation CIBA-GEIGY, Inc. E. I. Dupont Inc. Gustafson, Inc. Mobay, Inc. Rohm and Haas, Inc. Tennessee Valley Authority United States Agency for International Development United States Department of Agriculture, Office of International Cooperation Yield of Late Planted Grain Sorghum as Affected by Seeding Rate and N N rate, lb./acre 5 0 ...... ......... 4 0 ............... 80 .............. 120 ........... Yield/acre, by seeding rate 50,000 80,000 110,000 140,000 Bu. Bu. Bu. Bu. 32 34 39 31 .56 55 59 54 .64 63 64 66 .48 64 63 65 -1T Alabama Agricultural Experiment Station Auburn University Auburn University, Alabama 36849-0520 NON-PROFrr ORG. POSTAGE & FEES PAID PERMIT No. 9 AUBURN. ALA March 1990 10M