Soil Mapping: has electrical conductivity technology's time finally come?
Saturday, August 8, 2015
Interest is rising across the province in EC technology, particularly on farms with varying soil types. But it is expensive – $25 to $45 an acre or more and potential users are weighing the alternatives carefully
by DON STONEMAN
Over a decade ago, Mike Strang hired a soil-testing lab Agri-Food Laboratories in Guelph to soil-map more than 1,000 acres of land his family farms near Exeter, using electrical conductivity (EC) technology.
Not many people knew about EC soil mapping then, says Strang, who gave a talk on it at the time at an agricultural technology conference in Ridgetown. The technology "never really took off. Now it's coming back again."
Interest is indeed growing across the province as crop consultants look to invest in better ways of improving yields and reducing fertilizer costs for their customers. In eastern Ontario, Pioneer Hi-Bred agronomist Paul Hermans is using a device made by Veris Technologies for a second year at farm locations near Chesterville, Vernon and Kars. His ultimate goal is to develop variable-rate nitrogen programs.
In western Ontario, Premier Equipment, a John Deere dealership based in Elmira, is mapping soil using a Trimble product called Soil Information System (SIS).
At Tavistock, certified crop advisor Paul Raymer, Practical Precision Inc., is manufacturing and using a European-developed device and offers a program called SoilOptix that produces similar soil profiles in a different way than either of the above, measuring radiation emitted naturally during "soil decay" rather than electrical conductivity. Raymer has soil-mapped 3,000 acres in the two previous years. Dave Hooker, an assistant professor and field crop agronomist at Ridgetown College, is evaluating the device.
What is soil mapping? The process involves systematically mapping a field using technology to determine the profile and attributes of the soil near the surface or several feet underground. It is a different way of developing management zones for crop growing that may substitute for, or supplement, yield maps and also augment conventional soil tests. It gives large-scale crop farmers in Ontario, where farms may have highly variable soils, the advantages formerly reserved for smaller operators who knew their fields intimately.
Whether it is through using devices that provide soil profiles or via unmanned aircraft that look at crop growth patterns, "you are trying to best represent or capture the variability throughout your field," says Jack Legg, agronomist and branch manager for SGS's Guelph office. (SGS acquired Agri-Food Laboratories in Guelph nearly 10 years ago.) Field maps allow crop consultants and farmers to develop management zones. Once zones are identified, farmers can apply variable-rate fertilizers, variable rate nitrogen, "or even target areas with manure that need organic matter."
GPS systems allow farmers to do variable-rate seeding, plant a different variety for eroded knolls or a drought-resistant variety for sand, or even seed variable species. "It really opens a lot of opportunities," Legg says.
An EC soil map has a long-term value: proponents say the soil profiles of fields they develop are stable for seven to 10 years. The substantial cost of mapping, ranging from $25 to $45 per acre and upward for high resolution mapping, can be hard to stomach, but proponents argue it can be profitably amortized over time.
Certified crop advisors such as Huron County-based independent agronomist Mervyn Erb and Aaron Breimer of Southwest Ag are watching closely to determine which technology to invest in to serve their customers. Why is there a market now for a service that barely existed a few years ago? It's all about crop returns.
SGS's Legg explains that innovative-minded farmers were interested in using EM38 and Veris mapping of management zones (the two choices available then) prior to 2003 because crop returns were good. But variable-rate fertilizer application was in an early stage, GPS equipment for farming was expensive, topography mapping even more so, and demand for mapping went away in the mid-2000s when corn returns fell to below $3 a bushel and farmers economized.
Legg adds that interest was renewed when corn prices were high and farmers and crop consultants already owned relatively inexpensive Real Time Kinematic (RTK) GPS technology, which measured vertical dimensions of field topography economically. In the current crop price downturn, farmers see value in spending on technology to reduce future costs.
"The price of corn has come down, but we are almost in a world where we have to manage every dollar to maximize our margins with whatever technology we can utilize," Legg says.
