Mechanized threshing of foodgrains for sustainable agriculture in NE
- Part 2 -

Yumnam Jekender, RK Tiwari & SK Chauhan *

Few crop specific energy efficient power threshers developed in country are contributing key role for delivering quality produce with minimum permissible losses. Few crop threshers reviewed are prominent successful proven designs which are commercially available in India are given below.

Power Operated Maize Dehusker-cum-Sheller : The machine has a threshing cylinder of 495 x 1460 mm size with peg type drum. It uses centrifugal type blower. There are three round sieves with 12.5 mm size hole in upper sieve, 7 mm in middle sieve and 3 mm in lower sieve.

Concave clearance is kept about 50 mm and opening size of concave is 5.1 x 5.1 mm. Cylinder speed is kept at 13.7 m/s. The output of machine varies from 1.7 to 2.1 t/h at moisture content of 11.8 to 24.8%. The cleaning and threshing efficiency range 94-99% and 96-98%, respectively. The overall grain losses are from 0.65 to 1.42%.

The percent recovery of grain with the machine is 97% as compared to 78.4% in manual threshing. The unit price of equipment is about Rs. 40,000. The cost of operation of this machine is Rs. 500/t against Rs. 1500/t by traditional method. There is a saving of about 60-70% in cost of operation and about 90% in labour as compared to traditional method of dehusking and threshing.

Whole Crop Maize Thresher : A whole crop maize thresher has been developed for shelling of maize cob and simultaneously converting stalk to chaff. The thresher is designed for 5.5 kW power with spike tooth cylinder having 6-7 bolts per row on periphery. Concave is prepared by placing 8 mm square bars at a spacing of 18 mm.

Threshing speed is kept at 620 rpm. The output capacity of whole crop maize thresher is 210 kg/h. The output of grain is observed as 640 kg/h with chaff size of 18 to 52 mm. This chaff is fed to animals and 85% material is consumed in comparison to the whole stalk. The unit price of the machine is Rs. 70,000/-. Moreover, significant saving of Rs. 2000-2100/ha in labour was for detachment of cobs and transportation of crop from field to home.

Power operated thresher for CoriandrumStavium L : The axial flow multi-crop thresher has been developed for hilly region and it has been was evaluated for threshing of Coriandrum Stavium L variety by GBPUAT Centre of AICRP on FIM. The thresher is evaluated with two combinations i.e MS cylinder having MS pegs and PVC cylinder having composite pegs. The cylinder peripheral speed of 6 m/s and cylinder concave clearance of 15 mm give the best results for PVC cylinder with composite pegs.

The threshing efficiency, cleaning efficiency, percentage of broken seed, sieve loss and cylinder loss for threshing of coriandrum crop are 99.80, 91.29, 0.7, 2.07 and 0.21%, respectively. However, for MS cylinder with MS pegs (conventional) the optimum combination is 4.5 m/s cylinder peripheral speed and 19 mm cylinder concave clearance. The threshing efficiency, cleaning efficiency, percentage of broken seed, sieve loss and cylinder loss are 99.67, 88.10, 2.49, 1.91 and 0.29%, respectively. Therefore, PVC cylinder with composite pegs rotated at peripheral speed of 6 m/s and cylinder concave clearance of 15 mm can be used for threshing of coriander crop.

Tractor or electric motor operated multi-crop thresher for seed spices : The traditional practice of threshing of seed spices is either by beating on drums or on wooden logs or treading under tractor wheels on mud floors. It requires lots of labour and lot of dust and stone come in during the threshing process and are to be removed manually by hand sieves or cleaning machine in factories reducing the quality of seed spices.

Therefore, a tractor/electric motor operated thresher has been developed at MPUAT, Udaipur in collaboration with M/s Makewell Industries, Unjha (Gujarat) and evaluated for threshing of cumin and coriander crops. The drive to power transmission is given by telescoping shaft connected to PTO of tractor. An electric motor of 5.6 kW is mounted on frame so wherever electricity is available, thresher can be used with electric power. The output capacity of thresher is 240-260 kg/h. The unit price of thresher is Rs 70,000.

