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Competency Area 6: Considerations in Replanting Decisions

PO 26. Know the minimum stand for major Northeast crops before considering replanting. Recognize factors that result in thin stands of Northeast crops.

Determining stand density:
Plants/acre = (plants/ft) x (43,560 sq ft/acre) / (row spacing [in]/12in/ft)
Plants/acre = (pants/sq ft) x (43,560 sq ft/ acre)

  1. Measure out 1/1000 of an "acre in several representative areas of the field.
    • 30" row -17' 5"
    • Number of plants x 1000 = plants/acre
  2. Measure out plants in areas of the field.
    • Determine sq. ft. in measuring area.
    • 43560 sq. ft./ sq. ft. in area = correction factor.
    • Plants counted x correction factor = plants/acre.

Example: measure off 25ft over 4 rows (30” spacing) 4- 25 ft. rows at 30” spacing = 250 sq. ft.

Plant Counts
Row 1= 36 plants
Row 2= 33 plants
Row 3= 34 plants
Row 4= 35 plants
Sum = 138

(43560 sq. ft./ 250 sq ft) x138 plants= ~24,000 plants/acre

Minimum stands and replanting in the Northeast:
Forage Crops
Poor seedbed preparation, incorrect seeding rate of pure live seed, improper seeding depth, and incorrect seeding date can all result in thin stands, and can all be controlled. Excess moisture or drought conditions cannot be controlled and may also result in poor stands. It is impossible to assess the success of a perennial grass seeding by counting plants per unit area. Grasses have the ability to eventually spread out over the open spaces and fill in a stand. If essentially no plants are visible after all should have emerged, replanting is a consideration. A spring seeding may not be replanted till late summer, and a late summer seeding requiring replanting may not be accomplished till the following spring. Alfalfa seedings should have at least 10-12 plants per square foot (20-30 is optimum), or they will not have a good chance of coming through the first winter with an adequate full stand.

Alfalfa
Desired alfalfa stands:


Year


Desired Plants per Square Foot

Fall 1st (seeding)

15-20

Spring 2nd

10-12

Spring 3rd

3-5

Spring 4th

3-4

Dig up roots, look for rot, and insect damage. Consider replanting if the stand has fewer plants than noted in the table above or uneven stands (lots of skips). Grass can help and may tilt towards keeping the stand. Weeds will NOT help and may tilt the decision towards replacing the stand

Corn
Usually don’t replant grain corn if the final stand densities are ≥16,000 plants/acre and plants are evenly distributed throughout the field. For silage, final stands should be less than 18,000 plants acre before considering replanting. If there are major skips in the field, it may pay to go in and replant portions of the field where final stands are extremely low.

Effects of skips in 20 feet of row:

Grain:

  • 2 foot skip = no effect
  • 3 foot skip = 5-10% yield loss

Silage: 2 foot skip = 5% yield loss

Questions to consider in making a replanting decision:
Do first planted seedlings have:

  • Well developed roots?
  • A good start?
  • Good weed control?
  • Two-thirds of a stand?

REMEMBER: Later planting costs one bushel per day in grain yield, so yield is hurt no matter what!

 

Troubleshooting poor crop emergence


Seed appearance


Likely problem

1. No seed, no sign of seed

Planter problems

2. Seeds soft, rotten

Seed dead when planted

3. Seeds hard, not germinated

Dry soil or dry pockets in trash

4. Seeds gone, seedlings lying on soil surface

Birds (pulling up plants to get seeds)

5. Seeds gone, signs of scratching or digging

Squirrels or (less likely) birds

6. Seeds dug up, germs gnawed out, leaving half-moon shaped endosperm

Mice or rats

7. Seeds have holes in them (worms may be present)

Seed corn maggot or wireworm

8. Seeds present, root system okay, plants cut off near or at the base

Cutworm

9. Seeds okay, plants small, roots stunted and/or “burned” at tips

Fertilizer burn/injury