Tripura’s IFS officer Prasada Rao has developed a low-cost movable afforestation method called ‘Treebanks’ to increase the green cover in national highways without having to invest heavily in plant guards.

“Every time we plant a tree, the forest department spends close to Rs 2,000 to install a plant guard around it to prevent any man-made or animal-made damages,” he says.

“While it is a necessary expenditure, it can be avoided with an alternative, and public money can be saved. We can plant more trees with the saved money,” he adds.

In 2018, he initiated a pilot project along National Highway 44 and planted 15 species on a 5 km stretch of road based on the topography.

Treebanks are like nurseries, but they raise trees with a minimum height of 12 feet and collar girth of around 20 cm inside a plant container over a span of two years.

As part of his experiment, Rao studied the mahogany tree with a height of 15 feet and collar girth of 22 cm that can withstand strong wind pressure.

He measured the taproot, which had a depth of about 45 cm from the surface of the soil and its majority of fibrous roots were spread within the radius of 25 cm horizontally.

Using these measurements, Rao designed a polybag in which trees of this stature can be developed that allow the root system to grow both vertically and horizontally.

Next, he filled the bag with soil, manure, urea, single super phosphate, and potash and transplanted a one-year-old seedling from a nearby nursery into the bag, which he then supported with a bamboo stake.

He followed the same procedure with more polybags and placed all of them in a row with a distance of one metre between each tree. Two years later, the seedlings had attained a height of 12 feet.

Once the trees were ready, the team dug pits on the roadside, and the bottom layer of the polybag was removed and the tree planted.

Rao says that the entire exercise cost around Rs 400 per plant, which is cheaper than the previous method, and the survival rate is 100 percent.

He currently uses fast-growing species such as gulmohar, raintree, mahogany, and kadam. Today, close to 800 trees varying between 10–15 feet have been planted along NH 44.