Phosphorus uptake by plants in many soils is limited by strong sorption and fixation of phosphorus, resulting in slow diffusion of added phosphorus and low solution concentrations, according to the Australian Government Grains Research and Development Corporation.
By increasing the concentration of phosphorus in the soil solution, Dr Mike McLaughlin and colleagues at the University of Adelaide Fertiliser Technology Research Centre expect to increase the supply to and uptake by plant roots.
Two approaches are being taken to enhance the mobility of soil phosphorus or fertiliser phosphorus, and thus improve its availability to growing crops. Both relate to interfering with the immobilisation of phosphorus in the soil.
|Dr Fien Degryse Photo: Emma Leonard|
The first approach uses compounds that interact with the cations that make phosphorus unavailable. In many soil types in Australia, phosphorus becomes immobilised through precipitation or surface-complexation with calcium, iron or aluminium minerals.
The other approach is the use of compounds that can directly bind to the phosphorus but still make it available for crop uptake. As yet there are no agronomic applications of phosphate-binding compounds and this is an unexplored research area.
As might be expected, soil type is going to play an important part in the success or failure of these compounds. So Dr Fien Degryse (pictured), who is conducting this research, is testing each compound with a set of standard soils gathered from across Australia.
Dr Degryse is pictured measuring the level of phosphorus diffusion from the treated fertiliser granule, which can be seen to vary considerably with the different soil types. This newly developed visualisation method is used to test the effectiveness of the different compounds in enhancing phosphorus mobility in soil.
This research is being carried out in collaboration with the Mosaic Company.