Abstract

Extensive Eucalyptus tereticornis and E. grandis plantations are being raised in Kerala since early 1960s. As short-rotation eucalypt forestry is similar to agriculture and horticulture, whether monoculture of eucalypt can cause soil deterioration isa genuine question. The project, properties of soils under eucalypts, was initiated with the objective of evaluating changes in soil properties resulting in soil deterioration. Unlike in a long-rotation tree crop such as teak, impact of the highly intensive nature of eucalypt cropping may be felt sooner. However, the intensity of deterioration will depend on initial soil conditions, topography, climate and management practices. On favourable sites there may be no significant effect for two or three rotations but on poorer sites the effect may become apparent soon. Since most of the eucalypt plantations are in uncoppiced stage, comparative profile studies to establish soil changes due to monoculture of eucalypts would be premature. One profile each was chosen from six eucalypt sites to study the properties in general and 62 surface samples (0-20cm) were taken at random from several eucalypt plantations for an overall evaluation of soil properties in uncoppiced and to some extent in first coppiced plantations. Particle-size separates, pH, organic carbon and cation exchange capacity analyses were done. Profile data reveal relatively higher levels of organic carbon and cation exchange capcity indicating the generally high fetility of soils under eucalypts. Surface sample data support the profile data and coppice-wise results also demonstrate higher levels of these integrating parameters in uncoppiced and first coppiced soils. These trends combined with the presence of well-established root system of seedling tree for the coppice trees suggest that the chances of soil deterioration due to continuous eucalypt cropping would be less. Also, the relatively higher levels of organic carbon and cation exchange capacity in the surface horizons of profiles and in the surface samples imply that soil parameters should not limit growth of eucalypts in uncoppiced and to some extent in first coppiced plantations