UK query: Top Dressing

 
I have a lawn with clay underneath that floods every time it rains; it's
also
full of tree roots.
I have killed the lawn off, built "edges" and a deck/pier to walk
around on. I
plan to top-dress the old (now dead) lawn with homemade
compost and well-rotted
horse manure to a depth of about 6 inches,
thereby introducing organic matter,
and avoiding having to dig too
much. I have "loosened" the soil where possible.
Any thoughts? Anything wrong with this approach? I will not start
planting until
next year (herbaceous shrubs, roses and annual
vegetables).
Is this a sensible strategy? Have I missed anything?
Thanks - Bruce




--
BrucUK

 On 7/26/2009 9:23 AM, BrucUK wrote:

If you create an area with strata of unlike soils, you will find that
plants will not thrive.  Roots of your shrubs and vegetables will not
readily grow through the interface between strata.  Water will not
penetrate through the clay, and you will still have some flooding.

I suggest that you broadcast gypsum over the area, creating a 1/4 inch
coating over the soil.  Lightly water the gypsum to start it dissolving;
then water it into the soil 2-3 times.  This will help break up the clay.

Then rent a power tiller.  When the clay is slightly moist (definitely
not wet), till the area to a depth of two feet.  Top dress with about 3
inches of your homemade compost and well-rotted horse manure.  Till
again to a depth of a foot.  Then top dress again with another 3 inches
of the compost and manure.  Till one more time to a depth of only 6-9
inches.

If you don't walk on the area when it is truly wet, you won't have to
work the area for several years.  You will also find that plant roots
will eventually grow well below the depth that was worked.  However, you
might have to spread more gypsum annually to replace what has leached
away; this will keep the clay porous and well-draining.

--
David E. Ross
Climate:  California Mediterranean
Sunset Zone: 21 -- interior Santa Monica Mountains with some ocean
influence (USDA 10a, very close to Sunset Zone 19)
Gardening diary at <http://www.rossde.com/garden/diary>

 
This sounds like the best plan except that I would grow a deep rooted
cover crop for a couple months first and then proceed with the
above.

 On 7/27/2009 3:22 PM, J.R. wrote:

That would work even better if the cover crop were planted after the
initial gypsum treatment and the first tilling.  The roots of the cover
crop would then more likely penetrate the clay.  Afterwards, a second
gypsum treatment would be appropriate.

--
David E. Ross
Climate:  California Mediterranean
Sunset Zone: 21 -- interior Santa Monica Mountains with some ocean
influence (USDA 10a, very close to Sunset Zone 19)
Gardening diary at <http://www.rossde.com/garden/diary>

 

If water puddles on your clayey lawn area now simply adding a top dressing
won't help, whenever it rains you'd just have more volume of soupy mud...
you need to get down below the clay so it can perc or devise some way to
drain the water away.  My first cause of action would be to attempt a deep
rototilling in hopes of getting below the clay.  Next attempt would be to
create drainage away from that area, perhaps with a series of trenches that
hold perforated pvc pipe and covered with gravel... essentially creating a
leaching field.  Then add a good thick layer of rich soil.  But odds are
that clay runs deep rather than shallow.  To me it seems like you may want
to do something different with that area rather than planting a lawn,
perhaps an attractive flagstone patio built on a porous base.  Good luck.