LPM 121: Fodder Production and Grassland Management (1+1)

MECHANICAL MEASURES

• Mechanical measures are supplemented with agronomical measures when the latter, alone is not sufficient. Some of the mechanical measures are
  • Contour bunding
  • Graded bunding
  • Bread base terrace
  • Bench terracing
  • Trenching
  • Vegetative barriers
  • Grassed waterways and
  • Gully control.
• Contour bunding
  • The contour bunds are formed at all lines of the greatest slope and this ensures uniform water depth and distribution throughout its length and enables better possible cultivation than any other type of bund.
  • As the bunds are at regular intervals, they intercept the run off from attaining erosive velocity and causing erosion. Contour bunds are adopted in areas with rainfall of less than 1500 mm and the slope of upto 6%.
• Graded bunding
  • This is recommended where the rain water is not readily absorbed either due to high rainfall or low intake of the soil. The graded bunds are designed for conveying the peak rate of the inter bunded run off at non scouring and no silting velocity.
• Broad base terrace
  • This is a combination of ridge and channel built across the slope on a controlled grade and has a wide base and low height of ridge. Suitable for deep black soils.
• Bench terracing
  • Usually practiced on slopes ranging from 16 to 33%. Bench terracing consists of principally transforming relatively steep land into a series of level strips or platforms across the slope of the land. It reduces the slope length and consequently erosion.
• Trenching
  • Contour trenches are made in non - agricultural land for providing adequate moisture conditions in order to raise tree and grass species. Size of the trench varies with slope, rainfall and depth of soil available.
  • Trenches are formed at an interval of 60m. The trenches are half refilled diagonally with excavated material and remaining half of the soil forms the spoil bank.
• Vegetative barriers
  • These are closely spaced plantation, usually a few rows of grasses or shrubs, grown along contours. Act as a barrier, to check the velocity of overland flow entrapment of silt load behind them. Eg. Khus (Vettiveria zelanica)
• Grassed waterways
  • Grassed waterways are drainage channels developed either by shaping the existing drainage ways or constructed separately to agricultural lands.
  • Used to handle run off discharge from graded bunds, broad base terraces, bench terraces etc. Suitable perennial grass, deep rooted and spreading type such as Panicum repens, Brachiaria mutica, Cynodon plectostachyus, Cynodon dactylon and Paspalum notatum may be established for the stability of the waterways.
• Gully control
  • Gullies are controlled by diverting run off by adoption of agronomical measures and stabilizing the gully sides and bed by establishing vegetation and reducing the gradient of the channel to maintain velocities below erosive level by temporary and permanent structures such as check dams, drop spillways and chutes.