Evaluation of Corn Stands

May 1, 2003 10(7): 56-57

Joe Lauer, Corn Agronomist

Corn planting has progressed faster and earlier than normal in most areas this year. Many farmers have finished planting corn and are turning their attention to soybean planting. As corn plants emerge stand evaluations and assessments will be made on fields. For guidelines on assessing plant population in corn fields, see UWEX Bulletin A3353 "Corn Replanting or Late-Planting Decisions" (http://cf.uwex.edu/ces/pubs/pdf/a3353.pdf).

Nearly every farm has a field with poor plant emergence due to weather conditions, pests and/or crusting. Evaluating stands is a six-step process:

  1. Determine plant population of the field (use 1/1000th acre)
  2. Evaluate plant health: if health is suspected count as ½ plant
  3. Assess the uneveness of stands see http://learningstore.uwex.edu/Uneven-Emergence-in-Corn-P172C0.aspx
  4. Compare the yield of a reduced stand to that of a replanted stand
  5. Calculate replanting costs
  6. Factor in risks of replanting

The following tables are provided for southern and northern Wisconsin. These tables provide data on the impact of planting date and plant population on corn grain yield. Also you can use these tables for corn stand assessments in completing step #4 above – Comparing the yield of a reduced stand to that of a replanted stand.

Expected corn grain yield for various planting dates and harvest populations in Relative Maturity zones of 95 to 115 days (i.e. south and south central Wisconsin)
Harvest Planting date
population April 20 May 1 May 10 May 20 June 1 June 10 June 20
full short full short full short full short full short full short full short
percent of expected yield
36000 96 91 99 95 95 93 85 87 63 71 40 55 8 32
34000 97 92 100 96 96 94 85 87 63 72 40 56 8 32
32000 97 92 100 96 96 94 86 87 63 72 40 56 8 32
30000 96 92 100 96 96 94 85 87 63 72 40 56 8 32
28000 96 91 99 95 95 93 84 86 63 71 40 55 8 32
26000 94 89 97 93 93 92 83 85 62 70 39 54 8 31
24000 92 87 95 91 91 89 81 83 60 68 38 53 7 31
22000 89 85 92 88 89 87 79 81 58 66 37 51 7 30
20000 86 82 89 85 85 84 76 78 56 64 36 49 7 29
18000 82 78 85 81 82 80 72 74 54 61 34 47 7 27
16000 78 74 80 77 77 76 68 70 51 58 32 45 6 26
14000 73 69 75 72 72 71 64 65 47 54 30 42 6 24
12000 67 64 69 66 67 65 59 60 44 50 28 38 5 22
10000 61 58 63 60 60 59 54 55 40 45 25 35 5 20
Figures for shorter-season hybrids are in italics.  The actual Relative Maturities of short-and full-season hybrids vary with location and soil type.  

 

Expected corn grain yield for various planting dates and harvest populations in Relative Maturity zones of 70 to 95 days (i.e. north and north central Wisconsin)
Harvest Planting date
population April 20 May 1 May 10 May 20 June 1 June 10 June 20
  full short full short full short full short full short full short full short
  percent of expected yield
36000 96 82 100 89 97 89 86 82 63 65 39 46 5 18
34000 95 81 99 88 96 88 85 81 63 65 39 46 5 18
32000 94 80 98 87 95 87 85 80 62 64 38 45 5 18
30000 93 79 97 86 94 86 83 79 61 63 38 45 5 18
28000 91 78 95 85 92 84 82 78 60 62 37 44 5 18
26000 89 76 93 83 90 83 80 77 59 61 37 43 5 17
24000 87 75 91 81 88 81 79 75 58 59 36 42 5 17
22000 85 73 89 79 86 79 76 73 56 58 35 41 5 16
20000 82 70 86 76 83 76 74 70 54 56 34 40 4 16
18000 79 68 83 74 80 73 71 68 53 54 32 38 4 15
16000 76 65 80 71 77 70 69 65 50 52 31 37 4 15
14000 73 62 76 67 74 67 65 62 48 49 30 35 4 14
12000 69 59 72 64 70 64 62 59 46 47 28 33 4 13
10000 65 55 68 60 66 60 58 56 43 44 27 31 3 13
Figures for shorter-season hybrids are in italics.  The actual Relative Maturities of short-and full-season hybrids vary with location and soil type.

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