Irrigation Scheduling: A Water Balance Approach to Improve Water Efficiency for South Texas Horticultural Crops

When water resources are limiting, growers need to change to more water conserving methods to raise crops. The purpose of this project was to evaluate the water balance approach as a water scheduling and water saving technique with drip irrigation with plastic, drip without plastic and furrow irrigated watermelon. The water balance approach to irrigation scheduling keeps track of soil water deficit by accounting for all water additions and subtractions from the soil root zone.  Crop water requirements were estimated using a weather station, Penman-Monteith evapotranspiration (ET) equation, and FAO crop coefficients.  Plots were replicated using a completely randomized design with sub-sampling. Irrigation was determined by employing a water balance approach, replacing ET water loss within the drip and furrow irrigated plots.  Sub-surface drip irrigation was compared to irrigating to soil saturation point in furrow irrigated plots.  The furrow system was irrigated without producing runoff by blocking furrows at the lower end of the field.  Harvested watermelon was measured for size and weight to determine produce yield and quality.  The lowest amount of irrigation water used was in the Drip with Plastic treated plots, which resulted in the highest average yield and best overall irrigation use efficiency compared to other systems.