[Effects of the blended nitrogen fertilizers combined with inhibitors on soil nitrogen pools.]
Yang Bai1, Ming Yang1, Song-Ling Chen1
1College of Land and Environment, Shenyang Agricultural University/Key Laboratory of Arable Land Conservation (Northeast China), Ministry of Agriculture/National Engineering Laboratory for Efficient Utilization of Soil and Fertilizer Resources, Shenyang 110866, China.
Abstract:
Pot experiment with winter wheat was conducted to investigate the effects of blended nitrogen (N) fertilizer (slow-release fertilizer-N:urea-N=1:1) combined with N fertilizer inhibitor NAM on soil ammonium (NH4+-N), nitrate (NO3--N), microbial biomass nitrogen (MBN) and fixed-ammonium (FN) contents. We analyzed dynamic characteristics of soil mineral N, MBN, FN pools under different treatments. There were six treatments, including no N fertilizer (CK), conventional urea (U), blended N fertilizer (MU), MU plus 2.5‰ NAM (MUN1), MU plus 5‰ NAM (MUN2), and MU plus 7.5‰ NAM (MUN3). Our results showed that, compared to that of MU treatment, MUN2 and MUN3 delayed the appearance time of NH4+-N peak. Averaged across the whole wheat growing period, soil mineral N content for NAM treatments decreased by 5.3%-11.7%. From tillering to maturity stage, MBN mineralization and mineralization rates were 38.96 mg·kg-1 and 91.5%, which was higher than that of U treatment; MBN mineralization and mineralization rates for MUN1, MUN2 and MUN3 treatments were 58.73 mg·kg-1, 83.3%, 94.20 mg·kg-1, 94.6%, 104.46 mg·kg-1 and 96.3%, respectively. The FA mineralization release for NAM treatments were higher by 2.83-9.19 mg·kg-1 than that of MU treatment. The results of path analysis showed that NAM addition weakened the direct effect of soil NH4+-N pool on NO3--N pool but enhanced the indirect effects of FN pool on NO3--N pool through affecting NH4+-N pool. The wheat grain yields of the MUN1, MUN2 and MUN3 treatments were significantly higher by 31.6%, 21.5% and 22.9% than that of MU treatment. Nitrogen use efficiencies were increased by 8.1%, 13.5% and 3.1%, respectively. In summary, through double regulation for N release and transformation in soil, NAM delayed the appearance time of soil NH4+-N peak and retarded its transformation into NO3--N, and increased the roles of MBN and FN in supplying N, thereby increased crop yield and N-fertilizer use efficiency.
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