Onion Nutrient Know-How Quiz Quiz

Discover key facts about nutrient management, deficiencies, and best practices for onions. Explore essential elements that influence healthy onion growth in horticultural settings.

1. Essential Macronutrient for Onion Bulb Formation

   Which macronutrient is most closely associated with promoting large bulb development in onions during cultivation?

   1. Potassium
   2. Calcium
   3. Nitrogen
   4. Phosphorus

   Explanation: Potassium is crucial for large bulb formation, improving bulb size and quality in onions. While nitrogen supports leafy growth and phosphorus assists in root development, they are less specifically linked to bulb sizing. Calcium is important for structural integrity but not as directly involved in bulb enlargement as potassium.

2. Visual Symptom of Nitrogen Deficiency

   When onions experience a nitrogen deficiency, what is the most common visible symptom observed in their leaves during early growth?

   1. Purple leaf margins
   2. Red streaks on leaves
   3. Leaf curling
   4. Yellowing of older leaves

   Explanation: Nitrogen deficiency typically causes yellowing (chlorosis) of older onion leaves because nitrogen is mobile in the plant and moves to newer growth. Red streaks and purple margins are more indicative of phosphorus or other micronutrient shortages. Leaf curling usually relates to pests or environmental stress rather than nitrogen.

3. Soil pH for Optimal Nutrient Uptake

   For efficient nutrient absorption in onions, what is the ideal soil pH range recommended for commercial horticulture?

   1. 7.0–7.5
   2. 5.8–6.5
   3. 6.8–7.8
   4. 5.0–5.5

   Explanation: A soil pH of 5.8–6.5 is optimal for onion nutrient uptake and growth, ensuring availability of key nutrients. Values below 5.5 can restrict root function, while a pH above 7.0 may lead to micronutrient deficiencies. The range 6.8–7.8 is slightly alkaline, which is less favorable for onions.

4. Micronutrient Commonly Deficient in Onions

   Which micronutrient deficiency is most commonly reported in onion crops, leading to symptoms such as leaf tip dieback and poor bulb quality?

   1. Manganese
   2. Boron
   3. Sulfur
   4. Zinc

   Explanation: Boron deficiency commonly leads to leaf tip dieback and reduced bulb quality in onions. While zinc and manganese are vital, deficiencies are less frequently observed in onions. Sulfur is a secondary macronutrient, not a micronutrient, though it also plays a significant role in flavor and health.

5. Best Practice for Fertilizer Application in Onions

   In horticultural onion production, which fertilizer application method is preferred to maximize nutrient uptake while minimizing waste?

   1. Split application based on growth stage
   2. Foliar feeding exclusively
   3. Top-dressing with slow-release granules
   4. Broadcasting all fertilizer pre-planting

   Explanation: Split application aligns nutrient supply with crop demands at different growth stages, improving uptake and reducing losses. Broadcasting and top-dressing can lead to nutrient wastage, while exclusive foliar feeding does not meet all nutritional needs for bulbing onions.