Rice residues after harvest, near Sangrur, southeast Punjab, India (photo credit: Neil Palmer/CIAT).
There is a new report of mixed results about the viability of adopting ‘conservation agriculture’ to enhance soil health and sustain long-term crop productivity in the developing world, an approach advocated by many. The authors of the report work at five centres of the CGIAR and conducted this research under the CGIAR Systemwide Livestock Programme (SLP). The lead author is a scientist at the International Livestock Research Institute (ILRI). The following is based on the paper’s abstract.
One of the key principles of conservation agriculture is maintaining soil cover, often by depositing crop residues (the leaves, stems and stalks of crop plants after their grain or legumes have been harvested) on a crop field as mulch. Yet smallholder mixed crop-and-livestock farming systems across Africa and Asia face trade-offs among various options for crop residue use. This research assessed the trade-offs of using a proportion of a farm’s crop residues in contrasting settings on mixed crop-livestock farms. The paper draws from surveys in 12 villages and 9 countries across sub-Saharan Africa and South Asia. Sites were clustered into three groups along the combined population and livestock density gradients to assess current crop residue management practices and to explore potential challenges to adopting mulching practices in different circumstances.
Results show that in sites with high densities of human and livestock populations, although livestock face high potential pressure on resources on an area basis, biomass production tends to be substantial, with enough residues to cover demands for both livestock feed and soil mulch. In sites where population and livestock densities are at medium levels, biomass is scarce and pressure on land and feed are high, increasing pressure to use crop residues for livestock feed, and increasing the opportunity costs of using the residues for mulch. Where population and livestock densities are low, communal feed and fuel resources typically reduce pressure on crop residues on an area basis, but biomass production is also low and farmers in such sites rely largely on crop residues to get their livestock through the long dry seasons, indicating that there are substantial opportunity costs to using crop residues as mulch for croplands rather than feed for animals.
Despite its potential benefit for smallholder farmers across the density gradient, therefore, the introduction of mulching practices based on conservation agriculture appears potentially easier in sites where biomass production is sufficiently high to fulfil demands for both feed and fuel. In sites with relatively high feed and fuel pressure, any introduction of conservation agriculture needs complementary research and development efforts to increase biomass production and/or develop alternative sources of biomass to alleviate the opportunity costs of using some crop residues as mulch rather than feed.
Read the whole paper (note there is restricted access): Conservation agriculture in mixed crop-livestock systems: Scoping crop residue trade-offs in sub-Saharan Africa and South Asia, written by Diego Valbuena (ILRI and SLP), Olaf Erenstein (CIMMYT), Sabine Homann-Kee Tui (ICRISAT), Tahirou Abdoulaye (IITA), Lieven Claessens (CIP, ICRISAT and Wageningen University), Alan J. Duncan (ILRI), Bruno Gérard (SLP and CIMMYT), Mariana C Rufino (ILRI), Nils Teufel (ILRI), André van Rooyen (ICRISAT), Mark T van Wijk (ILRI and Wageningen University) and published online as a corrected proof in Field Crops Research on 17 March 2012.