Mycorrhizal Banks to Enhance Vegetable Yield and Reduce Water Quality Impairment by Mitigating Excessive Soil Phosphorus

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Commodities

Practices

• Crop Production: agroforestry, cover crops, cropping systems, nutrient cycling, nutrient management, pollinator habitat
• Education and Training: demonstration, on-farm/ranch research, participatory research, technical assistance
• Farm Business Management: feasibility study
• Natural Resources/Environment: biodiversity, carbon sequestration, habitat enhancement, hedgerows, hedges - grass, hedges - woody, riparian buffers, riverbank protection, soil stabilization
• Production Systems: agroecosystems, holistic management, organic agriculture, permaculture
• Soil Management: nutrient mineralization, soil analysis, soil chemistry, soil microbiology, soil quality/health, toxic status mitigation
• Sustainable Communities: partnerships, sustainability measures, values-based supply chains

Mycorrhizae can be an important component of agroecosystems. However modern agricultural practices, including some in sustainable agriculture, can impede mycorrhizal effects. Approximately 80% of crop plants harness mycorrhizal symbiosis to optimize nutrient uptake. Agricultures that till their soils inhibit this symbiosis. Furthermore agriculture often incorporates animal manures and composts which are enriched in phosphorus, causing excessive phosphorus levels to build up in the soil. Available portions of these phosphorus accumulations run off the land in spring snow melt and seasonal precipitation events, threatening water quality health. An innovative way to promote mycorrhizae and thus phosphorus use efficiency in tilled fields is to install mycorrhizae banks from which they can spread. The effectiveness of such a reserve will be tested in the Intervale farming community with a large bioassay. Essentially, mycorrhizal plants will be grown in a field, that is plowed twice a year, adjacent to a colonized bank. The number of mycorrhizal hyphae will be measured during the growing season to determine the rate of spread. Mycorrhizal densities, plant phosphorus uptake, harvestable yield, and water extractable phosphorus will be measured and correlated with distance from the bank. In addition, the mycorrhizae bank is designed with a diverse plant palette of native pollinator species, ranging from herbaceous to woody perennials. Woody biomass can be an effective accumulator of legacy phosphorus which can be removed from the agroecosystem through cyclical coppicing. Phosphorus removal by coppicing will also be measured.

We propose to help mycorrhizal colonization of tilled soils by providing “mycorrhizal banks” from where mycorrhizae can spread into fields and thus increase crop phosphorus efficiency.

Specific Objectives:

1. Test whether mycorrhizae spread into a field from the mycorrhizae bank

               This will be tested by extracting and counting mycorrhizae hyphae in the soil at different distances from the bank. This will give us information on an optimal spacing between banks. The hypothesis is that mycorrhizae are more abundant close to the bank but will spread further as time goes by.

2. Test whether plant phosphorus content varies with distance from the mycorrhizae bank

               Our hypothesis is that plant P decreases with distance from the bank and is positively correlated with soil hyphal counts.

3. Test whether water extractable phosphorus concentrations vary with the distance from the edge of the bank and whether it is correlated with mycorrhizal densities and phosphorus plant uptake.

               Our hypothesis is that mycorrhizal symbiosis will still be established in soils with excessive soil phosphorus. Hence, there concentrations of water extractable phosphorus will be lower closer to the mycorrhizal buffers.

4. Test how much phosphorus is in woody vegetation grown in the mycorrhizal bank.