Evaluation of the Dual Crop Coefficient Approach in Estimating Evapotranspiration of Drip-Irrigated Summer Maize in Xinjiang, China

A dual crop coefficient approach was validated experimentally to estimate evapotranspiration of drip-irrigated summer maize with partial mulch and no mulch in an arid region in Aksu, Xinjiang, China, during 2016–2017. In this study, five treatments were established based on fixed or variable irrigation cycles. Summer maize transpiration and evapotranspiration were estimated by the dual crop coefficient approach. Evapotranspiration was validated, and a positive regression with those values was obtained using the water balance method, with a root mean square error (RMSE) of 10 mm. The estimated transpiration also had a positive regression with measurements obtained by the stable carbon isotope technique, with a RMSE of 20 mm. By analyzing the RMSE, regression coefficients, and concordance index, we suggest that the dual crop coefficient approach is an effective method to estimate and partition evapotranspiration. Across the entire growing season for partially mulched summer maize, the estimated crop transpiration accounted for 78.7% and 76% of the total evapotranspiration in 2016 and 2017, respectively. For non-mulched summer maize, the estimated crop transpiration accounted for 64.9% of the total evapotranspiration over the entire growing season, which implied that the soil evaporation was about 12% higher than that of the partially mulched treatments. Water consumption with partial mulching was reduced by about 10%, compared with non-mulching, which indicated that mulching improved the use of water during irrigation.

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Effects of shallow water table on capillary contribution, evapotranspiration, and crop coefficient of maize and winter wheat in a semi-arid region

Australian Journal of Agricultural Research ◽

10.1071/ar99177 ◽

2001 ◽

Vol 52 (3) ◽

pp. 317 ◽

Cited By ~ 17

Author(s):

Shaozhong Kang ◽

Fucang Zhang ◽

Xiaotao Hu ◽

Peter Jerie ◽

Lu Zhang

Keyword(s):

Winter Wheat ◽

Water Table ◽

Arid Region ◽

Crop Coefficient ◽

Growing Season ◽

Groundwater Table ◽

Summer Maize ◽

Semi Arid Region ◽

Crop Coefficients ◽

Semi Arid

A lysimeter experiment was conducted during 19866—96 to study the impacts of groundwater tables on the capillary contribution, evapotranspiration, and crop coefficient of maize and winter wheat grown in a semi-arid region in loess loam soils. The depth of groundwater table was set to 0.5, 0.8, 1.0, 1.2, 1.5, 2.0, and 2.50 m, respectively. The results showed that the rate of capillary contribution from groundwater to crop root-zone was influenced mainly by the depth of the water tables. The daily variation in capillary contribution was not the same as pan evaporation; the peak was delayed when the water table was >0.8 m, and the time of delay increased with the depth of water table. The crop evapotranspiration was decreased with increasing groundwater table in the early growth period and harvest period. The maximum evapotranspiration occurred at 1.2 m groundwater table in the other periods. Values of crop coefficients (K c ) were estimated based on the measured evapotranspiration (ET) and reference crop ET computed by the modified Penman method. The estimated K c was significantly different from the values computed and used in the region in the absence of groundwater table effects, and it varied markedly with groundwater tables. Relationships between the crop coefficient and the depth of groundwater table were developed using mean crop coefficients derived from multi-year data. It was found that linear model was better for the period Octobermp;mdash;February in the winter wheat growing season and June in the summer maize growing season. The polynomial model was suitable for the period March;mdahs;June in the winter wheat growing season and from July to October in the summer maize growing season.

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