Ratoon Crop Nutrient Mastery Quiz

Explore essential nutrient management practices for higher sugarcane ratoon yields. Assess your understanding of fertilizer strategies, timing, and key agronomic choices.

1. Optimal Nitrogen Timing

   When should the majority of nitrogen fertilizer be applied to a sugarcane ratoon crop for maximum uptake efficiency?

   1. Immediately after harvesting the plant crop
   2. Just before final irrigation
   3. During the late tillering stage
   4. At the time of flowering

   Explanation: Applying nitrogen immediately after harvesting the plant crop supports rapid regrowth and ensures availability during early tillering. Late tillering and flowering stages are too late for optimal root uptake, reducing effectiveness. Application before final irrigation might lead to leaching losses or inefficient supply to developing shoots.

2. Micronutrient Deficiency Indicator

   Yellowing of young leaves in sugarcane ratoon crops often signals a deficiency of which nutrient?

   1. Magnesium
   2. Calcium
   3. Iron
   4. Potassium

   Explanation: Iron deficiency typically causes chlorosis (yellowing) in young leaves, due to its role in chlorophyll formation. Magnesium deficiencies affect older leaves, potassium leads to edge burn, and calcium generally affects growing points rather than leaf color.

3. Phosphorus Placement Technique

   What is the recommended method for applying phosphorus fertilizer in sugarcane ratoon fields to improve availability?

   1. Applying with irrigation water
   2. Broadcasting on the soil surface
   3. Foliar spraying
   4. Band placement near the ratoon stools

   Explanation: Band placement near the ratoon stools ensures phosphorus is accessible to developing roots. Broadcasting can result in fixation and reduced uptake, foliar sprays are not effective for phosphorus, and applying with irrigation may lead to uneven distribution and losses.

4. Potassium's Primary Function

   Why is potassium especially important for ratoon sugarcane crops?

   1. It is the main component of chlorophyll
   2. It directly increases nitrogen uptake
   3. It initiates tiller sprouting
   4. It enhances juice quality and disease resistance

   Explanation: Potassium reinforces cell walls, improves juice quality, and helps plants resist stress and disease. Chlorophyll requires magnesium, not potassium. While potassium supports overall plant health, it is not the main driver of nitrogen uptake or tiller sprouting.

5. Split Application Benefit

   What is the primary advantage of splitting nitrogen fertilizer applications across two or more intervals in ratoon management?

   1. Rapidly accelerates ratoon emergence
   2. Reduces risk of leaching and improves nutrient use efficiency
   3. Increases immediate yield but lowers soil fertility
   4. Eliminates the need for phosphorus application

   Explanation: Splitting nitrogen applications allows for better synchronization with crop demand and minimizes losses due to leaching. It does not directly alter ratoon emergence speed or replace the need for phosphorus. Increasing yield at the expense of soil fertility is not an intended consequence.