Comparison of Statistical Approaches to Determine Nitrogen Needs of Winter Cereals.

Including a double crop, or a second crop within a growing season, in dairy forage rotations in the northeastern United States can provide both economic and environmental benefits, including increased forage production, erosion prevention, enhanced rotation diversity, and improved soil health. Winter cereals such as cereal rye (Secale cereale L.), winter wheat (Triticum aestivum L.) and triticale (x Triticosecale Wittm.) are winter-hardy species that can produce desirable yields in the spring if properly managed. With harvest, these crops remove substantial amounts of nitrogen (N), often requiring N addition at dormancy break in the spring. This study compares the quadratic plateau, exponential, and square root plateau functions using statistical, environmental, and economic criteria to determine the most appropriate model for predicting winter cereal most economic rates of N (MERNs) and associated yields at the MERN. Sixty-three on-farm winter cereal N-rate trials were conducted in New York from 2013-2016. Trials were categorized into 4 groups depending on the nature of their yield response curves followed by model comparison. The quadratic plateau model fitted the data the best, with the lowest AICc values and the highest R² values across sites. It also was the most stable across environmental and economic scenarios, with the lowest absolute change in apparent N recovery (ANR), MERN, and yield at the MERN values between both a high and low price ratio and under- and over-application from the MERN across sites. The quadratic plateau model had MERNs ranging from 47.0-112.3 kg N ha^-1 and yield at MERNs ranging from 2.2-6.9 Mg DM ha^-1.