Ah, the old intensive vs extensive debate. I'd been convinced by the extensive folks for a while (spread plants out widely so each gets more water) but this thread combined with some observations of my own are making me doubt that. I'm now quite sure that with irrigation intensive planting helps to conserve the irrigation water. I'm still not quite sure about dry farming; intensive or extensive? Your picture is pretty good evidence for the intensive position. How did they yield?
This project was in my dry-land part of the farm. It has excellent drainage being mostly sand and rocks. It's about 400 feet to get to the water table in mid summer (about 50 feet in the winter). My observation so far is that in this part, closer spacing has drastically better yields.
In another part of the farm where the groundwater is close to the surface - less than 20 feet in the summer, about 1 foot higher than the ground in the winter. In this part, the close spacing helps in the early summer, but it seems to hinder in the late summer. I'm going to try wider spacing on this section next year to see if that improves things.
My theory at the moment is that availability of ground water is a significant factor in how closely together plants want to be.
So, I'm wondering if the close-spaced plants in your upland area may have more room to expand downward and avoid too much competition that way.
shauna carr wrote:Since you mentioned starting to look at more than just the dew collection, I wanted to share what some of my own experiences have been in the hopes that it might give you some idea of some of the details you can be monitoring, especially because some of the things we hear as 'absolutes,' like intense mulching, have turned out to be not as absolute as I thought. Iguess maybe that's why I so like Know Nothing Farming, because we can always find out new things that turn out to be opposite for what we thought was true, yeah? I'm just a bit impatient so I try to combine it with 'intensely researched farming with respect to my growing conditions,' heh. ^_^
Dew collection - This is really a great idea, but depends completely on the area having a high enough humidity. If you don't have a very high humidity naturally, or if a drought lowers the humidity, then this becomes not as viable a method of collecting water. The fog collecting redwoods are actually already having problems right now because the drought has done just this in CA and the fog level is lowering in the redwood's area (http://www.wired.com/2010/02/fog-decrease-threatens-coastal-redwoods/). So something to think about would be not what the humidity is now, but what it may be during a drought in your area, you know? Where I am now, during some seasons, the humidity is so low out of the rainy season, dew collection is quite negligible. And the temperature is so high, what little dew there is evaporates before it would hit the ground. But again - this is where I am, not where you are, yes? I would definitely say on the hottest, driest days, looking at the dew levels would be very helpful to try and estimate what might be going on in that area during a drought.
Mulch - This is something that is actually much more site specific than I realized and I would definitely make study of what mulching works well in your area one of the factors you look at. I found an interesting study a long while back on how quickly water evaporates from the MULCH (as opposed to studies on evaporation from bare ground vs. mulch). And it evaporates pretty quickly, actually, especially from mulch made from organic materials. If rocks or sand were used as mulch, there was very little evaporation. But with organic mulch, it can break down and add to the soil, whereas the sand and rocks prevent that, so there are other considerations, too, yeah?
This has turned out to be very good information for my area. And curiously was born up by a few pieces of traditional farming practices in the desert, too. Where I am the average high in the summer is 37 C - with the last couple of years having at least a week of daily temps around 43C. Rainfall is around 12 inches a year on NORMAL years, but has been closer to 9-11 inches the last few. Evaporation rate is higher than the rate of rainfall. And one thing that a number of people here have noticed is that if you are are relying on organic mulch to help keep the moisture in the ground, you have to have a large enough SOURCE of moisture. Otherwise, the rainfall drops onto the mulch and evaporates from it before it even reaches the soil. So folks here mulch their watered crops deeply, but do NOT mulch their native, watered-by-rainfall plants very deeply at all. Some, yes, but not deeply.
I also happened across an interview with a Zuni woman from New Mexico, USA who grew up following one of the traditional forms of gardening that have earned the name 'waffle garden' due to their shape (numerous square basins surrounded by low walls). I found it very interesting that when they would make it, they would add sand on top of the basins and the walls, to keep them moist. I was also privileged to be able to see an experiment by a botanist and archaeologist with the forest service in New Mexico, USA to try and recreate one of the gardening methods that had been speculated to exist with the Anasazi (ancient, extinct tribe in that area). They built a garden down in a valley (but still high desert) and after the crops came up, they covered the entire garden with large, rounded river stones, just leaving room for the seedlings to poke through. I cannot recall any longer whether it was never watered after that point, or almost never, but the experiment was a success and the garden did quite well.
