2.1.2. Plough-till (conventional tillage, CT)
The plough-till (CT) system is based on mechanical soil
manipulation of the entire field and involves mouldboard ploughing
followed by one or two harrowing. Plough-till embraces soil
cultivation based on ploughing or soil inversion, secondary
cultivation using discs and, tertiary working by cultivators and
harrows. These tools are often drawn by animals or tractors or by
other mechanically powered devices. Ploughing removes the
vegetation cover and exposes the soil to rainfall, wind and overland
flow. However, the technique gives a weed free seedbed, incorporate
fertilizer and improve soil conditions. The mechanical soil disturbance involved increases the risk of erosion. Mechanized conventional tillage encourages splash and sheet erosion as it leaves the soil
surface bare, under heavy tropical storm occurrences (Shetto, 1999).
Conventional flat cultivation systems are commonly practiced in
Eastern and Southern Africa. In this practice, the soils are cut,
inverted and pulverized, burying most of the crop residues
underneath, leaving a clean fine seedbed. Under the impact of
raindrops, the soils may cap or crust. Land degradation sets in and
this starts with the reduction in vegetative cover, exposing the soil
surface to accelerated erosion and leading to reduction in soil
organic matter and nutrient content (IFAD, 1992).
The effects of tillage method on soil properties and soil erosion
varies depending on soil properties. For example, where the soil
has favourable structure with high proportion of water-stable
aggregates, and is permeable, mechanical soil disturbance is likely
to increase risk of soil erosion. On the other hand, where the soil
has a smooth crusted surface and compacted subsoil horizon,
massive non-porous unstable structure, carefully judge, timely
mechanical tillage is likely to decrease the risk of soil erosion, at
least temporarily
2.1.2. Plough-till (conventional tillage, CT)
The plough-till (CT) system is based on mechanical soil
manipulation of the entire field and involves mouldboard ploughing
followed by one or two harrowing. Plough-till embraces soil
cultivation based on ploughing or soil inversion, secondary
cultivation using discs and, tertiary working by cultivators and
harrows. These tools are often drawn by animals or tractors or by
other mechanically powered devices. Ploughing removes the
vegetation cover and exposes the soil to rainfall, wind and overland
flow. However, the technique gives a weed free seedbed, incorporate
fertilizer and improve soil conditions. The mechanical soil disturbance involved increases the risk of erosion. Mechanized conventional tillage encourages splash and sheet erosion as it leaves the soil
surface bare, under heavy tropical storm occurrences (Shetto, 1999).
Conventional flat cultivation systems are commonly practiced in
Eastern and Southern Africa. In this practice, the soils are cut,
inverted and pulverized, burying most of the crop residues
underneath, leaving a clean fine seedbed. Under the impact of
raindrops, the soils may cap or crust. Land degradation sets in and
this starts with the reduction in vegetative cover, exposing the soil
surface to accelerated erosion and leading to reduction in soil
organic matter and nutrient content (IFAD, 1992).
The effects of tillage method on soil properties and soil erosion
varies depending on soil properties. For example, where the soil
has favourable structure with high proportion of water-stable
aggregates, and is permeable, mechanical soil disturbance is likely
to increase risk of soil erosion. On the other hand, where the soil
has a smooth crusted surface and compacted subsoil horizon,
massive non-porous unstable structure, carefully judge, timely
mechanical tillage is likely to decrease the risk of soil erosion, at
least temporarily
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