灌溉模式与施氮水平对土壤渗滤液氮浓度动态变化的影响

Effects of irrigation patterns and nitrogen levels on the dynamic changes of nitrogen concentration in percolation water in a paddy field

以Ⅱ优838为水稻供试品种,湖北潮土为供试土壤,通过2年稻麦轮作柱栽试验研究2种灌溉模式(FW:土表淹水3cm;CW:保持土壤湿润但土表不积水)和4个施氮水平(N0:0kg·hm-2,N1:126.0kg·hm-2,N2:157.5kg·hm-2,N3:210.0kg·hm-2)对水稻土渗滤液不同形态氮浓度变化动态的影响。结果表明:土壤渗滤液的总氮浓度随水稻生育期推移呈由高到低的变化趋势,氮素淋失风险主要存在于水稻移栽后的前40d左右;在稻麦轮作制中,前作小麦明显提高后作水稻土壤渗滤液氮浓度;硝态氮(NO3--N)和可溶性有机氮(SON)是土壤渗滤液氮素的主要形态,铵态氮(NH4+-N)所占比例较低;水稻移栽后20～30d左右出现土壤渗滤液NO3--N高峰,在高峰期土壤渗滤液的NO3--N浓度随施氮量增加而提高;减氮25%处理(N2)相对于常规施氮量处理(N3)显著提高氮肥利用率,并降低氮素淋失风险。

A two-year pot experiment was conducted to investigate the effects of irrigation patterns and nitrogen （N） fertilizer levels on N leaching in paddy soils in a rice-wheat rotation cropping system. The experiment was designed with four levels of N fertilizer rates of NO, N1, N2, and N3 （0, 126, 157.5, and 210 kg. hm-2 , respectively） in two irrigation patterns （FW： flooding water to a depth of 3 cm above soil surface and CW： keeping soil moisture but not ponding at soil surface）. The rice variety II You 838 and alluvial soils from Hubei Province were used in this experiment. The results showed that the concentration of total N （TN） in percolation water decreased gradually during the rice growing season, and the risk of N leaching loss mainly appeared on the 40th day after transplanting. NO3--N and soluble organic nitrogen （SON） were the major forms of N in soil percolation water, while NH4 ＋-N had a lower proportion compared with NO3--N and SON. The concentration of NO3--N reached the highest level during the 20th day to 30th day after transplanting, and the concentrations of NO3--N in soil percolation water increased as the N level increased during this period. Compared to N3 （local recomrnendation dosage）, the N2 treatment （75% of N3） under both irrigation patterns significantly increased the nitrogen use efficiency （NUE） and decreased leaching loss of N.