Hi there! I really don't think that's going to be likely. Here, with a lot of taping the cover to the poles and even with a lot of thermal mass inside (bricks, water, compost, etc), I probably wouldn't leave much out below -2C (assuming a ground frost at +2C or lower air temperature), especially in the winter where the heat storing hours are low and the heat loss hours are high. My DIY improvements in my more recent video get me about 3C improvement overnight and the basic unimproved greenhouse probably gets about 1C over the forecast air temperature (I've not directly measured the outside temperature). It might be possible to add a wall of bricks to the inside of the cover and position the greenhouse sideways facing south (long side facing the sun) so the heat build up and less airflow gets you more protection but I've not tried it and I'd still be hesitant to trust it. The Romans used to do something similar to grow lemons in the UK in the open air. But I think the coldest we've ever had here was -10C in Jan 2023 and without any added protection (and a few holes in the fabric) it was about the same in the plastic greenhouse. But I imagine even a poly-carbonate or glass greenhouse might struggle at -20C without a passive heat strategy or even active heating - maybe a water heater connected to an outside mains electric source and dunked in a water butt? Not sure how safe that is or how expensive but some kind of heat source might be a good idea in those greenhouses where the airflow is less of an issue.

@@alexgrowsfood Wow, thank you for your elaborate answer. My question was stupid from the start, I then researched green houses and understood the phenomenon and different types. And yeah in Romania at least where I live we have -20 and even more for prolongued periods. Thank you for the info. Cheers!

Great stuff. Honestly, it holds water for ages. It doesn't rain much in Cambridge (lowest rainfall in the UK) but grass is like magic. Was surprised at how flat that graph was but it clearly works even in shallow soils

Thank you! Good luck!

Yeah, this can be a bother. In principle the grass can break down so by next season the seeds should find their way to the bottom but it's probably going to be less reliable than directly coming into contact. Might be worth an initial mulch early in the season and not topping-up and leaving it to decay/thin out by the autumn. I've not tried it but could be worth experimenting on a small area

@@alexgrowsfood all I have is containers (for now). Plus, I tend to over-seed. It works for me. I would also be interested in a larger scale experiment.

Ah thank you so much! Glad you enjoyed it

Amazing. Yeah it's remarkable. I guess compost is so soil-like that it basically behaves the same and the water transfer at the interface is basically unobstructed - unlike grass/hemp. I did suggest that the compost lost more because it might have had more water initially but it also had less clay content so the water can move much faster, including to the surface. If hemp was free/legal to grow (without an expensive licence) I'd do it but, failing that, looks like grass is terrific and it grows itself.

Yeah, they need reinforcing that's for sure. I did do a follow up video about storm-proofing them but eventually you'll get perforations that cause bigger issues

@@alexgrowsfood I did all the reinforcement I could but nothing can withstand the horrible weather in northern Ireland

I think so. My guess is either water can't transfer vertically as fast because it has to transfer between linear grains (mostly within the material) or the air can't get to it so humidity around the grains are high and evaporation stays low. I think that's why grass did a little worse than hemp but much better than bark. The main counter arguments are colour: hemp is white so potentially a lower temperature at the surface and evaporation slows and also the bark had decayed slightly so had some soil-like / compost-like material in it and because those particles are so small you get a different dynamics (I think the water moves externally to the material - like a suspension or via surface tension on a microscale and can move pretty well in all directions). It's been a while and I've not looked into the microscale mechanics in that much depth but that would be my guess.

Yeah it's weird but I guess it's basically soil and has very little clay content so the water can move quite fast through it too. Possible you'd get an improvement in sandy soil in pots if the compost was very stodgy but not in my clay-heavy patch.

