Shane Kaser

I agree with others who are talking about maximizing the effectiveness of your landscape's carbon/water sequestration via contouring and mulching (chop n drop!!!).

My big suggestion for dry areas is trees.  Nut and fruit trees are much hardier than vegetables.  See J Russell Smith's Tree Crops (free pdfs online).  Trees are also good synergy with animals.  Grazing animals among trees, and feeding them fruits/nuts.

Cheers,
-b

Chop N Drop for woody/perennial/bramble/multifunctional hedgerows.

For the vegetable garden, clover.  In humid climates, sources of cations (calcium!) and micronutrients (kelp!) which get washed out by precip.

Something I haven't seen mentioned (maybe I missed it): Mulch is only a nutrient problem if mix it into the *mineral* soil profile where your plants roots mostly live.  Mulch is typically high carbon, low nitrogen.  It should stay on the surface where it shades the soil, and enters the nutrient cycle on nature's terms (slowly, with the help of a healthy community of microbes, worms, etc.).  So you can mulch as much as works for you in vegetable gardens, but you have to be careful when you dig to honor the layers and avoid mixing them.  Mulch has other problems for veggies though like pesky mollusk/rodent habitats and labor-intensive weeding/sowing/planting.  I like to do mulch/compost piles between hoed veggie berms which also serve as walkways and storm-water catchment/infiltration, and then the plants grow their roots into pile as it suits them.  Many "cover crops" are designed to be turned into the soil for high-disturbance annual-focused agriculture, but introducing tilling I don't think is in the spirit of permaculture, except possibly as an acute remediation technique, and definitely not as a regular part of the agricultural process.

Cheers,

B

Mulch vs. succession:

Mulch is the product of disturbance, and the first step of a succession toward a closed-canopy system.  

Disturbance is redox: combustion, respiration, batteries... It is a chain-reaction release-flow of ecological energy, typically embodied in the ligatures of carbon-based molecules (fuel/carbohydrate).  This release of free-floating carbon into the river of space-time is an opportunity.  Shape your river so that it winds about and steps down a chain of vernal pools held back by leaky weirs.  Remember we're talking about carbon, but the concept is the same as water - the great ocean to which all carbon eventually flows is the atmosphere (as CO2).  Complex carbon into your landscape, and by complex, I mean 1) facilitate interaction, and 2) slow flow.  Chop-and-drop is the most efficient, though not appropriate for all crop situations, ideal for tree/shrub-based systems.  

It is not an efficient use of your human energy to use imported mulch as a long-term weed-barrier.  It constantly breaks down into a perfect (weed)seed-bed, and mulch takes energy!  The next step up the successional ladder is living-mulch (layers of canopy).  Mulch is a spring-board for greater levels of organization, of complexity, of community, which are self-resilient through their dynamism.  The hardest thing for a gardener to do in the landscape is to grow absolutely nothing at all.

Thanks for the topic - close to my heart!
-B

15 years is still young in apple tree years.  They are very resilient trees.

Wood chips are an excellent idea.  Healthy soil mycorrhizae offer immense support for healthy trees.

I have limited experience with comfrey polycultures, but if there ever were a place for this tenacious accumulator, it's as a tree-crop understory plant!

Cheers
-b

In my experience (mostly apples and pears), fruit tree production often unintentionally turns to "espalier-like" structure as the weight of the fruit pulls branches down, and prudent harvesters prune off sucker-whips to keep the harvest (on short fruit-bearing spurs) within easy human reach.  Don't hassle with the circus of posts and wires, and just prune your trees every year like you should.  They may look funny/tortured, but hey it works.

-B

Perhaps thinning the fruit so more energy goes into fewer fruits?  Also prune the tree so that it's not a thicket, and direct its energy where you want it to go?

Some ideas.

sK

Not sure what a clay level is... but it doesn't sound like something that would help poorly draining soil.

The thing about water is that it always comes from somewhere, and it's always on its way to somewhere else.  Where is it coming from (uphill/roof); where is it ultimately going to (downhill)?  Once you have those two parameters identified, then your management options pretty much reveal themselves.  Whether your site is level or sloped, it boils down to shaping some simple redirection topography (and often it doesn't take more than a one-shovel swale/trench to make a significant difference!).  I find it to be really engaging landscape problem solving!

Good luck,
B

I second Nicole Alderman's post.

I vote for

thimbleberry
evergreen huckleberry
salmonberry
salal
oregon grape
sword fern
fringecup
woodruff
strawberry
wood violet (viola adunca)
woodland aster
bear's breech
cornus ('kelseyii' is a 2-3' dwarf version of the native shrubby dogwood)
rhus aromatica 'Gro-Low' (non-poisonous poison-oak doppleganger)

You won't get much human-food from tree-shade, so focus on building the soil/plant community for the bugs/birds/etc.  Think nurse logs, stumps, wood chips, storm-water.

If you can, strategically thinning-prune the trees to allow more sun through.

Cover crop is whatever you and nature allow.

Good luck.

Done alotta sheet mulching, and never seen it affect an established tree... UNLESS you have a pre-existing water-management issue, or you let the mulch build up against the crown/trunk; then you can get crown-rot and/or adventitious surface roots which can girdle the crown and scaffold roots.

Though I think 8-12" is a little on the thick side.  Of course it depends on the material: hay will be bulkier than arborists' wood chips... Basically the paper/leaves are the primary weed barrier; everything else is either soil amendment or paper-weight.  It will rot down soon enough.

Water + Carbon. Together.

This is the secret.  Others have given you good advice to start with water redirection for increased infiltration.  The next level is to use coarse woody debris (logs/stumps, "CWD") to support your earthworks, so that water soaks into the wood (a better sponge than even the densest clay).

Prepare for a cascade-and-pool dynamic as you intercept water; on a slope it is easy for rodents to burrow-drain your swales.  So don't get your hopes up too much about your ability to control/contain water for long.  So it goes.  Or figure out how to become the bane of rodents.

Also, there's lots of talk of mulch, but really, plant roots live and die and inject more carbon *down in the soil* than mulch+worms.  And obviously there's the slope stabilization benefits.  So go low-disturbance, long-lived crop plants (tree/shrub/bramble/vine) if you can.  Yes mulch is great, but don't forget the roots.  Super important.  IMO, mulch's highest contribution to the system is hosting beneficial fungi that network plant roots and CWD.  Think how the internet is a bunch of dispersed users (plants) connected via fiber-optic communication lines (roots + fungal mycellia running through the humic (mulch) layer) and server nodes (CWD).

Have fun!