基于CROPWAT-DSSAT关中地区冬小麦需水规律及灌溉制度研究

明确关中地区作物需水规律可为合理制定灌溉制度提供理论前提,从而为合理开发和高效利用农业水资源提供帮助。该文基于CROPWAT-DSSAT模型模拟分析了关中地区近30年来冬小麦生长季期间的有效降水量、作物需水量等季节变化特征,并模拟不同降水年型不同灌溉制度下作物产量的变化趋势,分析了多次灌水对产量及经济效益的影响,以确定不同降水年型下的最优灌溉方案。结果表明:关中地区冬小麦生长季期间有效降水量不足其需水量的50%,不同降水年型的季节特征有所不同,总体表现为越冬及返青拔节期缺水较为严重。冬小麦生长期间,越冬水、返青水、拔节水及灌浆水4水中以返青水最为关键,其次为拔节水,灌浆水对产量的贡献作用最小;丰水年、平水年、枯水年冬小麦最佳灌溉定额分别为75 mm、125 mm及150 mm;枯水年需在越冬期、返青期和拔节期分别灌水25 mm、75 mm和50 mm,此时冬小麦产量和经济收益均最高;平水年需在越冬期、返青期、拔节期分别灌水50 mm、50 mm和25 mm,此时冬小麦产量最高,越冬水灌溉量减半后经济效益最高;丰水年则需在越冬期、返青期和拔节期均灌溉25 mm为宜,此时冬小麦产量和经济效益均最高。

Water requirement and irrigation systems of winter wheat: CROPWAT-DSSAT model solution in Guanzhong District

Definitive regulation of winter wheat water requirement is critical for developing theoretical bases for rational irrigation systems with high agricultural water use efficiency in Guanzhong District. To develop time-variant optimal irrigation schemes, a simulation of seasonal characteristics of a range of variables (e.g., effective rainfall, crop water requirement, etc.) was conducted for the winter wheat growth seasons in the last 30 years in Guanzhong District. An integrated CROPWAT-DSSAT model was used to simultaneously simulate the changes in crop production and water stress under different irrigation schemes in different precipitation years. The optimal irrigation schemes were determined according to effects of irrigation on crop yield and economic benefits. Based on the results, the amount of effective rainfall was less than 50% of water requirement during winter wheat season. Seasonal characteristics were different across different precipitation years; which phenomenon induced severe water shortages during wintering, greening and jointing stages of winter wheat. Among the four investigated irrigation stages, which were wintering, greening, jointing stage and grain-filling stages, water for greening was most critical for winter wheat growth. This was followed by water for jointing, while grain-filling irrigation was least critical for winter wheat production. Abundance analysis suggested that optimal total irrigations in wet years, normal years and dry years were 75 mm, 125 mm and 150 mm, respectively. For detail, irrigation scheme suggested that water for wintering was the critical in wet years. For maximum yield and economic benefit of winter wheat, water for winter, greening and jointing were all noted to be no less than 25 mm in wet years. For normal years, waters for wintering, greening and jointing were 50 mm, 50 mm and 25 mm respectively. These water quotas gave the highest yields of winter wheat. However, halving the amount of water for wintering optimized the economic benefit of winter wheat. Similarly, waters for wintering, greening and jointing in dry years were 25 mm, 75 mm and 50 mm, respectively. These were the water quotas that produced the highest yields and economic benefits for winter wheat in Guanzhong District.