The effects of microdrip and conventional drip irrigation on water distribution and uptake

Drip irrigation at a rate close to plant water uptake necessitates low application rates (microdrip), which affect soil water regime and plant response. This study compare the effect of three emitter discharges, 0.25, 2.0, and 8.0 L h(-1), on different aspects of the water regime in daily drip irrigated corn (Zea Mays L.), relying on field observations and numerical simulations. Field observations show that microdrip irrigation (i) tends to increase yield although this was not statistically significant under the experimental conditions; (ii) induces higher relative water content values in the 0- to 0.30-m depth layer, and lower ones in the 0.60- to 0.90-m layer. Numerical simulations, carried out using HYDRUS-2D, show that microdrip irrigation led to the smallest wetted volume with the least extreme water content gradients both in the horizontal and the vertical axes. A saturated zone below the emitter was obtained only for the 8.0 L h(-1) discharge. Comparing water content distributions with depth at the end of the application of the same amount of water close to the emitter, the driest profile is obtained for the lowest application rate. However, when compared at solar noon representing the time of the highest plant water demand, the upper 0.20-m layer of the soil irrigated at the lowest rate was the wettest. Microdrip irrigation has reduced the dynamic changes in the water content during the day in the most active part of the root zone. It also caused the smallest reduction in the simulated water uptake relative to the potential value.