Influence of Phosphorus Fertilizer Application on Available Phosphorus and Easy-loss Phosphorus Content in Red Soil

[Objective] This study was to investigate the influence of phosphorus （P） fertilizer application on available P and easy-loss P content in red soil under aerobic incubating condition, with the aim to provide theoretical basis for the management of elemental P and evaluation of elemental P loss potential. [Method] Totally six treat- ments were set to the soil samples. The Olsen-P, Bray-1 P and CaCl2-P contents of each soil sample were measured after indoor aerobic incubation. [Result] In the red soil of different P fertilizer application rates, the Olsen-P content decreased with the increasing of incubation time, while the content of Bray-1 P increased and CaCI2-P content was first increased then decreased. CaCl2-P content was linear correlated with Olsen-P content and Bray-1 P content. About 62% P fertilizers were transformed into Bray-1 P pool, and 14% into Olsen-P pool, but only 0.12% transformed into CaCl2-P pool. [Conclusion] There is little risk of P loss caused by P fertilizer application under aerobic condition, but it would increase with the increasing application dose, and the most serious time is the primeval period after P fertilizer application.

Effect of Lanthanum on Nitrification, Phosphorus Transformation and Phenol Decomposition in Red Soil

The effect of La on nitrification, P transformation and phenol decomposition in red soil was studied by incubation and pot culture experiments. La at low concentration has stimulative effect on soil nitrification and P transformation while its high concentration has inhibitory effects, and the inhibition is strengthened with increasing concentration of La. La has strongly inhibitory effect on soil phenol decomposition and the inhibition is strengthened with increasing concentration of La. When the incubation time is prolonged, the inhibitory effect of La on soil nitrification and phenol decomposition tends to decrease.

模拟酸雨对土壤有效磷衰减的影响

采用pH 3 .0和pH 4.5的 2种模拟酸雨与对照pH 6.0的雨水 ,湿润培育加磷后的土壤 (2种红壤和 1种水稻土 )。试验结果表明 ,土壤中有效磷的衰减在快反应阶段呈直线下降 ,而在慢反应阶段缓慢下降。快反应阶段持续时间约 3～ 6h,随模拟降雨的pH值不同而不同 ,pH值愈低 ,持续时间愈短。与对照相比 ,模拟酸雨对有效磷衰减产生较大影响 ,模拟酸雨pH值愈低 ,有效磷衰减得愈快 ,尤其在快反应阶段影响更为明显 ;在慢反应阶段 ,随着时间的延续 ,影响逐渐变小。模拟酸雨对有效磷衰减的影响因土壤类型不同也不同 ,表现为红壤大于水稻土。酸雨加快土壤有效磷的衰减 ,其主要原因是酸雨作用导致活性铝的大量释放 ,增加了磷的活性吸附点位 。

磷在土壤中有效性的衰减

培育试验表明，磷在红壤中有效性的衰减可分为快反应（３小时）阶段和慢反应阶段，前者有效磷以直线关系下降，后者则为一渐减性曲线。快反应阶段磷有效性的衰减量和土壤活性铝含量呈显著相关，但与活性铁和交换铝相关不显著。用红壤、潮土、板浆白土三种性质不同的土壤进行的生物试验表明，产量也随着土－磷作用时间延长而下降，而且有一个终止时间。中性水稻土在８个月培育后产量即不再下降，石灰性潮土为１６个月，而酸性红壤在２８个月以上。影响产量衰减的可能和磷在土壤中的双核化（转化为环状双核结构）和吸收作用有关，它们在程度上和延续时间上不同土壤不同，在水稻土上最弱，延长时间最短，而在红壤上作用最强，延长时间最长，潮土处于两者之间。