ISU Extension and Outreach
ISU Extension and Outreach
ISU Extension and Outreach reliable information about agriculture, 4H programs, food and nutrition, and family sciences. ISU Extension and Outreach has an office in Muscatine.

Muscatine Living

By Kristina TeBockhorst and Daniel Andersen–Iowa State University Extension and Outreach

Using manure as a fertilizer may help lower costs as the price of synthetic fertilizers continue to increase.

AMES, Iowa – Last fall, fertilizer prices were trending higher, and with supply change issues and soaring fuel prices, that trend has continued into the spring.

Even with potentially higher crop prices, this offers challenges to finding ways to increase or maintain farm profitability. One available option is to explore the use of manure.

Why apply manure in the spring?

Aligning nutrient availability with crop nutrient demands is good for the farm’s bottom line and downstream water quality. Research has shown that applying nitrogen closer to when the crop needs it can reduce the risk of nitrogen loss to the environment.

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 seen by delaying manure application from late fall when soils are 50 degrees Fahrenheit and cooling until spring. With 2022 futures corn prices, yield improvement can easily total over $200 an acre in value.

Cost savings can also add up fast with today’s fertilizer prices. The nitrogen value in manure can often account for half of the manure’s total fertilizer value. In typical swine finishing manure with 50 pounds N per 1,000 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 available to the crop and how much leaches out depends on manure application practices and weather.

Spring can be a busy time, the window for fieldwork can be short, and spring rainfall can keep soils wet, leading to compaction concerns. However, there can be some clear economic and environmental advantages to applying manure in the spring. With much of the state rated as either abnormally dry or in moderate drought conditions as of March 10, conditions might be more favorable for spring manure application this year.

Similarly, this may be a good time to reexamine the nitrogen application rates you select. Manure management plans typically utilize the yield goal method to set nitrogen application rate maximums, intended for environmental protection, not to maximize profit. Rate selection tools, like Maximum Return to Nitrogen, can be used to determine rates that will help you maximize your manure fertility value and typically will help you stretch the manure across more acres.

Best practices for spring application:

  • Prioritize fields with well-drained soils, adequate drainage, and good soil structure.
  • Consider reducing manure load sizes to limit axle loads to less than 10 tons, which will help reduce the risk of deep compaction.
  • Check for proper tire inflation. Consider reducing tire pressure to less than 20-35 psi and using flotation tires to reduce the risk of surface compaction.
  • Limit field traffic by designating sacrifice paths.
  • Agitate manure well for a more uniform nutrient application and sample manure for nutrient content to know what you are applying.
  • Check and calibrate application equipment for application rate uniformity and good injection or soil incorporation.
  • Watch the weather forecast closely and avoid manure application before rainfall events.

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