Potassium Management for Improved Dryland Spring Wheat Grain Yield and Quality.

Like all cereals, wheat requires potassium (K) for optimal growth and development. Adequate K nutrition assists in successful grain fill, results in enhanced grain quality due to improved efficiency of photosynthesis and tolerance to several diseases. Potassium helps to improve nitrogen (N) use efficiency. From the physiological point of view, K is important for root growth and development, and thus, crucial for both nutrient and water uptake. According to conventional nutrient management approach, fertilization is not recommended for a nutrient testing high in the soil because it will likely not result in a yield response. In northern Great Plains region, K is abundant in most agricultural soils, but the majority of soil K is unavailable for plant uptake due to its limited mobility in the soils. High yielding crops are known to remove large quantities of K and can lead to gradual K depletion even from the soils high in K. Research indicated that in Montana frequent K responses could be expected in dryland wheat, even when soil K levels are considered very high. This is a proposal to carry out a comprehensive study that will help to better understand the importance of K nutrition for dryland hard red spring wheat from the point of view of fine root growth, N uptake and grain protein production as well as water uptake and utilization. The specific objectives are: 1) To evaluate root characteristics and distribution on N uptake, as influenced by K fertilization, and 2) To determine optimum K fertilizer rate for improved grain yield and increased grain protein content in dryland hard red spring wheat. Two experimental sites will be established in Montana in the cooperating wheat producers’ fields. Fertilizer N will be applied as urea (46- 0-0) with the seed at planting at 7 rates ranging from 0 to 270 lb N/ac. Potassium will be applied as potassium chloride (KCl) (0-0-60) at 3 rates – 10, 20, and 30 lb K2O/ac side-banded at planting to ensure K supply early in the growing season. Phosphorus and other plant nutrients will be, if needed, applied according to current Montana State University guidelines for spring wheat. At 3 growth stages - tillering, anthesis, and maturity - plant height will be measured, and whole plant biomass samples will be collected. Complete analysis of root samples utilizing “WinRHIZO” system will be carried out to accurately determine root length, surface area, and diameter, and root distribution. The above ground biomass weight will be determined; the subsamples will be analyzed for N and K concentration. At harvest, for each plot grain yield and grain test weight will be recorded, and grain samples will be collected and send for comprehensive quality analysis, including total N, grain protein content, oil and starch. Statistical analysis will be carried out to evaluate the effect of K application rate on root length, surface area, root length density, root weight density and specific root length. Furthermore, the effect of K application on N uptake, grain yield, and grain quality characteristics such as test weight, protein content, oil and starch content of spring wheat will be evaluated. This study will help us to better understand the importance of K nutrition and to develop K recommendations for optimized N and water uptake and utilization due to improved root growth.