1. Soybean Production and Management in Kentucky Jim Herbek Grain Crops Specialist University of Kentucky

2. SOYBEAN Growth Stages

3. ► How a Soybean Plant Develops, Special Report No. 53 ► Iowa State University Press ► $2.00  Extension Distribution Center 119 Printing and Publications Building Iowa State University Ames, Iowa 50011-3171 Telephone: (515) 294-5247 Fax: (515) 294-2945  http://www.extension.iastate.edu/Pages/hancock/agriculture/soybe an/bean_develop/ The information in the presentation comes from Iowa State Special Report No.53. This is an excellent resource for any producer or agronomist.

4. Vegetative Stages Reproductive Stages VE – emergence R1 – beginning bloom VC – cotyledon (unrolled unifoliolate leaves) R2 – full bloom V1 – first trifoliolate* R3 – beginning pod V2 – second trifoliolate R4 – full pod V3 – third trifoliolate R5 – beginning seed V(n) – nth trifoliolate R6 – full seed R7 – beginning maturity R8 – full maturity Soybean Growth Stages When staging a soybean field, each specific V or R stage is defined only when 50% or more of the plants in the field are in or beyond that stage. * A fully developed trifoliolate leaf node has unrolled leaflets.

5. Young Soybean Plant (Seedling)

6. Time Between Soybean Growth Stages ► Specific time between stages, number of leaves developed, and plant height may vary according to varieties/maturity groups, seasons, locations, planting dates, and planting patterns. ► An early-maturing variety may develop fewer leaves or progress through the stages at a faster rate. ► Late-maturing varieties may develop more leaves or progress through stages more slowly. ► Late planting dates will progress through stages at a faster rate.

7. Time Between Soybean Growth Stages (2) ► Rate of plant development is directly related to temperature. Length of time between stages will vary as temperature varies (both between and within growing seasons). ► Stressful conditions may lengthen the time between vegetative stages and shorten the time between reproductive stages. ► Soybeans at high populations grow taller; produce fewer branches, pods and seeds per plant; and set pods higher off the ground than soybean at low populations. ► Soybean has great compensation ability to adjust (branches, pods, seeds) to populations, injury and stress.

8. Development and timing of vegetative growth, flowering, pod development, and seed filling. Days of R Stages R Stage (node and leaf development)

9. Soybean Growth Habits ► In general, soybean has two types of growth habits. ► Indeterminate: characterized by a continuation of vegetative growth after flowering begins.  Lower V(n) prior to bloom (R1).  Flowers, pods and new leaves occur on plant at same time.  Most varieties in maturity groups 00 to IV. ► Determinate: characteristically finishes most of its vegetative growth before flowering begins.  Flowering occurs about the same time in top and bottom of plant. (pod and seed development are similar on same plant).  Higher V(n) prior to bloom (R1).  Terminal node has a long flowering raceme (stalk with pods).  Most varieties in maturity groups V to IX.

10. Due to photoperiod sensitivity, soybean varieties are adapted for growth in a relatively narrow latitude range. Areas Where Maturity Groups of Soybean are Grown Group 00 = earliest maturity Group IX = latest maturity Soybean varieties are classified into maturity groups (00 to IX) according to the range in latitudes in which they are adapted and are most productive. Regions of adaptability are long east to west but relatively short (100- 150 miles) north to south.

11. Soybean Vegetative (V) Stages ► Begins with seedling emergence and ends with last V(n) prior to beginning bloom (R1). ► VE = Emergence ► VC = Cotyledon (unrolled unifoliolate leaves) ► V1 – V(n) = Fully developed trifoliolate leaf node stages ► Except for VE and VC stages, all other vegetative stages are defined and numbered according to the uppermost fully developed trifoliolate leaf node. ► New V stages appear about every 5 days (from VC-V5) and every 3 days (from V5 to shortly after R5).

12. VEVE VE (Emergence) = Cotyledons above the soil surface. VE VC V1 Soybean seed begins germination by absorbing ~50% of its weight in water. Although soybean can germinate at minimum temperature of 50°F (or less), field emergence is more rapid (~7 days) and uniform if soil temperature is above 65°F.

