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

View the project final report

Commodities

Practices

• Crop Production: cover crops, organic fertilizers
• Education and Training: on-farm/ranch research, participatory research
• Natural Resources/Environment: biodiversity
• Production Systems: agroecosystems, organic agriculture
• Soil Management: organic matter, soil analysis, soil quality/health
• Sustainable Communities: sustainability measures

The Lower Rio Grande Valley in deep South Texas comprises of about 2.1 million acres of arable land. The upland soils are mostly deep, grayish-brown, and comprised of alkaline loams, silty clay loams and silty clay. 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. LRGV has the highest concentration of certified organic farmers in the state of Texas. Still, these farmers constantly address challenges of restoring the degraded soils while increasing productivity, without the tools commonly used by conventional farmers. Fertilizers acceptable for organic production usually have a low nutrient analysis and are made up of larger, insoluble molecules that take time to be broken down into forms usable by the plant. Thus, they need to be applied in larger quantities than conventional fertilizers to obtain the same nutrient value leading to a higher cost per unit of nutrient than synthetic fertilizer sources.

Soil chemistry has become the common metric of soil quality. However, soil biology is increasingly considered when managing soils, with recent research suggesting below ground soil ecology is an integral face in sustainable soil management. Based on these findings, 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 climates of the southern U.S. For example, the ability of the non-native commercial fungi spores to colonize the plants and provide expected outcomes 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. Furthermore, farmers frequently grow crops highly dependent on mycorrhizal fungi such as peppers and corn (common in the LRGV), do so following non-mycorrhizal dependent brassica crops, which reduces the rate of mycorrhizal infection. Thus, farmers have to continuously inoculate their farms to receive the benefits of inoculation, which is both expensive and sometimes discouraging. Organic growers in the LRGV have limited knowledge on the benefits of using soil microorganisms, and have voiced concern of a lack of relevant available information. As such, on farm research and integrative extension activities are important aspects of both understanding and promoting the use of beneficial soil microbes as an appropriate tool for maintaining soil fertility for organic and transitioning farms in this region.

This study will provide baseline information for the practical use of mycorrhizal fungi in farms. It will provide the necessary foundation to promote sustainable agriculture by optimizing plant-soil-microbe interactions.

The goal of this project is two-fold:

• To develop and test efficient mycorrhizal inoculum production system that avoids the costs of commercially produced inoculum and instead promotes native mycorrhizae;
• Compare the benefits of different systems and demonstrate them to farmers in the LRGV.