Soil health is a term that we are familiar with, but what does it mean? It helps our understanding if we look at the soil as a living and life-giving resource. Soil is not inert, it is teeming with bacteria, fungi, and microbes that are part of a symbiotic relationship that sustains plant life. According to Kathy Merrifield, retired nematologist at Oregon State University, “A single teaspoon of rich soil can hold up to one billion bacteria, several yards of mycorrhizae fungal filaments, several thousand protozoa, and scores or nematodes,” (OSU Extension Unit, 2010). Earthworms are the giants of the living soil jungle, visible, and a sign of healthy soil. Mycorrhizae, however, is best seen under a microscope. Mycorrhizae are the fungi that physically connect with the plant roots. The plant feeds the mycorrhizae with sugar and carbon through photosynthesis and in return, the mycorrhizae feed the plant with water and nutrients from the soil through its wide reach across and deep into the soil. The soil must be kept undisturbed, covered with diverse plants, and healthy so that the soil microorganisms can thrive and provide symbiotic support for the grower’s vines or trees.
The USDA defines soil health as the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans. Healthy soil gives us clean air and water, bountiful crops and forests, diverse wildlife, and beautiful landscapes. (USDA.gov) The USDA refers to four main principles for soil health:
⦁ Maximize the presence of living roots
⦁ Minimize disturbance of the soil
⦁ Maximize soil cover
⦁ Maximize diversity, (USDA.gov).
The third principle, maximizing soil cover, is a practice that naturally drives the other three principles. By growing cover crops there is a presence of living roots, minimized soil disturbance, and maximized diversity. A cover crop is grown to cover the soil, to build a soil surface armor. It may be incorporated at some stage for soil enrichment. It protects the soil from the sun, wind, and water erosion, especially for vineyards on sloping terrain. Cover crops suppress unwanted weeds and increase the nutrient content of the soil, improving yield potential, attracting pollinators, and providing habitat for beneficial insects and wildlife, (USDA.gov).
Different cover cropping practices may vary according to crop vigor, maturity of plants, water availability in the soil, and pest management practices.
⦁ Annually seeded and tilled cover crops, planted in the fall and then grown until spring and then mowed and tilled into the soil
⦁ Annual cover crop species that reseed themselves on an annual basis, such as clovers and grasses, provide permanent soil cover
⦁ Perennial cover crops, such as ryegrass, and orchard grass, provide permanent soil cover
⦁ Native grasses, managed by mowing
Cover cropping in vineyards and orchards is practiced by several growers and we are likely to see more adoption as environmental and cost pressures increase. It can be an alternative to tillage to remove weeds (soil disturbance) and reduce the use of herbicides.
For the grower, It requires careful selection and management as the cover crops will compete for nutrients and water. There is the additional cost for the grower for cover crop seed, seeding equipment, and the seeding operation, however, this can be offset by the reduction in herbicide cost while bringing the satisfying knowledge that the practice is supporting the long-term health of the soil, our living, and life-giving resource.
At Bluewhite, we aim to ensure that we support the grower's cover crop practices through autonomous mowing solutions and precision herbicide applications.
%20(1).png)
Cover crops in a California vineyard.