Agriculture and Environment: Tea

Environmental Impacts of Production: Soil Degradation

Monocrop production and its associated chemical inputs not only reduce soil biodiversity and soil organic matter, but also compact soils (especially in areas that workers and machinery pass over). Compacted soils are low in oxygen.

The farmer friendly earthworms!
Earthworms can play an important role in oxygenating soil and are commonly used as an indicator of soil health. Researchers have found that tea plantation soil contained between one-third and one-half the number of earthworms per square metre as the nearby natural forest soil. In addition, most earthworms found in tea plantations were not native species to the area (Senapati et al. 2002).

Vulnerable to soil erosion
Although well-established tea plants are deep-rooted and provide good ground cover, both of which minimise erosion, areas where tea is being planted or replanted are vulnerable to erosion.

A study of soil erosion in Sri Lanka focused on tea, rubber, and coconut plantations. Of these 3 crops' overall growth phases, tea that was replanted on steep slopes had the highest erosion rates, whereas well-established tea had relatively low erosion rates (UNESCAP 2002).

Not only does erosion strip nutrients and topsoil from the agricultural fields, it also causes problems downstream. In Sri Lanka, siltation from erosion is a major problem. Silt fills reservoirs, which reduces hydropower generation and the life of hydroelectric dams (UNESCAP 2002).

Stripped of life
In southern India where some tea estates are more than 100 years old, the soil has become impoverished and yields are stable despite the increasing application of fertilisers and pesticides.

According to Senapati et al. (2002), soil degradation includes, in addition to those factors mentioned above, reduced cation exchange (a measure of a soil's ability to hold stores of nutrients and release them to plants), reduced water absorption and retention, increased acidity of the soil (pH as low as 3.8, which causes concentrations of aluminium to increase to toxic levels), nutrient leaching, and accumulation of natural toxins from tea leaves, which can begin to alter microorganism soil communities.

A vicious cycle
The degradation of tea plantation soil is a cycle that feeds upon itself and increases the environmental degradation from tea production. As the soil is degraded, farmers increasingly rely on chemical inputs to maintain productivity. These inputs then contribute to further soil degradation, which leads to decreased productivity, requiring still more inputs to maintain a profitable tea plantation.

As the soil degrades, more and more of these inputs are eroded or washed away, entering local water systems and harming the local environment. Some tea plantations are now trying alternative methods to restore soil health and increase productivity from the ground up.