Soil Management and Fertilizer Use: Crop Rotation

Excerpt from Agronomy Guide for Field Crops (Chapter 2)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Benefits of Crop Rotation
   • Corn Yield Response to Rotation¹- Table 2-4
   • Various Crop Rotations and Their Potential Negative Impacts - Table 2-5
2. Updates on Soil Management and Fertilizer Use: Crop Rotation
3. Related Links...

Benefits of Crop Rotation

Crop rotation is an integral part of the crop production system. The greatest benefit to a good crop rotation is increased yields. A well-planned crop rotation will help with insect and disease control and will aid in maintaining or improving soil structure and organic matter levels. Using a variety of crops can reduce weed pressures, spread the workload, protect against soil erosion and reduce risk. Legume crops in the rotation have become more valuable with the increased cost of nitrogen. Research and experience have proven that a good crop rotation will provide more consistent yields, build soil structure and increase profit potential.

The basic rule of crop rotation is that a crop should never follow itself. Continuous cropping of any crop will result in the buildup of diseases and insects specific to that crop, and cause a reduction in crop yields. The more often that crop has been grown in the field in the past, the greater this impact will be. For example, the practice of growing two or more years of soybeans is becoming increasingly common. Perhaps the greatest impact of back-to-back years of soybeans has been the accelerated spread of soybean cyst nematode (SCN). For more information and potential yield reductions, see the section Soybean Cyst Nematode. The increased number of years of soybeans in the rotation is also increasing the susceptibility of Ontario's soils to erosion. In fact, the structure of soils in corn-soybean rotations can actually be poorer than that of soils that are in continuous corn production. For example, a recent study found that erosion following an intense June rainstorm in first-year corn following 2 years of soybeans was twice as high as following corn, wheat underseeded with red clover or alfalfa. Relatively poor soil structure after 2 years of soybeans not only increased erosion susceptibility but also reduced soil porosity, that resulted in less rainwater infiltration. Reduced rainwater infiltration increases the likelihood of erosion risk, yield-reducing water ponding and/or soil moisture deficits; all of these effects can reduce crop productivity, particularly in years with weather-related stress.

The greatest benefit from crop rotation comes when crops grown in sequence are in totally different families. The two families are grasses (monocots) and broad-leaves (dicots). The grasses include forage grasses, cereals and corn. Soybeans, white beans, alfalfa and canola are examples of broadleaf crops. Table 2-4, Corn Yield Response to Rotation, provides an example of the type of response to crop rotation that is possible.

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Source: Vyn, University of Guelph

¹On a Toledo loam near Chatham, Ontario, and on a Brookston clay loam near Maidstone, Ontario.
²All corn treatments were fertilized with 179 kg/ha (160 lb/ac) of N.
³Red clover plow-down was underseeded into wheat. "Wheat (RC)-RC" indicates that underseeded red clover was not plowed under but harvested for seed the following year and then fall plowed.

The fibrous root systems of cereal and forage crops (including red clover) are excellent for building soil structure. Studies have shown that the benefits of including wheat, and especially wheat plus red clover, may persist beyond just the following year. Underseeding red clover into wheat resulted in yield increases every year for 3 consecutive years compared to when red clover was not included in 4-year rotation systems.

In choosing which crop to grow, consider the economics of the entire rotation instead of a single crop in isolation. Also, be aware of any potential insect or disease problems that could affect crops later in the rotation. Cover crops in the rotation may also have an impact on diseases and pests, either positive or negative (refer to the section Cover Crops, for potential impacts of various cover crops). Table 2-5, Various Crop Rotations and Their Potential Negative Impacts, displays various crop rotations that are recommended, cautioned against or not recommended depending on their impact on the crop production system. It is not a comprehensive listing of crop problems, but it does highlight the main impacts to be aware of. More information is provided in each crop chapter.

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Updates on Soil Management and Fertilizer Use: Crop Rotation

No updates available at this time.

Related links...

• Soil Management

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