Variable rate irrigation management for soybean and corn

Variable rate irrigation (VRI) is a new irrigation method developed in precision agriculture. VRI technologies allow the producers to site-specifically apply irrigation water at variable rates within a field to adjust the temporal and spatial variability in soil and plant characteristics. Use of VRI in agricultural production has the potential to improve water use efficiency. Developing VRI practice and documenting the benefits of VRI to producers are critical to accelerate the adoption of VRI technologies. Comparison of VRI with uniform rate irrigation (URI) in soybean and corn crops was studied in Stoneville, Mississippi, USA. A center pivot VRI system was employed for delivering irrigation water. Soil apparent electrical conductivity (EC) of the fields was used to delineate VRI management zones and create VRI prescription. Irrigation was scheduled using soil moisture content measured by soil moisture sensors. Crop yield and irrigation water productivity in VRI treatment was compared to that in the URI treatment. There was no significant difference in yields of soybean and corn between VRI and URI treatments. Compared to URI, VRI treatment saved 25% irrigation water in soybean and 21% irrigation water in corn. Irrigation water productivity (WP) of VRI was 31.2% and 27.1% higher than the URI in soybean and corn, respectively. Results demonstrated that VRI management was superior to the URI in terms of water use efficiency. Soil EC coupled with soil physical properties could be used to establish VRI management zones. Development of novel algorithms with more inputs to site-specifically determine appropriate amount of water to apply is a major challenge facing VRI industry.