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Manure is a Valuable Resource
by LuAnn Rolling, District Conservationist
We know what a busy time Spring can be. The window for field work can be short, and spring rainfall can keep soils wet, leading to concerns of compaction. There can be some clear economic and environmental advantages to applying manure in the spring, however. As input costs rise, producers using manure for crop production should consider how they can integrate more spring application into their production systems.
Kristina TeBockhorst, Field Ag Engineer, ISU Extension and Outreach, recently wrote in the Iowa Manure Management Action Group, that aligning nutrient availability with crop nutrient demands is good for the farm bottom line as well as downstream water quality. She says research has shown us that applying nitrogen closer to when the crop needs it can reduce the risk of nitrogen loss to the environment. “Fall applications of nitrogen can pose a risk for nitrogen loss to the environment, especially when manure is applied earlier in the fall. With a longer period of time between manure application and crop nitrogen use, there is higher likelihood that some nitrogen conversion and leaching will occur.”
TeBockhorst notes that especially with high nitrogen fertilizer prices, it can pay to apply manure in the spring. “Across multiple research studies in Iowa and Minnesota, significant corn yield benefits (average of 33 bushels per acre) have been found by delaying manure application from late fall when soils are 50°F and cooling until spring. With 2022 futures corn prices, yield improvement can easily total to over $200 an acre in value.”
Cost savings can also add up fast with today’s fertilizer prices. TeBockhorst says the value of nitrogen in manure can often account for half of the manure’s total fertilizer value. She calculates that in typical swine finishing manure with 50 pounds N per one thousand gallons and applied at a rate of 4,500 gallons per acre, the nitrogen value alone can sum up to over $200 per acre. “How much of that $200 is actually available to the crop and how much leaches out will depend on manure application practices and weather. Factors at play include: 1) how close to crop nitrogen use the manure is applied, 2) how warm of soil temperatures the manure is exposed to as it sits in the soil, and 3) how much excess moisture goes through the soil. Applying in the spring will ensure you’re getting most of that $200 value and won’t need to spend money on other sources of nitrogen fertilizer this spring.”
Producers are looking to make sound economic decisions as input prices soar. Consistently applying a portion of manure in the spring can be a viable economic decision. Weather and timing constraints will likely keep producers from applying all of their manure in the spring but shifting as much as is feasible to the spring can mean big savings in fertilizer costs and gains in crop yield. Additionally, consistent spring manure application can give us some added flexibility within our manure storage systems.
