Effects Of Different Irrigation And Fertilizer Management On Nitrogen Leaching Control In Soil

Excessive fertilization and irrigation is general in greenhouse during the process of planting vegetable,because economic benefits are excessively pursued by farmers.This wastes water resources and fertilizers seriously,and causes groundwater polluted,and results in a series of environmental problems.In view of these problems,two parts of experiments were involved in this paper.Soil column experiment and cucumber planting in greenhouse were conducted.Soil column experiment was to study the better measures to resistance nitrogen leaching through assessing the effects of adding different additives（urea（U）,slow-release fertilizer（SRF）,organic manure（O）,dicyandiamide（U+D）,biological activated carbon（U+B））on the leacheate volume,pH,EC and concentration of NO₃^--N and NH₄⁺-N in both soil and leacheate.Cucumber planting in greenhouse was to study the effects of reducing water and fertilizer amount on vegetables and soil quality in greenhouse,which was conducted to determine the yield,nutrients accumulation,irrigation water productivity（IWP）,partial factor productivity of nitrogen（PFP_N）of cucumber,and leaching of nitrogen and phosphorus in soil.The thesis was practical to provide theoretical basis for nitrogen leaching control in greenhouse.The main results are as follows,1.The soil column experiment showed that application of biochar could significantly increase the EC of leacheate,which was 4.87 times of urea treatment.With the increasing of leaching times,the concentration of NO₃^--N in leacheate decreased,while the concentration of NH₄⁺-N in leacheate showed irregular trend.Application of slow-release fertilizer,organic manure,dicyandiamide and biochar could significantly decrease NO₃^--N leaching amount by 18.05%,18.78%,25.65%and 81.54%comparing to application of urea,respectively.However,application of organic manure could significantly decrease NH₄⁺-N leaching amount by 68.87%,while application of slow-release fertilizer,DCD and biochar could significantly increase NH₄⁺-N amount by 18.77%,23.86%and 42.88%comparing to application of urea,respectively.2.The soil column experiment showed that with the increasing of soil depth,soil pH increased,while soil EC decreased.The pH of the 0-20 cm soil layer was negatively correlated with fertilizer amount,and was independent of additives.At the same nitrogen level,application of slow-release fertilizer and biochar could significantly increase the NO₃^--N accumlation by 8.97%and 30.34%,respectively than that of urea.On the contrary,application of organic manure and DCD significantly decreased the NO₃^--N accumlation by66.41%and 50.19%than that of urea,respectively.Comparing to application of urea,application of organic manure,slow-release fertilizer and DCD could significantly increase the NH₄⁺-N accumlation by 34.35%,60.22%and22.47%,while application of biochar could significantly decrease the NH₄⁺-N accumulation by 2.52%.3.The soil-column experiment showed that reducing irrigation rate could significantly decrease the NO₃^--N amount and NH₄⁺-N amount of the leacheate,and could also increase the NO₃^--N amount and EC of the soil.Irrigation amount were not correlated to the soil NH₄⁺-N amount.Increasing fertilizer amount could increase the EC,and NO₃^--N and NH₄⁺-N amount in soil.Application of biochar was the best in reducing nitrogen leaching for all concerned in the experiment.4.The experiment in greenhouse showed that less inputs on the basis of farmer’s fertilizer amount and water saving irrigation didn’t reduce the yield of cucumber.On the contrary,water saving irrigation could decrease the soil pH and leaching of nitrogen and potassium.Reducing the fertilizer amount and using drip irrigation could increase the nutrient contents of the aboveground part of cucumber and the underground part of cucumber than that of traditional irrigation mode,while it had no obvious effect on nutrient content and accumulation of cucumber.5.The apparent balance of cucumber in this season was surplus,and the surplus was positively correlated with the fertilizer rate.Drip irrigation could significantly reduce nutrient surplus under different irrigation amount.Within the test range,yield,irrigation water production rate（IWP）and nitrogen partial productivity（PFP_N）of the cucumber in T2（low fertilizer rate+drip irrigation）were the highest,and the nutrient surplus in T2 was the least.