Wheat Variety Performance and Production Practices in Louisiana
By Boyd Padgett, Stephen Harrison, Noah DeWitt, Trey Price
LSU AgCenter
Article Highlights:
· Variety selection considerations (vernalization/heading date, disease resistance, yield, test weight)
· Crop management (planting date, seeding rates, fertilization strategies)
To access the Variety Performance Trial publications, go to the following website:
Variety selection:
Choice of varieties for planting is a crucial management decision that sets the stage for yield potential and input costs. While grain yield is the most important factor, test weight, disease resistance, and heading date are important considerations as they also impact economic return.
Test weight is important because low test weight results in dockage at the elevator. Heading day is a function of cold requirement (vernalization) and day length (photoperiod) response that determines when a variety heads out. Some varieties head very late or not at all in south Louisiana due to a long vernalization requirement or photoperiod response, while those same varieties may perform better in north Louisiana or Arkansas. Varieties that fully vernalize but head out late due to long photoperiod requirement perform poorly in south Louisiana due to grain fill during hot weather. By contrast, early heading varieties may yield poorly in north Louisiana due to late spring freeze damage. Vernalization and photoperiod response are the primary reasons for dividing Louisiana into North and South regions.
Early-heading and maturing varieties permit earlier harvest and more timely planting in a double-crop system, while later-heading varieties guard against damage from a late spring freeze and can be planted earlier in north Louisiana. Early-heading varieties should be planted in the second half of the recommended planting window to reduce the likelihood of spring freeze damage. Lodging resistance helps guard against reduction in test weight and yield loss that results when near-mature heads come in contact with the ground.
Disease resistance protects yield and reduces input costs. Disease susceptibility is very important in terms of yield and profitability. Reactions for naturally-occurring diseases are also listed for each variety in Variety Performance Trial publications. There are no varieties fully resistant to FHB, but some have high to moderately high to moderate levels of resistance. It should be noted that varieties less susceptible to disease may not always be the highest yielding, especially if disease pressure is not present. However, in high disease pressure situations, these varieties produce higher yields than susceptible varieties and enhance profitability by saving the costs of fungicide applications.
Crop management:
Planting dates for Louisiana wheat depend on location and variety. For southern and central Louisiana, optimum planting dates range from November 1 through November 30. The optimum planting for northern Louisiana is slightly earlier, ranging from October 15 through November 15. Early-heading varieties should generally be planted after the mid-date, while late-heading varieties can be pushed a little on the early side of the planting window. The weather in north Louisiana is cooler in the fall and early winter, which slows growth and prevents excess winter growth. It is important that the wheat crop be well-established and fully tillered before the coldest part of the winter. Additionally, because of the cooler conditions, the threat from fall pests (Hessian fly, army worms and rust) is decreased earlier in the fall compared to south and central Louisiana. While these dates are the optimum planting window averaged over years, the timing will vary in some years depending on weather patterns. Additionally, if wheat cannot be planted within these optimum windows, planting later than the optimum window is usually better than planting too early. Early planting can result in greater insect and fall rust establishment and also makes plants more prone to spring freeze injury due to excessive fall growth and development. Planting too late (more than 14 days after the optimum window) can result in significant yield loss due to slow emergence, poor stands from seed rotting and a decreased tillering period, which results in fewer and smaller heads.
Wheat can be planted by broadcasting seed and incorporation into the soil; however, it is preferred that the seed be drilled. Drilling the seed increases the uniformity of depth and uniform emergence. Use recommended planting rates for drilled wheat (60 to 90 lb/A) or broadcast wheat (90-120 lb/A) of quality seed into a good seedbed with adequate moisture. This higher seeding rate should be used under conditions in which good germination or emergence is not expected, as occurs with late-planted wheat or heavy, wet soils. Late-planted seed should be planted at a higher seeding rate using a drill to ensure rapid, adequate and uniform emergence.
Good surface drainage is critical to successful wheat production. Saturated fields lead to diseases such as root rots and downy mildew, reduced tillering and vegetative growth, and decreased root development and nutrient utilization. Yields in wheat fields suffering from waterlogging stress are greatly reduced. Fields with marginal drainage should be ditched to ensure that water stands for a minimum time after heavy rainfall.
Nitrogen (N) fertilization of wheat can be a challenging aspect of production. Total N application should normally range from 90 to 120 pounds per acre, but this will vary depending on soil type and rainfall after applications. Timing of N application depends on several factors. The wheat crop needs adequate N in the fall and early winter to establish ground cover and properly tiller; however, excessive levels of fall N can result in rank growth and increased lodging potential, as well as a higher probability of spring freeze damage from early heading. If the wheat crop is following soybeans, soil residual or mineralized N should be adequate for fall growth, and no pre-plant N is needed. However, if the wheat crop follows corn, sorghum, rice or cotton, the application of 15 to 20 pounds of N per acre would typically be beneficial. Where the wheat crop is planted later than optimum, additional N may be necessary to ensure adequate fall growth prior to winter conditions. If the wheat crop did not receive a fall application and appears to be suffering from N deficiency in January, the initial top dress N application can be made early to promote additional tillering. Early spring is when the majority of N for the wheat crop should be applied. There is no universal rule on how early spring N should be applied. Each field should be evaluated based on tillering, stage of development, environmental conditions and crop color. A crop that has good growth and good color should not need N fertilization prior to erect leaf sheath (Feekes 5), usually sometime in February. However, first spring fertilizer application should be applied prior to first node (Feekes 6) to ensure optimum head development, tiller retention and head size. Crop N stress around jointing (Feekes 6) will result in yield losses. Any additional N applied following flag leaf typically contributes very little to crop yield. Splitting topdress N into two or three applications is common in Louisiana production systems due to the increased risk of N losses often associated with heavy rainfall and our long growing season. Splitting N typically occurs by applying fertilizer N at or just prior to jointing with a second application occurring 14 to 28 days later. About 50 percent of the topdress N is normally applied with the first split, but this may be decreased if the first split is put out early and plants are not well enough developed to take up that much N.
Phosphorus, K, and micronutrients should be applied in the fall based on soil test reports. All fertilizers applied as well as lime should be incorporated into the soil prior to planting. Required lime should be applied as soon as possible because it takes time for the lime to begin to neutralize the acidity of most soils. The application of sulfur is a growing concern in Louisiana production systems, with increasing deficiencies appearing every year. Oftentimes, early spring sulfur (S) deficiencies are mistaken for N deficiencies and additional S is not applied. Because sulfur is mobile, similar to N, the application solely in the fall may not be adequate. Supplemental applications of S with spring N applications are often warranted.
For further questions or comments contact:
Steve Harrison, Small Grain Breeder, sharrison@agcenter.lsu.edu
Noah DeWitt, Small Grain Breeder, ndewitt@agcenter.lsu.edu
Boyd Padgett, Wheat Extension Specialist/Plant Pathologist, bpadgett@agcenter.lsu.edu
Trey Price, Extension Research Plant Pathologist, pprice@agcenter.lsu.edu