Conservation and Nutrient Management: Save Money with a Smarter Plan
By Charlie Ebbesmeyer, SWOF Field Program Representative: NE and Southern Missouri
Efficient nutrient management is key to maintaining soil health, maximizing crop yields, and reducing costs while also supporting conservation efforts. A well-designed nutrient management plan (NMP) ensures that the right amount of essential plant nutrients, from manure to nitrogen-fixing legumes, to commercial fertilizers, is applied in the right place at the right time. This maximizes the economic return of nutrient resources while reducing runoff into waterways and saving you money!
Benefits of a Nutrient Management Plan
Lowers fertilizer costs by applying only what is needed. A 2012 study of over 250 Wisconsin farms with NMPs published in the Journal of Soil and Water Conservation found that 69% of farms saved money with an NMP, savings an average of $18 per acre.
Reduces nutrient runoff into waterways by preventing over-application. Use the “4R” method to apply the right source of nutrient, at the right rate, at the right time, and in the right place.”
Improves soil pH management, ensuring nutrients are available to the plant. For example, soil pH levels can sometimes bind-up nutrients. A lime application can help release nutrients trapped in the soil, reducing the need for additional nutrient applications.
Supports soil health and long-term productivity. NMPs are also used to evaluate the impact of field operations, including crop rotations and tillage practices, especially in relation to soil erosion and surface water quality.
A probe is used to take soil samples.
Start with Soil Sampling
Soil sampling is the most important step in keeping nutrient management in check on your farm. Several factors affect the nutrient levels in your soil. This includes your soil type, crop rotations, management practices, rainfall patterns, and more. By testing soil nutrient levels, farmers can apply only what is needed, reducing fertilizer costs and minimizing environmental impact.
The Iowa State University Extension recommends soil sampling in a consistent way every 2-4 years or once in a crop rotation. Soil sampling is most often done in the fall after harvest or in the spring prior to field work. Either way, they recommend that you stay consistent with your timing and always sample prior to applying fertilizer.
Types of Soil Sampling
Whole-Field Sampling is used to get a representative sample of the typical soil in the field and is usually done on a larger scale. This method is less accurate than zone sampling, but more accurate than a flat rate nutrient application. I recommend no more than 20ac/sample. Take 8-12 soil samples 6 inches deep over the determined field/acre area, and mix the soil together to get a single, composite sample.
Zone Sampling aims to collect samples that represent the average soil within each zone. This method offers more precision by using soil type and harvest maps to divide fields into zones with similar soil properties. Purdue Extension recommends collecting two subsamples per acre in each zone and says that regardless of zone size, a minimum of five subsamples per zone should be collected. This method creates customized nutrient maps for more accurate applications.
Grid Sampling is another common approach that takes soil samples from locations spaced out in a uniform pattern. Grid sizes usually range from 1-5 acres with 8-12 subsamples per grid. Grids provide improved spatial information and can help generate variable rate maps, however there is an increased risk for bias. Certain zones can be overrepresented from the samples taken and more samples are often needed to cover the complete range of soil types and variability.
Purdue Extension offers more insights and step-by-step instructions for soil sampling collection.
Test soils for phosphorus (P), potassium (K), and lime (pH and buffer pH). Organic matter (OM) can also be an indicator for some nutrients such as sulfur. Once soil samples are analyzed by a certified lab, a variable rate map (VRT) can be created to apply nutrients efficiently. Instead of blanket applications, VRT ensures nutrients go exactly where they are needed, optimizing crop growth while reducing environmental impact.
Variable Rate Technology vs. Flat Rate Applications
Flat Rate Applications apply nutrients evenly across the entire field and are often based on yield goals alone, rather than actual soil conditions. In contrast, Variable Rate Technology (VRT) Applications adjust nutrient application rates based on soil nutrient levels, leading to higher efficiency and lower costs. North Dakota State University explains, this technology “includes an in-cab computer and software with a field zone application map, fertilizer equipment capable of changing rates during operation and the Global Positioning System (GPS).” Many modern VRT systems also account for the previous year’s crop removal, helping to restore soil fertility without excessive applications.
How to Create an Accurate Nutrient Management Plan (NMP)
Work with an agronomy professional to ensure proper soil sampling and accurate VRT maps.
Use precision VRT equipment or hire a professional applicator with a calibrated VRT system.
Apply nutrients at the right time:
Phosphorus and Potassium: Fall and early spring applications are best to ensure the nutrients work into the soil and are readily available for the plant by growing season.
Nitrogen and Sulfur: Avoid applying excessive amounts until a growing plant is in the field. These nutrients are water-soluble and therefore highly susceptible to leaching through the soil and into local groundwater systems.
Avoid applying nutrients before major forecasted rains, and while the ground is frozen or snow-covered, to again, reduce the risk of nutrient runoff.
A SWOF staff member collects water samples from the subsurface runoff of an enrolled field.
By following these best practices, farmers can improve efficiency, lower their rising input costs, and support conservation goals, all while maintaining high yields. A strong nutrient management plan also amplifies the work of other conservation practices, such as reduced tillage, cover crop implementation, or diversified crop rotations. If you’re considering any of these practice changes to improve your farm’s bottom line, the Soil and Water Outcomes Fund (SWOF) can help you maximize the benefits of these sustainable practices by providing financial and agronomic support. Contact us today to learn more!
Charlie Ebbesmeyer
Field Program Rep.
As our field program representative for most of Missouri, Charlie works with farmers to implement conservation practices on their farming operations. He also provides support to referral partners. Charlie is a Missouri native and was raised on his family’s farm in Fayette. He attended the University of Missouri—Columbia and graduated in 2019 with a Bachelor of Science in Agronomy. He and his wife reside in Fayette, which allows him to still help on the farm. Charlie enjoys being outdoors—whether it’s farming, hunting, photography, or hiking with his wife and dog.
Sources:
Ackerson, Jason P. Soil Sampling Guidelines. Purdue Extension. Accessed February 7, 2025. www.extension.purdue.edu
Anderson, Meaghan, and Rebecca Vittetoe. A Recipe for Success with Soil Sampling This Fall. Iowa State University Extension. Accessed February 7, 2025. crops.extension.iastate.edu
Genskow, Kenneth. "Taking Stock of Voluntary Nutrient Management: Measuring and Tracking Change." Journal of Soil and Water Conservation 67, no. 1 (2012): 51–58.
International Plant Nutrition Institute. 4R Plant Nutrition: A Manual for Improving the Management of Plant Nutrition. 2016. Accessed February 7, 2025. plantnutrition.ca
Nowatzki, John. Precision Agriculture Technology. NDSU Extension. Accessed February 7, 2025. www.ndsu.edu/agriculture/