13. “Poking through” hypocotyl

14. VC VC (Cotyledon) = Unifoliolate leaves unrolled sufficiently so the leaf edges are not touching. Nutrients and food reserves in the cotyledons supply the young plant during emergence and for about 7-10 days after VE (or until about the V1 stage). Unlike corn, where the growing point is protected beneath the soil for several weeks, the growing point of soybean moves above the soil surface at emergence. Thus, the plant is susceptible to damage (hail, frost, insects) or anything that cuts the plant off below the cotyledons (lowest axillary buds).

15. Determining Soybean Leaf Node Stages ► Following VC, the V stages are numbered according to the uppermost fully developed trifoliolate leaf node. ► Fully Developed Trifoliolate Leaf Node: A fully developed leaf node is one that has unrolled leaflets (i.e. the two edges of each leaflet have separated (unrolled) and the two edges are no longer touching). ► Start at the bottom of the plant and count upwards all nodes with fully developed trifoliolate leaves. ► The uppermost leaf node counted with a fully developed trifoliolate leaf is the V stage.  (i.e., 5 fully developed trifoliolate leaves = V5 stage)

16. Uppermost trifoliolate leaf with folded (rolled) leaflets (Leaflet edges touching each other). NOT a fully developed trifoliolate leaf node leaflet edges touching

17. Identification of the Uppermost Node with a Fully Developed Trifoliolate Leaf Uppermost node counted Uppermost node counted

18. V1 V1 = One fully developed trifoliolate leaf node. The two edges of each leaflet have unrolled and the two edges are not touching. V1

19. V2 V2 = Two fully developed trifoliolate leaf nodes 2 2 1 1 Rhizobia bacteria have infected roots and nodules become visible shortly after VE. N-fixation begins at V2 to V3 stages. Lateral roots are growing rapidly into the top 6 inches of soil.

20. Root Nodules (including a sliced nodule) Root showing nodules Active nodules have an internal pink color Nodules

21. V3 V3 = Three fully developed trifoliolate leaf nodes.

22. V4 V4 = Four fully developed trifoliolate leaf nodes. The upper junction between the main stem and a leaf petiole is called an axil. Each axil has an axillary bud. An axillary bud may develop into: 1) A flower cluster 2) A branch 3) Remain dormant The upper junction between the main stem and a leaf petiole is called an axil. Each axil has an axillary bud. An axillary bud may develop into: 1) A flower cluster 2) A branch 3) Remain dormant 2 2 4 4 3 3 1 1 Axillary Buds Stem Apex Axils of the unifoliolate and trifoliolate leaves and cotyledons all have axillary buds.

23. *The upper junction between the main stem and a leaf petiole is called an axil. In each axil there is an axillary bud. This bud usually develops a flower cluster, but may remain dormant, or may develop into a branch. Young Soybean Plant

24. V5V6 Apex (Growing Point) The total number of nodes that the plant may potentially produce is set at V5-V6. Branch

25. Stem Apex and Axillary Buds ► The axillary buds allow a tremendous capacity for the soybean plant to recover from damage (such as hail) and thin plant stands. ► The stem apex (tip growing point) exhibits dominance and supresses axillary bud development during vegetative growth. ► If the stem apex is damaged, axillary buds will produce many branches. ► The plant is killed if broken off below the cotyledonary node. No axillary buds occur below this node.

26. If the growing point is broken off during vegetative growth stages, the remaining axillary buds are allowed to branch so the plant can recover from damage or thin stands. During reproductive stages, the ability of the soybean plant to recover from damage is not as great. If the plant is broken off below the cotyledon node (lowest axillary buds), the plant will not recover. Young Soybean Plant Growing Point Trifoliolateleaf node Trifoliolateleaf (3 leaflets) Unifoliolateleaf No plant recovery Cotyledon Unifoliolatenode Petiole *Axillarybuds

27. What Vegetative (V) Stage is this Plant?

28. V6 V6 = Six fully developed trifoliolate leaf nodes. 2 2 4 4 6 6 5 5 1 1 3 3 New V stages are now appearing every 3-5 days. 50% leaf loss at V6 reduces yield ~3%. Unifoliolate leaves and cotyledons may have matured and fallen from the plant at this time. Root system expands at its fastest rate from V6 to R2

29. Determining Soybean V(n) Stage When Lowest Leaves are Missing ► Unifoliolate leaves (and lowest trifoliolate leaves) may be lost through injury or natural aging. ► The unifoliolate node produces unifoliolate leaves on directly opposite sides of the lower stem (on short petioles). ► The cotyledons (modified leaf storage organs) also are directly opposite on the stem just below the unifoliolate node. ► All other nodes produce true leaves that are trifoliolate leaves (on long petioles).  Produced singularly (from different nodes).  Alternate (from side to side) on the stem.

