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Superabsorbent amendment developed by USDA increases yields

Work that began in 1984 at the USDA-ARS National Center for Agricultural Utilization Research in Peoria, Ill., is now coming to fruition in California's processing tomato fields in the form of a cornstarch-based superabsorbent soil amendment called Zeba.

Along the way, various forms of the starch material have been commercialized as seed coatings, wound dressings, engine fuel filters, foam packaging material and a host of other diverse products.

But to growers in the West, the real value of the superabsorbent starch is as a production tool that has consistently increased tomato yields in commercial trials over the past two years.

Zeba is a granule product that will absorb more than 400 times its original weight in water. This captured moisture is released in response to capillary action from root hairs, providing a steady supply of water to plants between irrigation cycles.

“The technology of Zeba makes perfect sense,” says agronomist Jerome Pier, Western Farm Service, Stockton. “Applied as a sidedress and shanked in, Zeba can retain both water and nutrients in a solution in the active root zone. It will give water back, rehydrate with subsequent irrigations, and keep repeating this process throughout the season,” he says. “Where we've used Zeba, it gets results. Because nitrate and urea go through the soil profile rapidly, Zeba gives growers a double benefit,” the agronomist says. “The nitrogen will be there for the plants, and, there is less of a risk of nitrate leaching into the groundwater. In addition, a moisture- and nutrient-rich environment should also serve as a good environment for beneficial microorganisms.”

Pier points out that other absorbent products are petrochemical-based, and while they “suck up a ton of water,” they don't give it back to the plants. “It makes sense that an organic carbohydrate product should have the ability to retain water and nutrients in a solution.”

Tom Pierson, a PCA with Gar Tootelian, Reedley, worked with OPC Farms to test the soil amendment in the field. About 1,300 acres in several fields were treated with Zeba. From each field, 10 acres were left as checks.

“We did field samples and extrapolated our counts and got over 5X return on investment (ROI) at almost every field,” Pierson reports, adding that every field showed a yield increase, even those with buried drip irrigation.

“I think this is because there was less stress on the plants because they got water all the time. Zeba is holding water next to the roots.”

The soil types in these test fields ranged from sandy to loamy to medium, with the drip field on medium soils, indicating that even in drip-irrigated fields tomato plants can benefit from extra moisture around the roots.

Application of the soil amendment granules was made with Gandy boxes set up on a toolbar, about 5 inches away from the plants and then shanked in about 4-5 inches down to encourage root growth. Applications were made after transplanting, but prior to bed shaping and mulching. Two weeks elapsed between planting and Zeba application.

“The price of tomatoes is going up. With the yield increases we're getting, growers get a good, strong ROI with at least a 2 ton increase over the check,” Pierson says. “I will be recommending it to my growers.”

Only two years on the market in California, commercial trials include grapes, peppers, eggplant, melons, squash, cucumber, and new almond plantings.

“What makes it so beneficial to plants is that it evens out the highs and lows of moisture available to plant roots between irrigation cycles, and this reduces plant stress,” says Zeba's Gary Olson.

Zeba is made by Beaverton-Ore.,-based Absorbent Technologies Inc. (ATI), the first company to create starch-based polymers optimized for agriculture. The core technology was developed by USDA scientist William Doane who spent years researching superabsorbents, but until recently was unable to create a form that was suitable for commercial agricultural applications.

In 1994, Doane collaborated with ATI founder and CEO, Milan H. Savich, to develop the starch-based polymer into a usable product for agriculture. The result: a granule suitable for application was created in 2003 and the product was commercialized a year later. ATI holds two exclusive Cooperative Research and Development Agreements with USDA and a patent portfolio for applications in seed coating, agriculture, formulations and ingredients.

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