Pulling up plants of shallow, light groundnuts is easy compared to uprooting cassava tubers. Many times I have seen farmers, men and women, struggle to pull up the big, starchy tubers. This makes a stunning energy demand on people, not to mention the strain on their backs.

The number and size of tubers vary greatly among cassava varieties; a single tuber can be as long as one meter and weigh up to 8 kilograms. Under traditional practices, farmers harvest 5 to 20 tons per hectare. This can easily be doubled by applying good soil fertility management practices, as shown in the video Growing cassava on poor soils.

While boosting production is one thing, getting the tubers out of the ground is yet another. Cassava does not lend itself readily to mechanical harvesting because the tubers of a single plant can spread over more than one meter and grow up to 60 centimeters deep. While countries like Mexico, Brazil and Thailand have adapted machinery to harvest cassava grown in large-scale plantations, smallholder farmers require simple, affordable devices that can reduce their workload.

Cassava has a tricky characteristic. Although the tubers look sturdy, once they are damaged and the starch is exposed to air, it becomes dark and the value of the flour decreases.

When visiting farmers in Northwest Thailand, I was thrilled to see farmers using a simple device to raise the tubers by pulling at the cut stems left after topping. At the same time I thought: “Why have I never seen any farmer in Africa use something like this?�

The tool was introduced some 20 years ago and now most farmers in Khon Buri district use it. Thai farmers use a long, wooden stick and have a metal fork made by a local artisan. The fork is attached at 30 centimeters from the bottom of the stick. Farmers wedge the rough edges of the fork into the cassava stem and then lever the tool to pull up the roots.

As Mr. Amnart Traprasomrong explains: “Before, I pulled the roots by hand. I had to pull hard, spent much energy. So this tool was invented. Instead of hand pulling, we now use this tool to lever the roots. We can work twice as fast.  If hand pulling takes two days, using this tool will take only one day.�

Local innovations and appropriate technology take time to spread, simply by word of mouth, with no advertising or formal support for the new idea. A topic like this is perfect for a future video which can help spread innovations faster and to many more farmers, even to other countries and continents.

Acknowledgement: the University of Ghent, Belgium, sponsored our video “Growing cassava on poor soils�. CIAT sponsored my visit to Thailand to produce the video “Managing mealybugs in cassava�, during which I learned from farmers about this innovation.