| Nitrogen（N）is abundantly used in vegetable crops to enhance the production but cause serious environmental threat as nitrate leaching in China.The concept of N fate in a particular soil is important for the selection of control measures.Hence,this study was based on the field experiment,lysimeter and conceptual GIS study of the North China Plain.Field study was conducted to analyze the variations in the plant available N（PAN）concentrations in the soil profile.Different fertilizers were applied for the Chinese cabbage plantation（CCP）in the experiment fields of Shunyi region.The treatments used for the comparative analysis namely as:（i）no fertilizer and plantation（NVP）,（ii）no fertilizer with CCP（CTP）and（iii）fertilization as urea（URP）,（iv）potassium nitrate（KNP）and chicken manure（CMP）with CCP.In URP,maximum PAN in soil layers 0-60cm was recorded during crop production and in60-100cm after harvesting as compared to other treatments.CMP showed maximum ammonium in the upper layers 0-60cm throughout the season,whereas minimum PAN was observed in NVP but increased in lower layers 60-100 cm.In general,all fertilizers raised the PAN below the soil 60-100cm which indicates their potential for the nitrate leaching.In lysimeter study,15N urea with biochar（BC）and without biochar（WB）and control without urea（CK）were applied for the crop plantation（Brassica Campristris Var.Chinensis）in two consecutive seasons.As compare to WB,BC significantly decreased mineral N leaching including nitrate levels（35%）,increased EC（168%）and water use efficiency（12%）,while non-significant increase in mean yield（15.98%）,evapotranspiration（8.33%）,dry matter（6.89%）and decreased in mean leachate volume（7.63%）.Moreover,BC presented higher N uptake（6.68%）,growth rate（7.3%）and N retained（185%）after the first and second cropping season whereas;the soil pH,bulk density and total N presented non-significant differences.Therefore,biochar amendment can condition the soil to improve water and nitrogen holding ability which is supportive to improve crop production and decrease N leaching from an agriculture land.The NCP study was conducted to manipulate the available record in the form of GIS raster data or published paper to make assessment for the nitrate leaching.The soil physical properties supporting nitrate leaching as 56%,4.49%,8.58%and 4.49%total area have sand（above 35gm/100gm）,porosity（more than 53cm3/100cm3）,bulk density（above 1.2gm/cm3）and soil layer depth（less than 100cm）respectively.Similarly chemical properties as 75.15%,55.14%,57.52%and 1.3%total area have the pH7.0 to 8.5,CEC>13me/100gm and total N>0.3gm/100gm respectively.Biochar may be beneficial to control nitrate leaching and enhance soil N retention to increase soil fertility in the many regions in NCP except area with lower soil depth located at southern sides of NCP.Many regions in NCP are already on the threshold level of nitrate leaching under vegetable crop in Shandong province where management measures should be taken to lower down N input,otherwise the situation may get worsen in future. |
