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Crop Rotation for the small vegetable garden
Carol Hall, Harrowsmith
One of the most effective ways to avoid losing vegetable crops to bugs, wilts, blights and other problems is simple to rotate your crops. But how?
It sounds so easy: Just don’t plant vegetables of the same type in the same patch of soil for at least three years. But when you grow 20 or more different kinds of vegetables every year, each with its own soil preferences, cultural needs, space requirements and crop specific pest and diseases to keep in mind, planning a workable garden rotation can seem like a nightmare.
The benefits of crop rotation are well proven. Rotation disrupts the life cycle of disease organisms and insects by relocating their favourite host plants to a new spot every year, which makes it harder for the bugs to find their victims. The brassicas (broccoli, cauliflower, cabbage and other related plants) require rotation to avoid club root. Potatoes, tomatoes, eggplants and peppers, (members of the nightshade family), require rotation to avoid wilts and blights that overwinter in the soil. Similarly root crops and leafy crops should be rotated to avoid common pest such as root maggots and leaf miners.
Crop rotation also helps keep the soil naturally productive by preventing the depletion of the same nutrients by heavy feeding plants.
Winter cover crops such as fall rye are also an important part of any rotation schedule. They add valuable nutrients and organic matter when they are turned under in the spring. But since some long season crops aren’t harvested until it’s too late to plant fall rye, and other need planting before the turned under rye has had a chance to decompose, trying to work cover crops into the rotation can get complicated. We’ve decided to plant fall rye in the final plot, after harvesting its beans, tomatoes, corn, cucumbers and other war-weather crops. It gets tilled in before planting Plot A (brassicas) the next spring.
Then there’s the matter of lime. Magnesium-containing dolomite lime, the type most beneficial to plants, is also one of the slowest acting. This means the soil for lime-loving plants, like brassicas, really should be amended the previous fall- but only if you have the foresight to know where you are going to plant them. Liming the whole garden is so solution, since some crops do best without lime (fresh lime will make potatoes scabby, and some plants like a more acidic soil). We lime our gardens a quadrant at a time, at the same time and in the same place as we sow winter rye: in Plot D, after the harvest.
Our plan takes care of some major complications, but when you tackle crop-rotation, many more wrinkles come up. Where do the needs of gardeners fit in, for one thing? And, with eight to ten weeks between cool weather plantings (peas, onions, potatoes) and warm weather plantings (squash, peppers, melons), how do you work planting times into the rotation? What about harvest times? Since radishes mature in 25 days or less while winter leeks and Brussels sprouts can take over 120 days, how do you accommodate succession planting? What about just plain convenience, like having your salad crops grouped in one area; your winter storage crops in another? And if you do some how manage to meet all these conflicting needs this year, what do you do next year, when every crop shifts place again?
Don’t despair. The fine tuning of your crop rotation plan will come with time, as ours did. Gardening is a process of discovery. And one of the first things we discovered was counterintuitive: instead of the three-year rotation usually recommended, a four year rotation ;is easier to keep track of, better suited to crop space requirements, and much more practical for grouping crops with similar planting times and/or harvest times. It also makes it easier to custom amend the soil in the fall for crops that will be planted there come spring.
The details are all spelled out in the following chart, but the basic idea is to divide the garden area into four quadrants and group your vegetables into four plots according to their needs for soil fertility and acidity. We start the first plot of right, with added lime, manure and green manure, and as those first, heavy feeding veggies grow, they use up nutrients and affect pH in such a way as to naturally create the soil conditions preferred by the plot that will follow…and so it goes for the remaining two plots, too.
Our rotation plan succeeds by working with nature, not fighting against it. And that’s the best plan of all.
A little fine tuning
The quadrant plan works in theory, but in practice, it might need a little fine- tuning. For instance, leeks are ideally located in Plot C with other cool-weather crops, but because we like to leave ours in the ground all winter, we plant leeks in Plot A, along with kale and other veggies that keep all winter. This also leaves us more room in Plot C, which we desperately need. Over the years, we’ve tinkered with the plan and have learned that if space is short in one quadrant, chances are there’s room in another.
Carol Hall’s Crop Rotation Plan
The basic idea is to divide your garden into four quadrants and group your vegetables into four plots, as shown. Start with Plot A in the top left, Plot B: In THE BOTTOM LEFT< Plot C in the bottom right, and Plot D in the top right corner. Then, come planting time next year, rotate the plots clockwise one stop. It will take four years before each crop returns to its original spot on the quadrant, ample time to foil soil-borne diseases or overwintering insects, and to allow soil nutrients to balance out.
