The 4 Rs of Manure Management: The Right Place

January 31, 2019

2019-01-31 The 4 Rs of Manure Management: Right Place from Central Valley Ag on Vimeo.

The 4 Rs of Manure Management: The Right Place

In the last couple of articles and videos we have talked about the right source and right rate of fertilizer and applied those concepts to how we manage our manure resources. This month I would like to focus on the right placement of our manure and its nutrients. Of course, what type of manure we are dealing with makes a big difference, and the first thing we generally think of is what kind of animal the manure came from. I am going to look at it a little differently and say the most important factor in placement is actually the amount of moisture in the product. 

The term “manure” covers a wide variety of different products ranging from the nutrient and organic-rich water in a lagoon or settling basin to a dry product like composted or even dehydrated poultry manure. These products are going to be handled differently, and the options for placement vary considerably.  

Since we already covered variable rate application, I am going to talk here about how we place manure relative to the soil surface not where we place it in the field. Lagoon water or the nutrient-rich water in a settling basin that catches runoff water across open lots will generally have less than 2% solids. Since that product is 98%+ liquid we can often run it through a pivot or pump it through a hose attached to an injector out in the field. The pivot will water about half of the ammonia into the soil, and the injector should get nearly all of the ammonia under the soil surface depending on its design.

Getting manure into the soil vs. laying it out on top of the soil surface allows us to take advantage of the ammonia nitrogen in that manure that will volatize off into the air if we leave it on top of the soil surface. The same is true with liquid dairy, cattle, or hog manure stored in a pit. These products normally have higher “solids” values but are still 85-98% water. These pit stored manures tend to have high nitrogen content with large ammonia values. That ammonia N can be put to use by our crops if we can get it incorporated into the soil. If we do not get it incorporated right away, we lose that ammonia nitrogen. Typically, every day manure lays on top of the soil surface you lose 20-30% of that ammonia N depending on temperature and other factors.

How we get that manure incorporated into the soil makes a difference as well. Injecting the manure, and getting good closure of the slots allows you to take credit for all of the ammonia N. If you use some type of coulter system to mix the manure with the soil but still leave some manure on the soil surface you probably need to discount that N credit from the manure. If you apply a liquid or solid type manure on the soil surface and disk it in later you will need to discount those ammonia N values by about 30% for every day it sits on the soil surface.

We don’t normally think about the P, K, or other nutrients in manure and how surface application or incorporation affect them. These nutrients are not easily lost to the atmosphere like ammonia. We probably should think about how placement affects them more. I am a big fan of no-till. I like how it cuts down on soil erosion especially on hilly or rolling ground. When we place manure on the soil surface in a no-till system we set ourselves up for some nutrient loss through runoff and erosion. Water quality problems associated with nitrogen and phosphorus from agricultural land are going to continue to be an issue for producers. We need to think about how we can limit loss of manure nutrients especially N & P to surface water. It may make sense to disc in manure vs. leaving it on the soil surface to try to get that phosphorus worked into the soil and not just laying on top of it. Every case is different and needs to be considered on its own merits but don’t just dismiss the idea of getting manure worked into the soil because you don’t normally till. 

As you deal with dryer forms of manure such as feedlot manure or poultry manure look at two things: 1) How much ammonia N do I have in this product? If there is a large amount get it worked into the soil to take advantage of that N. 2) How can I best limit N or P loss to the environment?   Maybe that answer is; do not till because the erosion loss will be too great or the soil health benefits of no-tillage outweigh the benefits of getting the manure into the soil. But maybe the right answer is the negative short-term impact to the soil is outweighed by getting that P & N into the soil where it cannot run off as easily. At least ask yourself or others you trust these questions. 

For additional information feel free to give me a call or check out the great resources on nutrient losses and availability provided by UNL on their UNL Water website.

- By Tim Mundorf

Posted: 1/31/2019 3:56:52 PM by Kelli Emanuel | with 0 comments