How tight should soil be compacted

[John Robertson]

I'm not a gardener but I planted some seeds of food eaten from the kitchen
(pears, apples, lemons, oranges, avocados, watermelon, pomegranate, etc).

I put the soil in typical plastic plant containers but I don't know if I'm
supposed to pack the results tightly or loosely or mediumly. If I pack them,
with a mallet I can easily triple the amount of soil and even if I compact
them with my fist, I could easily double the amount of soil, so compaction
certainly makes a huge difference in soil volume.

There must be an optimum amount of compaction though, for soil volume and
for water sponging I would think that the experts already know about.

What's the rule on compaction when you dig the soil out of the ground with a
shovel and then when you fill a dozen of these quart to half gallon sized
black plastic planting containers?
--
"Old pinballers never die, they just flip out."

[bob prohaska]

In rec.gardens John Robertson <sp...@flippers.com> wrote:
> I'm not a gardener but I planted some seeds of food eaten from the kitchen
> (pears, apples, lemons, oranges, avocados, watermelon, pomegranate, etc).
>

Those seeds all have fairly different germination techniques; for example,
avocado pits are commonly sprouted in water. Sounds like you're experimenting,
to see what grows and what doesn't.

> I put the soil in typical plastic plant containers but I don't know if I'm
> supposed to pack the results tightly or loosely or mediumly. If I pack them,
> with a mallet I can easily triple the amount of soil and even if I compact
> them with my fist, I could easily double the amount of soil, so compaction
> certainly makes a huge difference in soil volume.
>
> There must be an optimum amount of compaction though, for soil volume and
> for water sponging I would think that the experts already know about.
>
> What's the rule on compaction when you dig the soil out of the ground with a
> shovel and then when you fill a dozen of these quart to half gallon sized
> black plastic planting containers?

Depends on the seeds, soil and importance of success. If you're using
natural soil you might let water do the compacting. Flood the pot of
soil, push the seed into the resulting mud and flood the pot again.
That's how nature compacts soil and will give some hint how the seeds
might fare on their own in your area.

If you really want the seeds to grow, David's approach is customary.
There's much less risk of waterlogging if you use a porous mix, pack
it till it's just immobile when flooded and make sure all liquid drains
in a few minutes. Very few seeds will germinate if submerged.

I think waterlogging is the biggest objection to using natural soil
in pots. It's too easy for the water to get trapped in the pot,
especially if the pot is plastic.

hth,

bob prohaska

[Jeff Layman]

Waterlogging and/or drying out are the two commonest reasons for
germination failure. It doesn't matter what soil or compost you use, or
even how compact it is, if you follow this guidance:

Put the soil/compost in the pot. If using soil, just fill to within 1/2"
of the top; if using compost, fill to the top and press down 1/2". Put
the pot in a bucket and fill with water to the soil/compost level. Leave
for an hour (some peat-based composts, if dry, can be very slow to take
up water again. A drop of washing-up liquid in the water can help).
Remove pot and allow to drain for 15 minutes. Add seed(s), and either
push into the compost until well covered or place on surface and cover
with a little moist compost. Put pot in a polythene bag and seal the
bag. Just keep an eye on the pot every week or so to see if germination
has taken place. With the bag sealed, you won't have to worry about
under/overwatering. Once germination has taken place, remove the pot
from the bag.

--

Jeff

[micky]

In alt.home.repair, on Sun, 17 Oct 2021 08:16:44 +0100, Jeff Layman

Though I have had little problem with planting, iirc, I have to reread
this thread.

My big takeway is that there are two groups I didn't know about,
rec.gardens and alt.agriculture.fruit. That's more important to me than
any one thread.

Esp. after alt.home.lawn.garden faded away, I'm not sure when.

Glad you included us, John.

[John Robertson]

On 2021/10/17 4:56 am, bob prohaska wrote:
> Those seeds all have fairly different germination techniques; for example,
> avocado pits are commonly sprouted in water. Sounds like you're experimenting,
> to see what grows and what doesn't.

Well, I didn't say I was an experienced gardener, did I?

I knew of the avocado in toothpick on top of a drinking glass method but
some of the avocados that I threw will nilly on the ground grew over the
years (just in the wrong spots), so now I'm trying to containerize them as
transplanting always kills them (same soil packing question though).

>> What's the rule on compaction when you dig the soil out of the ground with a
>> shovel and then when you fill a dozen of these quart to half gallon sized
>> black plastic planting containers?
>
> Depends on the seeds, soil and importance of success.

