Q&A: Why You Should Check Your Imagery Before Your Harvest

Written by Dr. Tracy Blackmer
August 10, 2017

By the time your yield map comes in this year, it may be too late to investigate the root cause of problem areas. While yield maps help you identify differences in yield, the combine leaves little evidence to investigate why. Satellite imagery, on the other hand, can point you to potential problems while you still have time to investigate and identify the cause.

In my last webinar, I discussed how to identify potential problems, and what to look for in your imagery that might justify a pre-harvest investigation. You can read the questions from the webinar below, or watch the full recording here »


Q: Can you use satellite imagery to monitor things like beans, wheat, oats, cotton, or sorghum?

A: Yes. Satellite imagery can be used for more than monitoring just corn. For soybeans, you can see herbicide overlap, as well as weed pressure. The same principles hold true for different crops. 

It's important to have the right timing when we check satellite imagery. We need to ask if we're checking imagery at the right time for the right crops.

For example, satellite imagery for wheat is best monitored during spring, whereas satellite imagery for corn can be best monitored in late summer. Sometimes, if a crop’s LAI (leaf area index) is too high, it can be difficult to see problems that might exist beneath the leaves. However,  you will still be able to monitor growth and problems that occur on top. This being said, satellite imagery can still be valuable for other crops besides corn.


Q: When you notice areas of N stress with weeds in them, can you determine what the exact cause is?

A:  It’s a question of if the weeds caused the nitrogen stress, or if the plants aren’t growing as well because of the weeds’ presence: you most likely can’t tell just by looking at it. Early weed pressure can cause a nitrogen stress that may not have been there if the weeds didn’t exist, but usually, weeds come into play because you don’t have a healthy crop with good coverage. Ultimately, it’s difficult to sort those two things out.


Q: Is there a way to hover over FarmLogs satellite imagery with your mouse and get the GPS coordinates so you can know exactly where to go in the field? 

A: We currently don’t offer that service, but we are planning to make improvements in the future. We also get asked about measuring the actual width of the satellite cycles, and it is important to be able to say if it’s a 60 ft. pattern or a 30 ft. pattern in order to match up with your equipment.

As of right now, you will have to determine that by looking at other references in the field, but this is something that we’re discussing as part of our future improvements on this product.


Q: In your opinion, what are the plus and minus attributes of drone imagery vs. satellite imagery? Do you have concerns about variability within the DVI imagery?

A: When comparing drones and satellites, it really comes down to looking at the strengths and weaknesses of each rather than determining which is better.

With satellites, we get a lot of in-season flights, and we also have the ability to access historical images of your field.

We can use that data to understand the field’s history and predict future patterns.

Let’s say you’ve just picked up a new field for next season. With satellites, we’ll actually be able to say what the variation for the field is. You can look at the past images of the field to determine what the variation is because those images exist, with roughly the same quality that a yield map can produce. Satellite imagery can also be advantageous when comparing multiple fields. 

On the other hand, drones can produce higher resolution imagery. Finer imagery does provide more detail, but there are still logistical challenges. If you’re trying to get imagery for 8,000 acres every other week, drones aren’t the most economical. Ultimately, when you look at the cost of getting that kind of resolution, with high frequency of images, and historical records, the drones haven’t caught up yet. The effectiveness of drones is getting better, but there are still issues with getting the imagery depending on the weather and cost. It’s not really a question of which one is better, but rather of what the better option is for you that’s available today.


Q: What’s a short, convincing argument for farm managers who are stubborn about imagery technologies and who lack familiarity with software?

A: The biggest argument is asking “Can you find one thing you can do better in your operation?” 

Satellite imagery can identify so many different problems on your field that it improves your changes of finding something that's gone wrong.

Especially in a wet year, N stress, compaction stress, and diseases can be magnified, and satellite imagery makes it that much easier to find and identify those problems. That’s probably the easiest argument to start convincing some of the farm managers.


Q: How does FarmLogs use remote sensing to create a prescription if the satellite images are so variable throughout the season?

A: It depends on where you are in the season. The first thing you’re looking for is a difference in growth. In most areas, fields are variable and plant growth varies.

The idea of a prescription is to adjust what you’re managing to match the variability of the field.

Lots of people like soil surveys as a general guide, but the reality is that looking at the crop can be a much more accurate way of understanding where the field is different, in terms of what’s actually important to the crop. Even though the crop will vary throughout the season, you still be able to identify general trends. Some areas are typically higher yielding while other may be lower yielding, and that’s where we start. Then, as the season progresses, we start going the other way and monitoring the crop to see how it’s performing.

For some prescriptions, we’re actually measuring based on where it’s at now and how it affects the end of the season, rather than depending on forecasting. It’s essentially a theory of weighing how much you use imagery for prediction and how much you measure reactions.


Q: I just compared a yield map to a sidedress application skip. The yield loss for 12 rows, for a short distance, was great. The FarmLogs satellite imagery was “fuzzier” than expected. Why?

 A: The imagery when going across 6 rows isn’t necessarily going to produce a very high resolution image. 

Satellite imagery can still produce valuable insights, and having this data is still more beneficial than not having it.

While we haven’t perfected everything to the ideal resolution that we want, we now have tools are just so much better at catching more of these problems. The resolution of the imagery will get better, the frequency of the imagery will get better, and our ability to analyze and react in-season will get better.

At this point, just having the ability to identify a mistake that happened this year in your fields that you may not have known, is very valuable for your farm. Having this information will provide you with the insight to fix these problems for the next year.


Q: Does satellite imagery replace the need for a yield monitor and a GPS?

A: Satellite imagery adds to the value a lot, but it’s not doing exactly the same thing as a yield monitor or a GPS. Looking at the satellite imagery isn’t going to be able to provide you with an absolute difference in yield, but it is going to provide you with  a better understanding of the problems in detail and the variability in the fields.  


Missed the live webinar?
You can watch the full recording here » 


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Dr. Tracy Blackmer


Dr. Tracy Blackmer is an expert agronomist with over 20 years of experience incorporating precision agriculture technologies in agronomic management for growers. His work has included organizing a network of over 1,000 growers from 12 different states to conduct Nitrogen adaptive management using imagery, yield response, and other feedback assessments. Tracy also focuses on implementing large-scale, on-farm trials that are easy for growers to implement and result in improved agronomic recommendations. His work as the Vice President of Science at FarmLogs includes developing tools that improve local management for growers through better and simplified recommendations and monitoring.