Nitrogen fertilizer requirements of silage maize and sorghum–sudangrass grown after 4 years of alfalfa production in a semi‐arid environment

Background This 2‐year study sought to determine the influence of N application rates following alfalfa termination on biomass production and quality of the succeeding crops of maize ( Zea mays L.) and sorghum–sudangrass ( Sorghum bicolor (L.) Moench × Sorghum sudanense Piper) and quantify short‐term changes in soil total N (TN) under the different systems. Methods Treatments were two silage maize hybrids (“LG5470” and “NK0388”) and two sorghum–sudangrass hybrids (“Super sugar” and “Sweet six”) for a total of four entries and three N application rates (0, 80, and 160 kg N ha −1 ) in a 4 × 3 factorial in a randomized complete block design with four replications each. Results In the first year following termination of a 4‐year alfalfa stand, no additional N was required for maize (22.9 Mg DM ha −1 , SE = 1.2) and sorghum–sudangrass (19.3 Mg DM ha −1 , SE = 1.2) biomass production. Total digestible nutrients (TDNs) of herbage biomass differed only in the second year, and TDNs in Year 2 were greater for the 160 kg N ha −1 rate (675.2 g kg −1 DM, SEM = 9.6) compared to the 0 kg N ha −1 rate (638.2 g kg −1 DM, SEM = 9.6). Conclusions The results from this study offer producers the opportunity to integrate a cropping system that will lead to significant N input cost savings, provide a reliable source of feed for the ruminant livestock industry, and promote long‐term feed crop sustainability in semi‐arid environments like Nevada and other similar regions worldwide.