Assessing Anaerobic Soil Disinfestation for Improving Weed and Soilborne Disease Management in High-tunnel and Open-field Salad Green Production

View the project final report

Commodities

• Vegetables: greens (leafy), greens (lettuces)

Practices

• Crop Production: high tunnels or hoop houses
• Pest Management: integrated pest management, physical control
• Production Systems: organic agriculture
• Soil Management: composting

In response to national and local consumer demand, organic crop production in Florida has expanded during the last decade. In recent years, high-tunnels have emerged as a protected production system increasingly used by Florida organic growers because of their utility for season extension of high-value vegetables and improvement of produce quality. As organic production in high-tunnel systems continues to expand, research is warranted to guide producers in terms of pest and nutrient management. One method which has proved effective against several soilborne diseases across a wide range of horticultural crops and environments and shows promise as a weed management strategy is anaerobic soil disinfestation (ASD). ASD is a preplant method based on creating anaerobic soil conditions by incorporating labile carbon sources, irrigating to fill the soil pores with water, and covering the soil with a gas impermeable barrier. ASD promotes soil microbial shifts toward facultative and obligate anaerobes which produce short-chain organic acids and volatile compounds that are likely toxic to and inhibit weed seed germination. While previous studies have focused on disease management and the underlying mechanisms, limited field studies have investigated the effects of ASD treatment on soil and crop nutrient dynamics as well as ASD for managing weeds in high-tunnel systems.   

To our knowledge, limited field studies have been conducted to determine the impacts of ASD soil treatment on baby leafy green production and soil nutrient dynamics in organic high-tunnel systems. Organic fertilizers are commonly applied preplant in organic baby leafy green production. While the nitrogen (N) application rate for growing organic baby leafy greens is yet to be determined in Florida sandy soil conditions, the influence of preplant N rates through organic fertilization on the ASD soil treatment with respect to anaerobic condition development and crop and soil nutrient dynamics as well as crop performance also needs to be evaluated. This study examined different preplant N application rates involved in the ASD treatment in organic high-tunnel and open-field systems for developing recommendations on ASD application in production of direct seeded baby leafy greens. Based on linear and nonlinear models applied in each season, the optimum N application rate associated with ASD soil technique and production of baby leafy lettuce in HT and OF systems ranged from 136 kg N ha^-1 to 233 kg N ha^-1. Within this range, yield was not reduced compared with a reference N rate based on conventional commercial production, while limiting negative effects on lettuce color and phytochemical quality attributes at harvest. Project findings contribute to improving ASD as an environmentally-friendly method for soilborne pathogen, weed and nutrient management in organic production systems. 

Based on responses provided by participants in an online webinar, 100% or respondents indicated they are 'somewhat or extremely likely' to implement ASD as an integrated pest management plan. Similarly, 75% or respondents indicated they are 'somewhat or extremely likely' to transfer the knowledge and resources gained during the webinar. Moreover, 93% of farmers who participated in our field day indicated that they are 'somewhat or extremely likely' to transfer the knowledge and resources gained, while 86% of participants indicated they are 'somewhat or extremely likely' to consider using eco-based practices including ASD for managing pests. 

With the long-term goal of developing cost-effective and environmental-friendly ASD application for improving organic baby leafy green production systems, the specific objectives of this study included:

Objective 1: Assess the impact of N application rate on soil cumulative redox potential in ASD-treated soils.

Objective 2: Assess the ASD soil treatment impact on soil nutrient dynamics in high-tunnel and open-field systems. 

Objective 3: Compare different N application rates for baby leafy green production under ASD treatment in high-tunnel and open-field systems.