NC State Extension Publications

Introduction

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Organic production systems are based on management practices that promote and enhance farm biodiversity, biological cycles, and soil biological activity. Organic agriculture strives to minimize use of off-farm inputs and relies on management practices that restore, maintain, and enhance soil ecology and the farm landscape. Growers considering organic grain crops need to recognize that success will depend on developing a diversified crop management system, including an appropriate rotation plan. We developed the recommendations in this guide to help growers tailor soil health and pest management strategies to fit their specific conditions.

Components of Organic Production Systems

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Table 2-1 lists the key components of an organic production system. The choices made for each component will affect the choices for other components as well as soil fertility and pest management.


Table 2-1. Components of cropping systems.
Components Category
Crop sequence

Rotations
Cover crops

Crop Management Variety and hybrid selection
Planting depth
Planting date
Plant population
Row width
Harvest and storage
Soil Management Tillage practices
Fertility
Pest Management Weed management
Insect management
Disease management

Crop Sequence

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An organic production system begins with selection of the best rotation sequence of production crops and cover crops based on a field’s specific characteristics. This is particularly important in the first few years of an organic production system because the transition period will set the conditions for success. Rotation sequences should be designed to do the following:

  • Reduce weed pressure by minimizing the amount of weed seed produced and reducing perennial weeds
  • Increase the amount of mineralizable nitrogen in the soil
  • Reduce the incidence of insect and disease pests by eliminating hosts and interrupting pest life cycles

This goal usually requires combinations or rotations of crops that attract or harbor different insects and diseases, fix nitrogen, inhibit weed growth, and enhance the soil. Organic flue-cured tobacco crop rotations present a minor departure from these rotation sequences. Because flue-cured tobacco requires relatively low levels of nitrogen early in the season, rotations should be developed that supply the crop with its nitrogen needs without excess, as too much nitrogen can negatively affect leaf quality. The following crop sequences are recommended for organic commodity crop production in North Carolina.

Wheat – Red clover (or other forage legume) – Corn

Wheat and the legume provide continuous groundcover, help break up pest cycles, reduce warm-season weeds through the mowing of clover, and increase available nitrogen. Tilling the clover into the soil makes nitrogen available for the succeeding corn crop. Growing the legume for two seasons will result in more nitrogen returned to the soil and a longer period between corn crops to break pest insect and disease cycles. However, in systems without livestock, the legume cover crop might have little economic value unless it can be cut and sold for hay as an organic forage crop.

Wheat – Soybean – Corn

This classic rotation is also used by organic farmers. Traditionally, both double-cropped and full-season soybeans are used in the rotation in roughly equal proportion. Some organic farmers are emphasizing more double-cropping for a variety of reasons—from economic to agronomic. The main reason is that soybeans planted after wheat usually suffer less pigweed competition. The first flush of pigweed emergence is larger than subsequent flushes of growth and occurs in May. Double-cropped soybeans planted in June must contend with fewer emerging pigweeds. To successfully double-crop more often, consider alternatives to wheat as a winter crop. Disease buildup can occur when wheat is grown on a field too frequently. Both barley and canola have proven to be profitable winter crops. Barley is a preferred feed grain for dairies and often commands almost the same price as corn. Canola contracts have been offered by AgStrong (see “Buyers”) for the last several years.

Wheat – Corn – High value crop

The acreage of organic tobacco, sweetpotatoes, and other wholesale vegetable crops has continued to increase in North Carolina. Wheat and corn have provided valuable rotations, both economically and for managing pests. Soybeans are sometimes included in this rotation. But concerns over inadequate weed management in soybeans increasing the weed seed bank have limited enthusiastic use in some regions.