Electromagnetic beam
Back in the day, Agrifood Laboratories dragged an EM38 device across fields behind a GPS-equipped ATV to categorize zones for variable rate fertilizer applications – in particular, nitrogen. An EM38 machine sends an electromagnetic beam into the ground and then captures and stores the returning signal on a computer on the ATV. That signal, when it is interpreted, reveals soil characteristics such as soil texture – the amount of sand, clay and loam – as well as organic matter, which reveals water-holding capacity, The resulting map helped Mike Strang to make nitrogen application decisions.
"It worked really, really well in fields with large variations in soil type," Strang recalls. He cites a particular field that has good clay loam at the front of the farm, "beach sand at the back, and all variations in between." The EM38 "would map out those soil zones exceptionally well and I still use the maps from those fields." But it didn't always work well.
One field had little variation in soil type, but a lot of changes in topography. The maps would point to low yield potential on eroded knolls and signal the applicator to reduce the fertilizer applications there. But it failed to signal when to increase fertilizer later when the management zone should have changed to indicate a more fertile part of the field. As a result, says Strang, the crop growing in those areas would be nitrogen-deficient at the end of the season.
Legg allows that customers like Strang found that low areas on the farm were quite different in nitrogen requirements than the higher areas.
Strang is now one of the customers of Tavistock-based Practical Precision Inc., which manufactures SoilOptix, a high resolution top soil mapping system, and uses it to develop management zones in farmer clients' fields.
Practical Precision owner Paul Raymer calls his SoilOptix system "an MRI for your soil." Raymer says he mapped about 3,000 acres in Ontario in 2013 and 2014 in 40-foot-wide swaths and collected 335 data points per acre. "There is a lot of meat there to create management zones." Results were being evaluated over the winter by Ridgetown's Dave Hooker, who would not comment on the device's effectiveness for this story.
SoilOptix emits no signal as it is pulled across a field. Instead, it measures the naturally-occurring radiation emitted as soil particles decay. "The strength of this tool is identifying texture, clay content and sand content," Raymer says. "The real low-hanging fruit to make this stuff pay is variable-rate seeding. We did some for corn last year." However, identification of pH levels across fields and where to spread lime is another benefit.
Raymer looks at the coverage maps and picks out areas to strategically soil sample. "We run (survey data) through some fancy computational software… and output high resolution property maps from a fertility standpoint and also from texture." He calls it "foundational data" that can be taken into management zones. He charges $35 an acre for average-sized fields. Raymer argues it amounts to about $7-$8 per acre annually, since the profile that is developed will aid in crop production for more than five years.
Drone considered
Huron County crop consultant Mervyn Erb is torn between the EM38 and the SoilOptix system when considering buying devices to scan customers' fields.
Last winter, he was going to buy a drone (UAV) to inspect crops and diagnose problems. But, after talking with other crop consultants at their annual association meeting in early winter, he felt discouraged by the prospect of trying to get paid for photographing fields – customers often don't see value in the information gathered by drones taking photos from overhead. So Erb set aside $30,000 for a soil sensor system instead. The question he faced is which one?
Months later, and faced with a number of choices, Erb still hadn't made up his mind. "I am weighing it all in the balance and fence-sitting for now," he wrote in an email.
Like Erb, Aaron Breimer, Veritas Lead for Southwest Ag, is evaluating what system works best and also if he can "monetize" the service that the program provides to farmer-customers. He thinks there are more questions than answers. He isn't ruling out drones or other aerial evaluation systems.
EC field mapping is expensive, Breimer observes. Costs range from $25 an acre to $45 and more if higher resolution images are requested. "Can you really make management decisions that will allow you to capture that cost? I am not 100 per cent sold on it yet."
