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Plastic tarps increase vegetable yields

March 5, 1997

STATE COLLEGE, Pa. (AP) _ In his dreams, Penn State professor Michael Orzolek sees America’s farmland covered in a mosaic of electric colors: blue for cucumbers, red for tomatoes and yellow for peppers.

Over the years, scientists have found that brightly colored plastic sheets spread over farm fields can lead to bigger plants and larger yields. For Orzolek, the challenge has been finding out which plants respond to which colors.

In trials last summer in Rock Springs, for example, Orzolek nearly doubled the yield of tomatoes grown on a field covered with blazing red plastic.

``One day I hope to look out an see a kaleidoscope of colors out there,″ he said recently. ``Now we just have to get the word out.″

For decades, farmers have spread plastic on their fields to hold down weeds, keep in moisture and regulate soil temperature. They call it mulch, though it’s a far cry from peat moss. Generally, though, the plastic is black.

Research into the effect colors have on plants began in the 1960s and was resurrected again in the 1980s at Clemson University in South Carolina. Experts now believe that a ``growth regulator″ called phytochrome reacts to the reflected colors and, depending on the wavelengths, causes plants to grow short and thick, or tall and thin.

By the end of 1991, scientists had seen 10 percent to 15 percent yield increases with some colored mulches, according to plant physiologist Michael J. Casperbauer and soil scientist Patrick G. Hunt of the Soil and Water Conservation Research Center in Florence, S.C.

The trick is finding out which plants respond to which wavelengths. Enter Orzolek, who began his color research in the early 1990s.

In his work, Orzolek has seen squash grown on beds of bright blues yield 30 percent more than squash raised on black plastic. Cantaloupes and other melons appear to like silvers. And tomatoes really seem to dig reds.

The key is balancing the many different effects plastic can have on crops. The original moisture-and-temperature regulating uses need to be watched carefully, as does the durability of the colors. Orzolek credits a new colorfast red with increasing the tomato yields last summer.

``It’s astounding,″ said Robert Marvel, 59, who has farmed in central Pennsylvania for almost three decades. ``When I look at it it’s unbelievable to me. It’s like science fiction.″

Marvel has been experimenting with colors for the past nine years. At his Campbelltown farm, his cantaloupes and watermelons, planted on a field of green plastic, come up seven to 14 days earlier than normal, giving him a head start in the highly competitive produce business.

``It’s dog-eat-dog, hand-to-mouth, and this helps the farmer get another window,″ he said.

Not all farmers have had such success. Paul Zimmerman, who farms 25 acres in Mifflinburg, didn’t see much of an increase in his peppers when he put them on red, blue and yellow plastic last year. ``I think the people are not really convinced yet that it’s that good,″ he said.

James E. Welshans, an agriculture extension agent with Penn State, said he hears a lot of comments like Zimmerman’s as he works to spread the findings of university researchers.

``Change is tough to come by,″ Welshans said. ``We still got a group of people out there who don’t want to wear seat belts.″

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