Editor’s note: Bijon Brown, Production Economist, Alberta Pork recently interviewed Trevor Wallace, Nutrient Management Specialist, Alberta Agriculture, Forestry and Rural Economic Development. Brown can be contacted at bijon.brown@albertapork.com. Wallace can be contacted at trevor.wallace@gov.ab.ca.

High fertilizer prices have created a renewed sense of interest in using hog manure to nourish crops. Knowledge is the key to putting manure to best use.

Brown: Since mid-2020, we’ve seen a significant rise in fertilizer prices. More recently, we’ve seen how transportation bottlenecks and China’s restriction of fertilizer exports have caused prices to soar. Do you think there is value in using hog manure as fertilizer for crops?

Wallace: Yes, definitely. Basically, all the nutrients that a crop needs can be found in manure to varying degrees. It’s not a perfect fertilizer, and there’s going to be shortfalls of nitrogen within the manure, but as a nutrient source, it’s a very good option for producers – especially the operations that have manure there. They’ve got to put it on the land somewhere, so it can be really targeted both on the landscape and towards the crop, to provide a very good value for that cost of application.

Brown: Is it expensive to test or sample manure?

Wallace: No. The sampling is relatively easy, and sometimes manure applicators can do it for you, but this can sometimes be a pain. Manure composition is variable, so that’s always a problem. On a drag line system with a pump, there’s often a spigot that we can open and take some manure out or use the transfer hose that we’re pumping. We take several samples and then try to keep it cool and get it to the lab, so that’s the bigger challenge than the cost.

Brown: What’s the best way to start this, and how can we value this manure? Is there a tool that can estimate the value of the manure?

Contrary to what some might think, it is possible to put a dollar value on manure through testing and analysis.

Wallace: Yes. There are a couple of different ways to do it, and we do have the ‘manure transportation calculator.’ The calculator allows you to put in the crops you want to grow, and it’s going to give you book values automatically, but you can put in your own values if you’ve had the analysis done.

When you put in your numbers, it spits out the economic benefit and the cost of using it. The calculator evaluates the cost over five years, so over that rotation, we’re going to account for nutrients that are released with time. Value comes in two ways: one of them is from the nutrients in the manure, and the other one’s from the nutrient needs in the crop.

Brown: What’s the best approach for getting consistent nutrient application?

Wallace: The traditional way is really good agitation – starting two to four hours before application. It costs money, but we’ve improved agitation with either multiple agitation pads in the lagoon or new technology, like a remote-controlled agitator that moves around and sucks up the content at the bottom. That’s one approach.

Another way is to take multiple samples from the lagoon at different times. The early material is mostly water, and the later material is going to be a higher percentage of solids. Another way yet uses a newer technology to sample the nitrogen content as the manure’s flowing from the tanker.

Brown: What are the benefits of applying the manure via direct injection versus surface application?

Wallace: Surface application is fast. You can do a large area quickly to reduce soil compaction, but the problem with surface application is the loss of that available nitrogen with solid manure, which has a lot more of the organic nitrogen and a smaller amount of the available nitrogen. With liquid manure, it’s fine. There’s a lot of nitrogen that can be lost depending how we handle it.

Injecting manure, rather than surface application, remains the preferred method. Among other reasons, less nitrogen is lost.

Brown: Should application be directly to the soil, to make the best use of nitrogen?

Wallace: Yes. It can still be broadcast, but the quicker we work it in, especially the liquid, the more nutrients or nitrogen being captured. The guys that are changing their system so they can spread during the season – into growing crop – are not spreading it when there’s a risk of loss, since most of our runoff’s in the spring. If we can get it in the ground in the fall, the organic stuff will start breaking down a bit, but crops use it better. A low broadcast or a pure injection helps with odour, and maybe the most important thing, it gets some of the equipment off the road, for safety reasons. 

Brown: Are there any other benefits we can get out of manure when it comes to soil quality? 

Wallace: Yes. Part of it comes from that organic portion, like the manure itself. We’re adding a food source for microbes. Solid manure can have a greater impact than the liquid. It’s adding the carbon and organic matter to the soil, which makes the ground more pliable and easier for crop growth. It granulates really nicely and helps with water infiltration, resists soil compaction and helps the plant roots.

Brown: Is there value to using manure for renewable energy?

Wallace: I’m torn on it. For this technology to work, it needs to be scalable and fit the size of the operation. The difficulty with this is that it is complex technology – it’s going to require expertise or extra labour. Many manures are not really high-energy producers. We can use the manure as a base in the mixture for something like an anaerobic digester, but the hog manure we did some research on was producing about 156 megajoules of energy per tonne. In the same quantity, poultry manure produces 3,200 megajoules, and coal is 22 to 32 gigajoules [22,000 to 32,000 megajoules].

Brown: Are there benefits to having knowledge in terms of how manure affects the environment?

Wallace: Yes. When we often talk about manure, we look at it as an economic benefit for the crop. It is a cost to get it out there, but whatever we can do to maximize the use of the nutrients that are in it helps offset that cost. When we start talking about losses due to gases in the air or runoff, the loss of value is either a loss in yield or just a pure loss of cost, because you paid to put it there, but now it’s gone.

Those nutrients do the exact same thing in water as they do on land. A very small amount of them have a huge impact in water, so when we start to lose nutrients because of runoff, we’re not capturing them in the field. That nitrogen or phosphorus can have a significant effect on the growth of algae, for example, which has a negative impact on water quality.

Brown: Do you have any best management tips that can help a farmer manage his use of manure?

Wallace: Knowing what’s in the manure is a great first step. It doesn’t matter if you start with book values, but knowing what you’re applying is important.

I’ve worked with a lot of producers who have figured out their application rate not because they know what’s in it, but they’ve done it so long and they’ve come up with a number that produces the crop they’re targeting, so they’ve figured it out that way, but getting to know the nutrient content through soil sampling is fundamental.

Knowing that nutrient profile really helps with taking advantage of all the nutrients that you’re applying or the nutrients that are in the field, because if they’re accumulating there, you’re not getting value from them. 

Producers in Alberta are encouraged to contact Wallace if they are interested in learning more about how to best use their manure. Producers outside of Alberta are encouraged to contact their local agronomist.