Breimer thinks the easiest return is for anything to do with lime applications, and maybe dealing with excessive magnesium in soils. The next target is variable-rate planting "and that is where we play around." Then there is variable-rate fertilizer, excluding nitrogen, but this is a challenge because "not all nutrients are going to be made available the first year and not all of the plants are going to need them the first year. It becomes a multi-year tracking process to see if it is the right decision. In my very humble opinion, the highest fruit on that tree is variable rate nitrogen, but that is also the one that gets the most interest."
Breimer has had some success creating zones in less expensive ways. The best method, he feels, may be using historical yield data, but not all farmers have that available for their fields.
"I tell farmers the most important data layer we work with is the one between their ears," Breimer says. "It's their experience as a farmer."
Farmers know where good things happen in their fields, Breimer says. "But they may not know why something is going on," and that's where new technology fits in.
"If a farmer has a clay field and a sand field, he treats them differently. Now we have the technology to be able to treat the clay parts and the sand parts in the same field differently. The challenge becomes how we identify which parts are clay and which parts are sand."
The oldest and mostly widely used of these mapping devices is manufactured by Veris Technologies of Salina, Kan. The Veris measures soil electrical conductivity to map soil characteristics within a field, determining texture (amounts of clay and sand), organic matter and also pH. The Veris is a so-called "contact" method of mapping, because an electromagnetic current passes between coulters in the soil pulled behind a tractor. Readings are stored in a computer on the tractor. According to documentation provided by Pioneer, which is adopting this technology for its agronomists, contact and non-contact methods are "said to have comparable results."
Readings affected
Marketers of other competitors' products say Veris isn't good in wet soils because moisture affects the readings. "Moisture affects our readings and everyone else's," says Eric Lund, president of Veris Technologies. "The absolute readings will change. What makes EC valid is that the zones don't change and that has been well documented. We mapped one field in Illinois seven times. The numbers change, but the zones don't."
The Veris is the device of choice for a Pioneer Hi-Bred program to boost yields (see story page 23). But not everyone likes the Veris. SGS/Agri-Food Technologies chose the EM38 because it was non-contact – it wouldn't interfere with no-till customers' field plans – and it was easy to tow behind a low-powered ATV.
Mike Catalano, senior technical sales associate for North America at Geonics Limited in Mississauga, explains that agriculture is only one of many applications for the EM38. Police forces use it to search for graves; it is also used in archaeology and in mining. While the technologically has existed for 30 years, it wasn't used extensively in precision agriculture until about 10 years ago.
Scanning agricultural fields is "seriously expensive," Catalano says. Still, he says "millions of dollars can be saved" if farmers don't apply fertilizer where it isn't going be effective anyway.
When the EM38 is scanning farm fields, a typical swath might be 50-to-100 feet wide. It is pulled on a sled several metres behind a tractor or an ATV and the device sends and receives an electromagnetic pulse into the soil. The signal that is collected is stored on a computer on the towing vehicle, either via a cable or a Bluetooth wireless connection.
The information collected on a scan means "different things for different farmers in different parts of the country," Catalano says. He says Geonics recently sold a dozen devices to a corporation in Bose, Idaho, which grows potatoes for McDonalds Corporation.
Back at Guelph, Legg is considering reinvesting in another EM38, though he hasn't given up on photo imagery from satellites and UAVs capturing subtle differences across fields.
With a drone, you have the potential to use it every year and multiple times per year. "I think the marketplace (for a UAV) is about $5 an acre per visit," he says.
Legg stresses that this technology won't pay off when used on a farm with uniform soils. Its value is on farms where soils are variable. Whatever is offered to farmers "has to be economical, it has to have returns and it has to be practical."
Legg warns there is a risk of information overload. "I wouldn't want to see people jump in two feet first, get overwhelmed and then think it doesn't work." The winter is a good time to work on this and make management decisions, Legg says. BF
Pioneer hi-bred takes another direction
Variable rate nitrogen might be the toughest target to achieve as far as Veritas' Breimer is concerned, but it's a key target for DuPont Pioneer. Agronomist Paul Hermans, based in Richmond, near Ottawa, worked with a Veris machine in eastern Ontario in 2014 and planned to do more testing in 2015. Using the Veris machine "opens your eyes to soil variability in the field and also pH differences," Hermans says. In one pass, the machine tests for soil variability, organic matter and pH across the field.
