By Scout Nelson
The number of irrigated acres in Minnesota is rising as farmers seek ways to ensure high crop yields during dry years. This blog post updates an ongoing field research study at two irrigated corn sites in Minnesota’s central sands region, focusing on how different reduced irrigation strategies impact nitrate leaching and residual soil nitrate.
After four years of data collection—one wet year and three dry years—we have observed interesting results regarding irrigation strategies, water usage, and nitrate leaching losses.
This study is being conducted at two locations in central Minnesota: The Sand Plain Research Farm in Becker and the Rosholt Research Farm in Westport. Both sites are at the heart of Minnesota’s irrigated agricultural area, funded by the Agricultural Fertilizer Research and Education Council (AFREC) and the Minnesota Department of Agriculture (MDA).
The primary aim of this research is to explore how various irrigation and nitrogen (N) fertilizer rates interact, influencing nitrate leaching, corn yield, and water and N use efficiency in coarse-textured soils. We are evaluating six nitrogen rates (0, 70, 140, 210, 280, and 350 pounds per acre) alongside four irrigation levels
We are measuring corn yield, nitrate leaching, soil moisture, plant nutrient status, and soil nitrate levels. Nitrate leaching is assessed using permanent suction cup lysimeters installed at a depth of four feet, sampled weekly during the growing season. Soil moisture is monitored weekly using a Neutron Moisture Gauge, helping estimate irrigation needs and drainage. Additionally, we collect plant samples at various growth stages and soil samples post-harvest for soil nitrate analysis.
Preliminary findings indicate that increased nitrogen application correlates with higher residual soil nitrate levels, which can lead to inefficient crop uptake and greater leaching risks. Notably, both rainfed and fully irrigated crops show higher residual nitrate than limited irrigation treatments, indicating that moderate irrigation (50-75% of full irrigation) optimizes nitrogen uptake and minimizes environmental risks.
In conclusion, this study emphasizes the importance of managing irrigation and nitrogen application rates to enhance crop efficiency and reduce nitrate leaching. By adopting limited irrigation strategies, farmers can improve sustainability while protecting water resources in sandy soils.
Photo Credit:minnesota-department-of-agriculture
Categories: Minnesota, Education, General