Keywords: Fertiliser, Physical properties of fertilisers, Fertiliser flow, Fertiliser spreading, Uniformity.
The performance of any fertiliser spreading mechanism can be regarded as having components relating to the metering of a given application rate of material and a system for distributing that material uniformly over the area to be treated. The relative importance of the two functions will depend upon detail machine design considerations but in all cases, the physical properties of the fertiliser material will be major factors influencing overall system performance.
The metering of fertiliser through a range of different mechanisms is a function of the flow characteristics of the material. This paper examines methods that are being developed to quantify such flow characteristics both in terms of a laboratory test and the implications for full-scale spreader performance.
To date, it has not proved possible to relate laboratory measurements of the physical properties of a fertiliser material to a single parameter describing its likely performance in a range of spreading systems. An approach is described based on the full-scale measurement of both longitudinal and transverse distribution patterns that are then combined to give an expected level of uniformity over treated areas.
Particular features of this approach relate to the use of reference materials to define fertiliser spreading quality categories and the ability to relate such categories for nitrogen fertilisers to likely crop yield and financial returns.
Methods by which the approach is being developed to use an indoor test rig simulating the operation of a full-scale spreader but with good control of operating conditions and the variables to be measured are also described. These developments are aimed at overcoming many of the limitations that have been identified as relating to the existing scheme and provide a basis for the further development of the concepts that have been successfully used to date.
P C H Miller, Silsoe Research Institute, Wrest Park, Silsoe, Bedford, UK
31 pages, 11 figures, 5 tables, 17 refs.