Sustainable Ag. Intensification
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By 2050, FAO estimates that the global population will have reached 9.1 billion people. To feed this population, the world will need to produce significantly more food: 3 billion more tons of cereal and over 200 million more tons of meat products per year. At the same time, however, we face a lack of arable land upon which farmers can expand their production, as well as increasing competition for natural resources and decreasing soil fertility.

All of these challenges mean that increasing food production will require a global shift from extensive agricultural systems to sustainable intensification (SI) agricultural systems. Such systems include agroforestry, intercropping and crop diversification, and the use of mineral and organic fertilizers to help renew soil fertility and increase agricultural yields.

A new article in Food Security examines the potential for sustainable intensification of maize production in Africa south of the Sahara. The article looks at 17 multi-year, multi-site peer-reviewed studies that have assessed the performance of SI interventions for smallholder farmers, focusing on maize-farming systems. Interventions analyzed include the use of green manure, the use of rotational cropping with legumes, the use of agroforestry, and the use of conservation agriculture.

The article looks at these interventions’ impact on both “provisioning services” (maize grain and protein yields) and “supporting services” (biomass production per unit of rainfall and efficiency of nitrogen fertilizers); by combining both factors, the study can thus analyze the impact of SI interventions on both agricultural production and agricultural sustainability. After compiling information from each of the studies on the services of interest, the authors then utilized radar charts to visualize and compare the services provided by multiple SI interventions.

Overall, the article finds that there are both benefits and trade-offs to many SI interventions, and that the response of various factors to these interventions is highly variable and context-specific.

The application of nitrogen fertilizer (N-fertilizer) was found to increase grain yields, protein yields, and vegetative biomass across most of the studies; the exception was in areas characterized by more sandy soils, such as those found in several study sites in Zimbabwe.  Diversification of maize systems with legumes led to even more efficient use of N-fertilizer and further increased grain yields. This was particularly true when the legumes used were longer-lived varieties that produced more vegetative ground cover and higher protein food products; the use of such varieties increased N-fertilizer efficiency, protein yields, and vegetative biomass. However, the article also notes that adding legumes into their crop rotation can reduce annual maize yields for smallholder farmers, since no maize will be produced during periods when legumes are being grown; thus, rotational cropping may be more appealing and effective for farmers with slightly larger landholdings since they will be able to stagger different crops in different fields and ensure production of both maize and legumes in a given year.

The use of agroforestry was found to have the largest impact of all of the interventions on maize grain yields, producing 2000 to 5000 kg ha−1 of grain relative to around 1000 kg ha when only maize is planted. However, agroforestry also requires substantial labor use, making it inefficient for many farmers. In addition, free-roaming livestock production is common in many areas in Africa south of the Sahara, posing another challenge for successful agroforestry, according to the article.

Conservation agriculture was found to have the most inconsistent impacts across the studies analyzed. While in some cases, the use of conservation tillage practices improved maize grain yields and vegetative biomass production, these effects did not hold true across the board. In addition, some studies found that in order for conservation tillage to be effective in the first few years of its adoption, large applications of N-fertilizer are needed; this can reduce the practice’s cost-effectiveness and feasibility for poor smallholders. The authors conclude that conservation agriculture must be tailored to local soil types, topography, and climate conditions, and must be paired with interventions to increase farmers’ access to inputs like N-fertilizer, in order to truly be effective. 

The article concludes with several ways forward for sustainable intensification programs in Africa south of the Sahara. Plant breeding efforts should focus on producing legume varieties that are long-lived and that produce both copious vegetation and high-protein food. In addition, increasing both household demand and market demand for legumes will incentivize more smallholder farmers to adopt rotational cropping; thus, efforts should be made to increase consumers’ and producers’ awareness of the nutrition and agricultural benefits of legumes.

In addition, SI intervention programs need to shift away from a “one-size-fits-all” approach to take a more site- and context-specific look at which interventions will be most effective and sustainable in the long term. The authors suggest that smallholder farmers will be better served if programs provide them with a range of SI techniques and then build farmers’ capacity to share their knowledge and work together to combine those techniques in a way that makes the most sense for their specific locale. This will require investment in long-term research and extension support services.

Finally, the article emphasizes the need for consistent policymaking in support of sustainable agriculture. For example, farm input subsidy programs in both Malawi and Zimbabwe have been found to focus almost exclusively on hybrid maize seed and maize fertilizer, to the exclusion of legume diversification and other SI initiatives. Incorporating sustainable intensification techniques into prioritized national programs will help encourage the wider use of such techniques in African agriculture.

By: Sara Gustafson, IFPRI

Photo credit:David Stanley