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Ecosystem services in support of a greener revolution in Africa

Increased maize yields are helping to address food insecurity in Malawi (© Sieglinde Snapp)
Increased maize yields are helping to address food insecurity in Malawi
© Sieglinde Snapp

In Malawi, a subsidy programme for nitrogen fertiliser and improved maize seed has been heralded as a triumph for input intensification of rain-fed cereals. Over 1 million farmers have benefitted annually since 2006, with increased maize yields doing much to address food insecurity in the country. But the team, which undertook the field research on which Malawi's current programme, is based also recognised that crop diversity would be sacrificed by a system entirely based on maize. In response, two members of that team initiated a country-wide trial, to compare monocultural maize production with a more diversified system. In particular, the research team wanted to test the hypothesis that a diversified system would offer improved ecosystem services, and that these would contribute to enhanced food security among a broad base of Malawi's rural poor.

This trial developed into a five year programme of participatory research at sites in northern and southern Malawi, which was then expanded into a country-wide study involving around 1,000 farmers. Farmers assessed various systems against the standard improved maize seed/fertiliser package promoted through the subsidy programme. They also helped in developing the diversified model, to improve its applicability at household level. Ecosystem services that were monitored in the study were chosen for their relevance to smallholder farmer livelihoods. They included direct farm outputs such as grain and protein yield, and profitability, as well as supporting services such as plant cover, soil organic carbon, and fertiliser efficiency.

Promoting diversity

To introduce diversity, legumes were selected on several key criteria. They needed to be vigorous producers of nitrogen-enriched roots and leaves and should produce some edible grain, so as not to compromise household food security. They also needed to live longer than the four months typical of annuals. Mucuna pruriens and pigeon pea (Cajanus cajan) were two examples, which the research team termed 'semi-perennial' legumes (SP-legumes). Pigeon pea was already grown as a shrubby cereal intercrop in large areas of southern Malawi, where farmers appreciate its slow growth early in the season and deep rooting, which ensure minimal competition when grown as an intercrop with maize. It has high nitrogen-fixing capacity and produces modest amounts of grain on degraded sites.

Figure 1
Figure 1

Data from earlier evaluations showed that, under smallholder conditions, grain yields were improved and fertiliser use was profitable with the small amounts of fertiliser available under the subsidy programme. But, by improving biodiversity through the incorporation of legumes into the system, fertiliser use efficiency rose sharply, thus markedly reducing the level of subsidy needed to ensure national food security. Legume rotation systems could produce equivalent quantities of grain with half the amount of fertiliser, and on a more stable basis (yield variability reduced from 22 per cent to 13 per cent) compared to monoculture. Further studies found that when an increased fertiliser cost was taken into account - reflecting a global increase in fertiliser costs since 2008 - the diversified maize/legume system offered an even stronger value/cost ratio compared to monoculture.

In Figure 1, the profitability of three potential farming systems is compared. In the 'current system', the standard subsidised maize/fertiliser package is shown. If the farmer chooses to bring diversity in through rotating with a legume in the conventional manner, profit falls sharply. But, due to the combined effects of fertiliser use efficiency (the farmer gets more grain for less fertiliser) and an additional crop from the same piece of land in the same year, profit doubles under the improved legume system.

Consistent results

Farmer surveys indicated consistent technology rankings across experiments, despite the diversity of years, locations and participants involved. About half of participating farmers rated the SP-rotation system as first (41-56 per cent), around one-third chose an alternative groundnut/maize rotation and just 6-8 per cent chose monoculture maize. When technologies were assessed in terms of specific benefits and costs, nutritional benefits of legume diversification were particularly valued by female farmers. Overall, rankings of technologies remained generally consistent across the different sites and types of experimentation.

Farmers and outreach workers will need to become familiar with the new intercropping systems (© Sieglinde Snapp)
Farmers and outreach workers will need to become familiar with the new intercropping systems
© Sieglinde Snapp

This is the first evidence in Africa that crop diversification can be effective at a countrywide scale, and that shrubby, grain legumes could transform the economic viability of fertiliser subsidy policies, and support key ecosystem services from agriculture. Plant cover has increased from around four months to ten months, and fertiliser use efficiency by about 200 per cent. Some 8,000 farmers at the northern Malawi site are now adopting the improved legume system.

National plans

The Malawi Government has recently launched the Green Belt Initiative, a national programme in agricultural transformation; improved cropping systems, including use of legumes, are a major focus. There are, however, important implementation issues. Legume seed is expensive to multiply and is less profitable for seed producers than hybrid seeds such as many of the improved maize varieties. But Malawi has several emerging seed companies that are actively seeking a niche and could, with proper support and advice, enter this market.

Farmers and outreach workers will need to become familiar with the new systems, and there will be a need for ongoing enhancement and development. But the data from the farm trials have been carefully peer reviewed, and provide robust evidence that an improved legume/maize rotation offers a sustainable way for Malawi to maintain its impressive progress in food production, through a system which - unlike the current subsidy programme - will be less likely to cause reductions of expenditure in other key areas such as education and health.

Written by: SS Snapp, MJ Blackie, and GY Kanyama-Phiri

Date published: January 2012


Have your say

We also found deep rooted pigeon pea strip cropping improves... (posted by: RAVINDER RAJU AMBATI)

Organic, no-till farming, in permanent beds,doubles or tripl... (posted by: Ken)


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