长期咸水滴灌对棉花产量、土壤理化性质和N_2O排放的影响

Effects of Drip Irrigation with Saline Water on Cotton Yield, Soil Physical and Chemical Properties, and Soil N_2O Emission

通过田间试验研究了咸水微咸水滴灌对棉花产量、土壤理化性质及N2O排放的影响。试验设置3种灌溉水,盐度(电导率,EC)分别为0.35、4.61、8.04 dS·m-1(分别代表淡水、微咸水和咸水);同时,设置0、360 kg·hm-2(360 kg·hm-2为当地棉田推荐氮肥用量)2个施氮水平。结果表明:灌溉第一年,微咸水处理的棉花产量最高,分别较淡水和咸水处理高出了6.50%和22.46%;随灌溉年限的增加,棉花产量随灌溉水盐度的增加而显著降低,咸水灌溉显著抑制棉花产量。土壤含水量、电导率、铵态氮含量随灌溉水盐度的增加而增加,土壤pH、全氮、有机质、硝态氮含量则随灌溉水盐度的增加而减小;咸水和微咸水灌溉显著抑制土壤硝酸还原酶、亚硝酸还原酶活性,施用氮肥可提高酶活性;土壤N2O排放通量随灌溉水盐度的增加显著降低,施氮肥促进了土壤N2O的排放,土壤N2O排放通量与土壤有机质、铵态氮、硝态氮、硝酸还原酶和亚硝酸还原酶活性呈显著正相关,与土壤含水量呈显著负相关,而与土壤pH、电导率和全氮无相关性。

This field study was conducted to investigate the effects of irrigation water salinity and N application rates on cotton yield, soil physical and chemical properties, and soil N2O emission. The experiment included three levels of irrigation water salinity：0.35, 4.61, and8.14 dS·m^-1, referred as fresh water, brackish water, and saline water, respectively. The N application rates were 0 and 360 kg·hm^-2（a commonly used rate by local farmers）. In the first year of the study, cotton yields were highest in the brackish water treatment, 6.50% higher than in the fresh water treatment and 22.46% higher than in the saline water treatment. In the subsequent years, cotton yields decreased with increasing irrigation water salinity. As irrigation water salinity increased, soil moisture, soil salinity, and soil NH＋4-N concentrations increased significantly, but soil pH, organic matter contents, total N concentrations, and NO-3-N concentrations decreased. Irrigation with either brackish or saline water significantly reduced activities of soil nitrate reductase and nitrite reductase, whereas applying N fertilizer promoted their activities. Soil N2O emission was significantly decreased by irrigation with salt-containing water. On the contrary, it was increased by N application. Soil N2O emission was correlated positively with soil organic matter, NH4^＋-N, NO3^--N, nitrate reductase activity,and nitrite reductase activity, but negatively with soil moisture. Soil pH, soil salinity, and total soil N had no significant effects on N2O emissions.