Berm Building and Mulching for Water Retention

By Nana
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I come from a long line of people with soil under their fingernails from playing in the garden or in the fields. My father’s parents’ families were farmers for a couple of generations before him. He was a nursery owner, landscaper, an agronomist, crop adviser and farm consultant. I learned a lot by watching, listening to, and helping him.

To me, building berms around trees and mulching to hold onto moisture in the soil seem like no-brainers. But these are things a lot of people might not learn by growing up in the city. I realize some of the Capper’s Farmer readers might not understand the value of the practice. If you’re planting a LOT of trees, you’ll probably skip the berm/mulch chore, but if you only have a few, as we do, this is a great water saver.

We planted three olive trees last year, before we discovered how terribly allergic to them my husband is. I’m going to keep both the olives and the husband, but he’s getting allergy shots now. Curing olives has become a hobby (I get them from a friend until ours produce enough).

When we planted our trees, they each had a small berm around them, which creates a water well, for deep watering. Over time, berms wear down and erode. Goats, deer, Guinea fowl, and chickens all add to the drama. Any mulch we placed around them is gone and has been replaced by dried weeds.

I don’t know about other country folks, but at our place, we have piles: piles of manure, piles of old straw, piles of materials, and more. It gets a little annoying at times, but there seems to be a season for everything. When I decided to rebuild the berms and mulch the trees, I was able to get rid of some straw we’ve had piled at the end of our house for more than a year. That made me smile!

I put approximately 2 inches of straw in the wells around the trunks of each tree. If I’d had more, I would have made it 4 inches deep. I’ll add more mulch as needed throughout the summer and into fall. Water retention is my No. 1 reason for mulching. Weed control is the other reason.

It’s important that you don’t mulch with hay. Hay has seeds. Seeds will germinate. If I put hay around my olive trees, by the spring, the oats and wheat would be taller than my trees. Straw is the stalk that’s left after oats, barley and wheat are harvested for their grains. Hay is the stalks with seeds still attached and is used to feed livestock.

I watered my olive trees before starting the berm building project. Then I took our big wheelbarrow to a couple of piles of manure and shoveled it in. I use old manure that’s seasoned for at least a year. This is really important. Most fresh manure is too hot (high nitrogen content) and will burn or kill your plants and trees. Allergies aside, my husband doesn’t want to kill the trees. He’s looking forward to home-cured olives as much as I am.

I mixed equal parts horse/chicken manure and added water to moisten it. My chicken manure is probably equal parts sawdust (from a local furniture manufacturer), sand and manure scooped out of the coop a few times a year and piled where it can season or ‘mellow.’

All of my trees are planted on a slope so I don’t have to put the berm at the top of the tree well. If you plant on flat land, you will have to make an entire circle around your tree. Give your tree plenty of room around the trunk. If you place soil against the trunk, you can suffocate the tree. I gave my trees at least a foot of space between the trunk and the berm.

Once my berm is built and I’ve smoothed it out with my hands, I place more straw on the berm. This helps it hold its shape and keeps it from eroding easily; basically it holds together longer. They really need to last at least through the summer, and my hope is that they’ll last until next spring. I water it all down again, then water each tree until I fill the well that was created when I built the berm.

If you build your berms with aged manure, you are feeding them as you water because there’s really good stuff in the manure. You’ll notice some brown fluid running off your berm when you water it down. This is GOOD and your trees appreciate it.

So, plan on building (or repairing) your berms at least annually and adding mulch as needed. If you don’t have manure piles lying around, find out if you can get some horse manure from a local stable. Let it sit in a pile for at least six months. As I said, I let mine sit for a year. If you have to buy it at a home improvement store or nursery, ask the sales associate what brand/type is best for your project. I have no idea what you’d use.

If buying an entire bale of straw seems like a waste, find out if neighbors will go in on it with you. Or you can let the leftover straw sit somewhere in the yard. Cover it in the rain and you may be able to use it for a couple of years, as I’ve done.

**Some horse manure is contaminated with broad leaf weed killer applied to the hay the horses are eating. Recent studies show that some horse manure is toxic and deadly to plants because the herbicides pass through the animals’ digestive tract. I don’t know if there is a remedy to this. Research this to find out more.**

I hope you’ve enjoyed this blog about tree berms and mulching. A lot is going on at Nana’s Ranch these days, including a drought and the real fear that our well could dry up before the summer is over.

God bless you all.