土壤水分对蔬菜硝态氮累积的影响

采用耕层红油土进行盆栽试验，在每千克土施０．４０ｇＮ和０．３０ｇＰ２Ｏ５的基础上，种植小白菜（黑油菜）和菠菜（宁夏圆叶）。采样前１０ｄ设置１５０，２００和２５０ｇ／ｋｇ３个土壤水分等级，研究土壤水分对蔬菜生长和硝态氮累积的影响。结果表明，在土壤水分为２００和２５０ｇ／ｋｇ时，菠菜的生长量比水分为２５０ｇ／ｋｇ时提高１０８．７％和１７４．８％，小白菜提高１０８．９％和１０９．９％；而菠菜的硝态氮含量却分别降低２９．７％和１９．４％，小白菜降低２２．５％和２５．０％；２种蔬菜的硝酸还原酶活性亦明显降低。对蔬菜生长、硝态氮吸收及还原的分析表明，土壤水分增加不仅促进蔬菜生长，还促进硝态氮的吸收及向地上部分转移。但生长量和硝态氮吸收的增加并不同速，由于生长超前引起的植物体内养分释稀效应，是增加土壤水分蔬菜硝态氮含量降低的主要原因。

The Influence of Soil Water on Nitrate Accumulation in Vegetable

Pot experiments were carried out with a red-oil soil by using Chinese cabbage and spinach as indicating crops, in order to study the influences of soil water on nitrate accumulation in vegetables at a fertilization rate of 0. 40 g N and 0. 30 g P₂O₅ per kg soil.The results obtained showed that the yields of the two vegetables increased more significantly at the soil water contents of 200 g /kg and 250 g /kg than at that of 150 g /kg, an increase of 108. 7% and 174. 8% for cabbage, and 108. 9% and 109. 9% for Chinese cabbage. In contrast, the nitrate-N contents of the two vegetables decreased obviously, being 29. 7% and 19. 4% for spinach, and 22. 5% and 25. 0% for Chinese cabbage.Also decreased the nitrate red uctase activities of the vegetables. Comparing the vegetable growth and the nitrate-N absorption and reduction, it is found that high soil water supply increased notonly the vegetable growth but also the nitrate absorption and its translocation from roots up to the above-ground parts.However, both the biomass and the nitrate increases were not in the same proportion.The dilution effects caused by more increase of biomass than nitrate absorption were the major cause for the decrease of nitrate-N contents athigh soil water supply.