地膜残留量对新疆棉田蒸散及棵间蒸发的影响

为探讨残膜对干旱区农田蒸散耗水特征的影响,在新疆阿克苏典型覆膜滴灌棉田开展2 a小区试验研究,设计0、225、450 kg/hm2共3种不同的地膜残留量,采用水量平衡法,微型棵间蒸发仪法,于主要生育时期测定并计算土壤含水量、蒸散量、棵间蒸发量、作物蒸腾量、棵间蒸发占蒸散的比例。结果表明:随着地膜残留量增加棵间蒸发量、棵间蒸发占蒸散的比例呈增大趋势,而蒸散量及作物蒸腾量则逐渐减小。与无残膜处理相比,225和450 kg/hm2处理全生育期田间无效耗水的棵间蒸发量分别增加了9.27和22.20 mm,棵间蒸发占蒸散的比例增幅分别为2.6%和6.1%,作物蒸腾量降低34.89和55.94 mm。在棉花生育期内,棵间蒸发占蒸散的比例(E/ET)与叶面积指数(leaf area index,LAI)呈幂函数关系,各处理间棵间蒸发占蒸散的比例对叶面积指数的响应差异不同,450 kg/hm2处理蒸发占蒸散的比例随着LAI的增加,曲线下降趋势较明显;无残膜处理棵间蒸发占蒸散的比例与LAI的决定系数最高,均在0.9以上。土壤水分利用率也随残膜量的增加依次降低,当残膜量由0增加到450 kg/hm2时,土壤水分利用率从28.25%降至24.91%,可见,残膜增大了农田的无效耗水,不利于土壤水分的有效利用。研究可为制定缓解或克服残膜危害的应变调控技术提供依据。

Effects of plastic film residue on evapotranspiration and soil evaporation in cotton field of Xinjiang

Plastic film mulching plays an important role in cotton production. However, its widespread use has generate large amounts of plastic film residue and damage the physical structure of soil, which blocks the infiltration of capillary water and natural water and affects the moisture absorption in soil. Little is known about the impact of film residue on crop evapotranspiration (ETc), and soil evaporation and transpiration. This study aimed to determine the effects of different amount of plastic film residue on ETc using weighable micro-lysimeters (MLS) and water balance methods. A cotton cultivation field experiment was carried out under drip irrigation with plastic film mulching for 2 growing seasons from May to September of 2014 and 2015 in the Tarim Basin, Northwest China (40°06′N, 80°44′E, altitude 1 025 m). Three treatments including plastic film residue amount of 0, 225 and 450 kg/hm2 were designed based on investigation of typical cotton field representing local present situation. Eighteen MLS were buried in soil at 0.15 m depth in each treatment with soil volume of 1424.8 cm3. Soil moisture and evaporation were measured, and ETc, transpiration and ratio of evaporation and ETc were calculated. In addition, leaf area index (LAI) was determined. Resulted showed that the mean evaporation and ratio of evaporation and ETc increased with the increase of residual plastic film amount, which revealed a different trend with the transpiration and ETc. During the whole growing period, residue addition of 225 and 450 kg/hm2 significantly increased the soil evaporation by 6.2%and 14.9% and decreased transpiration by 34.89 and 55.97 mm compared to no film treatment, respectively. The transpiration and ETc were reduced by 3.4% and 4.5% in the entire growing season. Increasing plastic film residue could decrease soil water use efficiency. The increase in soil evaporation in the residual treatment probably is because that the film blocks moisture transportation downward after rainfall and irrigation and the moisture left in surface soil is evaporated. However, soil moisture in no residue treatment could infiltrate to below surface and thus the evaporation was smaller than the residual treatments. Among the 3 treatments, the soil water use efficiency was lowest in the no residue treatment. The relationship between E/Etc partition coefficient and LAI could be described by a power function. The ratio of evaporation and ETc decreased greatly with the increase of LAI in the treatment of 450 kg/hm2 residue. In sum, residual plastic film could change structure of crop water consumption, and this study could provide valuable information for well understanding effects of residual film in soils.