Agriculture and Environment: Rubber
Better Management Practices: Reduce Soil Erosion
Several techniques can be employed to reduce soil erosion.
Each of these practices also helps to build organic matter, maintain soil nutrients and soil structure, retain water, and support microorganisms that benefit the maintenance, nutrient cycling, and building of soil.
Countouring & Terracing
On steep, hilly terrain rubber trees should be planted on the contour to prevent soil erosion; this process is known as contouring. Terraces do an even better job of reducing erosion, but these require considerable investments to build (Goldthorpe 1993).
Silt pits and Bunds
Soil erosion along terraces and on gentle slopes can be minimised by digging silt pits and constructing bunds. Silt pits trap the soil particles that are carried in runoff; they also hold some of the rainfall on site so it has time to sink into the ground.
Bunds are earthen embankments that check the flow of water during heavy rains (Goldthorpe 1993). Planting bushy materials on the bunds can further minimise erosion after the bunds have settled.
Keeping the ground covered is one of the best ways to minimise erosion. Natural vegetation like ferns, grasses, and shrubs could be encouraged to rapidly cover the exposed soil surface during planting.
Benefits of planting legumes
In the absence of natural vegetation, rapidly spreading creeping legumes can be sown as cover crops around the young rubber trees. Legumes increase nitrogen in the soil and reduce the need for chemical fertilisers. Equally important, they reduce erosion and exposure to the elements and increase organic matter.
Mulch, proving useful again
Mulch around the base of rubber trees prevents soil exposure and holds nutrients and moisture, which is especially important during the establishment of plantations. Mulch also reduces chemical runoff. Mulch can be created from clearing the undergrowth in the plantations or from trimmings cut from the trees themselves. Mulch is most important during the early years of plantation establishment, before the canopy closes, when both of these sources are more plentiful.
Intercropping
Another way to reduce soil erosion after the planting stage is intercropping, growing other plants between the rubber trees. Intercropping has been used effectively with cacao and coffee in the Philippines, with tea and cacao in Indonesia, and with hearts of palm in Brazil.
However, intercropping has not been widely practiced with rubber except by some integrated farms with multiple product lines. Most plants are shaded out by mature rubber trees. For about 3 months per year, however, rubber trees shed their leaves, leaving the understory with sufficient sunlight for other crops to grow.
Short-lived legumes could be planted during this period to rejuvenate the soil provided there is enough moisture (often the trees lose their leaves during the dry season). Intercropping provides the additional benefit of supporting greater biodiversity, especially in plantations that have been cleared and replanted.
Research suggests that the biomass of the mature rubber plantation at 450 metric tons per hectare, while somewhat less than the biomass of 475 to 664 metric tons per hectare for Malaysian forests, compares favourably to the 295 to 475 metric tons per hectare for forests in Brazil, Papua New Guinea, and Thailand.
A nutritionally self-sustaining ecosystem
Rubber plantations also perform well from the point of view of canopy cover and the production of leaf litter (Goldthorpe 1993). Sivanadyan and Moris (1992) conclude that a mature rubber plantation is a nutritionally self-sustaining ecosystem unlike other agricultural systems. Research in India has suggested that mature rubber plantations with closed canopies generate and recycle more nutrients and biomass each year than are harvested.
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