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Precision variability in agriculture

For precision ag, the headline grabber is nitrogen. But how exactly the technology will improve N efficiency is still up in the air

When it comes to precision agriculture on the Prairies, all eyes are on nitrogen efficiency. It makes sense, after all. Nitrogen is an expensive input that seems to all too conveniently track the price of grain, at least on an upward trajectory. And after grain prices fall, nitrogen prices seem mysteriously to be a bit more sticky.

It’s enough to make farmers dream of a future when they’ll be able to limt their exposure to this major production cost by supplying their crops with exactly the right amount and source of nitrogen at exactly the right time and place.

But this is going to be tricky throughout the West, says Jeff Schoenau, a respected soil scientist with the University of Saskatchewan who believes it all comes down to variability.

“I do think our challenge with precision agriculture is a bit greater than other areas,” says Schoenau, who’s often called a farmer-scholar with a practical bent. “It all comes down to our variability, mainly in the weather. What you’re trying to do is predict the crop’s demand for nitrogen and other nutrients, and unless you’ve got a crystal ball, that’s pretty tough to do.”

Homemade solutions

Schoenau says that doesn’t mean growers should drop the idea, but it does mean they’re going to have to accept that achieving what they’re talking about is going to take a lot of experimentation and adaptation to come up with a made-at-home solution.

“We’re not even talking about a made-on-the-Prairies solution,” Shoenau says. “We’re talking about systems that work at the individual farm level.”

It’s a simple concept that involves balancing out nitrogen applications because total N requirements are going to be different in different parts of the field.

Like most simple concepts, however, the practical application in the field gets quite complex quite quickly. One of the biggest challenges is how to identify these zones that might be a candidate for different management treatments and doing so without being overly cumbersome, Schoenau says.

“You’re really trying to take the random variability that occurs in a field and convert it to systematic variability that you can manage differently,” Schoenau says.

That suggests the most basic precision agriculture tool most farmers have — GPS-linked yield maps from combines — are ironically too imprecise taken alone. That’s because of the year-to-year variability Prairie farmers know all too well. It can skew these maps dramatically from season to season, and conditions are never the same, so essentially growers find themselves applying nitrogen to last year’s growing conditions.

“You can take several years of these maps and put them together and get a bit better picture, but even that’s not a particularly clear picture,” Schoenau says.

A better approach is to begin pulling information together from a diversity of sources, including yield maps. For example, there could be readily available satellite imagery for most of your fields that will give a visual depiction of where different growing zones might exist. There are soil maps, including a frequently overlooked resource of RM assessment maps done in the 1960s.

“Some of these have a surprising amount of soil detail,” Schoenau says.

Even old aerial photography might hold some clues with, for instance, visually different soils showing up on a summer-fallow field. Yet it’s not going to be an easy thing to pull together, Schoenau admits.

“Any way you slice it, there’s going to be some work, some cost and some hassle,” Schoenau says.

But once this information has been pulled together, that’s when things start to get interesting, since you can begin using mapping systems to pull all this information together to produce a map that begins to generate a real and complex understanding of your field.

“The people who do this kind of work talk about layering information, and I do think that’s the right approach,” Schoenau says.

Schoenau also stresses that growers toying with the idea of integrating precision agriculture into their operations are also going to have to look well beyond nitrogen to include other potential limiting factors. For example there are likely areas on every farm that are highly deficient in other things, such as micronutrients. Here a farmer might earn a few extra bushels and dollars by making straight-up spot applications. Other areas might be ruled out entirely because they have other major challenges.

“You might have a portion of a field where salinity is your major limiting production factor, and what you do with fertility will have no effect,” Schoenau says.

Getting started

However, just because the map is made, that doesn’t mean the challenge of precision agriculture is put to rest.

“It will help you do things like identify areas that are lower yielding and might benefit from a different treatment,” Schoenau says. “It’s a good starting point for what you might look at — but it’s the starting point.”

There’s likely going to be a learning curve and developmental period as growers get their heads around the concept of precision agriculture and how it might fit on their farms. And while lower grain prices certainly aren’t welcome, they will provide an incentive to growers to begin to ponder some of these questions, Schoenau says.

“As we’ve gone through a period of high crop prices, there was a bit of a temptation to pour on the fertilizer,” Schoenau says. “Now that prices are flat and aren’t as high as before, and producers are feeling the squeeze, I think they’re going to look a bit more carefully at how they allocate their inputs.”

One central challenge is going to be to design a system that works here, under our unique production conditions and challenges. For example, we have more weather variability than other production areas, which accentuates the variability in our soils and the relative low value of the crops we grow. It means some of the solutions that work elsewhere, such as variable-rate applications, aren’t necessarily such clear-cut winners here on the Prairies.

