Effects of nitrogen in organic fertilizer instead of chemical fertilizer on the yield and quality of leaf vegetables and soil nitrogen residues

摘要

Application of organic nitrogen amendments and reduction of chemical fertilizer are considered as an effective approach in sustainable agriculture. Three field experiments were conducted to study the effects of nitrogen in organic fertilizer instead of chemical fertilizer nitrogen (0, 25, 50, 75 and 100%, and marked as 100CF, 250M75CF, 50OM50CF, 750M25CF and 100OM) on the yields and qualities of leaf vegetables and soil nitrogen residues. The planting season was arranged with pakchoi, lettuce and Chinese cabbage seedling. The results showed that the yield differences among treatments were gradual decreased with the extension of planting time, In Chinese cabbage seedling season, the yield of 250M75CF treatment reached 7.74x104 kg hnr2. Overall, 250M75CF and 50OM50CF treatments could obtain considerable yields of leafy vegetables with 100CF treatment, but leaf nitrate, soluble sugar and total acid content were all higher than that of in 100CF treatment. Leaf nitrate content of 750M25CF and 100OM treatments were 3.13 and 35.30% lower than that of in 100CF, but soluble sugar content increased by 23.97 and 34.69%. The nitrogen substitution ratio of organic fertilizer was positively correlated with VC (R=0.077) and sugar acid ratio (R=-0.129), while itnegatively correlated with free amino acid content (R=0.173). With the increase of organic nitrogen substitution ratio, the soil nitrate and ammonium contents decreased gradually. Compared with 100CF, organic fertilizer nitrogen replacement treatments for 0-20 cm, soil nitrate and ammonium reduced by 10.67-16.11% and 23.13-69.03%, and the 20-40 cm of soil nitrate and ammonium reduced by 21.15-60.77% and 2.04-10.20%. Therefore, for the leafy vegetables, the nitrogen in organic fertilizer instead of 25-50% chemical nitrogen can obtain better yield and quality, meanwhile reducing the environmental risk of nitrate nitrogen.