Porosity, Water Holding Capacity, Cost of Common Soil Components
ewwmayo
7 years ago
Featured Answer
Sort by:Oldest
Comments (118)
ewwmayo
6 years agoRelated Discussions
Water Release Curves for Growing Media Ingredients
Comments (45)morpheuspa: I asked to get clarification from somebody was, well, not you (I threw you two red herrings in my latest post; you found one, you didn't find the other and it was pretty blatant. When I sent your reply off to a friend of mine who's a physics professor, he had some rather unkind things to say that I didn't, of course, post because I'm not some other posters around here. I have no idea what you are talking about. morpheuspa: When I sent your reply off to a friend of mine who's a physics professor, he had some rather unkind things to say that I didn't, of course, post because I'm not some other posters around here. Please do not hold back. I want to see a nasty response from a Physics professor. If you have the courage please name him and his university too. You know full disclosure is important. morpheuspa: To me, it's increasingly clear that you are still confused about the water retention curves above and what they mean. Remember, that's also a force retaining the water in the soil. Of course, there is a force retaining the water in the soil. That is the whole point here. If you water a medium to complete saturation to the top and let it drain and let it come to equilibrium then you will have two zones in the soil. A lower zone that is completely saturated - a zone where all air space is filled with water. And an upper zone that is not 100% saturated. The boundary is the )Kpa tension. The height of this boundary is the height of PWT. If undisturbed then this saturated zone will remain saturated for ever. Above this zone water is still present within the particles and as a film surrounding the particles. But it is not 100% saturated - meaning there is some air space also between the particles. As go up towards the surface the film of water keeps reducing and air space keeps increasing. This is what is captured in the water release curves. Depending how tightly soil particles hold on to water, the release curves are different. Peat has a higher affinity for water and so a larger (taller really) zone above the PWT that can hold substantial water but not fully saturated. Bark on the other hand has a lesser affinity for water so holds much less water at the surface and rapidly comes close to being dry as move up from the 0Kpa boundary. Water release curves, in short, describe how easy or difficult it is to extract that water from the soil particles. Below the 0Kpa boundary there is a lot of free water (unbound and bound) and above it is only bound water. Adding a wick to the bottom of the pot moves the bottom soil/air boundary lower. Water above the wick is under positive pressure to move away from the soil. The wick extends the soil bottom boundary causing a reduction in pressure in the water column above. Thus it moves the 0Kpa boundary lower. If the wick is long enough this boundary can be moved below the pot. Thus effectively removing the saturated zone in the soil medium. The water release curves do not directly address this but does so indirectly. The key is that the wick extends the bottom boundary to a lower point. Many of the subtleties of what I am saying has been presented by Dale in this thread with good diagrams and explanations. I encourage you to go through them again. I welcome and encourage you to send this entire thread including my explanation to your Physics professor friend. In many threads you have boasted about your scientific prowess. I do not doubt that. I tend not to do that but instead try to explain the best I can. But do not under estimate my background. So keep it to logical explanations and if I am wrong I will gladly admit it....See MoreCactus roots & soil ingredients that retain water
Comments (12)Hi, AR. Thanks for the kind words. I don't get snippy about what people use for a soil because I don't care beyond the fact that I'd like everyone to get all they can from their growing experience. I do care when, during the course of a conversation, misleading or erroneous information that has the potential to limit your experience is claimed or inferred to be true. I'll argue those points with gusto, for no reason other than the fact I think it's important for (the collective) you to have accurate info if you're to make good decisions. I think it can safely be said that the number of plants that would do well in soils in which they naturally occur would be somewhere between very few to practically none, with the overwhelming number of them crowding each other for space at the 'practically none' end of the comparative scale. Putting mineral soils in a pot changes the way water physically behaves in them due to the fact it eliminates the wicking effect of soils deeper than pots. I said all that to say it hardly matters a whit, what type of soil the plant prefers growing in situ, 'cause it ain't gonna like it in a pot. Also, I don't think you should be thinking about trying to use the fines left over from screening Turface as a significant fraction of a soil for plants that happen to be vulnerable to ill effects caused by wet feet. You can increase water retention w/o introducing a perched water table by screening the ingredients to a size large enough to ensure the medium can't hold perched water, but also increasing the volume of ingredients that hold water INSIDE of the soil particles. IOW, screened ingredients equaling 4 parts Turface 3 parts bark 2 parts grit will hold a lot more water than the standard 1:1:1 screened parts by volume w/o sacrificing any notable amount of aeration or drainage, and it won't invite a perched water table to take up residence in the lower reaches of the pot. Al...See MoreLeaves squishy fast. Hot weather and soil an issue?
