DEMARCATION OF POTENTIALLY MINERAL-DEFICIENT AREAS IN CENTRAL AND NORTHERN NAMIBIA BY MEANS OF NATURAL CLASSIFICATION SYSTEMS

Mineral deficiencies that lead to production losses often occur concur rently with climatic and management changes. To diagnose these deficie ncies in time to prevent production losses, long-term monitoring of mi neral status is advisable. Different classification systems were exami ned to determine whether areas of possible mineral deficiencies could be identified, so that those which were promising could then be select ed for further monitoring purposes. The classification systems address ed differences in soil, vegetation and geology, and were used to defin e the cattle-ranching areas in the central and northern districts of N amibia. Copper (Cu), iron (Fe), zinc (Zn), manganese (Mn) and cobalt ( Co) concentrations were determined in cattle livers collected at abatt oirs. Pooled faecal grab samples and milk samples were collected by fa rmers, and used to determine phosphorus (P) and calcium (Ca), and iodi ne (I) status, respectively. Areas of low P concentrations could be id entified by all classification systems. The lowest P concentrations we re recorded in samples from the Kalahari-sand area, whereas faecal sam ples collected from cattle on farms in the more arid areas, where the harder soils are mostly found, rarely showed low P concentrations. In the north of the country, low iodine levels were found in milk samples collected from cows grazing on farms in the northern Kalahari broad-l eaved woodland. Areas supporting animals with marginal Cu status, coul d be effectively identified by the detailed soil-classification system of irrigation potential. Copper concentrations were lowest in areas o f arid soils, but no indication of Co, Fe, Zn, or Mn deficiencies were found. For most minerals, the geological classification was the best single indicator of areas of lower concentrations. Significant monthly variation for all minerals could also be detected within the classifi cation system. It is concluded that specific classification systems ca n be useful as indicators of areas with lower mineral concentrations o r possible deficiencies.