Evaluation of Soil Water and Nitrogen Distribution by Site-Specific Irrigation Scheduling Method in Tomato Crop Grown on Sandy Soil.

Irrigation scheduling based on a real-time and location-specific (RT-LS) model increases irrigation water savings and yield. The RT-LS irrigation scheduling models have been developed as smartphone applications and have been used for crop-specific irrigation requirements. Although many RT-LS irrigation models have been tested and used in several agronomic and horticultural crops in Florida, none of these irrigation-scheduling models has been tested for their impacts on nutrient distribution in Florida’s sandy soils. A two-season (fall 2015 and spring 2016) study was conducted to determine the effects of an RT-LS–based irrigation scheduling on soil water, NO3-–N, and NH4+–N distributions during a tomato cropping season. In both seasons, an RT-LS model for tomato was evaluated at three irrigation application rates (66, 100, and 150% RT-LS–suggested amounts) and compared with a historic evapotranspiration (ET)-based irrigation schedule (Historic ET) currently recommended in Florida. This study suggests that the RT-LS model improves water savings by 20 and 17% for the fall and spring seasons, respectively, compared with the Historic ET irrigation scheduling method. No specific pattern was observed for soil NH4+–N concentration between scheduling methods, but the RT-LS model maintained a higher soil NO3-–N concentration within the crop root zone and hence could reduce NO3-–N leaching potential. In each season, compared with the Historic ET irrigation method, the RT-LS improved both nitrogen recovery and irrigation water use efficiency in the open-field fresh-market tomato production system. Results obtained in this study clearly demonstrate that irrigation applications using the RT-LS irrigation scheduler improved irrigation scheduling accuracy by maintaining nutrients within the tomato root zone and hence could reduce nutrient leaching potential in sandy soil. [ABSTRACT FROM AUTHOR]