Spring Manure Application: Setting Up for Success

As winter fades and the ground begins to thaw, spring manure application moves to the top of the priority list. But applying manure effectively in the spring requires more than just an open weather window—it demands planning to maximize nutrient availability, avoid compaction, and minimize environmental losses.

Evaluating Manure Storage and Application Timing

For many farmers, the first concern with manure is manure storage capacity. Earthen manures storages can be reaching near-full levels by the end of winter, creating urgency for spring application. While deep pit storages, which are often designed to hold close to a years’ worth of manure, won’t be full, it is important to evaluate how full the storage is and if there is sufficient space available to make it to fall or if you should be considering getting some manure used this spring. When soils are frozen there is greater risk of nutrient loss from both in both runoff and from volatilization. Even when the surface appears thawed, subsurface frost can prevent infiltration, leading to manure running off with early spring rains.

Soil Conditions: The Foundation of Smart Application

Beyond soil temperature, moisture content is another key consideration. Applying manure to saturated soils increases the risk of runoff and compaction. Wet soils soak manure in more slowly, and getting the manure nutrients in contact with the soil is critical for holding nutrients. Moisture conditions also play an important role in soil compaction. Compacted soils can reduce corn yields by up to 10% due to poor root development and restricted water movement in some growing conditions.

You can find more information on how soil moisture impacts field activities from Iowa State University Extension and Outreach and I talk more about how  moisture impacts manure movement in soil during injection in a classic The Manure Scoop post.

Manure Nutrient Content: Test Before You Apply

One of the biggest mistakes in manure application is assuming nutrient values without testing. The nutrient content of manure varies significantly based on animal diet, storage method, and agitation practices. The University of Minnesota, recently released a tool, ManureDB, showing results from many manure samples. One thing we can say is manure concentrations are highly variable from farm to farm. It is critical to know what is in the manure you are applying by getting it samples and tested.

·         Swine manure ranged from 30–65  lbs of nitrogen per 1,000 gallons, 10–30 lb P2O5, and 15–35 lb K2O

·         Dairy manure averaged 10–20 lbs of nitrogen per 1,000 gallons, 5–10 P2O5, and 15–25 lb K2O

·         Beef manure averaged 10–20  lbs of nitrogen per ton, 5–15  lb P2O5 per ton, and 10–20 lb K2O per ton.

·         Poultry litter contained 40–65  lbs of nitrogen per ton, 30–50  lb P2O5 per ton, and 26–45 lb K2O per ton.

Without testing, there’s a risk of either over-applying (wasting nutrients and increasing leaching risk) or under-applying (leading to nitrogen deficiencies in crops). Taking multiple samples and averaging, or compositing before analysis, helps reduce variability in sample results and ensure a more representative measurement of manure nutrient content.

Calibrating Equipment for Even Application

Uneven manure application can result in poor crop performance and increased environmental losses. Before heading to the field, check equipment to ensure:

·         Flow rates and pressure settings are appropriate for the manure consistency.

·         Injectors are distributing manure evenly across the application width.

·         GPS or guidance systems are calibrated to prevent overlaps or skips.

Minimizing Nutrient Losses and Protecting Water Quality

Spring manure application comes with an increased risk rainfall and wet soil conditions. To minimize loss:

·         Setbacks: Follow setback distances from streams, water sources, and designated areas.

·         Incorporation: Injecting or lightly incorporating manure reduces ammonia volatilization by 30–60% compared to surface application.

·         Cover Crops: Research shows cover crops can reduce nitrate leaching by up to 40%. We are currently evaluating cover crop control of nutrient loss with swine manure application data and will have more data available this fall on how it performed.

Regulatory Considerations and Recordkeeping

Keeping records of application dates, rates, field location, and application method is required for those with a manure plan. It is also a best practice to record field and weather conditions at application that can assist with compliance and nutrient management planning.

Final Thoughts

Spring manure application is about more than just emptying storage—it’s an opportunity to optimize nutrient use, improve soil health, and support crop productivity. By waiting for the right soil conditions, testing manure, calibrating equipment, and using best management practices to reduce losses, farmers can turn manure into a valuable asset rather than an environmental liability. With a little planning and attention to detail, manure can provide the nutrients crops need while protecting water quality and maintaining soil health for the long run.