长期施用有机肥和过磷酸钙对潮土有效磷积累与淋溶的影响

利用20年定位试验研究了施用化肥和有机肥对潮土耕层土壤有效磷（Olsen-P）含量与作物产量的关系及土壤Olsen-P积累和垂直移动规律的影响.结果表明：土壤Olsen-P含量在10～40 mg·kg^-1能保证小麦、玉米有较高的产量，土壤Olsen-P含量大于40 mg·kg^-1发生显著淋溶，轻壤质潮土Olsen-P发生淋溶的阈值为40 mg·kg^-1.连续施用化肥（NPK）和秸秆还田处理（SNPK）施磷量在77～90 kg·hm^-2，平均每100 kg P·hm^-2使耕层土壤Olsen-P提高0.63～0.72 mg·kg^-1，每年提高0.49～0.65 mg·kg^-1，达到淋失阈值需要45～60年.有机肥与化肥结合（MNPK、MNPK2和1.5 MNPK），年施磷量为210 kg·hm^-2时，土壤Olsen-P（Y）与施肥年度（x）的关系为：Y_{1.5 MNPK}=4.506x+6.4464 (R²=0.8862)，平均每年增加4.5 mg·kg^-1，连续施用8年可使耕层土壤Olsen-P达到淋失阈值；年施磷量为125和140 kg·hm^-2时，土壤Olsen-P与施肥年度的关系为：Y_MNPK2=2.4765x+13.563 (R²=0.9307)和Y_MNPK=3.1097x+6.9615 (R²=0.8562)，平均每年增加2.47和3.1 mg·kg^-1，连续施用11年可使耕层土壤Olsen-P达到淋失阈值.有机无机肥结合处理土壤Olsen-P积累速度是化肥处理的3.5倍，过量施用有机肥增加了土壤Olsen-P的积累和淋失.

Effects of long-term application of organic fertilizer and superphosphate on accumulation and leaching of Olsen-P in Fluvo-aquic soil

Based on a 20-year experiment of fertilization with organic and chemical fertilizers on a Fluvo-aquic soil under wheat-corn cropping system, this paper studied the relationships between Olsen-P concentration in plough layer and crop yields as well as the accumulation and vertical translocation of Olsen-P in soil profile. The results showed that when the Olsen-P concentration in plough layer maintained at 10-40 mg·kg^-1, the grain yields of wheat and corn were higher, whereas when the concentration of Olsen-P in plough layer was higher than 40 mg·kg^-1, it started to leach, which meant that in light loam Fluvo-aquic soil, the threshold value for P leaching might be 40 mg·kg^-1. In the treatments of chemical fertilization (NPK) and corn straw returning (SNPK) with the P application rate of  77-90 kg·hm^-2, the Olsen-P concentration in plough layer was increased by 0.63-0.72 mg·kg^-1 per 100 kg·hm^-2 of applied P, with an annual increment of 0.49-0.65 mg·kg^-1 and needed 45-60 years for reaching the threshold value for P leaching. In the treatments of chemical fertilization combined with manure application (MNPK, MNPK2, and 1.5MNPK),  the formula of Olsen-P accumulation in 0-20 cm soil layer were Y_MNPK=3.1097x+6.9615 (R²=0.8562), Y_MNPK2=2.4765x+13.563(R²=0.9307), and Y_1.5MNPK=4.506x+6.4464 (R²=0.8862). It might take 8 years to reach the threshold value for Olsen-P leaching when the P application rate in treatment 1.5MNPK was 210 kg·hm^-2, 11 years when the P application rate in treatments MNPK2 and MNPK was 125 and 140 kg·hm^-2. Organic fertilization combined with chemical fertilization increased the Olsen-P accumulation rate being 2.5 times higher than chemical fertilization. Excessive application of organic fertilizer could increase the accumulation and leaching of Olsen-P in soil profile.