秸秆还田条件下氮肥用量对稻田氮素淋失的影响

通过田间小区试验,研究了秸秆还田条件下不同氮肥用量对稻田田面水、渗漏水中氮素动态变化和淋失量的影响.结果表明,稻季秸秆还田量为6t/hm2,氮肥用量分别为0,120,180,240,300kg/hm2时,稻季田面水、渗漏水中无机氮(NH4+-N与NO3--N)浓度随氮肥用量的增加而显著增加,秸秆还田显著降低田面水和渗漏水中NH4+-N和NO3--N浓度;田面水中NH4+-N浓度在每次施肥后的第2d、NO3--N在第2~4d达到峰值,渗漏水中NH4+-N在每次施肥后的第2~4d, NO3--N在施基肥后的第20d左右达到峰值;不同处理田面水中NH4+-N、NO3--N的平均浓度及变幅分别为1.23±0.88(0.01~9.89)、1.14±0.18(0.14~2.86)mg/L,渗漏水中分别为1.78±1.60(0.03~22.66)、1.42±0.24(0.22~2.66)mg/L.稻田渗漏量与水稻移栽后天数呈极显著负相关,整个水稻生育期内的总渗漏量为298mm.不同施氮处理稻季NH4+-N、NO3--N的平均净淋失量分别为4.77±4.37 (0.45~12.33)、1.76±1.08(0.49~3.31)kg/hm2,占施氮量的2.57%~4.11%、0.41%~0.56%,氮素损失以NH4+-N为主.

Effects of nitrogen fertilizer application rate on nitrogen leaching in paddy field incorporated with straw

A field experiment was conducted to investigate effects of nitrogen fertilizer application rate in paddy field incorporated with straw on nitrogen in surface- and percolating-waters and its losses with the waters. It was designed to have 5 treatments in N fertilizer application rate, i.e. 0, 120, 180, 240 and 300kg/hm2, and all the plots incorporated with 6t/hm2 of straw. Results show that the concentration of inorganic nitrogen (NH4+-N and NO3--N) in the surface- and percolating-waters increased significantly with increasing nitrogen application rate, while the concentrations of NH4+-N and NO3--N were reduced significantly in the surface- and percolating-water by straw incorporation. The concentration of NH4+-N in the surface-water peaked on the next day after each nitrogen application, where the concentration of NO3--N in the surface-water did on the 2ed to 4th day after each fertilization, and the concentration of NH4+-N in leachate did on the 2ed to 4th , of NO3--N on the 20th day after basal fertilization. The average concentration and the variation range of NH4+-N and of NO3--N in the surface water of the 5 treatments was 1.23±0.88(0.01~9.89)and 1.14±0.18(0.14~2.86)mg/L, respectively, and that in the leachate was 1.78±1.60(0.03~22.66)and 1.42±0.24(0.22~2.66)mg/L, respectively. In the paddy field, leakage was in a highly significant negative correlation with the elapse of the time after rice transplanting, and the total leakage was 298 mm during the rice growing stage. The net average loss of NH4+-N and NO3--N with leachate of all the fertilization N treatments was 4.77±4.37 (0.45~12.33) and 1.76±1.08 (0.49~3.31) kg/hm2, accounting for 2.57%~4.11% and 0.41%~0.56% of the N fertilizer applied, respectively. And NH4+-N was the main form of nitrogen leaching loss.