Avocado seedlings transplanting into the main field.
To make crop breeding operations and harvest easier, trees should be planted in a straight line. In addition to rectangular, square, and hexagonal layouts, there are other options available. The rectangular planting pattern is the primary method used in Kenya. This allows machinery to move freely between rows for cultivation, spraying, pruning, and harvesting. Furthermore, it enables the maximum penetration and utilization of sunlight.
A closed square planting approach is followed by a tree thinning operation due to congestion and costly tree removal. Plant spacing is dependent on elevation, soil fertility, cultivars, and climate. If soil fertility is high, maintenance inputs are limited and plants depend mainly on rain, the spacing is likely to be larger than normal. Overcrowding will lead to more pest and disease infestations, resulting in lower yields and lower incomes.
Depending on the above variables, it is recommended to plant trees that are 6 m x 7 m or 8 m x 10 m. Where yields per hectare are low in the early years, infill crops or sub-crops can compensate. Beans, maize, sunflowers, and system are just a few of the annual crops that can be grown. They are appropriate, but not always. It’s important to remember that young trees require a distance of at least two meters.
Preparation of planting holes.
- After layout and stake, digging of planting holes begins.
- During the dry season, the holes should be dug and the planting process should be completed by the start of the rainy season.
- To comfortably accommodate the seedlings, the holes should be dug large and deep enough, leaving enough space for soil to be filled on the sides and under the bale.
- Planting holes of 60cm square and 70cm are recommended. To ensure free drainage and uninterrupted root growth, compacted gravel layers or muddy outcrops must be broken up.
- Take soil samples when digging planting holes. To obtain accurate values, it is important to avoid mixing topsoil and subsoil and to take separate samples for analysis.
- When planting, it is important to separate topsoil and subsoil because they contain different nutrients and topsoil is more fertile.
- For best analytical results, take 10-12 topsoil samples (5-15 cm deep) from different locations in the field.
- Mix well and place approximately 1 kg of this representative mixture in a properly labeled shipping container.
- Fill a separate container with soil to a depth of 16cm and continue with this process.
Planting avocado seedlings.
1. Dig a planting hole that is 2 by 2 feet (0.61 m), both deep and wide. It is recommended to have a round hole.
2. Separate the topsoil and the subsoil from the hole. Lime is added in case the soil is acidic.
3. Set aside one debe of manure.
4. Mix the manure with the subsoil either in the hole or before filling it.
5. Add a handful of DAP fertilizer and mix it thoroughly with the manure and subsoil mixture.
6. Add the topsoil and mix it with the mixture in the hole.
7. Level the filled hole with the normal ground surface and add more mixture to raise half feet from the ground to avoid water logging.
8. Place a mark in the center of the hole.
9. Gently remove the seedling from the polythene bag, being careful not to disturb the soil that holds the roots together.
10. Make a hole in the center of the planting hole and plant the seedling.
11. Allow the soil to cover the seedling up to the point where the nursery media in the paper had reached to protect it from rotting.
12. If the weather is dry, make sure to water the plant thoroughly through drip irrigation for at least the first two weeks.
Photo source green gold series.
1) digging a hole and separating topsoil and subsoil; 2) mixing topsoil with Agricultural lime; 3) mixing topsoil with lime with mature; 5) filling the hole with the soil mature and lime mixture; 6) making a hole in the center; 7) placing the seedling in the hole; 8) cover the seedling with the mixture; 9) drip irrigation to water the seedling.
Field maintenance.
Pruning and training.
It is not necessary to prune avocado trees extensively when they are young. Trees should be allowed to grow naturally whenever possible. Be sure to cut off any suckers that appear below the graft or bud union. Training avocados should begin at an early age. It’s best to start the second growing season of terminal shoots and encourage lateral growth until the tree is properly shaped. Without early training, upright varieties grow very tall and fruit develops in the upper two-thirds of the tree, making harvesting difficult.
Early training will help limit tree height, and fruit will be produced closer to the ground and evenly throughout the tree. Avocado trees don’t need trimming or thinning. Before bloom or after fruit set is the best time to prune trees to keep them smaller. This way, the tree can naturally adjust its fruit load during the June drop. It is possible to prune a tree at any time of the year. It is better, however, to avoid pruning late in the season, as this may result in tender growth that is susceptible to frost damage.
What to do;
Sprinkle little by little and remove as little green wood as possible and some green leaves. Protect any exposed branches after pruning from sunburn by painting with a mixture of 50:50 white latex paint and water. Pruning is primarily done to increase the size, quality, and quantity of fruits in later years. Shortening branches touching the ground, pruning broken or diseased branches, and removing unwanted shoots within the canopy.
To prune properly after avocado transplanting, it is best to do so when the trees are dormant. This is also the best moment for the often-needed rejuvenation pruning aimed at bringing declining/neglected trees back to full productivity. To avoid fungal infestation, wounds made during pruning have to be treated with a suitable sealing compound. Additionally, exposed trunks and branches need to be whitewashed to protect against sunburn.
Types of pruning avocado tree.
- Light pruning.
- Medium pruning.
- Heavy pruning.
Both light and medium pruning is what is called plant maintenance as there not many branches are removed while heavy pruning is where after several years the tree is cut down totally about a meter from the ground and the tree comes back to production after two years at about 25% of the normal production and regain fully production after four years.
a). Light and medium pruning. b). Heavy avocado pruning
Weed control.
