Investigating the effects of excess phosphorus on soil-plant-insect interactions in organic cropping systems

Monday, November 11, 2024

9:00 AM – 9:12 AM MST

Location: Phoenix Convention Center, 131 C, PCC

Presenting Author(s)

CS

Carly Sharp

Graduate Research Assistant
University of Georgia
Athens, Georgia

Co-Author(s)

WS

William E. Snyder

Professor
University of Georgia
Athens, Georgia
CB

Carmen Blubaugh

University of Illinois
Champaign, Illinois
KC

Kate Cassity-Duffey

Assistant Professor
University of Georgia
Athens, Georgia
AC

Anny Chung

Assistant Professor
University of Georgia
Athens, Georgia

Phosphorus is an essential nutrient for crop growth and development, but in excess may exacerbate insect pest pressure in agroecosystems. While high levels of phosphorus is a soil characteristic of the vast majority of cropping systems, remarkably little is known about how surplus phosphorus alters agroecological communities via both bottom-up forces, such as plant defenses, and top-down forces, such as insect predation. Filling this knowledge gap is critical for farmers to develop sustainable fertility management strategies while mitigating the environmental harms of phosphorus runoff into water bodies. In order to explore how surplus phosphorus affects weed and insect-pest pressure in agroecosystems, we manipulated six combinations of two compost fertilizers to create a gradient of phosphorus on a certified organic production area within the University of Georgia’s Durham Horticulture Farm. Zucchini (Cucurbita pepo) were our crop of focus due to their economic importance and challenging weed and insect-pest problems. We found that surplus phosphorus did not directly increase weed growth but did decrease foliar-feeding omnivore abundance and predation of herbivores. However, the overall effect of herbivory was not critical in this system as herbivores did not significantly reduce yields. Our results suggest that soil phosphorus is an important mediator of top-down control of herbivores and, in abundance, may decrease crop health and production.