Abstract

An extensive field trial was conducted at Mundakadavu, Karulai Range, Nilambur Forest Division, Kerala, to study the effect of slash burning on soil properties, weed growth, taungya yield and growth of teak (Tectona grandis) in a second rotation plantation. The original 55-yr-old teak plantation was felled in October 1991, and the trees converted to logs and billets. All material _30 cm girth over bark (g.o.b.) was removed from the site and the remaining slash evenly distributed. (treatments A, D);for the remaining treatments (B, C, E, F), wood down to g.o.b. 10 cm was collected and removed for sale as fuelwood, and the slash again evenly distributed. Estimates were made of the remaining slash before burning in March 1982 (treatments A, B, D and E); treatments C and F were not burned. Fresh teak stumps prepared from 1-yr-old nursery seedlings were planted in all plots in May 1982 at 2X2 m spacing. Taungya crops of paddy (rice, Oryza sativa, first crop) and gingelly (Sesamum indicum, second crop) were grown during the first year of teak establishment in treatments A-C, and tapioca ([cassava] Manihot esculenta) in the second year. Burning significantly increased base content of the soil, changing it from acid (pH 6.26-6.49) to alkaline (pH 7.23-7.63), but within 6 months these values had returned to pre-burning levels. Burning reduced weed growth during the first 3 months after planting, but not significantly after this. Taungya crop yields were not significantly different between treatments for rice, and there was no indication that they varied for the other 2 crops (although these results could not be statistically analysed). None of the treatments significantly affected teak survival, and initial variations in height growth between treatmentsover the first 3 yr had disappeared by 42 months. Salvaging 10-30 cm g.o.b. material for fuelwood gave a net revenue of Rs 756/ha (1982 prices) after meeting labour costs, and since this made no difference to teak and crop growth it is suggested that it becomes normal practice; the remaining slash (1.9 kg/m2 , as opposed to 4.7 kg/m2 of all material up to 30 cm g.o.b.) can then be either lightly burned or removed