Bioremediation at Dilmah tea gardens

Bioremediation through biochar use at Dilmah tea gardens

Dilmah Conservation will work on a bioremediation programme to address the deteriorating soil conditions in many Sri Lankan tea plantations and to explore sustainable solutions to support the industry. Years of neglect due to poor management practices have created unsustainable and unyielding estates and Dilmah Conservation introduced a programme in the tea plantations to address and mitigate the present situation. The aim of the programme is to reduce fertiliser and other artificial inputs by at least 50 per cent while increasing the productivity of the land by at least 50%. The first site for the biochar application was at the Pelmadulla field at Kahawatte and Nawalapitiya Plantations, chosen for their different agronomic and climatic conditions.

The sites selected for field trials had to meet certain specific parameters including plants pruned 16 – 18 months prior to the biochar application, as well as fields fortified with bush frames strong enough to withstand envelope forking for insertion of biochar.

 Soil sampling for laboratory analysis

As part of post biochar applications, the team tested the soil at both sites using a non-auger type soil core extractor to pull samples from a 15 – 20 cm depths. The extracted soil samples were thereafter air dried for four days, and during this moisture reduction period, each set of seven individual samples were kept separate. The research team found that biochar-amended soil had higher amounts of organic matter.

A simple test procedure was carried out to determine soil microbial activity. A calico cloth, 20 cm x 20 cm in diameter was inserted into the soil at several points in the selected as well as at other random parts in the two estates (used as the control). The results indicated a higher degree of microbial activity in the biochar-amended soils.

Field observations and plant growth

The team conducted overall observations at the Pelmadulla field test site four days after the last tea pluck and noticed that fresh shoot development had already taken place. The color of the new leaf growing in the biochar treatment induced soil was a darker green than that of the tea that grew in the area used as control. This suggests higher chlorophyll content, which in tea terms means that the tea eventually manufactured will be a darker representation of black and more valuable.

Project partners: Kahawatte Plantations Limited