Predicting nitrogen mineralization from dairy manure and broadleaf residue in a semiarid cropping system

Approximately 37% of US milk production occurs in semiarid regions, providing an opportunity to recycle manure nutrients through a variety of cropping systems. Accurate prediction of nitrogen (N) mineralization is critical to determine manure application suitability in intensive irrigated agriculture as many crops in the region have quality parameters that are sensitive to N. Research was conducted in southcentral Idaho to evaluate N mineralization via a buried bag methodology to develop a predictive N-mineralization model. The study was arranged in a randomized complete block design with manure application rates of 18, 36, and 52 Mg center dot ha-1 (dry weight basis) both annually and biennially with synthetic fertilizer and untreated check treatments. The crop rotation included small-grain and broadleaf crops. In the final year of the study, preplant soil organic carbon, total nitrogen, and NO3-N concentrations were positively linearly correlated with manure application rate. Nearly five times as much N was mineralized annually in the 0- to 30-cm depth as compared to the 30- to 60-cm depth. Increased rates of N mineralization for each kilogram of added N occurred in years when residue from broadleaf crops (slope = 0.17) was applied as compared to years with manure only application (slope = 0.07). Stepwise modeling determined that the most predictive model for seasonal N mineralization (R2 = 0.79) included manure N, residue N, soil organic matter, and electrical conductivity. These results allow preplant N mineralization estimation and will prove critical for managing manure in semiarid regions for agronomic, economic, and environmentally sound crop production. Tools are needed to estimate nitrogen (N) mineralization from applications of dairy manure in semiarid irrigated soils.N mineralization was affected by manure application rate, timing, and broadleaf residue N.Average manure N mineralization was 27% and 18% of N applied in the first and second years, respectively, following application.The incorporation of broadleaf residue with manure increased N mineralized to 41% of N applied.The best predictors of N mineralization were soil organic matter, soil electrical conductivity, manure N, and broadleaf N residue.