Because crops grow so fast in the hoophouse, the organic matter in the soil is consumed at a rapid rate. Each new crop requires a fertility boost. In the fall, we prepare our beds by removing all the summer crops, and spreading about four wheelbarrows of compost per 4' × 96' (1.2 × 29 m) bed. This rate is a generous 46 gals/100 ft2 (or 680 L/36 m2 bed). A full wheelbarrow generally holds six cubic feet (44 gallons or 170 liters). 1 ft3 = 7.5 US gals. An inch of compost is about 8 ft3/100 ft2, or 60 gals/100 ft2; 20 gals/100 ft2 is 15 tons/acre (8.6 L/m2). Other professional growers use anywhere from 12–40 gals/100 ft2 (5–17 L/m2). Some use much more.
There are three concerns about using too much compost: high phosphorus levels, raised salt levels and nitrate accumulation. Some growers like to do two years of high compost rates (40 gals/100 ft2, 17 L/m2 or more), then reduce the rate to half that and add fish or kelp, at only 5 oz–8 oz/100 ft2 (15–24 gm/m2) per year. Sustainable alternatives to compost include organic pelleted chicken manure, alfalfa meal, etc.
We added in an annual broadforking a few years after we put up our hoophouse, when we noticed that despite our best efforts, we were walking on the edges of the beds and compacting them. Initially we simply loosened the edges of the beds with a digging fork. We then noticed that the plants on the edges grew better, and we realized the whole bed width needed loosening. If you have designed your hoophouse to use tractor equipment there, that will deal with soil compaction. We wanted our hoophouse to be free of internal combustion engines and fossil fuels, and the broadfork has provided the solution. Ours is an all-steel broadfork from Way Cool Tools.
We set nylon twine to mark the bed edges, holding it in place using sod staples. The string alone has not been enough to stop us walking on the bed edges. Loose soil is important because our winter crops grow all the way to the edges. After spreading compost, we broadfork the beds, then vigorously work the compost into the top of the soil with scuffle hoes and rakes. We learned the hard way the importance of raking the soil to a fine tilth immediately after broadforking — you don’t want to let the broadforked clumps dry out into bricks before you rake!
When I posted Sowing hoophouse winter crops on my website in Sept 2017, I wrote about our bed prep method and tools, and also our outdoor sowings for transplanting into the hoophouse, with a special focus on suitable lettuce varieties.
We had just started planting our late fall, winter and early spring crops in the hoophouse. We pre-sprout our spinach for a week in a jar in the fridge. Soak the seed overnight, drain it in the morning, fit a mesh lid on the jar, and lay it on its side in the fridge. Once a day, give the jar a quarter turn to tumble the seeds and even out the moisture. If the seeds are a bit wet when you need to sow them, and clumped together, pour them out on a cloth to dry a bit before sowing.
On September 6 and 7 we sow five crops in our first bed – spinach, tatsoi, Bulls Blood beet greens, radishes and scallions. On September 15 we sow lettuces, chard, pak choy, Chinese cabbage, Tokyo Bekana and Yukina Savoy, in an outdoor bed to be transplanted into the hoophouse in a few weeks, after we’ve prepared another bed.
We plant crops closer in the hoophouse than outdoors, and closer to the edges of the beds. We don’t have many weeds in the hoophouse, and the paths are marked off with twine, to keep us from stepping on the beds. We find that the soil does slump and compact some of its own accord, even if we don’t step on the edges (and of course, some feet do find themselves on the bed edges), hence the once-a-year broadforking.
Step-by-step guide to how we do our fall bed prep:
1. First remove the summer crops to the compost pile,
2. Spread a generous layer of compost over the whole bed surface.
3. Remove the soil staples and move the drip tape off to one side or the other,
4. Broadfork the whole bed, but not all at once. Only broadfork the amount of space you have time to rake immediately, otherwise the warm hoophouse conditions dry out the soil and make it harder to cultivate into a fine tilth, which is the next task. We tackle 1/3 bed each day.
To use a broadfork, go backwards working the width of the bed. Stab the tines into the soil and step on the crossbar, holding the long handles. Step from foot to foot until the crossbar touches the soil, with the tines all the way in, then step off backwards, pulling the handles towards you. This loosens a big area of soil, which hopefully crumbles into chunks. Lift the broadfork and set it back in the soil about 6” (15 cm) back from the first bite. Note: you are not inverting the soil – this is not a "digging over" process. Step on the bar and repeat.
Sometimes we use a rake, breaking the clumps up with the back of the rake, then raking the soil to break up the smaller lumps, and reshape the bed. More often we use a wide stirrup hoe very energetically. This isn’t the job stirrup hoes were designed for (that’s very shallow hoeing), but the sharp hoe blade does a really good job of breaking up clumpy soil.
5. We’ve found it important to lay the drip tapes back in place in between each day’s work, so that the soil gets irrigated when we run the system and stays damp. We don’t want dead, baked soil.
6. Once the bed is prepared, we measure out the areas for different crops and mark them with flags.
7. Next we use our row-marker rake (bed prep rake) from Johnny’s Selected Seeds.
8. After the rowmarking, we deepen the furrows if needed (often it’s not needed), using a pointed hoe, then sow the seeds.
For more on winter hoophouse crops, see more posts on my website, such as
Planning winter hoophouse crops for our step-by-step process for hoophouse crop planning
Cold-tolerant lettuce and the rest, our January 2018 assessment of the varieties we grew that winter and which survived the unusually cold spell we had.
Excerpt from The Year-Round Hoophouse Pam Dawling and New Society Publishers
Pam Dawling works in the vegetable gardens at Twin Oaks Community in central Virginia. She often presents workshops at MEN Fairs, as well as sustainable agriculture conferences. Pam also writes for Growing for Market and other magazines. Her book, Sustainable Market Farming: Intensive Vegetable Production on a Few Acres, is available at www.sustainablemarketfarming.com, Pam's second book The Year-Round Hoophouse will be published by New Society November 20, 2018. Her blog is on her website and also on facebook.com/SustainableMarketFarming.
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