PLOT A
BRASSICA (CABBAGE FAMILY)
CROPS: Broccoli, Brussels sprouts, cabbage, Chinese cabbage, cauliflower, collards, kale, kohlrabi.
NEEDS: These heavy feeders need a deep fertile, nearly neutral soil (pH 6.8-7.0).
PREPARATION: After harvesting Plot D last fall (this year’s Plot A), you will have dug in a generous layer of manure, planted fall rye and spread dolomite lime. Over winter, the lime has been washed in deeply. Turn under the rye as early as the ground can be worked.
PLANTING: Transplant early crops about three weeks after turning under the fall rye. Plant mid-season and late crops (seeds or transplants) from April to June. Late –season storage crops are best as transplants in late May or early June.
HARVEST: Crops are harvested as they mature (some give repeat harvests). Late crops can be mulched for fall-winter harvest.
PLOT B
ROOT CRIOPS
CROPS: Carrots, parsnips, potatoes, salsify, Swede turnips (rutabagas), winter beets, winter radishes (Asian types).
NEEDS: Fertile soil, not too alkaline (pH 6.5); high in phosphorus and potassium but not in nitrogen. No fresh manure (causes hairy roots) or lime (causes potato scab).
PREPARATION: Soil is left reasonably fertile but somewhat depleted in lime by Plot A. Extra phosphorus (bone meal or rock phosphate) and potassium Greensand or kelpmeal) can be added at planting time.
PLANTING: All crops can be planted early, mid-season and or late.
HARVEST: In well drained soil, late crops can be mulched heavily and stored right in the ground until late fall, till heavy frosts.
NOTE: Always plant potatoes on one end of the plot; tomatoes, eggplants and pepper at the opposite end of their plot (Plot D), to prevent these nightshade-family crops from revisiting the same soil before four years have passed and thus avoid soil-borne diseases.
PLOT D
WARM-WEATHER CROPS
CROPS: Corn, cucumbers, eggplant, melons, peppers, pumpkin, summer squash, tomatoes, winter squash, zucchini.
NEEDS: Fertile soil, especially at surface; adequate lime (pH around 6.5).
PREPARATION: Soil has been replenished by the legumes from Plot C and the turned-rye. Lime applied last fall ensures a pH level acceptable to all crops, although lime tolerant peppers may appreciate more. Compost or aged manure can be dug in at planting time or applied as a top dressing.
PLANTING: All crops should be planted only after all danger of frost is past and ground is warm. Melons need consistently warm soil; planting of peppers and eggplants should be delayed until temperatures are above 10*C at night.
HARVEST: Crops are harvested as they mature, but since all are frost tender, harvest is completed by first frost. This leaves plenty of time to dig in manure, plant fall rye and spread dolomite line in preparation for the brassicas crops that will once again occupy the soil as Plot A in spring.
NOTE: Always plant tomatoes, eggplants and peppers on one end of the plot; potatoes at the opposite end of their plot (Plot B), to prevent these nightshade-family crops from revisiting the same soil before four years have passed and thus avoid soil-borne diseases.
PLOT C
LEGUMES, COOL-WEATHER CROPS AND SALAD CROPS
CROPS: Broad beans, green beans, lima beans, peas, celery, green onions, leeks, salad greens, lettuce, spinach, summer beets, storage onions, summer radishes, summer turnips, Swiss chard.
NEEDS: Legumes (peas and beans) adapt to any soil type and need little or no extra fertilizer as long as the soil is high in organic matter. Except for lettuce, all other crops need or tolerate moderately acidic soil (pH 6.0 – 6.5). Most need only moderately fertile soil; onions, leeks and leafy crops need extra nitrogen.
PREPARATION: Soil is left moderately acidic and moderately fertile after Plot B. Turning under straw or hay used for its winter mulch adds organic matter. Extra nitrogen for onions, leeks and leafy crops can be added at planting time, as can extra lime if required for lettuce.
PLANTING: All crops except green beans and lima beans (both warm weather crops) can be planted as soon as the ground can be worked. Salad crops can also be sown in succession or to follow very early crops (broad beans, peas).
HARVEST: Most are repeat harvesters. Leeks, Swiss chard and succession-sown salad crops can produce well into the frosty period. At summer’s end, turn plot over (leaving a corner for fall-producing crops if desired), plant fall rye and lime lightly.
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