Evaluation and Performance of Different Irrigation Scheduling Methods and Their Impact on Corn Production and Nitrate Leaching in Central Minnesota

Abstract

An increase in corn (Zea mays L.) grain production has been witnessed in the United States since the 1960s. Although this increase in corn production has satisfied the needs of a growing world population, management practices for N and water that sufficiently protect the environment are insufficient. Soils with low available water holding capacities (coarse-textured soils) cannot store a lot of water that is available for plant uptake. Hence these soils require meticulous monitoring of soil water levels and controlled supplemental irrigation. Insufficient irrigation may diminish crop yields and leave more N unused through reduced uptake which is susceptible to losses. Excess irrigation has the potential to contaminate ground and surface water sources through deep seepage of nutrients (applied as fertilizers) below the root zone of the crop. Many private drinking wells in Central and Southwestern Minnesota have NO3-N concentrations greater than the USEPA standard for drinking water (10 mg/L).Prior research suggests that fertilizer and water management strategies can potentially reduce agricultural NO3-N leaching. Though a significant amount of research has been conducted to study the impact of fertilizer management on nitrate leaching, only limited research has been conducted to explore the role of irrigation management alone in reducing nitrate leaching. Irrigation scheduling involves estimating actual crop water requirements and maximizing the accuracy and precision in terms of the amount and timing of irrigation applied. This two-year study is conducted at two sites in Central Minnesota on four different irrigation scheduling methods involving different principles and strategies (weather-based, soil-moisture based, simulation-based) to compute irrigation requirements. These irrigation scheduling methods are compared in terms of recommended irrigation amounts, crop evapotranspiration, N uptake, and the potential to reduce irrigation-induced NO3-N leaching in coarse-textured soils without significantly impacting crop yield. One of the irrigation scheduling methods, the Irrigation Management Assistant (IMA) Tool resulted in significantly lower total water application and still obtained similar yields as compared to other scheduling methods. The study demonstrates that adoption of appropriate irrigation scheduling methods in coarse-textured soils can reduce agricultural water loss by up to 65% which directly contributes to a significant reduction in costs pertaining to procurement and application of irrigation water. It was observed that both corn grain yield and crop N uptake were not significantly (p<0.05) impacted by the irrigation scheduling method used. Significant differences in nitrate leaching between different irrigation scheduling treatments were observed. Therefore, irrigation scheduling has the potential to significantly reduce the amount of water and N loss without impacting corn grain production in coarse-textured soils. Also, an 83 % reduction in nitrate leaching was observed with a 37% decrease in precipitation amounts at one of the sites.