成都平原农业废弃物施用下稻田田面水氮磷动态变化特征

为合理利用农业废弃物,设置不同量的废弃物还田处理,以期通过研究稻田田面水中氮素和磷素的动态变化探明废弃物施用下面源污染风险。结果表明:总氮(TN)、可溶性总氮(DTN)、铵态氮(NH+4-N)以及硝态氮(NO-3-N)在各施肥处理下均表现为先升后降的趋势,施肥后2~3 d达到峰值,之后迅速下降;各处理下各形态氮含量在施肥后21 d内差异趋同。总磷(TP)、可溶性总磷(DTP)在施肥后1 d达最大,之后迅速下降,猪粪施用处理的田面水TP、DTP含量在施肥后5~7 d明显回升。与纯化肥相比,加施全量麦秆对田面水中各形态氮、磷含量及分配无显著影响;高量猪粪施用会显著降低田面水NH+4-N含量,降低氨挥发潜能,显著提高各形态磷含量,延长磷素流失风险期,增加磷素流失风险;废弃物施用对水稻产量及糙米磷含量无显著影响。综合考虑废弃物施用下的环境风险与粮食生产,成都平原麦秆全量还田模式下水稻季每667 m2田的猪粪承载量不宜超过3头猪0.5年的排泄量。

Dynamics of Nitrogen and Phosphorus in Paddy Field Water Under Agricultural Residue Applications in Chengdu Plain

Applying agricultural residues has improved soil fertility and thus crop yields. However, little information is available about the risk of nitrogen and phosphorus pollution caused by agricultural residue applications in paddy fields. In this study, an experiment with three agricultural residue application rates was conducted to study the dynamics of nitrogen and phosphorus in paddy field water. The concentrations of total N(TN), dissolved total N(DTN), ammonium(NH₄⁺-N) and nitrate(NO₃^--N) under different treatments all reached their peak values 2~3 days after applying residues, and then decreased rapidly. The concentrations of different forms of N showed no significant difference between different treatments 21 days after treatments. The concentrations of total P(TP) and dissolved P(DTP) under different treatments attained their peak values on the 1st day after treatments, and then declined. However, TP and DTP significantly increased 5~7 days after swine manure treatment. In comparison with chemical fertilizer, wheat straw did not have significant effects on the concentrations of different N and P forms. High rates of swine manure significantly decreased ammonium concentrations and ammonia volatilization potential in paddy field water, but significantly enhanced P loss. The applications of agricultural residues had no significant effects on rice yields and P contents in brown rices. Considering food production and environmental risks resulted from applying agricultural residues in Chengdu Plain, we suggest that under the whole wheat straw returning the paddy field carrying capacity for swine manure per 667 m² during rice growing season should be less than the amount of excretion by three swines during half year.