Comparing Vesicular-Arbuscular Mycorrhizal Colonization in Conventional versus Organic Strawberry Production Systems

Project Overview

GNC03-023
Project Type: Graduate Student
Funds awarded in 2003: $10,000.00
Projected End Date: 12/31/2004
Region: North Central
State: Minnesota
Graduate Student:
Faculty Advisor:
Dr. Emily Hoover
University of Minnesota

Annual Reports

Commodities

  • Fruits: berries (strawberries)

Practices

  • Crop Production: conservation tillage
  • Education and Training: focus group, on-farm/ranch research, participatory research
  • Pest Management: cultural control, mulches - killed, mulching - vegetative
  • Soil Management: soil analysis, soil quality/health
  • Sustainable Communities: sustainability measures

    Abstract:

    An on-farm comparison showed no differences in arbuscular mycorrhizal fungal (AMF) colonization between conventional and organic strawberry management strategies. However, the high variability of on-farm systems may make small differences difficult to detect. A research plot study comparing simulated conventional and organic strawberry management strategies found that fungicide and insecticide sprays did not affect levels of AMF colonization. However, organic mulch materials in the establishment year translated to higher levels of AMF colonization and root biomass than herbicide or hand-weeded groundcover management strategies.

    Introduction:

    Strawberries are herbaceous perennials and can be an important part of a sustainable agroecosystem. Matted row systems in Minnesota allow growers to utilize minimal disruptive tillage, establish long-term pest control strategies and enhance soil quality by maintaining a vegetative cover. Strawberries also provide the grower with economic benefits because labor is confined to a relatively short season, often before other crops mature.

    The current research on mycorrhizal associations is extensive yet inconclusive. The published literature repeatedly emphasizes the need for site- and crop-specific studies (Barea et al., 1993) to account for factors such as plant-fungus specificity and environmental adaptations of fungi. Many of the current studies have been conducted in greenhouses using inoculum to supply mycorrhizal fungi to the system. While these studies are effective means for gaining preliminary information, they are not representative of the highly complex interactions occurring in natural and agricultural systems. The potential benefits of mycorrhizae to sustainable agriculture have been repeatedly emphasized (Bethlenfalvay and Linderman, 1992; Gianinazzi and Schuepp, 1994) and warrant further research.

    Research which applies the current knowledge base and moves ahead to affect real changes in agricultural management practices and agricultural system functioning is the next step. This project provided an opportunity to evaluate mycorrhizal associations at the systems level to make a clearer assessment of the benefits conferred to plants, and the factors which affect these associations. Our work was partially conducted on working strawberry farms with an emphasis on grower participation. This set-up allowed us to evaluate the costs and benefits of managing for these associations in a realistic way, considering grower acceptance and farm profitability in addition to environmental quality.

    Literature Review
    The soil biology within a strawberry field is an important, yet poorly understood contributor to the health and productivity of the system. To understand the physical role of the soil, we must also be aware of the many microbiotic associations occurring in the soil and how these affect plant health and crop yield. Other SARE-funded projects have recognized the importance of studying the whole soil system, and the roles of microorganisms in that system (LNC00-175, LS00-110). Possibly the most prevalent soil-plant interaction is with mycorrhizal fungi. Most horticultural crop plants form associations with mycorrhizae, and the majority of these with arbuscular mycorrhizae (Barea et al., 1993). These associations have demonstrated numerous benefits to plants in both natural and agricultural systems. In strawberries, these associations have been shown to increase nutrient uptake (Dunne and Fitter, 1989), protect against soil-borne pathogens (Norman et al., 1996), and generally improve soil aggregation (Schreiner and Bethlenfalvay, 1995). Other putative benefits include protection against drought and salinity stress, and increased nitrogen fixation (Barea et al., 1993).

    However, much of the information on AMF interactions in strawberry crops remains incomplete. In other crops, soil type has been shown to affect fungal species diversity, fungal density, and mycorrhizal colonization (Land et al., 1989). Agricultural practices also affect the mycorrhizal colonies and symbioses. Many practices have demonstrated negative effects on fungal colonies, including belowground fumigation of white bean and soybean (Buttery et al., 1988), pesticide and fertilizer application to meadow plants (Titus and Leps, 2000), and tillage in maize (Hamel, 1996). Although there have been relatively few SARE-funded projects relating to mycorrhizae, several studies have investigated the relationship between mycorrhizae and management practices (LNC00-162, LNC91-041). However, this was the first SARE project to study mycorrhizae and strawberry crops, and to compare the dynamics of these interactions among conventional and organic management systems. Through proper management of AMF, the need for fertilizer applications and pesticide treatments may be reduced. These benefits represent a particularly promising addition to low-input, sustainable management plans (Azcon-Aguilar and Barea, 1997).

    Project objectives:

    1. Compare effects of various strawberry management strategies on AMF

      Increase grower awareness of soil system and its biotic components, focusing on AMF

      Facilitate grower discussions

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.