One of the best tools to detect crop nutrient deficiencies in crops could be the farmer’s eyes.

Visual clues may tell a producer what nutrient a crop may need, says PotashCorp Director of Agronomy and eKonomics contributor, Dr. Robert Mullen.

A sharp eye, Mullen says, is especially important in soils that have not had recent lab soil tests.

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Soil tests are helpful in identifying potential nutrient deficiencies, he adds, but monitoring visual cues given by crops is also important.

Those cures include:

  • Upper vs. Lower Canopy – Determine if the abnormality is in the upper (newer growth) or lower (older growth) part of the plant. Problems in the upper canopy typically signify a micronutrient deficiency, while the lower canopy will show macronutrient issues, which can be fixed by applying potassium, nitrogen, phosphorus or magnesium.  
  • Discoloration – Most healthy plants should have evenly colored, deep green leaves. Reddish or purplish leaves usually indicate a phosphorus deficiency, while yellowing leaves often signal a shortage of nitrogen or potassium. The latter can be differentiated by how the yellowing progresses – if it is along the edge, it indicates a potassium shortage, but if it is down the middle of the leaf, the plant is likely deficient in nitrogen.
  • Plant height – Stunted growth is often a sign of a nutrient deficiency. Plants with extremely slow, stunted growth usually represent a potassium or phosphorus shortage, while spindly stalks signify a nitrogen deficiency. A plant with an abnormally small height is a simple way of diagnosing a nutrient deficiency, but this recognition should be used in combination with additional information (plant analysis/soil testing) to identify the particular deficiency and the best course of action. 

Mullen says nutrient deficiencies can result from a number of reasons, but should be diagnosed and fixed as soon as possible, regardless of the cause. “Identifying deficiencies early allows you to take corrective action to minimize damage.”