Sentek Technologies is an Australia-based irrigation solutions company active around the world. While sensor technology is its mainstay, Sentek’s broader offerings fall into the category of knowledge products. Knowledge products include data analysis and recommendations that help answer substantive questions like how deep to irrigate or how to space one’s crops.

In this interview, Sentek cofounder Peter Buss tells Irrigation Leader about the company’s origins, its products, and trends in the irrigation management world today.

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Irrigation Leader: Please tell us about your background.

Peter Buss: I was born in Germany and migrated to Australia in 1986. I studied tropical agriculture in Germany, specializing in irrigation management and plant nutrition in Australia. When I arrived in Australia, I was offered a job in the Australian Department of Agriculture to set up a commercial irrigation scheduling service. In Australia, citrus, almonds, and vines are the main crops grown, similar to the case in California. We have a lot of visits from Californians and vice versa. I started an irrigation management service using a portable device called a neutron probe. It was labor intensive to collect data with this instrument. You had to have all sorts of security training, and you had to wear radiation badges. You would take readings by lowering the radioactive probe into an aluminum access tube that was installed in the ground, pressing a button, waiting 16 seconds for the reading, and lowering it to the next soil depth level. It sounds low tech, but in 1986 it was revolutionary, and the growers I worked with started to appreciate it. A lot of areas were severely overwatered. We had water tables at 1 meter, and a lot of money was spent putting drainage systems in. That’s all gone today: Hardly anybody is using drainage systems anymore because of how fantastic a job irrigation scheduling did. Today, using the same amount of water they did in 1986 on a regional basis, growers can irrigate a significantly larger orchard area.

The Department of Agriculture charged for this irrigation management service, so people valued the advice they were getting, rather than treating it as a free service. The irrigation management service grew rapidly, and I had to hire three more people to extend the service to other growers. One day, my boss decided that we should do this on a fully commercial basis. We exited the Department of Agriculture and set up a company called Watson Buss & Associates. We provided the service full time and expanded from South Australia into the neighboring state of Victoria and the Northern Territory. 

After 3 years, it dawned on me that we couldn’t go on like this because the instrumentation we were using to collect soil water data was too labor intensive. We spent most of our time collecting and retrieving data rather than analyzing the data. I realized that we needed a new technology, so I began to read scientific articles about capacitance probes. There was a Polish scientist in the 1940s who had built a sensor that was located inside a tube. I liked the tube approach because being able to measure at multiple depth levels is tremendously helpful in understanding soil moisture. It allows you to gauge the depth of the root zone, the depth of percolation of water, and so on. The capacitance sensor mentioned in the paper had never taken off because the sensor operated at a low frequency range, namely the kilohertz range. As I continued digging through scientific articles, I found that in the 1970s, scientists had suggested increasing the frequency into the megahertz range in order prevent soil salinity from affecting the moisture readings. That was a little breakthrough. 

Sentek’s fully encapsulated Drill & Drop probe, installed in the ground.

I approached a friend of mine who was an electronic engineer and asked him to build me a high-frequency soil water capacitance sensor. He told me he’d have it by Monday. The sensor he came back with measured everything: the fridge door opening and trucks going past. I said, “Very nice, but I just want it to measure water.” Like me, he was working full time, so it was probably another year until he came to me with a sensor he said was absolutely stable—it responded to water in the soil and nothing else. We tested it with encouraging results and went on to build 11 systems by hand, each of which consisted of a car battery, a lunch box, and a little probe with three sensors on it. The capacitor was basically two metal rings separated by a bit of plastic with the sensor itself in the center. We found a bit of water pipe, cut it into rings, assembled it on a little plastic stick, and inserted it into PVC tubes installed in some onion and potato fields just outside Adelaide whose owners allowed us to experiment with our sensors there. 

I visited all the sites on a weekly basis, checking things and downloading the data. The growers were interested in the near-continuous data I was gathering—the measurements were recorded every 10 minutes. They were looking over my shoulder asking, “What does this mean?” I’d tell them, “Since you asked, the water from your pivot didn’t go deep enough—you’re running it way too fast,” or, “You should have irrigated 2 days ago,” or, “You’re irrigating too much.” Toward the end of the season, one of the farmers asked me to convene a meeting in the town hall and talk about the data. I anonymized the data and did a presentation on the mistakes that the different individuals had made. Only the individual farmers knew which data came from their own farm. They looked on in awe. Suddenly, the main guy got up and said, “Peter, would you leave the room?” Rick, the electronic engineer, and I left the room. We heard a lot of murmuring inside, and after 15–20 minutes, we were called back in again. The main grower said to me, “We cannot afford not to have this technology in the next growing season. We would like to put some money together for you to start a company.” It was like being struck by lightning. I had to go home to my wife and explain that. I said to my business partner, “Something happened today that doesn’t happen every day,” and after some thought, I accepted their offer. These growers contributed the money, and Rick and I started Sentek in April 1991. The name stands for sensor technologies.

Irrigation Leader: Where are the company’s headquarters?

Peter Buss: They are in Adelaide, the capital of South Australia. South Australia has a population of only 1.5 million, so it is sparsely populated. It’s actually the driest state in Australia—most of it is desert. Most of its agriculture is along the River Murray, which winds its way from the state of Victoria into South Australia. That is the major supply of irrigation water for a lot of horticultural crops and the vegetable industries. The rest of South Australia is basically dry-land agriculture, growing mainly wheat using sparse rainfall. Relying on that is always a gamble. People just plant wheat and wait for rain; sometimes it comes, sometimes it doesn’t. 

Irrigation Leader: How did Sentek become a global company?

Peter Buss: We set up a distribution network. We started in Australia in 1991, and in 1992 we went to California and met with Dr. Louise Ferguson, a professor from the University of California, Davis, who studied nut crops. She had attended some of my early talks in Australia and had offered to organize some meetings for me the next time I was in the United States. Our meetings in the United States sparked some interest. We set up some trial systems and one person took the technology to a large agricultural research center in Beltsville, Maryland. These people liked the technology, but they didn’t know anything about it. They actually took the devices apart and investigated how reliable and accurate they were. They published the first paper on the technology in the Soil Science Journal of America. This sparked customer interest from universities in California, Florida, and Washington State. After establishing a customer base in the United States, we branched out into other countries. Today, our technology

Sentek users consult data on a tablet.

is being used in over 80 countries around the world, and we have about 35 employees. 

A lot of our distributors are irrigation agronomists. For them, our technology is another tool they can use to offer a better service to their irrigator customers. We find that it is best to have trusted advisors who live locally and work with the growers to introduce any new technology. If those advisors get to know farmers and deliver results, people will start to trust them and likely adopt the new technology. Learning to interpret the soil water data is the key to changing irrigation management. If you don’t successfully teach people to do that, then a soil moisture monitoring technology will never be successful. We have found that irrigation agronomists are the best people to do that. 

Irrigation Leader: What kinds of probes and sensors do you manufacture today? 

Peter Buss: We manufacture multisensor profiling probes that measure soil water, soil salinity, and soil temperature. These probes come in different lengths: 1 foot, 2 feet, 3 feet, and 4 feet. We also have a single sensor that measures a soil horizon of 4 inches. All the sensors log data every 10–15 minutes and upload that data to our IrriMAX Live cloud around every 2–3 hours, where the information is used to update easy-to-understand graphs that guide growers in their irrigation management. The latest probe communicates with Bluetooth Low Energy. This means you can download the data to your phone when you are visiting the field and then upload them to the cloud. No cables, no modems, no solar panels, and no mounting poles are involved. 

Irrigation Leader: What can your technology do for irrigated farmers? 

Peter Buss: The business of agriculture relies on reducing inputs like water and fertilizer, and our technology can help prevent overirrigation and the waste of fertilizer. A lot of fertilizer leaches into the ground because of overirrigation, and unnecessary irrigation also requires labor that can’t be used elsewhere. Reducing inputs is one side of the coin; the other is increasing yield and crop quality. If you become more consistent, you become more attractive to supermarkets. If you can deliver a certain amount of produce of a certain quality in a certain window of time, your business becomes much more solid. 

Irrigation Leader: What trends do you see in irrigation technology and management? 

Peter Buss: The challenge today is understanding what water does in the soil and how it affects the crop, and then communicating that information to the end users quickly and in a way that is easy to understand. Rather than providing raw information to a user, we are delivering predigested recommendations that we have used algorithms and artificial intelligence to create. We are also working on automatically detecting crop stress and other key variables for irrigation management. 

Farmers need to be able monitor a lot of fields and prioritize irrigation management. If it rains overnight, priorities can change. Developing a way of quickly communicating information like that is one of our biggest challenges. Cloud and Internet-of-Things technology will assist with this irrigation decisionmaking by integrating data inputs like weather forecasting, plant measurements, power cost forecasting, and satellite images of crop canopy changes. 

One factor that is often neglected is irrigation system health. Irrigation systems can have problems with the distribution uniformity of water, pressure, the spacing of drippers, and insufficient water delivery systems. Before people spend money on irrigation scheduling, they should first make sure they have a good system that enables excellent water distribution uniformity. If you’ve got a distribution uniformity of water of 40 percent, it is actually dangerous to use sensors because you don’t know whether they’re in dry or wet spots. Good irrigation management has to be built on the foundation of good irrigation system health. 

Another factor is the cost of power. In Australia, our power prices fluctuate every half hour. That must be factored into irrigation management decisions along with weather, crop stage, and soil moisture. Crop stage is important because irrigation management changes as roots go deeper, particularly with field crops. How do you irrigate at the beginning, in the middle, and toward the end of the season? The future of irrigation management is integrating all these factors in a multiparametric calculation. 

Irrigation Leader: What is your message to irrigating farmers and irrigation districts about Sentek? 

Peter Buss: They should know that we’ve been around for almost 29 years. We’re not a startup. We have learned a lot, and what we’re selling is not just probes: We sell insights and solutions. 

We really like to work with farmers. Generally, we put a system in, we watch an irrigator’s water management, we see what happens, and we gently educate them and correct them if there are any mistakes. That gets results. Then we expand to other parts of their property. That builds trust. We’re interested in building long-term relationships and helping farmers manage their irrigation in the best way possible. 

Peter Buss is the manager of agronomic research and development at Sentek Technologies. He can be contacted at