Agriculture and Environment: Tea

Better Management Practices: Reduce Soil Erosion & Degradation

Soil erosion can be high in tea plantations. They are often planted in areas of considerable slope that receive high levels of rainfall.

Erosion is most extensive during periods of planting or replanting, when as much as 75 metric tons of soil per hectare per year can be lost, as compared to 20 metric tons or less for well-managed seedlings or vegetatively propagated tea (UNESCAP 2002).

Maintain ground cover
It is important that ground cover be maintained at all times. If an area has to be replanted, the exposed ground should be mulched and replanted with vegetation as quickly as possible. If the land being planted slopes significantly, then planting should be undertaken on the contour.

This is particularly important on slopes that are over 25 degrees (in fact, a rigorous analysis should be undertaken to insure that such slopes are even economically viable for planting in the first place).

On particularly steep slopes, single bands of a grass such as napier (Pennisetum purpureum) can be established every 5-10 rows of tea to supplement contour planting. The grass can be harvested for mulch or for fodder.

Several other practices can be used to reduce erosion:

• Environmental impact assessments can help identify problematic areas of concern.
• Digging silt pits in newly planted areas can arrest runoff and encourage water retention.
• Mechanical harvesting should be avoided in any areas where soil erosion is likely to be severe.
• Ground cover plantings along field edges should be used to reduce erosion.
• Careful siting and construction activities (e.g., drain design, road and path layout, etc.) can reduce soil erosion significantly.
• Tea prunings can be used to cover all bare soils to prevent soil erosion.
• Soil should not be taken from fields for use in nurseries. This material can just as easily be created from compost mixed with soil in the nursery area.
  
  

Use organic matter to restore soil fertility
Senapati et al. (2002) report that several research projects begun in 1991 on 6 estates in southern India indicate that there are several ways to restore soil fertility and enhance tea production. The application of organic matter to the soil appears to have great potential to increase soil microorganisms and earthworms.

Earthworms again!
In general, more earthworms present in the soil mean higher total green leaf tea yields. As soils are degraded their earthworm populations decline and termite populations increase. As a result, the proportion of termites to earthworms appears to be a good indicator for assessing soil degradation. Yield increases from bio-organic fertilisation ranged from 75.9 to 282%.

This produced profits of U.S. $5,500 per hectare per year compared to conventional cultivation with standard synthetic fertilisers. Such bioorganic fertilisers can be made by composting tea prunings and high-quality organic matter, and mixing the material with earthworms. This was shown to be a more effective way to increase yields than the application of fertilisers alone.

Different field trials showed that yields were increased from 79.5 to 276% over conventional fertiliser use alone. The vegetative propagation of tea allows both for quicker growing and ground cover establishment. The adoption of these practices can increase production by 50%. However, in addition to increased production, producers also restore their land, improve the quality of their leaf, and conserve soil.

Prudent combinations for long-term gains
The combination of these factors will increase the net value of production both in the short and medium terms. One of the main measures of soil health and fertility is the content of organic matter, so management should be focused on maintaining or increasing organic matter.

In addition, deterioration of soil structure may result from compaction, especially from harvesting mechanisation, from changes in pH, from salinity, or from exposure. Mulching with tea prunings, leaf, or other organic matter, planting shade trees, or even planting cover crops for 2 years prior to replanting of tea plantations can also increase organic matter.