Comparison of medium-term organic and inorganic fertiliser application on leaf nutrient concentration and yield of maize in rural agriculture in the Mbizana area, Eastern Cape province, South Africa

The impact of anthropogenically induced degradation on the vegetation and biochemistry of South African palmiet wetlands

“…Higher soil pH has been shown to result in an increase of phosphorus uptake in vegetation in acid soils (Beukes et al 2012), in this case driving a vegetation community that is less phosphorus limited. This is evidenced by decreasing vegetation N/P ratio and visibly by the higher incidence of alien weeds and competitive tree species such as Acacia mearnsii and Acacia saligna on degraded fragments (Zedler and Kercher 2004).…”

“…We hypothesize that these differences are linked to the impacts of agricultural runoff. We did not measure this, however it is known that fertilizers and lime (usually dolomitic lime) are commonly applied to agricultural fields in the Cape Floristic Region of South Africa, particularly irrigated fields, to increase the pH and nutrient availability of extremely acidic and oligotrophic soils (Beukes et al 2012). Both the Goukou and Kromme catchments have intensive irrigated agriculture adjacent to degraded palmiet wetlands.…”

“…There has been research on the impacts of invasion by alien Acacias on riparian systems, which has shown an increase in nitrogen availability in the soil as well as enhanced phosphorus mineralization rates (Naudé 2012). Impacts from agricultural runoff may include an increase in bioavailable nutrients from fertilizers as well as an increase in pH due to liming practises common in agriculture in the Cape Floristic Region (Beukes et al 2012). In this study, we ask the question: what is the cumulative impact of this complex, multifaceted wetland degradation on soil and groundwater biochemistry and vegetation community composition and chemistry of palmiet wetlands?…”

Quantification of water purification in South African palmiet wetlands

“…It appears that these wetlands are acting as a sink for base cations resulting in an overall decrease in pH along the wetland section. This may possibly be linked to two conflicting mechanisms: first, liming practises from agriculture causing a spike in base cations and carbonates and a concomitant increase in pH in degraded wetland stretches (Beukes et al, 2012), and second, an increase in CO2 in the wetland due to respiration of wetland vegetation and microbes in the soil (Trumbore, 2000), or the release of humic acids upon decomposition, causing a decrease in pH further down the wetland (Keller et al, 2009). The disappearance of nutrients (total phosphorus, potassium and Kjeldahl nitrogen), other ions, and dissolved silicon may be explained to some extent by plant uptake (Fisher and Acreman, 2004), microbial immobilization within the wetlands or adsorption to and retention by the soil (Fisher and Acreman, 2004).…”