There is an implicit assumption in cited literature on precision agriculture (PA) that spreading of
fertiliser is performed perfectly in the field leading to uniform application, this is not true. Variation can
be large and often the actual performance of spreading equipment used has never been measured or
verified. In various countries around the world there are quality assurance (QA) systems designed to
achieve a prescribed level of performance. Even within these QA schemes limited testing is
undertaken and always under perfect or near perfect conditions.
The test methods are designed to establish an acceptable bout width which meets an acceptable
evenness of spread if driven accurately. The test does not take into account wind conditions (except
for requiring less than 15kmhr-1 for testing), humidity, slope, terrain or the instrumentation to maintain
the desired bout width.
This paper examines the effect of the farm environment and the physical characteristics of fertilisers
on the spread patterns of fertilisers in the field. Fertilisers with heterogeneous particle size
distributions proved to have more robust spread patterns under field conditions than those with
homogeneous particle size distributions.