Microbial biomass activity of a sodic Lixisol reclaimed with gypsum and clean water irrigation in urban vegetable systems of Burkina Faso

Background

Little is known about the effects of gypsum application to remediate saline–sodic soils in the tropics and the role of microbial indicators in soil reclamation.

Aims

Our study aimed at (1) remediating a highly weathered, irrigated sodic Lixisol under prolonged urban crop production by clean water and gypsum application and (2) to determine the remediation effects on soil microbial indices.

Methods

A three-factorial on-farm experiment with maize (Zea mays L.) was used to study effects on soil microbial biomass of (1) soil degradation at two levels of salinity, (2) irrigation with clean water and wastewater, and (3) the impact of added gypsum during a typical growing season.

Results

At the high-degradation site, the 0.5 M K₂SO₄ extractable carbon (C) content was 40% higher than at the low-degradation site. In addition, microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were 20% lower than at the low-degradation site, while fungal ergosterol was even 40% lower, leading to a 33% lower ergosterol/MBC ratio. Wastewater irrigation increased MBN but decreased ergosterol content at the low-degradation site while having no effect at the high-degradation site. Gypsum amendment led to higher MBN at the low-degradation site but to lower MBN at the high-degradation site. Gypsum amendment always increased the ergosterol content whereby this increase was stronger at the low-degradation site, especially in combination with wastewater irrigation.

Conclusions

From a microbial perspective, high soil degradation levels should be avoided by treatment of a saline–sodic wastewater prior to its use for irrigation rather than relying on future remediation strategies of affected field sites.     

Water quality in forest and village ponds in Burkina Faso (western Africa)

Forest ecosystems help conserve the quality of water resources in aquatic habitats. The conservation of biological diversity in aquatic and terrestrial ecosystems remains a communal concern. Aquatic ecosystems and resources are vulnerable but can be preserved and protected by forests. In sub-Saharan regions of Africa, water from ecosystems such as ponds still play important role in the livelihood of local populations. Water from temporary ponds is used by local populations for multiple needs; however, in this part of the world, the population is increasing, thus increasing human needs and activities and land use in the region. Land-use changes lead to deforestation, land degradation and the decline in freshwater, affecting human health and well-being. Forest degradation leads to the decline in ecosystem goods and services, particularly those related to watersheds. This study conducted in eastern Burkina Faso aimed to assess water quality of temporary ponds in protected forest areas (reserves) and surrounding villages. It was conducted in 61 temporary ponds where physical, chemical and biological variables were measured, such as water surface area, depth, transparency, macrophyte cover, pH, dissolved O₂, conductivity, nutrient concentrations and algae biomass. The results showed that at p < 5%, water surface area (p = 0.02), depth (p = 0.00), nutrient content (p = 0.00), and algae biomass (p = 0.04) were significantly higher outside reserves than inside reserves. In contrast, macrophyte cover (mean cover percentages 53 vs. 44.5%) and water transparency (p = 0.02) were higher inside reserves. The variations in conductivity and pH were not significant. All trends showed the influences of human activities on water characteristics and the role forests and land cover had in preventing negative human impacts and disturbance of temporary ponds. Forests and land cover are important to water quality conservation and algae biomass regulation in temporary ponds. Protecting and managing forests is therefore an essential part of future strategies for limiting algal blooms and their negative consequences, maintaining water quality and providing clean water to citizens.