Comparison of raised beds, sheet mulching, and tilling: a three-year study of home gardening methods

The short version:

In the past 7 years, I have built three types of garden beds at my current location.

  1. Plowing of local soil, with horse manure added.
  2. Sheet mulching.  Corrugated cardboard over sod, covered with a variety of materials.
  3. Raised beds. Sides made of composite decking or 2x8s, placed directly on sod, filled with garden blend soil and/or horse manure.

I’ve had all three types for at least three years now, and I’m ready to proclaim a winner: raised beds. Plowing was an abysmal failure.

The details: (After the jump)

Plowing

Year 1

Salsa gardenI had a neighbor plow under sod and weeds in a 12’x100′ strip of our clay-filled yard and smooth it out for planting.  think I also put about a foot of horse manure over the top of this.  A few tomatillo plants and peppers were planted the first year on part; compost crops like alfalfa and radishes went on the other part. The greenhouse ended up on part of this strip in October.

Year 2

DSCN1451Planted corn and squash and harvested rye.  The rye yielded 1 lb per 100sf and the corn was completely annihilated by raccoons and deer. Weeds were starting to get out of control, especially in the rye area, so I covered the entire area with cardboard and a foot of horse manure (sheet mulch). Planted winter wheat, one patch in rows and one patch broadcast.

Year 3

Wheat?Planted sugar beets (in a patch we weeded by hand to remove sods of weeds) and potatoes (in a fairly weed-free area) The sugar beets never emerged from the straw; I blame slugs because I mulched them with straw that had overwintered outside.  Replanted the beet area with squash, which did OK but were never really robust.  The potatoes yielded about 1/2 lb per sf (half or a third of the rate of my “good” garden beds). The row-planted wheat succumbed entirely to weeds.  The broadcast wheat made it just about to harvest and the deer ate every last kernel.

Year 4

Weeds taking overI looked at the grass and Canada thistle taking over the beds and declared the area a total loss.

The upshot:

Plowing was an abysmal failure for me. I’m never plowing again if I can possibly help it, and I’m never making a garden bed with that many linear feet of edge backing up to grass and thistles with no solid border between them.

Sheet mulching, a.k.a. “lasagna gardening”

Year 1 – fall

DSCN1450Laid down huge sheets of cardboard directly on the sod (20’x20′). Covered cardboard with about 8″ of fluffed-up straw, then a foot of horse manure (half composted and mixed with straw), then maybe 6″ of garden blend soil.  Possible the dirt was on top; I forget exactly.

Year 2

DSCN1547Made paths of straw and planted potatoes, sweet potatoes, brassicas, squash, and cantaloupe.  The squash and cantaloupe all succumbed to squash borers but the other things did pretty well.

Year 3

Garden July 2010Added another 20’x20′ bed: cardboard with horse manure (this time mixed with both straw and wood shavings).  No layer of straw, and no dirt added. This section got a Three Sisters garden and the 2 year-old section got potatoes, brassicas, and black-eyed peas.  The three sisters garden was 2/3 failure and 1/3 OMG success: the squash went nuts and produced something like 300 pounds of winter squash.  The beans never thrived, and critters got the corn again, despite the thicket of squash vines and a nylon stocking placed over each ear.

Other crops did quite well: potatoes yielded 1.5 lb/sq ft and black-eyed peas grew 7′ tall.  It was a bad year for brassicas, meaning we had enough to eat all summer but not enough to share or freeze.

Creeping Charlie and grass (something with big rhizomes…quack grass?) were really starting to move into the beds by the end of the season and it became clear that beds with no edge would be succeptible to weed infiltration annually.

Year 4

New raised beds May 2011Converted entire area to raised beds, with cardboard in the bottom and filled with garden blend soil.  Put down weed block fabric and stone chips on the paths.  Goal is to completely eliminate edge where grass and other rhizomes can creep in.

The upshot

Building up is better than plowing down.  The main difference between sheet mulching and raised beds is simply the absence or presence of wooden sides to the beds – and the sides make a huge difference in maintenance time.

Raised beds

Potatoes and peasThese are still my all-time favorite.  I won’t go year-by-year, but I will say they that after 7 years, they continue to offer the best yields with the least work year by year.  Weeding is truly very minimal, and almost never resembles sodbusting.  Just put the frame on a flat area and fill with at least 8″ of heavy material – soil and/or manure – and that will kill the sod. Weeds can get in at the corners, so try to keep the sod away from the boards.

Framing materials

I’ve used composite decking material and untreated pine lumber.  I will not use the decking material again. It bows too much and has gaps that make it easier for rhizomes to come in at the corners.  Instead, I like 2″x8″ lumber, in whatever length makes sense.  I’ve had untreated beds holding dirt for 6 or 7 years and am not noticing any rotting.  Tacking a 1″x2″ “sacrificial” furring strip on the bottom might be good for longevity; if that rots, you could flip the bed up, pull off the 1×2, put a new 1×2 on, and carry on with the same 2×8.

