SCIENTISTS at the Zonal Research Centre at the College of Agricultural Engineering (CAE) in Coi-mbatore have developed a motorised machine for weed extraction in fields and orchards. The device claims to bring down the cost of weeding a hectare of cultivated land by 70 per cent from Rs 2,200 for manual weeding, down to Rs 600 with the motorised implement.

The machine, which resembles the front half of a bicycle with a motor rigged above the wheel, is driven between crop rows to uproot the weeds. The machine is suitable for weeding fields of crops like turmeric, tomato, tapioca, cotton, maize, soyabean, groundnut and pulses, as well as for orchards, coconut and areca nut plantations (Invention Intelligence, Vol 30, No 1).

Says R Karunanithi, head Of CAE who initiated work on the research project to develop the machine, "Weeds destroy about Rs 420 crore worth of crop annually in India, and weed control is one of the most expensive operations in crop production. About one-third of the cost of cultivation is spent on weeding alone when carried out manually."

Karunanithi advocates mechanical weeding over chemical weeding as weedicides are expensive and selective and are often harmful to humans and crops. Weedicide application also requires large quantities of water.

The CAE weeding machine is capable of weeding upto 0.05 ha of land per hour, or one acre in an 8 hour day. It works at a depth of 4-5 cm and consurnes I litre of kerosene per hour of field operations.

Says Karunanithi's associate A Taiuddin, "The weeding machine is operated by a 1.1 kilowatt (1.5 horse-power) engine that requires petrol to start and kerosene to run. The engine power is transmitted to a 450 nim diameter wheel through sprockets and chains in 2 steps so as to have the walking speed of 2.5 km per hour."

A replaceable sweep blade is fixed at the back of the machine. Sweep blades of width ranging from 150 to 250 min can be fitted depending on the row-to- row spacing required. A 150 mm diameter iron wheel with pegs had been pro vided in front of the sweep blade to disturb the soil and for maintaining the depth of the blade.

The development of the weeding machine was financed by the Tamil Nadu State Council for Science and Technology. The machine is priced at Rs 9,500, and efforts are on to bring down its cost.