长期施肥对NO3^——N深层积累和土壤剖面中水分分布的影响

研究了旱地农业系统中，长期不同施肥条件下，降水对NO3^--N积累、剖面水分分布以及N有收量、回收率影响及其相互之间的关系。结果表明，降水和氮肥施用量显著影响作物产量。施用氮肥在土壤剖面中造成NO3^--N深层积累，其中NPM处理累积层位于60－120cm，累积量相当于3.0年的年度施肥量（120kg·hm^-2），NP处理累积层位于80－140cm，相当于1.4年施肥量。随着降水的年际间波动，进化论在丰水年、平水年还是干旱年，NPM处理耗水量＞NP处理＞M处理＞P，CK处理。12年不同施肥造成了土壤剖面水分差异。冬小麦播种前不同施肥处理0－100cm水分剖面分布差别不大，NPM处理、NP处理（除丰水年外），土壤100－300cm含水量迅速降低，干旱年M处理缓慢降低，P和CK处理在任何年份变化都不大，氮肥回收率随着降水的波动也呈现相应的高低变化，NPM、NP处理的高低波动幅度最大。NPM、NP处理NO3^-－N累积与N素回收率的降低、土壤水分亏缺基本吻合。由此也反映了水分－作物－施肥三者之间存在的内在制约关系。

Effect of long-term fertilization on NO3--N accumulation and moisture distribution in soil profiles

On the basis of long-term fertilization experiments in gully area of Loess Plateau, the relationships among fertilizations, NO3(-)-N accumulation, and moisture distribution in soil profiles were evaluated. The results showed that fertilization and rainfall significantly influenced the yields. NO3(-)-was accumulated in soil profiles under N and P fertilizers and organic manure(NPM) and N and P fertilizer (NP) treatment. The accumulated NO3-N reached 340 kg.hm-2 in 60-120 cm under NPM treatment, and 220 kg.hm-2 in 80-140 cm under NP treatment, respectively. Soil moisture in 100-300 cm was significantly reduced under NPM treatment. Under NP treatment, it was significantly reduced in dry year and normal year, while under organic manure(M) treatment, it was significantly reduced in dry year. Soil moisture under P and CK treatments was relatively stable in different years. N uptake under NPM and NP treatments was significantly decreased in dry year. It reflected the close relationship among soil moisture, crops, and fertilization.