That sounds smart. I saw someone use rotting fruit - pears maybe - nearby as a decoy, but I've not tested it. They don't seem to be interested in apples

I'm not absolutely certain but, to me, it looks like they've chopped up or shredded the dried stems. They are very flat, very small rectangular pieces. I've been using AubiChick which is meant to be organically grown and used for chicks and chickens rather than the larger pieces they make for horses. They state they use the 'core of the plant'

Interesting question. I've never tried hydroponics, but I'd be surprised if you'd _need_ to add nutrients. For these ones I harvested them while they were really really young so you can rely on the energy stored in the seed. I grew them in the surface of pure coir. I think if the plant takes more than a week or two to go from germination to finished or you want more nature leaves, I'd consider a nitrogen source. But for these and for things like bean-sprouts, a sterile environment and moisture is all that's required. I'd expect similar behaviour in water (but happy to be corrected if someone else sees this or if you want to try it and report back)

No worries, just be sure to give them a lot more water - either a long drawn-out watering over hours (potentially) or maybe doubling up the soaker hose. It depends on the watering requirements of the tree and your soil type & structure. If it helps, I get through about 5L of water a minute over a 75m length

Yeah they are quite the investment. I slowly bought mine over time (and one was given to me - by luck, not by the company) or anything) but I think they'll last long enough to be worth it and I suspect more cost effective than a drip system if you have dense plantings. Not cheaper than manual or a sprinkler though (sadly).

It's an amazing result. I unpacked the experiment not long ago and, while it has rained a bit since, there was so much moisture still in there. Still felt like wet clay on the top and stuck to my hand. Hemp was great too but it isn't free.

That's really cool. I guess you still get decomposition and nutrients permeating through the fabric and into the soil too.

Same. 2022 was all no-dig beds at half thickness and called it done, but turns out it's very soil-like. Deeper compost will help (water takes a long time to move, especially in clay) but yeah... Compost with grass clippings on top is the way imo

Thanks Rebekah!

Thanks Mark! Imo grass is probably better anyway tbh. It's free and doesn't blow away as much or breakdown as fast. No pesticides either

@@alexgrowsfood ha, but no grass clippings around here. Grass lawns take up too much water and we live in a desert so everyone has artificial turf 🥵

Thank you so much! It's hard to make videos this condensed so appreciate the comment

Thank you! I imagine hay would be a lot like grass, I imagine straw wouldn't be too similar but my guess is they pack less efficiently by volume and allow more air flow to/from the soil (and any soaking up of moisture to be faster and more coherent) so I'd guess a little lower. I doubt there is much in it though and it'll depend on exactly how it's cut up. My guess is a mix would promote more evaporation than pure grass/straw (more gaps, darker overall surface colour) but layering might do a better job. In reality you'd probably have something like compost over a bed, with grass/hay on top and using straw in pots and a thicker layer of bark/woodchip on the paths and around trees. Think this is a standard picture and it sort of makes sense really.

Thank you for replying! I am more interested in mulching around the trees, so mix or layering seems like a better option. Would you mind telling which program you have used for plotting your data? I know a few but do not recognize this one :)

@@artur_pinski No worries. I use matplotlib in Python for all my plotting. I have lots of snippets of code lying around from my PhD days. I swapped the font and use other default/custom parameters so it's not the easiest to spot. The line animation was a crop effect in the video editor though.

Not really - the relative rates of evaporation are unaffected. There are lots of limitations (moisture levels in the mulch, destruction of soil structure, being in bowls at all) but the bowls being glass isn't at the top of the list

Thank you, very welcome!

Thank you! Glad it was helpful

The comment I was waiting for. Had a ton of code lying around from a phd. The best imo

Im a big fan of R but python is a fine language and more general purpose than R.

Really enjoyed your research project here. Interesting stuff.

Yeah, the syntax is just really nice to work with. I went Fortran->Python->C++ but Python feels natural. I did an R course and you can definitely feel how it was designed for a given task, never really managed to displace Python for me but super high uptake in biology and researchers without programming backgrounds

I think so. I spent a lot of time studying how things pack together and my expectation would be that the large and long pokey shapes pack together inefficiently with a lot of holes in between and that allows more air to flow so evaporation should be much easier. It was very windy too and I expected a high airflow effect. Additionally the bark came with lots of dust/dirt which is probably partially broken down bark, but I imagine that soaked up water and helped it wick to the surface too. Lots of people have also pointed out the dark colour causing a heating effect. Some mentioned using 6 inches of bark for good mulching and that makes sense for all of the above imo. Just some thoughts. Imagine if you could get more spherical or more regular cubic shaped wood chips, they'd do a lot better.

