Page 102 - Soil Degradation, Conservation and Remediation

3.4 Control of Water Erosion 89

Fig. 3.12 Contour cropping (Photo courtesy of USDA-NRCS)

stones, lava or granite rock, decorative and colored stones, sand, crushed brick,
crushed graded recycled glass, landscape fabric sometimes referred to as geotex-
tiles, plastic mulch, and aluminized mulch.

3.4.5 Contour Cropping

Plowing and planting crop in the contour that is across the slope is called contour
cropping or contour farming (Fig. 3.12 ). Contours are arbitrary lines drawn perpen-
dicular to the direction of slope. So, contour farming is a cross-slope farming sys-
tem. Contours reduce velocity of runoff, give accumulated water more time to

infiltrate, and deposit detached soil particles along the contour lines. It retains sedi-
ments in the field. In contour farming, ridges and furrows are formed by tillage,

planting, and other farming operations to change the direction of runoff from
directly downslope to around the hillslope. Contour farming is most effective on
slopes between 2 and 10 %. Contour farming is not well suited to rolling topography
having a high degree of slope irregularity.
Several factors infl uence the effectiveness of contour farming to reduce soil ero-
sion. They are rainfall intensity, slope steepness, soil properties, ridge height, cover
and roughness, and the critical slope length. Cover, roughness, and ridge height can
be influenced by management. Spacing of contour lines is chosen on the basis of

slope, soil, rainfall, and crop type. Annual and perennial crops are planted in the
ridges or furrows of the contours. Contour farming can be combined with strip
cropping.