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Changes of soil nitrogen types and nitrate accumulation in vegetables with single or multiple application of dicyandiamide
Created on 05.12
Abstract: Field experiments were conducted to investigate the changes in soil nitrogen forms and nitrate accumulation in vegetables under single and continuous application of dicyandiamide (DCD).
The results showed that compared with the sole application of chemical fertilizer, during the long-term growth of cabbage, the single application of DCD increased soil ammonium nitrogen content by 21.3%-339.4%, while soil nitrate nitrogen and vegetable nitrate contents decreased by 4%-80.2% and 4.4%-58.3%, respectively; at the harvest of short-term leafy vegetable water spinach, soil ammonium nitrogen content increased by 299.4%, while soil nitrate nitrogen and vegetable nitrate contents decreased by 26.2% and 31.7%, respectively.
In the "cabbage-sater spinach-radish cabbage" cropping system with continuous application of DCD, soil ammonium nitrogen, nitrate nitrogen, and vegetable nitrate contents all showed an accumulative trend. Soil ammonium nitrogen content under DCD application developed from slightly higher than the chemical fertilizer treatment (44.0%) to significantly higher than the chemical fertilizer treatment (392.5%, P<0.01); soil nitrate nitrogen content developed from significantly lower than the chemical fertilizer treatment (-68.2%, P<0.01) to significantly higher than the chemical fertilizer treatment (146.6%, P<0.05); and vegetable nitrate content developed from significantly lower than the chemical fertilizer treatment (-30.2%, P<0.05) to significantly higher than the chemical fertilizer treatment (40.4%, P<0.01).
Therefore, the single application of DCD can significantly reduce vegetable nitrate content, while the soil with continuous application of DCD can maintain a certain level of ammonium nitrogen, and these surplus ammonium nitrogen will be further converted into nitrate nitrogen remaining in the soil, which may pose a risk of vegetable nitrate accumulation.
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