Adaptive Wheat Management: Increasing Wheat Yield by Adjusting for Weather Conditions
Growing environments for wheat are highly variable, with tremendous changes in temperature and rainfall during the growing season from one season to the next. One season the wheat may experience warm temperatures and little rainfall; the next season may have very cold temperatures with excessive moisture. These extreme conditions can occur at different times within a single growing season. Managing wheat for optimal yield in these environments is extremely difficult. Using a formalistic approach (planting on the same date with the same variety, seeding rate, and fertility practices) often results in less than optimal yield and lower economic returns. Adaptive management is a system that adapts management practices to current and predicted environmental conditions. It is based on an understanding of the key environmental factors and growth periods that influence wheat growth, yield components, and final yield. Using an adaptive management approach, a grower adjusts practices such as variety selection, seeding rate, planting date, amounts and timing of fertilizer applied, and the use of special practices such as growth regulators or pesticides to optimize yield based on the environmental conditions of a given growing season.
Growers interested in using an adaptive management system should develop a plan based on anticipated weather conditions, frequent analysis of crop growth, and updates on growth stage (tiller and growth targets that need to be achieved by a given date). The grower should follow these steps:
- Collect all information on anticipated temperature and rainfall conditions for the coming fall (via NOAA) during late August through September. Use the NAO index, weather forecasts, or other pertinent information to determine what temperature conditions are most likely to occur in the fall and early winter. These temperatures will determine how many growing degree days the crop will experience.
- Identify the optimal planting date. Once you have identified the most likely temperature profile for fall and winter, select the range of planting dates to consider. Don’t forget to adjust for soil conditions under no-till or high residue situations; such conditions require more heat units to achieve growth and development.
- Anticipate jointing time by selecting the proper maturity group for your variety based on targeted planting dates.
- Adjust anticipated seeding rate and nitrogen use based on current weather conditions as planting time approaches. If the weather is warmer than anticipated, reduce seeding rates and withhold nitrogen at planting. If weather is cooler than anticipated, increase seeding rate and apply nitrogen at planting or closely after planting. Don’t forget to adjust practices based on pest pressure. If warmer than normal, consider whether Hessian fly or diseases such as barley yellow dwarf may present problems.
- Scout your crop to see how it is approaching the goal of two tillers by Dec. 25. If the weather has turned colder or wetter than anticipated, use split-nitrogen applications whenever temperatures are above 40ºF to help stimulate growth. If the weather has turned warmer or drier than anticipated, withhold your nitrogen application until just before jointing or consider the use of a growth regulator to limit the number of excess tillers produced and to ensure that nitrogen is available through the flowering period.
- Monitor the crop following cold weather or heavy rainfall events. Plants should recover their green color quickly. If they do not recover quickly, that is a sign of poor root development. Consider applying nitrogen in late January or early February (whenever temperatures start to warm up) to improve root growth and development. Watch for other sources of stress that may limit the plants’ response to warm temperatures and, if possible, take corrective measures.
- Anticipate jointing between March 15 and March 25 if your planting date and variety maturity class were on target.
- Monitor the crop for disease and growth after flowering: this is the time to protect yield potential. If the crop is failing, consider whether additional expenses, such as applying a fungicide or late-season insecticide, are justified. After flowering if warm, dry weather is experienced in May, growers with irrigation capacity should consider at least one application of water to keep canopy temperatures below 86ºF.
Successful wheat management in today’s economic environment requires the wheat grower to manage the temperature environment of the crop. The adaptive wheat management system is a way for wheat growers to do just that. Following an adaptive system, growers can maximize yield while at the same time not wasting resources on a crop that has little yield potential. A successful adaptive management system can lower costs by helping prevent more than one application of nitrogen in many cases; by staging wheat development during periods where pest or disease pressure is lower; and by making it possible for the crop to resist pests.