How Many Crops Per M3 Can Be Grown Each Year? How Intensive Can Cropping Be? Are 2-3 Crops A Year Realistic? I Have Easily Grown 7-8 Crops a Year From a Square Metre … Here’s How.
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As a veg and salads grower it was necessary for me to grow several crops a year from every square metre of soil. Anything less wasn’t commercially viable. But how many crops per m3 can be grown each year?
And let’s not forget, it’s not just about growing plenty of volume. It’s also about producing quality crops with great flavour and nutritional quality.
Agricultural Versus Horticultural and Gardening Cropping
In farming only one crop per year is normally grown. They sometimes get sown or planted in one year and harvested the next, but the average is still one crop per yearly cycle.
In gardens, allotments, and in market gardening, the growing of one crop per unit area is unusual. In most cases at least two crops are grown per annual cycle. For example a gardener might grow early potatoes and follow them with leeks. Or they may grow Brussels Sprouts over winter and follow them with potatoes in spring and transplant another brassica, peas or carrots to follow on with.
So two or more crops per year is relatively easy to grow and few pieces of land are occupied with one crop per year. The exception might be a crop of leeks that could be in the ground for 11-13 months max. But in many cases some or all of the crop would be harvested and a second crop could be grown.
But two or three crops aren’t the maximum possible. So what is?
An Extreme Cropping Situation
Whereas one crop per year is an extreme situation it’s possible to go top the other extreme with crops that mature very quickly. Radish is an example.
The RHS claims that radish can mature as quickly as four weeks from sowing. Some seed companies claim the crop can be ready in 22 days. But it isn’t a matter of waiting 22-28 days if we sow the seed in modules that can be transplanted. Multiseeded modules can be transplanted after 10-14 days and that means the crop is in the ground for a much shorter period.
Of course the time to maturity depends on may factors such as variety, day length, temperature etc. And outside of the best growing period the growth rate will be slower. Here is a rough and ready guide to the length of time they take from seed.
- Late winter/early spring: Plant spring radish varieties in late winter or early spring. These varieties will mature quickly and will be ready to harvest in 3-4 weeks.
- Early summer: Plant summer radish varieties in early summer. These varieties are larger and have a longer growing season than spring radishes. They will be ready to harvest in 4-6 weeks but you could grow the smaller faster maturing spring varieties.
- Late summer: Plant autumn radish varieties in late summer. These varieties are best suited for cooler climates. They will be ready to harvest in 5-7 weeks.
- Early autumn: Plant winter radish varieties in early autumnl. These varieties are the most cold-tolerant and can be grown through the winter months. They will be ready to harvest in 6-8 weeks.
- Remember, in a heated greenhouse the crop would grow faster in cooler months. Not that I can afford top pay the heating costs at current prices!
The Basic Assumptions
So assuming we grow from seed drilled in situ, and they average 4 weeks to mature, we could get around 12 crops a year from each area. And if we use multi sown modules we can reduce the 4 week average to around ten days at best. And perhaps six weeks at the slowest time of year.
OK, so that is all theory. But one year I devoted one my polytunnels to radish. We sowed a few hundred modules every few days from February onwards and planted them in a 120×18 ft tunnel. So we effectively had a few hundred sown/planted every two days and harvested on a regular basis to suit demand (demand is always higher at weekends so that means harvesting the majority on Thursdays and Fridays in the main with fewer on other days).
The tunnel was notionally divided into small beds giving around 20 beds in total .. though this varied over the season.
We harvested the last crop in late September as I wasn’t prepared to heat the tunnel .. it was just too expensive. However, most years, in the south we could expect to get reasonable weather for long enough to get at least one more harvest …. possibly two!
An Imperfect Experiment
Our experiment with this was imperfect in the sense ewe couldn’t keep up with the workload whilst running the rest of the nursery. Quite often we harvested a crop and didn’t have enough modules to replace those harvested. So we didn’t maximise cropping.
Having said that, we had eight crops out of most areas. And was we cleared the last of the crop we planted late leeks for the baby leek market we had established in Western International market. We had several chefs from top end restaurants buying these leeks from us.
So, in total that was nine crops from a given area.
I know we could’ve done better. If we had managed to replant fast enough we could have had more harvests. And if we had grown some crops in the hot beds that Jack First uses we could have had faster early crops.
How About Successional Crops in Gardens and Allotments?
No gardener is going to want a garden full of radish. We want a succession of seasonal crops with a bit more variety. And growing 8-9 crops a year isn’t possible in that situation. but that doesn’t mean we can’t grow a lot more than the two crops that some achieve. A biointensive garden can achieve much more than this.
Take this example.
I grew leeks in one bed, harvested in January and then had a quick crop of module raised coriander in early spring. As that was harvested I replaced the crop with a mixed bed of oriental sand leaves/greens, coriander etc. Now, in late April I have already harvested a few leaves from these plants and have planted module raised shallots between the rows.
The oriental salad leaves will continue to crop for some weeks .. perhaps as long as 8 weeks if harvested regularly. By this time the shallots will have grown bigger and need more space and the oriental crops will be removed. Any removed early, or where I find a gap, I have plants a few radish.
Once the shallots are harvested, around late summer, I will replant with oriental salad leaves, coriander etc. They should then crop well into the winter.
At certain times of year, early and late, I’ve covered the crop with horticultural fleece.
So in this bed we will have had leeks, mixed leaves, shallots and mixed leaves followed by late mixed leaves. That’s five crops minimum with some of them cropping over a long period. In fact there aren’t many weeks when something isn’t being harvested. It’s a highly productive piece of land that measures just 3 metres by 1.3m. But of course we needn’t be limited to a single bed, we can grow as many was we want.
Other Successional Rotations
Many sequential sowings can be improved by planting catch crops in the spaces that aren’t growing at a given time. For example, I’ve recently planted Purple Sprouting Broccoli in one bed. They need a bit of space and I’ve planted at 18 inches apart in both directions (different spacings will affect the number of heads and their size .. there is no “right” spacing). So, until they grow much bigger there is a lot of space between the plants. Plenty of room to grow other crops. In my case I’ve planted a few rows of shallots between the PSB. And I’ve interspersed them with radish. So, in effect I have three crops growing on this bed. The radish will harvest in a month or so (it’s from seed), then I’ll get some shallots later in summer, then we’ll have the PSB.
An alternative would be to plant lettuce, beetroot, salad leaves etc between the PSB.
Any crop that needs wide spacings until it fills the rows provides an opportunity to grow a catch crop in the space. Clearly we need to choose quick maturing crops that can be harvested before they compete with the main crop, but the options are varied and provide biointensive cropping opportunities.
Biointensive Rotational Growing Is NOT The Same As An Annual Crop Rotation
Annual rotations focus on what we grow in successive years. Successional cropping, especially when grown biointensively, focus on growing a series of crops in a single area in ONE year.
Of course we needn’t view it as individual blocks of time lasting just one year as seasons just roll on from one year to the next and one successional series can merge into the next year without pause.
So, for example, where the PSB in the above successional plantings are harvested we can quickly plant another crop. I expect my March sown PSB to be harvested in late autumn or early winter at which time I can plant another crop if I wish. Depending when the land is cleared I could easily plant large modules of salad leaves, coriander, spinach or some oriental leaves here in Devon, but in other areas that will be possibly be unviable.
In my case an August or September sowing of Spinach will start yielding in late winter provide I protect it with fleece. In a kind winter it will even crop without fleece. And as the climate changes we are going to see more and more possibilities if we grow biointensively.
Tag: How Many Crops Per M3 Can Be Grown Each Year?
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