The Effects of Biochar in Sri Lankan Tea Plantations

We drink a lot of tea in the office, and recently we noticed an interesting article looking at the effects of biochar in tea production.  The article titled “Using Biochar to Improve Soil Health and Leaf Production at Tea Plantations in Sri Lanka” presents preliminary results from research aiming to increase crop productivity, reduce chemical and fertilizer use, and to remediate degraded soils.

Read a summary of the article below. 

Sri Lanka is one of the world’s leading tea producers. Dilmah Tea, a Sri Lankan company, is stepping away from large scale processing to smaller-scale farms with onsite picking and packaging of tea. Nevertheless, tea monoculture has large environmental impacts, especially on land and soil quality. To address these effects and assist with environmental conservation, Dilmah Tea created the Dilmah Conservation.

Soil degradation is a major concern in tea plantations as poor soil management has led to significant reductions in soil quality. To address these concerns, a Bio-remediation program was initiated in 2008, and is currently led by Dr. J.C. Krishnaratne of the Dilmah Conservation. The program is currently investigating the effects of biochar application to soil at the Palmadulla field and Nawalapitiya plantations. The team produced a wood-chip biochar onsite with an updraft pyrolyzer made from steel drums. Biochar of varying particle size was incorporated into the soil.

Findings from soil sampling:

Nine months after Biochar application, soil samples (from 15-20 cm depth) were tested in the laboratory. They found that the biochar-treated soils had higher amounts of organic matter, but lower pH than control samples. Microbial activity was measured through a simple cotton strip assay, where tensile strength of cotton is measured after an exposure period to soil. Microbial activity tests revealed a higher degree of microbial activity in the biochar-amended soils. The team is conducting further testing for a larger sample size before publishing their data.

“If biochar can be shown to have a consistent beneficial effect on soil microbial populations, increased plant growth, and the ability of the soil to withstand drought, the tea industry in Sri Lanka can benefit greatly; not only with larger production but also in decreased chemical fertilizer use and improved soil health.”

Findings from field observations and plant growth:

New leaf growth in the biochar treatment was a darker color green than that of the control, but no attempts at quantifying this effect were performed.  Because darker leaf color suggests a higher chlorophyll content, and would result in a more valuable manufactured tea, more data is needed to prove this effect. About six months after application to the root zone, biochar-treated crops showed an increase in new growth compared to control treatments. The sensitivity of tea to dry weather is a major concern; data recorded over a thirty day period of dry weather showed that the biochar treatment led to a difference of up to 83.27% crop yield increase against the control.

Future Work:

The team is setting up more in-depth trials to determine optimal usage and biochar particle size according to soil conditions. “The biochar requirements for the in-depth trials showcase the need for an industrial-scale pyrolyzer to make biochar on site.”  The team hopes to collect more data in the next 6-12 months, and is also looking to study the effects of biochar to increase soil carbon sequestration.

Once again, the use of biochar in the soil has demonstrated interesting positive effects on growth, quality, and tolerance to harsh conditions (drought). More research is needed, but it is encouraging to see that biochar treatments can be a simple way to simultaneously  improve crop production and ecological sustainability.

Read the full article for more details.

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