THE Grains Research and Development Corporation (GRDC) is urging growers to choose nozzles for their band, boom or shielded sprayers that offer versatility and can deliver the correct amount of spray to the target.
Versatility is important, particularly where paddock conditions cause a variation in speed and pressure required, according to spray application consultant, Bill Gordon.
“The nozzle is perhaps the most important part of the whole sprayer, so it is worth spending time on selecting nozzles that can be used in more than one situation,” Mr Gordon said.
He said nozzle operating pressure was very important and each type of nozzle must be run at the most appropriate pressure for its type.
Mr Gordon warned that dropping below the minimum suggested pressure can result in poor control due to changes in fan angle and droplet size which can cause a loss of efficacy in broadacre applications.
“Selecting the most appropriate nozzle size and type, and using rate controller functions such as the minimum hold for pressure, speed or volume can help to reduce these problems,” Mr Gordon said.
“However, if the minimum hold function is set and you travel at lower speeds where it engages to maintain pressure at the nozzle, you will be overdosing those areas.
“If the minimum hold engages too often, this ultimately costs the grower more, and with some products such as in-crop herbicide or pre-emergent applications, it may damage crops or create plant back problems.”
He also advised that in some cases it may be better to increase the application volumes slightly to allow for a faster speed.
Mr Gordon said factors within each paddock including slope and variation in soil type, soil moisture and crop density can result in big variations in speed.
“The trick for operators is to select nozzles that will provide the biggest speed range while maintaining the desired spray quality.”
Help in selecting the right kinds of nozzles is available with the GRDC The Back Pocket Guide: Nozzle selection for boom, band and shielded spraying, written by Mr Gordon and fellow spraying expert, Graham Betts of ASK GB.
The guide includes a table outlining the features of eight main kinds of nozzle available: pre-orifice, low-pressure and high-pressure air induction, extended range flat fans, twin jet and hybrid, fence line and streaming nozzles.
“Before purchasing a set of nozzles, ask what else you can do with the nozzles — well-chosen nozzles should do more than one job, but not necessarily all jobs,” Mr Gordon said.
“Most growers need at least two sets of nozzles — that might be one for fallow and pre-emergent use and one for in-crop applications — and they can often get help on what’s best for their situation from agronomists, resellers or machinery dealers as well as narrowing down some of their options by using tools like The Back Pocket Guide.”
The guide contains some handy tables and formulas so growers can calculate their application rates and adjust the settings in their rate controllers to help ensure they get the best results possible with each spray and with suitable nozzles.
“With banded and shielded spraying becoming more popular, growers may need to use formulas to calculate the application rates, or to select the most appropriate nozzle size and pressure, as most nozzle charts only cover 50cm sprayed widths, and shields and bands rarely match this,” Mr Gordon said.
Whether boom, band or shielded spraying, he said determining the application volume and spray quality from your nozzles was critical to ensure growers get the most from spray units.
The guide contains step-by-step instructions about how to select appropriate nozzles for booms using manufacturers’ spray charts or by calculation for different set-ups, as well as some simple checks to ensure the sprayer is operating efficiently.
To download the Back Pocket Guide, click here
