B. Smolikowski et al., Influence of soil protection techniques on runoff, erosion and plant production on semi-arid hillsides of Cabo Verde, AGR ECO ENV, 87(1), 2001, pp. 67-80
A combination of human, climatic, geomorphological and pedological factors
has led to extensive degradation of the soils of the Cabo Verde Islands. To
survive in fragile conditions, the stabilisation of the farming systems an
d the maintenance of high and sustainable yields have become absolute prior
ities for farmers. The project described here is part of a programme of wat
er resource optimisation on the island of Santiago in a semi-arid mountaino
us area near Godim. The objective of this study was to evaluate the influen
ce of two conservation techniques (light mulching with maize (Zea mays L.)
haulms and hedging with bushes and grass) on runoff, erosion and phytomass
production under natural rainfall. The main data were collected on five run
off plots of 100 m(2) and 10 pairs of 4 m2 plots scattered over the hillslo
pe. Although, rainfall erosivity was higher than in Sahelian areas, runoff
occurred only for rainfall higher than 40 mm and intensities over 40 mm/h.
Soil losses reached 12 mm/year on bare plots, 48 min with traditional crops
, 3.1 mm, with hedges and less than 0.03 mm under mulching on 50% slopes. T
his study confirmed that mulching alone, or associated with the plantation
of hedges, reduces runoff and erosion on the steep slopes of the Cabo Verde
mountains. However, the ability to improve the use of the water resources
by grain-producing crops in semi-arid regions was questionable. Plant mater
ial for mulching was only available and efficient during the wet years. The
efficiency was therefore irregular and depended on the abundance of rainfa
ll, weed production and the degree of satisfaction of plant water and nutri
ent requirements at the critical moment when the crops are in flower. Hedge
s of Leucaena leucocephala (Lam.) De Wit or Cajanus cajan (L.) Huth (Congo
pea), without ditches or banks, planted on the flat and mulched could contr
ibute to the supply of fodder in the dry season as well as blocking rivulet
runoff and erosion in the Sahelian area. (C) 2001 Elsevier Science B.V. Al
l rights reserved.