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

Abstract

Core Ideas SmartIrrigation is a smartphone‐based crop irrigation scheduling method using real‐time and location‐specific (RT‐LS) weather information. The RT‐LS irrigation scheduling method improved irrigation water savings and increased crop yield. The RT‐LS model can reduce nutrient leaching by maintaining water and nutrient within crop root zone. Efficient irrigation scheduling can improve crop performance and increase production efficiencies. 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.