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| DOI：10.13522/j.cnki.ggps.2017.0615 |
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| Estimating the Evapotranspiration of Summer Maize under Sandy Gravel Mulch |
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TANG Dexiu, LI Yi, LIU Feng, FU Yaya, LI Siyi, ZHAO Dan, FENG Hao
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College of Water Conservancy and Architectural Engineering, Northwest A & F University, Yangling 712100, China; Institute of Water-saving Agriculture in Arid Areas of China, Northwest A & F University, Yangling 712100, China; Key Laboratory of Agriculture, Ministry of Education, Northwest A & F University, Yangling 712100, China; Institute of Soil and Water Conservation, Ministry of Water Resources, Chinese Academy of Sciences, Yangling 712100, China;Beijing Woerde Disaster Prevention Green Technology Co.,Ltd., Beijing 100048, China; Sichuan Water Resources and Hydroelectric Investigation & Design Institute, SWHI, Chengdu 610000, China
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| Abstract: |
| 【Objective】 Accurately estimating the evapotranspiration (ETc) is imperative to design irrigation schedule for a catchment, and this paper investigated how the ETc changed in response to mulch with sandy gravels. 【Method】 A shelter experiment was conducted from 2014 to 2016 with the soil mulched with sandy sand at 0, 23, 46 and 69 kg/m2 respectively; the model plant in the experiment was summer maize. The ETc formulae with single and dual crop coefficients were modified to calculate the evapotranspiration, and they were then tested against measured values. The single crop coefficient was calculated by regressing the measured evapotranspiration from a lysimeter to the calculated reference crop evapotranspiration for the four mulches in 2014 and 2015, with the data in 2015 used for validation. 【Result】 The ETcs calculated using the single-coefficient and the dual-coefficient models both agreed well the measured values during all growth stages, with a determination coefficient of 0.782, 0.784, 0.85 and 0.883, and a relative mean root square error of 29.4%, 30.9%, 27.9% and 25.4% respectively for the four gavel treatments, suggesting that the accuracy of the model increased with the amount of gravels. The dual crop coefficient method separated the transpiration from soil evaporation, with the crop coefficient calculated by modifying the FAO-56 using a correction parameter to account for the impact of the gravels. Tests against the 2015 data revealed that the calculated value using the modified methods agreed well with all measurements, with a determination of 0.636, 0.858, 0.87 and 0.932, and a relative root mean square error of 34.8%, 25%, 28.3% and 19.8% respectively for the four treatments. 【Conclusion】 We proposed modified formulae to estimate the evapotranspiration of maize with the soil mulched by sandy gravel; comparison showed that the modelled results agree well with the measured values. |
| Key words: crop coefficient; sandy gravel mulch; summer maize; evapotranspiration; correction coefficient |
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