A country plough cuts a trapizoidal furrow having 18cm top width and 5cm bottom width the depth of furriw is 8cm assume the average soil resistance to be 0.6kg/cm^2 calculate the pull exerted by bullocks if the plough chain forms an angle 30 degree with the horizontal
Answers
TILLAGE
Mechanical manipulation of soil to provide favourable condition for proper crop growth is called tillage. Soil tillage consists of breaking the compact surface of earth to a certain depth and to loosen the soil mass so as to enable the roots of the crops to penetrate and spread into the soil.
Objectives of Tillage
To prepare a desirable soil structure for a deep seed bed or a root bed suitable for different types of crops.( A granular structure is desirable to allow rapid infiltration and good retention of rainfall, to provide adequate air capacity and exchange with in the soil and to minimize resistance to root penetration. A good seed bed generally considered to imply finer particles and greater firmness in the vicinity of the seed)
To control weeds or to remove unwanted crop plants (thinning)
To manage plant residues. ( Mixing of trash is desirable from the tilth and decomposition stand points and retention of trash in the top layers reduce erosion)
To minimize soil erosion. (By following counter tillage, listing and proper placement of trash).
To establish specific surface configurations for planting, irrigating, drainage, harvesting operations etc.
To incorporate and mix fertilizers, pesticides, soil amendments etc. in to the soil
Classification of Tillage
Tillage operations for seed bed preparations are classified as: i) Primary tillage ii) Secondary tillage.
1. Primary tillage
The initial major soil working operation designed to plough the soil deeply to reduce soil strength, cover plant materials and rearrange aggregates is called primary tillage. The objectives of primary tillage are
a. To reduce soil strength
b. To rearrange aggregates
c. To cover plant materials and burry weeds
d. To kill insects and pests
The implements used for primary tillage are called as primary tillage implements. They include many animal drawn and tractor drawn implements. Animal drawn implements mostly include indigenous ploughs and mould-board ploughs. Tractor drawn implements include mould-board ploughs, disc ploughs, heavy duty disk harrows, subsoil ploughs, chisel ploughs and other similar implements.
2. Secondary tillage
Lighter and finer tillage operations performed in the soil after primary tillage to create proper soil tilth and. surface configuration for seeding and planting are called secondary tillage operations. Secondary tillage operations are generally done on the surface soil. They do not cause much soil inversion and shifting of soil from one place to other. They consume less power per unit area compared to primary tillage operations. The main objectives of secondary tillage are
To break the big clods and make the soil surface uniform and leveled as needed for a seed bed
To destroy grasses and weeds in the field.
To cut crop residues and mix them with top soil
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