There are five approaches to weed control in orchards: mechanical cultivation, manual cultivation (hoeing/pulling), intercropping/cover crops, mulching, and herbicides. Mechanical cultivation should be used sparingly due to the potential damage to the root system and other negative effects. Manual cultivation is preferred for newly planted trees while intercropping with legumes can provide additional income for the farmer. Mulching is effective in reducing weed growth, controlling erosion, and improving soil structure. Herbicides can be used as a control measure, but they are not commonly used in Kenya’s avocado industry due to cost and potential damage to the foliage.
Fertilization.
To guarantee optimal growth, it is recommended to apply a total of 30 grams of actual nitrogen to each irrigated tree during the first year. The amount should be doubled every year until it reaches 480 grams by the fifth year, which will be sufficient. It is recommended to divide the entire fertilizer amount into two or three separate applications because avocados are sensitive to high salt concentrations.
Fertilizer requirements for avocado trees
| Age (years) | CAN (g) | DSP (g) | Murate of potash (g) | FYD (kg) |
| 1- 3 | 125 | 225 | 15 | |
| 4- 5 | 225 | 4450 | 15 | |
| 6 – 7 | 450 | 650 | 225 | 30 |
| 8- 9 | 650 | 650 | 450 | 30 |
| 10- 14 | 900 | 1000 | 635 | |
| 15+ | 1300 | 1200 | 650 |
Nitrogen-containing fertilizers should only be applied to the drip line areas around the trees when the soil is moist. It is crucial to note that nitrogen can penetrate the soil with moisture. When the soil is too acidic, phosphate-containing fertilizers may not be effectively absorbed. These fertilizers should be applied in such a way as to reach the root zone for optimal penetration. Before applying phosphorus-based fertilizers, it may be necessary to adjust the soil’s pH by adding calcium (lime) in some cases. Calcium-based fertilizers are generally the safest choice for most avocado-growing regions in Kenya due to the acidic nature of the soils. Phosphorus is a vital nutrient that aids in the growth and development of roots, especially in young trees. Potassium nutrition is more important for the yield and fruit quality of mature avocado trees than for young trees that do not yet bear fruit.
Irrigation system.
The irrigation of avocados is important to achieve maximum yields and fast maturity. The quality of avocado fruit can be improved and avocado trees can be greatly benefited by using the right irrigation methods.
Avocado irrigation in Kenya is done through drip irrigation, which is a popular method. The method involves using button drippers or pressure-compensated drip lines to direct water directly to the root zone of the avocado trees. For young avocado trees, this method is especially effective and allows for precise water distribution, ensuring that the shallow root system receives adequate water.
a) button drippers system. b) pressure-compensated drip lines system.
Micro sprinkler irrigation is another effective method for irrigating avocados. Low-volume sprinklers are employed in this method to apply water directly to the root zone. The sprinklers have a spray radius of up to 2.5 meters, which allows a uniform distribution of water in the root zone. Furthermore, micro sprinkler irrigation assists in cooling the plants and reducing heat stress.
Micro sprinkler irrigation system for an avocado tree.
It is crucial to aim for a water distribution efficiency of 80% when selecting an irrigation system for avocado trees. This will enhance the tree’s health and ultimately lead to higher yields and profits for the farmer.
Overall, avocado irrigation is essential for achieving higher yields, quick maturity, and consistent production. It helps to minimize plant stress, reduce flower and fruit drops, and improve the overall health of avocado trees.
Mulching.
Mulching is undertaken to conserve moisture and add organic matter to the soil. Mulching will therefore improve the water retention of soil and subsequently promote avocado growth. The most common mulch for avocados is well-dried grass that is pest-free. According to Pegg (2010), mulching should have a C:N ratio between 25:1 and 100:1.
Trimmings and prunings of avocados, chipped to a suitable size, have been very successful. Aged hardwoods like eucalyptus, pine bark that has been aged or composted, and stem grass thatch like Rhodes grass are also suitable. Care must be taken to compensate for any nitrogen depletion from mulches with a high C:N ratio (leaf analysis) while the sawdust is too compact and too low in N (severe negative N period). While natural avocado leaf drop is beneficial, woody mulch is more effective. Don’t remove the pruned branches, but chop them up and use them as mulch in the orchard.
Intercropping.
Avocado orchards may be intercropped with other crops such as beans, peas, kale, or cabbage during the first 3-5 years to get economic returns from the land before the trees start bearing or producing economic returns.
References.
1. https://www.google.com/search?client=ms-android-transsion&q=How+to+fertilize+avocado+tree+in+kenya+pdf&uds=H4sIAAAAAAAA_-OK5mIOSEkTUsvIL1coyVdISy0qyczJrEpVSCzLT05MyVcoKUpNVcjMU8hOzatMNBAq0vIgSqVCQUoaAOcbQAZdAAAA&sa=X&ictx=0&biw=360&bih=664&dpr=2&lei=aO7RZLjLDOHskdUP8bS74Ao.
2. https://www.agric.wa.gov.au/minor-fruits/propagating-jujubes?page=0%2C1#smartpaging_toc_p1_s2_h3.
3. Avocado Seedling Multiplication 2019 by Lusike Wasilwa, Grace Watani, Nasambu Okoko, Anthony Nyaga, Violet Kirigua and Joseph Njuguna.
4. AVOCADO GROWING IN KENYA JÜRGEN GRIESBACH
