December 2003

Soil pH sensor Commercialized

 

J. Lowenberg-DeBoer

 

Introduction

            Veris Technologies sold the first commercial on-the-going pH soil sensors this fall. The first batch of sensors went to fertilizer dealers, a crop consultant and a farm equipment dealer in Indiana, Ohio, Michigan, Louisiana and Washington. The sensor was based on an interdisciplinary research effort led by faculty in the department of Agricultural and Biological Engineering, ABE. This article provides a brief review of the history of soil sensor development at Purdue and an update on soil pH sensor commercialization.

            The introduction of a pH sensor signals a new stage in precision agriculture and new opportunities for crop consultants and ag retailers. Until the introduction of this sensor, soil sampling meant that someone had to poke holes in the ground and send samples off to a lab to be analyzed.

            The Veris Technologies Mobile Sensor Platform (MPS) automates the soil sampling process and keeps everything within the field. The technology scoops up a sample, presses it against the same type of sensor used in laboratory pH tests, and takes a reading. The sensor is mounted on a cart and typically pulled through the field by a pickup or a small tractor.

            The density of samples depends on speed and spacing between passes through the field. Commonly the pH sensor is taking 4 or 5 readings per acre. The pH data is available in real time with a few seconds lab allowing electrode stabilization..

 

Soil Sensors at Purdue

            There is a long history of soil sensor research at Purdue. Larry Gaultney, then in ABE, now with DuPont, developed an optimal soil organic matter sensor in the late 1980s. Mark Morgan, then in ABE, now in the Purdue Food Science Department, started work on a soil pH sensor in the early 1990s. Other faculty involved at that time include: Dan Ess, ABE; Darrel Schulz, Agronomy; and Dave Mengel, Agronomy.

            The technology eventually commercialized by Veris Technologies (www.veristech.com) stems mainly from the work of Morgan, Ess and an ABE graduate student, Viacheslav Adamchuk. Adamchuk is now on the faculty of the University of Nebraska-Lincoln, in the Biological Systems Engineering Department where he continues to work on sensors for other soil characteristics. The pH sensor technology was patented by Morgan, Ess and Adamchuk in 2002 and licensed to Veris.

            The work on current soil pH mapping method was initiated in July 1997 and publicly disclosed in the summer of 1998. A United Soybean Board grant in 1998 helped in further engineering, and in better understanding the agronomic and economic significance of the data collected. Jess Lowenberg-DeBoer, Ag. Economics, and his student Alan Hallman estimated the potential value of the sensor data and found that the higher data density was key to the economic value of the technology. Sylvie Brouder, Agronomy, was on Adamchuk’s doctoral committee and helped him understand some of the complexities of pH measurement.

            Veris Technologies showed an interest in the pH sensor during AgInfo ’99 conference held at Purdue University. A commercial prototype was later developed through a grant from USDA/CREES Small Business Initiative Research (SBIR) project. Veris MSP was first publicly demonstrated at the Purdue Agronomy Research Center, in July 2003, as part of the Top Farmer Crop Workshop, six years after the beginning of method development.

            An on-going SBIR funded research effort by VERIS and UNL continues until Fall, 2005. Data fusion and variable rate prescription development remain the focus of current research activities aiming to enhance feasibility to economically manage soil pH and other amendments using a site-specific approach.

 

 

View from Veris

             Eric Lund, who has led the development of the pH sensor at Veris, said that the sensor sold in 2003 were “preproduction” units with some parts still being built by hand. As with most new products there were still a few bugs to be worked out.

            “The response has been very strong,” Lund said. “The data looks really good, but we did realize that a commercial sensor will need more warning devices to let the operator know when something is going wrong. Some users had a problem with stray voltage, but we have fixed that now.”

            “Also we realized that in areas with rock ledges, we will need a spring reset. The sensor now has a shear bolt and that works fine for the occasional rock, but not with rock outcrops.”

            Users have learned to deal with the fact that the sensor measures pH, and not buffer pH. Lund said that some used the sensor data to identify low pH areas which are then manually sampled to determine buffer pH in those areas.

            Lund said that other users have employed electroconductivity (EC) information to help estimate buffering capacity. All of the pH sensors sold also were equipped with EC sensors. Technology currently being developed by Veris will add optical sensors to the package with an initial aim of estimating organic matter levels.

            “With pH, EC and organic matter, we can do an even better job of estimating buffer pH,” Lund said.

           

Opportunities

            Studies at Purdue University suggest that the pH sensor will see rapid adoption. The pH sensor responds to an urgent need for higher density soil data at an affordable cost. In many areas variable rate application of lime is becoming a standard farming practice, but growers and those that advise them are increasingly aware of the pH variability within the grids and management zones. Soil pH mapping is an additional service that ag retailers can provide their clients, in addition to or instead of manual soil sampling.

            The pH sensor can be expected to see more rapid adoption than soil EC sensor because the data is easier to interpret.  There are well developed recommendations for lime application based on pH measurements. Using EC information in crop management requires more skill and interpretation than using a pH measurement.

 

For more information:

 

Adamchuk, Viacheslav, “On-the-go Mapping of Soil Properties Using Ion-Selective Electrodes” Fourth European Conference on Precision Agriculture, Berlin, Germany, June, 2003, http://bse.unl.edu/adamchuk/