An interview with consultant Chuck Schembre on ecological methods for managing orchard floors
Acres U.S.A.: Orchard floor management is such an important topic; how worried should growers be about competition from grasses?
Chuck Schembre: Grasses are extremely important in any orchard system. My approach is to promote as many grasses as possible and to allow them to run their full lifecycles when possible.
Grasses are one of the strongest soil restoration species on the planet. They’re the most diverse in terms of their ability to grow in all types of conditions and climates; they’re very resilient, and they are highly efficient at producing root exudates. They’re probably the greatest carbon pump we have on the planet and are great at building soil organic matter. It’s root exudation and that liquid carbon pump, or photosynthetic carbon pump, that’s building more than 50 percent of the soil organic matter production underground. That’s the biological hotspot — the rhizosphere — and grasses probably create the most rich and robust soil microbial life.
One of the key species that associates with grasses is mycorrhizal fungi. For all perennial crops to become a resilient system, they need an abundance of mycorrhizal fungi — both ecto- and endo-. I believe grasses are a paramount species to create strong soil health and a resilient system.
Acres U.S.A.: So, how can growers keep grasses in the orchard as much as possible? And what’s the difference between a newly planted and an established tree in terms of that management?
Schembre: In orcharding, in particular out West, there’s a lot of fear about competition of any plant species growing in the orchard. In California’s Central Valley you see these bare orchards — nothing growing in them. There is a lack of understanding that grasses or any plant growing around a tree is actually supporting the tree’s health.
But yes — when we’re establishing a new orchard or a vineyard, it is very important to keep a good amount of vegetation-free area. I hate using the word “weeds,” but it is important to establish a weed-free area around the vine or tree during the first two years. It’s only when the tree or vine becomes four to five years old that you can really allow grasses or other plant species to proliferate around the base of it. It’s hard to juggle, because when we keep the tree row or vine row free of weeds, we’re not actually following the principles of soil health, which is to keep a living root in the ground, keep the soil armored, etc. We’re forced to contradict the principles of soil health for a period of time. We’re disturbing the soil and keeping it free of vegetation — which is our microbial carbon pump.
So, it’s just finding a balance. My approach with growers as a consultant, and in my own farming, is during the major part of the growing season to try to keep as narrow a strip as possible in the tree or vine row. But once we go into the dormant season, allow as much vegetation as possible to repopulate into that tree or vine row.
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