Minimal cultivation is most popular way of establishing a seedbed in preparation for drilling cereals. With the escalating cost of fuel it is certainly a less expensive way of crop establishment. But such a technique leaves straw trash on the surface which may "lock up" residual herbicides.
By doing so this represents in effect a potential loss of active ingredient to weed control. As the activity of PDM is via root uptake, a sufficient active ingredient loading must be delivered to the soil for it to be effective.
However results of a recent study conducted by Paul Miller of NIABTAG shows that the that micro encapsulation formulation of Stomp Aqua reduces binding of the active due to easier wash-off behaviour.
What was the objective of the study?
The study set out to define the best pendimethalin formulation for minimal tillage systems by investigating how different residual formulations behaved with regard to their retention on straw. Any variability in straw retention would also indicate variability in the amount of active that is available - the herbicide that showed the least binding to straw under different conditions is therefore preferable.
The experiment at Silsoe Spray Applications Unit was conducted to demonstrate the retention behaviour of different formulations of pendimethalin – PDM 330 EC, Stomp 400 SC, Cinder (CS) and Stomp Aqua (CS), to trash in typical minimal tillage field conditions.
Methodology
The PDM formulations were applied in two water volumes (100 l/ha and 200 l/ha) to sample trays containing soil and straw. The soil/straw surfaces were sprayed using a track sprayer arrangement, mimicking normal sprayers in the field. Different rain regimes were then applied 24 hours after the herbicide application to mimic varying weather conditions and soil moistures.
There were 4 different rain treatments
• Dry straw followed by one rain event
• Dry straw followed by no rain
• Wet straw followed by one rain event
• Wet straw with no rain
The straw samples were harvested after 2 hours, frozen and double bagged, packed, insulated and sent of for detailed high tech analysis using HPLC-MS/MS analysis. The analysis gave the percentage increase in PDM available in the straw.
Results
The results showed that in all situations Stomp Aqua showed the least binding to straw than other PDM formulations, even another capsule suspension such as Cinder, and so would be the PDM of choice for effective weed control in minimal tillage systems.
Stomp Aqua’s binding to straw was less pronounced when the straw was dry before application and when applied at 100 l/ha.
Even on wet straw at 200 l/ha it was the best formulation, with the least straw binding.
Its lower straw retention was considerably better than the EC and SC formulations.
Additional supporting evidence for Stomp Aqua as the superior PDM
Stomp Aqua is the best source of pendimethalin and has been proven to have significantly improved microcapsules to other microencapsulated formulations.
For the grower this means superior surface stability and targeted release of the active, leading to effective weed control and improved crop selectivity in speciality crops. It also means flexibility in all tillage systems and under different environmental conditions.
For the user it means superior handling characteristics, with a low odour, less staining and quicker sprayer filling and rinsing.
For the environment this means lower use rates and no organic solvents.
