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

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

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10～40mg·kg-1能保证小麦、玉米有较高的产量,土壤Olsen-P含量大于40mg·kg-1发生显著淋溶,轻壤质潮土Olsen-P发生淋溶的阈值为40mg·kg-1.连续施用化肥(NPK)和秸秆还田处理(SNPK)施磷量在77～90kg.hm-2,平均每100kgP.hm-2使耕层土壤Olsen-P提高0.63～0.72mg·kg-1,每年提高0.49～0.65mg·kg-1,达到淋失阈值需要45～60年.有机肥与化肥结合(MNPK、MNPK2和1.5MNPK),年施磷量为210kg.hm-2时,土壤Olsen-P(Y)与施肥年度(x)的关系为:Y1.5MNPK=4.506x+6.4464(R2=0.8862),平均每年增加4.5mg·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140kg.hm-2时,土壤Olsen-P与施肥年度的关系为:YMNPK2=2.4765x+13.563(R2=0.9307)和YMNPK=3.1097x+6.9615(R2=0.8562),平均每年增加2.47和3.1mg·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.

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 YMNPK=3.1097x＋6.9615 （R2=0.8562）,YMNPK2=2.4765x＋13.563（R2=0.9307）,and Y1.5MNPK=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.