How adjuvants and application techniques improve agchem efficacy

Taken from Agronomist & Arable Farmer, February 2017

Agrovista's Mark Palmer analyses developments in spray application


The vast majority of adjuvant efficacy trials have been conducted using the same traditional small plot trials used to evaluate biological efficacy for product registration applied at lm/s (3.6kph).

However, in the late 1990s we observed that product efficacy was consistently higher in plot trials, compared to that achieved with farm sprayers operating at standard work rates and spray volumes. Farm spray application was reducing herbicide and fungicide efficacy.

To help us to investigate the impact spray application technique has on product efficacy and to discover ways to improve performance, Agrovista built a range of trial sprayers capable of spraying replicated trials at speeds of up to 19.2kph, and for nearly 20 years we have conducted spray application trials.

Early on, we tested a range of application methods, the differences were huge. Combining poor pre- and post-emergence techniques could reduce grass weed control by 50%, for example. We identified that adjuvants could play a crucial role in improving application by reducing spray drift, improving spray deposition pattern, coverage, (whether of soil or plant), or increasing soil adsorption, for example.

We started to develop adjuvants as spray application aids to overcome some of the practical difficulties encountered on farm. We saw that incorrect choice of adjuvant could reduce efficacy, highlighting the need to conduct trials over several seasons prior to launch.

Adjuvants are chemicals that are designed to enhance the efficacy of plant protection products. They can be used to modify the physical characteristics of the spray solution to improve spray deposition and coverage and penetration into the target surface, increasing biological efficacy.

Agrovista and our sister company Helena (North America) and parent Marubeni (Japan) have a global adjuvant R&D programme - the largest of any distributor designing, testing and refining adjuvant chemistry.

The programme has resulted in a proven track record of innovation in spray application, such as the development of the first adjuvants for use with pre-emergence herbicides (Remix / Grounded). The unique, specialist oil-based formulation is designed to reduce spray drift, evenly coat the soil surface and increase adsorption to soil particles. This results in improved crop safety and better weed control.

In the case of residual herbicides, having more droplets that reach the target is key. Tank mixing the residual herbicide with Remix and applying using a twin-cap combining a VPS0- 03 in the front with a Defy 03 in the back of cap (pointing forwards), with a spray volume of 200 I/ha travelling at 14.4kph enabled us to increase the number  of spray droplets and water volume, while maintaining  forward  speed. The level of black-grass control from a pre-emergence spray was increased from 14 to 52%, for example, and in a programme from 67 to 86%.

In 2009, we started evaluating a range of factors on fungicide performance, including forward speed and pressure, nozzle type and configuration, boom height and spray volume. Differences in fungicide application technique were greater than the differences between products, but combining the right products and right technique we could increase disease control and yield. A second area of innovation was the development of Velocity to improve fungicide performance.

In 24 trials conducted over seven seasons, a wide range of triazole / SDHI +f- strobilurin fungicides were applied at GS39 using air inclusion nozzles at 14.4kph in 100 1/ha spray volume, and the  addition of Velocity increased yield by an average of 0.45t/ha.

This is a higher value than the 0.25t/ ha long-term average observed in small plot trials applied via handheld boom, and demonstrates increased value of adjuvants as spray application aids when applied using standard farm spray techniques.

 

03 February 2017

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