60
4.2.3 Contour Ridges
Contour ridges consist of bunds or ridges, constructed along the contour line at an
interval of 5–20 m. A 1–2 m strip upstream of the ridge is allocated for cultivation,
and the rest constitutes the catchment. The height of the ridges varies according to
the slope and the expected depth of the runoff water retained behind it (Fig. 6 ). The
bunds may be strengthened by stones. This is a simple technique which can be
implemented by farmers. Bunds can be formed manually, with animal-driven equip-
ment, or with tractors fitted with suitable implements. Ridges may be constructed
on a wide range of slopes from 1 to 50 %. Contour ridges are important for support-
ing the regeneration of forage crops, grasses and trees on mild to steep slopes in the
step. In the semiarid tropics, they are used for growing sorghum, millet, cowpea and
beans. The system is sometimes combined with other techniques (such as the zai
system) or with in situ water conservation techniques (such as tied-ridge system) in
the semiarid tropics (Oweis et al. 2001 ; Mugabe 2004 ; Adgo et al. 2013 ).
Contour ridges are used in row crops in areas with 350–700 mm of annual rain-
fall and require even topography. The use of contour ridges in Jordanian and Syrian
deserts (annual rainfall ~150 mm) successfully raised fodder shrubs and cereal
crops. Furrows are dug on a contour and ridges formed immediately on the lower
side. The ridges are spaced 1–2 m apart and are usually 15–20 cm high. This forms
Fig. 5 Semi-circular bunds for bushes and trees (Sources: Oweis and Hachum 2009 , ICARDA;
http://www.actionagainsthunger.org))
A. Yazar and A. Ali