Changes in the inorganic nitrogen content of the soil solution with rice straw retention in northeast China

Research the effects of straw retention (SRT) and nitrogen fertilizer on nitrogen concentration in soil solution and yield during the growth period of rice. This study was conducted to explore the variation of nitrogen concentration in soil solution by continuous location plot experiment, pot experiment, and laboratory culture experiment. The results showed that the ammonium N (N114'-N), nitrate N (NO3-N), and mineral N contents of the soil solution gradually decreased with increasing rice growth. Moreover, the N contents of the soil solution gradually increased with an increasing rate of N fertilizer application; however, increasing the rate of N fertilizer application did not change the effect of SRT on the N content in the soil solution. Comparing SRT with straw removal (SRM), the NH4.-N in the soil solution increased by 29.08% (0.17 mg Li over the rice-growing period; by contrast, the NO,-N and mineral N contents decreased by 8.90% (0.47 mg L-1) and 3.02% (0.29 mg I:1), respectively. In the black soil region of Northeast China, SRT reduced the nitrate concentration in the soil solution, and the N contents mineral was lower than that of the straw. Under production conditions, SRT has the trend of increasing rice yield.