Comments (5)IIRC, you mentioned similar mix before and also wondered about it's water holding capacity; here is the answer: I do not know what is water holding capacity of Kanuma, but turface has water holding capacity of approx. 52% , so I would be surprised if plants are not getting enough in mix of these two? Here is what Kevin said: Turface holds a huge amount of water. 50% is quite a lot, especially indoors. Careful not to over water those pots! Could be a little challenging to balance over and under watering with that mix. According what you are saying above, your mix is: I'm currently using equal parts akadama, kanuma, and an absorbant clay like turface (that would make it 1/3rd of each). IMO, it doesn't matter much what are the proportion; you are using very similar materials. I think that mix may be holding onto quite a bit of water. Water holding capacity of akadama (I have read that, comparing same grain size, it is similar to turface and higher than lava and pumice) is approx. 40% (from Kevins post); I do not know about kanuma but they are probably quite close...so mix of these, in any proportions, would have quite high water holding capacity. It will be even higher if grain size is small. Besides water holding capacity, total air porosity is also important. Maybe you should measure kanuma, so you can judge. I actually decreased amount of turface I am using to less than 1/3rd (10-20%), because IMO, mix was staying wet for too long. I believe Kevin has too - hope he will see your post and has some answers...or anyone else there familiar with those products....See MoreWay to Cap Bottom of Test Pot for Soil Testing?
Comments (6)Tricky? Not really. Place one or two squares of nylon window screening in the bottom of the inverted top. I use such in regular pots without issue. For stability, rocks can be placed in the bottom section. Furthermore, if this is just to test the media, the weighted bottle could sit in a terra cotta pot or a shallow hole in the ground, or braced with bricks, or any number of other cheap, down and dirty solutions....See Morekil0
6 years agokil0
6 years agoewwmayo
6 years agolast modified: 6 years agoNil13 usda:10a sunset:21 LA,CA (Mount Wash.)
6 years agoewwmayo thanked Nil13 usda:10a sunset:21 LA,CA (Mount Wash.)ewwmayo
6 years agowestes Zone 9b California SF Bay
6 years agowestes Zone 9b California SF Bay
6 years agoewwmayo
6 years agowestes Zone 9b California SF Bay
6 years agoewwmayo
6 years agowestes Zone 9b California SF Bay
6 years agoewwmayo
6 years agotropicofcancer (6b SW-PA)
6 years agoewwmayo
6 years agowestes Zone 9b California SF Bay
5 years agowestes Zone 9b California SF Bay
5 years agotropicofcancer (6b SW-PA)
5 years agoVance Evans
4 years agowestes Zone 9b California SF Bay
4 years agoewwmayo
4 years agolast modified: 4 years agowestes Zone 9b California SF Bay
4 years agoewwmayo
4 years agogdinieontarioz5
4 years agowestes Zone 9b California SF Bay
3 years agolast modified: 3 years agoewwmayo thanked westes Zone 9b California SF Baywestes Zone 9b California SF Bay
3 years agolast modified: 3 years agowestes Zone 9b California SF Bay
3 years agolast modified: 3 years agoewwmayo thanked westes Zone 9b California SF Bayewwmayo
3 years agoUser
3 years agowestes Zone 9b California SF Bay
3 years agoewwmayo
3 years agolast modified: 3 years agowestes Zone 9b California SF Bay
3 years agowestes Zone 9b California SF Bay
3 years agolast modified: 3 years agotropicofcancer (6b SW-PA)
3 years agoUser
3 years agoewwmayo
3 years agowestes Zone 9b California SF Bay
3 years agoewwmayo
3 years agolast modified: 3 years agowestes Zone 9b California SF Bay
3 years agowestes Zone 9b California SF Bay
3 years agowestes Zone 9b California SF Bay
3 years agoewwmayo
3 years ago
Related Stories
GARDENING GUIDESHow to Stop Worrying and Start Loving Clay Soil
Clay has many more benefits than you might imagine
Full StoryGARDENING GUIDESWhat's Wrong With My Plant? Leaves Often Hold the Clues
Learn how to identify common plant ailments by reading their leaves
Full StoryGARDENING GUIDESThe Poop Scoop: Enrich Your Soil With Good Old Manure
Get over the ick factor already — this natural super-ingredient for soil has so many benefits, you'll wonder why you ever went chemical
Full StorySAVING WATERXeriscape Gardens: How to Get a Beautiful Landscape With Less Water
Conserve water and make gardening much easier with the xeriscape approach’s 7 principles
Full StoryLANDSCAPE DESIGNHow to Design Your Landscape to Spread Water
Water that’s distributed widely will more readily soak into the ground
Full StorySAVING WATER11 Ways to Save Water at Home
Whether you live in a drought-stricken area or just want to help preserve a precious resource, here are things you can do to use less water
Full StoryGREEN BUILDINGWater Sense for Big Savings
Keep dollars in your pocket and preserve a precious resource with these easy DIY strategies
Full StorySAVING WATER6 Reasons Why You Should Save Your Rainwater Now
Collect and store during the rainy season so you’ll have water ready for irrigation when you need it
Full StoryREMODELING GUIDESLiving Roofs Crown Green Design
Living roofs save energy, improve air, water, curb appeal — and the view from above doesn't hurt either
Full StorySAVING WATERIs a Rainwater Cistern Right for You?
These extra-large containers reduce runoff and save on the use of potable water for the landscape
Full Story
ewwmayoOriginal Author