The Onion Fertilizer Challenge Quiz

Explore essential knowledge about fertilizing onions for optimal horticultural growth and yield. This quiz covers nutrient needs, application timing, and common cultivation practices.

1. Essential Nutrients for Onion Growth

   Which primary nutrient should be most abundant in fertilizers for strong onion bulb formation?

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

   Explanation: Potassium plays a crucial role in bulb development and helps onions resist diseases. Nitrogen is needed for leafy growth but can reduce bulb size if overused. Phosphorus is important for root growth but is not the main nutrient for bulb formation. Calcium is necessary in small amounts but does not directly support bulb development like potassium.

2. Fertilizer Application Timing

   When is the best time to apply nitrogen-rich fertilizer to onion plants?

   1. At harvest
   2. Immediately after bulb swelling begins
   3. During flower formation
   4. At seedling emergence

   Explanation: Applying nitrogen at seedling emergence encourages robust vegetative growth, setting a good foundation. Applying it after bulb swelling may delay desired bulb development. During flower formation, it is generally too late for the desired vegetative effect. Fertilizing at harvest serves no purpose since crop growth is complete.

3. Fertilizer Burn Symptoms

   What is a common sign that onion seedlings have been damaged by over-fertilization?

   1. Deep green leaves
   2. Bulbs splitting
   3. Yellow, scorched leaf tips
   4. Increased pest activity

   Explanation: Yellow, scorched leaf tips indicate salt damage from excess fertilizer. Deep green leaves generally show adequate nutrition, not damage. Bulbs splitting may occur from irregular watering rather than over-fertilization. Increased pest activity is not a direct symptom of fertilizer burn.

4. Organic Versus Synthetic Fertilizers

   Which fertilizer type improves soil structure while providing nutrients to onions?

   1. Rock phosphate
   2. Synthetic urea
   3. Organic compost
   4. Ammonium nitrate

   Explanation: Organic compost enhances soil structure and fertility as it decomposes. Synthetic urea and ammonium nitrate supply nutrients but do not improve soil structure. Rock phosphate is a mineral fertilizer rich in phosphorus but does not boost soil organic content or structure.

5. Micronutrients in Onion Cultivation

   Which micronutrient is especially important in preventing onion leaf tip dieback?

   1. Iron
   2. Magnesium
   3. Boron
   4. Zinc

   Explanation: Boron helps prevent leaf tip dieback and is vital for onion health. Zinc deficiency more commonly affects growth rates, iron relates to leaf chlorosis, and magnesium is involved in photosynthesis but not specifically in tip dieback prevention for onions.