Application at 200 l/ha for consistent grass weed control
Results of new grass weed herbicide application trials have confirmed the more consistent results with application at a water volume of 200 l/ha. Brixworth Farming's sprayer operator, Tim Cleaver, explains how they have refined farm practice to help cover the ground with timely applications in the autumn.
New 2018/19 application research at the Syngenta grass weed focus sites - at Barton in Cambridgeshire for black-grass and Doncaster in Yorkshire on ryegrass - has shown that increasing water volume, to 200 l/ha, can deliver consistently better grass weed control from pre-em applications, compared to treatment at 50 or 100 l/ha.
Syngenta application specialist, James Thomas, reported the trials have shown that whilst lower water volumes can perform well in ideal conditions and with a perfect seedbed, wherever situations are evenly marginally compromised by weather or seedbed, application at 200 l/ha will achieve more consistent results.
"In a difficult season, or where grass weeds are proving more problematic, there is a positive action to enhance control rates with application at 200 l/ha," he advised.
Overall, the trials have shown an average 10% enhancement in grass weed control at 200 l/ha, compared to 100 l/ha.
Compiling results from over three years of application trials, James has demonstrated that pre-em treatment at 50 l/ha resulted in far greater variability in the control rates achieved. Increasing the water volume significantly reduced the variability and assured higher rates of control in each instance. Results have been comparable with all application techniques and nozzle selection trialled.
"From our repeated work it is clear that application at 200 l/ha gives the optimum balance between achieving consistently high control rates and the practicality of application on farm scale," he advised.
There has been no real advantage seen in increasing water rates further to 400 l/ha, he added. New results from the 2019 season, investigating application at 150 l/ha had shown performance mid-way between 100 and 200 l/ha, James reported.
"That has given increased confidence that the 200 l/ha recommendation is the optimum, but that growers and agronomist can reliably select a water volume that works for their specific situation and season."
Growers putting results into practice
Black-grass is a primary driver in agronomic decisions of Ian Matts, Arable Director of Northamptonshire farming company, Brixworth Farming. With a real focus on achieving the best possible control across the farm’s 2500 hectares of arable cropping, he’s moved to applying all pre-emergence grass weed herbicides at an increased water volume, of 200 l/ha, and up to 250 litres on the most heavily infested fields.
For the company’s spray operations manager, Tim Cleaver (above), the pressure is having to make more tank fills over the course of the day – so minimising any downtime and improving turnaround is essential.
Having available water sources close to fields is the main factor in achieving the necessary high daily sprayer output, he advocates.
With extensive contract farming arrangements, covering a wide area, each block of land has its own water tank, typically with capacity for three sprayer fills (12,000 litre), which is supplemented by two 8000 litre and a 12,000 litre mobile water tanks where required.
“We fill up the sprayer in the morning at the yard, and take all the day’s chemical in a trailer towed behind the sprayer,” reported Tim.
“That means we can set up a convenient filling station by the water source, with everything to hand, without the need to travel back to the yard until the end of the day.”
Spray recommendations for most of the farm are made on Gatekeeper software, synched direct to Tim’s iPad. That gives a job total for all the day’s chemical requirement, which can be loaded ready onto the trailer the night before.
One useful advance to save time has been that Gatekeeper lists all the chemical in the order they need to be added into the tank, to reduce risk of any incompatibilities. If product is loaded onto the trailer in the same order as the filling schedule, it makes filling a few minutes quicker and avoids mistakes.
Furthermore, Tim’s iPad has a SIM card fitted, so if there are any changes or updates to the spray schedule during the day, they can be automatically amended whilst he’s on the move.
The iPad also holds all the farm maps, including stewardship areas that might impact on spraying operations, which saves time searching for information on paper. The large and complex number of stewardship initiatives operated by Brixworth Farming could compromise spraying output, but where well planned can take out awkward corners or features.
Tim's Top Tips for fast turnaround:
The other area where computer technology has helped to increase sprayer output is the automated field mapping and recording. Spending time pre-season to get everything installed and up to date, means just one press of the ‘Quick Start’ and its working – saving valuable minutes working through menus for each field.
