Problems with sheet mulch/ farm update

We have installed lots of sheet mulches on the Lakewood farm. Sheet mulching involves laying an overlapping layer of cardboard to smother weeds, and then piling on a foot or more of organic matter, ideally weed free, and with a balanced ratio of nitrogen to carbon. There are lots of benefits to this: less weeds, more organic matter, and, after the first year, less work, since the beds are never tilled again. For more information, see this post.
However, we have discovered two potential problems with sheet mulching.
First of all, sheet mulch does NOT stop bindweed. Those long twisting roots easily wend their way around the cardboard and through every crack, to emerge triumphantly at the surface. However, nothing else really kills bindweed either, and sheet mulch at least makes bindweed easy to pull. And the sheet mulch killed off the grass, thistles, dandelions, mallow, and other weeds on our site fairly well.
The second problem is more serious. When we planted the tomatoes, we just opened a hole in the mulch, stuck the tomato in, and pushed the mulch back together. Some of the beds were full of a light, fluffy mixture of grass clippings and mulched leaves. We then got a lot of rain, and occasionally people would step on the beds (our paths are not that well defined.) The mulch compacted and sank. Soon the tomato root balls were sticking out of the mulch, where the peat in the potting mix acted like a wick to dry out the roots. The fact that the grass clippings were very porous did not help matters any. We first noticed the problem when a lot of the tomatoes looked sick, with curled and yellowing leaves on a hot day.
Hopefully, we have solved the problem by laying a layer of rough compost from the pile we built last year over the beds. This will cover the root balls and hold water.
So, if you want to build a sheet mulch:
Don’t expect it to kill bindweed,
Try to mix dried grass clippings with other, more compact and water retentive material,
Lay the mulch much thicker than you think necessary, and plant deeply,
Carefully pack mulch over the root balls of transplants,
And ideally, build the beds in the fall, so they can decompose and compact over the winter.
The tomatoes in our hugelkulture/ sheet mulch hybrids are doing splendidly so far. I will continue to report on the success or failure of our systems over the next year. And now we will know how to avoid this problem for the future.
We are almost done planting. We have also got a fence built on the perimeter of the property, set up plant supports, and done a lot of weed mowing on the site over the last few meetings.



notes from the work meeting, March 15th

We got one length of the wire fence up, which runs across the width of the property. It should keep out rabbits and groundhogs, and, with the addition of an electric wire, it will help keep out raccoons and squirrels. We still need to deconstruct and replace the fencing on the other three sides.
The fruit trees have now been ordered. They should arrive in the first week of April.
We got a lot of work done on the next set of planting beds. These will be hugelkulture/ raised beds. We are digging down about six inches, and then piling on lots of sticks, putting the dirt and sod on top of them, and layering on leaves, manure and wood chips. It will basically be a big thick sheet mulch. Since they are being built on a slope, we will edge the downhill side with rocks to form a sort of terrace. Unlike our last hugelkulture, it will not have a deep trench in the center, and it will be under two feet deep.
We are still removing trees and brush along the bottom of the property, generating firewood, and piles of sticks for hugelkultures.
There are two problems with our greenhouse. The beds tend to dry out too fast, so the batch of lettuce we planted germinated erratically. We will be solving this with a combination of more watering, clay seed balls, and self watering planters. And the entrance does not close well. So we will be attaching weights to the bottom of the flap door, and installing a PVC pipe and clamps along the vertical edge. However, it is much warmer inside than out, and the automatic vent seems to be working well.

