秸秆覆盖下的夏玉米蒸散、水分利用效率和作物系数的变化

农业用水占华北水资源的70%以上,提高农业用水的效率对华北水资源安全具有重要意义。在节水农业研究中,利用农艺节水提高农田水分利用效率是节水农业的重要组成部分,其中减少农田无效棵间蒸发耗水和优化供水制度是主要的农艺节水措施。夏玉米是华北太行山山前平原的主要作物之一,一般在冬小麦收获前的5～7天套种在其中,以延长夏玉米的生育期。随着联合收割机的广泛应用,冬小麦收获后的秸秆直接覆盖夏玉米,对夏玉米的农田蒸散特别是苗期的蒸散产生影响;夏玉米生长在6～9月的雨季,一般年份降水能够满足夏玉米的需水要求,但夏季降水的分布变异较大,再加上近6年来的夏季干旱,使灌水对夏玉米的高产至关重要。为了提高夏玉米的农田水分利用效率,本研究的目的是建立秸秆覆盖下的夏玉米优化供水制度和研究秸秆覆盖对减少棵间无效耗水的影响及秸秆覆盖下的夏玉米作物系数的变化,为制定秸秆覆盖下的夏玉米优化供水制度提供依据。2年的实验结果显示,秸秆覆盖下的夏玉米产量在8000kg/ha,总蒸散量在390mm,水分利用效率在2.2kg/m3。干旱年份,夏玉米在灌四水的条件下产量最高,再增加灌水量,产量减少。水分利用效率随着灌水量的增加有所递减。

Evapotranspiration, Yield and Crop Coefficient of Irrigated Maize under Straw Mulch Conditions

Agricultural water use takes up about 70% of the total water consumption in the North China Plain. Thus improvement of the water use efficiency (WUE) in agriculture would play an important role in sustainable water use in the North China Plain. Agronomic water saving measure is one of the most important aspects in water saving agriculture. Reducing soil water evaporation and optimizing irrigation scheduling are effective methods in improving the farmland WUE. Maize is one of the staple crops in the piedmont of Mt. Taihang in the North China Plain and is usually inter planted into winter wheat field about one week before wheat crop is harvested. At harvest, the wheat straw is left to mulch maize crop so as to reduce evapotranspiration, especially during the earlier growth stages. Maize grows during the rainy months of June to September, and the rainfall usually meets its requirement for growth. In dry years or with inter seasonal variability of rainfall distribution, however, irrigation is essential to maintain good maize yield in the region. Due to the fact of a severe shortage of irrigation water in the region, this study aims to examine the effects of numbers of irrigation on maize grain yield, water use efficiency (WUE) and crop coefficient under straw mulch conditions. The results of field trials in the years of 1999 and 2001 showed that total evapotranspiration and WUE of irrigated maize under straw mulch were 390 mm and 22 kg/m 3, respectively, with grain yield of about 8000 kg/ha. Maize yield increased with the irrigation numbers and reached the highest 8834 kg/ha and 8010 kg/ha in 1999 and 2001, respectively, when the irrigation was applied four times over the growing season. Irrigation more than four times, however, caused grain yield reduction in both seasons. In contrast, WUE was only slightly decreased with the increase in the numbers of irrigation. Mulching reduced total soil evaporation by 50 mm in the 2001 season measured by micro lysimeters. At the early growing stage, crop coefficient of maize with mulching was about 05, which was about 50% lower than that without mulching. The coefficient over the growing season with mulch varied between 03~15 with an average of 10.