30. Trifoliolate leaf nodes: Trifoliolate leaves appear singularly (different nodes) and alternate (side to side) on the stem. Unifoliolate leaf node: Two unifoliolate leaves are directly opposite on lower stem. Cotyledonary node: Two cotyledons are directly opposite on the lower stem. When leaves fall off, a scar is left on the stem where the leaf petiole was attached. Leaf Node Locations

31. Identifying Soybean V(n) Nodes ► If lower leaves are lost, the V(n) stage can be determined by locating the position of the unifoliolate node. ► The two opposite leaf scars (slight indentations) on the lower stem (where the leaf petioles were attached) permanently mark where the unifoliolate leaves had grown. ► The unifoliolate leaf scars are located just above the two opposite scars that mark the cotyledonary node. ► Any leaf scars above the unifoliolate scars appears singularly and alternately on the stem, and mark node positions where trifoliolate leaves had grown.

32. Soybean Reproductive (R) Stages ► Begins with flowering and ends with full maturity. ► R1 - - - Beginning Bloom (flowering) ► R2 - - - Full Bloom ► R3 - - - Beginning Pod ► R4 - - - Full Pod ► R5 - - - Beginning Seed ► R6 - - - Full Seed ► R7 - - - Beginning Maturity ► R8 - - - Full Maturity

33. R1 – Beginning Bloom R1 = One open flower at any node on the main stem. Indeterminate varieties: At R1, plants are in the V7 to V10 stage. Flowering begins on the third to sixth node (depending on V stage at flowering) and progresses upward and downward. Vegetative growth continues after flowering begins. At R1, less than half of the nodes on the main stem have developed and plants have achieved less than half their final height. Determinate varieties: Vegetative growth is complete before flowering begins. Most or all of the nodes on the main stem have developed and plants grow very little in height after R1. Flowering occurs at the same time in the top and bottom of the plant. R1 and R2 may occur simultaneously. ******************* Soybean flowers are self- pollinated with less than 1% natural crossing. Pollination occurs at or just before flowers open. Flowers are purple or white (variety) Open Flower

34. PlantingSoybean Maturity Group DateMG IIMG IIIMG IVMG V Predicted First Flowering Date mean 1 SD 2 meanSDmeanSDmeanSD (±) 1-May3-Jun28-Jun417-Jun425-Jun5 15-May15-Jun221-Jun229-Jun38-Jul3 29-May27-Jun25-Jul112-Jul119-Jul2 12-Jun10-Jul116-Jul123-Jul129-Jul1 26-Jun24-Jul129-Jul12-Aug18-Aug1 1 Average of 29 years of weather data, Spindletop Farm, Lexington, KY. 2 Standard deviation: measurement of variation. Flowering dates generated from CROPGRO and verified from field data by Dr. Dennis Egli. AGR-184 --- Predicting Soybean First Flowering Date. Predicted first flowering date

35. AGR-184 --- Predicting Soybean First Flowering Date. Average of 29 years of weather data, Spindletop Farm, Lexington, KY. Standard deviation: measurement of variation, expressed by bars. Flowering dates generated from CROPGRO and verified from field data by Dr. Dennis Egli.

36. R2 – Full Bloom R2 = Open flower at one of the two uppermost nodes on the main stem with a fully developed trifoliolate leaf node. The rapid dry weight accumulation initially starts in the vegetative plant parts but then gradually shifts to the pods and seeds between R3 and R6. 50% defoliation at R2 reduces yield about 6 percent. R2 marks the beginning of a period of rapid and constant (linear) dry weight accumulation by the whole plant which continues until shortly after the R6 stage.

37. Axillary buds in stem axils develop into flower clusters called racemes. A raceme is a short stem-like structure that produces flowers that develop into pods. Determinate varieties generally have a longer raceme (flowering stalk) than indeterminate varieties. Raceme

38. R2 Well-nodulated plant Major lateral root growth is now vertical (downward). They (and the taproot) continue to elongate deep into the soil until late R6. Soybean roots can achieve depths of 5-6 feet by R6.

