Explore key principles of effective onion fertilization, including nutrient needs, timing, and best practices for healthy yields in horticulture. This quiz covers practical scenarios and essential facts to help optimize onion crop nutrition.
Which macronutrient is MOST crucial for vigorous onion bulb formation and overall yield during their growth cycle?
Explanation: Potassium is essential for onion bulb development, size, and resistance to diseases. While nitrogen supports leafy growth, too much can hinder bulb formation. Phosphorus is important for root development but less directly related to bulb size. Calcium helps cell structure but is not as critical for bulb yield as potassium.
When is the BEST time to apply the majority of nitrogen fertilizer to an onion crop for optimal growth?
Explanation: Onions need most of their nitrogen during early vegetative growth to establish strong leaves that support bulb growth. Applying at planting may lead to leaching losses. Late application can cause excessive top growth and delay bulb maturity. After harvest application provides no benefit.
If you notice pale yellowing of older onion leaves with poor bulb development, which nutrient deficiency is MOST likely responsible?
Explanation: Nitrogen deficiency often causes general yellowing of lower leaves and poor bulb development. Potassium deficiency can appear as leaf tip burn but rarely causes such widespread yellowing. Magnesium or sulfur deficiencies have different, more specific symptoms like interveinal chlorosis.
Applying too much nitrogen fertilizer to onions is likely to result in which problem?
Explanation: Excessive nitrogen promotes leafy growth and can delay bulb formation, causing thick necks and smaller, poorly formed bulbs. While it does not improve disease resistance or result in earlier maturity, proper nitrogen supports uniform bulbs, but overapplication has the opposite effect.
Which organic amendment is commonly used to supply slow-release nitrogen to onions in sustainable horticulture systems?
Explanation: Composted poultry manure is a widely used organic source of slow-release nitrogen for onions. Vermiculite is a soil conditioner, not a significant nutrient supplier. Dolomite lime is chiefly for calcium and magnesium, while rock phosphate provides phosphorus.