With a little time, a bit of dye and a good eye, vegetable
farmers can learn to grow their crops more efficiently and
economically, says a University of Georgia scientist.

Vegetable farmers in south Georgia and Florida can grow crops
in all seasons because of the subtropical climate, said Alex
Csinos, a plant pathologist with the UGA College of
Agricultural and Environmental Sciences.

A growing practice

Of the 200,000 acres of vegetables grown in Georgia, about 20
percent are grown in raised beds of soil wrapped in plastic,
called polyethylene film mulch. And the percentage is
growing.

The practice allows the farmer to better control the
environment for the crop and apply things like fertilizers,
pesticides, fungicides and water in a more environment-friendly
way.

To do this, farmers run a thin hose with small emitters through
the bed under the plastic. They then inject this “drip tape”
with the materials, which drip out into the bed.

Missing science

But a major blank in this new method needed to be filled.

Because the drip tape was under the plastic and often under
soil and emitting colorless materials, nobody could say for
sure whether the drip tape got enough of the material to the
plant or into the raised bed.

How much material should run through the tape? For how long? At
what pressure? Is the tape emitting enough materials to
effectively cover the bed? The answers could mean the
difference between a good crop and no crop at all.

The instructions salesmen gave to farmers were “best guesses,”
Csinos said. “At the time, there was no scientific data to back
up what they were saying, or selling.”

Simple science?

So Csinos took some simple blue dye and injected it through
some drip tape under plastic on a raised bed at the UGA Tifton,
Ga., campus. He then sliced down through the bed in various
places. The blue designs in the sliced pieces of the bed showed
exactly where the material was being deposited.

“Now we can say with much more certainty how effective the drip
tape is in delivering materials to the bed under the plastic,”
Csinos said.

Sandy soils pose a problem to Georgia and Florida, said Johan
Desaeger, a postdoctoral scientist working with Csinos. Fluids
tend to drop straight through them. Georgia’s soil can be as
much as 88 percent sand. Florida’s can be 98 percent sand.

Most raised vegetable beds are about 32 inches wide. To control
vegetables’ top two enemies, nut sedge and nematodes, the
entire bed needs to be fumigated. Nematodes are microscopic
worms that feed on plant roots. Nut sedge is a weed.

Initial studies in sandy soils showed that in many cases the
drip tape wasn’t delivering enough material to spread
adequately over the entire bed.

“And when you don’t treat the entire bed, those pathogens
outside the range of the drip tape survive and just come
straight back to that area once the material has leached
through,” Csinos said.

Science doesn’t have to be complicated. It just has to be
effective. Csinos, Desaeger and other UGA researchers have put
many different drip tapes through the blue-dye test. And many
more scientists and farmers have used this method in Georgia,
Florida and South Carolina.

Pesticide manufacturers now use results from this simple
scientific method to write better directions for drip tape
usage on their labels.