Annual Report: CIRAD 2008

In the semi-arid regions of Brazil, farmers have few financial resources, which reduces their possibilities for purchasing inputs, especially fertilizers. Moreover, the high population growth in this region has increased pressure on natural resources, thus resulting in clearance of the native vegetation, ie caatinga . CIRAD and EMBRAPA researchers studied the impact of soil fertility management practices on the sustainability of production systems with the aim of developing intensification strategies that would make more effective use of farm resources. It was assumed that the analysis of biomass flows could facilitate the characterization of management practices and the development of sustainability indicators. These biomass flows, which are usually converted into mineral balances, have an impact on other farm resources that should also be estimated.

Identifying and describing biomass flows

This approach involves identifying areas of production and concentration of biomass, as well as biomass flows between these areas, such as biomass transfers, imports and exports. The analysed sample consisted of 14 farms with diversified production structures. For each farm, the different biomass areas and flows were described and quantified on the basis of the farmers’ monthly logs of their practices, GPS measurements of areas and biomass production on crop fields (seeds, straw, faeces) and semistructured interviews with farmers.

The main flows were converted into sustainability indicators on the basis of the descriptions of production systems. A simple model was then developed to analyse the sustainability of the studied systems. It simulates multiannual changes in production systems and indicators. Potential areas for improvement based on the simulations were discussed with the farmers.

A method for assessing farm sustainability

Each biomass flow involved a negative or positive balance concerning the farm’s resources, such as mineral, fodder, livestock or forest resources. The impacts of farmers’ decisions on a farm’s resources could be analysed after identifying these flows and converting them into balances.

The developed model was used to estimate long-term changes in these balances. It runs on a seasonal time step and simulates biomass production according to the type of year (good or bad) for four types of fodder areas—pastures sown with buffel grass (Cenchrus ciliaris), sorghum cropped for silage, Indian fig prickly pear (Opuntia ficusindica), which is harvested and fed to the livestock during the dry season, and caatinga vegetation. It also simulates changes in mineral reserves for each area, in livestock numbers, and in caatinga areas. Regional references were used to model these processes. Four types of decision regulate changes in these different balances: stockpiling fodder, clearing native vegetation, using the different fodder resources, and selling livestock. This simulator was validated with farmers who were not part of the survey network.

These indicators and this simulation model served as a basis for discussions with the Brazilian researchers. They highlighted the importance of continuing the research on management of caatinga vegetation by exploiting useful species. Discussions with farmers were focused on the impact of farming practices on the the sustainability of production systems.

Improving production system performance

Several levels of complexity between production systems were also identified, resulting in variable performances, from systems at the installation stage with little area and low biomass flows to long-standing diversified systems able to cope with climatic and economic risks.

Specific options were discussed and tested with each type of farmer. For dairy farmers, for instance, who are not very self-sufficient in terms of fodder production and do not make effective use of caatinga fodder resources, techniques aimed at selecting caatinga forest species were proposed.

Contact

Nadine Andrieu
Innovation and Development in Agriculture and the Agrifoods Sector (INNOVATION)
E-mail

Partners

• Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA, Brazil)

For further information

• Andrieu N., Piraux M., Tonneau J.P., 2007. Design of sustainability indicators of the production systems in Brazilian semi-arid area by the analysis of biomass flows. International Journal of Sustainable Development, 10 : 106-121.
• Andrieu N., Tonneau J.P., 2007. Gestion agroécologique de la caatinga pour les agriculteurs familiaux du Sertão : une alternative à la désertification ? Bois et forêts des tropiques, 293 : 9-21.