There's so many interesting videos about mulch, but I haven't found another video that does this sort of of comparison testing of mulches. Comparison testing videos are one of the most interesting and informative types of videos, so much so that there are plenty of KZfaq channels that are only about comparison testing different products. I just thought I mention this because clearly it has something to do with the healthy amount of views this video has received. Well done. You're testing not only demonstrated some really good info, but also inadvertently raised so more interesting questions. Like, why exactly was the the hemp and straw so effective at preventing evaporation? They're both fibrous materials, presumably designed by nature to be effective at wicking moisture, and the hemp in particular was finely ground, close in consistency as the typical potting soil. Therefore, one would think that the hemp would have preformed as well as the compost, quickly wicking moisture up from the soil. So there's another factor in this picture, regarding the inherent wicking efficiency of the material used, that I would like to see explored.

Thank you again. I definitely have my theories - water moves faster through soil through pores and so does air, so a loose compost probably has little effect while hemp is solely through moisture absorption and transfer between the plant material (probably cellulose, which I expect should bind strongly with water molecules) so be very slow. Other people have rightly commented on the colour and heat absorption. It's probably a mix - the heat helps when the moisture gets high enough to evaporate. Not sure when (or how) it could all be tested for sure but I suspect it's something along those lines.

Thank you! Es-cargo still cracks me up

Thank you! Honestly these were just the materials I had lying around. I'm not sure where I'd get some of those tbh but I've heard good things about the rice hulls. Plastic sheet might be fine but be careful not to heat the soil too much or limit oxygen transfer and imagine that one would be the most soil type dependent of the bunch.

It's a game of probabilities really. Less coverage is less likely to incur problems. In the west I sort of take your point (I actually think the repeated light rain is a bigger problem) but I live in the driest part of the country and there really isn't much rainfall at all, even this year it wasn't that extreme

Thank you! Honestly it's such a win that a homegrown item like this is so good. Forget the compost, straight on the ground for organic goodness at no cost but a weekly mow. Sublime result

Thanks mate. You almost got a graph of the gradients of the time series, would have been sweet but uber nerdy

@@alexgrowsfood Well ... It-[All]-'Started' With NEWTON's-Fluxions ... The-'Greatest''-DOODLES of [All]-TIME So-To-Speak!!!??? >(*U^)< (Joke) *Wink*

Assuming that's bottom-up, I guess the sand would trap the moisture. Top-down, you could probably skip some of those as I imagine the plastic does a neat job. Just be careful with restricting airflow and not overheating the soil and consider alternative ways of feeding the soil, including adding carbon.

Thank you so much!

Yeah I very much wanted to measure evaporation rates to support some hydrology simulations I was running. It's also an easier setup because watering the bowl and waiting for it to seep into the soil is dependent on the mulch but also the soil type and structure and it could be quite slow and differ a lot between areas. We then probably want to look at moisture build up and then it matters how often and when in the day I water the bowls. Agree it would be cool to know the net effect of adding mulch from a top water scenario but I very much chose the simple option (just measuring evaporation for an irregular bottom watering scenario). Might follow up though on water content if I can get my simulation working and apply it to different soil types.

I'm not sure about sand. It gets quite hot and is quite small so good at restricting airflow but it also soaks up water. My guess would be it doesn't do as well as the top two and it won't feed the soil. If I do another set I'll write it down but it would have to be a complete set to account for the weather which is the main driver.

Thanks Vin. Tbh it would depend so much on the soil and distance from the water table and my patch of ground isn't consistent enough. I was really just after evaporation data for some simulations I was running. If I get them working I'll see if I can do something on water content and try and apply it to different soil types

It's amazing how good the free option is, isn't it? I had expected compost I bought in to do the job for me when I set up the garden but it was a tough year. I'm not the greatest at making my own compost so this is the perfect use

Love it! I've just lost my drying area so I'll probably be doing the same too. Saves a step...

Thank you so much! Possibly... The compost was a weird mix of sizes really but parking that for a moment, with the true mulches it seems like you're right. Better packing factor and reduced airflow to the soil.

Possibly, especially if packed densely. Although significant water application should still seep through and the other materials have their own issues with top watering too. I recommend watering underneath anyway