MSc

Root competition between bamboo [Bambusa arundinacea (Retz.) Willd.] and associated tree components in two mixed species systems and root distribution pattern of boundary planted bamboo clumps were evaluated. Root competition was assessed using 32P soil injection technique in two cultural systems involving bamboo viz. teak (Tectona grandis Linn. F.) – bamboo and Vateria (Vateria indica Linn.) –bamboo). Experimental units were selected considering distance between bamboo clumps and the nearest Vateria/teak. 32P was applied to two soil depths (25 and 50 cm). Each lateral distance-depth combination formed a 32P treatment and it was replicated thrice. To characterise root distribution pattern, modified logarithmic spiral trenching method was used. For this, 18 boundary planted bamboo clumps were randomly selected and classified in to small, medium and large clumps based on clumps diameter ranges. Spiral trenches were dug around the clumps (10 m long). The number of severed roots exposed on both sides of the trench was assessed by placing a 50 x50 cm quadrats against the vertical sides of the trench at 1 m intervals.
Isotopic studies revealed that, 32P absorption by teak or Vateria increased as the lateral distance of bamboo occurrence increased. With respect to depth of application, deeper placement showed higher 32P recovery than shallow placement by teak and Vateria. Uptake of bamboo was inversely related with lateral distance from treated plants. Bamboo clumps may exert a competitive effect upto an 5-6 m radial distance in ten year old clumps growing on lateritic soil. Beyond six meters, the magnitude of competition may be negligible. Recovery of 32P from different soil depths show that more number of physiologically active roots are present at 25 cm than at 50 cm depth.
Excavation studies showed that locations close to the clumps recorded higher rooting intensities and there was a linear decrease in rooting intensity with increasing distance. Size of the bamboo clumps showed discernible differences in respect of spatial root distribution pattern. The medium and small size clumps recorded higher rooting intensities upto 7.5m, beyond this limit the large clumps recorded higher rooting intensities. There were significant difference in bamboo root distribution with depth, 10-30 cm depth of soil horizon registered the higher root counts with nearly 60% of total root counts. Thus, a considerable overlap between the bamboo roots and crop rooting zone in the 30 cm depth and 5-6 m lateral distance zone is possible. However care should be taken while cropping in association with bamboo in this rooting zone.