“Using plastic mulch jumps melon harvest up by 10 days to two weeks,” says Bob Wiedenfeld, soils scientist at Texas A&M Agricultural Research Center in Weslaco. As every farmer knows, the earlier the crop, the better the profit. So why don't all farmers use plastic?
“It's an expensive proposition. Not only is the plastic itself expensive, the farmer has to pay high costs to lay it down and then, after harvest, to pick it up,” says Wiedenfeld.
“If only we could get two crops out of the plastic, we could more easily justify the expense.”
And that is one of the purposes sponsored by the Ampacet Corporation, the producer of the additives that go into making the plastic film. But the experiment is concerned with more than just durability. The company also wants to determine which of the many plastics is best for the development of the crop.
The field trial began in January when watermelon was planted. Drip lines run down the middle of the 80 inch beds providing water and fertilizer to the melon crop.
Instead of just the standard black plastic used by most Rio Grande Valley farmers, a variety of colors was used. It has been found that not only do different colors of plastic perform differently, the texture and finish also have an effect on the crops.
The main purpose of plastic mulch is to warm up the soil, but it can also provide weed and insect control.
A yellow plastic has been seen to draw insects and could feasibly even be used to attract insects to keep other plots bug-free.
Some plastics that do a good job warming up the soil and providing weed and insect control may not be the most durable. This all must be taken into consideration in determining the right plastic to use in a certain area.
“We measure vine length and soil temperatures at regular intervals,” says Wiedenfeld, “and compare them to melons that were planted without plastic.”
The vines under all varieties of plastic have consistently shown better vine length than the check group. Right now the clear plastic is leading the pack in providing a warmer soil.
“It also appears to be more durable than the other colors, but, unfortunately, provides little weed control. Better weed control was shown under the silver color, which also rated high in warming the soil.
For summer planting a two-toned film, white on black, can be used. The white reflects the heat, cooling the soil, while the black underneath keeps weeds from growing.
“Durability is a big factor,” says Wiedenfeld. A more fragile plastic might do the job with the plants, but high winds in the Rio Grande Valley can tear it into shreds.
Which plastic is the strongest will be determined after the second crop. “We'll be putting in peppers after the melons are done,” says Wiedenfeld.
The results of this study should be available later in the year.
Plastic mulch has come a long way in the last few years. Previously the plastic film was not pliable enough to install in cool temperatures. Lately, more pliant plastics have been developed to change this, allowing farmers to get their plastic and their crops into the ground earlier.
Companies have also tried to develop biodegradable film, but so far with little luck.