化肥减施对小麦-高粱系统土壤团聚体分布及其稳定性的影响

当前我国农户的肥料施用量已远超全球平均水平,所造成的土壤退化问题十分严重,因此控制我国肥料施用量已经迫在眉睫。研究肥料减施对土壤团聚体分布及其稳定性的影响,设置农户常规用量（CK）、常规用量的75%（UA_75%）、常规用量的50%（UA_50%）、常规用量的25%（UA_25%）4个处理,通过对土壤团聚体分布及其稳定性分析得出：短期化肥减施对机械稳定性团聚体分布几乎无影响,但显著增加了水稳性大团聚体（粒径>0.25mm）的数量。短期化肥减施对机械稳定性团聚体的平均重量直径（MWD）、几何平均直径（GMD）和分形维数（D）均无显著影响。UA_25%和 UA_50%处理增加了水稳性团聚体的MWD和GMD,降低了D值和团聚体破坏率（PAD）,提高了稳定率（WSAR）。肥料减施显著降低了冬小麦产量,而UA_50%和UA_75%处理对夏高粱产量的影响并不明显。综上所述,UA_50%处理能提高小麦-高粱系统的土壤团聚体稳定性、保证夏高粱产量,但肥料减施显著降低了冬小麦产量。

Effects of Fertilizer Reduction on Distribution and Stability of Soil Aggregates Based on Wheat-Sorghum System

The current amount of fertilizer application in China are far more than global average level, which causes serious soil degradation problem. Thus controlling the amount of fertilizer is imminent. In this experiment, the soil aggregates distribution and stability were studied by fertilizer reduction. Four treatments including conventional dosage (CK), 75% of conventional dosage (UA_75%), 50% of conventional dosage (UA_50%), and 25% of conventional dosage (UA_25%)were set up in the experiment. The results showed that the effect of fertilizer reduction on the mechanical stability aggregates distribution was not obviously different, but the number of water stability large aggregates was significantly increased based on analysis the distribution and stability of soil aggregates. Fertilizer reduction had no significant effects on the mean weight diameter (MWD), geometric mean diameter (GMD) and fractal dimension (D) values of the mechanical stability aggregates. UA_25% and UA_50% increased the MWD and GMD values of the water stability aggregates, decreased the D value, declined the percentage of aggregate destruction (PAD), and improved the water stable aggregates stability rate (WSAR) value. Fertilizer reduction significantly reduced winter wheat yield, while UA_50% and UA_75% treatments had no significant effects on summer sorghum production. In summary, UA_50% treatment can improve the soil aggregates stability on two seasons crops and ensure the yield of summer sorghum, however, fertilizer reduction significantly reduced winter wheat yield.