秋浇对内蒙古农业灌区磷元素迁移转化的影响

通过对内蒙古农业灌区一年中水量最大的一次灌溉（秋浇）期间,灌、排水干渠和农田土壤中总磷（TP）、无机磷（IP）以及有机磷（OP）进行分析监测,考察了秋浇对灌区磷元素迁移转化的影响.研究表明,秋浇使灌区土壤水分得到极大地补充,促进了土壤磷元素的溶解.由于灌溉引水中携带了大量泥沙,附着了较高含量的颗粒态磷（PP）,并沉积在农田土壤中,使灌区土壤总磷含量略有升高,排水中总磷浓度降低.原有土壤中有机磷在碱性环境中与土壤中钙离子形成难溶性盐类,促进反应平衡向有机磷增加的方向进行,使灌区有机磷含量大幅增加.同时,在周期较长的淹灌期间,土壤潮湿的厌氧环境增强,促进了厌氧微生物对溶解态磷的吸收利用,将其转变成有机态磷,因而在灌区土壤和排水中有机磷含量均有显著提高.

Impact of fall irrigation on phosphorus transportation & transformation in the agricultural irrigation area in Inner Mongolia

The impact of irrigation on phosphorus transportation and transformation in the agricultural irrigation area in inner Mongolia during the period of fall irrigation was analyzed by monitoring the soil water ratio, total phosphorus (TP), inorganic phosphorus (IP) and organic phosphorus (OP) concentration from farmland soil and water in both irrigation ditches and drainage streams. The fall irrigation uses the largest volume of irrigation water in the year. The research showed that the soil water ratio was greatly increased, which resulted in the dissolution of soil phosphorus. The irrigating water carried substantive particulate phosphorus (PP) which settled in the soil and became adsorbed, leading to a slight increase of TP in the soil and subsequently a large reduction in the drainage streams compared with that in the irrigation ditches. The inherent soil OP and calcium ion were adsorbed onto insoluble substances which shifted the chemical equilibrium in the direction of OP generation, which led to a large gain in OP. The wet soil became more anaerobic because of the long submersion time which promoted the utilization of soluble phosphorus by anaerobes and its transformation to OP, which explains the dramatic augmentation of OP in both soil and drainage streams.