Intermediate Wheatgrass Nitrogen Dynamics: Nitrate Leaching Prevention and Nitrogen Supply via Legume Intercrops

Abstract

We compared soil and soil water nitrate concentrations, root biomass, and yield in intermediate wheatgrass (IWG; Thinopyrum intermedium) and a corn-soybean rotation over three years. Nitrate was 77-96% lower under IWG than the annual system, while root biomass was higher. IWG grain yields were 854, 434, and 222 kg ha-1 for Years 1-3 and biomass averaged 4.65 Mg ha-1 yr-1. IWG effectively reduces soil solution NO3--N concentrations even on sandy soils, supporting its potential for broader adoption on vulnerable land. We also assessed grain and biomass yield and N dynamics in response to mineral fertilizer and six legume intercrops. Treatments affected N dynamics and IWG biomass but not grain yields. N transfer rates ranged from 0 to 27% but legume biomass was negatively associated with IWG grain yield, suggesting competition in addition to nitrogen supply. Overall, alfalfa, red clover, and birdsfoot trefoil were among the best options for intercrops.