The Law Of Nitrate Transportation And Assimilation Study In Soil-Vegetable System Under Different Conditions Of Water And Fertilizer

Nitrate leaching is the main loss of nitrogen fertilizer which will result in nitrate accumulation in the deeper soil layers,and will make the groundwater polluted in some potential way.with the development of intensive agriculture,the amount of the fertilizer and the irrigation,The environmental quality of the farmland and the underground water is becoming more and more worse,A quantitative understanding of the movement and distribution of nitrate in the soil profile,recommending economical fertilizer and irrigation requirement is required to reduce leaching loss of nitrate and to improve nitrogen fertilizer efficiency,which can provide theoretical basis for rational application of fertilizer.This paper studied cabbage which is representative for Beijing regional pattern,it focus on nitrogen migration under different water and fertilizer levels and studied the impact on the yield,In accordance with the comprehensive relations of the fertilizer amount and the crop yields,we proposed the best economic fertilization and irrigation amounts.The study of lysimeter experiment combination with the method of field trial,first of all,with the use of the indoor soil column experiment,it concluded the nitrate leaching under different soil texture at different water and fertilizer levels through the analysis the leakage;in conjunction with the analysis of the nitrate diversification in the0-100cm soil profile and the nitrate concentration.Then it calculated the nitrogen loss using the nitrogen-quality-equity method within a certain soil profile.At last it evaluate the relationship between different fertilizer and irrigation amount between the yields,At last it put forward reasonable irrigation and fertilization program.The following conclusion was drawn from the experimental and simulation studies:1.According to the lysimeter experiment we concluded:under the condition of lower irrigation,the diversification of NO3-N concentration has very small changes in different fertilizer levels,which shows an upward trend in the anaphase of the eluviations,in the condition of lower irrigation,it showed a similar concentration of "normal" trend.The experiment illuminated that nitrogen fertilizer can not be completely removed from the 1m of soil profile in a certain period of time under the conditions of lower irrigation and can be used effectively by the crop,but under the conditions of higher irrigation,the nitrogen fertilizer leached almost completely2.In the whole period of the leakage,the change of the concentration of NH₄⁺-N is small, the overall changes were not substantial changes in its scope which has been maintained at a lower level of 0-9 mg/kg,maintained at the average of 2 mg/kg or so,so it can be ignored in the soil inorganic nitrogen fertilizer recommendations.In addition,because of the impact of nitrate concentration,the pH value will drop to the lowest point when the NO₃^--N concentration achieved the maximum.The overall trend is negatively correlated,but it need further study to find the specific function.3.We concluded through the field experiments that the change of the concentration of NH₄⁺-N in the profile showed no significant differences in different growing periods.4.The nitrate content in the soil profile increased gradually with the increase of fertilizer dose,but it dropped with the increase of the irrigation amounts.The nitrate in the soil profile increased with the increase of the fertilizer amount and the irrigation amount. Because it only 2 months after the cabbage planted,so most of the fertilizer was lost in a variety of ways.The maximum loss of nitrogen is up to 420.34 kg/hm² in the condition of W₃N₃(N 450 kg/hm²,Water 4800 m3/hm²).5.In the harvest time,the nitrate content increased in a significantly downward trend with the increase of the irrigation amount.Compared to W₁,the nitrate content of W₂,W₃ in the plant were all decreased by 54.41%,38.59%,37.20%and 71.50%;45.73%;46.97%, there is no significantly different among the irrigation level in the condition of N₀.6.Fertilization and irrigation affect crop yields through nitrogen content in plants considering from the environmental protection and high yield,the economical fertilizer and water application rates for cabbage are 3767.06m³/hm² and 255.82kg/hm² respectively.The ideal yield is 104323.56 kg/hm².