This is a generic question in that we can assume the seeds are "kitchen
seeds" since I'm no expert. I first googled but that just made me dangerous.

I can snap a photo of my test bed if you're interested in seeing it.
With respect to compaction, as far as I can tell from googling, "air spaces"
are death zones to plants, aren't they?

Google told me that plants don't get their nutrients from air but from water
but even then the water has to be the right kind of water.

Google told me there are three kinds of water in the soil profile.
<1> Hygroscopic, aka unavailable
<2> Capillary, aka available
<3> Saturation, aka gravitational, aka field capacity (unavailable)

Field capacity, google said, was when there was just the right mix of soil
particles and capillary water because plants don't "breathe" so much as
"drink" their nutrients (says google anyway).

> If you're using natural soil you might let water do the compacting.

I first filled with "natural soil" (the stuff all around me), and then
filled with water and hit it with a stick (stokes law). That dropped the
level an inch or more in and of itself.

Then I compacted with my fist and that could drop the level in half if I
wanted to do that.

My question is really all about how much compaction is normally needed?

> Flood the pot of
> soil, push the seed into the resulting mud and flood the pot again.
> That's how nature compacts soil and will give some hint how the seeds
> might fare on their own in your area.

You have a good point if this was in the ground where the soil has already
reached a steady state of compaction. But does it work when you just dug the
soil out of the ground (so that it's no longer in any compaction state)?

> If you really want the seeds to grow, David's approach is customary.
> There's much less risk of waterlogging if you use a porous mix, pack
> it till it's just immobile when flooded and make sure all liquid drains
> in a few minutes. Very few seeds will germinate if submerged.

The "mix" is whatever soil I dig out of the ground.
The porosity is what I'm trying to ascertain.

Since plants drink (they don't breathe as far as I can tell), I don't want
any air but what I want is water that is "available" (capillary water).

But how do you compact the soil to make sure the water is all capillary?

> I think waterlogging is the biggest objection to using natural soil
> in pots. It's too easy for the water to get trapped in the pot,
> especially if the pot is plastic.

You have a good point there where I think I am waterlogging them too much.
I will stop that.

Do you want to see pictures of my test bed?

[bob prohaska]

In rec.gardens John Robertson <sp...@flippers.com> wrote:

> On 2021/10/17 4:56 am, bob prohaska wrote:
>> Those seeds all have fairly different germination techniques; for example,
>> avocado pits are commonly sprouted in water. Sounds like you're experimenting,
>> to see what grows and what doesn't.
>
> Well, I didn't say I was an experienced gardener, did I?
>

No, but it sounds like you're trying to become one. That takes
experimentation. Using your particular starting materials.

> I knew of the avocado in toothpick on top of a drinking glass method but
> some of the avocados that I threw will nilly on the ground grew over the
> years (just in the wrong spots), so now I'm trying to containerize them as
> transplanting always kills them (same soil packing question though).
>

Avocados have impressive taproots. I've started several in water, then
transplanted to containers made of grow tubes a couple feet deep. Then
they went into the garden the following year. After eleven years only one
has bloomed out of eight germinations and five survivors.

An avocado on toothpicks in a glass of water illustrates the requirement
neatly: Mechanical support, water contact and air contact. The layout over
the surface of the seed can be fairly variable, else plants using seeds
would be extinct.

>
> This is a generic question in that we can assume the seeds are "kitchen
> seeds" since I'm no expert. I first googled but that just made me dangerous.
>

Kitchen seeds are not special, except that they're likely hybrids that
won't have much vigor and certainly won't breed true.

> With respect to compaction, as far as I can tell from googling, "air spaces"
> are death zones to plants, aren't they?
>

Air is good, water is good. Seeds need both.

> My question is really all about how much compaction is normally needed?

Enough to support the plant mechanically, supply capillary water and
at least some air contact. As in the avocado pit on toothpics in a glass
of water.

>
> The porosity is what I'm trying to ascertain.

From the seed's point of view porosity doesn't matter. It needs
water, mechanical support and air.

>
> But how do you compact the soil to make sure the water is all capillary?
>

Just drain off the standing liquid.

>
> Do you want to see pictures of my test bed?

Won't help me, but it might let others get a hint what you're doing.
Better, disperse a sample of soil in water and dump it into a
cylindrical glass jar. Let it settle overnight. Photograph it in good
light with a ruler adjacent. Just possibly you're dealing with some
unusual soil.

hth,

bob prohaska