LA RIVIERE, Man. – After cleaning out his cattle pens in the spring, piling the manure and carefully turning it a couple of times, Larry Thompson expected to have a heap of black gold to spread on his alfalfa fields.
His brother-in-law had switched to a minimum-till system, and no longer wanted Thompson’s manure. So Thompson read up on composting and decided to try it.
But the experiment left him wondering where the nitrogen went.
“We were testing (the finished compost) because I didn’t want to put it on too heavy because it would be so rich,” he ruefully recalled.
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The tests showed Thompson had poured his time into a pile of dirt with less than .05 kilograms per tonne of ammonium.
Shrunk in half
His compost heap started out about 2.4 metres high, 40 m wide, and 100 m long. By the time the microorganisms in the pile finished feeding on organic matter, they shrunk the pile by half.
“It’s a lot smaller,” said Larry’s wife Beth “But it’s a bigger pile than you need of something that’s no good at all.”
Beef producers searching for a different way to handle manure may look to composting, but those who have tried it say farmers need to rein in their expectations.
A compost heap tries to provide the ideal working conditions for the bacteria that decompose organic materials.
Composting’s most visible benefit is reduction in the bulk of manure.
“In this area, we’ve got a high population of cattle,” said Andrew Olson, a research technologist at Agriculture Canada’s Research Centre in Lethbridge, Alta.
“A lot of the feedlot operators look at their hauling costs when they’re cleaning out their pens and they’ll base how far they’ll travel on the cost.”
He said most producers don’t have a lot of land to spread it and many are looking to expand their feedlots.
Scientist John Paul of Agriculture Canada’s research centre in Agassiz, B.C., said beef cattle manure compost can contain good amounts of phosphorus, potassium and micronutrients.
The heat generated inside compost windrows kills weed seeds, pathogens and fly eggs.
Nitrogen disappears
Paul said the amount of nitrogen left in compost depends on the ratio of straw to manure. Even with extra straw, a lot of nitrogen tends to be lost to the air.
He tested cattle manure compost on corn fields in Ontario. For that crop, in those conditions, the compost wasn’t a replacement for nitrogen fertilizer.
To decide whether compost contains enough for a crop, Paul said farmers should test it, know the nitrogen levels in the field and consider the needs of the crop they want to plant.
“The value in the compost is there as a soil improver but it can’t, in all circumstances, take the place of chemical fertilizer,” Paul said.