39. R3 – Beginning Pod R3 = Pod is 5 mm (3/16 inches) long at one of the four uppermost nodes on the main stem with a fully developed trifoliolate leaf node. About 60 to 75 percent of all flowers produced typically abort. ~ half of this abortion occurs before flowers develop into pods. Other half is due to young pod abortion. Stress causes higher abortion rates. pod 3/16 inch long

40. R4 – Full Pod R4 = Pod is 2 cm (¾ inches) long at one of the four uppermost nodes on the main stem with a fully developed trifoliolate leaf node. R4 is start of the most critical period for yield determination. From R4 through R6, stress (moisture, light, nutrients, frost, lodging, defoliation) reduces yield more than any other period. Yield reductions at R4 result mainly from fewer pods per plant. Stress can cause pods to abort. Period of rapid dry weight accumulation by the pods (R4 to middle of R5). ¾ inch long pod

41. Sequence of Young Pod Development R3 = Pod is 5 mm (3/16 inch) long. R4 = Pod is 2 cm (3/4 inch) long. R3 R4

42. R5 – Beginning Seed R5 = Seed is 3 mm (1/8 inches) long in the pod at one of the four uppermost nodes on the main stem with a fully developed trifoliolate leaf node. Seed yield depends on dry weigh accumulation (rate and length of time). Period of rapid seed growth. Between R5 and R6 dry weight accumulation redistributes to the developing seed. Stress at R5 will abort seeds. Yield loss in late R5 to R6 occurs mainly from fewer pods per plant and fewer seeds per pod. Also somewhat from smaller seed size.

43. R6 – Full Seed Dry weight accumulation still rapid in seeds, but begins to slow shortly after R6. R6 = Pod containing a green seed that fills the pod cavity at one of the four uppermost nodes on the main stem with a fully developed trifoliolate leaf node. “green bean” stage Stress reduces seed size (weight)

44. Sequence of Seed Development (R5 R6) R5 R6 R5 = Seed is 3 mm (1/8) long R6 = Green seed fills pod cavity

45. R7 – Beginning Maturity R7 = One normal pod on the main stem has reached its mature pod color (normally brown or tan). At R7, the plant is essentially at physiological maturity. No additional dry weight will accumulate in the seed. Physiological maturity occurs when the seed (and pod) turns yellow (lost all green color). Seed at physiological maturity is ~60 percent moisture. Stress at R7 essentially has no effect on yield.

46. R6R7R8 Sequence of Color and Size Changes of the Soybean Pod and Seed (R6 R8).

47. Soybean Pods and Seeds (R6 R8) (R8) (R7) (R6)

48. R8 – Full Maturity Five to ten days of drying weather are required after R8, before the seed contains less than 15 percent moisture. Ideal seed moisture content at harvest and for storage is 13 percent. Harvest can begin above 15 percent moisture: drying costs. seed damage if very high. Harvest delayed below 13 percent moisture: field shatter loss. harvest shatter loss. seed damage (split seeds). R8 = 95 percent of the pods have reached their mature pod color.

49. Components of Soybean Yield  Soybean yield is determined by 3 major components.  Number of pods per plant.  Number of seeds per pod.  Weight per seed (seed size).  Yield increases or decreases result from an increase or decrease in one or more of the yield components.  A reduction in one component may be compensated for by another component.

50. Soybean Yield Estimates  Estimates can be made. Reliability/variability depends on accuracy of estimating yield components.  The following publications provide information and guidelines for estimating soybean yield in the field prior to harvest.  Estimating Soybean Yields (AGR-188).  Kentucky Integrated Crop Management Manual for Field Crops. Section in “Soybean” manual (IPM-3).

51. Criteria for Estimating Soybean Yield  Variability in yield components will alter yield estimate reliability. Some assumptions are made.  More locations/samples; the better the estimate.  Best to estimate after seed fill is complete.  Estimate the following components:  Population (plants/acre).  Pods per plant.  Seeds per pod.  Seed size (seeds/lb).

52. The “Remarkable” Soybean (1)  Soybean has a great ability to adapt (+ or -) to it’s environment. Ability to compensate in both the vegetative and reproductive stages.  Important feature of the soybean.  Best ability of all major row crops. Vegetative Stages  Great capacity to compensate for reduced stand, plant loss, or stem and leaf damage. stand, plant loss, or stem and leaf damage.  Axillary buds at lower nodes produce branches (with new leaves). (with new leaves).

