干旱区膜下滴灌农田土壤盐分非生育期淋洗和多年动态

膜下滴灌土壤盐分在生育期和非生育期的累积与淋洗,共同决定了土壤的盐碱化趋势,影响着当地农业的可持续发展。为分析长期膜下滴灌土壤盐分多年动态,于2008—2013年在中国西北干旱区的清华大学-库尔勒生态水文实验基地开展了棉田实验,采集和化验了15 000余个土壤样本,结合SHAW模型模拟,探讨了非生育期冬春灌方式的盐分淋洗效果;基于长期连续观测及理论分析,评估了区域盐碱化趋势。结果表明:冬灌和春灌的盐分淋洗作用明显,冬灌盐分淋洗深度大致为60 cm,效果优于春灌。若膜下滴灌条件下综合采用非生育期冬灌或春灌洗盐,在多年尺度上土壤根区盐分不会出现明显累积,土壤盐碱化趋势可以得到控制。

Soil salt leaching in non-growth period and salinity dynamics under mulched drip irrigation in arid area

Soil salinity trend is affected by both salt accumulation and leaching during the growth and non-growth periods. To explore the long-term salinization trend of farmland under mulched drip irrigation, the experiments were conducted from 2008 to 2013 in a cotton field in Xinjiang province,northwestern China. More than 15 000 soil samples were collected and tested. With Simultaneous Heat and Water model (SHAW),the salt leaching during the non-growth period was studied. Associated with the soil salt distribution and migration study in the growth period in the other companion papers,the salinization trend in the arid area was evaluated. The results indicate that the salt leaching is obvious in both winter and spring flush. The leaching depth of soil salt is approximately 60 cm in winter flush,which is superior to the spring flush. According to the salt leaching during non-growth period in arid area,soil salinization trend can be controlled and salt balance can be maintained when mulched drip irrigation is adopted in growth period. In consideration of irrigation water amount in growth period only,the water use efficiency (WUE) is 0.68 kg·m^-3 and 0.22 kg·m^-3 for mulched drip and flood irrigation,respectively. Even if the leaching water amount in non-growth period (375 mm) is taken into account,the WUE of mulched drip irrigation is 0.42 kg·m^-3 and still higher than the value of flood irrigation. The results show that in arid and semi-arid areas, the soil salinization trend can be controlled and the WUE will be also improved when the mulched drip irrigation in growth period and the salt leaching measures in non-growth period are both adopted.