Soil Health in Orchards and Vineyards

By Macy Lacasse (summer student), Stephanie Vickers, Danny Jefferies and Kathryn Carter (OMAFA)

Soil health is a fundamental aspect of agriculture that significantly influences crop productivity, water and nutrient retention, disturbance resistance, biodiversity, and climate change adaptation and mitigation. For fruit growers, understanding and maintaining healthy soil is crucial to the long-term viability of fruit production and the implementation of sustainable farming practices for generations to come. So, what are some of the biological, chemical, and physical characteristics of healthy soils?

Definition of Healthy and High-Quality Soil:

Healthy and high-quality soil is characterized by good soil tilth, ensuring it is easy to work and supports root growth. It has sufficient depth to provide ample space for root expansion and water retention. The soil maintains a sufficient but not excessive nutrient supply, promoting plant growth without causing nutrient imbalances. A small population of plant pathogens and insect pests minimizes crop damage, while good soil drainage prevents waterlogging and root diseases. This soil harbors a large population of beneficial organisms, such as earthworms and microbes that enhance nutrient cycling and soil structure. Low weed pressure allows crops to thrive without competition. The absence of chemicals or toxins that may harm the crop ensures a safe growing environment. Furthermore, the soil demonstrates resilience to degradation and unfavorable conditions, maintaining its productivity and health over time (Gugino et. al, 2007).

Biological:

Biological activity within soil plays a pivotal role in maintaining its health and fertility. Microorganisms such as bacteria, fungi, and earthworms decompose organic matter, recycle nutrients, and enhance soil structure. A diverse and active soil microbiome can suppress plant diseases and pests, reducing the need for chemical interventions. For instance, mycorrhizal fungi form symbiotic relationships with fruit trees, improving nutrient uptake and increasing resistance to drought and pathogens (Sofo, Mininni, & Ricciuti, 2020).

Chemical:

The chemical composition of soil directly affects the availability of essential nutrients for fruit trees. Key soil nutrients include nitrogen (N), phosphorus (P), and potassium (K), along with secondary and trace elements like calcium (Ca), magnesium (Mg), and zinc (Zn). Soil pH, which measures acidity and alkalinity, also influences the nutrient solubility and uptake of plants (Singh, Brewer, and Lukas, 2023).

Regular soil testing can help fruit growers monitor nutrient levels and pH, allowing for the precise application of fertilizers and amendments. By managing soil chemistry effectively, growers can prevent nutrient deficiencies, improve fruit quality, and avoid environmental impacts such as nutrient runoff.

Physical:

Physical properties of soil include color, texture, structure, porosity, density, consistence, aggregate stability, and temperature. These properties affect processes such as infiltration, erosion, nutrient cycling, and biological activity. These properties can have a significant impact on the soil’s ability to hold moisture to withstand droughts (reducing the need for irrigation), as well as the soil’s drainage capabilities, which help with managing extreme rain events.

Having a good understanding of the physical properties of your soil (texture, aggregate stability, and bulk density) helps you to understand the limitations or advantages of your soils and how they impact irrigation practices, fertilization, and overall soil health.

How Can We Test for Soil Health?

The Soil Health Assessment and Plan (SHAP) is an Ontario-developed soil testing tool that helps farmers assess agricultural crop practices in conjunction with a lab analysis of soil health indicators (University of Guelph, 2023).

SHAP helps farmers address soil health issues with targeted management practices. It establishes a soil health baseline for monitoring and allows comparisons between different fields. SHAP includes risk assessment tools, in-field observations, and lab tests to identify challenges, as well as indexes for evaluating management practices.

As soil science advances, SHAP will evolve to incorporate new knowledge and methods.

Soil Health Assessment and Plan Guidebook – Field Crop News

Positive Impacts of Understanding Soil Health:

A thorough understanding of soil health can yield numerous benefits for orchards and vineyard management. Healthy soil enhances the nutrient and water availability for fruit trees, leading to better growth and potentially higher yields. By improving soil fertility and structure, growers can also reduce their reliance on synthetic fertilizers and pesticides, promoting more sustainable and cost-effective farming practices. Healthy soil is also more resilient to environmental stresses such as drought, heavy rainfall, and temperature extremes. This resilience helps to stabilize fruit production in the face of climate variability, ensuring a more consistent supply of high-quality fruit for consumers.

Effective management of soil health directly influences the availability of nutrients and water for fruit trees and vines. Healthy soil with good organic matter content and structure enhances water retention, reduces the need for irrigation, and ensures that trees and vines have access to water during dry periods. Similarly, a well-balanced soil nutrient profile supports optimal tree growth and fruit development, contributing to higher yields and improved fruit quality (DuPont, Granatstein & Sallato, 2020).

General Practices to Help Improve Soil Health:

• Avoid driving on soils when they are wet, as it can compress soils and reduce the infiltration ability of the soil.
• Mechanically loosening with a deep ripping tool during orchard/vineyard renovation to try to reduce the plow layer. Keep in mind that deep ripping may only mitigate compaction for one to two years if not combined with organic matter additions and reductions in traffic.
• Planting cover crops with strong taproots that penetrate compaction layers and can help increase organic matter and provide traction for traffic that needs to move in the orchard or vineyard.
• Monitor soil organic matter and consider adding organic matter (compost, manure, cover crops) can help reduce compaction and provide food for soil organisms.
• Consider measuring soil properties prior to planting an orchard and continue to monitor through the life of the orchard/vineyard. Conduct soil samples for nutrients every 3 years. Use regular petiole sampling to determine fertilizer needs.

Conclusion:

Soil health is a critical component of successful orchard and vineyard management. By focusing on the biological, chemical, and physical aspects of soil, fruit growers can create a more productive and sustainable orchard and vineyard environment. Investing in soil health supports the long-term viability of fruit farming. Stay tuned for upcoming articles on soil health testing and techniques to enhance soil health in orchards and vineyards.

References:

DuPont, T., Granatstein, D., & Sallato, B. (2020). Soil health in orchards. Soil Quality Information, 1-10. https://s3.us-west-2.amazonaws.com/treefruit.wsu.edu/wp-content/uploads/2020/11/23134102/EM120E_Soil-Health-in-Orchards.pdf

DuPont, S. T., Kalcsits, L., & Kogan, C. (2021). Soil health indicators for Central Washington orchards. PloS one, 16(10), e0258991. https://doi.org/10.1371/journal.pone.0258991

Singh, S., Brewer, L., & Lukas, S. (2023). Understanding soil health and biota for farms and gardens. Oregon State University, 1-12. https://extension.oregonstate.edu/catalog/pub/em-9409-understanding-soil-health-biota-farms-gardens

Sofo, A., Mininni A. N., & Ricciuti P. (2020). Soil Macrofauna: A key Factor for Increasing Soil Fertility and Promoting Sustainable Soil Use in Fruit Orchard Agrosystems. Agronomy 10, no. 4: 456. https://doi.org/10.3390/agronomy10040456

Visconti, F.; López, R.; Olego, M.Á. The Health of Vineyard Soils: Towards a Sustainable Viticulture. Horticulturae 2024, 10, 154. https://doi.org/10.3390/horticulturae10020154

Washington State University. (January 2023). Soil health in Washington vineyards. WSU. https://pubs.extension.wsu.edu/soil-health-in-washington-vineyards