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Cover crops for...established orchards

Posted by Josh Willis 
Cover crops for...established orchards
September 19, 2021 07:52PM
When I read about cover crops in orchards, it is often in the context of establishing and orchard, i.e., prior to fruit tree planting. What are your best on-going practices for orchards with already established trees -- do you cover crop in the fall (or whenever your zone's late season)?

My underlying question: Is cover crop competition for nutrients/water an issue with established trees (either semi- or dwarf)? Or Is this nutrient competition a good thing, to help fall buds harden off?

The covers that I'm thinking of here: Legumes such as Red or Crimson Clover, or even Sweet Yellow Clover (not as good for mycorrhizae development, but it does have deeper taproots, along with some pretty yellow flowers : ), Oats, Vetch, Tillage Radish (also great deep taproots, but also is described as a scavenger of nutrients -- does this compete with established trees?).

Or...

Do y'all stick to grasses + wildflowers + herbs for understory development?

Earthworks
Zone 7a in West-Central MD
Re: Cover crops for...established orchards
September 20, 2021 04:34PM
I'm just beginning an understory cover crop rotation in established plantings too. All my trees have been planted within the last 5 years, though, so they're still young. And I was in a hurry to get the first rounds of plantings in the ground, so I didn't take the time I should have to prep beds. Anyway...

This summer, after shallow tilling between trees and along the edges of rows, I tried planting a clover mix with buckwheat. Unfortunately, it didn't work too well. I want to establish a no-till regimen, so I spent quite a bit of time hand-pulling the weeds that grew up with the clover and then mulching with cut grass to smother what remained growing.

Following that, just at the end of August, I planted bell beans as a fall/winter cover. That went fine, but many of the bean sprouts were also smothered by the grass mulch. So I'm looking at replanting beans in the sections that didn't fill in. No problem, except placing the bean seeds correctly spaced in rows takes more time and effort than just scattering seeds like I could with oats or rye.

Now, then, I'm rethinking my plans for 2022. During the summer months, I plan to stick with buckwheat, sowing multiple successions of seeds to bulk up and improve the tilth of our clayey soil. Then next fall I'll do oilseed radishes to further break up the soil. In subsequent years, I'll start a fall/winter rotation of oats, rye, radish, and bell beans. That's the plan anyway. It's based on book-learning, though, so real-world experience may have its own lessons to teach me.

I'm not too worried about competition for water and nutrients shorting the apple trees of either. After all, the idea of covers/green manures is to keep the nutrients in the immediate vicinity of the crop trees. As long as you're letting the covers rot in place instead of taking off cuttings for mulch elsewhere, humus levels will improve over time allowing the soil to retain moisture/nutrients from the surface to lower and lower depths.

Rather, my concern is interrupting the biodiversity of the understory around and adjacent to my trees. I know M. Phillips talks quite a bit about balancing the life systems in the orchard by mowing (with a scythe) infrequently, and not letting such things as "weeds" bother your sense of aesthetics. The idea as I understand it is to maximize biodiversity, which should give the good insect predators a favorable habitat to hunt the damaging pest insects. But other growers I've read and talked to praise the benefits of planting a succession of no-till covers in raised beds. I'm wondering, therefore, if getting so intensive about planting a succession of green manures in the tree rows could backfire by encouraging a pest that takes advantage of the constantly changing soil surface.

One other thing I should mention, I keep the immediate vicinity of the trunks of my trees free of any competing plants (aka weeds, whether of the volunteer or seed-tossed variety.) Easier said than done, of course, but between pea gravel and hand pulling a couple times a year I can keep a circular zone about 3 feet in diameter around the trunk competition free.

Craig Bickle
Hap Woods
Zone 6a
East-Central Ohio
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