Restoring the Soil - Canadian Foodgrains Bank

Decision Tree Guide37or the gm/cc systems they would most likely apply will keep the soil covered duringalmost all of the annual rainy season or seasons, go to #12. If the soil is at lessthan a 35% slope and will be well-covered during the rainy season, go to #12. Ifneither of these conditions applies, go to #11.11. Contour hedgerows. To prevent or reduce water erosion, many farmers aroundthe world are using contour hedgerows. This is a subject that could fill a book. Iwill mention just a few points that are very important and controversial amongsome practioners. First of all, ground cover is far more important than physicalbarriers in preventing water erosion, whether the barriers are contour hedgerows,rock walls, ditches, or whatever. If the gm/cc covers the ground well and the rainsare not too plentiful, farmers may not need hedgerows at all, even when the landis at a 40% slope. The ranges mentioned in #10 are applicable to most situations.Second, trees are not as effective as grass at holding the terrace face that maygradually build up (to as much as 75 cm), so probably the best over-all speciesfor hedgerows is Napier grass (Pennisetum purpureum), which is sometimes calledelephant grass. This species has a double function, as it holds the eroded soilvery well and provides a large amount of fodder for animals. If possible, use thevarieties of napier grass that do not have small hairs on the leaves, as they aremuch more palatable for animals and do not spread into farmers’ fields nearly asquickly. If grazing animals roam free during the dry season, the farmer who ownsthe hedgerows will receive no benefit from the napier grass as a good source offodder. A better choice in that case would be vetiver grass (Chrysopogon zizanioides).If the slope is less than 20% (so the terrace face will never get too high),the fields are at less than 1,000 m in elevation and the animals are under control,sugarcane is usually much more popular—but it will fall over if the terrace facegrows more than 25 centimetres (cm) in height.If farmers really want to plant non-grass crops in their hedgerows, such as pineapplesor fruit trees, a good option is to plant the grass and then space the othercrops along the grass barrier. This would also apply to trees planted to createdispersed shade. If farmers want to plant other grasses, such as lemon grass or ashorter-stature grass among vegetables, they can use these instead of napier grass,at least on parts of their land.Hedgerows should not be planted at less than 12 m apart, because farmers willusually reject any shorter spacing. The rows can be as far as 20 m apart on lessinclined slopes. If the hedgerows are too far apart to catch all the soil, do notmove them closer together than 12 m; instead, find a way to cover the soil betterwith a gm/cc. Hedgerows should be laid out by the farmers using A-frame levels.Hedgerows can be planted after the gm/ccs or at the same time, except whereerosion is excessive. In the latter case, the gm/ccs will not provide any increasein crop yields until the hedgerows are developed enough to prevent the gm/ccs’organic matter from being washed down the hill. Go to #12.