[permaculture] arid soil building
raincascadia at yahoo.com
Fri Dec 4 13:47:55 EST 2009
Dieter, why don't you write a book about your experiences and knowledge regarding living in the Mediterranean? Or at least a long article for a permaculture magazine? I'm going to start saving your emails. I find your information extremely valuable.
Most of my irrigation (which I've stretched to the limit due to a variety of social and other factors) is applied through drip, so I don't have the problem of water evaporating off mulch. I had to abandon most of my small annual beds, so most of what I'm talking about is trees and shrubs. Most of these are still only up to three feet in diameter. I've tried to give the trees about 10 gallons (40 liters) a week, but by mid July or August I can usually only afford about 7 gallons. Some trees are doing better than others, but I have the intuitive feeling that the few trees I hand water three times a week seem happier. My gut tells me that younger trees (at least) really need to have the entire surface of the soil near their roots remain moist, not just a the column of soil below a drip emitter. I've been surprised at how poorly the figs, chestnuts, and almonds have fared, but I've been impressed by the growth of certain acacias, especially
Acacia dealbata, despite its flammability). My soil varies from serpentine-derived heavy blue clay (high in magnesium and calcium) to sandy clay loam with pH values from 5.5 to 6.9. The new pond we built is slowly filling and I hope this will change the whole irrigation situation radically. I feel the trees need two or three times the water I'm giving them (the University of California at Davis says I should be giving them 10-25 gallons a DAY rather than a week!).
My kitchen garden experience here is still very limited, but I plan to mulch the entire thing. I can't stand using short-lived plastic drip lines at the density needed for this application, so I am actually thinking about using microsprayers or even sprinklers, even though these are less efficient and create other problems. I don't want to spend half my day hand watering, either. Flood irrigating furrows might be cool, if I could figure out an automated method.
As for biochar, it is hard for me to see doing it on any scale given the involved preparation. I can't imagine the people who created Terra Preta went through all this trouble, though the tropical context makes a big difference in how the charcoal would interact with the soil.
All my life has been spent in maritime climates, even in California, until now, so it is taking me some time to adjust. A lot of the recommendations I hear from people are inappropriate to this climate. For example, cover crops here never do as well as the wild plants that are already here. We have several species of native and exotic clovers, plus two species of vetch, that virtually cover the ground. Wild oats probably grow as well as any other grass. Most of the cover crops need more rain than we get, or require soil cover, so are only appropriate for small, cultivated areas like the kitchen garden.
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