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Getting to the root cause of crop deficiencies

Getting to the root cause of crop deficiencies

Plants may lack potassium and manganese at this time of year

By Kaitlynn Anderson
Staff Writer

Soybean growers across the province may want to keep an eye on the health of their crops.

Many Ontario fields show signs of potash and manganese deficiencies, Steph Kowalski, an agronomy lead at the Agronomy Company of Canada Ltd., told yesterday.

To identify these nutrient deficiencies, producers can look at the soybeans’ leaves.

If a plant lacks potassium, its leaves will begin to yellow along the margins, Thursday’s OMAFRA field crop report said.

Manganese deficiency, in contrast, causes entire leaves – except the veins – to become yellow. This symptom will first appear on younger leaves.

Different factors cause these problems.

Potassium deficiency tends to appear in areas where crops have not established strong root systems. Sidewall compaction and a lack of rainfall can contribute to this situation, the report said.

Plants may also struggle to absorb potash in dry conditions, even if soils contain sufficient levels of this nutrient.

If farmers do not address these deficiencies, their fields could suffer.

“Soybeans take up and remobilize a considerable amount of potassium to produce the crop,” Kowalski said. “Whenever you short one of those macronutrients, you are looking at substantial yield loss.”

Unfortunately, producers may be unable to reverse the damage, as many fields are too far into the growing season.

“It’s difficult to alleviate (potassium) deficiency now, since foliar products cannot supply enough (potash) through the leaf tissue to rectify the problem,” the report said.

However, in late-planted fields that severely lack this nutrient, farmers may still be able to apply dry potash, the report stated.

Soybeans could fall victim to manganese deficiency, in contrast, if the fields have unfavourable pH levels.

“As soil pH increases, less manganese is available to the plant,” the report said.

This nutrient deficiency tends to become an issue on poorly drained soils, such as clays and silt loams, and fields with high levels of organic matter, the report said.

To prevent this deficiency from damaging their crops, growers can apply a foliar manganese. By taking this step, farmers could see their yields improve by up to eight bushels per acre, the report said.

Growers can take soil samples to identify which nutrients their crops need. When submitting these tests, farmers may want to ask the lab to look for soybean cyst nematode, as this pest can cause plants to show symptoms similar to the signs of potassium deficiency.

For more information on weeds, pests and crop diseases, check out the Field Guide.



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