Garden 2008I usually just drill pilot holes and use 3″ deck screws to hold the corners together – to braces, blocks, or brackets.  Most have held, but a couple have pulled apart.  I just push those back together and re-screw, or, in a couple cases, add an external L bracket to bandage it back together.

Filler materials

Beds need some dirt and some manure; just manure isn’t good enough to support many crops (beans, tomatoes) though some seem to appreciate it (squash).  If you fill a bed with just manure and put tomatoes in it, you’ll have blossom end rot until the tomatoes get their roots into the soil below, at which point they’ll do OK because they can access the minerals in the soil.  However, after a year, 8″ of manure compacts down to 5-6″ of soil, and the worms and roots and such have done a pretty good job mixing the manure and soil even if you don’t get in with a digging fork to help. Still, when I top off the beds, I try to use something with some mineral content (i.e., dirt, not just more compost).

Summary

As much as I admire the idea of building up soil, and as much as I feel bad importing materials to garden in, and as much as I grumble about paying for garden soil and framing wood, I really stand by my decision to use raised beds.   Now that they are installed, I can keep up soil fertility with compost produced on-site.  I don’t have to kill myself weeding or preparing beds each spring – a 4’x8′ raised bed can be completely weeded, composted, and ready to plant in about 10-15 minutes.  I don’t have to own, rent, or use a rototiller or tractor; I can maintain the gardens entirely without burning fuel other than elbow grease.  Yields are fantastic – I’ve raised squash and potatoes in multiple kinds of beds and the tilled area yielded only about 1/3 the weight of produce of an equal square footage in the other kinds of beds.  I know not everyone can afford to buy materials for a raised bed, but you can often scavenge them (wooden pallets for sides, perhaps?) and they make such a difference in ease and yields that I strongly recommend them to anyone trying to carve a garden out of a lawn.

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14 Comments

  1. Ed Bruske said,

    May 25, 2011 at 7:36 pm

    Fantastic report, Emily. My own efforts at sodbusting and regularly amending soil with compost have yielded great results, but the beds are very small–3.5 x 15–compared to yours and easily managed.

  2. aimee said,

    May 26, 2011 at 5:57 pm

    THANK YOU! Very useful information for me. I have been plowing, and find that the weed-load is more than I can bear – I just don’t want to spend three hours a day bending over and pulling deep-rooted weeds like burdock and dandelions. I have had decent luck with sheet mulching, planting perennials like raspberry canes and rhubarb. I still have to weed around the edges but so far I’m keeping them at bay. I have no raised beds – but the last couple years I have greatly expanded my container gardening. I have a couple of bathtubs and a dozen or so large boxes and buckets. These work great for most of the crops I like – chiles, tomatoes, squashes, peas, beans, greens, and herbs. This year is the first year I haven’t rototilled at all – and so far that means I am just not planting those crops that need to go in the ground – carrots, corn and potatoes.

  3. varmentrout said,

    May 30, 2011 at 3:22 pm

    I still love getting my hands into garden soil. Partly it depends on how well you keep it cleaned up – I don’t have thistles etc. any more but I do keep fighting turfgrasses that seed in, and clover.

    One advantage to raised beds in weather like we’ve been having is that they should drain rapidly – I imagine yours have been mostly plantable through all this rain, and my garden is mud.

    Some people use city compost as their sole filler for raised beds. This seems like poor support to me, and I’m interested to see that you do use some soil in yours.

  4. ReesieKitty said,

    June 19, 2011 at 8:28 pm

    Just found your blog and really enjoying it! We have a small yard, but are gardening in two raised beds for veggies and strawberries and another for herbs, We also have a long bed- not raised, where I rotate tomatoes and beans (as a nitrogen fixer) and I want to build those up and enclose them too. I just started a new bed for beans and mixed veg in our front yard and the amount of weeds there as opposed to the raised beds is crazy. After the initial effort in getting them built, I am totally convinced that for our smaller garden, raised beds are the way to go!

  5. pixilated2 said,

    June 22, 2011 at 9:52 pm

    I have 4 raised beds and I have a 25 by 40 ft area that I overwinter by sheet mulching. I use all the straw and wood chips from the chicken run and the goose bedding to completely cover everything. In the spring my husband rototilled the whole thing and now my hard clay is hand workable. Problem: weeds – grass mostly. The geese are working over the grass, but I have to watch them closely or they will eat things I don’t want them to! I would love to make all raised beds, but can’t afford to bring in filler soil. Tomatoes, beans, squashes, melons and sunflowers are doing well, as are the handful of confiscated cotton plants I planed into the companion flower bed. Not exactly a roaring success, but it is a start.

