tailieunhanh - Water harvesting and soil moisture retention - chapter 7,8

Soil moisture retention In this second part soil moisture retention techniques to be applied in the cultivated area are described. A distinction is also made here between systems which follow the contour lines of a slope and those which are independent of contour lines. | Part II Soil moisture retention In this second part soil moisture retention techniques to be applied in the cultivated area are described. A distinction is also made here between systems which follow the contour lines of a slope and those which are independent of contour lines. Chapter 7 deals with contour systems to improve infiltration. Chapters 8 and 9 describe water conservation measures which are not necessarily contour-bound. 7 Contour systems to improve infiltration Contour farming is a term used to include ploughing furrowing and planting along the contours of a hill side. The objective of contour farming is to increase infiltration into the soil along the contours and to conserve soil moisture there. Contour farming may reduce runoff and soil erosion by as much as 50 . The first step in contour farming is to determine a contour guide line. One method for marking out contour lines the water tube-level is described in Appendix 3. Several other techniques are described in Agrodok Field surveying . All subsequent water conservation measures are related to the contour guide lines. Hedges shrubs or stones may be used to mark these lines. In small fields or on even slopes one guide line may be sufficient. This line should lie about halfway up the slope. On irregular slopes or in large fields more guide lines are necessary. In this case the various contour lines should be evenly distributed over the slope. Contour ploughing Contour ploughing ensures that rainfall and runoff water are spread evenly over a field by making furrows parallel to the contours. 62 Water harvesting and soil moisture retention Conditions Contour ploughing may be done on slopes with a gradient of less than 10 . On steeper slopes it is better to combine contour ploughing with other measures such as terracing or strip cropping. Contour ploughing is practical on fields with an even slope. On very irregular slopes it is too time-consuming to follow the contours when ploughing. Strip .