The introduction to agroforestry in the previous article explained the broad principles of this agriculture system.

• In this article, we look at the value of the systems with regard to the improvement of land and biodiversity;
• food and nutritional security;
• income and livelihood improvement;
• ecosystem services and climate change mitigation; and
• gender aspects.

Land and biodiversity improvement

The main challenge facing smallholder farmers in Kenya is low soil productivity caused by continuous cropping over time with no or low addition of inorganic fertilisers.

Research has proven agroforestry to be a cheap way to improve soil fertility by means of reducing soil erosion and
land degradation and thereby increasing crop yields. In western and central Kenya, technologies like improved short-duration fallows, green manure biomass transfer, hedgerows and intercropping with fertiliser trees substantially improved soils.

Benefits of short-duration fallows accelerate the process of soil rehabilitation, enables double maize yields and provide firewood for households. Improved fallow species combined with a micro-dose of inorganic fertiliser led to
an even bigger maize yield compared to non-fertilised maize farms. Tithonia diversifolia or tree marigold, a plant native to Mexico and Central America, is used as a green fertiliser biomass. When combined with rock phosphate on soils that are low in phosphorus, it proved to be an effective way of restoring soil fertility and resulted in an increase in yields of maize, tomatoes, kale and French beans.

Striga, also known as witchweed, is a parasitic plant that attacks cereals and severely stunts them, especially on nitrogen deficient soils. When striga is removed, less soil erosion occurs. In western Kenya, improved fallows remarkably declined infestation by the weed. Agroforestry effectively controls loss of soil through surface run-off, especially on steep slopes, and aids the rehabilitation of degraded rangelands.

Agroforestry can conserve tree genetic resources. The system provides landowners of private, communal or public land with the opportunity to introduce new tree species in an area. Trees can grow in different locations including boundaries, terraces or intercropped in food crops, pasture lands, river areas and hills, among others. This provides small-scale farmers with the opportunity to use different niches for specific tree production. In some instances, land productivity improvement by agroforestry sometimes involves trade-offs that may impact negatively on the farmers if not properly planned and executed, for example, where exotic tree species are grown excessively, they might replace indigenous species that leads to low tree species diversity on landscapes. This occurs mostly in the humid highlands, where Eucalyptus (blue gums) and Grevillea robusta, (silk oak) have replaced many indigenous species as the most common tree species on farms in western and central Kenya.

Food and nutritional security

Agroforestry contributes to food and nutritional security through:

1. the direct provision of tree foods such as fruits and leafy vegetables and by supporting staple crop production;
2. by providing rich and nutritious fodder for livestock;
3. by providing energy for proper processing and cooking of food such as charcoal and firewood; and
4. by supporting various ecosystem services such as pollination that are essential for the production of some food plants.

By planting indigenous and exotic fruit and nut trees, farmers have access to fresh fruit, a major source of vitamins and minerals, throughout the year. Mango, orange, avocado, tamarind and baobab trees, as well as macadamia and cashew nuts, and many other fruit and nut trees, grow in the humid highlands as well as the arid and semiarid lands (ASALs). Fodder trees, when fed to dairy cattle, significantly increase milk yields, enabling households to have more milk for use and sale of surplus milk. Milk is an important source of proteins, especially for children. For example, one kilogramme of dry matter equivalent of the twigs of Calliandra calothyrsus, a leguminous tree or shrub native to Mexico and Central America, increase milk production by 0,6 kg to 0,8 kg per day per cow and the butterfat content is also slightly higher when cattle were fed with this tree fodder. Besides fodder, this species is also used for reforestation, firewood and nitrogen fixation, but may be invasive in some regions.

Sale of tree products provide smallholders with additional income, which allows them to purchase food types not produced on the farm, thereby improving household food diversity and better nutrition. Better access to cooking fuel also gives households a wider variety of foods they can cook and eat, including foods with better nutritional profiles that need more heat to cook, such as legumes.

Income and livelihood

improvement Incomes are usually seasonal in relation to the farming cycle and farmers are vulnerable and exposed when they only rely on their small farms for food and livelihoods. By providing profitable market products, farmers can raise their income levels or obtain products they would otherwise have to buy. Agroforestry systems provide opportunities for getting involved in various enterprises like tree nurseries, timber production and sale, as well as the sale of fruit, fodder and fuel wood, among others. The trees act as a rural ‘insurance system’, ‘savings account’ and ‘safetynet’ for poor, highly vulnerable smallholder farming families.

Ecosystem services and climate change mitigation

Climate change is a major threat to a huge proportion of the farming populations dependent on agriculture in
developing countries, including Kenya. Net revenue from crops is expected to fall by 90% by 2100 as a result of climate change, while smallholder farmers do not have the means or knowledge to adapt.

Agroforestry can buffer farmers against climate extremes, while at the same time providing other services that support local production such as protection of soil, springs, streams and watersheds, conservation of animal and plant biodiversity, and carbon sequestration and storage. Carbon credits may provide another source of income for farmers. Since agriculture in Kenya is mostly rain-fed, farmers are very vulnerable to any variability in rainfall and temperature patterns. Agroforestry can help reduce farmers’ vulnerability.

In semi-arid areas it was found that trees can buffer understory crops against extremes of temperature by reducing incident radiation. Another study in the area reported higher soil moisture retention where alien species Gliricidia sepium and Calliandra calothyrsus trees were intercropped with maize. This can extend the growing season of maize, and possibly other crops, during periods of drought. Both trees are also useful for reforestation, fodder, firewood and nitrogen fixation.

Gender aspects

Successful agroforestry depends on the participation of women, who benefit from access to tree products such as fuel wood, herbs, fodder and vegetables on their farms. Thus, they save money and time, which can be invested in productive activities that can improve incomes and livelihoods. Although women do most of the work on the farms and manage natural resources, they are often disadvantaged due to socio-cultural and economic constraints. Sometimes women are not allowed to plant and manage trees because they do not own the land. They do not have
money, so they do not have access to new technology, seeds or seedlings.

However, in some communities, widows or women whose husbands are working away from home may decide on the land use, including tree planting. Women manage more tree species on farmlands than men since they primarily
try to meet subsistence needs over and above commercial goals. They are also as actively involved in planting fodder shrubs and woodlots, as well as improvement of soil fertility, even though female-headed households grow only about half the number of trees that men do.

Source references:

Agroforestry in Kenya (2024) Tracextech. https://tracextech.com/agroforestry-in-kenya/

Tengnäs B. (1994.) Agroforestry extension manual for Kenya. Nairobi: International Centre for Research in Agroforestry. Agroforestry extension manual for Kenya. World Agroforestry Centre UDC: 634.0.26:374.6(676.2) ISBN 92 9059 116 1. https://apps.worldagroforestry.org/Units/Library/Books/Book%2006/html/publisher.htm?n=1

Wanjira, E.O., Muriuki, J. (2020) Review of the Status of Agroforestry Practices in Kenya. Background study for preparation of Kenya National Agroforestry Strategy (2020 – 2030) World Agroforestry Centre https://www.ctc-n.org/system/files/dossier/3b/A%20review%20of%20agroforestry%20status%20of%20Kenya.pdf