14. Erosion in andean hillside farming.
Hohenheim Tropical Agricultural Series 1; Verlag J. Margraf, P.O.B. 105, 6992 Weikersheim, FRG; ISBN 3-8236-1211-5; 1992, 219 pp., price DM 35,00/USD 27.00
The investigations reported here were carried out to provide some basic information on characteristics of soil erosion processess in the Andean zone of Colombia. The effect of cultural practices in cassava cultivation systems on the process of soil erosion was investigated.
The research reported here aims to collect basic information on the characteristics of erosion processes in a defined area of the Andean zone of Colombia. Furthermore, conventional and improved cassava cropping systems adapted to local smallholder conditions were to be tested to obtain knowledge based on the influence of management practices on erosion processes. Erosion trials were established on slopes with a gradient of 7-20% at two locations in southern Colombia.
As expected, the greatest soil losses were found in the clean tilled fallow system. However, at the beginning of the growing period the greatest soil losses were measured where rill erosion was predominant.
This was especially evident in plots with cassava on ridges down the slope where greater soil losses were recorded during the first months after planting than in the plots with clean tilled fallow. These results show that soil conservation measures must be directed especially towards the reduction of surface runoff during the first months after planting.
In this context those cropping systems were the most efficient which reduced the velocity and the quantity of runoff by physical barriers.
This is especially evident for the contour ridges and to a limited extent also for the contour grass strips. Also, a high initial percentage of ground cover reduced effectively the surface runoff and prevented rill erosion.
Based on these site characteristics, a tolerable amount of a yearly soil loss of 1-5 t/ha-1 was calculated.
Under the test conditions the cropping systems with sole cropped cassava and cassava planted between contour strips of grass produced relatively high yields.
The results suggest that management practices such as planting on contour ridges or contour strips markedly reduce soil loss while producing optimum cassava yields.
This book is well worth the attention of those working with soil and water conservation in mountain areas. All chapters are well, documented and the conclusions drawn are verified by the text, graphs and tables.
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Erosion and desertification control
Review, USA, soil and water conservation, tillage systems
UNGER, P.W. and T.M. MCCALLA
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