Secondary tillage
Secondary tillage is the shallow operation performed after the primary tillage. Secondary tillage implements are used for breaking clods and producing a loose, friable, smooth state. These implements are used with the following objectives.
• Breaking the furrow slice and working the soil to get the required tilth
• Destruction of weeds
• Stirring the soil and forming mulch
• Mixing the manures and fertilizers with soil
• Covering the seeds
1. Cultivators – These implements have number of tines for piercing the soil and breaking clods. Tines of 23–30 cm long are fixed to a heavy and sturdy, frame, mounted on wheels. These tines penetrate up to a depth of 20 cm in heavy models. Cultivators are used when the soil is ploughed deep with heavy mould board ploughs to break the big clods that are formed.
2. Harrows – They are smaller implements with many tines like cultivators. Used for breaking smaller clods left unbroken by cultivators and for producing a powdery seedbed. Tines are set closer (5-8 cm) and are smaller in size. They penetrate up to about 10 cm depth. There are different types of harrows in use.
A. Spike tooth harrow – Peg like steel tines of round, oval, square, triangular or rhomboid section are fixed on a rigid or flexible frames for use under different soil conditions. Rhomboid section offers straight cutting edge and it enters the soil properly and is better than others. In undulating lands the flexible types adjust themselves to the uneven surface. When the frame is of a zigzag type it called zigzag harrow.
B. Spring tine harrow – Instead of rigid tines strong steel springs shaped like the letter “C” are attached to the frame. Depth of penetration is adjusted with lever arrangements. Tines ride over rocky and other obstructions in the field and are not damaged since the spring tines recoil on obstruction. Due to vibration they pulverize clods better than rigid types.
C. Chain harrow – Number of stout steel links is connected together to spread over the soil like a mat. Links may have spike like projections. Since, they are flexible they adjust unevenness of the surface. These harrows are used for breaking clods and making the surface smooth and even. It can also be used for covering seeds after broadcasting.
D. Disc harrow – These harrows are made up of number of concave discs of 46–56 cm in diameter, fitted 15 cm apart on square axles. Two sets of discs are mounted on different axles. Discs cut through the soil and effectively pulverize clods. Small animal drawn harrows have six discs and power driven harrows have larger number.
E. Intercultivating harrow – Different types of harrows are used for intercultivation. Tines pass through the inter row spaces and effectively remove the weeds. The typical example of the intercultivating harrow is junior hoe.
Different attachments can be made in the tines of the junior hoe to make use of same harrow for different purposes.
Sweeps are blades that move horizontally under the soil and cut the shallow rooted weeds. There are two kinds of sweeps. The Central sweep attached to the central tines has horizontal wings extending on both the sides. The One side sweep has the wing on the right or left side. On the side tines, one-sided sweeps are fixed on the side away from the crop rows.
Hiller is a rhomboidal curved steel plate, shaped like the mould board, which is used for earthing up crop rows
Furrows have a double mould board one on either side, which splits the furrow slice and lays it on both sides equally. It is used with a central tine to open the furrow for sowing or to clean the furrow for irrigation.
Cultivator steel is a steel plate with sharp edge, which penetrates into the soil.
F. Blade Harrows – Different from conventional harrows in that there are no tines but they are fixed with horizontal blades, which enter into the soil and travel below the surface at a constant depth. These blades severe (cut) the surface layer from the soil below and leaves it in its original position with slight disturbance to the surface soil. These harrows cut the weeds, eradicate all weeds except those, which have under ground bulbs.
The Guntaka is the blade harrow used for primary tillage in ceded districts of Andhra Pradesh. It has a horizontal wooden beam of 15 cm diameter with a fixed handle, shaft pole and blade. The blade is fixed to the beam near the ends by two standards at 25 cm distance from beam. The blade is 1.0 m long, 7.5 cm broad and 1.25 cm thick, with a cutting edge in front. Big sized guntakas are called as bara guntakas (1.8 m long blade). Small guntakas with 15 to 33 cm long blades are called as danties that are used for inter cultivation in crops, spaced at 28–46 cm apart. Since they are small, five or six danties are attached to a common yoke and guided by three or four people. It covers 0.4 ha/day of eight hours.
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