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Doug Sturtz and Jonathan Frantz use spectrometry to detect plant nutrients. Link to photo information
Technician Doug Sturtz (left) and horticulturist Jonathan Frantz use spectrometry to detect plant nutrients. They would like to develop a portable sensor for greenhouse use. Click the image for more information about it.

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Letting Plants "Talk" to You

By Don Comis
June 20, 2007

The greenhouse manager of the future walks around the greenhouse, pointing an infrared "flashlight" at potted plants. A tiny screen tells whether each plant has too much, too little, or just the right amount of nutrients.

During the past three years, at a new facility in Toledo, Ohio, Agricultural Research Service (ARS) plant pathologist Jim Locke and horticulturist Jonathan Frantz have made a great deal of progress toward realizing this automated future. Frantz is testing commercial nutrient sensors with a view toward developing improved portable ones. Devices like these can give greenhouse growers a few—often critical—extra days to correct nutrient problems before their plants are seriously damaged.

In one approach, Frantz, Locke and colleagues are testing ways to bounce infrared light off plants, in order to read the earliest possible signals of nutrient deficiency. The signals could be key proteins or other molecules associated with stress, or a change in a leaf’s light reflectance as a result of a deficiency. Spotting ways in which plants signal stress would be a way to detect a problem before any visible evidence of damage to the plant occurs.

Currently, the scientists use commercial portable sensors that detect nutrient ions but are expensive and have to be calibrated properly. They would like to develop an easy-to-use portable kit that growers could buy at a reasonable cost.

The scientists also use inductively coupled plasma (ICP) spectrometry to determine plants' total nutrient content, but that test is suitable only for laboratory use.

The Toledo location is a worksite of the ARS Application Technology Research Unit at The Ohio State University-Wooster. It comprises labs, offices and greenhouses on the University of Toledo's main campus, as well as 8,000 square feet of greenhouse space leased from the nearby public Toledo Botanical Garden. At the garden, sensors have been installed to record everything from nutrient levels in leaves to moisture in the soil or potting mix.

Read more about this research in the May/June issue of Agricultural Research magazine.

ARS is the USDA's chief scientific research agency.