Determining if Beneficial Fungi Increase Tree Growth and Reduce the Need for Fertilization and Irrigation of Newly Planted Apple Trees.

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Commodities

• Fruits: apples

Practices

• Crop Production: fertilizers, irrigation, nutrient management
• Soil Management: soil microbiology

Orchardists increasingly plant orchards using dwarf trees with limited root systems.  Roots are injured when trees are dug at the nursery and subsequently planted.  Rising land costs and the need to return land to production reduces growers’ abilities to rotate orchard land into cover crops for more than a season. This lack of rotation increases the risk of concentrating apple pathogens in the soil.  Many growers establish orchards with irrigation and regular fertilization, but these approaches are costly, requiring synthetic or high levels of organic fertilizers, and large quantities of water in dry years. 

Many fungi species form associations with apple roots, and there are commercially available formulations that growers can apply to the roots at planting. Previous research found trees inoculated with fungi showed improved survival, growth, and nutrient uptake, and may make trees more resilient to drought. However, few trials have been conducted in commercial northeast orchards.

We will investigate if the addition of commercial mycorrhizal products to newly planted apple orchards, under varying levels of soil phosphorus, improves tree growth, survival, nutrient uptake, and water use efficiency, compared to naturally occurring fungi under various soil, climate, and management conditions found in the northeast. We will assess if fungal colonization, and therefore any subsequent benefits to tree growth, survival, nutrient uptake, and water use efficiency, vary between different apple varieties and rootstocks.

Three research sites will be conducted on commercial orchards in New York, New Hampshire, and New Jersey. We will inoculate 50 trees each with four commercial fungi products, with 50 trees serving as a control. During each of the three years, we will collect data on tree growth, survival, root colonization, root microbial community distributions, nutrient uptake, and water use. Two greenhouse studies will also be conducted. One study will determine the effects mycorrhizae have on drought stress on two varieties and four rootstocks. The second study will look at the effects mycorrhizae and three levels of P fertilization have on nutrient uptake.

A survey conducted in September 2022 showed grower interest in this work. When asked “Would you be interested in using mycorrhizal fungi when planting your new orchards/nurseries?”, 20 responded “Yes”, 1 responded “No”, and 32 responded “Yes, if there was more research documenting clear benefits”. This shows growers are interested in incorporating these materials into their plantings, but more data are needed before they implement these materials.  

Growers will play key roles in this project.  Field research is taking place at commercial orchards. Growers will apply treatments, maintain sites, and host field meetings. They will play key roles in developing outreach materials. Our advisory committee includes five commercial growers, who will be providing input throughout the course of the project through bi-annual meetings. 

While the general benefits of mycorrhizal fungi have previously been documented, more data is needed from field trials on commercial farms in the northeast before growers can be confident in applying these materials on their farms. The knowledge generated from our multi-state on-farm field trials and greenhouse work will provide growers the additional data needed to determine if inoculating trees prior to planting their orchard will provide tangible benefits to their commercial plantings. Positive results may allow them to decrease their fertilizer and irrigation inputs when establishing their future plantings while improving orchard productivity and profitability.