Crop residue mulching in tropical and semi-tropical countries: An evaluation of residue availability and other technological implications

Crop residue mulching (CRM) can be defined as a technology whereby at the time of crop emergence at least 30% of the soil surface is covered by organic residue of the previous crop. The present study proposes CRM as the most adequate term for the technology in view of the substantial controversy and confusion surrounding existing terms, particularly conservation tillage. CRM is a dual-purpose technology that combines conservation and productivity effects. Its conservation potential hinges on the presence of the crop residues as mulch. This mulch provides a protective layer to the soil surface that is extremely effective in halting soil erosion and also amends the soil ecology. Its productivity potential is twofold. First, the mulch tends to stabilise, and occasionally even enhance, crop yield. Second, it implies factor substitution and input use efficiency alterations. The paper presents the residue balance as an analytical tool to assess the current availability of residues-both in terms of current residue production and current residue destinations. Residue destinations typically include extraction, burning in situ, incorporation, weathering and retention as mulch. CRM has profound implications for crop management. First, CRM implies a set of necessary practices so as to ensure the retention of sufficient residues as mulch. Second, CRM may imply complementary adaptations in order to be able to grow a crop and/or maintain productivity levels. Therefore, CRM is not a simple add-on technology, but instead a complete package of cultural practices. The actual potential of the CRM technology depends on a comprehensive assessment of the socio-economic implications of the implied changes. This potential is site-specific and will diverge between the private and social viewpoint. CRM therefore is a promising dual-purpose technology-but no panacea for soil conservation in (semi-)tropical countries. (C) 2002 Elsevier Science B.V. All rights reserved.