USDA awards $1M grant to refine organic weed control method

Weeds are a major factor limiting yield in organic vegetable and other horticultural crop systems, and the lack of effective biological weed-management solutions is considered by experts to be a significant obstacle to the adoption of organic farming practices. Many organic systems deliver up to 34 percent less yield than their conventional counterparts, thus requiring more land to grow the same amount of food.

To address this problem, the U.S. Department of Agriculture has awarded a four-year, $1 million grant to a team led by plant scientists and an economist from Penn State to investigate anaerobic soil disinfestation, a microbial-driven process to manage weeds, to support transitioning from conventional to organic production systems.

“Anaerobic soil disinfestation — often referred to ASD — is emerging as a broad-spectrum biological soil treatment for the management of soilborne pests and pathogens, including weeds,” said research team leader Francesco Di Gioia, associate professor of vegetable crop science in Penn State’s College of Agricultural Sciences. “It is an ecological alternative to chemical soil fumigation. The method consists of incorporating easily decomposable organic amendments into the soil, followed by irrigation to saturation and soil cover with impermeable plastic.”

Soil saturation enhances the decomposition of organic matter, and the anaerobic conditions foster the accumulation of volatile fatty acids and other organic acids in amended soil that are toxic to weeds. The lack of oxygen suppresses weed seed respiration, and those anaerobic conditions result in changes in soil temperature and pH, which work synergistically with other factors to kill weed tissues that could propagate new plants.

The primary goal of this project, according to Di Gioia, is to increase the profitability and sustainability of organic vegetable and other specialty crop production systems and to facilitate the transition from conventional to organic production practices. This can be accomplished, he explained, by optimizing and integrating the use of anaerobic soil disinfestation as a biological weed-management tactic in specialty crops systems, while promoting soil health.

The project will include coordinated research activities, including on-farm demonstration trials to evaluate the efficacy of the tactic in suppressing key weed species in Florida and Pennsylvania, two states representative of the U.S. Northeast and Southeast regions.

“In addition to assessing the efficacy of anaerobic soil disinfestation in suppressing specific weeds, the project will allow us to investigate the impact of ASD on soil-plant nutrient dynamics, investigate the mechanism of suppression and examine the impact of the treatment on the soil microbiome,” Di Gioia said.

To ensure the viability of ASD, he added, team member Claudia Schmidt, Penn State assistant professor of marketing and local/regional food systems, will assess its economic sustainability.

“She will identify obstacles to adopting this new biological solution,” Di Gioia said. “She will oversee the economic analysis and assessment of the obstacles to adoption.”

This grant is part of an investment of nearly $121 million to advance research and extension activities that aim to solve key challenges facing specialty crops — including fruits and vegetables, tree nuts, dried fruits, and horticulture and nursery crops — and organic agriculture producers recently announced by the USDA. The investment includes $70.4 million to support specialty crop production research across the United States and $50.5 million to support farmers and ranchers who grow and market high-quality organic food, fiber, and organic products.