Model Answer
0 min readIntroduction
Alternate bearing, also known as biennial bearing, is a phenomenon observed in certain perennial fruit crops where a tree produces a heavy crop in one year (on-year) followed by a significantly reduced crop in the subsequent year (off-year). This irregular fruiting pattern negatively impacts yield and farmer income. While common in mango and apple cultivation, the underlying causes and effective management strategies differ. Understanding these nuances is critical for optimizing fruit production and ensuring sustainable agricultural practices. The phenomenon is linked to carbohydrate reserves and hormonal imbalances.
Alternate Bearing in Mango
Mango (Mangifera indica) exhibits pronounced alternate bearing. The primary causes include:
- Nutrient Depletion: Heavy cropping depletes stored carbohydrates and nutrients, hindering flower bud initiation in the following year.
- High Temperatures & Water Stress: Erratic rainfall and fluctuating temperatures during flower bud differentiation stages can disrupt the process.
- Hormonal Imbalances: Gibberellins (GA) promote flowering while auxins inhibit it. Imbalance in these hormones contributes to alternate bearing.
- Bud Dormancy: Inadequate chilling hours in certain mango varieties can disrupt the bud dormancy cycle, leading to erratic flowering.
Measures to Overcome Alternate Bearing in Mango
- Nutrient Management: Application of fertilizers, especially phosphorus and potassium, during flower bud differentiation (September-October) helps replenish nutrient reserves.
- Pruning: Selective pruning to reduce the number of fruiting spurs can lessen the burden on the tree.
- Growth Regulators: Application of plant growth regulators like Paclobutrazol can help control vegetative growth and enhance fruit set, reducing the impact of alternate bearing.
- Irrigation: Providing adequate and timely irrigation during critical stages like flowering and fruit development is essential.
Alternate Bearing in Apple
Apple (Malus domestica) is also susceptible to alternate bearing, though often less severe than mango. The causes are:
- Chilling Requirement: Insufficient chilling hours (600-1000 hours depending on the variety) disrupts dormancy and flowering.
- Photosynthetic Imbalance: Heavy fruit load reduces photosynthetic activity, leading to carbohydrate deficits.
- Vigor and Tree Age: Young and highly vigorous trees are more prone to alternate bearing.
- Rootstock Influence: The rootstock used for grafting significantly affects the tree's vigor and bearing habit.
Measures to Overcome Alternate Bearing in Apple
- Dormant Pruning: Reducing the number of fruit buds during dormancy can mitigate the impact of heavy cropping.
- Chemical Thinning: Applying chemical thinning agents like ethephon after bloom can reduce fruit load and promote flowering in the following year.
- Chilling Injury Mitigation: Using reflective mulches or applying antitranspirants can help increase chilling hours.
- Rootstock Selection: Choosing appropriate rootstocks that promote balanced growth and fruiting is crucial. M.9 rootstock is known to reduce alternate bearing.
| Fruit | Primary Cause(s) | Mitigation Strategies |
|---|---|---|
| Mango | Nutrient depletion, temperature stress, hormonal imbalance | Fertilization, pruning, growth regulators, irrigation |
| Apple | Chilling requirement, photosynthetic imbalance, vigor | Dormant pruning, chemical thinning, chilling injury mitigation, rootstock selection |
Conclusion
Alternate bearing poses a significant challenge to mango and apple production, impacting yield and farmer livelihoods. Addressing this issue requires a holistic approach combining nutritional management, pruning techniques, judicious use of plant growth regulators, and appropriate water management. Furthermore, selecting suitable varieties and rootstocks tailored to the prevailing climatic conditions is crucial for mitigating the problem and ensuring sustainable fruit production. Further research into hormonal regulation and genetic improvements could offer long-term solutions.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.