With more rain moving through the Corn Belt today, there is increasing concern about soybean planting progress and even the need for some replanting. Iowa State University Extension offers some valuable resources for making these decisions, including the following table that breaks down the effect of planting date on yield in Iowa:
Interaction between planting date and maturity group on physiological maturity date, days from VE to R8, and relative yield for soybeans grown in Iowa, 1997
Planting dates | Maturity group | |||||||||||||||
| 2.2 | 2.5 | 2.9 | |||||||||||||
| Datea | Daysb | Relativec | Date | Days | Relative | Date | Days | Relative | |||||||
| Yield (%) | Yield (%) | Yield (%) | |||||||||||||
Late April | 9/30 | 137~ | 100 | 9/17 | 132 | 100 | 9/25 | 131 | 100 | |||||||
Mid-May | 10/3 | 134 | 96 | 9/21 | 118 | 91 | 9/25 | 126 | 88 | |||||||
Early June | 10/5 | 116 | 91 | 9/26 | 107 | 72 | 10/1 | 111 | 75 | |||||||
Late June | 10/14 | 108 | 67 | 10/2 | 99 | 61 | 10/6 | 103 | 54 | |||||||
Early/mid-July | 10/14 | 104 | 61 | 10/15 | 95 | 38 | 10/15 | 99 | 40 | |||||||
a Harvest date (month/day).
b Days between growth stages VE to R8.
c Relative yield = percent of potential yield for the average of six varieties.