53. The “Remarkable” Soybean (2)  Ability of the soybean plant to recover from vegetative (foliar) injury is much less during reproductive stages (particularly late R stages).  However, the soybean has the ability to adjust it’s reproductive components (flowers, pods, seed #, seed size) in response to environmental conditions (stress or no stress).  Increases or decreases in one or more of the yield components will affect yield (+ or -). Reproductive Stages

54. The “Remarkable” Soybean (3)  Stressful conditions will abort flowers, pods, seeds and decrease seed size.  A reduction in one yield component may be compensated for by another component.  Which yield component decreases (stress) or increases (good conditions) depends on the R stage when stress/non-stress occurs.  A short period of stress allows the next R stage to compensate as conditions improve.

55. The “Remarkable” Soybean (4)  An extended period of stress decreases the opportunity for R stage components to compensate each other.  As the soybean plant progresses from R1 to R6, it’s ability to compensate after a stress decreases.  At later R stages, potential yield loss from stress increases.  Stress from R4 to R6 reduces yield more than stress at other R stages.

56. Vegetative Flowering Soybean Compensation Ability by Growth Stage Vegetative Flowering Podding No. of Seeds Seed Size  Optimum stand branching ability reduced  Reduced stand increased branching  Plant damage increased branching  No stress maintain more flowers  Stress more flowers abort

57. Flower and Pod Trivia  About 60 to 75 percent of all soybean flowers produced abort and don’t contribute to yield.  About half (30-40%) of this abortion occurs before flowers develop into young pods.  The other half (30-40%) is due to pod abortion.  If soybean maintained all its flowers, yield potential would be 250 bu/acre.  Present soybean plant not capable.  Overproduction of flowers and pods is good. Allows flexibility for early stress periods.

58. Seed Number Seed Fill (weight)  No stress increase seed size (weight)  Stress decrease seed size (weight) Podding  No stress more seeds develop  Stress seeds do not develop or seeds abort  No stress maintain more pods  Stress more pods abort

60. Soybean Populations

61. U.K. Recommended Seeding Rates  Higher than needed for most situations.  Contain a seeding rate range for each row width.  Recommendations are “buffer” seeding rates.  Insurance in the event of poor emergence, stand loss, etc.  Growers are not accepting lower seeding rates.  Soybean seed costs:  Relatively low seed costs 10-20 years ago.  Comparatively higher seed costs today with technology trait soybeans (i.e. RR).

62. U.K. Recommended Seeding Rates Row Width (inches) Seeding Rate Expected* plants/acre Seeds/footSeeds/acre 7 2 to 3 149,000 to 224,000 119,000 to 179,000 15 5 to 6 174,000 to 209,000 139,000 to 167,000 30 8 to 10 139,000 to 174,000 111,000 to 139,000 *Assuming 80% emergence of planted seed. AGR-130 --- Soybean Production in Kentucky (Part III).

63.  Seeding Rate Final Population (Plants)  What can we expect?  Average % emergence = 80-85%  Range = 70% or less to 95%  Factors influencing final stand achieved.  Seed quality (germination and vigor).  Seedbed conditions (tillage, residue).  Planting environment (soil temp. & moisture).  Weather after planting (crusting, moisture).  Planting equipment (depth, seed coverage).  Post-emergence (hail, pests, chemicals).

64. Seeding Rate Basics  Base seeding rate on number/unit area (seeds/acre); not volume/area (pounds/acre).  Reason: Seed size will vary.  Variety (genetics).  Environment: Affected by growing season (weather during seed-fill).  Seed size can vary from:  2500 seeds/lb or less (large seed)  3500 seeds/lb or more (small seed)

65. Seed Size / Seeding Rate Example  Fifty pound bag of seed contains:  Small seed (3500 seeds/lb) = 175,000 seeds  Large seed (2500 seeds/lb) = 125,000 seeds difference = 50,000 seeds/bag  Seeding rate of 60 pounds/acre:  Small (3500 seeds/lb) = 210,000 seeds/A  Large (2500 seeds/lb) = 150,000 seeds/A difference = 60,000 seeds/A

66. How Seed Size Affects Seeding Rate No. of Seeds in a 50 lb. Bag Lbs. of Seed Required at: Seed Size (seeds/lb) 180,000 Seeds/acre 120,000 Seeds/acre 200025002800300035004000100,000125,000140,000150,000175,000200,000907264605145604843403430

67. Soybean Plant Populations  Studies: Yields do not vary greatly within a wide range (100,000 – 220,000 plants/A).  South: < 100,000 plants/A have equal yields.  A common goal is 150,000 plants/A.  Seeding rates of 175,000-200,000 seeds/A.  Most producers overseed than underseed.  Considerations?:  Variety (maturity group)  Planting date

68.  Question:  Why can soybeans produce equivalent yields at a wide range of plant populations?  Answer:  Soybeans have a tremendous ability to compensate (branching, pod number, seed number).  High populations: plants do not sense a need to branch.  Low populations: plants branch to fill in space.

