Plastics and vegetable production would seem to be an unlikely combination. But six years of testing and development in southeastern Colorado is proving that this unlikely pairing of organic and synthetic goes together like peanut butter and jelly.
The vegetable production part of this story takes place in the Arkansas Valley where more than ten thousand acres of vegetables are grown each year, including world-famous Rocky Ford cantaloupes and watermelons.
The plastic part of this story is a growing system called plasticulture. Plasticulture uses a lightweight plastic film or mulch that covers the seed bed to control soil temperature, moisture, and weeds. Plants poke their heads through slits in the plastic and are watered by drip irrigation, a network of small plastic tubes placed under the plastic mulch that delivers water to the plants in precise amounts.
Colorado Agricultural Experiment Station scientist Mike Bartolo says experiments at the University's Arkansas Valley Research Center during the past six years show significant advantages for plasticulture-produced vegetable crops. Cantaloupe and tomato yields almost doubled in some test plots and regularly matured as much as two to three weeks earlier than conventionally grown crops.
Bartolo says the plastic mulch keeps weeds from growing while it also warms the soil and promotes early spring plant growth. That's why cantaloupes and tomatoes often go to market earlier than with conventional production. Earlier harvests provide an improved window for marketing at better prices for producers, plus a more uniform supply of high-quality produce for consumers.
Meanwhile, the drip system irrigation saves money and is more environmentally friendly than conventional irrigation. Drip irrigation systems slowly and continually apply small amounts of water to plants. The plant root absorbs as much as it needs in the time it needs to absorb it with little waste. Conventional furrow irrigation results in a lot of water being applied at one time, which means that much is wasted as it runs past the roots and into the ground. The excess water also leaches nutrients such as nitrogen into the groundwater system.
Onion production offers a slightly different challenge in the Arkansas Valley. Some of the onions grown in the valley are started from transplants produced in the milder climates of Texas, Arizona, and California. But Bartolo says they often harbor diseases and insects. This forces growers to use expensive pesticides for control. Using the plasticulture principle of early growth, some producers have begun to grow their own onion transplants locally in greenhouses or under plastic row covers in early spring. Preliminary experiments show little or no evidence of disease or pest problems for transplants grown locally, although more research is needed to make the process cost effective.
So far, high up-front costs to convert to drip irrigation — up to $1,000 per acre for pumping and filtration systems — have made many growers reluctant. But Gary Shane, who raises cantaloupe on the 350-acre family farm near La Junta, says plasticulture is the only way to go. He's among a few larger growers in the valley who have converted to plasticulture techniques. "It uses less water, less fertilizer, fewer pesticides," he says, "and less labor and machinery once the beds are planted and growing." Quality and yields have improved, too. Shane became convinced he needed to change after visiting fruit and vegetable growers in California and Arizona who had converted to plasticulture.
Melons grown in Rocky Ford have a reputation for quality and sweetness that melons from other markets can't match, says Shane. "But we have to make certain they exhibit appearance and shelf quality that melons from other markets have. We can do that with better growing practices that include plasticulture," he adds.
Although Arkansas Valley irrigation water may be relatively inexpensive now, it won't stay that way as more people move to Colorado. "Our crop producers need to demonstrate they can cut water use and produce even better quality than ever before," Shane says. "These new growing techniques with plastic help us do that."