Explore key facts about fertilizing onions for healthy bulb growth and high yields. This quiz covers essential nutrients, application methods, and common fertilization practices for onions in horticulture.
Which macronutrient plays the most crucial role in promoting onion bulb development?
Explanation: Potassium is vital for onion bulb formation, size, and overall yield because it promotes carbohydrate movement in plants. Phosphorus helps root development but isn't the main driver for bulb growth. Nitrogen encourages leafy growth and, if overapplied, may delay bulb maturity. Calcium supports cell structure but is less critical specifically for bulb enlargement.
When is the best stage to reduce or stop nitrogen fertilization for onions?
Explanation: Nitrogen should be reduced or stopped at the start of bulb formation to avoid excessive leaf growth and poor bulb quality. After sowing and early seedling stages both require adequate nitrogen for establishment. Applying nitrogen just before harvest has limited value and can negatively affect storage.
Which visual symptom most commonly indicates a nitrogen deficiency in onion plants?
Explanation: Nitrogen deficiency in onions typically appears as yellowing (chlorosis) of the older leaves, as nitrogen is mobile and moves from older to newer tissues. Purple leaf tips usually suggest phosphorus deficiency. Leaf tip burn is more related to salt stress or potassium issues. Curling of leaves can be caused by pests or environmental stresses, not specifically low nitrogen.
What is the optimal soil pH range for onion growth and nutrient uptake?
Explanation: A slightly acidic soil pH of 5.8 to 6.5 is ideal for onions, ensuring the best nutrient availability. Lower pH makes nutrients less available and can harm growth; the higher ranges (7.5 and above) can lead to micronutrient deficiencies and reduced onion performance.
Which fertilizer application method is commonly used to provide nutrients directly to onion roots?
Explanation: Band placement involves applying fertilizers close to onion rows, supplying nutrients directly to the root zone and improving efficiency. Broadcasting can waste nutrients and is less targeted. Foliar sprays mostly supplement micronutrients, not primary fertilization. Top dressing after harvest offers no benefit to the current crop.