长期不同施肥下潮土磷素的演变特征

【目的】研究在施磷量相等的条件下长期施用有机肥和化肥对潮土全磷、有效磷的演变的影响,为潮土地区农业生产和地力培育提供理论依据。【方法】以河南封丘的肥料长期定位试验(开始于1989年)为平台试验设置7个处理,即有机肥(OM)、1/2有机肥+1/2化肥(1/20M)、氮磷钾(NPK)、氮磷(NP)、磷钾(PK)、氮钾(NK)和不施肥处理(CK)分析比较了不同处理土壤的全磷、有效磷含量及两者比值的演变规律。【结果】所有施磷处理土壤全磷均与试验年份呈显著线性相关,1/2有机肥+1/2化肥、有机肥和氮磷钾处理土壤全磷年均增加量为0.0083、0.0081和0.011 g/kg;各处理2008~2010年3年平均土壤有效磷含量大小顺序为PKOM1/20MNPKNPCKNK施磷处理下试验进行的前11年土壤有效磷快速增加,以后达到稳定状态;有机肥处理和1/2有机肥+1/2化肥处理土壤有效磷与全磷的比值显著高于氮磷钾处理,试验20年后有机肥处理和1/2有机肥+1/2化肥处理有效磷/全磷是氮磷钾处理的1.9和1.4倍。磷素平衡与全磷及有效磷含量均达到了极显著相关相关系数分别为0.981和0.886。磷素盈亏每增加100 kg/hm2土壤全磷含量增加0.04 g/kg土壤有效磷含量增加约为2 mg/kg。试验20年后其他理化性质与土壤全磷、有效磷含量之间的相关关系均未达到显著水平。但土壤有机质和土壤全氮与有效磷/全磷的相关系数达到了显著水平,说明土壤有机质和全氮含量提高有利于土壤磷素的活化。【结论】土壤全磷和有效磷的演变都显著受磷素盈亏的影响。在每年P_2O_5投入量相当于135 kg/hm~2时施用化肥更加有利于潮土全磷含量的提高;经过21年的不同施肥处理,平衡施用化肥处理有效磷含量只能维持在7 mg/kg左右这一水平处于中低水平,依旧需要磷的投入才能维持作物的高产。施用有机肥可以在不增加施磷量的条件下增加作物可吸收利用的磷。因此减少施磷量增施有机肥可能成为潮土地区减肥增效的重要手段。

Dynamics of phosphorus in Fluvo-aquic soil under long-term fertilization

【Objectives】 In order to provide theoretical basis for agricultural production and soil fertility improvement, this study tried to investigate effect of a long-term (1989-2010) compost and mineral fertilizer application on dynamics of soil phosphorus in the North China Plain under condition of equal input of phosphorus fertilizer. 【Methods】 The long-term experiment consisted of seven treatments, organic compost (OM), half-organic compost plus half-NPK mineral fertilizer (1/2OM), NPK, NP, PK, NK, and control (CK). Soil total P and available P under different fertilization treatments were determined, and then the ratios of available P to total P were calculated. Impact factors on the phosphorus dynamics were investigated. 【Results】 There was a significant positive linear correlation between the soil total P contents under the P applied treatments and the years of the experiment. The average annual increments of total P under the 1/2OM, OM and NPK treatments were 0.0083 g/kg, 0.0081 g/kg and 0.011 g/kg, respectively. The order of 2008-2010 average soil available P in the different fertilization treatments was PK OM 1/2OM NPK NP CK NK. The soil available P contents were increased quickly in the first 11 years, while the available P contents were relatively stable in the latter 10 years. The ratios of available P to total P of OM and 1/2 OM were significantly higher than that of NPK, and the ratios of OM and 1/2 OM were 1.9 and 1.4 times of that under NPK. The P balance was correlated significantly with total P and available P, and the correlation coefficients were 0.981 and 0.886, respectively. Each 100 kg/hm2 increase in the P balance associated with 0.04 g/kg in soil total P content and 2 mg/kg in available P content. Other soil physico-chemical properties such as organic matter did not significantly relate to total P and available P. However, soil organic matter and total N significantly related to the ratio of available P to total P. 【Conclusions】 The P balance had strong influence on dynamics of soil total P and available P. In comparison with the compost, the chemical fertilizer can improve accumulation of total P when the application amount of P fertilizer is P2O5 135 kg/hm2 per year. The available P content is about 7 mg/kg after 21 years mineral fertilizer application, and still unable to meet the requirement of crop growing. The compost application can activate soil P and increase the availability of soil P when the input of phosphorus fertilizer is equal. Therefore, increasing the compost portion in the total P input should be recommended to improve soil fertility and protect environment in the North China Plain.