Tobacco – Summer cover crop – Sweetpotatoes

The relatively high profit margins for organic tobacco and sweetpotatoes allow this sequence to devote a growing season to a summer annual cover crop. Sunn hemp and sorghum-sudangrass are typically grown as the summer cover crop, either as a monoculture or biculture. These cover crops have the benefit of breaking up weed and pest cycles while also fixing nitrogen (sunn hemp) and producing abundant residue (sorghum-sudangrass). Although this system works for many, caution should be taken when following sweetpotatoes with a grass crop as wireworm populations can increase. Further discussion on this rotation can be found in chapter 14, “Organic Market Outlook and Budgets.”

Transitioning to Organic Cropping Systems

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A switch to organic production from conventional agriculture requires a 36-month transition period. That is, there must be 36 months between the last application of a prohibited substance and organic certification. Experienced farmers can use their skills, knowledge, and experience with conventional crops as a base to build new proficiency with crop rotation, cover crops, mechanical weed control, record-keeping for certification, and marketing of organic crops. Most North Carolina farmers can go organic with little capital investment; however, mechanical weed equipment, separate storage facilities, or both may be needed.

It is advisable to begin transitioning to organic with a relatively small acreage and carefully chosen fields. Fields with low weed, insect, and disease pressures and with relatively good soils give the best chance of success when starting with organic production. Fields with more intense pest problems or soil requirements may take more experience with organic production to be successful.

Although crops produced during the transition to organic might be marketed for a premium over conventional crops, return will be less than for certified organic crops. For example, some grain buyers in North Carolina and the Midwest are looking for nontransgenic (non-GMO) corn and soybeans, which must be used in transitional production. Some livestock producers in North and South Carolina are also looking for nontransgenic grains for feed and are willing to pay a small premium. These markets may be harder to identify than traditional organic markets, but they can provide economic incentives during the transition years required to change from conventional to organic farming. Some of these buyers register with the Buyers of North Carolina Organic Grains website.

Farm Profile: Burch Farms, Inc.

Burch Farms, in Faison, NC, produces about 1,000 acres of certified organic wheat, butternut squash, and sweetpotatoes on Norfolk and Goldsboro soils. Burch Farms plants cover crops, sometimes before and after each cash crop, to improve soil quality and add nitrogen to the soil with legumes. The rotation can be flexible. But generally, butternut squash and sweetpotatoes follow Austrian winter pea cover crops. Wheat follows sweetpotatoes. Crimson clover and vetch or Austrian winter peas and oats cover crops are planted in the fall to overwinter between the butternut squash and sweetpotatoes. These mixtures provide nitrogen, increase soil organic matter, and improve soil structure, while preventing erosion. Once the wheat and butternut squash are harvested, a cover crop of sorghum-sudangrass or buckwheat is planted to improve the soil the remainder of the summer. Buckwheat, a very competitive warm-season annual, grows quickly and has a fairly short lifespan (fully flowering at 35 to 45 days). It fits well in a rotation after a summer crop and before the first frost, where it can quickly provide cover in a field, preventing late warm-season annual weeds from germinating. Currently, along with fertility provided by the overwintered cover crops, Burch Farms is applying up to 7.5 tons of farm-produced compost (roughly 64 pounds N per ton available in the first year) per acre, depending on the most recent soil and tissue samples, before each vegetable and grain crop.

This rotation works well in an organic production system because it is fairly long (at least three years), is very diverse, and includes cover crops that are used to build soil health and fertility.

Having grain crops in the rotation also provides a benefit to the farm in terms of labor and marketing. Organic corn and wheat are low-return crops compared to organic sweetpotatoes and other vegetables. However, corn and wheat are relatively easy crops to grow, require little labor, and have lower production costs. With the price premiums for organic corn and wheat, these crops are very profitable, and the farm is glad to have them in the rotation.

Authors

Extension Organic Production Systems Specialist and Assistant Professor
Crop & Soil Sciences
Professor and Extension Specialist, Corn/Soybeans/Small Grains
Crop & Soil Sciences
Associate Professor and Extension Organic Cropping Specialist
Crop & Soil Sciences
Extension Assistant
Crop & Soil Sciences

Publication date: June 24, 2019
AG-660

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