Evaluation of Urea-Potassium Chloride Blend and Residue Management in Spring Wheat.

Hard red spring wheat in the northern Great Plains region is predominantly grown in no-till dryland cropping systems. With the majority of Montana’s soils in crop production having a high pH, reducing ammonia loss from urea applied to agricultural fields continues to be one of the most-discussed topics among growers, crop consultants and researchers. Higher nitrogen (N) losses have been reported under no-till. A number of approaches have been investigated in an attempt to find a cost-effective and efficient method of reducing N losses. Crop residue left on the broadcasted in the no-till cropping systems affects soil temperature and moisture content, which affects both N mineralization and the efficiency of N fertilizer use. Urea is an N fertilizer popular among crop growers due to its’ high N concentration, relatively low cost and ease of handling. Numerous studies have shown that urea-N may be susceptible to severe losses due to the volatilization of ammonia produced during urea hydrolysis. Ammonia volatilization refers to the loss of ammonia (NH3) from the soil as a gas. It appears that residue management and addition of potassium chloride to urea may reduce N volatilization and increase N use efficiency. Removing some residue from the fields, can help in establishing a more uniform plant stand - one of the key factors affecting wheat grain yield. Residue management could assist in improving fertilizer-soil contact and encourage N uptake and minimize the risk of fertilizer being trapped in the residue. Recent ammonia volatilization experiments found that N loss from broadcasted-applied urea can be reduced by almost 25%, and NUE can be improved by almost 25% when urea is amended with potassium chloride (KCl). Besides inhibiting ammonia volatilization and increasing N recovery of urea fertilizer, essential plant nutrient – K - is supplied to the crop. According to conventional nutrient management approach, K 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. There is a need to develop more efficient soil fertility and nutrient management strategies in order to maximize wheat grain yields and increase grain protein levels. This proposal is put forward to investigate the potential of urea-KCL blend utilization and residue management for improving N use efficiency in spring wheat dryland no-till conditions. The study will compare urea vs urea- potassium chloride blend applied to achieve a total target rate of 120 and 240 lb N/ac. Since incorporation of N fertilizers is one of the practices most commonly used to avoid/minimize N loss, we will compare two fertilizer placements: broadcasted-applied fertilizers vs side-banded fertilizers. Additionally, two superimposed residue management treatments will be evaluated – undisturbed broadcasted residue and removed broadcasted residue. We expect to develop grower recommendations regarding utilization of KCl as urea amendment and residue management for spring wheat production.