不同有机替代方式下稻田土壤胶体磷流失潜力研究

土壤胶体因具有较大的比表面积及较强的吸附与迁移能力，其所携带的磷（胶体磷）已成为农田磷流失过程中的重要形态。为评估不同有机替代方式下稻田土壤胶体磷（P_coll）的活性和流失潜力，本文依托两种有机肥部分替代化肥（控氮控磷与控氮不控磷）方式下稻麦轮作长期定位试验，探讨了P_coll含量变化、流失风险及其与不同土壤活性磷组分之间的关系。控氮控磷试验（4 a）设有3个处理：不施磷肥（CK）、单施化肥（CF）、猪粪有机肥替代30%化学磷肥（OF）；控氮不控磷试验（24 a）设有3个处理：不施肥（CK）、单施化肥（CF）、猪粪有机肥替代40%化学氮肥（OF）。结果表明：在控氮控磷条件下，有机替代处理较单施化肥处理，土壤有机碳（SOC）、P_coll含量及其流失潜力（LPP）均无显著性差异，胶体钼蓝反应磷占比（R_MRP，MRP_coll/P_coll）显著降低1.76%（P < 0.05）。在控氮不控磷条件下，有机替代处理的土壤P_coll和SOC含量分别为13.08 mg/kg和20.19 g/kg，显著高于单施化肥78%和212.6%（P < 0.05）；较单施化肥，土壤LPP和R_MRP分别显著升高了1.89%和16.05%（P < 0.05）。两种有机替代方式下土壤P_coll与土壤全磷（TP）、真溶解态磷（TSP）、Olsen-P、CaCl₂-P等均呈极显著正相关（P < 0.01）；与土壤有机碳（SOC）在控氮不控磷条件下呈极显著正相关（P < 0.01），在控氮控磷条件下无显著相关性。以上结果表明，较控氮控磷有机替代方式，长期仅控氮的有机肥施用显著增加了土壤有机碳、胶体磷和不同活性磷组分含量，磷流失风险升高。因此，有机肥部分替代化肥养分等量控制是改善农田磷流失可行的施肥方式。

Loss Potential of Colloidal Phosphorus in Paddy Soil Under Different Organic Substitution Fertilizations

Phosphorus (P) loss from farmland is one of the important sources of agricultural non-point source pollution, and colloidal P (P_coll) is an important form due to its large specific surface area, strong adsorption and migration capacity. In order to evaluate the activity and loss potential of P_coll in paddy soil under different organic substitution methods, this study relied on a long-term experiment of rice-wheat rotation under two partial substitution methods of organic fertilizers (N and P fertilizer application control and N fertilizer application control only) to explore the changes in soil P_coll content and its loss risk, as well as its relationship with different P components and soil chemical properties. The treatments of N and P fertilizer application control (4 a) included no P fertilizer (CK), chemical fertilizer (CF), and pig manure instead of 30% chemical P fertilizer (OF); the treatments of control N fertilizer application only (24 a) included no fertilizer (CK), chemical fertilizer (CF), and pig manure instead of 40% chemical N fertilizer (OF). The results showed that, for the fertilization of N and P control, there were no significant differences in soil organic carbon (SOC), P_coll content and colloidal phosphorus loss potential (LPP) between the organic substitution treatment and the chemical fertilizer treatment. The proportion of soil MRP_coll (R_MRP, MRP_coll/TP_coll) was significantly (P<0.05) reduced by 1.76% than that of the chemical fertilizer treatment. For the fertilization of N control only, soil P_coll and SOC content of organic substitution treatment were 13.08 mg/kg and 20.19 g/kg, respectively, which were significantly (P<0.05) increased by 78% and 212.6% compared with the application of chemical fertilizer alone; soil LPP and R_MRP were significantly (P<0.05) increased by 1.89% and 16.05%, respectively. Soil P_coll was positively (P<0.01) correlated with soil TP, TSP, Olsen-P and CaCl₂-P under the two organic substitution methods. Soil P_coll had no significant correlation with SOC under the fertilization of N and P control, however showed a significant positive correlation (P<0.01) under the fertilization of N control only. Compared with the treatments of N and P fertilizer application control, the long-term application of organic fertilizer with only N control significantly increased the content of SOC, P_coll and different active P components in the soil, thus may induce the risk of phosphorus loss. Therefore, equaling nutrient application is a feasible organic substitution fertilization to reduce the P loss in farmland.