Frequent cultivation prior to planting to prevent weed competition results in an opportunity for the use of arbuscular mycorrhizal fungus inoculum

Authors: Douds, David; Nagahashi, Gerald; SHENK, JOHN - Shenk'S Berry Farm

Submitted to: Renewable Agriculture and Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2011
Publication Date: 7/27/2011
Citation: Douds, D.D., Nagahashi, G., Shenk, J.E. 2011. Frequent cultivation prior to planting to prevent weed competition results in an opportunity for the use of arbuscular mycorrhizal fungus inoculum. Renewable Agriculture and Food Systems. 27:251-255.

Interpretive Summary: Arbuscular mycorrhizal [AM] fungi are beneficial soil fungi that form a symbiosis with the roots of most crop plants. The plants benefit from the symbiosis though increased uptake of mineral nutrients from the soil, drought resistance, and disease resistance. Better utilization of these fungi should be an important part of sustainable agricultural systems whose goal is to reduce chemical inputs. One way farmers can use AM fungi is to use inoculum that they can grow themselves on-the-farm. We demonstrated the potential benefits in crop growth that can occur due to inoculation using leek seedlings. Plants were inoculated during a preliminary greenhouse growth period, then transplanted into a field that had been repetitively cultivated to control weeds. Repeated cultivation is known to be harmful to the AM fungi already present in the soil. At harvest, the inoculated plants were over 2.5 times as large as the uninoculated plants. This research demonstrated the value of inoculation in targeted situations, and showed that inoculum of AM fungi produced on-the-farm can contribute to farm economic profitability.

Technical Abstract: Inoculation with arbuscular mycorrhizal [AM] fungi is a potentially useful tool in agricultural systems with limited options regarding use of synthetic chemicals for fertility and pest control. We tested the response of Allium porrum cv. Lancelot to inoculation with AM fungi in a field high in available P (169 ug g-1 soil) that had been repeatedly cultivated to control weeds. Seedlings were inoculated during the greenhouse production period with a mixed species inoculum produced on-farm in a compost and vermiculite medium with Paspalum notatum Flugge as nurse host. Inoculated and uninoculated seedlings were the same size at outplanting. Inoculated seedlings were over 2.5 fold greater in shoot weight and shoot P content than uninoculated seedlings at harvest. These results demonstrate the potential yield benefits from inoculation with AM fungi in situations where farm management practices may negatively impact indigenous populations of AM fungi.