Uncovering the Roots of Success: an Agronomist’s Experience Using a Root Imager For Sugar Cane Production in Brazil

Augusto Ohashi, an agronomist and master’s student at the Federal University of São Carlos, was part of a research project to improve sugar cane yield and biofuel efficiency. To gather insights into the impacts of irrigation and fertilization on crop growth and development, Augusto utilized a root imager to non-destructively study the root systems of sugar cane plants. To understand what Augusto and his team discovered using the root imager, read through the conversation and learn about this groundbreaking research project and its potential impacts on sugar cane production in Brazil.

Augusto’s Insights

Scott (CID): To get started, can you tell me a little about who you are and your background?

Augusto: Here in Brazil, we separate agronomy from agricultural engineering. I’m more like an agronomist. I started using the root imager in 2012 during my master’s project with the Agronomic Institute. It was a two-year project, and the Institute had already purchased the root imager, but they didn’t have someone to use it. So, I started using the imager with sugar cane.

It was part of a huge, multi-disciplinary project on sugar cane involving plant physiology and irrigation. They were trying to develop research around how to improve yield and biofuel efficiency, and so on. The project started in 2011, and I used the root imager in 2012, after the first harvest. We had one cycle – the first sugar cane cycle, which lasted 12 months. We harvested, and when it started growing again, I put the image tubes in the soil to start some preliminary tests. After the second harvest, we started the proper analysis.

Scott (CID): Can you tell me more about sugar cane planting and harvest?

Augusto: After you plant sugar cane, you can harvest it yearly. Every 12 months, you have one harvest. On average, here in Brazil, we plant for five harvests, so every five years, we replant. But, when you irrigate intelligently, for example, plantings can last for eight or nine years. I have been working with irrigation since 2010. When doing my master’s, I chose my advisor, who proposed this project to assess the sugar cane root system because this gives us vital information to use irrigation more efficiently.

Scott (CID): Let’s get into that, then. Can you tell me a little more about your research – what you did and what it resulted in?

Augusto: This experiment used irrigation and fertigation. Fertigation is when you use fertilizers together with water. The irrigation system was sub-surface drip irrigation. This is a new technology for sugar cane and a new system that we’re testing. In Brazil, we don’t have consistent information about the sugar cane’s root system, how deep it goes, or which months have more robust root growth than others. Because, other than root images, the other methods used to assess the root systems are destructive. You have to kill the plant to assess the roots.  When you have the root scanner, it makes it much easier to get this information during the crop cycle.

Scott (CID): What did you do to the sugar cane’s roots?

Augusto: We collect images during the crop cycle, then we measure them using RootSnap to assess root growth and, more importantly, when roots were actively growing – if it was in the beginning, the middle, or the end of the crop cycle. Aside from irrigation, we also tested four sugar cane varieties. We found that root growth was dependent on variety. Some varieties had more growth, and others had less growth in the crop cycle.

Scott (CID): What did you find when root growth was happening?

Augusto: It was interesting because this was a new finding for our sugar cane crop. We saw that 30-50 days after harvest was the peak of root growth. This is very important because when we define this time, we can schedule our irrigation and our fertigation via solid fertilizers for the most benefit and efficiency.

Scott (CID): How many tube installations did you have?

Augusto: 12 tubes total, three tubes per variety.

Scott (CID): How often did you collect images?

Augusto: We tried to collect images every month. In the beginning, after we installed the tube, we took an image as a starting point, and then we waited 15 days and took new images, and after 15 days, collected more images. Then we tried to keep a 30-day schedule. Here in Brazil, we have a rainy season, so when it was very rainy, we couldn’t enter the fields with the scanner, so we had to skip some months, depending on the weather.

Scott (CID): There are always unforeseen challenges in research! Did you encounter any other challenges?

Augusto: Yes. First, we didn’t get the right auger to install the tubes. We had one which was a little bit narrow and one which was a little bit larger. We had to adapt to get the hole in the soil to fit the tube.

Scott (CID): Ah, ok. So, what did you find on root depth?

Augusto: Our study was to provide more information about root depth when you apply irrigation by sub-surface drip irrigation. Interestingly, our adequate rooting depth was very similar to rain-fed conditions. Some people have said that when you apply sub-surface drip irrigation, you will get more shallow roots. We didn’t observe that. They go as deep as in rain-fed conditions. The difference we observed was a much higher root concentration. We had more roots, but root distribution was the same as in rain-fed conditions.

Scott (CID): How does that manifest in the above-ground plant?

Augusto: This was very interesting. Our research was in the city of Campinas, in São Paulo State. This city, for sugar cane, is considered a wet area. Usually, you don’t need irrigation because it rains a lot during the year. But, in Campinas, as well as most cities in São Paulo State, we had a very dry season, and we also had some periods inside the rainy season in which we experienced ~10-day periods without rain. So, when we applied water in that condition, which was the case in our experiments, we had crop yields of 3x the average Brazilian yield.

Scott (CID): That is a remarkable finding. How do your research and these findings ultimately impact the commercial side of agriculture?

Augusto: From this research, there were two main results. The first one was to show that most sugar cane root growth occurs between 30 and 50 days after harvest. This was an important finding. The other was to measure and analyze root growth with subsurface drip irrigation, which was very new information to the field.

Scott (CID): Do you have any tips or advice for other researchers embarking on research with the root analyzer?

Augusto: Actually, this was the subject of our paper that was just published. The first one is about tube installation. You have to be very careful to ensure you have contact with the soil and the tube. You can’t have air spaces between the tube and the soil because if you don’t have tight contact with the tube, the roots can’t reach the tube, and air pockets will collect water drops, which analyzes with RootSnap much harder.

Another issue is how you install the tubes – vertically or at an angle. We installed them vertically at 90 degrees from the soil. But, another researcher installed them at 45 degrees, using the same tube length. If you use the same tube length and install it on an angle, you will reach shallower depths in the soil. For example, if you install a one-meter tube vertically, you will get up to 80 cm in the soil. If you install the tube at 45 degrees, you will have 60 to 70 centimeters maximum. If your crop has deep roots, maybe it’s more practical to install the tube vertically, so you have to take the root depth of your crop into account.

Lastly, I would recommend doing tests on the timing of when you take images. You should know how often you will need to get the images- every week, every 15 days, or every month before you embark on your research. During my master’s, I did previous tests.

Scott (CID): That’s perfect. Great advice for anyone using the imager. Thank you so much for your time, Augusto.

Augusto: Thank you, I appreciate our conversation. I think it’s very important for scientists to talk to you guys from the company to share experiences to make our work more visible and your instruments more usable.

In summary, using a root imager proved to be a powerful tool for studying the root systems of sugar cane and gathering valuable insights into the impacts of irrigation and fertilization on crop growth and development. Augusto and his team faced several challenges along the way. Still, they gathered crucial information through persistence and determination that could revolutionize sugar cane production irrigation practices and ultimately improve yields and biofuel efficiency. We are grateful to Augusto for sharing his experience and insights with us. We hope this conversation serves as a helpful resource for others looking to optimize irrigation practices in sugar cane production.

See Augusto’s research here – 

Minirhizotron as an In-Situ Tool for Assessing Sugarcane Root System Growth and Distribution

Root Growth and Distribution in Sugarcane Cultivars Fertigated by a Subsurface Drip System