Get the most from your farm’s manure

No one needs to tell a farmer that fall is a busy time of year. As the crop is coming off the fields, livestock producers are ready to follow that up with the emptying of manure pits and lagoons, and hauling manure stockpiles out to the barren acres.

What livestock producers need to be reminded of is the valuable resource that they are handling, and not to simply spread the manure on their crop acres before the snow flies.

Iowa State University’s Daniel Andersen, aka “Dr. Manure,” offers valuable and timely information in his last three offerings on his “The Manure Scoop” blog.

Andersen, an ISU assistant professor of Agricultural and Biosystems Engineering specializing in manure management, reminds producers to adhere to the rule of waiting for soils to get down to 50 degrees F (and cooling) at a four-inch depth before applying anhydrous ammonia to fields. Andersen writes that this 50-degree rule also applies to ammonia-rich manure. In his Sept. 11 blog, Andersen explains “Remember, there are a few forms of nitrogen that can be applied or are found in soils and these include ammonia/ammonium, nitrate and organic nitrogen. Of these forms, all forms can be lost, but ammonia and nitrate tend to be the most mobile.

“Ammonia is lost as a gas, so if we are using an ammonia/ammonium fertilizer (like swine manure) it’s important to get the fertilizer into the soil quickly where the ammonia will react with the soil particles and be held, rather than letting it sit on the surface where some of it can be lost to the air. This is why injection or immediate incorporation can be a great technique for getting the most from your manure; it makes sure that we aren’t immediately losing some portion of the nitrogen we are applying.

“Nitrate on the other hand is lost with water, especially water moving through the soil to groundwater or tile drains. Nitrate is super soluble, so if water is moving and we have nitrate in our soil, it is probably moving with the water. We tend to have larger rains in the spring coupled with wetter soils from snow melt; this means that if the nitrogen we applied is in the nitrate form there is a high opportunity for it to be lost in the spring.”

Technology evolution

In his last two Manure Scoop blogs (Sept. 23 and Oct. 7), Andersen talks of the evolution of manure spreaders and the importance of using today’s technologies to benefit the most out of the valuable resource of manure. These technologies are in the advance of the manure spreaders themselves, but also the ability to test the manure itself to determine what is available in the form of crop nutrients.

He writes in his Oct. 7 offering: “Unfortunately, manure is a variable fertilizer – its nutrient content varies from year-to-year or farm-to farm, the availability of some of the nutrients within the manure is influenced by the weather that year, and our ability to control how uniform it is applied is dependent on both our equipment and the field conditions. Understanding the sources of variability in manure and figuring out the best ways to manage them are critical to making the best agronomic and environmental use of manure resource.

“There are three main sources of variability and uncertainty when using manure as a fertilizer for crop production. These are:

  • The nutrient content of the manure
  • The availability for the manure nutrients to the crop
  • Application variability

“If you don’t account for this variability, you can end up applying too much or too little manure, both of which are costing you profits. Applying too little manure can lead to reduced crop because of nutrient deficiency while too much manure wastes nutrients and could negatively impact water quality.”

Click here to read the blogs mentioned above, as well as all of Dr. Manure’s blogs.

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