Onion is one of the most widely grown vegetable crops in India and is used daily in almost every household. Because onions have shallow roots and grow quickly, they need proper nutrition from the soil to produce good-sized bulbs, better colour, and higher yield. Applying the right amount of fertilizer at the right time helps farmers get a healthy crop and avoid unnecessary expenses. Understanding the recommended fertilizer dose is useful for both small and large onion growers.
Before applying fertilizers, it is important to prepare the field well. Onion grows best in loose, well-drained soil. Adding 10–15 tonnes of well-decomposed farmyard manure (FYM) per acre during land preparation helps improve soil structure and increases water-holding capacity. This organic matter also boosts the effect of chemical fertilizers by improving nutrient availability.
For chemical fertilizers, onion generally requires nitrogen (N), phosphorus (P), and potassium (K) in balanced quantities. A commonly recommended dose is:
Nitrogen (N): 50–60 kg per acre
Phosphorus (P₂O₅): 25–30 kg per acre
Potassium (K₂O): 25–30 kg per acre
Phosphorus and potassium should be applied at the time of transplanting, as they help in early root development and strong bulb formation. These nutrients are usually given in the form of single super phosphate (SSP) for phosphorus and muriate of potash (MOP) for potassium.
Nitrogen, however, should not be applied all at once. Onions need nitrogen in small amounts throughout their growth period. If nitrogen is applied heavily at one time, the plants produce more leaves instead of bulbs. To avoid this, farmers should apply nitrogen in three equal splits:
First dose – 15 days after transplanting
Second dose – 30 days after transplanting
Third dose – 45 days after transplanting
Applying nitrogen in splits gives steady growth and helps form bigger bulbs.
Apart from these major nutrients, onions need micronutrients such as sulphur, zinc, and boron. Sulphur is very important because it improves flavour, pungency, and oil content in onions. Many farmers use sulphur-based fertilizers or choose SSP instead of DAP so the crop receives adequate sulphur.
If the leaves turn light green or yellow, the crop may be facing nutrient deficiency. Zinc deficiency causes stunted growth and narrow leaves. Boron deficiency affects bulb formation. Spraying suitable micronutrient mixtures during early growth can help correct these problems.
Proper irrigation also plays a major role in fertilizer use. If water is too much or too little, nutrients cannot reach the roots effectively. Light irrigation immediately after fertilizer application ensures that nutrients move into the soil.
Farmers should also avoid applying fertilizers too close to the bulbs, as this can burn the roots. Always place fertilizers in small furrows beside the plants, not directly on the bulbs.
In summary, onions need balanced nutrition for good bulb size and high yield. By applying FYM during land preparation, providing phosphorus and potassium at transplanting, and supplying nitrogen in splits, farmers can achieve healthy crop growth. With proper fertilizer management and timely irrigation, onion farming becomes more productive and profitable.
