In favor of using the “brush cutter” weeder in its various forms for mechanization is that it is widely available and relatively inexpensive.  It represents a first step towards mechanization for many small-holder farmers.  It is faster than a manual weeder, and avoids a push and pull motion that many weeders require for thorough weed removal.

In the USA a simple brush cutter with “string trimmer” can be purchased for about 150 USD for the version where the motor is attached directly to the cutter.  The backpack versions are of higher quality and cost approximately 300 USD and up.

The brush cutter has its challenges, but we believe it can be adapted for use as an effective SRI Weeder.  Here are some of the challenges we see:

The high RPM of the rotor makes the machine difficult to control and this forces the user to expend considerable energy guiding the weeder down the rows to avoiding damaging the rice plants.  Slowing the rotor speed would require a new gearbox.   We have not found a commercially available part/gear box to accomplish this.   Although the brush cutter can be used/adapted for multiple rows, control of the weeder remains difficult, and as the rotor/paddles must then be made much larger to go over the rice plants when doing two or more rows.  For With the multi row weeders, the larger rotors/paddles further increasing the tip speed of the rotor.

We know that Japanese versions of a single row covered weeder, that adds a single blade in a cover/sled, are is commercially available that adds a single blade in a cover/sled. The sled can be plastic or metal. This adaptation uses the commonly available “head” that holds “string” for grass and weed cutting.  We have attached plans for two versions of a single blade version that we are working on.  The added cutting blade will need to be modified to get the best possible weed removal and least damage to the plants.  We will test these in the near future at a farm testing site that has just become available to us.

This covered version has the advantage of covering the blade to a certain extent, taking some of the weight off the farmer, as well as providing some stability and tracking for the weeder.  We are looking forward to doing our construction and testing.

Thanks go to Supachai Pitiwu and the Weekend Farmers Network in Thailand for all the considerable testing and videos they have produced on this weeder:

Brush cutter, Backpack version:


Another advantage of this tool is that it can also be adapted to harvesting with an inexpensive conversion.  The safety of this use is unknown?


Japanese equipment site, (in Japanese):

Picture of plastic version

Picture of metal version

Prices without motor, in yen, 18,000    $160 USD

Prices with motor, in yen, 59,400           $530 USD

Less expensive versions can be purchased from Chinese Manufacturers.