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Home HortScience Native Plants Prove Sustainable Cover Crops for Strawberry Production
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AMES, IA--Strawberry growers know that continuous production of a crop on the same site can cause weeds to multiply and pathogens to accumulate in the soil. Additionally, continuous tillage to remove weeds breaks down soil particle size and causes compaction, resulting in reduced crop vigor. All of these factors lead to decreases in crop yields and translate to economic losses for strawberry producers. A long-term study from researchers at Iowa State University found that growing cover crops before planting perennial fruit crops can alleviate the buildup of weeds and pathogens in the soil and can help to maintain soil structure.

According to scientists Dennis Portz and Gail Nonnecke from the Department of Horticulture at Iowa State University, controlling weeds is difficult in large-scale strawberry production because not all weed species are controlled by herbicides. "Chemical inputs such as methyl bromide have been used since the 1960s in strawberry production to reduce the impact of weeds and pathogens, but the use of methyl bromide was significantly restricted under the Montreal Protocol and U.S. Clean Air Act," the team noted. Portz and Nonnecke designed a 10-year study that featured rotation with cover crops as an alternative management practice in strawberry production. Published in HortScience, the study includes recommendations of three "superior" native plant cover crops for use in sustainable strawberry production.

The researchers established and maintained plots for 10 years of seven native plants used as cover crops. The plots were located on a site that had been used for strawberry production for the 10 previous years. Cover crops included blackeyed Susan, sorghum Sudangrass, marigold, big bluestem, perennial ryegrass, switchgrass, and Indiangrass. Plots featuring continuous strawberry planting or continuous tillage were also included in the study. "We designed this study to evaluate weed populations by type and biomass and to compare plant density and strawberry yield in plots after long-term continuous tillage, continuous strawberry, or growth with monoculture covers," the researchers noted. "We hypothesized that plots established in cover crops or plots of continuous tillage would reduce weed populations and have greater strawberry plant density and yield compared with plots of continuous strawberry production," they explained.

Experiments were conducted from 1996 to 2008 at the Iowa State University Horticulture Research Station. The researchers ended the treatments in 2005, when the plots were planted with 'Honeoye' strawberry in a matted row design. The team then evaluated the effectiveness of soil pretreatments in reducing weed populations and enhancing strawberry production for four growing seasons by quantifying weed growth by type and biomass and strawberry plant density and yield.

Results confirmed the authors' hypothesis, showing that rotation with cover crops and continuous cultivation before planting strawberry generally reduced weed populations and increased strawberry plant density and yield compared with continuous strawberry plots. "Our findings showed that sorghum Sudangrass (Sorghum bicolor), switchgrass (Panicum virgatum), and big bluestem (Andropogon gerardii Vitman) are superior cover crops for use in rotation with strawberry, and their use may reduce soil deterioration by avoiding tillage," the authors concluded.


The complete study and abstract are available on the ASHS HortScience electronic journal web site:

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at


Original Article:

Rotation with Cover Crops Suppresses Weeds and Increases Plant Density and Yield of Strawberry
Dennis N. Portz and Gail R. Nonnecke
HortScience 46:1363–1366. [Abstract][Full Text][PDF]

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