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A report from the AgTech Centre

Research sets performance bar for liquid manure injectors

Studies to develop standardized tests for liquid manure injectors will provide livestock and crop producers with a buyer's checklist of performance considerations for four of the most popular models, says Alberta Agriculture, Food and Rural Development (AAFRD) Project Manager, Brian Sexton.

Liquid manure injection is a more effective means of controlling odour and nutrient placement is more precise than broadcasting, says Sexton. More producers are considering injection, but there has been a lack of evaluation information to help producers determine which model is best for their operation.

"This study is focused on developing standard test procedures for manure injectors. It will give us evaluation guidelines to help western farmers assess their injection options," he says.

Researchers are testing four different injectors to determine odour control performance, the amount of pooling over a range of injection rates and soil conditions, as well as a comparison of the effects of draft or pounds pull for each injector. The tests will also measure crop residue and soil disturbance with respect to each manure injector.

"After manure is injected, we collect odour samples in bags and send the samples to an olfactometry lab in Edmonton, where a specialized odour panel -with expertise in detecting smell - determine the intensity of the odour. These lab results will help us develop a standard measurement to show how well each injector works at controlling odour," says Sexton.

Injectors will be run at application rates ranging between 3,000 and 13,000 gallons per acre to determine at what range the manure starts to leave the furrow and begins pooling on the field. "The point is to get the manure below the surface. You should be able to walk across a field after application and come out with clean boots," says Sexton.

The pooling tests will also help determine if it's the rate of injection that causes the pooling, or the equipment itself. For example, modifications made to openers to allow fluid delivery may cause uneven fluid distribution.

"There's no question that rate plays a role in pooling," says Sexton. "Some of the problems, though, are with outdated or modified equipment."

Soil condition also affects how well injectors work. Wet soil often contributes to pooling, as the manure is not easily absorbed under these conditions.

Soil disturbance is another issue driving the development of the standardized testing. "A big reason why some producers have been reluctant to adopt injection is their concern about soil disturbance in a conservation practices system," says Sexton. "The fact is, there are injectors that can go on pasture and forage land and cause little soil disturbance. Our study should help determine which ones work best in these conditions."

The study will also look at how draft impacts injector performance. Sexton says having the right size tractor and knowing how much fuel it's going to use is a huge factor when considering the operational costs of injection equipment.

Although some producers with minimum till and pasture land continue to broadcast, this may not be the best choice. "If producers are interested in controlling odour, retaining nutrients and treating manure as a resource, then injection is the way to go," says Sexton.

The liquid manure injection project is part of AAFRD's ongoing commitment to support sustainable agriculture. Field testing is scheduled to wrap-up at the end of 2003 and reports are to be published in 2004. The AgTech Centre is part of the AAFRD Engineering Branch.

AAFRD's Agricultural Engineering Branch has a mandate to support all aspects of agricultural sustainability.

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