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Breeding for dew collection, or my experiments with dryland farming

 
pollinator
Posts: 149
Location: Missouri Ozarks
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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?



I've been following this debate for a while too, like so many things it all seems to depend on which species are grown and what soil and climate they're grown in. I favor less intensive for summer dry periods if no irrigation or even with irrigation if it's somewhere where I want to be able to go longer between waterings. Intensive is best for certain situations, if irrigation is your main water source during the season I do agree that watering a smaller area more intensively conserves irrigation water overall, but here in Missouri there's often plenty of rain, but even in wetter summers there tend to be dry periods, I've found that a bit wider spacing often makes the difference between only having to water when it gets really dry versus intensive plantings that can need water after just a few days of hot, dry weather. The areas of my garden that dry out the quickest are areas near the edge of an area with dense trees (the soil is also thin in that area, the top part is built up rich but doesn't have too much depth, and the nearby trees are only able to be healthy at such a dense spacing because of taking nutrients and water from the improved garden soil) Some plants transpire more than others, I have no experience in deserts but imagine that the native plants there transpire a lot less and so that would change the equation.

Seeing how moist it is at the top of the soil doesn't tell close to the whole picture for anything larger than the seedling stage. I've seen dense plantings do great for a while then get wilty and stop growing when they've used up most of the moisture from the deeper layers as well, when nearby less dense plantings are still doing fine despite the top layer of soil having dried out pretty quickly, as it's stayed moist further down for longer. Checking the moisture levels in the whole soil is only really possible if you dig a deep hole, I generally prefer to watch the state of the plants instead.

Some plants do prefer shade however and are best with taller plants nearby. I'm a big fan of growing corn and winter squash together (sometimes beans too, but it's tricker getting the varieties right so as not to make a complete mess of the patch). I plant both less dense than they would be by themselves, and the partial shade in midsummer definitely seems to benefit the squash in our hot summers, and the corn variety matures the end of August so the Squash are in full sun again in the fall when there's less light to go around. Squash tend to wilt in full sun here in midsummer even when the soil is very moist, while the stuff under the corn doesn't wilt much unless it's very dry.
 
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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.  
 
Richard Kastanie
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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.  



What is the natural vegetation like in your area in similar soils that are un-farmed? How dense is it? Here in the Ozarks the native vegetation is definitely more dense in the wetter areas of the landscape (which also tend to have better soil), bottomlands and north slopes tend to have more lush, dense trees than south and west facing slopes. My gardens are pretty high above the water table and pretty well drained because of underlying karst but my experience is more like your lower areas, possibly the roots of my plants can't reach as deep because the soil gets hard, rocky and poor not too far down, making it difficult for plant roots to penetrate.

I remember visiting northwest lower Michigan once (north a bit from Traverse City) and being surprised at how dense, lush and tall the woods were. Sugar maples for example took on the most impressive stature I've ever seen there. The area is very sandy, and hilly enough that the uplands are well above the water table. The soil seemed to dry out quickly being sandy but I was told by a long-term resident of the area that the trees grew so impressively because the roots could easily penetrate deep through the sand to get all the water they needed even when it seemed dry. The moderation of temperature extremes by Lake Michigan also helped, but I've been to other areas near the Great Lakes with different soil and less impressive trees. 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.

Another factor involved is nutrient availability in different levels of the soil. In soils like mine are rich near the surface but rapidly poorer the further down you go, what seems like water stress can sometimes be nutrient stress, as the plants cannot extract nutrients from the topsoil because of dryness so have to make do with whatever is deeper down where there's still moisture. Some people use fertigation if the water is limited for this reason.
 
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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.



This is the theory behind biointensive growing; beds are double dug, allowing much closer spacing without competition for water and nutrients.

There is a story that in part of Africa where there are winter rains but no summer rains, a group triple dug a bed (three shovels deep) before the rains, and were then able to grow a crop on it in the dry season. Others didn't have any luck with growing in the dry season, but the triple dug bed gave plants access to enough water storage.

 
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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!



Shauna, this is a very helpful post in understanding mulches....

I have another option for you in type of mulch - biochar!  It is sort of halfway between the organic mulch and the inorganic rock mulch.  I was intrigued by all the old accounts of spreading it on the surface and getting fantastic results and so I've been testing it.  And I had wonderful results up until the really hot and sunny days of June.  I was using pieces approx. 3/4 inch cubed in one layer and it kept the soil wetter and cooler underneath in spite of being black.  I presume it was because of the porosity and therefore insulating quality of the char.  But when the blazing sun and a heat wave arrived in mid-June it stopped being effective.  It didn't actually kill anything underneath yet, but it was no longer cooler underneath.  Either the same or warmer.  So I'm thinking it acted like the river rocks as mulch you described.  Up to a certain amount of sun, the rocks shielded and cooled, and then too much and they cooked.  So I have 2 options to try using char, add another layer of the same size pieces or try a mulch of twice as large pieces.  Both of these involve time and money and I have a lot of organic mulch (shredded old leaves and new green trimmings) on hand.  So I've added a layer of organic mulch on top of the biochar for now and we'll see how that works.

The biochar has several advantages to recommend it.  If well-charged, it can immediately add nutrients to the plants, which rocks cannot.  A same size piece as a rock collects more dew than the rock, even though some is undoubtedly also being absorbed and not collecting underneath.  Biochar can collect the nutrients condensed by the dew and rain.  It lets the dew and rain enter the soil rather than keeping it off as the organic mulch can do.  And as the biochar breaks down and weathers, it is incorporated into the soil where it will then supply all the advantages normally associated with working it into the root zone when first applying it.

Ray
 
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We are also working under extreme water scarce situation. Based on earlier reports, we used 200 pm of salicylic acid twice, once on young plants and second at flowering time; this reduced number of irrigation’s required drastically.  
 
r ranson
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I looked up salicylic acid.  It looks like it costs money and needs to be reapplied to the soil over time.

I would much rather find a permanent solution that works with the soil I have and doesn't need extra work from me.  

The plant breeding kale is going great.  I neglected it terribly this year, but now that the rains are here, it looks like the crop did great at growing good roots in the summer drought.  
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