Abstract
Deficiency or excess of certain trace elements in the soil causes problems for agriculture, including disorders of grazing ruminants. Geostatistics has been used to map the probability that trace element concentrations in soil exceed or fall below particular thresholds. However, deficiency or toxicity problems may depend on interactions between elements in the soil. Here we show how cokriging from a regional survey of topsoil geochemistry can be used to map the risk of deficiency, and the best management intervention, where both depend on the interaction between two elements. Our case study is on cobalt. Farmers and their advisors in Ireland use index values for the concentration of total soil cobalt and manganese to identify where grazing sheep are at risk of cobalt deficiency. We use topsoil data from a regional geochemical survey across six counties of Ireland to form local cokriging predictions of cobalt and manganese concentrations with an attendant distribution which reflects the joint uncertainty of these predictions. From this distribution we then compute conditional probabilities for different combinations of cobalt and manganese index values, and so for the corresponding inferred risk to sheep of cobalt deficiency and the appropriateness of different management interventions. We represent these results as maps, using a verbal scale for the communication of uncertain information. This scale is based on one used by the Intergovernmental Panel on Climate Change, modified in light of some recent research on its effectiveness.
Highlights
Geochemistry is an important factor in many problems of soil management
Cobalt deficiency can induce a deficiency of vitamin B12 which in turn causes various metabolic disorders (Stangl et al, 2000) which lead to conditions such as poor thrift and ‘pine’ in sheep (Coulter and Lalor, 2008)
But rather less (0–3%) in other counties of the Tellus Border region (Central Statistics Office, 2012). These results show how data from a regional geochemical survey, through an appropriate multivariate geostatistical analysis, can be used to map variations in the concentrations of topsoil Co and Mn against recognised thresholds, and so the susceptibility of grazing sheep to Co deficiency
Summary
Geochemistry is an important factor in many problems of soil management. The availability of particular trace elements in the soil to crops and grazing livestock can cause problems of either deficiency or toxicity. In this paper we consider the example of cobalt (Co) deficiency for sheep and other ruminants on pastures where the Co status of the grass may be inadequate because of soil geochemical factors. Ruminants depend on rumen bacteria to synthesise their supply of vitamin B12, and these bacteria require a source of Co. Cobalt deficiency can induce a deficiency of vitamin B12 which in turn causes various metabolic disorders (Stangl et al, 2000) which lead to conditions such as poor thrift and ‘pine’ in sheep (Coulter and Lalor, 2008). Small concentrations of blood vitamin B12 have been found among Irish cattle herds (Mee and Rogers, 1996), affecting 55% of herds sampled in 1993
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