Soil Erosion in Andean Cropping Systems The Impact of Rainfall Erosivity
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Beschreibung
Cassava, an important staple food and industrial crop of the low to medium-altitude trop-ics, is associated with soil exhaustion and degradation world-wide. Slow initial soil cover of the crop, in particular when grown without fertilizer, and the erosive nature of tropical rainstorms, combined with the increasing cultivation of marginal and steep lands are the principal factors leading first to the degradation of soils and then of rural livelihoods them-selves. They are indeed the loom on which the fabric of poverty is woven. Research focussing on the arrest or reversal of soil degradation has to take a long-term ap-proach since damage to agricultural lands from erosion is not normally detected in a couple of years and the loss in agricultural productivity is more of a gradually progressing than in-stantaneous nature. Yet, capturing the magnitude of change is necessary to quantify dam-age and justify investment in research to find viable solutions to the problems outlined above. A special effort has therefore been made to develop a sustained, long-term research programme on factors related to soil erosion and degradation in a mid-altitude location of the tropical Andes representative of vast extensions of agricultural lands in Central- and South America. Over a twelve-year time span (1986-1998), six individual doctoral research programmes, accompanied by numerous MSc programmes were planned and carried out in a sequential, co-ordinated way so as to explore causes and effects of soil erosion and devise conserva-tion practices in cassava-based cropping systems of an Andean mid-altitude tropical envi-ronment. The research reported in this doctoral dissertation, the last of those six, profits greatly from the large stock of scientific data previously generated and is thus able to pro-vide a medium-term perspective on degradation and productivity aspects as well as a solid, critical review of suitable conservation practices. Beyond this 12-year overview and syn-thesis, the last phase of the project focused on elucidating the role of rainfall erosivity in the context of soil erosion and conservation in this Andean environment from where no scientifically sound results were available until now. The research on rainfall erosivity im-plied a rigorous scientific approach to evasive and complicated to measure parameters such as raindrop size and a reassessment of the rain drop energy-rainfall intensity relationship. These and other highly demanding tasks were fulfilled with precision and perseverance. Based on the results, future researchers are now able to generate rainfall erosivity maps throughout the region based on rainfall quantity data thus providing an easy to generate and useful planning and decision support tool for agricultural development in the region.
What is left behind by this effort which went well beyond the twelve-year project phase is not only a wealth of scientific information on factors driving soil erosion and degradation in mid-altitude tropical Andean hillsides. Beyond science, and by gradually involving more and more stakeholders in the design of this research, planning tools and many practical so-lutions and approaches to conservation have emerged and have been taken up by local in-stitutions, NGO’s and even schools and farmers groups for whom this research was con-ducted. We are most grateful to Deutsche Forschungsgemeinschaft who provided the seed money to get this programme started, and to the Bundesministerium für wirtschaftliche Zusam-menarbeit und Entwicklung (BMZ) who had the vision and the determination to support this research over the necessary length of time to make it relevant and useful to those for whom it was conducted.
Autor*in
Kai Sonder
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Andean Cropping Systems Impact of Rainfall Rainfall Erosivity Soil Erosion