Reproducing perfect trials results in the field

Article taken from the Agronomist & Arable Farmer

When evaluating inputs through farm sprayers versus traditional trials equipment, changing the nozzle criteria could produce dramatic results.

But can the grower replicate the results from trials in the field?  The evidence of the past seems to suggest not.

During Agrovista’s early demonstrations, many growers were adamant that they could not achieve the same results as well as the company could, through their farm application equipment.

This led Agrovista to conduct a major review of its application development programme.  The conclusion is that the grower’s comments and observations were right.

In order to conduct data for registrations, manufacturers must carry out small plot replicated trials.  This early registration work is vital and must be conducted using small amounts of test product.  Obviously this can only be applied by small plot, hand-held application equipment.

For ease, some product comparisons such as registration trials (due to the small amounts of test materials) must be carried out with hand-held equipment.  You must have a mixture of both, particularly for grass weed trials.

Why is this a problem? Well, if it’s hand-held, the operator becomes the tractor.  The forward speed is about 3.6kph and hence small nozzles.  Coupled with fact that this is a very stable 2-3m boom, the application is practically perfect.  Does this happen in real life?  Using the specialised Agrovista application equipment many trials were conducted with herbicides and fungicides and the result were dramatic.

For example, in black-grass, we examined pre-emergence water volume implications and found that generally the higher the water volume the better the results.

We also found that by changing the nozzle configuration and angling of the nozzles, we could achieve better efficacy.

However, applying higher water volumes was not always desirable from the grower’s perspective and this led to the evolution of the twin line evaluation concept (a grower’s idea).  For pre-emergence applications this proved to be very successful.

For post-emergence applications we know our best effect on contact graminicides would come from the finer droplets.  But again this has practical implications and some applications cannot be applied in under 100l/ha, so the use of twin lines can overcome this.


There is obviously a higher drift issue to consider, with the finer droplets, and to counteract this we are evaluating several materials from our global connections.

However, a word of caution – they can cause major problems if they are not evaluated properly.  In fact, last year we had worse control from adding a test drift control agent.

As drift control agents do not come under any controlled evaluation/registration process, anyone can claim drift control and offer these to the market.

From a biological perspective – take care!  They may make the result worse.  Make sure you see biological data, not just data on physical parameters – our work suggest they are not the same thing.


Agrovista development had to design a unique machine could mimic grower’s application criteria but also:

  • Operate with small amounts of test material
  • Operate at farm speeds up to 16kph and over to show the problems
  • Have the ability to change nozzle types, for different actives
  • Have the ability to change nozzle direction and configuration, to examine drift and efficacy
  • Importantly, be able to conduct replicated trials 


03 February 2014

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