REGINA – Micronutrient fertilizers can make a big difference to crops growing on deficient soils.
However, if those soils are only marginally deficient or not deficient at all, crop response can be minimal and any micronutrient fertilizer applied would be a waste of money.
Rigas Karamanos told farmers at the Saskatchewan Soil Conservation Association conference in Regina that they should use micronutrient fertilizers only when the application results in an economic benefit.
“To me, measurement means yield increase,” said Karamanos, an agronomist with Westco Fertilizers in Calgary.
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“If you see a yield increase, it works. If you don’t see a yield increase, in my books – and all the research I’ve been doing since 1980 – then it doesn’t.”
He said farmers will rarely see an economic benefit from micronutrients if their soil tests are above what is considered a critical level.
In response to the statement, “We’ve got higher levels of micronutrient in the plant tissue analysis,” Karamanos said, “So what? If I eat twice as much, I have more food in me. Does that mean I was not sufficient before?”
Karamanos prefers to base his findings on scientifically established criteria to describe micronutrient problems in Western Canada rather than rely on anecdotal experiences.
“I like science. We have plenty of scientific data, especially in Saskatchewan.”
Boron
Karamanos said he’s familiar with only one confirmed boron deficiency in canola in Saskatchewan. This occurred at a location in the northern part of the province where new breaking included an area of highly sandy soil.
“It looks like a sulfur deficiency, but that’s the only documented boron deficiency,” he said.
“We had a study with 40 sites in Western Canada, with yields from 18 to 63 bushels per acre of canola. In none of them were we able to get any response to boron, even in soils that according to the soil test are very low in boron – less than 0.35 ppm in the top six inches (15 centimetres).”
Boron deficiencies are more common in soil that has less than 0.8 percent organic matter.
“Recently, I’ve seen soil testing labs that have the cutoff as 1.5 ppm, but there’s no response to boron. We cannot find a scientifically established response. So where do you need boron? I’d say 99.99 percent – nowhere.”
Copper
There is an extensive amount of research history on copper in Saskatchewan and plenty of positive results.
“The critical level for copper in soil varies from province to province,” he said.
“The critical level in Manitoba is 0.2 ppm, Saskatchewan is 0.4 and Alberta is 0.6. So you get recommendations easier in Alberta than you do in Manitoba or Saskatchewan.”
Karamanos said farmers will know if their soil has less than 0.2 ppm of copper because crops won’t yield more than 15 or 20 bushels per acre.
“Most of the marketing of copper doesn’t happen in the less than 0.4 ppm area. It’s in the marginal range. When I left Enviro Test lab in 1997, the marginal rate for copper was 0.4 to 0.6 ppm. Now, I believe it’s close to 1.0 and I recently saw a lab whose cutoff is 2.5 ppm of copper.”
While recommendations are being made to apply copper on soil in this marginal range, Karamanos said the scientific research in Western Canada shows that the critical level for copper is 0.4 ppm.
He said a review of more than 50 studies on copper deficient soils showed that soil testing less than 0.2 ppm had agronomic and economic responses of about $2.50 returned for every dollar spent on copper.
“Both the economic and agronomic response dropped once we moved from 0.2 to 0.3 ppm, but was still advantageous. At 0.4 ppm, both the agronomic and economic response became a break even situation.”
Soil texture was just as important as parts per million levels.
“When we had sandy loams, loamy sands and fine sandy loams, we had huge responses. Once we got to loams, forget it. Even if your soil test is very low on loam soils, you will hardly get any agronomic or economic response,” he said.
“Marginal, we chose to look at 0.4 to 1.2 ppm and there were 50 experiments published for Western Canada on marginal soils. They averaged a 1.75 bu. yield increase and you made 25 cents for every dollar you spent. So you lost 75 cents by applying that.
“Even with sandy loams that have a soil test of 0.6 ppm, you only get back about 23 cents for every dollar spent. This idea of marginal soils where most of the sales of copper occur, is just an idea.”
Karamanos said after analyzing 52 studies on copper deficient soil, he found there was a 94 percent probability of getting an agronomic response and a 62 percent probability of regaining $2 for every dollar spent on copper.
For marginal soil, there was a 16 percent probability of getting an agronomic response and a two percent chance of getting an economic benefit. He said farmers should put that into perspective when they decide what fertilizers they’re going to apply this year.
Manganese
Karamanos said in peat soils near Meadow Lake and Carrot River, Sask., “we got some huge responses to seed-placed manganese: about four to five pounds with oats or barley. If you’re looking for manganese deficiencies on mineral soils, most likely you won’t find one. There are none documented in Western Canada.”
He said the cutoff for peat soils in Manitoba is seven ppm.
“In Saskatchewan, we found it’s the ratio of manganese to copper that determines whether you’re going to have a manganese or copper deficiency. If the Mn:Cu ratio is less than one, you have a manganese deficiency. If it is greater than 15, you can have a copper deficiency because of the strong interaction between these two micronutrients.”
Zinc
With zinc, Karamanos and grad students at the University of Saskatchewan conducted tests at 52 sites in Saskatchewan and were able to find only one response to zinc, at Outlook with irrigated corn.
“We were not able to get any other responses, with cereals or oilseeds. We were down to less than 0.25 ppm and we couldn’t see a response. So when we set the critical level for zinc on cereals, we set it at 0.25 ppm. For corn and beans, it’s 0.5 to 1.0 ppm as the critical levels.”
Some work at the University of Manitoba did find responses to zinc with field beans. For zinc in Manitoba beans, Karamanos said the critical level is 0.5 ppm or one lb. per acre in the top 15 cm.
Iron and molybdenum
For iron and molybdenum, Karamanos said there are no documented micronutrient deficiencies in Western Canada.
“There is anecdotal information for garden soils for iron, but on field crops, we don’t have any documented incidents of iron or molybdenum. Molybdenum in our soils is actually in abundance,” he said.
“The vet college in Saskatoon did some studies on pasture soils in east-central Saskatchewan where they found the Cu:Mo ratio was so low they had cattle suffering from molybdenosis, which is an excess of molybdenum and a lack of copper. You cannot fix the problem in pastures by applying copper, but you can supplement the feed.”
