CROP ROTATION PRIMER

Problem:     Growing the same crop in the same field year after year weakens the soil and promotes harmful insects and diseases.

Solution:     Plant a different crop each year.  Alternating unrelated species allows soil to rest and breaks reproduction cycles of diseases and pests.

Example:     Rather than sowing Wheat — Wheat — Wheat, grow Red Clover — Potatoes — Wheat.

Rotation Science:     Each species roots at different depth and takes varying amounts of minerals.  Rotating crops gives soil time to replenish these nutrients.  Every variety has its own cast of villainous insects and debilitating diseases.  Alternating different plants each season starves harmful organisms by denying them hosts on which to feed.

How To Do It:     Following is a list of strict rotation rules.  Obey these instructions and your crops will thrive.  Ignore the rules and you will spend unpleasant sums for costly pesticides, nematicides, and fungicides.

Rule-Of-Thumb:     Never follow a crop with a similar or botanically related species.  Thus:

Rule:     Never follow a grain crop with a grain crop.  Examples:  Oats & Wheat.  Maize & Barley.  Note:  This rule applies to all true cereals = grass crops.

Rule:     Never follow a leaf crop with a leaf crop.  Examples:  Spinach & Lettuce.  Cabbage & Chard.

Corollary:     Never follow a broad leaf plant with a broad leaf plant if there is a better alternative.  Example:  Sunflower & Collards.  Sunflower & Millet is a better choice (broad leaf plant followed by a narrow leaf = grass plant).  This rule is not always easy to follow but keep it in mind especially if nematodes are a problem.  Grasses suppress most nematodes.

Good Practice:     Rotate nematode resistant crops where these parasites cause economic losses:  Asparagus, Arugula, Barley, Broccoli, Cabbage, Castor Bean, Collards, Cowpea, Crimson Clover, Grasses (Poaceae), Hairy Vetch (winter vetch), Jack Bean, Joint Vetch, Kale, Lupine, Maize (corn), Marigold (Tagetes species), Millet, Mustard Greens, Mustard Seed, Oats, Partridge Pea, Rapeseed (canola), Rice, Rye, Sesame, Showy Crotalaria, Sorghum, Sudan Grass, Sunn Hemp, Velvet Bean, Wheat.

Rule:     Never follow a root crop with a root crop.  Examples:  Carrots & Potatoes.  Onions & Sugar Beets.  Note:  All roots, tubers, corms, and bulbs are called “root crops”.

Rule:     Never follow a fruit crop with a fruit crop.  Examples:  Tomatoes & Peppers.  Watermelons & Gourds.  Cucumbers & Eggplants.

Rule:     Never follow a seed crop with a seed crop.  Examples:  Buckwheat & Sesame.  Caraway & Fennel.  Note:  “Seed Crops” include “pseudo-cereals” (Quinoa & Amaranth) and “Oil Seeds” (Safflower, Flax, Sunflower).

Rule:     Never follow a flower crop with a flower crop.  Examples:  Poppies & Zinnias.  Marigolds & Nasturtiums.

Rule:     Never follow a vine crop with a vine crop.  Examples:  Gourds & Pumpkins.  Cucumbers & Squash.  Note:  Some rotation rules overlap.  This repetition is deliberate.  Gourds, pumpkins, squash, and cucumbers are fruit crops, vine crops, and in the same botanical family = 3 reasons not to follow these crops in close rotation.

Rule:     Never follow crops sharing common diseases or insect pests.  Example:  Tomatoes & Watermelons are both susceptible to anthracnose.

Rule-Of-Thumb:     Highly aromatic plants = herbs “cleanse” the soil.  Examples:  Basil, Oregano, Sage, and Thyme.  This rule dates back to the Middle Ages and is especially useful for market gardens and other small spaces.  If you cannot think of a better rotation follow cash crops with herbs or strongly scented flowers like Marigolds.

Rule:     Alternate legumes with cash crops whenever practical.  Examples:  Red Clover & Sweet Corn.  Crimson Clover & Cabbage.  Frost Beans & Green Peppers.  Why buy costly synthetic fertilizer when you can grow nitrogen-fixing legumes?  Let nature pay your fertilizer bills!

