Pit and Mound Gardening

Hang out in sustainability circles for any length of time and you will notice a distinct antipathy towards traditional vegetable gardening. It ruins the soil; it is dependent on inputs; it eschews perrenial plants. It is un-natural. And in most cases that is all true.  But there are some real truths that this attitude can gloss over.  First, annual vegetable gardens are wicked productive – easily a pound or more per sq ft.  Second, the vast majority of us are used to eating food grown in annual vegetable gardens and food habits are extremely difficult to change – they are a integral part of our living culture and that changes slowly;  I am much more likely to eat potatoes than skirret or sunchokes, no matter what the permaculture books tell me.  Third, its gonna take YEARS for your multi story permaculture forest garden to start producing much of anything.  For certain, eventually it will outpace your annual gardens in productivity, but that is a decade or more out.  Until then, the 25#’s of harvest per tomato plant is gonna make you and your larder a lot happier.

So whats a suburban homesteader to do?  I’ve read thousands of pages on sustainable vegetable gardening – fantastic books from John Jeavons, Elliot Coleman, and many more that have inspired and intrigued me to the possibilities of vegetable gardens.  I’ve also read thousands of pages on ecology and soil science that contradict so very much of what those masters and mistresses have to say; tilling is very rough on the soil.  I want to have healthy soil, but I also need and intend to have a large canning garden for years to come.  Mulch Gardening like Ruth Stout’s “No – Work” garden and Lee Reich’s Weedless Gardening makes a great step towards integrating the two philosophies by removing much of the tilling.  Word to the wise though on this – Ruth Stout gardened conventionally for over 7 seasons before switching to no-till.  It takes a long time to build up your soils and you also need to irradiate persistent perennial weeds like quack/couch grass, sow thistle, and the like if you have them on site.  No till gardening is a journey, not a destination!

Bolstered by some impressive results from 2009, I mulched heavily this year and was very impressed with the reduced weed and irrigation inputs.  But the garden was still flat and that bothered me.  So at the market garden I tried a new technique that I want to explore Whole Hog in 2011.  Essentially it is based on a side bar blurb in Chapter 12 of David Blume’s epic opus Alcohol Can Be a Gas. Now a book on homebrewed energy revolutions is not a place one would expect to have an epiphany on vegetable gardening, but David is a die hard permaculturist so its all connected.  His idea was to dig trenches under your paths, fill them with mulch, and then use these mulch paths to breed up trillions of red worms to function stack a “wasted” space in the garden.  This idea worked wonders at the farm – with the beds I used this technique out producing my conventional beds by 20-50%.  As the season went on, I gave it more and more thought and always paid special attention to those two beds – digging and poking around as I tended to them.    My findings in short were these:

• Mulched Trenches improved drainage -essentially turning the planted areas into raised beds
• Mulched Trenches improved water retention – the mulch acted like a sponge, holding water for weeks and weeks between rains keeping a higher water table within reach of the annuals
• As hoped, Mulched Trenches foster just ridiculous amounts of fungus.  My hope was that even with the soil intrusion in the beds from potato harvest the fungus would live on in the paths to re-innoculate the soil for the next season.  The mycelium was often inches thick and brilliant white to the naked eye.  Bingo!
• Thanks to the moisture and fungus, the Mulched Trenches are havens for earthworms, even if you don’t plant worms in them, they will be there soon enough.
• Within only 3 months, a 1/8″ (3 mm) layer of humus formed under the straw that mulched the potatoes and was clearly evident to the naked eye when harvesting.  That is very impressive soil building in such a short time.  Now, this was on incredibly microbially rich soil that has been farmed organically for 20 years so your results may vary, but it is no wonder why straw mulch gardening works.  You are truly “uppening” your soils!

All of this really coalesced with the epiphany that  my Mulched Trenches essentially mimic “pit and mound” topography in old growth forests and were creating all kinds of interesting micro climates for soil fauna and plant roots to exploit.  Wait a minute – the reviled and ecologically barren annual vegetable garden was starting to sound a lot like permaculture!  I was on to something.

