What is the Convex to Concave cross over from Mediterranean to Arid Climates?

Drylands: Concave beds to trap water, shelter plants.

Mediteranean: (Small Rise) Raised Beds but trellis shade is common.

Cold Climate: Large Raised Beds (huguls invented north of Mediterranean.)

SO MY QUESTION IS THIS: When our Mediterranean climate is becoming more arid, desertifying, shouldn't we adapt at a threshold point? What is that point? Does it have to do with the quality of the winters, merely a soil moisture, rainfall or all of these and more factors? What would be a simple rule of thumb?



From the Foothills of Central Valley, California,

MP

Here in the hot, but wet climate of Georgia I am a bit perplexed about how the hugels work. I have built my hugelbeds by digging down 8-12" and using that as soil to cover the logs and wood chips I bury. At 8-12", I hit the clay layer that underlies the southern half of Georgia, and it is very slow draining. It may take 3 or 4 days to dry up after a gullywasher, but at least I know there is water available at the bottom of the hugelkultur. But here is where the problem comes in; I build the hugels up maybe 18-24" above grade, and the tops are dry as a bone! If I scratch into the top 3" of the hugel, it is VERY dry. It's very difficult to keep plants properly hydrated, and at the end of every day, I check for signs of water stress for the plants that are on top of the hugel. Until they grow a little, develop some root system and get to a certain size, I have to baby them by watering them often.

However, once the root system gets down into the bulk of the logs/wood chips/organic matter, the plant really takes off. Two weeks of struggling changes over to growing like a weed. Plants on the side of the hugel seem to do well, taking less time for their exploring roots to find the nutrients. And as for the weeds that are present at what used to be grade? It's like they are on steroids.

So I don't have an answer to your question about where it crosses over. I like the convex beds, because the plants real low on the hugel do amazingly well. But the top of the convex part is not retaining enough water for seedlings planted on top. And forget about seeding on top of the hugelbed. I am VERY disappointed with my results of broadcasting seed on top of a hugel. If I want seeds to sprout on the hugel, I had better plant them low down on the hill.

If you have clay layers in your subsoil, you may be in a similar situation as mine. Clay stores water very well, but if it is compacted, plant roots can't break into it and access it. I think that lots of organic matter on top of the clay helps, as the organic matter wicks up moisture and it also provides plant roots with nutrients. But it can only wick up moisture so far until the hot summer sun draws that moisture off.

Hey Matt. I am in Sacramento so I feel your pain. This year I have had a lot of opportunity to experiment on 9 acres that I am leasing. What I have had a lot of success with is mulch pits. I have watermelons, beans, and sunflowers I have not watered since planting and the melons just started running. They are about 3 feet wide now. And this is through very hot dry and windy days. We hit 102+ for about a week a couple weeks back and I did not water. Temps have been 90+ since then and I still have not watered. Everytime I go out to the farm the watermelons have grown and are thriving in the heat despite my neglect. I think this is a combination of growing technique and genetics. The watermelon variety is ali baba a heirloom from Iraq. Other varieties are doing well but the ali baba is growing like a weed.

Can you describe, in some detail, what you mean by a mulch pit and how you make them? The idea of growing any kind of vegetable without additional water up till now in the valley is an attractive, and somewhat unbelievable, notion to me!

Dig a hole 2 feet wide and 2+ feet deep. The deeper the better. Use the dirt from the hole and build a mound around the hole. Back fill with leaves, grass, weeds, manure, etc. Top with 6" of free wood chips so that the back fill is even with or above the surrounding mound. Compress by stepping on and add more mulch if necessary. Mulch and plant in the mound. Water pit until it over flows then water mound. This seems to be better than raised beds in my climate. I may try adding wood next season as well.