Corollary:     Plant legumes with cash crops whenever practical.  Growing 2 or more species together is called polyculture.  Examples:  Pumpkins & Dutch White Clover.  Barley & Chickling Vetch.  Sweet Corn & Pinto Beans.  Cotton & Crimson Clover.  Potatoes & Frost Beans.  Seed multiple species in the same row, in alternate rows, or broadcast together.  For best results use short or non-climbing legumes that will not interfere with harvesting equipment.

Rule:     Use 7-year rotations whenever practical.  Example:  Flax — Sweet Clover — Wheat — Lentils — Rapeseed (canola) — Pinto Beans — Sunflower.  Long rotations are essential to control insects and disease organisms that live in the soil.

Rule:     Alternate cash crops with forage crops whenever practical.  Examples:  Safflower — Winter Rye & Winter Vetch & Forage Turnips.  Winter Barley & Austrian Winter Peas & Tillage Radish — Sunflower.  Forage Maize & Velvet Bean — fall Broccoli or other cabbage family crops.

Good Practice:     German farmers have a long history of planting Landsberger Gemenge” = Hill Mixture = Mountain Mixture = Waste Land Mixture = multi-species forage crops sown on land unsuitable for plowing.  Typical mixes include 1 cereal or grass + 2 legumes + 1 cabbage family plant or root crop.  For example:  Winter Rye + Red Clover + Winter Vetch + Forage Kale or Turnips.  This combination of cereal, legume, forb, and root crops makes a balanced diet ideal for grazing animals.  Cattle gain 2.5 to 3.5 pounds daily when feeding on forage mixtures of 4 or 5 species.

Historical Note:     Farmers in the Middle Ages planted “The Twelve Apostles” = a mixed species forage crop with 4 grains + 4 legumes + 4 root or broad leaf crops.

Rule:     Practice sabbatical rotation whenever possible:  Let fields rest every seventh year.  Grow weeds or multiple species cover crops to restore soil structure and fertility.  Example:  Caraway Seed — Red Clover — Sunflower — Berseem Clover — Winter Rye — Soy Beans — Mixed Grass & Alfalfa Hay Crop.

Rule:     Grow crops in narrow strips rather than large fields.  Plant adjacent strips with unrelated species.  Adjust strip widths to fit planting and harvesting machinery.  For best results strips should not exceed 200 feet wide on flat land or 50 feet wide on hills or slopes.  Example:  4 rows of Sweet Corn — 4 rows of Snap Beans — 4 rows of Sunflower — 4 rows of Sweet Potatoes . . . .  Note how tall crops alternate with short crops.  This increases light penetration into the canopy and greatly reduces pest populations.

Rule:     Plant cash crops with companion plants whenever practical.  Use short cover crops that will not compete with taller cash crops.  Example:  Oats & Forage Peas & Turnips.  Harvest oats with a “stripper header” then graze peas & turnips.  Historical Note:  Farmers in the Middle Ages grew polycrops called The Holy Trinity = 1 cereal grain + 1 legume + 1 root crop.

Rule:     Include multiple species cover crops in farm rotations whenever practical.  Use multi-species cover crops just like legume cover crops.  Mixed species cover crops and legumes can be freely substituted in any crop rotation.  Growing multiple species cover crops is the best way to improve soil tilth and increase soil organic matter.

Good Practice:     Experience has shown that mixed species cover crops effectively control pests and diseases.  However, it is best to be cautious.  Thus, a corn and soybean farmer should not include either maize or soy in his cover crops.  This principle applies to all cash and cover crops.

Rule-Of-Thumb:     Mixtures of plants grow better than isolated species.  full synergistic effects require at least 8 cover crop species.  There is a certain minimum number of species that must be present before soil biology reaches maximum activity.  this “tipping point” appears to vary depending on location and plant varieties.  Some farmers include 30 species in their cover crop mixes.

Generic Cover Crop Mixture:     2 warm season grasses + 2 warm season legumes + 2 warm season broad leaf plants + 2 cool season grasses + 2 cool season legumes + 2 cool season broad leaf plants + 2 or more root crops = 14 or more species cover crop mix.  Broadcast not less than 20 pounds per acre or drill in 2-inch deep furrows spaced 7.5 inches apart.

Rule-Of-Thumb:     Include 50% legumes by weight in mixed species cover crops to provide sufficient nitrogen for following cash crop.

