MEDICINE HAT, Alta. – Spreading manure on native rangeland is a bad idea that can upset the nutrient balance built over the last 5,000 to 10,000 years.
“If we start adding nutrients artificially to rangeland, the result is there will be a change in organic matter cycling and the nutrient dynamic,” says provincial soil specialist Ross McKenzie.
Alberta’s growing intensive livestock industry has prompted interest in spreading manure on native grasses.
“Rangelands are viewed as a convenient place to dispose of manure and it can also serve to increase forage production,” said McKenzie at the western range science seminar in Medicine Hat Jan. 20.
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“It can create a dominant shift in the plant species on rangeland,” he said.
Manure may cause heavier weed growth that could choke out grasses.
Native grassland consists of low-yielding species that don’t respond to fertilizer in the same way as cultivated species.
Rangeland is self maintaining and all necessary nutrients are derived from grazing animals and the breakdown of organic material in the topsoil. About 75 to 90 percent of the nutrients eaten by grazing animals are recycled back to the soil in urine and feces.
“Almost all of the nitrogen that plants will take up will come from breakdown of soil organic matter,” McKenzie said.
Manure is not a balanced fertilizer and could overload the soil.
One ton of feedlot manure contains about 30 pounds of phosphorus.
One ton of grass removes about 30 lb. of nitrogen and 10 lb. of phosphorus in a growing season.
As well, high soil phosphorus can move in water runoff and contaminate surface water. Manure should not be applied near a water course. One lb. of phosphorus can grow 500 lb. of algae.
Adding nitrogen through manure may be a waste since this element is often lost to the air through volatilization.
“With manure depending on weather conditions, you lose up to 30 percent of your nitrogen in four or five days back to the air,” McKenzie said.
Native rangelands are found on brown, dark brown and black soil zones on nine million acres in Alberta and Saskatchewan. Most of this land is poorly suited to cultivation, although many acres were cultivated and some native species were lost as a result.
“We have to look at these rangelands as being very fragile,” he said.
Each zone is home to unique grass species that adapted to soil types and climate.
Brown soil zones are in semi-arid climates in the short grass prairie.
Dark brown soil contains more organic matter and produces mixed grasses.
Black soil has an ample percentage of organic matter and holds moisture well. Rough fescues grow well in this soil type.
Scattered within all the rangelands is solonetzic soil, which has a thin layer of topsoil with hardpan subsoil. There is little organic matter, and sodium content is higher than in other soil. It is almost impermeable to air and water. Further manure applications do not help because of the salt content and impermeability.