“The system for most of the farm is virtually paperless – which is a lot cleaner and faster in the field,” reported Tim.
With accurate mapping, he can also now tweak the water volume to optimise output, so a 42 hectare field could be completed in two tanks at 190 l/ha, instead of needing to stop, fold, fill and return, for example.
He also uses the mapping to record any issues, such as black-grass patches, for example, which can be used to better target future agronomy decisions.
Although, with appropriate nozzle selection, the in field spraying time is no different between 100 and 200 l/ha, for the pre-emergence applications forward speed has been cut back to 12 km/hr to further improve consistent surface deposition. Whilst the slower speed does reduce sprayer output, the advantage is that boom stability is improved and is easier to maintain at the optimum 50 cm above the surface.
Tim calculates they now need 15 sprayer days to cover all the autumn pre-emergence herbicide work – but alongside that is the stubble and pre-drilling clean up sprays that need to be applied.
With two Bateman 36-meter, 4000 litre, sprayers available, they tend to dedicate one - which also has an Avadex applicator mounted - to the pre-emergence application. And its use can be extended by either of the farm’s operators doing an extra turn morning or evening.
With the timing crucial for pre-emergence applications, the second sprayer can be brought into action if the programme were in danger of falling behind.
“One of the key advantages of operating two sprayers, with each dedicated to a specific job, is that it saves doing so many time-consuming complete wash-out and tank cleans, compared to if having one big machine doing the different treatments,” he pointed out. Using the sprayer’s integrated clean water tank, most washing can be done in-field.
Tim’s Top Tips for field work
The Brixworth Farming pre-emergence application typically involves a stack of three or four actives, tailored to individual field black-grass pressure, but often with pendimethalin (Stomp Aqua), prosulfocarb (Defy) and flufenacet + diflufenican (Liberator). Glyphosate might also be included if seedbeds have greened up with weeds before the pre-em application.
“Small cans are a killer for speed of turnaround and sprayer output,” according to Tim. “The 10 or 20 litre cans empty much faster and smoother – with fewer lids to open and less containers to wash, which all takes time."
Getting rid of fiddly foil seals saves time, and minimises the risk of contaminated waste. Cans are washed on the sprayer induction hopper and drained on the integrated lid.
With an average field size of 10 - 12 ha in some blocks, repeated folding of booms to move between fields can take an inordinate amount of time. However, within blocks of land, hedge gaps of at least 12 meters have been created to allow combine movement without taking off the header, and are trimmed so that Tim can use the gaps by just folding in the end boom sections – which is much quicker than a complete fold of the final sections.
Tim also highlighted the importance of knowing the aspect of different fields and the specific effect of wind direction. On all but extreme days it is usually possible to find some sheltered fields to keep working.
But with some fields that are almost always windy, prioritising the most exposed areas and getting them treated when conditions are good is essential, he advises.
Recently the sprayers have been equipped with anemometers to measure wind speed. One of the findings is that, at 50 cm boom height, the wind is significantly lower than the weather forecast measured records – conventionally taken at ten meters – or looking for visual indication of wind speed in tree tops, which are far higher. Physically measuring speed at boom height means there are actually more spray days available than hitherto assumed.
In optimum spraying conditions, the farm’s set-up for pre-emergence application has been a twin-cap bayonet fitted with an 03 flat fan in the front – effectively facing forward - and a 3D Nozzle in the rear, angled to give a vertical downward spray.
However, this season they have also been evaluating Teejet TTI 90% Drift Reduction Nozzles for pre-emergence applications at 200 l/ha, with the potential to reduce drift and give a more consistent spray pattern across the boom, with greater flexibility from a 3* LERAP rating.
“There’s always pressure to get the pre-emergence sprays on at the optimum timing. And that’s greater with the move to 200 l/ha when sprayer capacity has been stretched,” Tim reported.
“But getting the process as efficient as possible we did get around. And there’s always little things we learn, to get better and faster.”