[Nitrate accumulation in vegetables and its residual in vegetable fields].
Determinations of 11 kinds, 48 varieties of vegetables were carried out at different seasons. The results showed that nitrate-N concentrations in 20 vegetables reached Pollution Level 4 (NO3(-)-N > 325 mg.kg-1), which accounted for 41.7% of the total number of the sampled vegetables and included all of the leafy, and most of the melon, root, onion and garlic vegetables. Among them, 5 leafy vegetables even exceeded Level 4 (NO3(-)-N > 700 mg.kg-1). Although leafy vegetables were usually apt to heavily accumulate nitrate, most of them were with nitrate-N concentrations lower than Level 3 (NO3(-)-N < 325 mg.kg-1) in leave blades. Further investigation showed that vegetable soils accumulated more nitrates in each layer from 0 cm to 200 cm than did cereal crop soil. The total amount of residual nitrate-N was 1358.8 kg.hm-2 in the 200 cm soil profile of usual vegetable fields, and 1411.8 kg.hm-2 and 1520.9 kg.hm-2 in the 2-yaers and the 5-years long plastic greenhouse fields respectively, however that in the cereal crop fields was only 245.4 kg.hm-2. Nitrate residual in vegetable soils formed serious threats to underground water in vegetable growing areas.
Wang
Zhaohui
Z
College of Resources and Environmental Sciences, Northwestern Science and Technology University of Agriculture and Forestry, Yangling, Shaanxi 712100, China. zhaohuiw@public.xa.sn.cn
Zong
Zhiqiang
Z
Li
Shengxiu
S
Chen
Baoming
B
D000383:Agriculture; D005308:Fertilizers / Q000009:adverse effects; D009566:Nitrates / Q000032:analysis*; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000009:adverse effects; D014675:Vegetables / Q000737:chemistry*
D005308:Fertilizers; D009566:Nitrates; D012987:Soil; D012989:Soil Pollutants