Nitrogen and fungicide effects on winter wheat produced in the Louisiana Gulf Coast region

Management decisions affecting wheat (Triticum aestivum L.) yield include nitrogen (N) fertility rate, cultivar selection, and fungicide application. Since these cultural practices may interact with each other and the environment, often times affecting grain yield, test weight, and disease development, they need to be better defined for wheat production in for the Gulf Coast region. Field experiments were conducted to evaluate the effect of N rate, fungicide, and cultivar on grain yield, test weight, and disease development. Three N rates (67, 101, and 134 kg#lbha^‐1), two fungicide treatments (no‐fungicide control and fungicide), and four high‐yielding wheat cultivars with different levels of resistance to leaf rust (Puccinia recondite Rob. ex f. sp. tritici) were evaluated in 12 Louisiana field environments. Environment and interaction between environment and N rate, fungicide, and cultivar were significant for grain yield, leaf rust ratings, and test weight. Grain yield response to N rate was linear in five environments and quadratic in five environments. Although there was little evidence of a N x fungicide interaction for grain yield, increasing N rates increased leaf rust severity. Grain yields were increased by fungicide application in only four of twelve environments with a significant cultivar x fungicide interaction for grain yield. Grain yield increase from foliar fungicides was related to leaf rust severity and resistance of cultivars to leaf rust. Test weight was increased due to N in three environments and decreased in two environments. Test weight increased with fungicide application and varied among cultivars. The findings indicate that 101 kg N ha is probably adequate for maximum yield in most years. Although the higher N rates may increase yield in some years, disease pressure and the need for fungicides may also be increased.