Seemed to be another point in the favor of sand or rock mulch, yes? Except when I tried these in my area, they tanked as methods. The small pile of rocks with the cooler inside temperature? Tanked as well. After doing some investigating, I found out that the area in New Mexico where this was done had temperatures that were at least 10 degrees C cooler than my area on average, and I remembered that the rock mulched garden had been in filtered shade for a good part of the day, down in the canyon. I finally tracked down yet another study on rock mulch from an area merely 5 C cooler than my own and it turns out that rock mulch alone will raise the surrounding temperature at least 5 C at that level of heat.
So basically...the sand and rocks and rock mulch heat up so much here they were frying the surrounding plants here with the raised temperature. But deep mulching would capture the water before it hit the soil, and not-so-deep mulching doesn't keep the soil nearly as moist. It was very frustrating, and confusing. All the gardeners I knew here were simply using up water like mad and using deep mulch, but I wanted to do somewhat like yourself: try a method that I can do with just dryland farming, or close to it (we have a little too little water to do truly drylands farming except with native plants, as i understand it).
What I am experimenting with now, based on just looking around my area to see what's happening naturally, is to let the weeds grow TALL around my plants. They provide shade, which lowers the temperature and that's been a huge boon for the plants in my type of environment. The things is, though, when I have the shade, I can put a large stone or two by the garden plants, and the area underneath these stones will stay very damp far longer than the surrounding area, but the shade keeps it from heating up as much. I let light mulch cover the remaining area. If I try adding even a few rocks near a plant where there is no shade, then most of the crop plants literally fry - you can water them three times a day and the heat is still too intense for them. :-/
I have also done things like bury a few fist sized stones near or surrounding the crops, and again, moisture has remained higher under them - but not poking above the soil, they don't add to the surface temperature. I'm experimenting a bit with how many rocks I can add without interfering too much with the roots.
I have been doing as you have with the weeds, too, and I have discovered some fun things about letting them grow larger. One, they have acted as trap plants for some things. A certain type of nightshade, for example, wild seeded near my tomatoes, and as it had pretty flowers, I left it there. The tomato hornworms all turned up on the native species with only one single one left on my tomatoes. The shade has been a big bonus, especially in areas with more open dirt. For annuals, if I chopped them down rather than pull them out, the roots rot in the soil and add nutrients that way, and the dead weed is used for mulch on top, as you've been doing. I have also noticed that if I figure out WHICH weeds the birds take seeds from, especially during periods before the crop seeds come, and plant them on the edges of the crops, they will attract more birds which were instrumental in keeping it pest free, too. I've also had some interesting experiences with sacrificial native plants that weren't for insects, but rather animals. I had a garden next to a huge patch of native weeds. I have seen little rabbits sit in the patch of native plants, eating them, right next to crops they could have eaten instead.
I am trying to research which plants the native animals are more partial to and see how helpful it might be to grow them surrounding the crops, the next few years (gonna take some major research, I think!)
The closely grown plants doing better - that has been my experience as well. People here talk about it creating a microclimate within the bushiness of the plants that is cooler and a little more moist, as well.
The small pits - not only does it collect water, but during dry spells, it can simply be cooler as well. Cool air will pool in pockets like that at night and stay cooler a little longer after the sun rises - I'm currently trying to sink a small corner of my yard to grow plants that are used to slightly cooler weather. Some folks in my area seem to have used it with success.
Anyway, that's how things work in my area, and what I've noticed during some of my experiments. Obviously not quite the same environment as your own, but again, thought it might be useful to see how some of it works where I am, so you can have some ideas for what might or might not be going on where you are, yeah?
Oh, one other thing - you mentioned one of your legume types not doing well, yeah? And this is an area that you've mentioned everyone seems to agree does poorly, is poor soil, and so on, yes? I've run into something similar with my own legumes in some of our soils, and I have figured out that at least in some cases, part of the problem is that the soil has been so poor, no legumes have grown there - native or not - and so the soil has very few of the microbes that they need to collect that extra nitrogen they need. I found that growing successive plantings of the legumes has slowly seemed to increase the level of the proper symbiotic microbes in areas where this has been the problem (I compare this to areas where the legumes simply weren't growing well, due to heat, for example, where successive plantings never do anything but kill more plants ).
Good luck! I look forward to seeing how this experiment goes!