Using Mycorrhizal Fungi to Improve Soil Health and Increase Yield in Organic Vegetable Farms.

The Lower Rio Grande Valley (LRGV) in deep-south Texas comprises of about 2.1 million acres of arable land. Low soil organic matter, poor drainage, and high soil pH are the major soil-based problems faced by farmers in the LRGV. In spite of these challenges, small/medium scale farmers have trended towards organic practices of soil improvement. There has been a pulse of commercial mycorrhizal products now available for farmers with products like microbial inoculants containing naturally-occurring beneficial soil microorganisms, now a trend in sustainable agriculture. Nonetheless, the research on these products is relatively sparse, with existing research not necessarily applicable to warmer subtropical climes of the southern US. For example, the ability of the non-native commercial fungi spores to colonize the plants and provide expected outcome is still questionable, especially in warm climates where there is a relatively higher diversity of soil fungi. Introduced fungi do not appear to offer much superior advantage to native species since they need to compete with the indigenous population of mycorrhizal fungi in the farm. There are some studies where crops fail to respond to the introduced mycorrhizal fungi. There are two principal ways of increasing mycorrhizal activity on farm: (1) inoculating with selected commercial mycorrhizal fungi and/or (2) promoting the activity of effective indigenous mycorrhizal fungi through cultural practices. Commercially available inoculum comes at a cost to farmers, a cost that presents a considerable obstacle without evidence of improved yield in subtropical farms. Goal of this project is two-fold: (1) to develop and test efficient mycorrhizal inoculum production system that avoids the costs of commercially produced inoculum and instead promotes native mycorrhizae; (2) compare the benefits of different systems and demonstrate them to farmers in the LRGV. This project is being conducted in three phases: Phase 1: Assessment of on-farm mycorrhizal spore density and diversity in the LRGV, and on-farm production and promotion of mycorrhizal fungi. Phase 2: Examine the impact of two different mycorrhizal treatments and the cultural practice of on- farm management of mycorrhizae on total yield of cash crops. We will also analyze soil nutrient status (chemistry), soil organic matter, as well as mycorrhizal colonization in the roots, mycorrhizal spore density and diversity in the roots. Phase 3: Extension, outreach and dissemination of the collected data.