  6. Keith said,

    August 18, 2011 at 12:42 pm

    I have used decking boards to build raised beds and you are definitely right about them bowing. They do look attractive though, once you have built them.

  7. Cloud said,

    December 29, 2011 at 2:04 pm

    I must confess that I am a little frightened about the idea of planting a thousand plants in the 17-1800SF space we are developing. The downstairs ‘family’ room in our Tri-level is going to have to be rows of tables/flats and hanging fluorescent lights to get everything going…. *shrugs* Guess it gets easier and more of a flow to it, the further along you go. :D

    • Emily said,

      December 29, 2011 at 2:46 pm

      What are you planning to start yourself? I’m not a huge tomato/pepper person, so I just buy those at the A2 market. Plenty of variety, and organic/local, too. Other than that, I start my own kale and…that’s pretty much it. Everything else is direct-seeded. Much less fussy and not so time- and energy-consuming. Harvests aren’t noticeably delayed, either, except in the case of full-size solanaceae. (Volunteer cherry tomatoes ripen about the same time as the transplanted ones, though!)

      Over time, I bet you’ll find out what is really worth your time and effort for what YOUR household likes to eat. Oodles of heirloom tomatoes? Piles of peppers? Or more of a Jeavons-style garden where 90% is calorie crops (which all do well direct-seeded…don’t mind his exhortation to transplant wheat and beets!) and only 10% is stuff like tomatoes and lettuce.

      • Cloud said,

        December 29, 2011 at 4:55 pm

        From your experiences, you do not feel it is necessary to start much at all in flats prior to moving to the beds to have them a few weeks old by the time thaw comes?

        • Emily said,

          December 29, 2011 at 9:11 pm

          Correct – for what I grow. Any root vegetable, any seed larger than a grain of rice – those go directly in the ground, as far as I’m concerned. Things that really need the head start are hot weather crops like tomatoes, peppers, and eggplants – and I buy those seedlings, because I only need a few of each, and I’m very happy with the seedlings I can buy locally. I sometimes buy onion and leek plants, too.

          If you wanted 50 tomato plants, or want very specific varieties, or want to save your own seed, you might decide it’s worth the trouble to start them yourself. Or that starting from seed helps stave off the crazies in February! :) In my eternal search to simplify my gardening, I only grow kale from seed, because I’m picky about varieties and usually plant them out into the greenhouse long before seedlings are available.

          I think Jeavons is nuts for transplanting as much as he does. But then, he has a bunch of interns, and a growing season that is just long enough that he can get in 2 crops in many beds if he starts things in flats. That’s not going to happen in Michigan, except for a very few things: turnips, radishes, lettuce, peas, and onions, in my experience.

  8. Gabriela said,

    February 21, 2012 at 8:46 am

    Hello Emily,

    Wow that is an incredible report you’ve developed here :). I’m thinking of building some raised beds myself, and looking for some data about yield. I see you report data from your “mulched” land, but could you please offer some about the raised beds?

    By the way, if anyone knows about any other scientific-like reports about yields with this method, I would really much appreciate it. Im finding data like “from twice to four times the normal yield”, but would really like to be able to do the math myself!

    For you and other “introduced in the matter”, do you think of it only as a hobby, or is it really possible to feed a family (with a big garden) this way?

    Thanks for your effort! (and excuse my English) It’s cool to see people bothering to help others by reporting their results :D

    Gabriela

    • Emily said,

      February 21, 2012 at 11:29 am

      Gabriela-

      I get 1-1.5lb of potatoes per square foot in raised beds, but only 0.5lb/sf in the plowed area. A few other figures for my raised beds:
      Green beans: 0.3 lb/sf
      Collards and kale: 1+lb/sf (4.8 kilos per square meter)
      Onions: 0.5 lb/sf
      Tomatoes: 2 lb/sf
      Snap peas: 0.4 lb/sf

      Another way to look at it: for a family of two, I raise all of our potatoes, summer squash, winter squash, greens, snow peas, onions, garlic, sweet potatoes, and green beans. The only produce I buy in a year are carrots (which I can’t seem to grow), cabbage, and non-local produce (and tomatoes, in years I don’t grow those). In addition, I gave 750+lb of potatoes, greens, and winter squash to the local food bank, and 1/3 of all my beds are planted in legumes, which regenerate the soil. So I think it is completely possible to sustainably grow all the produce needed in raised beds at about 350sf per person.

      This needs supplementation with grains, dry beans, eggs, and meat, as desired, but it can be a very large part of your family’s diet.

      • Gabriela said,

        February 21, 2012 at 12:25 pm

        Hello Emily, thank you for your prompt response and for all those data, they are very helpful and positive for me :) I hope I can get to those numbers in my area too!

        Thanks again and congratulations for your site


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