Crop residues are natural resources with
tremendous value to farmers. These residues are used as animal feed,
composting, thatching for rural homes and fuel for domestic and industrial use.
About 25% of nitrogen, 25% phosphorus, 50% of sulphur and 75% of potassium
uptake by cereal crops are retained in residues, making them valuable sources
of nutrients. However, a large portion of the residues, about 140 Mt, is burned
in field primarily to clear the field from straw and stubble after the harvest
of the crop. Each tonne of straw (rice or wheat) on
burning releases 3 kg particulate matter, 60 kg CO, 1,460 kg CO2,
199 kg ash and 2 kg SO2. About 32-76% of the straw weight and 27-73% nitrogen are lost due to burning. The problem is serious in irrigated
agriculture, particularly in the mechanized rice-wheat system. The main reasons
for burning crop residues in field include lack of labour, high cost in
removing the residues and use of combines in rice-wheat cropping system
especially in the Indo-Gangetic plains (IGP). Currently residue from nine crops, rice, wheat, maize, millet,
sugarcane, cotton, rapeseed, mustard and groundnut are subjected to burning. Crop
residue management may include developing systems to plant into residue, baling
and removal for use as animal feed or for industry.
Machinery
for Crop Residue Management
Straw reaper combine is tractor mounted and tractor power take off
shaft operated. It consists of cutter bar reel, feeding auger and bruising
cylinder like a traditional thresher. Straw and stubble left by the combine
harvester is collected by straw combine and delivered to the cylinder concave
section, where it is cut into small pieces and passed through the concave. The
reciprocating cutter bar is utilized for reaping the standing stubbles and the
portion of the straw left uncut by the combine harvester. The remained straw
passed through the concave is aspirated by anin-built blower and fed into a
trolley on back side covered by a wire net. Recovering of the left grains from
the straw, a sieve system is provided beneath the concave.Straw combines are
used to recover the wheat straw after combine operation with tractor having 35
hp or above. It capacity is 600 kg/h.
Straw
combine harvester
Tractor mounted flail type chopper cum spreader
The tractor operated
straw copping machine harvest the straw left in the field after the combining
and chops in to pieces for spreading in the field in a single operation. The
machine consists of rotary shaft mounted with blades /flails to harvest the
straw and knives for chopping. The capacity of machine is 4 ha/day and can be
operated by a 30 kW tractor. The average
height of stubbles was after cut was 30 mm. Traditional seed drill was found
satisfactory after incorporating the chopped straw by disking and planking
twice. The straw
after cutting by the flails, pass on to the chopping mechanism. The chopping
mechanism chops the cut straw to 50 mm size and spreads it in the field
uniformly. The cutting unit has 38 flails mounted in three rows. The chopping
mechanism has 300 mm diameter cylinder with six rows of serrated knives and
four counter rows each having 22 knives fixed at the bottom. This machine is
used for chopping of paddy straw with tractor having
35 hp or above, which helps in easy incorporation of straw in the soil
in fewer operations by using traditional equipment. Since
the incorporation of rice straw checks environmental pollution problem
providing rich organic manure, there is great acceptability of the machine in
rice –wheat cultivation system.
Stubble shaver
The
machine consists of a rotary blade assembly, mainframe, fenders, platform,
gearbox and three point linkages. Rotary blade assembly consists of three
blades, which cut the stubbles and spreads the cut stubbles on ground uniformly
because of higher blade speed. The blades are swinging type and this recoil on
striking stone or a hard object. 35 hp
or above size tractor operated stubble shaver is a versatile machine for
cutting any crop residues such as wheat, paddy and grasses from the ground
level. The operation of this machine for cutting paddy stubble replaces two
disking operations, which saves time, energy and money.
Shrub master
It
is a tractor pto operated equipment. It consists of cutting blades (swinging
flails) joined to the bar, gear box for transmission of power at right angle,
universal joints with telescopic shaft to connect the tractor pto and gearbox,
adjustable side skids for controlling cutting height of shrubs or grass, safety
guard and hitching frame. The bar having cutting blades at the ends is mounted
on the gearbox shaft. The cutting process takes placed purely through impact
and flails need not be sharp-edged. The blades are made of medium carbon steel
or alloy steel and hardened. It is used for the clearance of shrubs, monsoon
growth in forests, fields, fairways, verges, helipads and general clearance of
grasses in fields with tractor having 25 hp or above.
Mowers and shredders
Mowers and shredders are available in two basic
types: rotary or flail. Power requirements for both are relatively high, but
they produce a more uniform residue cover. A balance is needed between standing
stubble and chopped residue on the surface. Too much chopping to create short
or no stubble leaves a matt of residue which may not flow around the ground
opener. Besides mowers,
shredders are another type of machines used for mulch management. They consist
of knifes, rotating vertically at high speed around a horizontal axle. Usually
they reduce the biomass to small pieces. The advantages include a fairly even
spreading of the mulch, the control of pests and diseases and the shredded
pieces do not interfere with the planting operation. However, the biggest disadvantage
of shredders is that the chopped residues decompose much more quickly which
means they would not last as long on the soil surface as non-chopped residues.
Another serious disadvantage is the high energy consumption. For this reason
shredders should only be considered in special cases for residue and cover crop
management. Rotary slashers suffer from the same disadvantage.
Chisel/ripper
It is tool for minimum or reduced tillage. It has rigid curved or straight
shank with relatively narrow shovel points. The standards are arranged on heavy
frames in two or three staggered rows to permit trash to pass between them
without choking. The depth of ploughing
may be shallow as desired or as deep 450 mm or more. As the soil is broken by
stirring, it is not inverted and pulverized to the extent that MB or disc
ploughs crush the soil. Hence the chisel plough is used for stubble mulch or
sub-surface tillage practice. It can used to loosen hard, dry soils before the
regular plough is used. It is also used to broking up hard layers of soil just
below regular ploughing depth. Equipment need proper soil moisture for working
otherwise result clogging with residue, poor weed control and lifting of
stones/clods on top surface.
Subsoiler
Subsoiler ploughs are heavier than chisel plough,since they are used
to penetrate the soil depths of from 500 900 mm. Tractors of 60-85 hp are
required to pull single standard subsoiler through a hard soil at a depth of
900 mm. One standard is generally used for the deeper depth, but two or more
can be used for sallower operations. Subsoilers are commercially available in
both trailing and mounted units. For conservation agriculture subsoilers should
work under crop residues (have cutting disks), not lift clods to the soil surface
requiring subsequent tillage (shanks bent to the side), be only considered as
exceptional repair tool. It can be used in dry soil only and water infiltration
will not improve a lot when used improperly
Rotovator
Rotavator is suitable for preparing seedbed in a
single pass both in dry and wetland conditions. It is also suitable for
incorporating straw and green manure in the field. It consists of a steel
frame, a rotary shaft on which, blades are mounted, power transmission system, and
gearbox. Rotary motion of the PTO is transmitted to the shaft carrying the
blades through gearbox and transmission system. A good seedbed and
pulverization of the soil is achieved in a single pass of the rotovator. The
size of rotavators vary from 1.2 to 2.2 m. The field capacity of equipment is
0.36 – 0.44 ha/h. Residue left after operation of
plough and chisel is minimum 10% and it is maximum 50-70 with one cultivator
operation.
