Identify common nutrient deficiencies in your chili plants by observing leaf color and symptoms, and learn about potential remedies and general fertilizer application rates. This guide provides a general overview; for precise diagnosis, soil testing is highly recommended.
Nitrogen (N) Deficiency
Leaf Color/Symptoms: Leaves are uniformly pale yellow-green to yellow, especially on older/lower leaves. Growth is stunted, and leaves may be small. Severe deficiency can lead to premature leaf drop.
Fertilizer Recommendation: Apply a nitrogen rich fertilizer (e.g., NPK ratio like 10-5-5 or 20-10-10).
Approx. Rate: For liquid feeds, 1/2 to 1 teaspoon per gallon of water every 2-4 weeks. For granular, follow product instructions for light feeding. Organic options: blood meal, compost, or fish emulsion.
Phosphorus (P) Deficiency
Leaf Color/Symptoms: Leaves may turn dark green, often developing a distinct reddish or purplish tint, particularly on older leaves and stems. Stunted growth, reduced leaf size, and delayed flowering/fruiting are also common.
Fertilizer Recommendation: Use a fertilizer with higher phosphorus content (e.g., NPK ratio like 5-10-5 or 10-20-10).
Approx. Rate: For liquid feeds, 1/2 to 1 teaspoon per gallon of water, applied as a soil drench. For granular, incorporate bone meal into the soil (follow product rates).
Potassium (K) Deficiency
Leaf Color/Symptoms: Yellowing, bronzing, or browning (scorching/burning) of leaf margins and tips, typically starting on older leaves. Leaves may appear deformed or droopy, and growth can be stunted.
Fertilizer Recommendation: Apply a fertilizer with higher potassium content (e.g., NPK ratio like 5-5-10 or 10-10-20).
Approx. Rate: For liquid feeds, 1/2 to 1 teaspoon per gallon of water. For granular, use sul po mag or green sand (check product instructions). Organic options: wood ash (sparingly) or kelp meal.
Magnesium (Mg) Deficiency
Leaf Color/Symptoms: Interveinal chlorosis (yellowing between the veins while the veins remain distinctly green), typically starting on older leaves. Yellowing can progress to reddish-purple hues, and leaves may become brittle.
Fertilizer Recommendation: Epsom salts (magnesium sulfate).
Approx. Rate: 1 tablespoon Epsom salts per gallon of water as a foliar spray (avoid full sun) or soil drench every 2-4 weeks until symptoms improve. Dolomitic lime can also provide magnesium and adjust pH over time.
Calcium (Ca) Deficiency
Leaf Color/Symptoms: Primarily affects new growth and growing points. Young leaves may be distorted, curled upwards, have tiny black spots, or die back. Blossom end rot is a common fruit symptom.
Fertilizer Recommendation: Ensure consistent soil moisture. Apply calcium nitrate or use bone meal, ground eggshells, or gypsum.
Approx. Rate: For calcium nitrate, use 1 tablespoon per gallon of water as a soil drench, or as per product instructions.
Iron (Fe) Deficiency
Leaf Color/Symptoms: Interveinal chlorosis on young leaves, with veins remaining distinctly green. In severe cases, the entire young leaf may turn pale yellow or almost white. Often appears when soil pH is too high (alkaline).
Fertilizer Recommendation: Apply chelated iron (iron chelate).
Approx. Rate: Use as per specific product instructions, typically a few drops or a small amount mixed in water for foliar spray or soil drench. Adjust soil pH if alkaline to improve iron availability.
Sulfur (S) Deficiency
Leaf Color/Symptoms: Uniform pale yellowing of new, younger leaves. Stunted growth. Can resemble nitrogen deficiency but affects new growth first because sulfur is less mobile.
Fertilizer Recommendation: Apply a fertilizer containing sulfur, such as ammonium sulfate or gypsum. Organic matter in soil also releases sulfur.
Approx. Rate: Apply granular gypsum or elemental sulfur as per package directions, often a few tablespoons per plant or per square foot.
Important Disclaimer & Best Practices
Visual diagnosis is a helpful tool for a quick assessment, but it’s not always precise. Many factors like soil pH, overwatering, underwatering, pests, or diseases can cause similar symptoms to nutrient deficiencies.
The fertilizer rates provided above are approximate and for general guidance. Always refer to the specific instructions on your chosen fertilizer product, as concentrations can vary greatly. Starting with a lower dose is always safer to prevent “fertilizer burn.”
For the most accurate determination of your chili plant’s nutritional needs, it is highly recommended to perform a soil test. This will provide detailed information about your soil’s nutrient levels and pH.