Submitted to: Biological Agriculture and Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2012
Publication Date: 6/11/2012
Citation: Douds, D.D., Lee, J., Rogers, L., Lohman, M.E., Pinzon, N., Ganser, S. 2012. Utilization of inoculum of AM fungi produced on-farm for the production of Capsicum annuum: a summary of 7 years of field trials on a conventional vegetable farm. Biological Agriculture and Horticulture. 28:129-145. Interpretive Summary: Arbuscular mycorrhizal [AM] fungi are naturally-occurring soil fungi that form a symbiosis with the roots of most crop plants. The benefits that the plants receive: increased nutrient uptake from the soil and enhanced disease and drought resistance, make utilization of this symbiosis a potentially essential part of sustainable agriculture. Earlier, we developed a method for farmers to produce inoculum of AM fungi on their farms. Here, we studied the utilization of the inoculum produced on a farm in Kutztown, PA for the growth of green bell peppers on that farm for seven consecutive years. Plants were inoculated during the greenhouse growth phase and then transplanted out in the farm fields. Five or six different varieties of peppers were used each year. The inoculation process successfully produced seedlings infected by the AM fungi, and in some years resulted in increased growth of the plants during the greenhouse growth period. Only one variety, however, consistently showed a positive response to inoculation with respect to yield, likely due to the high nutrient status of soils of this farm, typical of farms in the Mid-Atlantic region. This work demonstrated the reliability of the on-farm inoculum production system and underscores the need to study different varieties of vegetable crops for their response to AM fungi.
Technical Abstract: Utilization of arbuscular mycorrhizal [AM] fungus inoculum has been encouraged as a way for vegetable farmers to better utilize the AM symbiosis. On-farm systems can economically produce inoculum that has been shown to increase the yield of specific crops. We conducted seven years of field studies with five to six cultivars of Capsicum annuum L. each year to transfer the on-farm inoculum production and utilization system to a conventional vegetable farm with high soil available P typical of the Mid-Atlantic region of the USA (159 mg kg-1 soil). We inoculated seedlings in the greenhouse with a mixed species inoculum of AM fungi produced on that farm. Performance of the inoculation treatment was evaluated based on growth response in the greenhouse and fruit production in the field. Colonization levels were typically only 3% of root length at the time of outplanting. Growth response in the greenhouse and yield in the field varied by cultivar and the two measures were typically inversely proportional. Overall mean fruit yield was not significantly different between inoculated and uninoculated plants, however cv. Boynton Bell exhibited a significant positive response to inoculation (9.1% ± 2.4%) over the years. The results of this seven year study illustrate the reliability of the on-farm method of AM fungus inoculum production, however the lack of a significant yield response for most cultivars studied reflects the current debate surrounding the functional role of AM fungi in high P soils.