Mineral concentration and standing crop yield dynamics of forages in semi-arid communal grazing lands of South Africa: effect of landscape and season
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Semi-arid African rangelands are characterized by heterogeneous topography and distribution of grazing forages. In these ecosystems, grasses are the main sources of livestock feed with few species contributing to the bulk of the nutrient intake. Forage yield and elements availability play a significant role in determining the adequacy of nutrients intake and fodder flow plan, but limited information is available on their dynamics for the semi-arid South African communal rangelands. There is also little data on factors influencing concentrations of forage minerals throughout the year. We investigated the standing crop yield (DM) and element concentrations of major forages and evaluated their spatial and temporal variations. We conducted the study in two semi-arid (Highland and Lowland) communal rangelands in the Eastern Cape province, South Africa. Herbages for major forage species were harvested from three landscape positions (upland, slopping and bottomland) over four seasons (summer, autumn, winter and spring) in 2012/2013 to determine DM, macro and micro element concentrations. Our results confirm great variations in DM and mineral contents between grass species, across landscapes and seasons. Compared to the Lowland, more elements in the Highland showed interaction effects between species, landscape or seasons. While species variations are attributed mainly to biotic and anthropogenic factors, spatial and temporal variations may be due to topographic, edaphic and/or climatic variations. Minerals most likely to be found deficient were P, Mg, Zn, Cu and K, but this depends on seasons and landscapes. Their amendments through supplementation may deserve utmost consideration.