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Competency Area 6: Considerations in Replanting Decisions

PO 28. Recognize when major Northeast crops are most susceptible to specific environmental stresses such as frost, defoliation, drought, etc.

Corn:

  1. Flooding-most vulnerable during emergence and then from the first true leaf (V1) to about the V5 stage or just before the growing point emerges from belowground. Flooding can greatly reduce emergence rates or greatly reduce existing stands. Mild flooding at this stage will delay growth and development of corn and reduce yield.
  2. Frost-anytime after the V5 stage (growing point above the ground so no longer protected) until black layer formation (R6 stage).
  3. Drought-most vulnerable from about 2 weeks before silking (R1 stage) until about 2 weeks after silking. Severe drought stress at this time can reduce yields by 50% or more.
  4. Heat-same as drought stress.
  5. Cold stress-emergence to V5 stage or later. Crop will yellow and grow poorly.

 

Soybean:

  1. Flooding-same as corn-early in the season (emergence until R1-flowering stage) crop will yellow up and could become diseased. Also, flooding at the R1-R3 stage can reduce nodulation.
  2. Frost-can take a light frost (30o F or so) at the cotyledon- 1st unifloliate leaf stage (V1 stage). After that, growing point is exposed and there will be significant damage if frost occurs.
  3. Drought-Pod development through seed fill (R3 through R6 stage), but particularly seed initiation stage (R4) to through seed-fill (R6.0).
  4. Heat-same as drought.
  5. Cold stress-emergence-cool wet conditions can reduce emergence and cool wet conditions during vegetative development (V1-R1) can hurt early crop growth and lead to diseases.

Wheat:

  1. Flooding-usually in early spring when crop is breaking dormancy and into the early tillering stage (GS3)-wet soil conditions can drown out the crop or lead to freeze and thaw injury (heaving young wheat plants out of the ground).
  2. Frost-tolerates cold conditions until the jointing stage (GS6) and then will tolerate a light frost until anthesis stage (GS 10.1).
  3. Drought-most vulnerable to drought stress at anthesis or flowering stage (GS10.1) but dry conditions can also hurt grain-fill (GS10.5-11.0). But wheat is a pretty drought tolerant crop and dry and warm conditions in the Northeast usually have no negative impact on wheat yields.
  4. Heat-same as drought stress
  5. Cold stress-once the crop is at the jointing stage (GS6-growing point is above the ground), very cold temperatures (<24o F)