What Influences the Design of the System and the Choice of Trees?
The first step in establishing an agroforestry system is to define its purpose. These goals will influence the system adopted and the types of trees grown. If the intention is to provide food for home use, fruit trees are often favored, while for livestock feed, Calliandra or Sesbania hedges may be preferred. For income generation, timber trees such as Grevillea robusta are frequently chosen. For boundary marking, Euphorbia could be a good choice.
For ecological benefits like windbreaking and microclimate regulation, larger trees are planted on the boundary and mixed with medium and short-height trees to intercept wind at different levels. For bee forage, flowering and sweet-smelling trees are preferable. The purpose of growing trees greatly influences the choice of trees, their distribution, and management practices. For instance, trees grown for firewood are often heavily pruned or pollarded.
Size of the Land and Spacing
Farmers with small land areas may only be able to grow small trees such as Prunus Africana, whereas those with larger areas can grow bigger trees like Albizia coriaria. The spacing will be smaller on steeply sloping land than on gently sloping land, with shrubs performing better on steep slopes than tall trees.
Topography of the Land
In swamped or water-logged valleys, water-loving trees should be planted alongside crops like yams that do not drain the water. Steep slopes or hills with shallow soils favor shallow-rooted trees, and digging deep planting holes is not always possible. It is advisable to start with pioneer trees that tolerate shallow soils and gradually introduce deep-rooted trees as the soil depth increases through controlled erosion. This procedure may also be applied to flat land with shallow soils, although bigger tree species may be grown in such areas. In sandy soil valleys without waterlogging, deep-rooted trees should be established to prevent toppling due to shallow soils. On flat land with deep soils, most trees can grow and should be integrated to form different canopy heights.
Weather Conditions
Weather conditions must be considered to avoid competition for water. In areas with heavy rainfall that causes erosion, agroforestry trees with large canopies should be grown. In regions with limited rainfall and prolonged dry periods, trees like Neem and Grevillea robusta that shed leaves should be considered, while trees with reverse phenology should be avoided.
Soil Type and Natural Vegetation
Some pioneer trees, such as Prunus africana and Milletia dura, can grow in poor soils, while others like avocado and papaya prefer deep, fertile soils.
Where to Establish the Agroforestry System
Many smallholder farmers do not have access to large land areas to grow trees. However, optimizing spacing through proper site analysis can help find space for planting trees, such as establishing hedgerows along boundaries, riverbanks, and swamps, and in pastureland for animals. Intercropping systems require a good understanding of interactions between different crops. Good land use planning makes it possible to establish woodlots or fruit orchards even on smallholder farms.
Site Analysis
Ensuring the right spacing between trees and planting them in the most suitable locations requires a well-informed analysis of the farm. During this analysis, facilitators should walk the farm with the farmer and their family members to discuss which tree species to integrate based on their usefulness. Understanding the whole system is crucial: feel the soil, observe the current canopy, see spaces between plants, note the location of animal structures, and consider the slope of the land and existing crops. Drawing a map of the farm can be helpful. The map should be adjusted until the most suitable design is achieved, considering space, soil, interactions with other crops, impact on animals, pests, and diseases affecting the trees. The map should be maintained and updated regularly.
An ESFROMA Site Analysis tool for Agroforestry can be downloaded from www.organicfflg.org.
How to Prepare the Hole for Tree Planting
For soft soils, dig a round hole 20 cm in diameter and 30 cm deep. For hard soils, dig a rectangular hole 50 cm wide and 50 cm deep to allow roots to penetrate through the corners. For planting seeds, dig a small rectangular hole 20 cm wide and 30 cm deep. For planting a cutting with a bud (e.g., for hedges), dig 30 cm deep. Separate the topsoil (10 cm depth) from the subsoil and leave the holes for seven days to three months, depending on the tree species. The size of the hole should be three times larger than the root ball of the tree seedling.
How to Prepare the Soil for Planting
Mix topsoil and subsoil in a 2:1 ratio, making a fine mix by crushing crumbs. Combine the soil mixture with well-composted manure or compost in a 1:2 ratio. Fill the hole completely with the mixture and leave it for one to three days.
How to Plant the Tree
Time the planting to occur one to seven days before rain. Water the hole with a slow flow of 20 liters of water in the morning or evening. Open a hole depending on the size of the seedling and species. If the seedling is in a black polyethylene bag, cut off the bottom if closed, being careful not to damage the roots. Place the seedling gently in the hole up to half the stem’s depth. Plant seeds 5-10 cm deep, and cuttings 30 cm apart and 10 cm deep. Cover the hole with soil and flatten it. Water the seedling until the soil is saturated.
How to Care for Young Agroforestry Trees
Like other farm plants, trees should be frequently monitored by the farmer and FFLG members. Good agronomic practices to ensure healthy tree growth include compost manure application, watering, and other maintenance activities.