“The economic benefits of variable-rate applications can be hard to realize in Western Canada,” Schoenau says. “A number of people have looked at this question in their research, and they really aren’t that clear-cut.”

That doesn’t mean these benefits won’t be developed and emerge over time, just that we’re really in the infancy of discovering a precision agriculture system that works for Prairie conditions. Farms here are operating in a challenging, highly variable and weather-dependent system with moisture and temperatures that can swing wildly, all while growing unirrigated, lower-value small grains. These are unique systems that demand unique solutions.

One idea that some agronomists have been kicking around, especially in the U.S. where it’s a perennial conference topic, is combining applications of regular nitrogen with targeted applications of slow-release nitrogen, says a Manitoba soil scientist. John Heard, who works with the provincial Agriculture Ministry, says the concept is worth considering.

“There are some very interesting and compelling reasons to combine the two,” Heard says.

A farmer who has a few seasons’ experience on any given piece of ground will intuitively figure out the areas where nitrogen loss is more likely. For example, there could be eroded knolls where leaching is a serious risk. There can also be low spots that encourage denitrification and off-gassing.

One way to approach that might be to simply target a higher proportion of the nitrogen allocated to that field to these areas and hope this offsets any losses. However, this isn’t doing anything to address the underlying problem of nitrogen losses, though it may lessen or eliminate yield losses from the areas.

A better strategy might be taking the higher-priced slow-release products and applying them to these areas, to address both underlying issues.

“You might ask where the economic incentive is to go to this trouble, and the answer is it’s provided by the fertilizer manufacturers who tend to charge more for these products than just basic nitrogen,” Heard says.

Of course it’s one of those things that comes with its own challenges attached, Heard concedes. For example there’s the need to purchase and manage yet another input, as well as limitations of existing equipment, where bins and air tanks are already full up.

“It certainly can be a logistical challenge,” Heard says. “It’s yet another thing to manage in the field.”

There are some strategies that can help, however. For example, fall applications of nitrogen, if seasonal conditions permit, can ease the congestion in the spring. Done late enough in the season, the region’s frozen soils can also contribute to locking up the nitrogen until the spring thaw, then the slow-release nature of the product takes over from there, releasing it through the growing season. The rest of the field can then be treated as normal, with conventional nitrogen.

A sizable challenge

One under-the-radar challenge to precision agriculture might be the size of farms.

Heard says it’s inescapable that operations are getting larger and larger and more and more hired labour is doing the field work. Somehow the knowledge that exists within the mind of the experienced farmer who knows the land has to be transferred to the employees out in the field.

“This is where we may need the tool of technology,” Heard says. “It’s through things like maps and management zones that we can put these strategies to work on farms with more hired labour and perhaps more acres to cover.”

This is why Heard suggests the best strategy may be a combination of methods that includes both nitrogen source and high-tech mapping and variable-rate technology, though he stresses this is going to be a long-term project that relies heavily on the inventiveness and ingenuity of growers.

“It’s fine for someone like me to have a bright idea, but ultimately it’s the farmer who’s going to make the decisions and is going to figure out how to make it work,” Heard says.

“Now that crop prices have fallen, and fertilizer prices not so much, we may see more attention being paid to making nitrogen use more efficient.”

In particular, he’s expecting solutions to emerge that are centred around leveraging existing equipment and agronomic knowledge. It all comes down to farmers seeking to give themselves better economic control of their operations, Heard says. “They’re going to be asking themselves, ‘What can I do, by myself, with the equipment I already have?’”

During times like these a common question coming from farmers is how to reduce N use without taking a huge hit. They’re seeking the sweet spot of lower production costs without a serious yield hit, but Heard stresses that a short question doesn’t always lead to an equally short and sweet answer.

“There are a lot of different options and I suspect we will see the full spectrum being used,” Heard says. “There is no single right answer.”

Despite all these challenges, Schoenau isn’t telling Prairie farmers to give up on the precision agriculture goal, but rather he’s reminding them that any major evolution of the production system comes with a steep learning curve.

“The variable-rate technology and the engineering behind it — that’s there already,” Schoenau says. “What isn’t there yet is the knowledge. That’s our major challenge.”

For growers looking to dabble in the system, he recommends picking a field and breaking it down into a few different production zones. Then begin to manage them just a bit differently, accumulating experience and knowledge as you go along. He also strongly urges growers to find and layer as much information as possible over that field.

Says Schoenau: “This is really a situation where knowledge is power.”

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