Abstract

In many plantations Bombax ceiba [B. malabaricum] does not attain sufficient height by the rotation age of 25 yr. The present project was taken up to ascertain whether stunting is due to site factors, especially soil. One hundred and sixty-three subsites of 20X20 m were marked in 71 plantations from southern, central and northern regions of Kerala for assaying site and tree parameters. One soil sample was taken from 0-20 cm depth in each of the 163 subsites and 5 dominant trees around the soil sample were selected for top height and girth measurements. The soil samples were analysed for gravel, sand, silt and clay separates, pH, organic carbon, exchange acidity and exchangeable bases. Plantation altitude varied from 25 to 850 m with most in the 25-150 m range. The majority of the subsites were well drained and all had good undergrowth. Thirteen subsites had pure stands, but the others were mixed either with teak or Ailanthus. The correlation coefficient for d.b.h. vs. height was 0.87 indicating that the linear growth was not spindly. The correlation coefficients for height vs. age and d.b.h. vs. age were poor (0.38 and 0.40) suggesting suppression of height and diameter growth. For comparative purposes, height data were transformed to 25 yr and the midpoint between max. and min. height was the height (15 m) used to differentiate stunted and nonstunted stands. Height varied from 6.7 to 21.3 m and decreased towards the north. Mean differences of soil parameters in stunted and nonstunted plantations were significant for all except sand and organic carbon in the southern region, nonsignificant for all parameters in the central region and nonsignificant for all except gravel and organic carbon in the northern region. The inconsistent trends of mean differences for soil parameters in stunted and nonstunted plantations suggest no definite relations between tree height and the various soil parameters. It is suggested that the feasibility of planting B. malabaricum in central and northern regions whereit does not reach sufficient height needs appraisal