69. *The upper junction between the main stem and a leaf petiole is called an axil. In each axil there is an axillary bud. This bud usually develops a flower cluster, but may remain dormant, or may develop into a branch. Young Soybean Plant

70. 17,400 34,800 70,000 121,800 192,000 Seeding Rates: Live Seeds per Acre Spindletop Farm, Lexington, KY 15-inch rows 2 planting dates (full season and double crop) Three yrs (2003, 2004, 2005) No-Till (2003, 2004) Reduced Till (2005) Glyphosate herbicide for weed control Live stand counts were taken prior to harvest. Study conducted by Chad Lee, Dennis Tekrony, and Dennis Egli (Univ. of Kentucky).

72. Minimum plant densities required for optimum yield Seeding Date 1 CultivarMaturity Minimum Plant Population 2 plants/acre 24 April 03 FSStressland4.542,500 FS CF 461 4.653,400 24 April 03 FS CF 492 4.949,800 21 May 04 FSB2832.892,300 FSB3363.372,100 FSCF4614.685,800 21 June 04 DCB2832.891,400 DCB3363.393,100 1 FS = full season; DC = double crop. 2 Exponential rise to maximum, 3 parameter model: density required for 95% of yield that was achieved at maximum plant density. Lexington, KY, 2003 and 2004

73. Table 2. Minimum plant densities required for optimum yield as defined by two regression equations. Linear- Plateau 2 Exponential 3 Seeding Date 1 CultivarMaturity Minimum Plant Population plants/acre 24 April 03 FSStressland4.542,10042,500 FS CF 461 4.642,90053,400 24 April 03 FS CF 492 4.939,70049,800 21 May 04 FSB2832.866,80092,300 FSB3363.347,80072,100 FSCF4614.649,80085,800 21 June 04 DCB2832.879,80091,400 DCB3363.369,90093,100 1 FS = full season; DC = double crop 2 Linear-plateau model: Minimum plant density required for maximum yield. 3 Exponential rise to maximum, 3 parameter model: Density required for 95% of yield that was achieved at maximum plant density.

74. Soybean Population Summary (Lexington, KY ---- 2003 & 2004)  Maximum yield was obtained at populations between 42,000 and 93,000 plants/acre (more conservative exponential regression model) or between 40,000 and 80,000 plants/acre (linear plateau model).  Maximum yield obtained with <100,000 plants/acre (in all situations).  Early maturities (MG II and early MG III) and later planting dates (after June 1) may need slightly higher populations (70,000 to 90,000 plants/acre).

75. Soybean Population Study- - (2005) (Earlier Variety (3.9 RM) --- Early Planting Date) Seeding Rate (viable seeds/A) Avg. Final Stand (Plants/A) Soybean Yield (Bushels/A) 50,00044,000 70 a 75,00061,000 100,00081,000 72 a 125,000101,000 71 a 150,000117,000 73 a 175,000142,000 200,000168,000 71 a 225,000184,000 70 a  Location: UKREC (Princeton, Ky)  Variety = Pioneer 93M90  Planted May 25, 2005. Row spacing = 15 inches.

76. Soybean Population Study- - (2005) (Later Variety (4.7 RM) --- Early Planting Date) Seeding Rate (viable seeds/A) Avg. Final Stand (Plants/A) Soybean Yield (Bushels/A) 50,00045,000 72 a 75,00068,000 74 a 100,00092,000 76 a 125,000119,000 73 a 150,000145,000 175,000162,000 75 a 200,000183,000 76 a 225,000210,000 74 a  Location: UKREC (Princeton, Ky)  Variety = Pioneer 94M70  Planted May 25, 2005. Row spacing = 15 inches.

