Turning the tide on farm productivity in Africa: an agroforestry solution

Kate Langford

Promising results from fertilizer trees and conservation agriculture in Malawi and Zambia are encouraging for African maize yields.

A recent cross-site visit to share the successes of an agroforestry programme in Malawi with conservation agriculture practices in Zambia has scientists excited about a system of maize production that could transform the lives of millions of farmers.

"By combining the best of both systems, we believe it is possible to double or even triple maize yields without an increase in labour or the need to apply mineral fertilizers," says Dr Dennis Garrity, Director General of the World Agroforestry Centre.

"A comprehensive agroforestry-based conservation agriculture system such as this shows tremendous promise for addressing global challenges of food security and climate change."

For a long time, crop yields have remained stagnant in Africa, closely linked to declining soil fertility and degraded land. The addition of mineral fertilizers cannot be sustained in the long term, neither environmentally nor economically, and for this reason farmers in Malawi and Zambia are applying the benefits of fertilizer trees.

Over a ten year experiment in Malawi using fertilizer trees, such as Tephrosia vogelii and Gliricidia sepium, maize yields have averaged 3.7 tonnes per hectare compared to 1 tonne per hectare in plots without fertilizer trees or mineral fertilizer.

According to Dr Garrity, the strength of the Malawi maize-agroforestry system is the enormous increase in Nitrogen-rich organic matter going into the soil combined with the potential of the tree legumes to suppress weed growth and weed populations.

The Centre has calculated that if half a million farmers, each with 0.2 hectares, were to plant fertilizer trees, the amount of nitrogen biomass they would fix in a year would be equivalent to 200kg per hectare. To buy this amount of mineral fertilizer would cost around USD 5.8 million per year.

The weakness is that there is a generally a greater labour investment in establishing, maintaining, and pruning back the leaves and other biomass of the intercropped leguminous trees compared to conventional maize production.

In Zambia, farmers are improving soil condition by replacing hoe ridging with the digging of planting basins. This greatly reduces the labour needed for land preparation which means the crop can be established with the first planting rains, reaching its full yield potential with less weed growth. This technique also concentrates added nutrients directly at the maize roots.

The weakness of Zambian conservation farming is that when neither herbicides nor fertilizer trees are used, more labour is needed for hand-weeding later in the season and there is no additional nutrient cycling since the ‘fertilizer’ is only applied during planting.

However, research with Faidherbia albida in Zambia over several years shows mature trees can sustain maize yields of 4 tonnes per hectare. Unlike most tree species, Faidherbia remains leafless during the growing season so it does not compete with maize. The leaves regrow during the dry season (a phenomenon known as reverse phenology) and they maintain needed land cover.

Scientists from the World Agroforestry Centre are confident of developing a system that combines the best of what is being practiced in Malawi and Zambia to drastically improve the condition of soils while keeping labor requirements at a minimum.

"Not only will this increase maize yields and provide greater food security, the increased growth of trees will improve drought resilience and build Carbon sequestration, thereby contributing to climate change adaptation," says Dr Garrity.

Many of the Centre’s partners are keen to upscale such a system to eight to ten countries in Africa.

Dr Grace Malindi, who is Director of Extension in Malawi and manages an extension staff of 2,800 across the country, said she was extremely excited by what she saw in Zambia.

"If funding is available, there is potential to reach the entire farming population of the country by 2012; a total of 2.7 million farm households," Dr Malindi said.

According to Odd Arnesen from the Norwegian Embassy in Lusaka, which has supported conservation agriculture in Zambia since the programme began, this is indeed a turning point for Africa.

"With the right type of political thinking and institutional support, we can strive for at least two million farmers in Africa having access to this technology by 2012," Mr Arnesen said.

"It is extremely timely that in Ethiopia in April, African Union Ministers of Agriculture, Land and Livestock called for a scaling up of conservations agriculture and agroforestry, and the development of a climate change adaptation framework for African agriculture."

If the principles of agroforestry agriculture are to be applied to several countries in Africa through a massive up-scaling with real impact, everyone involved is aware that it will require the strengthening of training and a huge extension effort with serious donor commitment.

"The foundations are well established. We have sound science, strong partnerships with national research and extension systems and civil society organizations, and of course enthusiastic farming communities," Dr Garrity said.

Related publications

Pye-Smith C. World Agroforestry Centre (ICRAF), Nairobi (Kenya) 2008. Farming Trees, Banishing Hunger. How an agroforestry programme is helping smallholders in Malawi to grow more food and improve their livelihoods.

Sileshi, G.;Ajayi, O.C.;Akinnifesi, F.K.;Place, F. World Agroforestry Centre (ICRAF), Nairobi (Kenya) 2009. Green fertilizers can boost food security in Africa Nairobi.

Sileshi G, Akinnifesi FK, Ajayi OC, Place F. 2008. Meta-analysis of maize yield response to planted fallow and green manure legumes in sub-Saharan Africa. Plant and Soil 307:1–19.

Baudron, F.; Mwanza, H.M.; Triomphe, B.; Bwalya, M. World Agroforestry Centre (ICRAF), Nairobi (Kenya) 2007. Conservation agriculture in Zambia. - Nairobi, Kenya: African Conservation Tillage Network (ACT) Conservation Agriculture in Africa Series.

World Agroforestry Centre (ICRAF), Nairobi (Kenya) 2006. Defying the odds: Agroforestry helps African farmers meet food security goals.