| Hetao Plain and the Northern Yinshan,Inner Mongolia are the main production areas of maize and potato.Farmers in these regions applied a large amount of fertilization and irrigation for pursuiting high yields.However,overuse of nitrogen fertilizer and irrational irrigation easily cause the leaching loss of nitrogen fertilizer.In this study,the soil samples of different textures using different nitrogen fertilizers were collected in these two regions and the indoor soil column simulation experiments were conducted to explain the leaching losses and transformation low.The leaching amount of sandy loam is significantly higher than that of clay soil as the amount of irrigation is kept at 65% of the maximum water holding capacity.In terms of the clay soil,the double peaks appeared in the concentration of nitrate in leachate with the addition of synergistic urea treatment and normal urea treatment.The double peaks occurred on 7th day after firstly and the values were 9.3 mg/L and 130.9 mg/L respectively.The second one occurred on 21 st and 35 th days after,and the values were 18.9 mg/L and 102.3 mg/L,individually.Since then,they were basically stable at the value of 1.3-1.9 mg/L.For sandy loam soil,the nitrate nitrogen concentration in the leachate with the addition of synergistic urea and common urea reached the maximum in the leach solution on 7th day,the value was 109.4 mg/L and 192.2 mg/L,respectively.We found that Nitrogen is intermittently converted.Nitrate leaching concentrations of urease inhibitors were significantly reduced in different soils.In sandy loam soil,the addition of synergistic urea treatment reduced nitrate nitrogen leaching losses by 7.6 mg/column compared to normal urea treatment.In clay,addition of synergistic urea treatment resulted in a reduction of 15.6 mg/column for nitrate nitrogen leaching loss compared to normal urea treatment.Wheras,the ammonium sulfate leaching loss is relatively low in comparison.Nitrification inhibitors can significantly reduce the leaching of nitrate.In clay,just like urea treatment,add ammonium sulfate treatment and ordinary ammonium sulfate treatment.There is a double peak in the concentration of nitrate in the solution.The peak value occurred on the 7th day firstly with the peaks value of 7.1 mg/L and 46.4 mg/L.The second one occurred on the 63 rd and 42 nd dayswith peak values of 11.2 mg/L and 81.4 mg/L,respectively.Since then they were basically stable at 0.6-48.9 mg/L.In sandy loam soil,the nitrate nitrogen concentration in soil column solution with ammonium sulphate and normal ammonium sulfate was reached the highest.The concentration of nitrate in the leach solution reached the maximum of 40.7 mg/L on the 7th day and nd 169.0 mg/L,then stabilized at 0.1-5.9 mg/L.The ammonium nitrogen leaching loss is relatively low in sandy loam and clay.In the soils with different textures,the nitrate leaching concentration after addition of nitrification inhibitors was significantly reduced.In sandy loam soil,the addition of ammonium sulphate treatment was 13.3 mg/column nitrate nitrogen lower than that of normal ammonium sulphate treatment.And the leaching loss of clay with the addition of ammonium sulfate treatment was reduced 2.8 mg/column nitrate nitrogen leaching loss compared to normal ammonium sulfate treatment.Whether it is clay or sandy loam,both the two inhibitors can reduce nitrogen leaching losses.The urease inhibitors effectively inhibit urea hydrolysis.While the Nitrification inhibitors inhibite the conversion of ammonium nitrogen to nitrate nitrogen.On the whole,the loss of leaching of clay is less than that of sandy loam.And the inhibitory effect of ammonium sulfate is better than that of urea.In the field,inhibitors can be used to an effective means for reducing nitrate leaching losses. |
