包膜控释和常用氮肥氮素淋溶特征及其对土水质量的影响

大量施用氮素化肥所引起的氮素损失和环境污染正日益受到重视。通过土柱模拟氮素养分的淋洗试验,探讨包膜控释氮肥和常用氮肥的氮素淋失特点及其对土壤和地下水质量的影响。研究结果表明,不同氮肥施入土壤后氮素的淋失率有着显著的差异,其中硝酸钾中氮素淋失率最高,其次为尿素,硫酸铵和碳铵的氮素淋失量明显较小。然而控释氮肥因其控制释放的特点,在氮素释放的高峰期,其模拟淋失量较高,但如果在田间条件下此释放高峰期与作物吸肥高峰期相吻合,则会显著地降低其淋失率。除尿素外,被淋失的氮素均以硝态氮为主,尿素则以酰胺分子态被淋溶。大量速效化肥的施入会形成土壤中的肥料"微域点",引起交换性Ca2+、Mg2+离子的淋失,从长远来看可引起土壤结构的破坏,而施用控释肥则很少形成这种"微域点",有利于土壤结构和肥力的维持。不同氮肥处理淋洗后对土壤pH值和有效氮含量变化的影响差异较大,其中以控释肥对土壤pH值变化的影响较小。大多数氮肥处理在淋洗后,土壤中各层速效氮含量较淋洗前有所降低,然而两种控释氮肥处理的土壤表层却能持续保持较高的有效氮含量。

Leaching characteristics of controlled release and common nitrogen fertilizers and their effects on soil and ground water quality

The nitrogen loss and environmental pollution hazards resulted from application of large amount of fertilizers have been increasingly emphasized. The leaching characteristics of controlled release and common nitrogen fertilizers and their effects on soil and ground water quality were investigated through soil column nitrogen leaching experiments. The results showed that nitrogen leaching rates were significantly different among several controlled release and common nitrogen fertilizers. Potassium nitrate ranked the first, urea the second. Nitrogen leaching rates of ammonium sulfate and ammonium bicarbonate were comparatively lower. The simulating N leaching rates for controlled release fertilizers (CRFs) were relatively higher during later leaching period due to the peak release of the CRFs. However, if the release peak of CRFs was synchronized to the plant need, the N leaching rate would considerably reduced. The forms of N on leachate were mainly nitrate for most N fertilizers except urea. High loading of fertilizers in soil might form the fertilizers "microsite", which would cause the leaching loss of exchangeable Ca2 and Mg2 ions and resulted in the soil deterioration or structural damage from a long run. However, these fertilizer "microsites" were rarely formed by application of CRFs, which would beneficial to the conservation of soil structure and improvement of soil fertility. The changes of soil pH and available N content were obviously different among the different N fertilizer application after soil column leaching. The effect of CRFs on the soil pH changes was comparatively lower. The available N content in most soil layers was lower after leaching than that before leaching, but the soil surface horizon with CRFs kept relatively higher available nitrogen content.