Plant water accessibility function: A design and management tool for trickle irrigation

Systematic evaluation of different trickle irrigation design and management scenarios must consider the impact of a particular design on crop response at different soils, climatic conditions, and management options. Anecdotal evidence suggests that different emitter arrangements, discharge rates, irrigation amounts, and soil types result in different patterns of crop yield distribution generally decreasing with distance from nearest emitter. We hypothesize that these design and management variables could be incorporated into a plant water accessibility (PWA) function relating characteristic crop yield response as a function of distance to the nearest emitter. A field experiment was conducted to test the hypothesis and estimate the necessary parameters. Field corn was drip irrigated using different combinations of emitter spacing (152 cm × 175 cm, 152 cm × 107 cm, and 152 cm × 61 cm), emitter discharge (3.8 and 1.5 L/h) and irrigation interval (1, 3 and 7 days). Results show that corn dry matter yield remained constant up to certain distance, RE, from the nearest emitter, after which it gradually decreased up to distance RN, where corn yield was no different than for non-irrigated plants. Relationships were established between RE and average amount of water applied per irrigation (R2 = 0.842); and between the reduction zone length (RN–RE) and RE (R2 = 0.879). These relationships were used to evaluate the impact of various design considerations on average corn yield. Simulated values and field observed values were in good agreement, demonstrating the potential usefulness of the proposed PWA function as a design and management tool for trickle irrigation systems.