Multi-millet thresher: Threshing millets is done manually which results into lots of labour and time engagement. The multi-millet thresher was developed to facilitate timely threshing of the crop and to achieve higher output with better quality. It is also suitable for cleaning and grading of millets seeds. Threshing capacity of the equipment is 80-150 kg/h. About one million farmers of India, especially in the tribal areas are likely to get benefit of the equipment by saving about 30 man-h/ha of operation time.

Light weight powered paddy thresher cum cleaner : A light weight paddy thresher cum cleaner was developed by NEH, Barapani centre. It consisted of main frame, threshing unit, blower, sieving unit and power transmission unit including single phase 0.75 kW electric motor. Threshing unit consisted of cylinder fitted with wire loops.

The separation of paddy grain from the straw was achieved due to combing action of the wire loops fitted on the threshing cylinder. The test results indicated that the threshing efficiency, grain output capacity and losses due to shattering of the machine were 99.2%, 143 kg/h and 2%, respectively.

Axial flow multi-crop thresher for hilly region : The prototype of axial flow multi-crop thresher operated by single phase 1.5 kW motor/power tiller engine was designed and developed at GBPUAT, Pantnagar for threshing of cowpea, soybean, black gram, paddy and wheat crops. The output capacity of machine was 80-100 kg/h. Total losses varied 2.45-2.78%.
Tubular Maize Sheller : It is a manual operated sheller suitable for shelling maize from dehusked cobs. Shelling is done by holding the sheller in left hand and gradually inserting the cob into the sheller by right hand with little forward and backward twist. The capacity of sheller is 15-20 kg/h. It costs Rs. 60/- and cost of operation is Rs. 75/kg.

Pedal Operated Thresher : It is suitable for threshing rice. It consists of wire-loop type threshing cylinder operated by foot pedal or motor. It saves 20% labour and 40% operating time as compared to conventional method of hand beating on a wooden platform. It costs Rs. 5,500/- and its cost of operation is Rs. 28/q. With 200 h of annual use (4 q/h grain) or 150 tonnes of grain threshing, a thresher needed peg replacement once in three years. Therefore, with life span of 12 years, thresher pegs need to be replaced 3 times.

In India there are 150 million power threshers utilized (being 60% mechanization in threshing operation) in threshing 175 million tonnes crop produce consuming average power consumption of 15 kWh/ton of grain. Thus mechanized threshing of crop consumes total power of 1440 million kWh in the country.

In the agricultural sector standardization and improvement of critical component viz. threshing cylinder will bring down the total power consumption to 2/3 in mechanized threshing. The requirement of power threshers (mechanized threshing 100%) based on statewise foodgrains production has been estimated in table 1.

It also indicates requirement of statewise threshing units if food grains are threshed 25% by power threshers and 75% food grains threshing by pedal operated threshers. The economics of crop threshers include average output capacity of pedal operated and power threshers as 70-100 kg/h and 200-250 kg/h, respectively and cost of units included are Rs 8000/ and Rs 70, 000/ for each units. The power threshers need for 100 % mechanized threshing will be 537060 numbers and if mechanized 25% then 134258 numbers of power threshers will be required in north eastern states (8) nos.

Similarly if foodgrains total quantities are threshed by pedal operated threshers then 1074120 units will be needed. For partial threshing (75% foodgrains quantity) is performed by pedal operated threshers then total 805592 numbers will be required in north eastern states (08) nos) . In Manipur for mechanized threshing of foodgrains, 26188 power threshers or 52376 pedal operated threshers will be required costing Rs 183.31 crore for power threshers or 41.9 crore for pedal operated threshers.

But if power threshers are used for threshing 25 % food grains then 45.82 crore will be needed to procure 134258 units excluding freight charges. Similarly if 75% foodgrains threshing is performed by pedal operated threshers then total 39282 units will be required costing Rs 31.42 excluding freight charges in Manipur.

Concluded ....