77. Soybean Population Study - - 2005 (Avg. of 2 Varieties --- Early Planting Date) Seeding Rate (viable seeds/A) Avg. Final Stand* (Plants/A) Soybean Yield** (Bushels/A) 50,00045,000 73 a 75,00065,000 72 a 100,00085,000 75 a 125,000110,000 73 a 150,000130,000 74 a 175,000150,000 200,000175,000 225,000195,000 72 a *Avg. approx. final stand of two varieties. **Avg. of two varieties (3.9 RM and 4.7 RM). Varieties were not significantly different.  Planted May 25, 2005. Row spacing = 15 inches. Location = UKREC.

78. Soybean Population Summary (Princeton, KY ---- 2005)  Statistically, equivalent soybean yield was obtained at populations ranging from 45,000 to 200,000 plants/acre.  The lowest population of 45,000 plants/acre was sufficient to obtain maximum yield.  Occurred for both soybean varieties/maturities (3.9 RM and 4.7 RM).

79. Lower Soybean Populations: (+ and -)  Benefits  No yield loss  Lower seed costs  Less lodging  Possible negatives  More difficult to harvest?  Large, low branching  Low pod height  Go slow; go low More Weed pressure?  More Weed pressure?

80.  Maximum Soybean Yields can be achieved at  Lower Soybean Populations as a result of  Lower Seeding Rates which result in  Lower Seed Costs  particularly true for soybean seed that has higher costs associated with technology traits (i.e. RR).

81. SeedingRate(Seeds/A) No. of ** No. of ** 50 lb. Bags/A Seed*** Seed***Cost($/Acre)SeedSavings($/Acre) 175,000* 175,000*1.25$37.50 150,0001.10$33.00$4.50 125,0000.90$27.00$10.50 100,0000.70$21.00$16.50 75,0000.55$16.50$21.00 Soybean Seeding Rates and Seed Costs *Average seeding rate being used (based on yield contest entries). **Based on seed size of 2800 seeds per pound. ***Based on average seed cost (RR seed) of $30 per 50 lb. bag.

82. Soybean Population Conclusions (1)  Appears that populations for Full- Season soybeans can be lowered (from present populations commonly being used) and still obtain maximum yields.  Results in reduced seeding rates and lower seed costs/acre.  How low can we go?:120,000 --- 100,000 80,000 --- 50,000??  More research needed to more clearly define population/yield response parameters.

83. Soybean Population Conclusions (2)  Comparatively higher populations may likely be needed for:  Late plantings (D.C. soybeans).  Early maturity varieties?  More research needed to clarify.  Different environments may alter soybean population/yield response.  Growing season (weather).  Stress or non-stress.

84. Soybean Variety Selection

85. Soybean Variety Selection Criteria (1) Yield potential Multi-location and multi-year tests. Standability (lodging). Pest resistance. Diseases (SCN, foliar, others). Insects? (future development). Technology (GMO) traits. Herbicide tolerance (RR trait). Future pest traits? (insects, diseases) Future food/health traits.

86. Soybean Variety Selection Criteria (2) Shattering. Great improvements, Mat. Group differences. Markets (price; premiums). Commodity soybean (oil and meal). Specialty soybeans (specific uses/traits). (AGR-180) Non-GMO. Management reasons. Soils, harvest mgt., cropping system, planting date. Maturity Group(s)

87. Which Maturity Group(s) is Best to Use?

88. Due to photoperiod sensitivity, soybean varieties are adapted for growth in a relatively narrow latitude range. Areas Where Maturity Groups of Soybean are Grown Group 00 = earliest maturity Group IX = latest maturity Soybean varieties are classified into maturity groups (00 to IX) according to the range in latitudes in which they are adapted and are most productive. Regions of adaptability are long east to west but relatively short (100- 150 miles) north to south.

89. Yields by Maturity Group MG200320042005Avg. ------------ Bu/A ------------ II40.731.330.934.4 III46.439.935.840.9 IV51.745.938.845.4 V40.237.143.440.3 LSD (0.05)5.03.75.7 Field: Spindletop Farm, Lexington, KY (Chad Lee) Tillage: No-Till 2003 & 2004 = Adequate moisture throughout season. 2005 = Dry early (M,J.J); some rain in August; dry late.

90. Maturity Group Study Results Based on data for three years (2003-05) –MG IV was highest yielding –MG III and MG V were about 10% less –MG II was about 20% less Results

91. KY Soybean Variety Trials 200320042005 Bu/A III56.766.847.5 IV61.868.755.8 V59.759.959.0 Average yield of maturity groups across 5 locations. 200320042005 % Difference III- 8- 3- 15 IV000 V- 3- 13+ 6