Many nutrient deficiency symptoms in crop plants look similar and may be confused with damage from frost, insects, disease or herbicide drift. To confirm the cause of symptoms in your crop, you can consult your local provincial crops specialist, consult a soil fertility expert or send tissue samples to a lab with tissue-testing capabilities. An accurate diagnosis of the problem and the causal agent is needed to ensure that correct measures can be initiated.
Soil nutrients are essential to the production of a healthy, high-yielding crop. Soil tests are the best source of information on nutrient levels in the soil. A watchful producer can spot physical symptoms of a deficiency and confirm the diagnosis with a soil or tissue test.
Learning to read deficiencies
- Chlorosis or yellowing of plant parts, especially an interveinal chlorosis in leaves, is common when production of chlorophyll is interrupted. Chlorosis is usually followed by necrosis (the dying of plant tissue). Almost all deficiencies can manifest in this way, but it is especially evident in nitrogen (N) and iron (Fe) scarcities.
- Leaf loss occurs often, as the chlorosis leads to necrosis and leaves die.
- Symptoms that appear first on younger leaves are generally micronutrient shortages, as these nutrients do not translocate (move) in the plant.
- Purpling of plant parts — stems, leaves, veins, petioles, roots and flower parts — commonly shows up in older plants short on nitrogen (N) and phosphorus (P).
- Stunted growth is displayed in almost all deficiencies as plants struggle to survive and grow. Flowering and/or fruit setting that is deformed and/or aborted is also common.
Indicators by nutrient
- Nitrogen (N) is transferred from older to younger leaves, so older leaves will be the first to display deficiency symptoms by yellowing and turning purple.
- Plants lacking phosphorus (P) will display what is called “hidden hunger,” where plants are stunted with thin stalks. In addition, older leaves can develop a bluish tinge.
- A potassium (K) shortage will exhibit itself with tips of older leaves that turn brown and brittle before they drop off.
- Sulphur (S) deficiency presents with small leaves that will cup around the stem, which is especially evident in canola. Flower buds will be white instead of yellow.
- When copper (Cu) is scarce, “pigtailing” or spiralling of older leaves can occur; they will kink at the ends, especially in cereal crops.
- Zinc (Zn) deficiency shows up in flax as greyish brown spots and cereal leaves may turn bronze.
- Oats are more susceptible than other cereal crops to insufficient manganese (Mn), which shows up as “grey speck” on the leaves.
- When boron (B) is in short supply, symptoms include thickened, misshapen leaves. A “witch’s broom” effect occurs when the terminal bud or growing point dies off, resulting in poor seed set.
- Iron (Fe) chlorosis shows up as severe interveinal yellowing that can eventually result in bleached, almost white leaves.
Some deficiencies will show up early in a crop’s development and others later in the season. If a crop shows symptoms of a nutrient deficiency early on, the symptoms may recede as the growing season progresses. Scouting fields for these symptoms and for other problems is always a good practice.
Joanne Kowalski is a Regional Crops Specialist with Saskatchewan Agriculture.