Today I went too visit my friends at the Ex-hacienda de la Petaca. Unfortunately I got of the bus too soon and ended up walking about three miles down the desert highway and then about ten minutes on a dirt road. Luckily today was not that hot. I finally made it to the hacienda about an hour late. I found Keli, Mike and Jaime up on the hill mapping out berms with this interesting leveling tool I had never used before. Jaime gives Keli and Mike hands on lessons every week. I do not know him very well but he sells mesquite at the farmers market and is very knowledgeable about native foods, land restoration, water-harvesting earthworks and permaculture. I am hoping to learn from him more during my time here. Jaime created a table that determines the necessary drop and spacing between terraces on a slope relative to its grade. He made these calculations for this climate specifically that gets less than 28 inches a year. In a rainier climate, the spacing would be much closer. Because we do not have large machinery to form terraces, we will instead use available materials to create berms along the contour lines at appropriate intervals. Because the grade of this slope is 4%, every 24 meters there will need to be a 1 meter drop. This means the berms will be 24 meters apart and built to be 1 meter lower from the previous.
The intention of building these berms is to restore the land by preventing further soil erosion and harvesting rain water. Burning seems to be common practice here in Mexico and it is very detrimental to the health and vitality of the soil because it kills all the beneficial microorganisms and depletes nutrients. It is done mostly to prevent wild fires by clearing out dry grasses in a controlled manner, but also for other reasons. The land we were working on today had a few areas that had been burned by people trying to harvest trees for firewood and other uses. They had burnt the trunks instead of cutting them, my guess is because it was easier than using a machete.
The berms are going to be constructed out of tree branches, rocks, and dry vegetation. There is an invasive air plant species that infests the trees around this area of Mexico called Paschtle (Tillandsia recurvata).
Here is some information I got from the blog of my friends at the ex-hacienda about this plant:
Paschtle is an epiphyte (not a parasite) that blocks the photosynthesis of a tree. The thorns and rough bark of the mesquite provide a very secure surface for the the hairy seeds of the Paschtle to attach to. The paschtle is looked upon as a parsite, and pest, however, it is a blessing waiting for our harvest. The paschtle is high in nitrogen and can be used as animal fodder or compost material. In these arid lands, building soil is our number one priority, paschtle can help us. We also utilize paschtle to build terraces to retain soil. There is some basic research into the use of ball moss extracts for anti-tumor and anti-inflammatory uses.
check out their blog: http://exhaciendalapetaca.com/septimastudios/
In permaculture every problem is also a solution.
We used a measuring stick and an binocular with a built in level in the lens to find the contour lines that the berms would run a long. I have done water harvesting earth works before but used a type of water level sometimes called a bunyip. I had never used this system before.
To use this system you first find where your eye level hits the measuring stick when standing next to it. When you look through the eye level, there is a middle line and vertical level to the left in the lens. If the middle line is at your eye level mark on the marker and the level bubble is in the middle, the line between the two points is a contour. Read my posts Earthworks and Bunyip for more information on water harvesting earthworks.
Here are photos of the berms that Keli and Mike built in the mesquite grove. The soil in this grove is very silty and high in organic matter, making it valuable for growing. They plan on planting perennial shade tolerant herbs beneath the trees and adding in swales. Swales are dug out indents that collect rainwater and distribute it to the surrounding root systems. Berms are raised barriers. Both slow down water flow and protect the soil from erosion while simultaneously harvesting water.
All the Nopal (prickly pear) cactus were starting to bloom. The fruit is called tuna.