An assessment of the soil-conditioning capacity of gums exuded by some trees in Sierra Leone ii: raindrop experiments

This study assesses the soil conditioning capacity of tree gums based on the level of resistance to crumble posed by moulds of treated soils to the impacts of artificial raindrops. Gums exuded by trees viz., Acacia occidental and Parkia bicolor as well as a sample of poly(vinyl) alcohol (PVA) were used as soil conditioners. The soil samples were a loam, laterite and a leached sandy soil, labeled A, B and C, respectively. The study shows that compared to PVA (an established synthetic soil conditioner), treatments by the tree gums conferred greater conditioning capacity to the soil samples; the conditioning effectiveness of the tree gums was in the order P. bicolor>A. occidentale>PVA. The effectiveness of the all the conditioners increased with concentration with a somewhat leveling effect at high concentrations. An appreciable degree of stability to the raindrops (96.6, 111 and 114 % for samples B, A and C, respectively) was imparted to the soil samples when they were treated with 1% (w/v) CaCl2 solution on its own; prior treatment of the soil samples with the CaCl2 solution enhanced the soil conditioning properties of the tree gums as well as the PVA. The soil conditioning effect was most pronounced in the case of sample B (the lateritic soil) and least pronounced in the case of sample C (the leached sandy soil). These results are interpreted in terms of the physico-chemical properties of the conditioners and of the soil samples.