Drainage water management effects on energy flux partitioning, evapotranspiration, and crop coefficients of corn

Abstract Over the past 20 years, marketplace demand for corn has prompted many farmers in the Red River Valley (RRV) of the north to include more corn in their crop rotations. With a very flat topography and heavy clayey soils, the RRV can have shallow water tables in the spring and fall but can be dry in the summer. Due to these field conditions, some farmers have installed subsurface drainage (SD) systems with structures for controlled drainage (CD, manage the water table in a field) and subirrigation (SI, add water to the field via the SD system) to improve corn production. In a CD + SI field, an eddy covariance system was used to measure and quantify energy flux components along with soil moisture content (SWC) and water table depth (WTD) measurements during four corn growing seasons in 2012, 2013, 2016 and 2017. The results show that the average SWC in 2012 was significantly different from the other three years. The SWC and WTD in 2016 were more stable compared to the other years. The CD practice had a positive effect during a wet year in 2013, which resulted in 26.7% higher yield than the county average. During the dry growing season of 2017, the use of subirrigation resulted in 6.6% higher yield than the county average. The corn evapotranspiration totals (ETa) were 468, 476, 551, and 537 mm for 2012, 2013, 2016, and 2017 growing seasons, respectively. The average crop coefficients were 0.49, 0.73, 0.88, 0.86, and 0.69 for the initial, development, tasseling, reproductive, and maturity stages, respectively. They were calculated from the daily ETa, values only from days with more than 45% of total available water in the root zone, and the ASCE-EWRI standardized grass-based reference evapotranspiration. This study showed that the SD along with the CD + SI system can be used for optimal water management of field corn during both wet and dry years.