Utilization of inoculum of AM fungi produced on-farm for the production of Capsicum annuum: A summary of seven years of field trials on a conventional vegetable farm

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. Seven years of field studies were conducted with five or six cultivars of bell pepper (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 US (159 mg kg(-1) soil). Seedlings were inoculated 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 response 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.