How To Prevent Yield Fall in Fruit Farming: Stopping Alternate Bearing

Have you ever noticed that your fruit trees give a lot of fruits one year, then very few the next year? This is called irregular bearing, also known as alternate bearing or biennial bearing.

It is a common challenge for fruit farmers in Kenya, especially those in avocado farming, even though citrus, apples, pears, and mango farmers also feel the pinch.

Alternate Bearing: One year's high yield leading to poor yield the next year

Alternate bearing occurs when a heavy yield in one year (the "on-year") depletes the tree’s “energy” – particularly carbohydrates, nutrients, and sometimes hormonal reserves – leading to reduced flowering or fruit set in the following year (the "off-year").

Controlling irregular bearing involves strategies to balance the tree’s reproductive and vegetative growth, manage resource allocation, and mitigate the stress of heavy cropping. Here’s how You can do it:

 

1. Fruit Thinning

Reducing the number of fruits on a tree in an "on-year" prevents the tree from overexerting itself, preserving carbohydrate reserves for the next season’s flowering.

How to Do It:

Manual Thinning: Physically remove excess young fruit shortly after fruit set (e.g., in avocados, thin when fruitlets are pea-sized). Aim to leave a sustainable number based on tree size and vigor.

Example: For avocados, thin to one fruit per cluster; for apples, aim for one fruit every 6-8 inches along branches.

 

2. Pruning

Pruning regulates the balance between vegetative growth and fruit production, preventing the tree from overloading with fruit in one year.

How to Do It:

Post-Harvest Pruning: After an "on-year" harvest, prune lightly to remove excessive fruiting wood and encourage new vegetative shoots, which will bear next year’s crop.

Annual Maintenance: Regular pruning (e.g., removing dead wood, thinning crowded branches) improves light penetration and air circulation, supporting consistent energy allocation.

Example: In avocados, avoid heavy pruning during flowering, but trim back vigorous shoots post-harvest. For apples, thin fruiting spurs annually.

 

3. Nutrient Management

Adequate and timely nutrition replenishes reserves depleted by a heavy crop, supporting bud formation for the next year.

How to Do It:

Post-Harvest Feeding: Apply a balanced NPK (nitrogen, potassium, phosphorus) fertilizer after harvest in the "on-year" to rebuild reserves. For avocados, zinc and boron are also critical.

Avoid Over-Fertilization: Excessive nitrogen in the "off-year" can push vegetative growth over flowering so you should time your fertilizer applications to support the growth of new shoots just before the setting in of the flowering season.

Soil Testing: You should do your soil testing annually in order to monitor soil nutrient levels to ensure that the nutrients depleted by trees are quickly replenished.

 

4. Irrigation Management

Consistent water supply reduces stress that amplifies irregular bearing, ensuring the tree can support both current fruit and next year’s buds.

Maintain even soil moisture during fruit development and post-harvest, avoiding drought or waterlogging.

Apply organic mulch to retain moisture and regulate soil temperature, supporting root health year-round.

 

5. Variety Selection and Rootstock

Some varieties and rootstocks are less prone to alternate bearing due to genetic traits or vigor.

For example, in avocado, the Hass variety is less erratic than Fuerte with proper management. In apples, ‘Gala’ or ‘Fuji’ may bear more consistently than ‘Granny Smith’.

Dwarfing rootstocks (e.g., M9 for apples) can moderate vigor and promote regular cropping compared to vigorous ones.

 

7. Crop Load Forecasting

Anticipating a heavy crop allows proactive intervention before resources are depleted. Assess the bloom intensity as soon as your fruit trees start flowering. Heavy flowering indicates a potential "on-year" which calls for thinning as explained earlier.

Also, track production patterns over years to predict and manage cycles.

 

Important Notes

Avocados are particularly prone to irregular bearing due to their high fruit load potential and sensitivity to environmental stress. Avocado farmers should therefore be very keen to ensure a balanced soil nutrient level all the time, cross-pollination by planting Hass and Fuerte varieties together, and finally, avoiding water stress during the prolonged fruit development season.

Breaking the irregular bearing cycle takes 2-3 years of consistent management. Start by reducing the "on-year" crop load and supporting recovery in the "off-year" with nutrition and pruning. Over time, the tree’s internal resource balance stabilizes, leading to more predictable yields.