Hard Red Winter and Hard Red Spring Wheat (Triticum aestivum L.) Response to Fertilizer N Rates and Application Method

Nitrogen (N) fertilization has contributed greatly to improving the grain yield and protein content of wheat (Triticum aestivum L.). Crops require more N than any of the other essential element derived from the soil. Although other nutrients are essential for crop production, N availability frequently determines the level of wheat yields. Nitrogen is also costly because it is required in large quantities. Increasing the efficiency of fertilizer N use by wheat should be the goal of any wheat producer to maintain a reasonable profit margin. Environmental issues should also be considered. Potential contamination of ground water from nitrate leaching dictates that the applied N fertilizer application remain within reach of the plant roots. Efficient use of N is also important in light of energy concerns. The most logical approach to increasing N fertilizer efficiency, and hence lessening environmental impacts of excess N, is to match applications closely to the crop N uptake demand throughout the growing season. Theoretically, this could be accomplished with slow release N fertilizers, but their use may not be practical because they are expensive. Alternatively, fertilizer N can be supplied in multiple applications to match crop needs. However, each application incurs additional operating expenses. Efficient, profitable wheat production requires an adequate supply of N to meet plant demands. While the application rate is certainly important, application method is equally important. Wheat removes large amounts of nitrogen from the soil during the early stages of growth and retains it for translocation to the grain later on in the growing season. The greatest N demand by wheat is during the rapid growth stages between jointing and head emergence. Field experiments comparing the relative efficiency of preplant and split applications of fertilizer N to winter and spring wheat have produced mixed results. Information is needed concerning the influence of preplant vs. split N fertilization for efficient use of fertilizer· on hard red winter and hard red spring wheat in South Dakota. The specific objectives of this research were: (1) To determine the effects of N fertilizer rates on grain yield and grain protein of hard red winter and hard red spring wheat. (2) To compare the efficiency of preplant vs. split N fertilizer application on grain yield and grain protein of hard red winter and hard red spring wheat