低施磷水平下不同施肥对太湖地区黄泥土磷迁移性的影响

对太湖地区水稻土上长达13年的长期不同施肥处理的某试验田进行了土壤全磷、树脂磷和水溶性磷的测定分析.不同处理的年施磷量为0～53kg/(hm²·a),土壤全磷为0.3～0.5g·k^-1.根据土壤磷素的质量平衡,计算表明该水稻土存在的磷素流失量为2～8kg/(hm²·a),单施化肥下的流失量最大,为配施有机肥处理的2～4倍;水溶性磷的比率在0.2%～0.4%间,且不同施肥实践对其的影响不明显.但单施化肥有使亚表层树脂磷和水溶性磷含量提高的倾向.长期施用化肥配施大量鲜猪粪使树脂磷含量提高20～40 mg·kg^-1,但与长期施用化肥配施秸秆的处理一样没有发生在有机质增加下的磷活化而提高磷流失.这些说明本地区长期单施化肥的水稻土中可能存在强烈的磷流失,且水稻土磷流失并不以水溶解发生.为了防止水稻土磷的强烈水流失而加剧农业非点源污染,要避免长期单施化肥,而应坚持和推广配施适量有机肥.

Effect of Longterm Fertilization Practices on Mobility of Phosphorus in a Huangnitu Paddy Soil Receiving Low P Input in the Taihu Lake Region,Jiangsu Province

Analysis of mobile forms of phosphorus of a Huangnitu, a typical paddy soil in the Taihu Lake region, Jiangsu was conducted. The soil has been put into a scheme of longterm fertilization treatments for 13 years. Total P content varied in arrange of 0.3-0.5 g.kg-1 under a range of total P fertilizer input of 0-53 kg/(hm2.a). As estimated from the total P pool values by mass balance principle, the soil had been subjected to water loss of P 2-8 kg/(hm2.a), with that under chemical fertilizers only being the biggest. The ratio of soluble P to the total was in a range of 0.2%-0.4%, without significant influence by the different fertilization schemes. While chemical fertilizer plus pig slurry manure applications had remarkably enhanced the resin-P pool by 20-40 mg.kg-1, P mobilization was not observed due to combined application of chemical fertilizers and straw amendments despite of the increase of the SOM. Therefore, P water loss in paddy soils might have active under continuous chemical fertilization alone in agriculture of this region and could not be accounted for by dissolution in water and subsequent runoff migration. For reducing the present prominent non point source pollution of N and P in the region, it is suggested that chemical fertilizers are applied in combination with an appropriate amount of manure or straw return for reducing soil P loss and, in turn, the non-point source pollution loading.