Assessing the condition and capability of soils in cocoa districts of Ghana using geovisualization

Abstract

Improving agricultural soil conditions is essential for attaining global soil security against land degradation. This requires the use of complex geospatial farm soil information, the absence of which hinders sustainable cocoa (Theobroma cacao L.) soil management in West Africa. This study seeks to create geospatial visibility (awareness) on the conditions and capabilities of cocoa soils. Specifically, to examine the geospatial distribution of soil organic carbon (OC), clay, pH, iron (Fe) and aluminium (Al) in the entire cocoa-growing Districts of Ghana. A visual analysis of geographically referenced secondary data from farm soil survey conducted by the National Cocoa Rehabilitation Programme (NCRP) of Ghana Cocoa Board (COCOBOD) was made. The data were collected based on stratified random sampling of soils at 20 cm depth in 739 newly established cocoa farms, covering 60 Districts. R-GIS enabled descriptive analysis that showed District level mean and standard deviation of these soil properties in colour-graduated thematic maps. Generally, Cocoa District soils were low with 0.42 g kg−1 OC, 5.3 pH, 0.09 cmolc kg−1 Fe with Al in excess of 7.48 cmolc kg−1. Soil clay capability was 22.2%. Combined with a dearth of awareness, policy and economic incentives to improve these conditions, imply cocoa soil security is very low as well. The geovisual maps provide spatially explicit soil information for managing and monitoring cocoa soil security, specifically, Al, OC and pH at the Districts. Farmers, agricultural extension workers, soil scientists, agronomists, policymakers like COCOBOD and development practitioners may use these findings as a guide for restoring cocoa soils.