With that in mind, I set out to integrate these learnings into my freshly “pimped out” garden as I prepped it for the 2011 season.   The layout will be a 1′ Mulched Trench on each side of 30″ growing beds.  Now that is a lot of path, and purists will give me hell for that.  Whatever!  To manage a 1100 sq ft garden, be a husband, father, and still work a full time job and do all my other projects if I can’t get into my garden easily and efficiently it will turn into a mess faster than you can say “fundamentalist”.   I plant in straight lines – it may not be efficient in space, but it is incredibly efficient in time and labor – we need to factor those things into our plans too.  Mandalas are great, but they’re not for me.  While digging the trenches the soil was piled up onto the 30″ growing beds – mimicking a “double dug” bed.  On top of this I applied .5-1″ of compost and topped that with 4″ of straw with a nod to Ruth Stout.  Here are some pics:

1' deep and about 1' wide - basically dig a trench with a spade and pile it onto your garden bed. As these paths are to be semi permanent I pulled some lines to keep me honest.

Once the trench was dug and emptied, I filled it with chips. I like to use fresh chips with leaves in it if I can - the nitrogen helps to feed the soil ecosystem. Tamp the chips well (walk on them) and mound them slightly as they settle. I aimed to keep them about level with the top of the growing beds. As the trenches are 3/4 full, rake the growing beds flat to get them back to 30" width and then top the trenches off. Figure a cu ft per running foot - these beds are 32' (9.7 m) long so it takes over a cu yard each.

After the growing beds are raked flat, I put down a .5" (13mm) layer of compost which is enough to cover the soil. More is better, but the most important thing is to inoculate the bed with soil bacteria which will munch slowly on the straw all winter and add some humus.

At this point the beds are built and the straw is laid down.  That is all pretty straight forward.  But before I sign off I would like to show some examples of just WHY this is so important:

This was from one of the chipped paths from this summer's garden. These chips were only 4 months old - just LOOK at that fungal growth!

This is also  my answer to any concerns about “locking up nitrogen” by adding this much carbon to the soil.  The fungus is working like crazy to break it down, plus the soil in the growing beds is normal and the nitrogen concerns will only be in the paths or just next to them.  And once the plant roots start exchanging sugars with the path fungus the soil economy will go bonkers to the benefit of your pantry through increased yields.  Just so you understand that this wasn’t an isolated  shot her are some more pics — all from the same row!

Almost 4" thick - the fungal net was already reaching well below the chip layer. Again - this is 4 months or less of growth!

These fungal nets capture nutrients and water reducing leaching and feed worms (see him?) and other soil fauna. Fantastic!

I am an unabashed Soil Geek, but these discoveries had me beside myself, jumping, hollering, and dragging my wife and kids out to see the bounty growing under my paths. Wow.

So there it is, my Pit and Mound gardening method.  Essentially I am taking straw mulch gardening -the tomatoes and other big plants will grow right into this mulch- and taking it up a notch with a healthy dose of soil ecology by fostering fungus, worms and all their buddies in the “permanent” paths.  This also reduces labor by increasing the gardens ability to self irrigate by essentially creating contour swales next to each bed.

Time will tell how much of an impact this will have.  But I do know that some of the best soils on my property are found UNDER my wood chip paths, humus is formed from carbon after all.  Any question about the efficacy of fungus to make soils is erased by going out to a nearby woods and rummaging under the leaves – its amazing.  In addition to the paths, the growing beds now more precisely mimic a natural soil structure – beneath my garden is the sub soil, then a foot of top soil, the the “duff” layer of partially decomposed material in the compost I applied, and topped with raw organic matter in the mulch.  EXACTLY the same strata you will see in a prairie or forest.   Its still a veggie bed, but we’re a helluva lot closer to building more sustaining system as it holds water, suppresses weeds, and builds soil and soil ecosystems.

Be the Change!

-Rob