Crop nutrition basics
Plants need 17 essential nutrients. Three come from air and water, and the rest come from the soil or from fertilizer. When one is missing, the plant shows symptoms, often on specific leaves. Learning to read those symptoms helps you correct the problem early.
Major nutrients
- Nitrogen (N): leaves turn pale green or yellow, starting with the older leaves. Growth is slow.
- Phosphorus (P): older leaves turn dark green or purple, and root growth is weak.
- Potassium (K): the edges of older leaves scorch or turn brown, and the plant is weak against stress.
- Sulphur (S): young leaves turn pale and yellow, and the plant looks stunted. Sulphur also supports oil content in oilseeds.
Secondary and micronutrients
- Calcium (Ca): young leaves are distorted, and fruit can develop blossom end rot.
- Zinc (Zn): young leaves show yellow patches between the veins, and the plant may grow short.
- Iron (Fe): young leaves turn yellow while the veins stay green.
- Boron (B): growing tips die back, and flowers or fruit may drop or be misshapen.
Check before you correct
Symptoms can look alike. Waterlogging, pests, disease and herbicide injury can all cause yellowing. Before you add fertilizer, check the pattern on the plant, check the soil, and consider the stage of the crop. A soil test is the most reliable way to see what is missing.
Feed the plant, feed the soil
Organic matter, humic substances and soil biology help roots take up nutrients. Foliar sprays give a fast fix for a visible deficiency, while soil applications build reserves over the season. Use both as the crop and the soil need.