氮肥对水稻不同生长期土壤不同深度氮素渗漏的影响

Effect of Fertilizer N on N Leaching at Different Soil Depths During Growth Periods of Rice

为了探明太湖地区氮肥施用对水稻不同生长期稻田土壤氮素渗漏的影响,利用渗漏管进行了原位监测。结果表明:①土壤各层(20～40、40～60、60～80和80～120 cm)渗漏液中铵态氮(NH4+-N)的平均浓度在水稻分蘖期较高,而硝态氮(3NO--N)和全氮(TN-N)的平均浓度则在苗期相对较高。渗漏液中NH4+-N和TN-N浓度随土壤深度增加基本呈降低趋势。②以土壤80～120 cm深处渗漏量为进入地下水的氮素渗漏量,发现TN-N渗漏量占施肥量的比例为1.69%～2.04%。分蘖期的NH4+-N渗漏量相对较多,而苗期3NO--N和TN-N相对较多,总TN-N渗漏量中NH4+-N和3NO--N基本无差异。③氮肥用量增加降了氮肥利用效率,加剧了土壤各层氮素渗漏风险。当施氮量由N 200增至270 kg/hm2时,氮肥表观利用率下降7.14%,下渗至地下水中的TN-N增加12.3%。

An in-situ observing experiment was carried to understand the effect of N application on N leaching of various depth of soil during different period of rice growth.The results showed 1） rice tillering stage had relatively higher averaged concentration of ammonium nitrogen （NH4＋-N） in percolation water collected from soil depths of 20-40,40-60,60-80 and 80-120 cm.But nitrate nitrogen （NO3--N） and total N （TN-N） had relatively higher averaged concentrations during seedling stage and showed gradually decreased trend with soil depths; 2） the amount of TN-N percolated in 80-120 cm soil depth accounted for 1.69％-2.04％ of N application rate which could presented the amount of N percolated into groundwater.Relatively higher amount of NH4＋-N percolation happened during tillering stage.However,higher amounts of NO3--N and TN-N happened during seedling stage.The amounts of NH4＋-N and NO3--N showed parallel level in TN-N percolated from soil; 3） increased N application rate decreased fertilizer N use efficiency and accelerated risk of N percolation in soil.