Science Note:     Cover crops containing many species can fix substantial amounts of nitrogen even if few or no legumes are present.  Agronomists speculate that this nitrogen comes from free-living soil bacteria.  Also, symbiotic bacteria fix more nitrogen when mixtures of legumes are grown with plants that do not fix nitrogen.  Maximum synergistic effects are noted in cover crops with 20 or more species.  Ideal number of species is not known.

Rule:     Reserve 5% to 10% of farmland for native weeds.  Grow weeds around fields and in narrow strips between cash crops.  Sow weeds in vineyards and orchards.  Mow weeds only when necessary = at harvest.  Example:  Obtain weed seeds = screenings from local grain elevators.  Sow wherever soil is bare.  Bale weedy fields.  Spread bales of “wildflower hay” wherever soils are weak or pests prolific.  Native weeds are essential to provide food, shelter, and alternate hosts for beneficial insects.  Biological pest control is not effective without native wees growing in close proximity to crops needing protection.

Rule:     Tolerate weeds in cash crops provided density does not exceed 2,500 to 5,000 weeds per acre = approximately 1 weed every 3 or 4 feet equidistantly.  Thin weeds as necessary to protect cash crops from excess competition.  Weeds provide food, shelter, and alternate hosts for predatory and parasitical insects.  Example:  Let weeds grow inside and around tomato fields.  Result:  Save $400 per acre on insecticide costs.

Rule:     For biological pest control, plant cash crops adjacent to native weeds and other plants with small flowers.  More weeds = more flowers = fewer pests = less crop damage.  Rule-Of-Thumb:  If you have a pest problem it means you do not have enough flowers.  Examples:  Plant wildflowers in your vineyard or buckwheat, hairy vetch, and turnips in your orchard.

Rule:     Reserve 5% to 10% of farmland for hedgerows, windbreaks, and wood lots.  For high biodiversity plant not less than 40 species per acre or linear mile.  for best results choose economic species that produce nuts, fruits, berries or other cash crops.  Rule-Of-Thumb:  Everything on a farm should produce income.  Example:  Wildflowers can be harvested for seed or rented to local bee keepers.

Rule:     Break any rule rather than do something stupid.  Rotation rules are based on centuries of practical experience.  Thus, think deeply before trying anything risky.  For example:  Crop rotation can be difficult or inconvenient in small spaces or market gardens.  Solution:  Compromise where needed and apply lots of compost = at least 1 inch deep = 1 pound per square foot.  Soils of high biological activity have strong resistance to pests and diseases.  Rule-Of-Thumb:  Plants with Brix readings above 12% dissolved solids are generally immune to most insects and pathogens.  High Brix levels are directly related to soil organic matter content.  Translation:  More compost = healthier plants = crop rotation is not always necessary all of the time.

Plant Families:     Following is a list of the top 10 botanical families most important to farmers and gardeners.  Use listed species to plan effective crop rotations.

Beet Family = “Chenopods” = Chenopodiaceae:     Amaranth, Beet, Lamb’s Quarters, Mangel-Wurzel (stock beet = forage beet), Spinach, Sugar Beet, Swiss Chard, Quinoa, Redroot Pigweed.

Cabbage Family = “Crucifers” = “Brassicas” = Cruciferae = Brassicaceae:     Arugula, Brussels Sprouts, Broccoli, Cabbage, Chinese Cabbage (bok choy), Cauliflower, Collards, Garden Cress, Horseradish, Kale, Kohlrabi, Mustard (greens), Mustard (seed), Nasturtiums, Radish, Rapeseed (canola), Rapini, Rutabaga, Turnip, Water Cress, Woad (blue dye plant).

Agronomy Note:  Brassicas and Chenopods are good pioneer plants because they do not need mycorrhizal fungi in order to thrive.  Caution:  Do not plant Brassicas or Chenopods if you are trying to encourage beneficial fungi.  Brassicas and Chenopods will not feed mycorrhizal fungi.

Carrot Family = Apiaceae = Umbelliferae:     All plants in the Carrot Family have umbels = umbrella-like flowers composed of hundreds of tiny florets.  Small flowers are ideal “bee forage”:  Angelica, Anise, Caraway, Carrot, Celeriac, Celery, Chervil, Cilantro, Coriander, Cumin, Dill, Fennel, Lovage, Parsley, Parsnip, Wild Carrot (Queen Anne’s Lace).

