SOYBEAN GROWTH & DEVELOPMENT

Transcription

1 SOYBEAN GROWTH & DEVELOPMENT Keith Glewen, Nebraska Extension Educator 1

2 Soybean Growth Stages SOYBEAN GROWTH STAGES VEGETATIVE VE - Emergence VC - Unfoliolate V1-1st Trifoliolate V2-2nd Trifoliolate V3-3rd Trifoliolate V4-4th Trifoliolate V5-5th Trifoliolate Vn - nth Trifoliolate REPRODUCTIVE R1 - Begin R2 - Full R3 - Begin R4 - Full R5 - Begin R6 - Full R7 - Begin R8 - Full Bloom Pod Seed Maturity 2

3 Soybean Germination Hypocotyl pulls the cotyledons (seed leaves) out of the soil 3

4 VE Emergence: cotyledons and growing point are above the soil surface Cotyledons 7-10 day food supply following VE 4

5 VC Cotyledons and Unifoliates are fully expanded VC Cotyledons and Unifoliates are Fully Expanded 5

6 Soil Crusting V1 First Trifoliate 6

7 V2 Second Trifoliate V2 Active N 2 Fixation 7

8 V5 Fifth Trifoliate 8

9 V5 Fifth Trifoliate # of nodes initiated on main stem 9

10 R1: Beginning Bloom R2: Full Bloom 10

11 R3: Beginning Pod R3: Beginning Pod 11

12 R4: Full Pod R8: Full Maturity 12

13 Yield Effects of Weed Removal by Row Width Earlier Planting - Beneficial Impacts An earlier canopy closure, which: Allows the crop to capture more of the early season available solar radiation and more of the early season available water. Mitigates the evaporative loss of soil water thereby allowing more of the seasonally available water to be used for crop transpiration. An earlier V1 stage, which: Allows for an earlier seasonal start of the linear 3.7-day stem node accrual rate, leading to more final main stem nodes. Allows for an earlier occurrence of floral induction, which in turn leads to an earlier R1 flowering date lengthens seed-filling. Greater seed yield, because of: A 1/4 to 5/8 bu/ac increase in yield per day for each day the planting date is moved closer to 1 May, with the actual yield amount depending upon how favorable the given year is for soybean production. 13

14 5/9/2018 Earlier Planting Other Considerations Shown here by skin tone shading is the amount of solar radiation that would be potentially available for capture by a crop canopy after 1 May. Seasonal Change in Day Length (Lincoln, NE - Latitude: 40.82) 1-Jan 16-Jan 31-Jan 15-Feb 2-Mar 17-Mar 1-Apr 16-Apr 1-May 16-May 31-May 15-Jun 30-Jun 15-Jul 30-Jul 14-Aug 29-Aug 13-Sep 28-Sep 13-Oct 28-Oct 12-Nov 27-Nov 12-Dec 27-Dec 15:00 15:00 14:00 14:00 13:00 Day :00 12:00 11:00 11:00 10:00 10:00 19-Sep 9:00 1-Oct 12:00 26_Apr 3-May 8:00 9:00 8: Early emergent soybean seedlings attract emerging over-wintered bean leaf beetles. BLB feeding injury itself is usually not a problem per se, but BLBs do transmit bean pod mottle virus, and an early BPMV infection can greatly reduce the yield potential (aside from the green stems you get at harvest). You may want to consider treating your early planted seed with a systemic insecticide seed treatment. You do NOT have to wait for 50 F soil temperatures to plant soybeans. Genetics and dealer seed conditioning has made today s soybean seed quite cold-tolerant. Actually, the main problem in early soybean plantings is a much too wet soil. Cool rainy periods can create conditions very favorable for infection by soil pathogens. You may want to consider treating your early planted seed with a fungicide. To take advantage of the higher yield potential that comes with earlier planting dates, soybean planting may have to begin before you finish corn planting. If so, you will need to consider the amortized and annual costs of running a 2nd planter for soybean. But at least you now know the penalty for allowing corn planting to delay your soybean planting. Day Length (h:m) Day of Year The red, blue, green, and brown vertical lines denote planting dates of 1 May, 16 May, 31 May, 15 June, respectively. The light blue and dark blue triangles denote the zero and 20% probability of a later spring, or earlier fall, frost. 14

15 Soybean Seed Yield Response to Seed Depth & Seeding Rate Key Results: Seed depths of <1.25 were too shallow and depths of >2.25 were not yield optimal. -The optimal seed depth seems to be about Seeding rates of 35K or 70K seeds/acre (2 or 4 seeds/ft in a 30 row spacing) were not yield optimal. -The optimal seed rate seems to be between 105K and 140K seeds/acre (6 or 8 seeds/foot of row in 30 rows). Colder daytime soil & soil surface air temperatures in heavy-residue No-Till fields will delay germination, emergence, the attainment of stage V1 (thus delaying the start of main stem node accrual), lessen leaf area at those lower nodes and shorten their internodes. 15

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17 Hail Impact on Soybean Yield Yield loss associated with soybean leaf defoliation based on soybean growth stage 17

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