Crop Rotation in the Garden

Winter 2019-2020
A crop rotation with spring-sown oats interplanted later with transplanted squash.
One rotation I use is spring-sown oats interplanted later with transplanted squash. I flatten and then mulch over the oats in July. The following spring I transplant cabbage into the mulch. English photos

By Will Bonsall

We usually hear about crop rotation in the context of large farms where folks are talking about crops such as wheat, oats, corn, clover and maybe potatoes. I find rotation no less useful in my intensive-bed subsistence gardens, and although I also grow those aforementioned field crops, the principles behind rotation apply no less to my mixed vegetables.

The fact that all of my gardens are laid out in permanent, wide (but not raised) beds makes it a lot easier: I know exactly where every crop was last year, what went under it and what was planted with it. Yes, with it – virtually all of my crops are planted with one or more companion crops, which makes the whole business a bit more complicated. Moreover, some of my crops overlap in timing, which creates yet more complication. Despite that, lots of options exist for rotation, turning this complexity to my advantage. My choice of crops in the rotation can maximize my reasons for and benefits from rotation.

Growing the same crop in the same place year after year fosters the buildup of disease pathogens and pests in the soil; rotation tends to break their cycles. Crops do not require the same nutrients, so rotating them helps in fertility management. For example, legume crops such as peas and beans “fix” nitrogen from the air into nitrogenous compounds that plants can use, which enables legumes to follow heavy nitrogen-feeding crops without necessarily needing nitrogen applications to the soil beforehand. While growing, nitrogen-fixing bacteria in the root nodules not only produce nitrogenous compounds for the plant itself (and perhaps a little surplus for the neighboring companion crop, although I don’t count on that), but after the crop is removed – especially if the nodule-covered root mass is left behind – it leaves the soil fertile in nitrogen for a heavier-feeding rotation crop to follow, saving the need to fertilize before or after (depending on the nitrogen fixing capacity of the legume). Therefore, if a bed were planted to a companion crop that included, say, peas (for example, peas and carrots), I wouldn’t plant beans, favas or garbanzos there the following season. Aside from the fact that they may share some of the same diseases (e.g., ascochyta blight), it’s also wasteful to plant them in soil that has a surplus of nitrate when other crops might benefit more from it.

Of course fertility includes much more than nitrogen. As I mentioned, I also grow wheat and naked oats, and those are especially helpful with my rotations. Aside from the fact that they’re a completely different class of plants – monocot grasses as opposed to dicot broadleaf crops – they also create a large amount of humus-building residue in the form of straw and stubble. Moreover I sometimes oversow my grain with clover, which again complicates the timing but gives a further fertility boost in addition to the food crop.

My example of peas and carrots makes another complication: I not only don’t wish to follow one legume with another, but I also prefer not to follow carrots with another member of the Umbelliferae family (aka Apiaceae), which might foster alternaria blight, aster yellows, etc. So whether or not I know which diseases I have or how serious they are (and generally I don’t, as I’m lousy at pathogen ID), I’m on the safe side by avoiding that whole family for at least two years. Over the years I’ve developed a whole toolkit of useful companion combinations so that most of my groupings that include carrot family members (parsnips, celery, coriander, etc.) do not include legumes but rather some completely different set of companions (for example, celery and beets). That actually simplifies things a bit.

If my rotated plots are some distance from where they grew the previous year, that can further deter pests that overwinter in the soil and emerge in the spring searching for their host plants.

Timing is another consideration with rotation crops, especially since some of my crops (or combinations) overlap another season. Here’s one example: I always interplant corn with soybeans – field corn with dry soy or sweet corn with edamame. Either way I always oversow clover (usually ladino) after hilling in early July. The clover makes a slow start, especially in the shade of the corn, and only starts putting on serious growth after the corn comes out in September. It makes modest growth up until snowfall, but that is greatly enhanced if I let it overwinter and resume growth in early spring. The only hitch is that to get that maximized growth, I must leave the clover until at least Memorial Day, when I can follow it by a heavy feeder such as potatoes. That works fine as long as I’m planting a short-season variety. Tomatoes also work very well that way, but since I plant a lot more corn than tomatoes, I need to balance the mix with other crops. On the other hand, if I were to follow corn with winter wheat (yes, most gardeners don’t grow grain, but I do), I can let the clover grow until August or September, removing at least one cutting of clover for compost or mulch elsewhere.

Some crops that come out very early, such as onions, garlic, peas and early lettuce, leave ample time for a clover crop, which can run over into the next season. This is much like my corn example except that with corn the clover grows concurrently with the crop as a living mulch; here I’m referring to a succession crop. Even if it is too late to put in tomatoes, several vegetables can be sown for a late fall crop, often as late as mid-July. Late lettuce, carrots, beets, turnips and sometimes rutabagas can be direct seeded, whereas kale and summer cabbage (Early Jersey Wakefield) can usually be transplanted from a nursery bed, and Egyptian onions from bulbils, with reasonable assurance of a fair late crop, especially given the boost from the clover. It is important to provide ample moisture for those crops to thrive in late summer heat.

One of my favorite rotations is designed to avoid the need to cultivate for at least two seasons. I’ve described this in other issues, but will repeat it here: In very early spring I seed an area to common oats for a green manure/living mulch to precede/accompany a crop of squash or pumpkins. A week or two before setting out the hills of squash (started in 4-inch peat pots), I chop in the ankle-high oats only where the hills will go and let the rest of the oats keep growing among and around the squash hills. In early July I flatten the knee-high oats by flopping down a half-sheet of plywood and treading on it, and then I cover the oat thatch with a further mulch of old leaves (to really kill the oats) and then enough spoiled hay to keep the leaves from blowing. This combination renders the bed completely weed-free and very rich for the squash and whatever crop I choose to follow it. However, since I want to get a second year of use out of that same mulch, which is still largely intact, I must follow with a crop that is widely spaced enough to use transplants rather than closely spaced direct-seeded crops. My usual choice is cabbage, which I plant as seedlings through the old mulch, 2 feet in each direction. The cabbage transplants like the cool, moist, fertile soil, and they get a strong start with little pest pressure. I always need to refurbish the old mulch with an additional layer of grass, but this enables me to get a whole second season of crops without disturbing the soil or expending a lot of energy, beyond cutting and spreading the mulch. I’m still working on ways to extend this no-till series for yet another season – such as with grain amaranth – but even if I turn it all in at the end of year two, I can forget about adding anything to the enriched soil. Either way it’s a win-win.

Unlike the more conventional rotations (oats, corn, clover, etc.), my rotations are necessarily much more complicated, and I like that. Simple systems do not mimic natural systems, which are vastly more complex. And like Nature, I’m constantly fiddling with other companions and sequences to see what works best, or at least better.

About the author: Will Bonsall lives in Industry, Maine, where he directs Scatterseed Project, a seed-saving enterprise. He is the author of “Will Bonsall’s Essential Guide to Radical Self-Reliant Gardening” (Chelsea Green, 2015). You can contact him at [email protected].

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