|YAN, HAIJUN - China Agricultural University|
Submitted to: Journal of Irrigation and Drainage
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2016
Publication Date: 2/11/2017
Citation: Sui, R., Yan, H. 2017. Field study of variable rate irrigation management in humid climates. Journal of Irrigation and Drainage. doi:10.1002/ird.2111.
Interpretive Summary: Soil properties and plant characteristics can vary considerably within a single field resulting in variability of water need for plant to reach its yield potential. Variable rate irrigation (VRI) technology is able to site-specifically apply irrigation water at variable rates within a single field to account for the temporal and spatial variability in soil and plant characteristics. Research on development of methods for VRI management and evaluation of the impact of VRI management on water productivity are needed. USDA ARS Scientist at Crop production Systems Research Unit, Stoneville, MS, working with a collaborator in China, conducted a field study on VRI management for two years in a humid region to compare VRI management with conventional uniform rate irrigation (URI) management. It was found that the VRI management saved 25% irrigation water with slightly higher yield than the conventional URI management. Irrigation water productivity for soybean and corn in the VRI was 24.8% and 27.1% higher than that in the URI, respectively. The crop yield of the rainfed treatment significantly lower than the yield the irrigated crops in a dry year. Results showed the VRI management was able to use irrigation water more efficiently and supplemental irrigation is necessary in the humid region. Results of this study should be useful for development and adoption of VRI technologies for crop production in humid region.
Technical Abstract: Soil physical properties in the Mississippi Delta can vary considerably within a single field resulting in differing water storage capabilities, amounts of water available to the crop, and crop yield potential. Variable rate irrigation (VRI) technologies are able to site-specifically apply irrigation water at varying rates within a field to account for the temporal and spatial variability in soil and plant characteristics. Implementation of VRI has the potential for optimizing water use efficiency and increasing producer’s profits. Comparison of VRI with uniform rate irrigation (URI) in soybean and corn crops was studied for two years in 2014 and 2015 in a USDA-ARS research farm near Stoneville, Mississippi, USA. The experiments were conducted in two 6.7-ha fields. Each field was equally split into two sectors. VRI management was performed in one sector and the URI management in the other. 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 a VRI prescription map. Based on the prescription map, VRI controllers of the center pivot irrigation system adjusted the on/off time of the sprinklers to achieve the desired water application rate at each management zone within the field. 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 and a rainfed treatment. The VRI treatment used 25% less irrigation water and produced 2.8% more yield in soybean and 0.8% more yield in corn than the URI treatment. Irrigation water productivity (WP) of soybean was 0.84 kg/m3 and 0.64 kg/m3 under VRI and URI management, respectively. The WP of corn was 1.69 kg/m3 and 1.33 kg/m3 in VRI and URI, respectively. Yield of the rainfed treatment was significantly lower than VRI and URI treatments for both soybean and corn in 2015 season (p < 0.05). Results in this study 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 site-specific management zones for VRI practice. The VRI management method will be evaluated for more seasons, and the VRI prescriptions will be refined by including more inputs such as real-time plant water stress and plant health index.