Tropentag 2023, September 20 - 22, Berlin, Germany "Competing pathways for equitable food systems transformation: trade-offs and synergies."

Impact of shea waste slurry on soil physical properties

¹University of Cape Coast, Dept. of Soil Science, Ghana
²Tianjin University of Science and Technology, Environmental Science, China

Abstract

Vitellaria paradoxa, the shea tree, grows naturally throughout the Sahelian zone in Africa. The subspecies V. paradoxa paradoxa can predominantly be found in the Western part of Africa. In Ghana, shea is predominantly grown in the three northern regions: Upper East, Upper West and Northern Region. The fruit from shea tree (shea fruit) is edible and contains fats. This fat when extracted from the kernel serves as an important lipid material for cosmetics, food, and the pharmaceutical industries. Shea waste slurry (SWS) is a bye-product derived from the fat extraction process and mostly dumped. It hardens on the soil surface. This study was done to examine the physicochemical properties of SWS produced at different production sites and to investigate the effects of SWS application on soil physical properties. SWS was applied at 1%, 3% and 5% (w/w) on a haplic acrisol and ultisol collected from the coastal savannah zone and semi-deciduous forest zone, respectively. The result showed that SWS had bulk densities ranging between 0.56 g cm^-3 to 0.68 g cm^-3, porosity from 28% to 40%, water holding capacity (WHC) of 42% to 48%, particle density of 1.6 g cm^-3, void ratio of 0.51 and moisture content ranging from 25% to 31%. Addition of SWS increased soil porosity by 24% and 23%, WHC by 34% and 25% in the acrisol and ultisol, respectively. Soil bulk density was reduced by 11% and 16% respectively in the acrisol and ultisol. Correlation analysis indicated that the physicochemical properties of SWS positively correlated with physical properties of the two soil types. The possible mechanisms behind the improvements in soil physical properties by SWS application are high porosity, adsorptive nature of SWS and an efficient WHC. It is concluded that application of SWS improves the soil bulk density, enhances soil porosity and WHC.

Keywords: Acrisol, Ghana, shea, slurry, Ultisol, waste

Contact Address: Angela Lartey-Young, University of Cape Coast, Dept. of Soil Science, Cape Coast, Ghana, e-mail: angela.arthurucc.edu.gh