长期施肥红壤性水稻土磷素演变特征及对磷盈亏的响应

研究双季稻种植制度下长期不同施肥红壤性水稻土磷素含量及磷素有效性演变特征及其对土壤磷盈亏(磷平衡)的响应,为南方双季稻区红壤性水稻土科学施磷提供依据。以35年长期肥料定位试验为平台,研究不同施肥处理土壤全磷、有效磷及磷活化系数(PAC)的演变规律,计算不同处理土壤-作物系统每年磷素盈亏量及累积磷素盈亏量,探讨土壤全磷、有效磷及PAC与累积磷盈亏量的响应关系。结果表明,不施磷肥的CK和NK处理土壤全磷、有效磷和PAC随试验年限呈持平或下降趋势;不施磷肥仅施猪粪的NK+PM处理土壤全磷呈缓慢上升趋势,有效磷和PAC呈下降趋势;施化学磷肥或化学磷肥配施稻草的NP、NPK、NP+RS和NPK+RS处理土壤全磷在试验前10年上升速率较快,之后25年上升速率变缓或随时间变化不显著,土壤有效磷在试验前5年急剧升高,之后随时间变化速率减缓或基本持平。CK、NK和NK+PM处理35年土壤PAC平均值较试验初始值分别下降33.2%、29.7%和16.6%,NP、NPK、NP+RS和NPK+RS土壤PAC较初始值分别提高66.2%、60.6%、65.6%和52.9%。不施磷肥导致红壤性水稻土磷素亏缺,不施化学磷肥仅施猪粪土壤磷素基本持平,施用化肥磷及化肥磷配施稻草土壤磷素盈余。土壤全磷、有效磷及PAC与土壤磷累积盈亏量均呈极显著正相关关系,土壤每盈余磷100 kg hm-2,全磷含量提高0.03 g kg-1,有效磷提高1.20 mg kg-1,土壤PAC上升0.09%。外源磷投入是影响土壤磷素及磷有效性的重要因素,在本试验条件下,长期不施磷或磷投入不足导致土壤磷亏缺,进而导致土壤磷及磷有效性降低,而化肥磷及有机无机磷配施促进了土壤磷盈余及土壤磷素肥力的提高。

Evolution of Soil Phosphorus in Reddish Paddy Soil under Long-term Fertilization Varying in Formulation and Its Response to P Balance

[Objective]This study aimed to explore characteristics of the evolution of content and availability of soil phosphorus and their responses to phosphorus accumulation or loss(P balance)in reddish paddy soil under long-term fertilization varying in formulation under the double rice cropping system,in an attempt to provide theoretical bases for scientific application of phosphorus fertilizer in the double rice cropping areas of South China.[Method]Based on a 35-year long-term fertilization field experiment, researches were carried out on the evolution rules of soil total P,available P and soil P activation coefficient (PAC)in reddish paddy soil as affected by fertilization varying in formulation and history,calculations done of gain or loss of soil P each year and cumulative gain or loss of soil P in the long-term fertilization field experiment varying in formulation,and discussions made of relationships between soil total P,Olsen P,soil PAC and cumulative P balance.[Result]Results show that soil total phosphorus,soil Olsen phosphorus and soil PAC in CK and Treatment NK(No phosphorus fertilizer applied)remained unchanged or displayed downward trends with the experiment going on. Soil total phosphorus in Treatment NK+PM(N and K fertilizer plus pig manure)exhibited a slow rising trend with the experiment going on,while soil Olsen phosphorus and PAC in the treatment did a downward trend. Soil total phosphorus in treatments NP, NPK,NP+RS and NPK+RS(chemical phosphorus fertilizer or plus rice straw)soared during the first ten years of the experiment,but the trend gradually leveled off during the 25 years that followed. Soil Olsen phosphorus in the above-listed-treatments rose sharply to high value in content during the first one to five years of the experiment,and then the rising trend began to level off with the years passing on. Soil PAC fell drastically in the treatments of no or low phosphorus input,but it ascended in the treatments applied with chemical phosphorus fertilizer or plus organic manure. Compared with the initial background value of the experiment field,soil PAC decreased by 33.2%,29.7% and 16.6%,respectively in Treatments CK,NK and NK+PM,but increased by 66.2%,60.6%,65.6% and 52.9%,respectively in Treatments NP,NPK, NP+RS and NPK+RS. Treatment CK(No fertilization)led to soil phosphorus deficiency,while Treatment PM(applying only pig manure)nearly sustained P balance,and Treatments NP,NPK,NP+RS and NPK+RS resulted in apparent surplus of soil phosphorus. Phosphorus balance was very significantly related to soil total phosphorus,soil Olsen phosphorus and soil PAC. With an average surplus of 100 kg phosphorus per hectare,soil total phosphorus increased by 0.03 g kg-1,and Olsen phosphorus by 1.20 mg kg-1 and PAC by 0.09%.[Conclusion] Extraneous phosphorus inputs are the important factors that affect soil phosphorus and soil phosphorus availability. Long-term no phosphorus input and insufficient phosphorus input leads to soil phosphorus deficiency and hence reduction of soil phosphorus content and soil phosphorus availability. Applying chemical phosphorus fertilizer or chemical phosphorus fertilizer plus organic fertilizer promotes soil phosphorus accumulation and improves soil phosphorus fertility.