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Breeding for dew collection, or my experiments with dryland farming  RSS feed

 
Richard Kastanie
Posts: 96
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.
 
r ranson
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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
Posts: 96
Location: Missouri Ozarks
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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.
 
Gilbert Fritz
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Location: Denver, CO
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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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