FEATURE ARTICLES
Building a blueprint for better VRT
The key is developing a strong foundation of field and soil data, says Mike Bevans of AgTech Centre.
Posted: May 19, 2011
A tool is only as good as its operator's ability to use it.
There's a lot of truth to that in farming and it certainly applies in the case of new variable rate technology (VRT), says Mike Bevans, project engineer with the Alberta Agriculture and Rural Development (ARD) AgTech Centre in Lethbridge.
New VRT approaches have the potential to optimize nitrogen fertilizer application, seed placement and even herbicide application. That means more efficiency, along with the promise of cost savings and environmental benefits.
However, getting the most out of this technology requires having a depth of field-specific data required to make accurate prescription maps, which right now is lacking, says Bevans. Also, many producers are in the early stages of learning about VRT and haven't seen much data to give them a clear idea of best approaches and the potential economic benefits.
"A big part of the puzzle to get the most out of VRT is to have a thorough understanding of the land where you plan to use it," says Bevans. "That means getting down to the soil level and understanding all the factors involved, including responses under different environmental conditions."
To help address this need, ARD has established a major project, recently underway on a broad basis in Alberta Bevans plays a key role in the multi-level, multi-institutional project, which is headed by ARD agronomy research scientist Ross McKenzie.
"The big focus of this study is to look at what is happening on the ground under a wide variety of field conditions, with the idea of using this information to design methodologies for using VRT for fertilizer application," says Bevans.
The precision approach
More farmers are becoming familiar with the basics of VRT, which is a particular way of applying the core technology of precision farming to manage variability in fields. In practice, this is essentially a process of applying different rates of inputs to different areas of a field, with a goal to optimize those applications for benefits such as lower costs, better yields, environmental advantages and overall higher returns.
In practical terms, VRT is typically accomplished by developing a prescription map for a particular field, transferring the map information to a controller in the cab of the vehicle, and driving the field. The controller changes the application rate based on the prescription map, and records how much was applied where. Some more advanced VRT approaches can also be done on-the-fly, using sensors that measure what is needed by the crop and adjust the rate accordingly in real time.
Prescription maps often break fields into five to 10 management zones, based on soil tests, topography, aerial photos, previous yields and other factors, depending on the technology and information available. To help evaluate the effectiveness of VRT approaches and collect data for use in future years, yields are typically measured in each zone and a check strip, using combine yield monitoring and GPS systems.
Managing variability in fields
Indications are that precision farming and VRT are growing steadily in adoption for use in seeding and fertilizer placement. There is also potential to use VRT for spraying though there are hurdles to overcome for this option to become more viable. For all three options, many see VRT approaches gradually becoming more common.
"There's anecdotal evidence that VRT is working in the right situations," says Bevans. "However, it is a difficult area to evaluate because there's simply not a lot of information out there on the methodologies involved. Most producers who are doing this are working directly with companies and it seems that everyone is approaching it a little differently."
For example, some producers will base their approach solely off yield maps, while some will go off satellite imagery and some will go off soil sampling. "It may be that there's lots of different ways to get good results. But we haven't seen a lot of data to show the best approaches for different situations."
Records anchor success
More information and data is expected to gradually emerge, including through ongoing field studies by ARD and partners. In the meantime, Bevans advises a cautious, hands-on, eyes-open approach for farmers who are testing the waters.
Like in so many areas of farming today, one of the most critical things is to have good records - the more years and more detail they cover, the better, he says. "When you try a VRT approach, it's important to have the ability to compare what was done and the results from the period before the practice change to the period after the practice change. Records are the only way to do that. Otherwise, when you see a result such as higher yield, you don't know if it was due to VRT or some other factor. Good records also help you have a better prescription map that is likely to be more effective."
The producer needs to keep meticulous records of yields, inputs and a number of related key factors, to really be able to make a good decision, he says. "It's the only way to answer the question, 'Is VRT worth it for my field?' Don't simply take someone else's word for it. Keep the knowledge and the management decisions in your hands."
Rating VRT potential
How well will VRT work for different types of inputs? ARD AgTech Centre project engineer Mike Bevans offers a few observations.
Fertilizer application. This is where the majority of VRT applications and research is currently focused, says Bevans. "This is the most straightforward opportunity with VRT, but it's still at an early stage and there is lots of room for improvement in knowledge and methodology to get this to a more predictable, viable level."
Seeding. "There is good potential for seeding, but it makes sense to start first with a focus on fertilizer. Then once you figure out your fertilizer approach, you can add the seeding aspect. The reason is that playing with your seed affects your fertilizers. It's a question of, 'where do you start, where do you stop?' Seeding is likely second on the list.
Spraying. The specialized requirements of spraying make the precision pathway a difficult one to navigate, says Bevans. For one, there is the sheer size and speed issue: With many sprayer booms now in the 90 to 120 foot range and moving across the field at a rapid clip, the logistics of spraying at variable rates within a field are a formidable challenge. "This area is trickier but it has potential as well. Like with everything else, we need to keep building on what we know through research."
Equipment is improving the prospecting for VRT spraying approaches, he notes. Newer equipment allows farmers to use electronic guidance either automatically or manually to vary rates as they move across the field, either across the full boom or for different sections of the boom.
