磷在土壤中的固定机制和磷肥的高效利用

磷肥当季利用率只有10%～25%，通过系统分析文献研究进展表明，磷肥低效利用的主要原因是土壤对磷的固定，固定方式包括吸附固定和化学反应固定。土壤对磷的固定取决于土壤中碳酸钙、铁铝氧化物、土壤粘粒的含量以及土壤中磷的初始浓度，在施肥初期发生大量的吸附固定，持续数小时至数十小时，后期逐渐转化为化学反应固定，使有效态磷转化为无效态磷，持续数月乃至数年。磷肥在土壤中的固定动力学可用Elovich方程描述。要减弱土壤对磷的固定，需要降低土壤中水溶性磷的浓度。本文结合文献中报道的嵊县红壤对磷的固定规律和油菜对磷的吸收特性，定量分析了磷在土壤中的释放、固定、吸收过程，通过建立模型计算得出，与单施普通磷肥相比，混施普通磷肥和包膜磷肥可大幅度降低施肥量和提高磷的当季利用率。

Mechanisms of phosphorus fixation in soils and efficient utilization of phosphate fertilizer

The utilization efficiency of phosphate fertilizer in the whole life of plant is only 10%—25%. By analyzing the research progress in the literatures，it indicates that the phosphorus is easily fixed in soils，including adsorption fixation and chemical reaction fixation. The amount of phosphorus fixed is determined by the content of calcium carbonate，iron oxide，aluminum oxide，clay and the initial concentration of phosphorus in soils. Most of phosphorus is fixed in adsorption fixation in early period，which lasts several hours to tens of hours. In later period，chemical reaction fixation occurs mainly and lasts a few months to a few years，which results in phosphorus unavailable to plants. The dynamics of the entire fixation period can be described by Elovich equation. For reducing the amount of phosphorus fixed，an efficient way is to reduce the concentration of phosphorus in soils. By using the fixation data from the red soil in Shenxian (in Zhejiang province，China)，together with the research data on the phosphorus uptake of cole，the release，the fixation and the plants uptake of phosphorus are quantitatively analyzed. The calculation result based on the established mathematical model indicates that the consumption amount of fertilizer can be greatly reduced and utilization efficiency can be increased by fertilizing the mixed DAP and controlled released DAP，compared with that by fertilizing DAP only.