Effects Of DMPP And Chitin On Nitrate And Cd Contents In Vegetables In Suburbs

Suburban agriculture is an important part of modern agriculture in China.It is widespread phenomena of heavy metal pollution and high nitrate content in suburb vegetables due to industrialization of suburb and unreasonable application of chemical fertilizer in recent years,which will not only greatly reduce the quality and safety of vegetables,but these pollutants will also accumulate through the food chain and endanger human health.In this study,to provide a theoretical basis for safe production of vegetables in Wuhan suburban growing area of vegetables,we studied the effects of DMPP and chitin based on reduced 30% inorganic fertilizers and combined application of organic manure on nitrate and Cd contents of vegetables in pot and field culture.The main results are as follows:1.Compared with the recommended fertilization,Reduced 30% chemical fertilizer decreased significantly the nitrate contents of vegetables by 16.75% in leafy vegetables and 25.52% in fruit vegetables.However,the output of vegetable was reduced by 14.02%and 1.4%,respectively.The contents of soluble sugar and Vc in vegetables were decreased with the decrease of fertilization,and there was no significant difference in the content of soluble protein.The absorptions of NK in leaf vegetables were decreased significantly with the decrease of fertilization,but there were no significant changes in NPK absorption in fruit vegetables and no significant differences in soil physicochemical properties,but the utilization rates of N,P and K fertilizer increased by at least 3percentage points with the decrease of fertilization.2.The nitrate contents in vegetables were reduced significantly by 23.49%-55.36%by DMPP or chitin alone supply and combined application of DMPP and chitin under reduced 30% chemical fertilizer,and the reduced influence was DMPP + chitin >DMPP > chitin.There was no significant influence on vegetable yield between single and combined application of DMPP and chitin,but the yields were significantly improved,and the yield increasing rate of fruits vegetable was 34.23% by treated with DMPP.The single and combined application of DMPP and chitin could increase the absorption of nitrogen,phosphorus and potassium in fruits and vegetables(except DMPP),but therewas a tendency to reduce the absorption of nitrogen,phosphorus and potassium in leafy vegetables.DMPP and chitin could improve soil properties and soil organic matter content;The utilization rates of N,P and K fertilizer for fruit vegetables were increased by 15.64,7.63 and 19.51 percentage points respectively.3.The nitrate contents in vegetables were reduced significantly by 9.86%-49.86% by DMPP or chitin alone supply and combined application of DMPP and chitin under recommend fertilization condition,and the reduced influence was DMPP+ chitin >DMPP > chitin,and the Cd content of vegetables were decreased by 9.2%-30.22%.Increase of vegetable yield in fruit vegetables was more than that in leafy vegetables.Application of chitin was the best treatment in increased yield of leaf vegetables,the rate of increase was 19.66%;application of DMPP+ chitin was the best treatment in increased yield of fruit vegetables,the rate of increase was 64.79%.Single and combined application of DMPP and chitin increased the contents of Vc,soluble protein and soluble sugar(except soluble sugar in fruit vegetables).Application of DMPP and chitin promoted the release of soil available nutrients,improved soil organic matter contents and increased NPK accumulations in vegetables;Single and combined application of DMPP and chitin increased the utilization rates of N,P and K fertilizer,and the utilization rates of fruit vegetables were higher than that of leaf vegetables.4.With application of organic fertilizer,the contents of nitrate and Cd were decreased by 4.5%-24.1% and 12.95%-22.59% respectively in vegetables,and there were increased tendency in contents of Vc,soluble sugar and soluble protein in vegetables.The yield of leafy vegetables were increased by 5.62%,NPK absorption of vegetables,the content of available NPK and the utilization rates of N,P and K fertilizer in current season were increased by 5.65 percentage points,and organic matter content in soil were all increased,5.The nitrate and Cd contents in vegetables were reduced significantly by11.5%-52.6% and 17.95%-41.35% by DMPP or chitin alone supply and combined application of DMPP and chitin under combined with organic fertilizer condition,and the reduced influence of nitrate in leafy and fruit vegetables in DMPP+ chitin treatment better than that in single application treatment,moreover,the reduced influence of Cd in fruitvegetables in DMPP+ chitin treatment better than that in single application treatment,however,the chitin treatment was the best treatment in leafy vegetables.DMPP or chitin alone supply and combined application of DMPP and chitin could improve the quality of vegetables,improve the content of organic matter in soil and promote the absorption of NPK in leafy vegetables.The utilization rates of N,P and K fertilizer in current season were increased by 34.64、13.77、57.83 percentage points by DMPP or chitin alone supply and combined application of DMPP and chitin under combined with organic fertilizer.In conclusion,combined application of DMPP and chitin with the decrease of fertilization or combined with organic fertilizer reduced the accumulation of nitrate and Cd in vegetables and improved the utilization rates of N,P and K fertilizer in current season,and promote the safety production of suburban vegetables.