While the use of cover crops and conservation-tillage has increased markedly in row crops in recent years, vegetable growers continue to be reluctant to introduce such methods into their production systems. The reason, says University of Georgia Horticulturist Sharad Phatak, is that vegetable producers aren't willing to take any risks to save a few dollars by changing tillage alone.
“It's essential to introduce a total system, which in addition to reducing tillage also reduces the use of fertilizers, insecticides, fungicides, nematicides, herbicides and other off-farm inputs,” said Phatak at the recent Southern Conservation Tillage Conference for Sustainable Agriculture held in Auburn, Ala. “This will make a production system really sustainable.”
The popularity of cover crops never has been as high as it is today, he says, and there appears to be a cover crop available for every need.
“However, cover crops in vegetable production are used primarily as green manure crops. When used as a green manure crop, cover crops are chopped by disking a number of times and then burying the residue deep with a moldboard plow.
“Disking and plowing accelerate oxidization and decomposition of cover crop residues and soil organic matter. Thus, the benefits derived from plowed-under cover crops are only temporary. This practice of plowing under cover crops fails to bring about a permanent change in soil organic matter or soil physical properties,” says Phatak.
To make vegetable production sustainable, it's essential to make a permanent change in soil organic matter and soil physical properties, he adds. “Changing tillage from conventional to conservation in combination with cover crops will achieve this objective. The integration of conservation-tillage is important to make vegetable production truly sustainable,” he says.
It's essential, says Phatak, to have a thorough understanding of tillage for optimum vegetable production and to maintain soil productivity for the future.“Soil conditions that directly regulate plant activities include soil moisture, soil aeration, soil temperature, soil nutrients and soil strength or soil compaction.”
Soil tillage in vegetable production can be classified into three forms — primary, secondary and tertiary, he says. Primary and secondary tillage are used as pre-plant preparation of the seedbed while tertiary tillage is performed after planting vegetable crops to control weeds and reduce compaction between rows.
“In vegetable production, primary tillage is performed with a moldboard plow. Secondary tillage is used to prepare a fine seedbed just before planting. Rotary hoes, sweeps and other equipment are used for tertiary tillage. In conventional vegetable production, all of these tillage operations are essential to maintaining a high level of production. However, intensive soil tillage erodes and degrades soil.”
Previous research, notes Phatak, has shown permanent increases in soil organic matter by changing tillage from conventional to conservation. Conservation-tillage, he continues, is an essential component of sustainable agriculture, as it helps to improve soil organic matter and productivity.
Conservation-tillage, he says, hasn't been researched in vegetable production as it has in row crops. “Using conservation-tillage for vegetables should be implemented only where it has been proven to be consistently successful.
“Most research on conservation-tillage in vegetable crops has been on individual aspects of vegetable production. For example, we've seen research on fertility, weeds, insect pests, diseases and nematodes but not on total systems. Some research has been done comparing conventional and sustainable vegetable production.”
Since 1985, Phatak has looked at conservation-tillage in vegetable production in small plot and on-farm research. “Overall, most recent research on conservation-tillage on vegetables has been very encouraging. However, more practically oriented research is needed to integrate conservation-tillage in a sustainable vegetable production system.”
A total systems approach, says Phatak, including insect, disease, nematode and weed management, is more sustainable than “treat the symptoms” strategies.
“Since 1985, major vegetables like tomatoes, eggplants, peppers, snap beans, Southern peas, lima beans, cucumbers, cantaloupes, squash and watermelons have been produced without insecticides, fungicides and nematicides. These pesticides were not needed to produce these crops. The use of fertilizers and herbicides also was greatly reduced.
“Vegetable growers using these strategies were able to improve their bottom lines and increase profits. However, more multi-disciplinary research with this approach is needed to make sustainable vegetable production systems practical for all growers.”