Cucumber Family = “Cucurbits” = Cucurbitaceae:     Cantaloupe (melon), Cucumber, Cushaw (squash), Gourd, Honeydew (melon), Luffa (sponge), Muskmelon, Pumpkin, Squash (summer, winter, & spaghetti), Watermelon, Zucchini.

Daisy Family = Aster Family = Asteraceae = Compositae:     Artichoke, Calendula, Chamomile, Chicory, dandelion, Endive, Escarole, Everlasting (helichrysum), Lettuce, Marigold, Raddichio, Sunflower, Tansy, Tarragon, Wormwood, Yarrow.

Grain Family = Cereal Family = Grass Family = Gramineae = Poaceae:     Barley, Corn (maize), Durum (wheat) = Semolina = Kamut, Einkorn (wheat), Emmer (wheat), Fonio, Millet, Oat, Rice, Rye, Sorghum, Spelt (wheat), Teff, Triticale (rye x wheat hybrid), Wheat, Wild Rice.  Pseudo-Cereals are not grass plants but are grown and eaten like true grains:  Amaranth, buckwheat, Chia, and Quinoa.

Legume Family = Fabaceae = Leguminosae:     Any plant that has seeds in pods is called a legume.  All legumes fix nitrogen and can be grown as “green manure crops”:     Alfalfa (lucerne), Beans, Carob Tree, Chickpeas (garbanzo beans), Clovers, Cowpea, Castor Bean, Fenugreek, Hairy Indigo, honey Locust Tree, Jack Bean, Lentils, Lespedeza, Lupine, Partridge Pea, Peas, showy Crotalaria, Sunn Hemp, Vetches (tares).  Legumes grown for dry, edible seeds are called “pulses” or “pulse crops”.

Mint Family = Lamiaceae = Labiatae:     Basil, Bee Balm, Bergamot, Calamint, Catnip, Hyssop, Lavender, Lemon Balm, Marjoram, Mint, Oregano, Pachouli, Rosemary, Sage, Savory, Thyme.

Onion Family = Lily Family = “Alliums” = Alliaceae = Liliaceae:     Asparagus, Chives, Garlic, Hyacinth, Leeks, Lilies, Onions, Ramps, Scallions, Shallots.

Tomato Family = Solanaceae:     Eggplant, Peppers, Petunias, Potatoes, Tobacco, Tomatoes, Tomatillos.

Related Publications:     Biblical Agronomy; The Twelve Apostles; Biological Agriculture in Temperate Climates; Polyculture Primer; Strip Cropping Primer; Worm Farming; Managing Weeds as Cover Crops; Earthworm Primer; Planting Maize with Living Mulches; Living Mulches for Weed Control; Crops Among the Weeds; The Edge Effect; Organic Herbicides; Forage Maize for Soil Improvement; Coppicing Primer; Forage Radish Primer; Weed Seed Meal Fertilizer; Intensive Rice Culture Primer; Trash Farming; Pelleted Seed Primer; Upside Down Potatoes; Maize Polyculture Trial 2007 – 2016; No-Till Hungarian Stock Squash; and the Rototiller Primer.

Would You Like To Know More?     For more information on crop rotation and Biological Agriculture please visit:  http://www.worldagriculturesolutions.com  — or —  send your questions to:  Eric Koperek, Editor, World Agriculture Solutions, 413 Cedar Drive, Moon Township, Pennsylvania, 15108 USA.

About The Author:     Mr. Koperek is a plant breeder who farms in Pennsylvania during summer and Florida over winter.  (Growing 2 generations yearly speeds development of new crop varieties).

Index Terms:     Biological Pest Control; Brix Levels (in crops); Companion Planting; Compost; Cover Crops; Crop Rotation; Holy Trinity (grain + legume + root crop polyculture); Landsberger Gemenge (mixed species forage crop); Mixed Species cover Crops; Multi-Species Cover Crops; Multiple Species Cover Crops; Polycrop; Polyculture; Sabbatical Rotation (fallow fields every 7th year); Strip Cropping; Stripper Header; Twelve Apostles (12 species forage crop mix); Weed Management; Wildflower Hay; and Wildflowers.