Researching The Sustainability Of Organic Production Practices

As the number of organic vegetable growers continues to increase, there has been little research done on the sustainability of these organic practices, according to an Iowa State University reseacher.

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Kathleen Delate, a professor of horticulture and agronomy at Iowa State University, is examining which organic vegetable growing practices are best for the soil, water, yields, and even nutrition. Delate is undertaking perhaps the most comprehensive study of organic vegetable-growing practices by looking at the use of cover crops, manure, tillage, and mulch.

“We are measuring a lot of things,” she said. “We are hoping to provide organic producers with science-based information that they can use to make wise decisions affecting the sustainability of their operations. And we think much of this data can be used for conventional crops as well.”

Using 36 farm plots that each employ different combinations of variables, the researcher hopes to discover which practices work best. The vegetables in the research include tomatoes, broccoli, onions, beans, squash, and lettuce. They will be grown in rotation with one crop planted in the spring, followed in the fall by another.

“The first parameter we’re looking at is cover crops,” she explained. “For cover crops, we are using hairy vetch and rye. That combination is one that we’ve had really good luck with for our vegetable farming.”

In the research, the rye and hairy vetch are planted in the fall after the second vegetable crop is harvested. The cover crops are allowed to stay in the ground all winter and are then destroyed in the spring prior to the first vegetable crop planting.

Cover crop systems have been shown to improve soil quality and Delate hopes that they have other advantages. “One of the theories we’ll be testing is that cover crops can actually attract beneficial insects. 

“We also have some data that the straw from the cover crop could prevent some aerial diseases, but it also keeps the soils moist, which could lead to some root rot and a whole suite of soil quality issues,” she continued. “We’re eager to see the outcomes.”

In keeping with the organic nature of the research, rather than destroying the cover crops with chemicals, Delate’s research team will use a large roller to break the plant stems of the plants.

“The blades of the roller crush and kill the cover crops,” she explained. “It physically breaks the transfer of water and nutrients in the plant.”

None of the cover crop will be harvested and the plants will remain on the field and will add to the organic matter in the soil, said Delate.

The second parameter is the use of composted manure. Organic farming requires that farmers compost manure and apply it at least four months prior to harvesting. Delate’s team will see if these practices have an effect on soil quality and nutrient runoff.

The third input being measured is till versus no-till farming. Delate says that using no-till practices may be challenging. The crushed cover crop may present problems as vegetables are planted through it.

The final parameter is using plastic mulch in the crop production. Using plastic mulch involves growing crops through slits in thin, plastic sheets. Plastic mulch is said to provide benefits such as soil moisture retention and weed suppression, and allows for earlier planting dates.

During the research, soils will be tested regularly using lysimeters from USDA’s Agricultural Research Service National Laboratory for the Agricultural and the Environment to see if nutrients are leaching through the soil.

One other aspect of the study involves food properties of the organic produce. “On top of everything else we’re studying,” Delate said, “our colleagues in Florida are going to run a nutritional analysis, including vitamins and minerals, of the crops in this study.”

The research is conducted in partnership with the University of Florida, Gainesville, and funded by the Department of Agriculture through the National Institute for Food and Agriculture.

Source: Iowa State University News Release