不同有机碳水平下(土楼)土磷的有效性及无机磷形态转化

Phosphorus Availability and Transformation of Inorganic Phosphorus Forms Under Different Organic Carbon Levels in a Tier Soil

【目的】在土壤Olsen-P和全磷含量基本接近但土壤有机碳水平呈梯度的陕西省关中平原(土楼)土上,研究有机碳对土壤各形态无机磷有效性及其形态转化的影响,为合理培肥土壤,有效利用土壤累积态磷提供理论依据。【方法】采集并选取了陕西省关中平原小麦-玉米种植体系下(土楼)土Olsen-P含量相近(平均含量范围17.41—18.72 mg·kg;),不同有机碳水平(有机碳平均含量分别为6.38、8.34、10.17、11.95、13.64和15.74 g·kg;)的土壤样品,采用蒋柏藩-顾益初改进的Chang和Jackson的石灰性土壤无机磷分级方法分别对土壤中各磷组分(二钙磷(Ca2-P)、八钙磷(Ca8-P)、铝结合态磷(Al-P)、铁结合态磷(Fe-P)、闭蓄态磷(O-P)和十钙磷(Ca10-P))含量进行测定。【结果】在陕西关中平原小麦-玉米种植区(土楼)土中,有机碳对土壤各形态磷素水平及形态转化起重要作用。随着有机碳含量的增加,土壤中Ca2-P、Ca8-P、Al-P、Fe-P、O-P、缓效磷库(Ca8-P、Al-P和Fe-P)和难利用磷库(O-P和Ca10-P)含量均显著增加(P≤0.05),Ca10-P相对稳定。有机碳含量与土壤活性磷库(Ca2-P)、缓效磷库(主要为Al-P)的相对含量(占无机磷总量的比例)呈极显著正相关关系,与难利用磷库(主要是Ca10-P)呈极显著负相关关系。土壤Olsen-P含量与难利用磷库含量呈显著正相关关系。【结论】在Olsen-P相近,全磷也基本相似的条件下,土壤有机碳促进了土壤中难溶态磷酸盐向缓效态磷库和活性态磷库的转化,提高了有效磷源占无机磷总量的比例,从而提高了土壤磷素有效性。研究结果表明可通过合理的措施培肥土壤,从而有效地促进土壤累积态磷的活化利用。

【Objective】The influence of organic carbon on the contents and transformation of soil in organic phosphorus fractions were investigated, which can help to formulate soil managemental strategies whereby to improve phosphorus use efficiency in tier soil.【Method】The soil samples were collected and selected with a gradient of organic carbon levels but similar in Olsen-P(ranges from 17.41 mg·kg-1 to 18.72 mg·kg;) under winter wheat summer maize cropping in the Guanzhong Plain of Shaanxi Province. The organic carbon contents of the selected soil samples were 6.38, 8.34, 10.17, 11.95, 13.64 and 15.74 g·kg;, respectively. Then the soil inorganic phosphorus fractions(dicalcium phosphate(Ca2-P), octa-calcium phosphate(Ca8-P), apatite(Ca10-P), aluminum bounded phosphate(Al-P), iron bounded phosphate(Fe-P) and occluded phosphate(O-P)) were analyzed with the phosphorus fractionation procedure proposed by Chang & Jackson and modified by Jiang and Gu.【Result】The results showed that organic carbon played an important role in transformation of soil inorganic phosphorus in the winter wheat-summer maize cropping in Guanzhong Plain of Shaanxi Province. The soil Ca2-P, Ca8-P, Al-P, Fe-P, O-P fractions, moderately labile P(Ca8-P, Al-P and Fe-P),and stable P(O-P and Ca10-P) pools were increased significantly and linearly with increasing soil organic carbon, whereas Ca10-P remained unchanged. The relative contents of labile-P(Ca2-P), moderately labile P(mainly Al-P) were significantly and positively correlated with SOC content, but stable P(mainly Ca10-P) showed significant negative correlation with SOC. Soil Olsen-P increased significantly and linearly with increasing stable P.【Conclusion】Under the similar soil Olsen-P and total phosphorus conditions, soil organic carbon improved the availability of soil phosphorus mainly through promoting the conversion of stable P to moderately labile P and labile P in the soil, increasing the ratio of available phosphorus to inorganic phosphorus, and improving the availability of soil phosphorus. The results implied that improvement of soil fertility(SOC) could promote the activation and utilization of legacy phosphorus in soil.