what will happen if i put some garden soil from downstairs ontop of it some of my homemade compost and on the top bought planting soil?
for example plant sunflowers or sweet corn.
why?
to save money1.
to avoid evaporation since the planting soil has a bigger capacity of holding the water 2.
from the point of view of the plant i know it will meet another type of soil on its way down.....
how critical is it?

Usually people mix all the soils/composts together. I'm not sure why you would want your plants to grow through layers of different soils. If you are worried about water retention, put newspaper or wood chips or something similar as a top dressing.

Daisy

If you have a layer of fine textured soil over a layer of coarer material it will impede drainage between the two. As Daisy said, it is much better to mix the different materials together so that it is the same throughout the container.

davidsevit said:what will happen if i put some garden soil from downstairs ontop of it some of my homemade compost and on the top bought planting soil?
for example plant sunflowers or sweet corn.
why?
to save money1.
to avoid evaporation since the planting soil has a bigger capacity of holding the water 2.
from the point of view of the plant i know it will meet another type of soil on its way down.....
how critical is it?

In my opinion, what you are suggesting is not "critical." You say, No. 1, to save money, and I say, that's a very good reason.!

In nature, soils are stratified due to various climate/weather conditions and seasons. Experimenting is good...go for it!

The problem with layers is the potential for creating a "perched water table", where water doesn't move down from fine to coarser material until the fine material has become saturated. That's why we don't put gravel in the bottom of pots, for example, because it does the opposite of what one might intuitively think and actually causes the finer material on top to hold more water. There are some pictures that illustrate this phenomenon on this link:

http://gardenprofessors.com/co...

Avoiding a perched water condition in containers is very important.

Out in the open, in a regular garden, there shouldn't be a problem with doing a "lasagna" type layering.

thanks to everybody its a real new attitude the gravel story .i think iwill pprepare different typ[es of fillings

You're welcome, David! Experimenting is good! Thank you for your closure. Happy gardening!

Rainbow said:

Out in the open, in a regular garden, there shouldn't be a problem with doing a "lasagna" type layering.

A perched water table happens when fine material overlays coarser material but not when coarse overlays finer. I would have thought a lasagna garden would come in the latter category.

I'd assumed, perhaps incorrectly, from his previous posts, and also because the garden soil in this question was from "downstairs", that David was using this media in containers.

My containers are home made They are 15 liters in volume. Is it better for the sun flower to grow in a deeper container than a wider container? The volume is 15 and the difference is between 40 cm height to 30 cm height

The deeper container may have better growing conditions (aeration for example) but you have to consider also whether a tall one is more likely to tip over if it gets windy. If, from the location site and shape of the container, you think neither will tip then I would go with the deep one.

thanks iforgot the wind story


this is the look of the container.it used to hold soy oil.lately i have been using it as plant containers.for a few years.i am aware of the non breathing effect in plastic.my plumeria grew in it for 5 years at least.
my only problem i have is its outstanding color

They don't look very tippable - the aeration (and drainage) being better in a taller container is related to depth of the media inside the container rather than having to do with the breathing effect of the plastic. Looks like a good use for recycled oil containers

I think the bright yellow is very nice.

thank you all for the compliments.the use of this container really comes from a recycling point of view.its quite a chalenge to break through the concept of terracota.our municipality cut the containers into a shape than be useful as a shovel for the road cleaners

sooby said:The problem with layers is the potential for creating a "perched water table", where water doesn't move down from fine to coarser material until the fine material has become saturated. That's why we don't put gravel in the bottom of pots, for example, because it does the opposite of what one might intuitively think and actually causes the finer material on top to hold more water. There are some pictures that illustrate this phenomenon on this link:

http://gardenprofessors.com/co...

Great post and great link, Sue! I've heard this said a hundred times, but I also know that most people ignore, disbelieve, or never heard it.

The photos prove it conclusively. The water stays in the top layer, killing root hairs and rotting the roots, until that layer is 100% saturated. Even then, the top layer STAYS saturated, killing roots, and only the water in excess of "100% saturation" escapes down into the coarser layer.

I call it "establishing a capillary connection" all the way down to the bottom of the pot. (But that might be misleading also - it's just how I think about it.)

(If you happen to have an EE background, think of it as a transmission line with a kink or abrupt change in (I think) inductance. Capacitance? HF energy will flow smoothly down the line until it hits the abrupt change, then do wacky things like reflect. It's kinda-sorta similar.)

Note that even if your entire root zone is perfectly mixed or gradually changing from one layer to another, water can only drain down freely by capillarity and gravity until it reaches the drain hole. The the abrupt change from potting mix to air creates a break in the capillary conenction and a perched layer starts to accumulate at the very bottom of the pot ...
...
unless you sit the pot onto a wicking fabric like cotton terry cloth or cotton flannel. If the potting mix TOUCHES the fabric through the hole, then a capillary connection can be established between the mix and the fabric. The saturated / perched layer moves down into the fabric.

If you can drape the fabric so it forms a dangling wick, even a short one, water will drip out of the fabric, so that all water that would have been perched water can wick down to the low point of the fabric and then drip onto the floor.

It's a perfect example that you can't rely on "everyone has always done it this way".
Sometimes "everyone" IS wrong.

Rick's right Sooby, great information that most people are ignore(ant) about. And you too Rick. Good info. Way back when (you reminded me of this), we used to use wicking that ran up the middle of the pot and into a reservoir to keep this from happening. I think the reservoir was under the pot - not remembering exactly how it worked...

I also used to create my own wicking pots from un-glazed terra cotta pots (no holes) sitting in a glazed ceramic pot (no holes). The ceramic pot was full of water and wicked evenly into the terra cotta. Someone stole my idea and are now making a fortune.

Daisy

DaisyI said: ... Way back when (you reminded me of this), we used to use wicking that ran up the middle of the pot and into a reservoir to keep this from happening. I think the reservoir was under the pot - not remembering exactly how it worked...

Yes! Yes!! Every time I see an article about eBuckets or self-watering anything, I think about that.

When I asked Al / Tapla what he thought, his attitude was like "Well, you COULD ... but if your potting mix drains right, and wicks right, you should never NEED a wick."

I like your attitude better. It gives more range and scope for my desire to fiddle!

rick and daisy thanks for your discusion....i learnt alot