January 28, 2026

2026 January Stewardship Advocate

Nutrient Management on Iowa Corn Farms

The Iowa Nutrient Reduction Strategy (INRS) was unveiled in 2013 as a roadmap to assess and reduce nutrients transported to Iowa waterways and the Gulf of Mexico. Developed by experts from Iowa State University, the Iowa Department of Natural Resources and the Iowa Department of Agriculture and Land Stewardship, the INRS focuses on reducing nitrogen and phosphorus in Iowa’s water bodies. The strategy outlines efforts to reduce nutrients from point sources, such as municipal and industrial wastewater treatment plants, and nonpoint sources, including farm fields, golf courses, lawns and urban landscapes, in a scientific, reasonable and cost-effective manner. Iowa farmers play a key role in the success of this strategy.

Nutrient management is essential for farmers aiming to maximize crop yields. When producing high corn yields in Iowa, the key macronutrients required are nitrogen, potassium, phosphorus, and sulfur, along with micronutrients such as zinc, boron, and manganese. Fertilizers typically rank among the top two or three annual expenses for Iowa corn farmers. Using too much fertilizer not only incurs extra costs but can also result in nutrient runoff from the field. Conversely, insufficient fertilizer application can lead to reduced yields and lower revenue. Striking the right balance in fertilizer use is challenging due to varying factors such as weather conditions, soil types, soil fertility levels, and more.

Fortunately for corn growers, there are some methods and new technologies available to help them manage their fertility programs. A few of these methods are described below:

Grid Soil Sampling Combined with Variable Rate Applications

Grid soil sampling and variable rate application are techniques used to improve the efficiency of fertilizer use and soil management. Grid sampling involves dividing a field into smaller areas and collecting soil samples from each grid to determine how nutrients are dispersed across the field. The collected data is called a soil map and is used to create a “prescription” for a variable rate applicator that applies more fertilizer in areas where the soil tests read “low” and less fertilizer in areas where the soil tests read “high.” Using grid sampling and variable rate technology increases the probability that all corn plants in the field have adequate nutrients while reducing the likelihood of over or under-applying fertilizer.

Applying the 4Rs

The 4Rs of nutrient stewardship include applying the right source of nutrients at the right rate, right time, and right place. The 4Rs are strategies for optimizing nutrients in the field to assist farmers in creating their fertilizer plan for the growing season.

Split Applying Fertilizer

It is well known that once a corn plant is about knee high, its rate of nitrogen uptake accelerates rapidly as it approaches tasseling. This is when utilizing a split fertilizer application is most effective, allowing the grower to apply nitrogen fertilizer when the plants need it the most. This is depicted in Figure 1.

Iowa Nitrogen Initiative

Nitrogen is the most studied yet mystifying nutrient among those applied to corn fields. Among the 4Rs of nutrient management—right source, right timing, right place, and right rate—determining the optimal nitrogen rate is the most complex. Agronomists at Iowa State University (ISU) have embarked on an ambitious effort to quantify the Economic Optimum Nitrogen Rate (EONR). This effort is called the Iowa Nitrogen Initiative (INI). The EONR value is the nitrogen rate at which the economic payback from yield equals the cost of the increase in nitrogen fertilizer applied, essentially a breakeven point.

Historically, nitrogen rate recommendations in Iowa were derived from fewer than 20 small plot trials conducted annually at university research farms. In contrast, the INI employs large, variable-rate plots in farmers’ fields across Iowa. The INI team partnered with farmers statewide to conduct more than 500 field trials in 2025. All the collected information is being used to create data-driven nitrogen management considerations. In addition, ISU statisticians and programmers collaborated with the INI team to develop an app for farmers named N-FACT to run different scenarios where farmers can enter a few parameters into the app to reveal simulated results on both the agronomic optimum nitrogen rate and the EONR for their location. For more information or how to participate, see Iowa Nitrogen Initiative. To access the N-FACT app, click here https://n-fact.ag.

Developing an effective nutrient management plan is one of the most important aspects for farmers in their corn production systems. Fortunately, there are several tools available to aid farmers as they calculate their optimal fertilizer rates and manage their fertility programs.

Reprinted for 2025 Soil and Water Club report.

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Farmer to Farmer: Paula Ellis

Paula Ellis, her husband Jeff, and sons Josh and Parker, farm in Lee County near Donnellson in southeast Iowa. She has been farming since 1993, and her career started with an FFA project. Since then, they have incorporated their operation and now farm 2000 acres in a corn/soybean rotation.

Paula farms on her family’s Century Farm and they are very proud of that. She says, “Our goals are sustainability and efficiency. While margins are extremely tight right now, we continue to evaluate how we manage our farm. Our sustainability journey began in the early 1980s when my dad started no-tilling. Since that time, many of our fields haven’t been touched with deep tillage equipment. We currently no-till, contour farm around hills, build terraces to slow water down, have waterways throughout the farm and plant cover crops. We are also enrolled in the Conservation Stewardship Program, have Conservation Reserve Program buffer strips and established a pollinator plot. By using these conservation practices, we are able to cut fuel and equipment costs, while building soil health on our farm.”

Paula’s corn planting population goal is 34,000 plants per acre and they plant a mixture of hybrids in the 109-116 day range. Their fertility program is based on management zones that are established on different soil types. Paula says their fertility approach centers on feeding their corn crop throughout the season, “We apply early season nutrients with the planter and in-season nutrients by side dressing and foliar feeding. We apply soil amendments in the fall based on soil tests that are taken every four years. Our planter is set up to apply the liquid fertilizer in the seed furrow while roughly half of the total nitrogen is applied in a 2”x2” spacing from the seed.”

A rye cover crop is seeded on 30-35% of their fields. Cereal rye is spread on after the crop is harvested and terminated in the early spring. They have successfully planted corn into green rye, and with their fertilizer program, they have seen positive yield results.

The tight profit margins have the Ellis family constantly looking for ways to maximize corn yields with the least amount of inputs. This past fall, Paula and Jeff invested in a vertical tillage tool. She says, “Our goal is to pair vertical till with our no-till system to help warm up the soil quicker in the spring and help break up the corn stalk residue. Cooler soils have always been a problem in the early spring so we’re hoping vertical tillage will promote quicker germination and emergence.”

In addition to being busy on the farm, Paula is passionate about being involved in off the farm learning and advocacy activities, saying, “I am part of I-LEAD Class 12 and serve on the Iowa Corn Animal Agriculture and Environment committee. I am a voting delegate and active participant of CommonGround, which is an organization that connects women farmers and shares stories about the important roles that women play in US agriculture. I believe in being active in our organizations to promote our products and know I’m doing what I can. Whether it’s talking to legislators or doing a “farmer take over” on social media, we have to be proactive to tell our story.”

She sums up her philosophy by saying, “We’re always looking at ways to increase yields and plant health. Maximizing efficiency is our goal, whether it’s time, fertilizer, equipment or fuel. At the same time, we are doing our best to steward our land to improve its soil health and long-term productivity.”