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Competency Area 8: Cropping Systems

PO 34. Compare and contrast single crop systems and crop rotations such as corn-alfalfa, corn-soybean, wheat/clover, etc. for:
A. Yield
B. Soil structure
C. Soil nutrient status
D. Insect pests
E. Pathogens
F. Weeds
G. Economic

Crop rotation:
Crop rotation increase crop yields as opposed to the single crop system.  A corn-soybean rotation can lead to a 10% yield increase for corn and a 5% yield increase for soybeans.  A corn-alfalfa rotation increases corn yields 10% independent of the soil fertility contribution.

B) Soil Structure
Crop rotation can improve soil physical conditions. A Corn – alfalfa rotation improves soil structure for the corn crop because of the deep-rooted alfalfa.

C) Soil Nutrient Status
Crop rotation can increase soil N status for the corn crop whereas this benefit is absent in a single crop system. Examples include a corn – alfalfa crop in which there is no need to sidedress N or a corn – soybeans crop growers can reduce sidedress N rates on corn.

D & E) Insect Pests & Pathogens
Crop rotation helps break the pest cycle, especially with pathogens and insects.  Crops like wheat must rotate because of soil-borne disease problems which can build up in a single crop system. Soybeans must rotate if nematodes, fusarium (sudden-death syndrome), or white mold are a problem. Corn-soybean rotation is used for Corn rootworm control in corn in the Northeast

F) Weeds
Cover crops can be effective in disrupting weed cycles. For Example corn – wheat rotations which are summer and winter crops.

G) Economic
Diversification of crops reduces economic risk.  Growing a corn-soybean-wheat rotation helps absorb some risk.  If it is an excellent year in the Midwest resulting in corn and soybean prices being low in the Northeast, wheat price may be up.
Cover crops allow allow for better utilization of labor and equipment. Wheat is planted in September, topdressed in April, and harvested in July. This doesn't interfere with management practices on corn and soybeans.
Cover crops can however require more equipment than a single cropping system only.  Growers will need a row crop planter and grain drill. Corn and small grain head also have different harvest equipment needs.

Double-cropping systems
Another option is a double cropping system when two or more crops are harvested from the same field in a single season. The first crop is harvested as soon as possible then the second crop is no-tilled or planted into reduced tillage system to save time. Usually the earliest maturing small grain is used which has no effect on yield, then plant an early maturing second crop which has a lower yield potential. If conditions are dry, this can result in crop failure or very low yields of the second crop.

  • Wheat - soybean in Southeast
  • Barley - corn in California
  • Northeast-difficult to do because of the shorter growing season