Aquacrop模型在北疆棉花生育期灌溉洗盐制度优化中的适用性

    Applicability of the Aquacrop model in optimization of irrigation and salt leaching schedule during the reproductive period of cotton in Northern Xinjiang of China

    • 摘要: 为明确Aquacrop模型在北疆棉田膜下滴灌和地下滴灌方式下生长和生产模拟的适用性,并探究棉田生育期最优灌溉洗盐制度,该研究以2020和2021年的田间试验数据对模型参数进行校正和验证,并用校正好的模型揭示3种灌溉水平(100%ETc、80%ETc、60%ETc,其中ETc为作物需水量)、3种淋洗总定额(0、120和240 mm)、3种灌水频率(5、7和10 d/次)和3种降水年型(湿润年、平水年、干旱年)对棉花产量和灌溉水生产力的影响。结果表明,2021年所有处理的冠层覆盖度、地上生物量归一化均方根误差(normalized root mean square error, NRMSE)不大于20.998%,一致性指数d≥0.967,决定系数R2≥0.914,产量均方根误差(root mean square error, RMSE)、NRMSE、dR2分别为0.389 t/hm2、6.797%、0.836和0.754,模型整体模拟效果良好。基于58 a气象数据的模型模拟表明:灌溉水平、淋洗定额、降水年型对棉花产量和灌溉水生产力的影响显著,灌水频率的影响不显著;在平均土壤含盐量范围为12~18 g/kg的植棉区域,综合考虑产量、灌溉水生产力及实际生产情况,湿润年推荐80%ETc+120 mm的灌溉淋洗总定额,平水年和干旱年推荐100%ETc+120 mm的灌溉淋洗总定额;推荐延长灌水频率至10 d/次以减少灌水次数,节约成本。研究可以为Aquacrop模型在棉田中的应用积累经验,为农业水资源高效利用提供理论指导与技术支撑。

       

      Abstract: China's most fabulous cotton-producing area is Xinjiang. In Xinjiang, soil salinization and water shortage are now the two key challenges limiting agricultural productivity and sustainable growth. Water wastage and secondary soil salinization in the area are still being made worse by irrational irrigation during the growth period and salt leaching during the off-growing period. A breakthrough in solving these problems is the development of sensible irrigation and salt-leaching techniques throughout the growing period to preserve water efficiently, cut expenses, and guarantee cotton crop yields. Following calibration of the model parameters and validation using field experiment data from 2020 and 2021, respectively, the optimal scheduling of cotton field irrigation and salt leaching was investigated to clarify the applicability of the Aquacrop model to the growth and production of simulated cotton fields under membrane and subsurface drip irrigation in northern Xinjiang. Then the calibrated model was used to reveal the effects of three irrigation levels (100%ETc (D1), 80%ETc (D2), and 60%ETc (D3)), three salt leaching amounts (0 (Q1), 120 mm (Q2), and 240 mm (Q3)), three irrigation frequencies (5 (F1), 7 (F2), and 10 d/time (F3)) and three types of precipitation year (rainy years(H1), normal years (H2), and dry years (H3)) on cotton yield and irrigation water productivity. The results showed that canopy cover, aboveground biomass NRMSE (Normalized root mean square error)≤20.998%, d (Index of agreement)≥0.967, and R2 (Coefficient of determination)≥0.914 for all treatments in 2021, and yield RMSE, NRMSE, d, and R2 were 0.389 t/hm2, 6.797%, 0.836, and 0.754, respectively, and the model simulated well overall. Model simulations based on 58 years of meteorological data showed that the effects of irrigation level, salt leaching quota, and precipitation year type on cotton yield and irrigation water productivity were statistically significant, and irrigation frequency effect was not significant; in the cotton planting area with average soil salinity ranging from 12 to 18 g/kg, accounting for yield, irrigation water productivity, and actual production, the total irrigation and salt leaching quota of 80% ETc+120 mm (D2Q2) was recommended for rainy years, and the total irrigation and salt-leaching quota of 100% ETc+120 mm (D3Q2) was recommended for both normal and dry years; it was suggested that the irrigation frequency be increased to 10 d/time to reduce the frequency of irrigation and save costs. The optimal irrigation and salt leaching strategy proposed in this study was limited by model function and evaluation perspective. It was based on water conservation and optimal yield in cotton fields and did not consider the desalination conditions of membrane and subsurface drip irrigation. To develop more rigorous and convincing irrigation and salt leaching strategies, the Aquacrop model must be coupled with other water and salt transport models to improve the model's functionality and comprehensively assess soil desalination and cotton field production conditions.

       

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