Influence of slope aspect and position on soil physical quality and management implications at University of Uyo Teaching and Research Farm, Akwa Ibom State, Nigeria

The effect of north and south aspects (NA and SA) and positions viz upper (US), middle (MS) and lower (LS) on soil physical quality from 2000 to 2020 was evaluated at the University of Uyo Teaching & Research Farm, to identify management factors at the Farm. Results showed that coarse sand increased while clay content decreased significantly (p < 0.05) and soil textural class was loamy sand on slope aspects and positions. Soil bulk density and total porosity were similar on the slope aspects and positions. Saturated hydraulic conductivity was significantly (p < 0.05) higher on SA (10.6 cm h–1) than NA (3.1 cm h–1) but declined by 93.03% and 52.47%, respectively in 20 years. Soil organic carbon, water-stable aggregates, mean-weight diameter of soil aggregates and structural index decreased by 14.81% and 38.33%, 60.53% and 55.53%, 31.26% and 21.71%, and 48.60% and 69.0%, respectively in NA and SA within the 20-year period. One minute infiltration rate was similar on NA and SA, while final infiltration rate, cumulative infiltration, sorptivity and transmissivity were significantly (p < 0.05) different; these soil hydraulic properties decreased in NA and SA by 83.0% and 86.43%, 52.63% and 14.29%, 81.53% and 63.9%, 95.0% and 85.63% and 90.42% and 96.11%, respectively on the aspects after the 20 years. Slope aspects and positions were generally similar in their effects on soil physical quality attributes, most of which were degraded after the 20 years. Principal component analysis (PCA) identified seven soil quality management factors namely (1) water intake, (2) soil texture, (3) soil pore space, (4) and (6) Fe and Al oxide, and (5) and (7) soil structural stability factors that could be used to improve and conserve the soil and water for increases in crop production on the farm.

Effects of solar parks on soil quality, CO2 effluxes and vegetation under Mediterranean climate

Solar energy is increasingly used to produce electricity in Europe, but the environmental impact of constructing and running solar parks (SP) is not yet well studied. Solar park construction requires partial vegetation removal and soil leveling. Additionally, solar panels may alter soil microclimate and functioning. In our study of three French Mediterranean solar parks, we analyzed 1) effects of solar park construction on soil quality by comparing solar park soils with those of semi-natural land cover types (pinewood and shrubland) and abandoned croplands (abandoned vineyards); 2) the effect of solar panels on soil microclimate, CO2 effluxes and vegetation. We measured 21 soil properties of physical, chemical, and microbiological soil quality in one solar park and its surroundings to calculate integrated indicators of soil quality. We surveyed soil temperature and moisture, CO2 effluxes and vegetation below and outside solar panels of three solar parks. Soil aggregate stability was reduced by SP construction resulting in a degradation of soil physical quality. Soil chemical quality and a general indicator of soil quality were lower in anthropogenic (SP and abandoned vineyards) than in semi-natural (pinewood and shrubland) land cover types. However, differences between abandoned vineyards representing the pre-construction land cover type and solar parks were not significant. Solar panels reduced the soil temperature by 10% and soil CO2 effluxes by 50% but did not affect early successional plant communities. Long-term monitoring is needed to evaluate the effects of solar panels on vegetation.