Consider spring manure application

     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. However, one available option is to explore the use of manure. Many livestock owners have long known the value manure has to offer. With skyrocketing commercial fertilizer prices, this offers the opportunity to make even better use of the manure resources.

     In this article, ag engineering specialists with Iowa State University Extension and Outreach explain the opportunities and challenges to using manure as fertilizer in the spring.

     Farmers who historically have relied on synthetic fertilizer, and even those who have used manure, but have limited experience with spring application, should consider using some manure this spring. While there is never a guarantee of what fertilizer prices will do in the future, current prices are unprecedented. Until 2021, most years showed a lower average price in the fall than in the spring. Even if your manure resources are limited and applying some manure this spring means you won't be able to cover as much ground next fall, it still represents an opportunity to save some money now since fertilizer prices haven't stabilized.

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. Fall nitrogen applications can pose a risk for nitrogen loss to the environment, especially when manure is applied earlier in the fall. With a longer period between manure application and crop nitrogen use, there is a higher likelihood that some nitrogen conversion and leaching will occur.

     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.

     Factors at play include:

     • The length of time between crop nitrogen use and manure application.

     • The soil temperature that the manure is exposed to during this time.

     • The amount of moisture that moves through the soil.

     Applying in the spring will ensure you're getting most of that $200 value without needing to spend money on other nitrogen fertilizer sources.

     Best practices for spring application:

     • Prioritize fields with well-drained soils, adequate drainage, 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.