Notes from the meeting of October 28th

This meeting was held at our Lakewood farm site. Despite the wet and cold weather, we got a lot of work done. We finished our second hugelkulture. This one was wider, longer, and a bit taller than our first one, and was dug deeper into the ground. This should help it hold more water. In arid climates, hugelkultures are a balancing act. The surface dries out faster than a flat bed. However, the core holds a lot more water than a ordinary flat bed. So, they should be heavily mulched, and contain more core than surface area. One giant mound seven feet high and thirty feet long would work better than many smaller ones. We would need heavy machinery to move that much soil. So we are building them a reasonable size for hand work; about four feet high, with a trench about a foot deep, and a width of five feet. We mulched it with a layer of wood chips, and then a layer of leaves. We also added coffee grounds and manure to the various layers, to add a little nitrogen and improve the water holding capacity.
Leaves are a good top mulch in a desert area; they shed water, which then runs between them and into the soil. Then, due to the waxy nature of the leaf, the water can not easily evaporate into the air again. Wood chips and manure can hold water, but can also slowly release it to the air. So we hope to top all of our sheet mulch beds with leaves eventually.
We are still working on ideas for our sign. It will probably contain our logo. See our Logo here.
At our last meeting, we dug up a short piece of I-beam. So we decided to do a full heavy metal test, as well as our lead test, to find any contamination in the fill on our site. The results of this should be back in a few weeks. Even if there is some heavy metals in the soil, we can continue to use the site, though we may have to adapt in various ways.
We also discussed our focus for the farm site, and came to the conclusion that we should concentrate more on things members would find it difficult to do in their yards; the greenhouse, fruit trees and bushes, rare perennials, animals, aquaponics, seed raising, and staple crops. And we are hoping to schedule various social events—  a traditional blessing of the land for instance, or a potluck dinner in honor of a Saint’s feast day.
We have bought a membership with Seed Savers Exchange. This will enable us to purchase heirloom seeds from their yearbook, which contains more than twelve thousand varieties.

Notes from the meeting of October the 23rd

This meeting was held on our farm site in Lakewood. We continued work on our second hugelkulture, and as usual unearthed more rocks and other stuff. The hugelkulture is now a mound of sticks and small logs. We have been sifting manure and coffee grounds into each layer as we build it, to help trap more water. At the next meeting we will add about three more feet of wood, and then top it off with layers of manure, soil, and wood chips.

We discussed ideas for our sign, and other ideas for future land development. And we got fluorescent tape and reflectors put up around our work area, to warn people and to avoid damage to the beds.

I have been researching hugelkultures a little more, and I have found that in a dry climate, large hugelkultures work better than small ones, since there is a balancing act between the core, which holds more water than a flat bed, and the mound surface, which tends to dry out faster that a flat bed. The small mound has too little core and too much surface area. So we will be building our hugelkultures larger then at first planned.

I have also found that bone char is the best way to supplement our soil’s phosphorus levels. Bone meal, phosphate rock, and soft phosphate tends to be unavailable in this pH, and the manure we are getting may be too leached. It is also a very dilute source. I got some advice from a more experienced permaculture gardener. Here is what he said:

(This comes form the Permies forum, which is a good source of information about various permaculture topics. However, I disagree with many of the philosophical and moral opinions voiced.)

“Phosphorus is a tricky element to work with; if the pH is below 6, it gets fixed by iron and aluminum, if it gets above 7.3, it gets fixed by calcium. However, plants and their beneficial fungi can be persistent and un-fix the phosphorus, perhaps with some acidic or basic root exudates and enzymes, depending on what is needed. It’s unlikely that phosphorus is completely absent from soil, all sorts of critters dropping dead and decomposing provide a fairly constant source from above. The big question is the availability, and that’s where things like bone char can help tremendously. A piece of burnt bone, once colonized by mycorrhizal fungi, can be an oasis of phosphorous in an otherwise phosphorus-fixed landscape.”

So, now I just have to find a source of bone char. We could make it ourselves, and we might do that, a little at a time. However, to get things started, I might buy some, if I can find a source without too much shipping costs involved.

Notes from the meeting of October the 17th

This meeting was held on our farm site in Lakewood.

We got another hugelkulture started at this meeting. At present it is a large half dug hole, with a pile of cut up brush next to it. We hope to finish it next time.

Also, we found it is very hard to build hugelkultures with our current number of members. The amount of ground covered each time is very small with this technique, whereas sheet mulching is faster, letting us compete more beds before Winter sets in. We probably will not build any more of them this autumn unless we can find some more local members. (Our membership is scattered across the Metro area.)

One of the reasons that hugelkulture building is so difficult here is that there are a lot of rocks in the soil, some of them very large. These take a long time to move, with only a small space gained for each. They will, however, be very effective at forming warm microclimates once we get them out.

We could, of course, do sheet mulch beds instead of hugelkultures. However, hugelkultures have a lot of benefits, particularly on this site.

And it would be easier to build hugelkultures at ground level, and pile imported top soil over them. But there is very little high quality top soil in Colorado, it costs money we don’t have, and the beds would probably be more drought prone that way, since roots would be less likely to move below the preexisting surface.

We plan to replace our rather messy temporary sign with something more elegant, especially so the neighbors don’t have to look at a piece of painted plywood against a tree all the time.