Effect Of Organic Fertilizer And DMPP On Nitrogen Transformation In Vegetable Field System

The problem that too much chemical fertilizer and unreasonable organic fertilizer application in vegetable plots not only cause the waste of fertilizer and decrease the quality of vegetables, but also cause the environmental problems such as nitrate pollution of groundwater. The large undisturbed soil columns, indoor soil cultivation and soil column simulated rainfall experiment were used to study the influences of organic organic fertilizer and the effect of DMPP addition on vegetable yield, quality and nitrogen transformation and leaching in yellow brown soil. Three vegetable crops(Spinach, Amaranth and Radish) were grown sequentially. In order to provide a theoretical basis for the vegetable safety production and protection of groundwater environment. The main results are as follows:1.Studied with the influnce of applying organic fertilizer and adding DMPP on vegetable’s yield, quality and nitrate leaching by large undisturbed soil core lysimeters revealed that: The vegetable yield and nitrate content of vegetables decreased with the increase of the ratio of organic fertilizer application, and the yield was not decreased significantly when the ratio of organic fertilizer was not higher than 50%. The effect of DMPP on the yield and nitrate content of vegetables was related to the vegetable varieties and planting seasons.2.This paper studied the influence of applying organic fertilizer and adding DMPP on nitrogen leaching by the combination of undisturbed soil trial and simulated rainfall. The results showed that: Rainfall was the key factor of soil leaching, the main form of nitrogen leaching loss from vegetable soil was nitrate nitrogen, which takes up 98.65% of total nitrogen leaching.The reduction effect of adding DMPP on soil nitrate nitrogen leaching was 50%OM+DMPP>30%OM+DMPP>CF+DMPP. At 50%OM+DMPP, the soil nitrate nitrogen leaching concentration and average leaching amount was decreased by 41.64% and 37.65% compared with the pure chemical fertilizer treatment, the nitrogen utilization and loss rates were 26.26% and 4.70% respectively.3.The influnce of applying organic fertilizer and adding DMPP on the physical and chemical properties of soil were studied by using the large undisturbed soil core lysimeters revealed that: Soil organic matter content and p H value increased with the increase of the proportion of organic fertilizer, and the ratio of organic manure could significantly increase the content of soil organic matter in the proportion of 50%. The effect of different proportions of organic fertilizer on soil available nitrogen, phosphorus and potassium showed no significant effect, which indicated that the application of organic fertilizer could maintain the supply balance of available nutrients. The addition of DMPP had little effect on soil physical and chemical properties.4.This paper studied the effect of applying organic fertilizer and adding DMPP on nitrogen transformation by soil cultivation. The application of organic fertilizer itself had little effect on the content of nitrate and ammonium nitrogen in soil, but it could promote the soil nitrification; Adding DMPP could reduce the accumulation of nitrate in the soil by inhibiting the conversion of ammonium nitrogen to nitrate nitrogen, but the restrained effect of DMPP would decrease with the increase of the proportion of organic fertilizer; Taking the effect of DMPP and economic cost into consideration, under the condition of organic and inorganic fertilizer, adding DMPP took 1% of the applied nitrogen; The best period of DMPP restraining time was about 31 days.5.In this paper, we put forward the management method to reduce nitrogen leaching in vegetable field system.(1)Under the conditions that the annual nitrogen 550 kg N/hm2 applied in the yellow brown soil, the recommended organic nitrogen fertilizer should not exceed 50% of the total nitrogen;(2)The optimum adding amount of DMPP is 1% of the nitrogen;(3)It is suggested that fertilizers is applied in several applications according the vegetable growing characteristics;(4)In the rainy season, for each time,we should reduce the amount of nitrogen and irrigation;(5)The integration of technology and promotion.