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Expanding vision with infrared technology

Blain Hope Published on 30 September 2013
Irrigation problems on pivots

Infrared imaging is one of the trending technologies of crop production.

Blain Hope of AgSpecific has been using this technology for the past four years to help producers identify crop issues that might affect yield loss.

Progressive Forage Grower editor Lynn Jaynes recently asked Hope to explain the process.

Q. We’re hearing a lot about the use of drones with infrared photography and crop production. Can you explain what infrared rays have to do with crop production?

Hope: It’s kind of like x-rays. If your kid hurts his arm, you go and have it x-rayed to see if it’s broken or not because that’s not something you can see with your eyes. X-rays can’t be seen with the naked eye, but we can take pictures using those rays and get more detail.

Infrared technology works on the same premise. When we take these near-infrared pictures of fields, it’ll show us stress spots before we can see it with our eyes. And doing it weekly allows us to see anything occurring or changing in the field. That’s the simple explanation.

When light is reflected on the leaf of a plant, there are four lights that hit – red, green, blue and near-infrared. The red and blue are absorbed by the leaf, and the green and near-infrared are reflected.

The plant looks green because it’s reflecting the green light – but we can’t see the infrared. So we take pictures with an infrared camera to capture the reflection of the infrared rays, which allows us to see what is happening.

Chlorophyll is absorbed in the red and blue lights, so anything that affects the absorption of that light is not getting proper nutrients. As a plant starts to become unhealthy, it starts reflecting blue and red and absorbing the green and the infrared.

I do a mathematical calculation on every pixel of the picture to tell how much infrared is being reflected or absorbed. Then we turn it into colors that we can recognize and can use to map the field.

The dark green areas are the healthiest plants, then we scale it out to tans and whites to indicate less healthy or stressed plants. The coloring is comparative on a max-min scale for that picture.

Q. What will the infrared photo not reveal?

Hope: The near-infrared images tell you where the problems are but not what the problems are. For example, it won’t tell you whether the stressed area is specifically caused by disease or pest. However, the patterns it shows are very revealing – as is generally the case with irrigation problems.

Q. What is your process for assessing problems in fields?

Hope: We start the last week of May in our area, where most crops are just coming up and there isn’t much foliage yet. This allows us to see the wet ground and irrigation patterns and problems.

I don’t use drones, but I hire a pilot once a week to fly over the contracted fields to take near-infrared pictures. Then I go through the pictures and orient the field north, size it, then analyze it.

I put the images on a cloud server where the farmer can get them and send the farmer an email with my assessment of the problems in each field.

Q. If a light-colored area in a photo shows stressed plants, how do you determine what the cause of the stress is?

Hope: With irrigation stress, we can see patterns. On a pivot field we’ll see a ring or “spoking.” A stress spot that shows up in just one quadrant or an isolated area of a field might be anything – like poor soil or a rock outcropping.

But if you’ve got a ring going all the way around, then you probably have a sprinkler head that’s not working right. If the stress is bugs, diseases or fertility, then it’s a different type pattern, not as symmetrical, and that will usually take some further investigation on the ground to determine the cause.

Field spoking

Q. So an irrigation problem would show up as a complete circle under a pivot system?

Hope: Sometimes it might not go all the way around because you might have an area that’s handling that amount of water OK, and the rest is not.

But generally, they go all the way around. Another thing we sometimes see is “spoking” in the pivot, which indicates it isn’t moving evenly.

We can get wind spoking, but that would just be in one spot of the field.

But when there’s spoking all the way around the pivot, that tells me there’s something wrong with the pivot. But once that’s identified, the farmer can work on the problem.

Q. How do producers typically react to seeing these pictures?

Hope: It’s tough for anyone to admit there’s a problem and commit to addressing the problem when, to the natural eye, the field looks perfectly normal.

I took some pictures showing plant stress to a potato farmer last year, but he didn’t believe there was a problem. To his eye, the field looked to be in good shape.

So when he harvested, I went out there and got in the tractor with him with my GPS and a map of the field to track the rings identified in the infrared images.

As we went through the field and crossed those rings, he could visibly see that the potatoes were smaller and there were less of them. It made a believer out of him.

On the other hand, I had a farmer with some odd trails through his field, and when I showed him the infrared pictures, he immediately knew what had caused them.

Apparently, they spread compost in the spring and had created some “roads” into the field with the manure spreaders (see bottom left picture). So what we were seeing in the images was compaction.

And when we later walked the field, we could see the corn was thinner and shorter in those areas. What was interesting about it, though, was that we went through a winter of freezing and thawing, and even plowing, but the next spring when I sent the farmer images of the field, he called me and said I’d sent him last year’s picture.

But I hadn’t. Even after plowing, freezing and thawing, the compaction from the spreaders was still showing up. It wasn’t as severe, but it was still there, and the farmer’s response was, “I’ll never do that again.”

Q. Who do you find is most open to using this technology?

Hope: The majority of my customers are in their late 40s, 50s or 60s. The younger guys have more of an interest in technology, but the ones that I’ve dealt with who have been successful are the very progressive farmers who want to find help to do a better job.

Q. Why wouldn’t someone just buy his own drone and an infrared camera to take the pictures themselves?

HOPE: Right now, the ones available would mean you’d have to drive to each field, put the drone in the air and set up the computer to fly a certain pattern.

And you’d have enough battery to fly one, maybe two fields. So the economics and time factor involved in driving to each field, timing it so that you have bright sunlight (in order for the infrared to reflect), setting up the fly pattern and doing it consistently are problematic. And you haven’t even started the data processing yet.

Compaction caused by tractor passes
Q. What challenges does this present?

Hope: A farmer is busy: He’s stressed, he can’t be everywhere, and I’m able to show him where the problems are that he didn’t know existed.

Yes, it’s an opportunity to learn a lot and increase yields, but the farmer has to be willing to recognize there’s a problem and then be willing to do something about it.

Sometimes it is a little overwhelming, but you have to realize problems take time to work out, particularly if they have been there a while.

I have a farmer with irrigation problems he did not know about, but he doesn’t get upset, he admits the issues and commits to keep working on them.

Last winter, we sat down at the end of the year and went through all the images again, and he picked out the pivots that he wanted to repackage (replace nozzles), so he learns from it and works on it.

You have to be willing to work at it like that. Another thing is to keep monitoring those irrigation systems with near-infrared and making adjustments as soon as problems start so they are quickly fixed and don’t cause a loss in profit.  FG

TOP: Irrigation problems on pivots show up as light-colored rings, indicating malfunctioning sprinkler heads.

MIDDLE: “Spoking” in an image can indicate a pivot isn’t moving evenly through the field.

BOTTOM: Compaction caused by tractor passes can show up for two-plus years in a field. Studies estimate yield loss of 25 percent with only two equipment trips across the field. Photos courtesy of Blain Hope.