Submitted to: Journal of Agricultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2015
Publication Date: 10/15/2015
Citation: Sui, R., Fisher, D.K., Reddy, K.N. 2015. Yield response to variable rate irrigation in corn. Journal of Agricultural Science. Vol. 7(11):11-18.
Interpretive Summary: In the last decade, farmers in the Mid-South have shifted their land from other crops such as cotton, to corn and soybean, increasing corn acreage dramatically. Uncertainty in the amount and timing of precipitation becomes one of the most serious risks to producers in the Mid-South. Supplemental irrigation in this humid region is necessary to increase crop yield and reduce crop production risk. Research on crop water management is required for high yield and net returns. USDA ARS Scientists at Crop production Systems Research Unit, Stoneville, MS conducted experiments using variable rate irrigation (VRI) technology to investigate the effects of supplemental irrigation on corn yield in the Delta of Mississippi. Corn grain yields from five irrigation rate treatments (0, 50%, 75%, 100%, and 125% of evapotranspiration (ET)) were assessed in 2012 and 2013 season. The results showed that effect of different irrigation rate on corn yield was significant in a dry year but not significant in a wet year. ET estimates used in the irrigation scheduling might be lower than actual water demand by corn for a higher yield. Results of this study should be useful for developing VRI strategies and evaluating ET-based irrigation methods for corn production in humid regions.
Technical Abstract: To investigate the impact of variable rate irrigation on corn yield, twenty plots of corn were laid out under a center pivot variable rate irrigation (VRI) system in an experimental field near Stoneville, MS. The VRI system is equipped with five VRI zone control units, a global positioning system (GPS) receiver, and computer software. Each zone control unit controls the duty cycle of the sprinklers in the zone to realize variable rate water application across the pivot lateral. The GPS receiver determines the pivot position for identification of the control zone in real time. Supplemental irrigation was scheduled based on evapotranspiration (ET) estimates. A randomized complete block design was used in this study, with five irrigation rate treatments (0, 50%, 75%, 100%, and 125% of ET) and four replications. During the growing seasons in 2012 and 2013, VRI prescriptions were created based on the experimental design, and wirelessly uploaded to the system to apply varying amounts of water to each plot. The corn was machine harvested for yield. Effect of the irrigation rate on the yield was statistically analyzed. Results indicated that effect of irrigation rate on yield was not significant in 2012 (F=0.91, p=0.48) and was significant in 2013 (F=5.96, p=0.0018). The treatment of 125% irrigation rate had the highest yield for both years. No significant yield difference between treatments in the 2012 season could be due to the sufficient rainfall in that summer. The ET estimates used in the irrigation scheduling might be lower than actual water demand of the corn crops for a higher yield.