Quantifying the masses of Macrotermes subhyalinus mounds and evaluating their use as a soil amendment

Maintenance of soil quality is critical to environmental sustainability. However, its input cost is becoming unaffordable to small scale farming communities in Africa. Termites are an important element in traditional land-management practices in the Sahel. In their role as regulators of soil ecosystem processes, termites perform a number of vital functions. Although the application of termite mound materials as available nutrient sources is a common practice on the African continent, little is known about the density of masses of mounds and the amounts of nutrients they contain. First, two representative sites of 2 km x 1 km were delineated and then termite mound abundance was recorded (43 and 30 in the two sites). They were used for volume and mass determinations. The study revealed an average abundance of 10 mounds ha(-1) on Calcisols and 14 mounds ha(-1) on Luvisols, with estimated mound soil masses of 13.5 t ha(-1) and 58.9 t ha(-1), respectively. Because termite mounds contain many pores and void spaces, a regression equation that can estimate the correct termite mound mass from mound volume and mound wall bulk density was developed. This revealed that conventional calculations of mound mass without correction for the voids overestimate the true mass by over 10%. Soil samples were collected from top and bottom parts of 6 selected mounds and in the different horizons of adjacent undisturbed soil profiles. Although insignificant differences in organic carbon and total nitrogen contents between the termite mound materials and the surface horizons of the adjacent soils were found, the termite mounds constitute a store of 27-53 kg ha(-1) of total N and 186.3-306 kg ha(-1) of OC. On both sites, the available P and the exchangeable Mg and K contents of termite mound soil were significantly higher than adjacent soils by 90%, 36% and 188%, respectively. Termite mounds contain a considerable store of plant nutrients and the use of mound material as a soil amendment shows great potential for improving soil chemical fertility. (c) 2011 Elsevier B.V. All rights reserved.