This project evaluated how different irrigation scheduling methods affect maize yield and nitrate leaching in coarse-textured irrigated soils in Central Minnesota. Coarse-textured soils have low water-holding capacity, so irrigation is often needed to maintain crop productivity, but over-irrigation can increase nitrate movement below the root zone and create water quality concerns. The study compared four irrigation scheduling approaches: soil moisture sensor-based scheduling, the checkbook method, the Irrigation Management Assistant tool, and EPIC model-based auto-irrigation. The research was conducted from 2019 to 2021 under continuous maize at two Minnesota sites: Becker and Westport. Overall, the soil moisture sensor, IMA, and EPIC approaches applied less irrigation water than the checkbook method, with IMA applying the least water. Grain yield was generally similar among soil moisture, checkbook, and EPIC treatments, while IMA produced lower yield in some cases, especially during the dry 2021 season. Nitrate leaching was strongly affected by precipitation, irrigation amount, and irrigation frequency. At Westport, IMA substantially reduced nitrate-N leaching compared with the checkbook method, but yield penalties indicate that additional calibration is needed before broad adoption. The findings show that improved irrigation scheduling can reduce nitrate losses while maintaining maize yield, but tools must be carefully calibrated for sandy soils and dry growing seasons.
We also used the Environmental Policy Integrated Climate (EPIC) model to evaluate how different irrigation scheduling methods affected corn yield and soil water balance at the Becker and Westport research sites in Central Minnesota. This study compared checkbook scheduling, soil moisture-based scheduling, the Irrigation Management Assistant, and EPIC-based auto-irrigation. The model results showed that EPIC-based irrigation performed similarly to soil moisture-based scheduling while requiring less labor, making it a promising approach for irrigation decision support. The study also showed that checkbook scheduling tended to increase deep percolation losses, while the IMA approach reduced irrigation amounts but increased the risk of crop water stress under some conditions. Overall, the findings reinforce that irrigation scheduling tools can improve water management on sandy soils, but they must be carefully calibrated to maintain yield while reducing unnecessary water loss.
Study Period: 2019-2021
Research Team: Vasudha Sharma, Gurparteet Singh, Muhammad Tahir, David Mulla
Funding: Minnesota Corn Research and Promotion Council and Minnesota Department of Agriculture (MDA)