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Make Soil For Your Raised Beds

How to build the best soil for your raised garden beds -- recipe included!

Raised Bed GardenAdding some raised beds to your garden this year? Great idea. I’ve seen it said that raised beds produce about four times the amount of produce as do row crops. Plants seem more vigorous there in early season, probably because the soil in a raised bed warms faster than that in the garden patch. As gardeners, we love early season growth.

None of this is true, of course, if the soil in your raised bed isn’t at its best. And that’s the great things about raised beds. You can dig them out and fill them as you like. Think of them as a controlled experiment in which you’re looking for just the perfect mix of organic materials — including beneficial microbes and other living things — and naturally occurring nutrients like nitrogen and minerals.

The easy way is to just buy topsoil and compost, in bags or not, and fill up the bed’s box. If you have your own compost, or can get reliable, organic compost — we were lucky to get it from a local, organic dairy goat farm — it’s worth making your own soil recipe. That way, you’ll be able to fine-tune it for particular crops. Growing tomatoes? Make your soil slightly acidic, just the way they like it. Growing greens? You’ll want to keep the nitrogen low until you have germination.

If you’re using compost, make sure that it’s completely finished. If you’re adding manures of any kind, make sure they’re completely composted and are no longer “hot.” Mix in other materials, like peat, pumice or vermiculite if you’re looking for good drainage, or sand, which root vegetables like. The easiest way to make sure compost is garden-ready is to spread it in the fall, leaving it on the surface to finish through the freeze and thaw cycles of winter.

If you didn’t spread compost in the fall or just don’t have any to spare, you can make it on the spot and grow in it as you do. We’ve stuck a bale or two of straw in raised beds in the fall and were left with good results when we pulled the remnants off in the spring.

Not only does the bale smother any weeds that might try to poke up early, it conditions the soil beneath where it sits. We even know someone that placed a bale right on the sod where he put his box in August and finished up with top soil when it came time to plant next spring. Personally, I’d go to the trouble to dig out all the sod ahead of putting down bales. But that’s just me.

If you’re putting in new raised beds this spring, why not put your first planting right in the straw bales? The craft of straw bale gardening has grown in popularity and for good reason. Some gardeners skip the box altogether and just grow in the bale.

The Perfect Raised Bed Soil Mix

Good organic garden soil is the single most important ingredient for healthy, nutritious vegetables. It is loose and fluffy — filled with air that plant roots need — and has plenty of nutrients and minerals essential for vigorous plant growth and bountiful yields. Filling your raised beds is an opportunity to get high-quality soil and to fine-tune the mix of fertilizers and amendments.

The following soil mix was developed by Planet Natural to fill a 4’ X 8’ raised bed one foot deep (32 cu ft).

5 bags Black Gold Peat Moss, 2.2 cf x 5 = 11 cf

3 bags Teufel’s Organic Compost, 3 cf x 3 = 9 cf

4 bags Worm Castings, 1 cf x 4 = 4 cf

3 bags ​Organic Chicken Manure, 1 cf x 3 = 3 cf

2 bag Therm-O-Rock Organic Vermiculite, 2 cf x 2 = 4 cf

3-6 lbs Azomite

1-2 lbs Kelp Meal

3-6 lbs Oyster Shell Flour

2-4 lbs All-Purpose Fertilizer

Have on hand all the ingredients for your soil mix before you start filling the beds, and pre-mix as much as possible, on a large tarp if necessary, to avoid pockets of peat, manure or any other ingredients.

Note: Do NOT use pressure treated wood or railroad ties for your raised bed frame because of chemical leaching.

Once the hay bale growing is over, your raised box will be left with good-quality left behind from the composted straw. You can hasten the process by adding some compost or top soil which you’ll probably do as part of sticking plants in the bale. Either way, the soil inside your raised bed will benefit.

Bales provide good moisture control. They also warm faster in cool weather and insulate, if damp, in warm. And while you’re growing cucumbers with the help of a little soil or compost out of the top, the bale is making soil for you on the bottom.

Not all bales are created equal. Baled hay and pasture cuttings will contain weed seeds, something that can bring problems into your garden. Straw, if it’s what’s left after seed heads have been harvested, usually contains little weed seed. The terms seem interchangeable at time. A glance at the bales you’re buying should tell you which they really are, no matter what they’re being sold as.

There’s lots of advice out there on how to fill your raised beds. Let us know what you’re using, either in the comments section or on Facebook.

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