A programme on the radio talking about “truth” a collection of news items concerning “UFO’s” and recent agricultural presentations I have been privy too made me recall the highly successful TV series that ran from 1993 until 2016, The X-Files.
Illusory truth, is the tendency to believe false information to be correct after repeated exposure to it. Individuals rely on whether the information is in line with their understanding or if it feels familiar. The first condition is logical, as people compare new information with what they already know to be true. Repetition makes statements easier to process relative to new, unrepeated statements, leading people to believe that the repeated conclusion is more truthful.
In reality the word truth should signify true facts about something, rather than the things that have been invented or guessed. So what has this to do with farming?
Currently there is a great interest and value placed upon “On-Farm Trials” since often heard is a statement “all those manufacture trials are biased.”
Are On-Farm Trials conducted in a manner that provides a true and accurate answer to current farming dilemma’s?
When I consider my own, now historical trials involvement a few principles spring to mind that I would consider very relevant to the current raft of On-Farm Trials work.
Formulate a question that can be tested simply and effectively. Keep it simple by asking Yes or No questions or looking at only one variable.
Include a control treatment to test others against. Conveniently “Standard Farm Practice” works well as the control. Controls are not used to adjust yield results but rather to provide a baseline.
Randomize and replicate to account for field variability and also to build statistical power to detect differences between treatments.
Replication is extremely important to understand how much variability exists within the On-Farm Trial results. The lower the variability the greater the certainty of the results. You really do need a minimum of four replicates. Splitting a field in half for comparison is not a sound way to conduct on-farm trials because the data will not be accurate enough to use in other locations.
Use wide plots or strips to buffer treatment effects from neighbouring plots.
This is particularly important for foliar applications or where there is potential for lateral movement of nutrients such as nitrogen.
Take notes and observe throughout the growing season to fully understand what impact is occurring due to treatment effects.
While yields and profits are important at the end of the year, knowing if and when a treatment might have an adverse effect may indicate the ability to overcome them if results are promising.
Analysing the results
Treatment differences may be caused by several factors other than the treatment itself. Previous cropping, soil variation and management, drainage, soil fertility, moisture availability, insect, weed or, disease pressure, differences in planting or harvesting techniques, or field history are all going to influence outcomes.
Where sufficient replicates are included, statistics can be used to determine if variations are attributable to the treatment or to factors not controllable by the On-Farm Trial.
Statistics provide a rigorous process for comparing treatments. A least significant difference (LSD) maybe calculated to describe the smallest difference allowable between two treatments to be statistically different. If you cannot do something as simple as this then your time and money is for the most part – wasted.
All those manufacture trials could well be less biased than the current “On-Farm Trial” community would have us believe!