Factors to consider when growing avocados
Sourcing of good planting materials
Certified nurseries- Farmers are advised to get seedlings from the nurseries that are certified by Ministry of Agriculture.
Grafted varieties-Farmers should plant grafted avocado varieties. Grafting improves the variety by increasing resistance to diseases, improves yield and increase adaptability to different soils. Grafted varieties include ;
- They have great demand both locally and abroad due to their sweetness, high oil content, takes long to ripen thus can withstand long distance transportation as compared to local varieties
Physical soil attributes-Avocado requires well aerated, well-drained soil for healthy root growth. Avocado is highly affected by waterlogging which causes Phytophthora root rot. No avocado rootstock is completely resistant to this disease.
Chemical soil attributes: soil analysis-Farmers should undertake soil testing from well acknowledged laboratories as this will enable the farmer know the right type of manure or fertilizers to apply in order to obtain vigorous plant growth and good yield.
Avocado requires an altitude of 1000m-2,500m above sea level.
Avocado grows and produces best in cool or warm areas with temperatures of between 15°C – 30°C. Most varieties have little tolerance to extreme cold but generally, avocadoes produce bigger fruits in warm areas that in hot areas.
The sensitivity of trees to low temperature is influenced by a wide range of factors including:
• The age of the tree and stage of growth – young trees and those with young shoots are more adversely affected by cold.
• Growth vigor and health – plants that have vibrant growth are less affected.
• The duration and frequency of low temperature – Trees that often experience prolonged periods of cold weather develop resistance to cold.
Temperatures that are constantly above 36°C also have disastrous effects to any variety of avocados.
Avocado trees have significant tolerance to drought but thrive and produce most fruits in areas with well distributed rainfalls of between 1000-1600mm per year. In dry areas, irrigation can be used to meet the tree’s water needs.
Too much rain during flowering leads to shedding of flowers resulting in significant reduction in production. A short period of dry weather of up to two months usually triggers flowering.
The avocado tree needs high relative humidity at flowering (70-80 per cent), then moderate levels during the fruit swelling stage. However, too much humidity encourages the proliferation of pests and diseases such as thrips, scales, cercospora spot, scab and anthracnose.
Avocado trees does well in deep sandy and loamy soils that are well-drained. Poorly drained soils are associated with the presence of the Phytophthora fungi, which causes root or stem end rot.
The optimum pH is 5 to 7. Soils with high organic content support faster growth of trees and production of many and bigger fruits.
Strong winds causes flower abortion hence reduction in production.
Due to the weight of the fruits and the fragile branches that carry them, strong wind easily breaks loaded branches. Avocados should be grown in areas with gentle wind. Wind breaker row with closely planted trees can be used to protect an orchard in windy places.
It is also important to ensure that your avocado trees get plenty of light. The trees should have at least 6 hours of full sunshine a day; avoid planting the trees in areas with too much shadow from buildings or other trees. However, it is noteworthy that intense radiation causes scorching of leaves and fruits.
Most of the avocado roots occur within the first 600mm soil depth, it is important that hard pans are not created during ploughing.
7 Tips to Orchard establishment (Orchard means a piece of enclosed land planted with fruit trees.)
- Land clearing & ploughing; Land should be free from bushes, weeds, other trees that competes for nutrients and water and may also attracts pests and diseases-causing organisms.
- Land layout & Spacing; there is range of views on planting density, which seems to come down to personal preferences. For a farmer who wishes to maximize on returns per acre, a spacing of 5 by 5 meters is economically viable.
- Hole making: Planting hole should be dug 2 feet wide, 2 feet long and 2 feet deep(2ft*2ft*2ft). A farmer should separate the top soil and the sub soil.
- Back filing: Top soil should first be backfilled into the holes. A farmer, who wishes to add manure before backfilling, should thoroughly mix the manure with the top soil to avoid damage to feeder roots.
- Seedlings Planting: During planting, due care should be taken while removing seedlings from the potting bags, to avoid roots disturbance and damage of the grafting union. It is advisable for a farmer who may not be able to afford drip irrigation systems to plant during the onset of long rainy season. Water the seedling after planting.
- Crop nutrients: Avocado plants requires adequate nutrition, especially Nitrogen, Phosphorous and Potassium in equal ratios when establishing an orchard.
- Irrigation systems: A farmer can either go for drip irrigation systems or manual watering e.g. using bucket/container.
Addition of fresh manure, especially poultry manure, could be dangerous for the young tree since the roots could be easily burned. Avocado trees should be planted to the same depth as they were in the planting bag.
Collar rot develops if the trees are planted too deep, while roots are burnt by the sun if the tree is planted too shallow. The trees should preferably be planted in a slightly raised position so that water cannot collect in the basin around the stem.