Crop Productivity Boosters: Native Mycorrhizal Fungi from an Old-Growth Grassland Benefits Tomato and Pepper Varieties in Organically Farmed Soils

Project Director: Liz Koziol, University of Kansas

Project Overview

Soil health and nutrient management are key aspects of organically-managed farming systems, as is maintaining or improving crop yields. Soil microbes, such as arbuscular mycorrhizal (AM) fungi, form symbiotic relationships with plants thereby assisting with crop nutrient cycling. However, tillage is common on organic farms and this soil disturbance can disrupt AM fungal density and diversity. Adding microbial amendments, such as AM fungi from native biomes, may help alleviate this by adding beneficial microorganism density and diversity back into the soil. This study evaluated five tomato (Solanum lycopersicum) and five pepper (Capsicum annuum) cultivars transplanted with or without native arbuscular mycorrhizal (AM) fungi inoculation, and the resulting effects on tomato and pepper crop number and biomass, on a working certified-organic farm across one growing season in Kansas.

Farmer Takeaways

Inoculation with native arbuscular mycorrhizal fungi increased pepper number and biomass across the growing season.
‘Islander’ bell peppers and ‘Shishito’ peppers had the greatest response to inoculation, while ‘Milena’ bell peppers and ‘Jedi’ jalapeño peppers had smaller responses. ‘Mammoth’ jalapeño peppers did not respond to inoculation.
Inoculation with native arbuscular mycorrhizal fungi increased tomato number and biomass across the growing season, with no differences in response between tomato cultivars.

Project Objectives and Approach

To determine the effects of native arbuscular mycorrhizal (AM) fungi inoculation on crop productivity (crop biomass and number) over the growing season using five tomato and five pepper cultivars grown on a certified organic farm.

A hoop house experiment was conducted across one growing season on a certified organic farm in Lawrence, Kansas.
Tomato seeds were purchased from Johnny’s Selected Seeds and included the following: ‘Black Krim’, ‘Valencia’, ‘Brandywine’, ‘Green Zebra’ and ‘Striped German’. Seeds were sown in sterilized peat in a 72-cell tray in mid-February, and transplanting occurred in mid-April.
Pepper seeds were purchased from Speedway and included the following: Bell peppers ‘Islander’ and ‘Milena’ jalapeño peppers ‘Jedi’ and ‘Mammoth’ and shishito peppers ‘Mellow Star’. Seeds were sown in sterilized peat in a 72-cell tray in mid-March, and transplanting occurred in mid-May.
Treatments were arranged with crop cultivars planted as single rows down a length of 100 meters, with four blocks partitioned along each row. This resulted in six pepper or 4 tomato plants per treatment (inoculated or not inoculated). Treatments were spatially clumped to reduce cross-contamination.
Inoculation occurred using a native AM fungi with spores isolated from old-growth native prairie grassland near the farm. Cultures were grown in a sterilized sand+soil mix, and the inoculum was side-dressed by placing it into the crop transplant hole at planting time.
Once per week, tomato and pepper wet biomass were recorded from all plants in each block, as well as the number of tomatoes and peppers harvested.

Key Findings

Inoculation with AM fungi increased pepper crop number and biomass across the growing season, but this response varied by cultivar.

‘Islander’ bell peppers and shishito peppers had the greatest response to inoculation, while ‘Milena’ bell peppers and Jedi jalapeño peppers had smaller responses. ‘Mammoth’ jalapeño peppers did not respond to inoculation.
Across cultivars, pepper biomass in inoculated treatments was improved by 2-8% (per block of six plants) depending on harvest date compared to non-inoculated treatments, with an increase of 3.7% at final harvest (after 13 weeks).

Inoculation with AM fungi increased tomato crop number and biomass across the growing season, and this response was the same across cultivars.

Across the growing season and across cultivars, inoculated tomatoes showed 10% higher crop biomass and 20% greater crop number compared to non-inoculated treatments.

Resources

Koziol, L., & Bevre, J.D. (2023). Crop Productivity Boosters: Native Mycorrhizal Fungi from an Old-Growth Grassland Benefits Tomato (Solanum lycopersicum) and Pepper (Capsicum annuum) Varieties in Organically Farmed Soils. Microorganisms, 11(8), 2012.

Location

Kansas

Collaborators

James Bever, University of Kansas

Region

Plains

Topic

Soil Health, Crop Nutrient Management

Year Published

2023