Improving the spatial arrangement of planting rubber ( Hevea brasiliensis Muell. Arg.) for long-term intercropping

Abstract

Fluctuation in rubber prices has been a serious problem to growers and intercropping with economically important crops offers a practical solution to this issue whilst increasing overall productivity. However, shade given by the rubber canopy limits possibilities of incorporating other sun-liking crops into rubber-based systems. Therefore, the present study aimed to determine suitable spatial arrangements for planting rubber in order to facilitate long-term rubber-based intercropping systems. A field experiment was established in a commercial estate in the Kalutara district of Sri Lanka with five systems of spatial arrangement comprising: (1) single row; (2) double row; (3) three row systems; as well as, (4) three plant triangular; (5) four plant square cluster systems of planting. Planting density of rubber remained constant across the treatments and systems were assessed for a period of 9 years. Plants in single row alleys and in cluster systems performed better than those in other systems with respect to growth and yield. However, canopy closure was rapid in these systems resulting in poor light penetration. Both double row and three row systems provided the highest unshaded area and hence light penetration. Considering overall performance, the double row system was identified as the best system for long-term intercropping. In view of improving the plant growth in the double row system and further facilitating long-term intercropping, a revised version of the double row system was proposed reducing the planting density of rubber.