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A report from the AgTech Centre

Tillage tool type affects level of manure incorporation

With increasing concern about all aspects of manure application, livestock producers need to realize that not all tillage tools incorporate manure to the same degree, says an engineer at Alberta Agriculture, Food and Rural Development's (AAFRD) AgTech Centre.

The type of equipment used directly affects the level of manure incorporation, says Lawrence Papworth, a project engineer at the Lethbridge-based centre, who led a research project to evaluate five different systems.

Research showed relatively new tillage equipment known as the combo tool provided greater manure incorporation over an offset disk harrow, two types of chisel plows and a heavy harrow.

The goal is to find a balance between minimizing odour and run off from manure application and incorporation, and maximizing ground cover to reduce erosion and conserve moisture. The question is how much incorporation is enough to get the job done, while leaving as much crop residue on the soil surface as possible.

"As new manure incorporation standards develop it will be important for producers to know how equipment performs," says Papworth. For example, under current Alberta regulations, all manure applied to tilled fields is required to be incorporated within 48 hours of application.

Research at AgTech Centre looked at the range of tillage equipment available, some familiar, some less familiar to western Canadian producers. The combo tool, made by several manufacturers and used widely in some parts of the United States, is a combination of a disk harrow and a deep-till subsoiler. The aggressive tillage equipment consists of deep ripper shanks between disk gangs.

Other tillage tools evaluated included more familiar equipment such as a heavy tandem disk, a chisel plow with spikes, a chisel plow with sweeps and a heavy harrow. The equipment was adjusted to operate at tillage depths ranging from one to 16 inches, depending on the tool.

The equipment was used to incorporate fresh, solid feedlot manure applied with a standard solid manure spreader at a rate of 12 tons per acre (30 tonnes/hectare).

Evaluation of how the equipment performed was measured with both a visual assessment as well as soil nutrient analysis. The visual assessment, using a grid system on manure application plots, made a visual count of how much manure was visible on the soil surface after incorporation. To back that up, a soil analysis was made to measure the amount of chloride in the soil profile after incorporation. Since feedlot manure is high in chloride, it was suspected the level of chloride would spike on plots with higher degrees of manure incorporation. "Both types of evaluation pointed to the same conclusion," says Papworth.

Over two years of research, the combo tool averaged 97 percent manure incorporation, while the offset disk harrow provided 95 percent incorporation, the chisel plow with spikes approximately 92 percent, the chisel plow with sweeps approximately 89 percent and the heavy harrow approximately 86 percent.

"Our research confirmed the expected in that the more aggressive tools provided a greater degree of manure incorporation," says Papworth. "From that information producers can decide what level is appropriate for their needs."

AgTech Centre is part of Alberta Agriculture, Food and Rural Development's Technical Services Division and has a mandate to support all aspects of agricultural sustainability.

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