Paddy Straw choppers and spreaders, Biomass Management for Fodder & Energy | Biomass Management for Fodder & Energy - Agricultural Engineering PDF Download

Introduction

Although number of uses of paddy straw are available like as cattle feed, as packaging material for horticultural crops, as bedding for ruminants and in thermal power generation but still all these uses account up to 20 % of paddy straw and rest is considered as waste and is burnt in the fields. About 60-70 % farmers opt for burning of paddy straw. This practice needs to be discouraged because burning of paddy residue is not only a source of atmospheric pollution but it also leads to loss rich organic matter. The only solution to resolve this problem of paddy straw management is incorporation of paddy straw in soil. If the straw to be incorporated into the soil a straw chopper and spreader may be used. Chopper chops the straw and the spreader spreads the same. The chopped and spreaded stubbles can be buried easily in the soil with minimum tillage efforts by the use of traditional tillage implements like disc harrow and rotavator.

7.2. Classification

Straw choppers can be classified by size into small, medium and large. The small size chopper is mainly adapted for chopping dry straw or silage on small scale farms. The large chopper also called a silage chopper is mainly used for silage on cattle farms.
The medium chopper is normally suited to cutting dry straw and silage, so it is called a straw silage chopper. Choppers can be divided into cylinder or flywheel types, according to the mode of cutting. Large and medium size choppers are generally flywheel types, to facilitate throwing silage but the majority of small choppers are cylinder type. Large and medium choppers are usually equipped with road wheels for easy movement while small size choppers are normally stationary.

7.2.1. Cylinder choppers

There are many types of cylinder chopper. The machine consists primarily of mechanisms for feeding, chopping, and throwing, with a transmission, a clutch and a frame. The main parts of the feed mechanism are a chain conveyor, pressing rollers, and upper and lower feed rollers. For the upper feed roller, springs are used for pressure, with a cross-groove shaft coupled with a compact structure for driving. The chopping and throwing mechanism is in one unit, which consists of a main shaft, a blade rotor, rotating blades, a throwing vane and stationary blades. Gear teeth are 13, 22, 65 or 56. By changing the gear used, the speed can be adjusted to obtain various cutting lengths.

7.2.2. Flywheel choppers

Flywheel chopper has a feed chain, upper and lower feed rollers, a stationary lower blade, a cutter and a throwing fan. The straw is fed via the feed chain into the feed rollers, pressed and moved forward by them, then cut into pieces by the combination of upper and lower blades, and it is finally blown by the fan to the storage site or silo.

7.3. Tractor-operated straw chopping machine

Tractor-operated straw chopping machine harvests the straw left after combining and chops it into pieces for spreading in the field in a single operation. The chopped and spreaded stubbles can be buried easily in the soil with minimum tillage efforts by the use of traditional tillage implements like disc harrow and rotavator. The two types of straw chopper cum spreader are: (1) flail type and (2) cutter bar type.

7.3.1. Flail type rice-straw chopper-cum-spreader

PAU, Ludhiana centre, in co-operation with a manufacturer has developed a tractor-operated straw chopper-cum-spreader. It harvests the straw left after combining and chops it into pieces for spreading in the field in a single operation. The machine consisted of a rotary shaft mounted with four rows of blades named as flail for harvesting and chopping the paddy straw. There were 14 number of flails on each row.

The average field capacity (ha/h) of mounted type straw chopper cum spreader at forward speed of 2.00 km/h was 0.33 ha/h. At forward speed of 2.50 km/h, the field capacity was 0.39 ha/h and at 3.00 km/h the field capacity was 0.46 ha/h. The field efficiency at forward speed of 2.00, 2.50 and 3.00 km/h was 86.84 %, 82.10 % and 80.70 % respectively. Field efficiency decreased with increase in forward speed as at higher forward speed, the machinery is difficult to handle in the field.

7.3.2. Cutter bar type rice-straw chopper-cum-spreader

The cutter bar type machine has reel speed of 70 rpm and reel diameter of 457 mm.
A reel is attached in the front to feed the straw to the cutter. The cut stubbles are conveyed to the chopping cylinder with the help of feeding cylinder attached between the cutter bar and chopping mechanism. Field capacity of flail type machine varies from 0.35 to 0.38 ha/h at speed of operation of 2.72 km/h. The cutter bar type rice straw chopper cum spreader gave field capacity from 0.35 to 0.37 ha/h at speed of operation from 2.65 to 2.69 km/h. After chopping, the straw was incorporated by two passes of disc harrow.

After chopping, the straw was incorporated by two passes of disc harrow. Then the field was irrigated and subsequent sowing of wheat was done with no-till drill. The machine is commercially available. Feed rate of the straw chopper cum spreader was dependent upon the crop density, forward speed, width of cut and stalk cut length.