Hermans is working with the Veris and Pioneer's Circa yield program, a nitrogen determination model that takes soil texture differences, nitrogen differences and combines them with a local weather station. "You can start to see where water ponds, where you get more denitrification and leaching, and come up with a model to predict where nitrogen is in the soil," Hermans says. When a grower side-dresses a corn crop, the program predicts how much N is there and gives a grower a variable-rate prescription to change N applications "on the go" throughout the field.
This is being tested in eastern Ontario on three sites in the Kars, Chesterville and Vernon areas on variable soils. As well as the coulters, the Veris Hermans uses has an optical eye that detects and measures organic matter content.
Hermans says the Veris produces a map with soil textures, another map with organic matter and detects pH as well. A map of the fields shows all of the differences. "If those zones were in different fields, you would farm them differently," Hermans says. With variable-rate technology, a farmer can do that on the fly.
Using variable-rate seeding and fertilizer, "we can help the grower either to reduce input costs and (improve) economics or put in more inputs and get higher yields." BF
Premier's SIS system ‘quite different' from other approaches
Premier Equipment in Elmira has the only SIS (Soil Information System) in Canada to date, says Greg Kitching, integrated solutions consultant. The system, offered by Trimble (which purchased the assets of Wisconsin-based maker C3 in late 2013) involves a Dual EM machine which, surprisingly, is manufactured in Milton, Ont.
Surveying fields with SIS is a three step process, Kitching says. The field is initially surveyed with the Dual EM machine, and a highly accurate Real Time Kinematic (RTK) GPS. That process is called surfing. The software analyzes results and establishes very targeted locations to sample with a mechanical probe that goes four feet below the surface. The probe measures tip pressure, sleeve pressure, electrical resistance and volumetric moisture. Once that data is analyzed, it determines whether to go back and pull soil sample cores four feet deep which are sent off to a soil lab for a standard analysis.
"The EM machine is used as an assessment tool to identify variability within the field and then it lets you go out and run another two processes that actually generate the report," Kitching says. "It is just an initial step. There is a lot of work goes on after that."
This is not a substitute for 15 years of yield maps, says marketing manager Ryan Hicks at Premier. Fifteen years of yield maps represent opportunities across the landscape. This technology will identify what the opportunities are, Hicks claims.
Kitching says that it is "quite different from some other approaches" where they build recommendations based on output from the original sensor. Premier took delivery of the machines last fall and tested a few hundred acres. Kitching would not disclose the cost of the machine, noting only that "it is a considerable investment."
He describes SIS as a "unique approach" which provides not only topography and physical soil texture but also hydrology and assesses compaction as well as all of the chemical parameters of soil. The report for each site is 60 pages long. "I have never come across anything so comprehensive."
Working with consultants is important, stresses Kitching, who is a certified crop advisor. "There are quite a few scenarios for use of this information." The idea is to "build relationships with CCAs and other industry people to actually deliver and interpret results. That is critical. The last thing we need is another book of maps on the shelf."
It can be used to help build irrigation systems or drainage systems. Last fall, there was a lot of interest in compaction. Kitching says SIS builds a "depth of root restriction map" to determine where compaction needs to be dealt with via crops or mechanically.
The typical row crop situation is a 10 metres resolution, for horticulture a five metre resolution. For viniculture or research, it is two metres, which gives a very high resolution value to maps.
A Trimble press release says "By analyzing soil variability and patterns prior to sampling – and by using its industry-exclusive data acquisition and analysis software – SIS provides targeted recommendations on the best locations where soil samples should be taken.
"In some cases this reduces the number of samples required to provide high-quality information by as much as 60 per cent.
"The solution enables agronomists and other trusted advisors to be more efficient with in-field data collection, providing valuable time and operating cost savings." BF