上海市蔬菜地土壤硝态氮状况研究

以上海市郊不同管理方式下菜地表层土壤采样测定土壤硝态氮含量为基础,并以水稻土等土壤作为对照,以期了解上海蔬菜地土壤硝态氮的现状,为菜地的合理施肥提出科学依据。结果表明,由于管理方式不同,土壤的硝态氮的NO3--N质量分数差异明显。大棚蔬菜地土壤中NO3--N明显高于其它其他用地管理方式下的土壤,依次为:w(大棚蔬菜地)>w(露天蔬菜地)>w(传统自留地),而且土壤硝态氮的积累是全剖面性的,而非仅在表层,如在80~100cm土层,大棚土壤硝态氮也为农田的好几倍。而且,大棚蔬菜地土壤盐渍化明显,主要特点之一是硝态氮积累,盐分高的土壤一般硝态氮也高。此外,长期大量的N肥投入引起了土壤酸化。土壤pH与土壤NO3--N质量分数呈线性负相关,经统计检验相关性达极显著水平。

Nitric nitrogen in soils of vegetable garden in Shanghai city

Based on the samples from the surface soil layers of vegetable garden in the suburbs of Shanghai city and measurement of soil NO3--N content in different management modes, this article contrasts it with ripe soil to learn the current situation of NO3--N in soils of vegetable garden in the city and provides scientific gist for reasonable fertilization. Experiment results showed that contents of NO3--N in the soils were greatly different among different management modes. The results indicated that there was much more nitric nitrogen in soils of vegetable garden in greenhouse, followed by the soils of opened vegetable garden, and then by the soils of traditional vegetable garden. Accumulation of soil NO3--N was in all profile, not merely in the surface layer. For instance, in the depth of 80~100 cm, NO3--N content in soils in greenhouse was several times as many as that of the field. Furthermore, salinization of soils in vegetable garden in greenhouse was evident, and one of the main characteristics was NO3--N accumulation. The more salt in soil, the more NO3--N in soil. Moreover, the excessive nitrogen fertilizers resulted in decrease in soil pH. Statistical analysis showed that there was a significant negative correlation between soil pH and contents of nitric nitrogen.