Farmscape Article 2632  November 3, 2007

The Prairie Agricultural Machinery Institute (PAMI) reports that from a technical point of view solid manure injection technology is ready to move to commercialization.

This past spring, researchers with PAMI began the first field scale tests of a newly developed solid manure injection system. The two piece system was designed to land apply solid and semi solid organic fertilizers containing 20 percent solids or higher. Project leader Dr. Hubert Laundry explains, the system consists of a typical trailer type implement which is fitted with an injection tool bar.

Development of the technology actually began at the University of Saskatchewan (U of S) in 2001. With the completion of a bench scale prototype, the project was turned over to PAMI to take the technology to the field. The two are now working together to prove the technology and take it to the next level.

Solid Manure Infection Technology Field Tested this Spring

The field-scale prototype constructed at PAMI, and field tested this spring, uses a series of discharge screw conveyers to auger manure to flexible injectors. The flexible injectors then deliver the material to coulters that open trenches in the ground into which the manure is deposited. The trenches are then closed.

Dr. Landry notes the process is being referred to as injection to create a parallel with liquid manure injection but a more precise description would subsurface application of solid manure.

Comparisons this spring included broadcast application, broadcast followed by a second operation to incorporate the material into the soil and direct injection of the material under the soil surface using the new injection system.

Dr. Landry points out in the first year the cooperating farmer seeded oats but the equipment is intended to be matched to any crop system so it doesn’t matter what crop is going to be seeded on the field that is fertilized.

Composted Beef Feedlot Manure Applied

“What we’re working with in this first field season here is solid manure that’s been composted. It’s a homogenized material,” says Dr. Jeff Schoenau a senior research scientist with the University of Saskatchewan’s Department of Soil Science. “There’s not a lot of material in it in terms of trash, rocks, or anything like that because that will cause some problems with the solid application.”

However he says it isn’t a lot different than the solid manure that would be hauled from any feedlot pen. Most of the nutrient in this material is contained in organic form so it requires time for those organic materials to be broken down and released into available forms. In liquid slurries more of the nutrient is found in a form that plants can use right away.

Agronomic and Environmental Factors Monitored

In this, the first year of this particular trial, oats were planted. Dr. Schoenau is monitoring yield, nutrient uptake by the crop and at the impact of the technology on nutrients in the soil.

“We’ve got our yield data back and we certainly found a good yield response of the oats to application of manure in general.”

Supplemental Nitrogen Application Proves Beneficial

Dr. Schoenau notes that at the low application rate of 20 tonnes of manure per hectare some treatments were supplemented with incorporated nitrogen fertilizer.

“In fact at the low rates of the manure application we did see that the additional nitrogen fertilizer was beneficial in maximizing the yield. That’s because the solid cattle manures do tend to release their nutrients fairly slowly and for that reason we do see some benefit with the supplemental commercial nitrogen fertilizer.”

In terms of the application methods: broadcast without incorporation, broadcast with incorporation and solid cattle manure injection Dr. Schoenau says, “The yield in the injected solid cattle manure plots wasn’t significantly different from the other methods of application – So not a lot of difference there in terms of what we’re seeing in oat yield.”

Odour and Greenhouse Gases Monitored

As part of a related study Joy Agnew, a University of Saskatchewan Agricultural and Bioresource Engineering graduate student, is comparing odour and greenhouse gas emissions in liquid and solid manures as well as surface and subsurface applications. The research is intended to determine which is the more emission friendly type of manure and which is the more emission friendly way to apply it to the soil.

“Whenever possible, we actually had the solid manure injector prototype at PAMI apply the solid manure for us with both surface and subsurface application. For some of the solid treatments and all of the liquid treatments we actually hand applied the manure. We simulated as close as possible actual broadcast liquid manure application and injected liquid manure application then we deployed two types of chambers on the soil after the application to collect the greenhouse gas and odour samples.”

Solid Manure Less Odourous than Liquid Manure

Agnew notes, it’s common sense that odours will be reduced when you inject manure under the soil but we weren’t really sure how the injection was going to affect the greenhouse gas emissions.

“So far we’ve seen that liquid manure will result in more odours and greenhouse gas emissions than solid manure. Actually liquid manure produces 50 percent higher odours and 80 percent higher greenhouse gases than solid manure. As for the injection versus the surface application we saw that the overall odour emission was decreased by 20 percent due to injection.”

However Agnew adds, “When you break it down between liquid and solid, manure injection actually slightly increased odours from liquid manure, probably due to pooling of manure at high application rates. Injection of solid manure reduced odours a little bit more consistently and provided an overall reduction of odours of 40 percent.”

Comparisons Due to Continue for Three Years

The manure application comparisons at Humboldt are scheduled to continue for three years. Dr. Schoenau says in addition to providing an opportunity to refine the technology it will allow an opportunity to look at other crops.

He stresses, “One of the potential benefits of getting that solid manure below the surface is reducing some of the accumulation of nutrients right at the surface of the soil where they may be susceptible to movement into water bodies by surface runoff waters. This is something we’re looking at both for phosphorus and for nitrogen.”

Technology Ready for Commercial Application

Dr. Landry notes, from a technical point of view, the technology is very close to being ready to move to commercialization. However he acknowledges the first step is to prove its benefits.

“We need to demonstrate that, yes this new machine can bring benefits to the farmers in terms of better yields and eventually better environmental results in terms of greenhouse gases and odours.”

Dr. Schoenau  agrees, “As we work with this equipment, we certainly learn a lot and think about ways that it can be made to perform better out in the field with a variety of different manure sources and under conditions.”

“The other is to establish some of the potential benefits that might be seen from this technology, such things as improving the crop recovery of manure nutrients and reducing the loss of those nutrients and other constituents to the environment.”

Dr. Landry notes the equipment functions quite well and, while a commercial version would require some modification, as far as the mechanical systems go there would be no major changes required.

Staff Farmscape.Ca