New Studies

Winter 2003-2004
By Eric Sideman, Ph.D.

In the fall I attended the 100th anniversary, annual meeting of the American Society for Horticultural Sciences in Providence, Rhode Island. The ASHS has a good mix of members representing university researchers, Extension educators and industry who study all aspects of crop production. The reports covered very basic plant science to practical aspects of farming. The small sample below gives you an idea of some of the work that ASHS does. These ASHS reports often relate to very new studies, so they frequently raise issues for more thought and trials, rather imparting firm recommendations.

Reducing Weeds by Mulching with Clay
(Fumionmi Takeda et al., USDA-ARS, Kearneysville, W.V.)

In this experiment, researchers transplanted container-grown blackberry plants into square openings cut in a woven fabric weed barrier on raised beds. Four treatments were compared: 1) a layer of M96-018 kaolin (Engelhard Corp., which is the company that makes Surround); 2) herbicide; 3) pulling weeds by hand; and 4) a control with no weed management. The weed species were documented and percent of ground covered by the weeds was measured. As you would expect, the control treatment had 100% weed cover by the end of July. The hand weeded treatment had 27% cover, while plots treated with herbicide or kaolin had less than 3% cover. Seeds may germinate but do not seem to be able to grow through the clay mulch.

Mixtures of Cover Crops Enhance Weed Suppression Effect
(McGiffen, U. Cal. Riverside)

Sudangrass and cowpeas are warm weather cover crops with different growth habits. Cowpea is a broadleaf legume that can spread to shade the soil surface, while sudangrass rapidly grows a tall, dense canopy. Mixtures of cover crops have commonly been used to optimize the benefits associated with each species. The mix of sudangrass and cowpea may yield more soil-enriching carbon and nitrogen than monocultures of either species and may also suppress weeds better.

Soybean Meal May Have Phytotoxic Potential When Used as a Nitrogen Source
(Melissa Pline and Jeanine Davis, N.C. State)

Soybean meal, which is sold most commonly as a livestock feed, is also used as a source of nitrogen in organic crop production. It has about 7% nitrogen that is relatively quickly available to crops. The meal is a waste product from soybean oil production. This experiment studied bell pepper production using plastic mulch and soybean meal. Amending the soil with soybean meal just before transplanting significantly limited the early growth of the plants. In addition, greenhouse studies showed that when soybean meal was sprinkled on the surface of germination media, the percent germination of small seeded vegetables (spinach, lettuce, carrot and radish) was reduced. These studies suggest waiting perhaps a week between applying soybean meal and planting, or thoroughly incorporating the meal rather than applying it on the surface.

Surround is Not Good for Control of All Pests
(Kathleen Delate et al., Iowa State)

Three strategies for managing squash bugs in winter squash production were tested: row covers; interplanting with buckwheat; and Surround kaolin clay. Row covers achieved the best control, while intercropping with buckwheat or spraying with kaolin clay had little effect.

Eric is MOFGA’s director of technical services. You can contact him at the MOFGA office or at [email protected] with your questions about organic farming and gardening.

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