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

Arbuscular mycorrhizal fungi (AMF) have been proven to provide a wide range of benefits to plants including improved nutrient absorption, resistance to disease, pests, and drought (Smith and Read 2008), while inoculation with AMF has been widely reported to enhance plant growth and yield in both green house and field studies (Wu et al 2005; Adesemoye et al 2008; Baslam 2011).

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. This study examined different ways to promote and culture native fungi on-farm using sudangrass (Sorghum × drummondii), which when grown as a cover crop positively influenced a diversity of on-farm mycorrhizal fungi.

We conducted a greenhouse as well as field experiment to: (1) explore the native AMF community in the Lower Rio Grande Valley; (2) analyze the potential of on-farm AMF production; and (3) analyze the benefits of inoculating organic vegetable systems with AMF. Our preliminary results indicate that there was a very low population as well as diversity of AMF in vegetable farms of LRGV. Sudangrass increased the population of AMF spores in the field when used as a cover crop as well when used to produce AMF inoculum in bags. When treated with the commercial and on-farm produced AMF inoculum, there was a difference in the colonization by AMF in roots of peppers and onions but there was no significant difference in the total yield. However, it should be noted that AMF treated peppers flowered and produced fruit earlier than the control.

Objectives of this project are: 

1. Assess the status of mycorrhizal fungi in the organic vegetable farms in south Texas. 
2. Develop and test efficient mycorrhizal inoculum production system that avoids the costs of commercially produced inoculum and instead promotes native mycorrhizae.
3. Compare the benefits of different mycorrhizal inoculation methods and demonstrate them to farmers in the LRGV.