Agriculture and Environment: Tea

Better Management Practices: Reduce Fertiliser Use

Financial sustainability of tea production may require the use of fertiliser on some soils, especially over time.

In India, for example, higher levels of fertilisation are required to make plantations financially viable. However, the principle should be that nutrient inputs should not exceed off-take in the harvested product.

Efficiency will depend on the application rate, soil type, soil depth, slope, temperature, and climate. In order to achieve this, nutrient loss through wastes, erosion, effluents and soil exposure at the time of replanting must be minimised.

Nitrogen through biological fixation
In addition, because applied nitrogen is so volatile, every effort should be made to increase nitrogen through biological fixation. Application of fertiliser should be avoided within 3 to 4 meters of freshwater systems. Algal blooms in ponds within the farm are an indication of contamination from fertiliser runoff, particularly nitrogen.

In Kenya, about 80% efficiency of input use has been achieved by keeping fertiliser applications at an average of 150 kilograms of nitrogen per hectare per year or less.

Careful timing of fertiliser applications and monitoring of crop can also help reduce fertiliser use. For example, in Kenya a yield of green leaf of less than 6,500 kilograms per hectare per year is an indication of inadequate fertiliser; dark, green, fleshy and succulent shoots throughout the sorting table are an indication of excess applications of nitrogen.

Organic matter - rich and wholesome source of nutrients
Ash from eucalyptus (or other fuelwood), from dryers, or from old tea plants is a potential source of potassium, a nutrient essential for plant growth. However, ash is alkaline, and tea plants do not benefit from the added alkalinity (unless soils have become extremely acidic). Instead of using it on the plantations, the ash should be used on the soil of the trees grown from fuel plantations, which will improve fertility in the fuelwood plantings.

The application of organic matter and compost can reduce the requirement for inorganic fertiliser applications. This results in part because the application provides needed nutrients. In addition, however, the organic matter binds with nutrients in the soil as well as those added subsequently, effectively increasing the soil's nutrient-holding capacity.

The right mix!
Another way to reduce fertiliser use is through the choice of appropriate nutrients. For example, ground rock phosphate applied where soil is acidic during land preparation before planting or replanting reduces the subsequent reliance on soluble phosphate fertiliser, which is more easily leached into nearby streams and ponds.

Similarly, if soils are or become extremely acidic (below pH 4), lime should be applied at the time of pruning. Dolomitic rather than burned (quick) lime should be used if available. It will release more slowly in the soil and so tend to require fewer applications over time.