Trial Design and Analysis

Being able to calculate the viability of a fertiliser or variety under certain conditions is an important step in building confidence in spatial application.

Are your trials telling you the full story? Are they being analysed correctly?

Below is a trial showing a particular fertiliser treatment resulting in a yield increase of 0.3 b/ha of cotton. In dollar terms this was around $100/ha.

Image 1 shows the yield by soil type.

Analysis shows the lighter soils yield more strongly than the heavier soils. Normally an indication of over irrigation, wet season or subsoil constraints limiting yield in the heavier soils.

Image 2 includes the trial design which was a change from treated to untreated every 24 metres.

Analysis shows a yield response of 0.3 bales of cotton per hectare. Approximately a $100/ha profit increase.

Image 3 shows the relationship between soils and their treatments.

Analysis of this shows the soil types described here as Low EM and Low/Med EM have yield increases of 1.2 bales per hectare and 0.3 bales per hectare where the other soils are almost negligable.

This indicates that while an economic response was thought to be measured across the entire field the detailed results show that only the light soils responded (and by a greater amount than first thought).

This information can now be used to prove the viability of the product and it’s application using variable rate.