FAO - Cross-Slope Barriers
Cross-slope barriers are measures on sloping lands in the form of earth or soil bunds, stone lines, and / or vegetative strips for reducing runoff velocity and soil loss, thereby contributing to soil, water and nutrient conservation. This is achieved by reducing steepness and / or length of slope. Terraces are not usually constructed per se, but rather develop gradually behind earth bunds, vegetative strips (usually grass) or stone barriers, due to soil movement from the upper to the lower part of the terrace. Erosion between the barriers helps to achieve the levelling of the terrace bed. While cross-slope barriers are primarily intended to reduce soil erosion, they also enable / ease cultivation between the barriers, which are usually sited along contours. However, in high rainfall areas they may be graded at 0.5 – 2.0% across the slope to allow safe discharge of excess surface water along the barriers to reach watercourses. Some common technologies used by smallholder farmers include contour bunds, fanya juu and fanya chini terraces, stone lines and vegetative barriers. Bench terraces can be the eventual result – though in some circumstances may be constructed through excavation and shaping.
To ensure sustained fertility of the land it is necessary to employ soil fertility management measures such as composting, green manures, cover crop, etc. (see group on Integrated Soil Fertility Management).