Influence of Distributed Soil Landscape Units on Bare Soil Evaporation Dynamics

Abstract

Bare soil evaporation is the process of water vaporization from the soil surface without any vegetation cover. It is a significant component of the global water cycle and can have major implications for agriculture, water resource management, and climate change. Quantifying evaporation rates at both local and global levels can inform water management decisions, particularly in agriculture, in the face of climate change. This study presents an evaporation experiment conducted in a screenhouse over 25 days using soil samples from different series and locations in the northern strip (northern interior (Guinea) savannah zone). The research aimed to: (1) Investigate the effect of different soil types on the evaporation of bare soils from northern Ghana; (2) Derive cumulative water characteristics (CWCs) and Critical Water Content (tcrit); (3) Validate the Hydrus 1-D model for simulating bare soil evaporation; and (4) Develop a bare soil evaporation map for the northern strip (northern interior (Guinea) savannah zone) of Ghana. To achieve these objectives, statistical descriptors such as mean, mode, measures of variability (range, interquartile range, variance, and standard deviation), correlation matrix, and textural triangle were employed. Column evaporation measurements were used to derive cumulative water content and critical water content (tcrit ). The soils were packed into PVC columns (15 cm height, 9 cm diameter) and weighed every 12 hours over the 25-day period. Simultaneously, temperature and relative humidity in the screenhouse were recorded. Inverse modelling, prediction, and regression were used to validate the Hydrus 1-D model for simulating evaporation of bare soils. Maps and raster calculations in QGIS were used to generate semi-distributed landscape models for water management in cultivated soils in the interior savannah zone of Ghana. The study revealed that soil texture and bulk density significantly influence soil evaporation, with different textures and densities affecting critical moisture content, porosity, and water transport. Soil texture also reliably predicts the critical water content, marking the transition between stage 1 and stage 2 evaporation. The Hydrus 1-D model, based on the Richards equation, accurately predicted cumulative evaporation and soil moisture characteristics, though it requires measured hydraulic properties for validation. The use of GIS techniques demonstrated the potential for generating landscape models that support informed water management decisions for cultivated soils in Ghana’s interior savannah zone. The study recommends the adoption of soil-specific management practices, such as mulching for water conservation and organic fertilization.