Agroforestry is the practice of growing trees and/or keeping livestock on the same field at the same time.
The trees could be grown purposely for timber production, shed, nutrients or medicine. Trees could be planted on purely agricultural land or crops could be introduced to forested lands.
There are a number of agroforestry practices currently in practice such as; Silvopasture (a combination of trees and pasture), silvorable farming (crops and trees), alley cropping (crops between rows of trees) and riparian buffers (trees, shrubs and grass along streams) among others.
Although agroforestry has been practiced by mankind for many decades, it has gained greater attention in recent times due to the multiple benefits derived from it.
Tree off-cuts generated during pruning and harvesting provide soil cover, mulch and organic manure to the soil which improves on the microbial activities of the living micro-organisms in the soils. These create burrows that lead to further organic matter decomposition, promote deep root development, enrich soil moisture, improve soil aeration and eventually soil fertility.
Tree branches and shoots provide timber, wood, construction materials, customary norms, herbal medicines, animal feeds (fodder), human food (fruits) which diversify man’s livelihood.
Trees act as wind breaks eventually protecting gardens and infrastructure from wind erosion and other damages.
Trees are a good source of natural environments with fresh scents and aroma, and beautified landscapes.
Trees provide shade for tender crops, animals, grass and human beings especially during the dry seasons and under excessive temperatures.
Some tree species fix nitrogen into the soil which eventually promotes soil fertility, provides plant nutrients cycling and yield increase.
Alley cropping and planting trees as hedges at the farm boundaries trap run-off as well as reduce soil erosion and nutrient loss.
Alley cropping improves crop and forage quality since it keeps them away from the heavy heat.
Some trees with tap root system increase soil water infiltration and movements.
Tree roots hold soil particles together hence increasing soil moisture as well as improving the arrangement of the soil and corresponding physical properties.
Silvopastoral farming increases the availability of organic manure from animal droppings for both crops and pastures.
Agro-forestry enhances farm income possibilities and insures them. Any losses incurred by the farmer in crop productivity could be compensated for by revenue from trees.
Alley cropping lowers crop visibility to the plant pests while providing alternative pest hosts and breaking their breeding cycle.
Trees with a growth-inhibiting effect against other crops (allelopathy), if incorporated into the agroforestry practice, could be very handy to prevent the development and accumulation of some weeds, pests and diseases.
Agro-forestry protects and maintains the ecosystems by improving habitat for wild life while encouraging plant growth.
Riparian forest buffers prevent river bank degradation and promote the water quality of streams or rivers.
Agro-forestry practiced on river banks reduces chances of degradation and eventually flooding since there is streamlined water flow.
Trees with deeper rooting systems could retrieve soil nutrients long lost through leaching and bring them to the soil surface for shallow roots to use.
With agro-forestry, there is reduced artificial fertiliser use since the organic matter is partly provided by the trees.
Agro-forestry promotes maximum utilisation of land and space available on the farm and is a potential source of sustainable rural economic growth and productivity.
In cases where poultry is raised under tree cover, varieties of grass, insects and micro-organisms present a more balanced and cheap diet than the conventional practices.
Rural problems associated with agricultural production, fuel shortages and environmental degradation can be mitigated.
Agro-forestry easily enables the reclamation of previous degraded and uncultivable land through accumulated nutrient reserves and soil physical properties from improved fallows.
Agro-forestry enables rural farmers to adapt and become more resilient to combat climate change vagaries by fully conserving soil, water and biodiversity while simultaneously increasing food production and restoring productive natural resources.
How to obtain maximum output from agro-forestry
The habits and performances of the different crops grown between tree rows (alley-cropping system) should be considered in regard to light, water and nutrients requirements.
The light requirements of crops can be enhanced by studying the east-west orientation of the sun so as to benefit from it.
Shoot and root pruning or thinning should be carried out to maintain the appropriate plant shoot and root density or cover for maximum nutrient sharing.
The recommended and appropriate plant population should be implemented with the help of technical personnel at the various levels of the community. For instance 5-6 m spacing between tree rows and 2.5-3 m between individual trees.
Fine leaved trees that permit maximum light penetration should also be encouraged as they maintain a transparent canopy for photosynthesis of the vegetation beneath.
Trees that produce growth inhibiting chemicals against other crops (allelopathy) should be keenly studied and promoted only with those that they complement with.
Tree or timber harvesting and pruning or thinning should only be encouraged and practiced during off season when there is limited crop growth activity to minimise damage to the crops by the falling trees or branches.
Water and nutrient use is maximised by incorporating tree species like Faidherbia albida that are deep tap-rooted to extract leached nutrients while leaving the shallow nutrients for crop use.
Tree species that shade off their leaves at the beginning of the dry season and develop them at the on-set of the rains saves water, increase soil cover, provide mulch and enhance crop productivity should be considered.
Trees should be grown in the direction across (at right angles to) the direction of the prevailing winds to reduce wind speed and maximise the effect of windbreaks.
Where silvopastoral farming is practiced, the plant grass growth around the young trees should be cleared to ensure maximum nutrient and light benefit to the trees.
In a pastureland, the introduction of young trees should be encouraged since it promotes maximum penetration of light. The introduction of forage or pastures in a forested land should observe rotational grazing so as to maximise pasture redevelopment.
The writer is a practicing agricultural engineer.