GUELPH, Ont. — It was 10 minutes into a presentation on soil health at the Guelph Organic Conference when a farmer raised his arm to make a point.
The presenter was discussing the relationship between soil microbes and soil fertility when the farmer said, “the more you feed” the soil with nutrients, “the lazier the plant gets.”
Another audience member supported the comment. He said farmers grew crops for thousands of years without adding nutrients to the soil. Based on those ancient principles, modern day farmers should forgo crop inputs if they want to be sustainable.
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Stuart McMillan, an organic inspector in Manitoba, is familiar with the “closed loop” philosophy, in which organic producers are unwilling to import and apply crop nutrients.
After visiting hundreds of Canadian organic farms, McMillan has grown skeptical of the approach.
“I have seen (farmers) that, through their own philosophical choices, have not been importing off-farm inputs, be that manure or rock minerals. They have relied strictly on whatever they can grow on their own farm,” he said.
“I started to make some observations (of those systems) … and I’m starting to see declining yields. I’m starting to see poor soil quality.”
Terry Good of Tek-Mac Enterprises, a crop nutrient supplier in Ontario, said growers who refuse to use crop inputs are losing a startling amount of yield.
“I see 60 or 70 bushel variances from fertilizer and no fertilizer in corn,” he said
Organic farmers who add the appropriate nutrients and manage weeds can match the yields of conventional growers, Good said. He knows organic farmers in Ontario who have produced:
- 150 to 170 bushel per acre corn.
- 60 bu. soybeans.
- 80 bu. wheat.
Good said cover crops and soil organic matter are critical elements of organic systems, but there’s no getting around a basic reality of crop production: harvesting grain removes nitrogen, phosphorus and potash from the system.
“To think that you’re going to continue growing any amount of yield over the long haul without added nutrients is pretty much a pipe dream,” said Good, who spoke about large-scale organic farming at the Guelph conference.
He said nutrients are critically short on some organic farms and has seen soil test phosphorus at two parts per million and potash levels of 30 p.p.m.
“If P levels are two parts per million, no (soil) microbe in the world is going to fix that,” he said.
“If you’re not putting P (phosphorus) and K (potassium) in the soil and figuring out a way to get nitrogen from manure or cover crops … you are never going to maximize yields or get ahead of weeds.”
Good said organic farmers need planting equipment similar to conventional seeders, which are capable of placing starter fertilizer next to the seed.
The www.organicinputs.ca website provides a list of approved organic fertilizers, including bone meal, which contains phosphorus and calcium.
“There’s more and more products coming (onto the market) that can supply N (nitrogen), P and K as a starter fertilizer,” Good said.
“No different than conventional farming.”
Roger Rivest, an organic farmer from Tilbury, Ont., used to have a hog operation on his farm and grew crops under a “closed loop” system.
He abandoned the approach when soil tests found low nutrient levels on his farm.
“We didn’t have (fertility) products to add until the last few years,” Rivest said.
“We’re seeing fantastic results. Forty to 50 bu. (per acre) yield jumps in some of the crops.”
University of Manitoba research has confirmed that phosphorus is a limiting factor in organic production, but Good has seen cases where a lack of nitrogen also restricts plant growth.
He showed a slide of a corn plant with bright green leaves next to a plant with dull, brown leaves.
“If you run out of nitrogen you’re going to start burning off leaves from the ground up. If you’ve got the leaf opposite the cob that looks like that (brown), you ran out of N.”
McMillan said the organic certification system is helpful in these situations because it provides feedback to growers who may be mining the soil.
“I do think the organic industry needs to make improvements … in how it can continue to build and promote soil health,” he said.
“Our standards mandate it…. You’re supposed to be improving the soil … and improving soil fertility.”
robert.arnason@prodcuer.com
