Location: Sustainable Biofuels and Co-products Research
Project Number: 8072-12000-014-002-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Aug 1, 2021
End Date: Jul 31, 2025
Objective:
Arbuscular mycorrhizal fungi are beneficial symbionts of plants which enhance the uptake of nutrients and water from the soil, increase growth, and reduce the susceptibility to disease. Intentional inoculation of crops with arbuscular mycorrhizal fungi contributes to agricultural sustainability by reducing the chemical inputs needed for crop production. Prior field trials using mixed-species arbuscular mycorrhizal fungi inoculum, produced on-farm, have demonstrated yield increases of up to 15% from inoculation of a variety of crops, including, strawberries, potatoes, sweet potatoes, leeks, peppers, and eggplant. Commercial inoculants are also available; however, the options for formulations are limited, and such products typically contain only one or a few species of commonly-produced fungi. This project will characterize the ability of different species of arbuscular mycorrhizal fungi isolated from field soils to colonize the roots of crop plants, and the relative impact of individual species and mixtures of species on crop yield and nutrient quality.
Objective 1. Determine the impact of arbuscular mycorrhizal fungi inoculation on crop yield and mineral nutrient quality of potatoes and black beans. Controlled trials will use sterilized soil/potting medium to which the mycorrhizal fungi inoculum will be added. Yield will be analyzed based on mass (beans and potatoes) and grade (potatoes), and mineral nutrient content will be analyzed from dried plant tissue.
Objective 2. Develop on-farm production methods for arbuscular mycorrhizal fungi inoculum that are amenable to mechanical application. While the current method of producing inoculum in mixtures of vermiculite and compost is suitable for incorporation into trays for sowing vegetable starts, it is not amenable to most types of field application by machinery. A crushed and sieved mixture of natural zeolite within a size range that is suitable for in-furrow granular field application will be evaluated as a substrate for supporting growth of high-density fungal inoculum.
Approach:
Objective 1. Potatoes will be grown on raised benches in 9-gallon grow-bags filled with a sterilized mixture of soil, compost, and perlite (3:1:1), amended with 5,000 spores per bag of different arbuscular mycorrhizal fungi spores per treatment, or uninoculated controls. The mycorrhizal fungi treatments will consist of Claroideoglomus etunicatum, Funneliformis mosseae, two treatments of Rhizophagus irregularis (one treatment of inoculum produced on farm, one treatment of commercial inoculant), and a mixed-species indigenous population. Two varieties of potatoes will be grown, one yellow and one purple. Five replications will be tested for each treatment/potato variety pair. Plant nutritional status will be analyzed by collecting selected leaves at flowering. Yield and grade of tubers will be measured at harvest. Colonization of the roots will be assessed by staining/microscopy and molecular methods.
Black beans will be grown on raised benches in 0.7-gallon pots filled with a sterilized mixture of soil, peat-based potting mix and turface (2:2:1), and amended with 2,000 spores per pot of different arbuscular mycorrhizal fungi spores per treatment, as well as uninoculated controls. Ten single-species accessions of AM fungi will be selected, plus a mixed-species population isolated from field soil. In addition to the inoculation with fungi, all plants will be inoculated with Rhizobia to enhance nitrogen fixation. Twelve pots (four plants per pot) will be grown per treatment and, for sampling each treatment, these will be equally divided into three replicate groups. Plants will be watered daily, and fertilized once per week with 1X Hoagland’s Solution containing 0.01X phosphate. Leaf samples will be collected at flowering for plant nutrient analysis. At maturity, pods will be pooled among replicate group for yield determination. Seeds will be dried and finely ground, then analyzed for protein measurement and L-ergothioneine content. Colonization of the roots will be assessed by staining/microscopy and molecular methods. The entire experiment will be repeated on a second planting date during the 2021 growing season.
Objective 2. Inoculum grow bags will be set up side-by-side using the established substrate (3 parts vermiculite : 1 part compost) as well as mixtures of zeolite with compost or zeolite fertilized with fish hydrolysate on raised benches. A mixture of 3 parts zeolite : 1 part compost will be tested, as well as straight zeolite fertilized biweekly with a 15-1-1 organic fish hydrolysate fertilizer. Root samples will be collected for staining and molecular analysis. The bags will be left outdoors to be winter-killed and the contents of the bags will be homogenized prior to conducting spore isolations and molecular analysis. For successful treatments, the roots, as well as any particles larger than 1/8” will be removed by sifting. Inoculum will be utilized by one or more cooperators using in-furrow delivery of the granular material.
