Spatial variability of selected soil micronutrients under smallholder crop production in Zanyokwe, Eastern Cape, South Africa

Abstract

Understanding spatial variability of soil nutrients, including that of micronutrients, is important for establishing best management practices in smallholder crop production. The objective of this study was to determine the status and spatial variability of potentially available zinc (Zn), copper (Cu), manganese (Mn) and iron (Fe) for selective management at Zanyokwe Irrigation Scheme. Soil samples were collected from the 0–20 cm depth on 50 m × 50 m grids and coordinates of the sampling points were recorded using a global positioning system (GPS). The samples were analysed for Zn, Cu, Mn and Fe after extraction with EDTA. The GPS coordinates and corresponding micronutrient values were interpolated using simple kriging to produce continuous raster surfaces, which were then reclassified, using prescribed limits, to produce soil micronutrient maps. Zinc was deficient and exhibited the highest spatial variability, within short distances. There was limited spatial variability of Cu, Mn and Fe. The study highlighted the need for the creation of management zones for Zn availability. Field studies are recommended to establish the extent to which Zn is limiting yields and nutritional quality of crops grown at the scheme.

Keywords:

• copper
• crop yield
• iron
• manganese
• zinc