Soil testing more relevant than ever

If you don’t know what nutrients are in the soil it’s hard to meet your crop’s needs

To optimize crop yields, Ieuan Evans, a well-known western Canadian plant pathologist, urges farmers to get back to the basics — do a soil test and follow the recommendations.

Evans, speaking to farmers at the Ag In Motion farm show near Saskatoon in July says farmers have been advised since the beginning of modern agriculture to make soil testing a routine management practice and yet many producers still fly by the seat of their pants.

“You talk to a farmer and he may say I have “good” land here and “poor” land there, but the fact is they really don’t know what they have,” says Evans, a senior coach with AgriTrend Agrology.

“They may go out every year and apply nitrogen, phosphorus, potassium and sulphur (NPKS), but that may be at rates they use year after year and many just don’t consider the total nutrient package which also includes micronutrients. A farmer may be applying nitrogen and phosphorus but if one or more of the other macro or micro nutrients is limiting that can affect the health of the crop, the standability and ultimately the yield.”

Evans, in a sometimes colorful and occasionally frank criticism of some agronomic recommendations made to producers, says farmers need to look at the whole macro and micro nutrient package.

Look at the facts

He referred to a crop nutrient removal chart available on Alberta Agriculture’s Ropin’ the Web — and there are similar versions available from other provincial departments of agriculture — which point out for example, an 80-bushel barley crop will remove 78 pounds of nitrogen, 34 pounds of phosphate, 25 pounds of potash and seven pounds of sulphur. Those are macronutrients, but at the same time that 80-bushel crop also requires to varying levels of calcium, magnesium, boron, copper, iron, manganese and zinc.

“It is just a fact of biology, that an 80-bushel barley crop will require those levels of four macronutrients and seven micronutrients,” says Evans. “And if one or more is missing the yield and quality potential of that crop can be adversely affected.

“And farmers need to start with a soil test to know what is available in the soil and then fertilize accordingly.”

Evans who has long been a proponent of what he considers is the important yet often overlooked role of copper in a crop nutrient program says about 20 per cent of Alberta farmland (peat and sandy soils) are chronically deficient in copper, while another 20 per cent are routinely deficient in periods of high moisture. It is a similar situation in Saskatchewan, and some soils in south central Manitoba are also chronically deficient.

“I visited one farm near Ituna, Saskatchewan, where a farmer had an 80-bushel wheat crop and part of the field was badly lodged,” says Evans. “The crop was lodged in all the low spots. If wind had been the problem the crop would have lodged in the high spots. They had received several inches of rain earlier in the growing season, those soils in the low spots were high in organic matter and the copper had moved into the subsoil where plant roots couldn’t reach it.”

In another case, Evans was asked by an Alberta farmer to investigate what the farmer believed was a situation of herbicide injury on a barley crop following a treatment by a custom applicator. It wasn’t herbicide injury. The farmer had received a fertilizer recommendation that called for 120 pounds of nitrogen as well as a four pounds of copper per acre. He followed his normal practice of applying 100 pounds of 10-15-10 fertilizer, with no added copper. It was a poor crop that yielded about 40 bushels per acre. The following year the farmer applied the recommended fertilizer rate that included 120 pounds of nitrogen, plus copper and the crop yielded 140 bushels per acre.

“There are no quick fixes or silver bullets,” says Evans. “You can’t just apply one new miracle product and start optimizing yields. You need to look at the whole nutrient program, and that starts with a soil test ideally every year or at least every couple years and then make sure the crop has was it needs.”

With copper in particular, he says wheat varieties tend to be the most sensitive, some barley varieties and a few oat varieties, to deficiency. Flax is also often sensitive to a copper deficiency. And most of these crops can be sensitive when pushed toward higher yields. And referring to organic crop production, he says it becomes a real challenge for organic producers to provide the total nutrient package. If they are not using commercial fertilizer blends they end up mining the soil.

About the author

Field Editor

Lee Hart

Lee Hart is editor of Cattleman’s Corner based in Calgary.

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