The Yellowing Leaves Mystery Quiz

Explore key concepts in plant nutrition within agriculture, focusing on nutrient deficiencies and their signs. Learn how various factors impact plant health and crop yield.

1. Nitrogen Deficiency Symptoms

   A farmer notices that older leaves on her corn plants are turning yellow while new growth remains green. Which nutrient is most likely deficient?

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

   Explanation: Nitrogen deficiency often causes yellowing of older leaves first as nitrogen is mobile within the plant. Phosphorus deficiency usually leads to purpling, potassium deficiency causes leaf edge browning, and calcium affects new leaves, not older ones.

2. Fertilizer Application Timing

   Why is it important to apply fertilizers at the right growth stage for crops such as wheat?

   1. To maximize nutrient uptake
   2. To reduce wind damage
   3. To increase soil acidity
   4. To prevent pest infestation

   Explanation: Applying fertilizers at the correct growth stage ensures plants absorb nutrients efficiently, leading to better yields. Pest control and wind damage are unrelated to fertilizer timing, and increasing soil acidity is generally undesirable.

3. Micronutrient Importance

   Which micronutrient, though required in small amounts, is essential for chlorophyll production and can cause broad yellowing if absent?

   1. Iron
   2. Sulfur
   3. Magnesium
   4. Sodium

   Explanation: Iron is needed in small quantities for chlorophyll synthesis; its deficiency often shows as yellowing between leaf veins. Magnesium and sulfur are needed in larger amounts (macronutrients), and sodium is not essential for most plants.

4. Soil pH Effects

   How can highly acidic soil pH affect the availability of plant nutrients such as phosphorus?

   1. It makes phosphorus less available
   2. It increases nitrogen fixation
   3. It always improves nutrient uptake
   4. It prevents root growth

   Explanation: Low (acidic) soil pH can lock up phosphorus, making it harder for plants to access. Acidic soils do not improve nutrient uptake or nitrogen fixation and may slow, but not entirely prevent, root growth.

5. Water and Nutrient Uptake

   During a drought, crop leaves turn yellow and wilt. What is the primary reason for reduced nutrient uptake in these conditions?

   1. Excess potassium
   2. High leaf humidity
   3. Too much sunlight
   4. Insufficient soil moisture

   Explanation: Lack of soil moisture limits the plant's ability to absorb nutrients through its roots, leading to yellowing and wilting. Excess potassium, sunlight, and leaf humidity do not directly cause the same widespread nutrient uptake issues.