Monday, November 14, 2011

Sheet mulching and pH

Finally we have our first two beds filled with dirt.
The first one we sheet mulched in order to build the soil directly into the bed and the other we 
simply filled with cenote dirt.
I used sheet mulching a lot in our garden in NC, when opening another piece of grass up for growing, rather than digging out the grass, I would simply cut it real short and sheet mulch directly on top of the grass. This would incorporate the grass, roots and all the layers into the building of the soil, and at the same time avoid disturbing all the life beneath the grass.
Here however I am trying out using this technic to build the soil directly into the raised bed.
This is the process we used this time around, every time I have sheet mulched it is always a little different, depending on the materials I have on hand.

First we cleared out all the rocks, well the ones that we physically could.
 Then to clean the soil (as has been suggested by local farmers) we added a layer of ashes and left it in the sun for a day. (as it turns out I wonder if this was a good idea as my soil test proved that our soil, at least the cenote dirt, is very alkaline, and ashes are used to make acid soil more alkaline, so not exactly what we needed) .... ohh well....
 Then we added a layer of card board, if there are any weeds or if you are sheet mulching on top of grass or thick weeds this layer will smother it. Then lots of water.
 Then we added a thick layer of greens
 Then lots of water, as between each layer, in essence much like making a compost pile.
 Then we added a layer of dry matter, could be leaves, newspapers, or what ever you have, we used 
the dried cut grasses from the cenote. Then more water.
 Then a layer of horse manure, and more water.
 Then we added a layer of our ready compost, then more water.
 And finally a layer of cenote dirt.
Ideally I would leave that for a few months, in NC I would leave it to overwinter and it would be ready in spring, but here with the heat I think it will soon be ready, because it has already been sitting for about   4-5 weeks and is no longer warm at all.
Now the bed below is filled with just cenote dirt.
I did a home soil test the other day and it tested the soil very alkaline, which usually translates into a high salt content, this makes sense as the dirt is taken from the cenote. Apparently at some point the saltwater of the sea mixes a little with the underground river systems here, so sometimes the water is more salty than others. Also we find alkaline soil mostly in arid areas, which this place must be said to be, at least somewhat, when we arrived in early summer, it was just the end of 
dry season and it looked much like a dessert everywhere. 
Apparently it is tougher to lower the pH of the soil than it is to raise it if your soil is too acid. Generally soil is considered neutral when the pH measures 7.0, anything below is considered acid soil anything above is considered alkaline. Most plants prefer a pH around 6.5-7.0.
Our cenote soil measured at least 7.5, that may not seem like much but it makes nutrients in the soil unavailable to the plants and encourages pests and sickness in plants when the pH is off.

There are a few ideas out there as to how to remedy this problem.
Add plenty of organic matter, when we have more compost ready I will mix at least half the bed
with compost. Adding peat is also mentioned, but peat is expensive, a nonrenewable resource and I do not even know if we can get it here. Another suggestion is adding sulfur straight to the soil, not sure about that but does not sound like a sustainable way to handle the problem. You might also add vinegar, which has a very low pH, but this will need to be done continuously to work, and so not very practical.
Another suggestion mentions composted sawdust, this we have though not composted, 
and I will add some once it has broken down a bit. 
Horse manure is also said to do good and this we are already adding.
I hope and believe that adding plenty of compost, growing a cover crop rich in nitrogen and continually adding mulches will go along way to solve the problem, but I will keep you posted on the progress.
Can you tell these things interest me? I find the workings of the soil so interesting.


  1. I love the way you are going about this. You will have unofficial, but very rich credentials in soil management when you are finished. The layers fascinate me, and I am VERY sorry you are not close enough for me to contribute horse manure, which I happen to have in abundance. Manure, I will tell you, is NOT very beneficial when applied in piles on top of grass, which is the strategy my horses seem to favor - a little self defeating. The bed looks amazing. The deep, rich darkness of the soil - what will you grow there?

  2. Well now that I have realized the high pH I am not sure how I will proceed. I have seedlings ready to be planted, but I am almost certain that they will not thrive in this soil, so I must keep working on it till I lower it before planting I think, or just try and see what happens. In this event it will be, cabbage, broccoli, basil, parsley. The tomatoes I dare not put in there and will likely grow those in buckets this year.

  3. Yay - this is great! I've been building beds for next year using the same technique, though with differences in material. And it really IS a fascinating process. Should be interesting to see how the gardens work out!

  4. We have had a similar issues here in Fargo, ND... trying to grow blueberry bushes. Of course better yet would be to give up on the plants that don't thrive in our soil, but I was SO keen for blueberries after moving from NY state. Anyway, we had good luck using sulfur and cotton seed meal the initial years. Now (five years in) we simply mulch with our christmas tree boughs and needles annually and that seems to have helped immensely. Do you have any evergreens/needly things that grow there? Once the boughs dry up the needles come off easily and work in very nicely.
    Good luck - fun to follow your progress.

  5. Amy, Thank you very much for the advice, I will try that. We do not have any pine trees here, but perhaps there will be imported Christmas trees cast aside after Christmas.


Thank you for stopping by, I love to know you were here and enjoy comments so much.

Note: Only a member of this blog may post a comment.