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Planting Date Effect on Soybean Reproductive Duration

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Objectives

  • Evaluate the effect of planting date on the number of days required to reach the R1 growth stage (beginning flowering) and days from R1 to R6 (full seed) growth stage among different soybean maturity groups.
  • Compare days to Growing Degree Unit (GDU) accumulation at reproductive stages of soybean growth among different planting dates.
Reproductive growth stage of a soybean plant.

Study Description

  • Six locations in southern Pennsylvania, including 1 double-crop location.
  • Each location had a different planting date, ranging from mid-April to early July and was evaluated twice per week from R1 to R6 soybean growth stage.
  • Results were divided into 2 maturity groups:
    Late II to Mid III
    Mid III to Mid IV

Results

  • Days required to reach R1 and R1 to R6 declined as planting was delayed for both soybean maturity groups (Table 1 and Table 2).
  • Variation among planting dates in GDU accumulation from planting to R1 was greater for later maturity varieties (219) than for earlier maturity varieties (102).
  • Planting date had an impact on the duration of reproductive growth (R1 to R6) and GDU accumulation during this time period. Duration and GDU accumulation both declined with later planting.
  • Results of this trial suggest that, although GDU accumulation from planting to R1 was relatively stable among planting dates, there is opportunity to increase the duration of reproductive growth from the R1 to R6 stage and capture more GDUs with earlier planting.

    Table 1. Duration and GDU accumulation of vegetative and reproductive growth for soybean maturity Late II to Mid III.

    Location Planting Date Days to R1 GDUs to R1 Days R1 to R6 GDUs R1 to R6
    1 4/15/15 50 768 52 1,198
    2 5/4/15 41 805 45 1,032
    3 5/9/15 40 821 38 859
    4 5/11/15 41 861 37 836
    5 6/11/15 34 851 28 836
    6 7/7/15 28 759 26 609
      Range 22 102 26 589

    Table 2. Duration and GDU accumulation of vegetative and reproductive growth for soybean maturity Mid III to Mid IV.

    Location Planting Date Days to R1 GDUs to R1 Days R1 to R6 GDUs R1 to R6
    1 4/15/15 53 822 53 1,249
    2 5/4/15 51 1,041 40 938
    3 5/9/15 46 1,027 41 893
    4 5/11/15 44 926 41 961
    5 6/11/15 39 974 30 757
    6 7/7/15 36 932 26 644
      Range 17 219 27 605


Authors:  Angela Parker, Kevin Fry, and Kirk Reese, Pioneer Agronomy Sciences

 

The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary.