Validation and use of a model for the calculation of trace element accumulation in soils

Most agricultural production requires applications of agrichemicals and amendments to promote crop growth and aid soil fertility. These include fertilisers, pesticides and organic amendments, such as composts. Many agrichemicals and soil conditioners contain Trace Elements (TEs) as either active ingredients (e.g., Cu-fungicides) or contaminants. When TE-containing amendments are applied repeatedly to soils and crops, these TEs may accumulate. Consequently, soil fertility may be affected if these TEs are allowed to reach threshold levels, and plant uptake of TEs may reach critical levels for plant growth and food safety. As such, repeated applications of TE-containing products to productive land may limit both the sustainability of productive systems and future land use in areas where these products are applied. It is both useful and necessary to understand likely timeframes for accumulation and to understand sustainable application rates which might be adopted. There are different approaches to determine this. The use of mass-balance models has been employed as one approach to calculate expected soil TE concentrations into the future under specified conditions. We have developed a suitable mass-balance model for the calculation of TE-accumulation in soils under productive systems. We have used the approach that the model should be simple, rationally convenient and work with biologically relevant concentrations. We have validated the model using data from long-term field trials. The validated model was used to calculate TE-accumulation in oil palm production soils from Indonesia. Based on our findings, it is likely that TE-accumulation will reach threshold levels in oil palm plantations in Indonesia within eight years. We predict that production will become limited by phytotoxic concentrations of trace elements. This will deleteriously impact the world’s largest vegetable oil production system. This model may therefore be a useful tool in determining the sustainability of inputs into productive soils in terms of TE-accumulation.