Comparative Assessment of Water Distribution in Constant Versus Variable Rate Irrigation Systems

Abstract

This research explores the effectiveness of a cutting-edge smart irrigation sprinkler system, which boasts an adjustable water distribution feature. Utilizing a technique known as nozzle-pulsing combined with a variable-speed control mechanism, the system is capable of varying its water discharge rates. The evaluation encompassed measuring flow rates for both the system as a whole and its individual nozzles, as well as assessing travel speed and the uniformity and precision in water delivery. Performance metrics such as CU, DUlq, CV, MAE, MBE, and NRMSE were employed to determine the irrigation system's distribution uniformity and application accuracy. Field testing was conducted in the months of August and September 2023, under varying wind conditions with careful timing to reduce evaporative losses. The prevailing weather conditions were characterized by an absence of rainfall, with ambient temperatures ranging from 25 to 38°C and relative humidity spanning 9 to 35%. Results revealed that the system adeptly modulated irrigation rates between 0 to 25 mm and altered travel speeds from 0 to 3 m/min. The implementation of pulsing to deliver variable volumes of water exerted a negligible effect on the nozzle flow rates, evidenced by an average application error below 6%. The smart sprinkler system achieved an average CU of 89.7% versus 83.8%, an average DUlq of 87.0% versus 76.8%, and an average NRMSE of 19.33% versus 25.84%, paralleling the performance of traditional systems. The study concluded that the described Variable Rate Irrigation (VRI) system is capable of matching the precision and consistency of Constant Rate Irrigation (CRI) systems. The water distribution's consistency and precision were found to be statistically unaffected by the sprinkler cycling rate, cycle duration, or system movement speed (P > 0.05). This opens the door to more accurate and consistent irrigation scheduling for agricultural applications using a novel lateral-move irrigation system endowed with VRI technology, which is vital for water-efficient irrigation practices. This finding underscores the potential of variable-rate sprinkler irrigation as a tool to enhance water management strategies.