Evapotranspiration from Maize Studied Using Weighing Lysimeters

Abstract

【Objective】 Evapotranspiration is important not only as a component of the hydrological cycle but also for its role in modulating crop growth. The purpose of this paper is to measure the evapotranspiration of spring maize using weighing lysimeters and analyze its relationship with the yield and water use efficiency of the crop. 【Method】 A two-year experiment was conducted in Shanxi province from 2019 to 2020, and the evapotranspiration of spring maize under different water supplies was measured using weighing lysimeters. We compared four irrigation schedules: irrigating 5 times (T1), 6 times (T2), 4 times (T3) and 2 times (T4), with irrigation amount in all them being kept at 60cm. The irrigations differed only in the criteria set to resume irrigation, judged by a critical soil moisture measured in situ. Hourly changes in soil water content in all lysimeters were recorded automatically, and daily evapotranspiration was calculated using the water balance method, from which we further analyzed the relationship between yield and evapotranspiration. 【Result】 The evapotranspiration rate peaked in the middle of growing season in all treatments, and the daily evapotranspiration rate in all growing stages increased with the irrigation amount. In T2, the maximum evapotranspiration rate was 0.44 mm/h occurring at 13:00 pm, while in T4 it was reduced to 0.175 mm/h occurring at 09:00 am. The legacy of the effect of irrigation scheduling on evapotranspiration lasted a few days following the irrigation. The more frequently the crop was irrigation, the more the water would be evaporated or transpired. Most soil water was lost via evapotranspiration in the middle growth stage, i.e., 52 to 120 days after drilling the seeds; the maximum daily evapotranspiration during this period was 10.68 mm/d in 2019 and 7.27 mm/d in 2020, accounting for 75.7% and 72.9% of the total evapotranspiration in each of the two years, respectively. Model using relative evapotranspiration to predict the crop yield gave a good fitting with a correlation coefficient R2 > 0.99. Further verification of the model against data measured from 2018 to 2020 from a spring maize field in Wenyu River Basin proved the robustness of the model with a correlation coefficient R2 >0.94. 【Conclusion】 Evapotranspiration measured from the weighting lysimeter was accurate and can be used to predict yield and estimate soil water change.

Keywords

• weighting lysimeter
• evapotranspiration
• water balance
• corn yield
• relative evapotranspiration