Study on annual ryegrass-forage maize planting system-nitrogen flux and nitrogen balance in forage maize growth period

Nitrogen requirements, nitrogen transfer, nitrogen use efficiency, nitrogen flux and nitrogen balance of forage corn-Lolium multiflorum planting system (CIS) were analyzed in the representative area of the Chengdu plain. The results showed that dry mass and nitrogen accumulation of forage corn without nitrogen fertilizer were 26 756.82 kg·ha-1 and 317.39 kg·ha-1, respectively, which have no significant difference with fertilizer nitrogen treatment. Nitrogen fertilizer improved the content of nitrogen in soil which affected the biomass of aboveground and root and nitrogen accumulation at different stages of growth period. However, nitrogen fertilizer did not affect the dry mass and nitrogen accumulation at harvest. Soil nitrogen mineralization amount (283.34 kg·ha-1) during growth period and soil mineral nitrogen before planting (139.58 kg·ha-1) in 0-50 cm soil layer area are major nitrogen source of forage corn and the accumulated nitrogen efficient (including aboveground and root) account for 86.53% and 42.50%, respectively. With nitrogen application level (246.30 kg·ha-1), nitrogen absorption efficiency, utilization rate and apparent efficiency of nitrogen fertilizer are 0.49 kg·kg-1, 5.95% and 5.45%, respectively. Soil nitrogen residue and other loss were the main way of nitrogen transfer which accounted for 41.60% and 51.44% of total fertilizer nitrogen. Nitrogen surface runoff, leaching loss and other loss with fertilizer were 13.17 times, 16.67% and 13.17 times of the conditions without fertilizer respectively.