Risk vs. Reward: Can We Resolve Row Spacing and Seeding Rate Questions in Soybean?

Risk vs. Reward: Can We Resolve Row Spacing and Seeding Rate Questions in Soybean? Shawn P. Conley Soybean and Wheat Specialist University of Wisconsin, Madison Today s Soybean Production Systems are Dynamic Changes in row spacing Growers have dropped small grains from their rotation Row units vs drills Accurate seeding rate Uniform planting depth and emergence Changes in seeding rates RR seed cost - 2007 List price $30.99 to 33.99 vs. farm gate $23.50 to 26.50 Changes in planting date and environment

What Row Spacing Growers are Using What row spacing are growers planting? Row spacing Seeding rate Purdue rec s (90*90) % respondents 21 in. 155,000 129,000 12% 11 x 20 180,000 160,000 31% 10 in. 198,000 196,000 57% 52% of Indiana growers with 1000+ acres are planting their soybeans in 15 inch rows Conley Conley and Santini, and Santini, 2007; 2007 CM IN and IL Row Spacing Changes 100% Percent of Growers 80% 60% 40% 20% IN 2003 IN 2007 IL 2003 IL 2007 0% < 10 11 to 18 19 to 29 30 + Row spacing N = 180

Row Spacing Affect on Grain Yield (A) Soybean, Narrow vs. Wide Row Widths Optimum Seeding Date, Full Seaon Varieties 20 15 Yield Difference (%) 10 5 0-5 1-LA 2-KS 3-IL 4-NE 5-NE 6-NE 7-NE 8-IA 9-ON 10-MI 11-MI 12-MI 13-WI 14-WI 15-WI 16-MN Location Source: C. Lee, CM, 2006. http://www.plantmanagementnetwork.org/sub/cm/review/2006/wide/ Row Spacing Affect on Grain Yield (B) Soybean, Narrow vs. Wide Row Widths Late Seeding Date, Full and Short Seaon Varieties 100 80 Yield Difference (%) 60 40 20 0-20 1-AR 2-AR 3-LA 4-KS 5-WI Location Source: C. Lee, CM, 2006. http://www.plantmanagementnetwork.org/sub/cm/review/2006/wide/

IN Row Spacing Affect on Grain Yield Grain yield (bu a -1 ) 70 65 60 55 50 45 40 35 30 Narrow vs. wide 9.3% difference *Planting date did not affect row spacing response 7.5 15 30 63.6 62.8 A A 58.1 A 54.3 52.7 B B 50 48.7 47.9 A 46.6 A A A 43.1 B 38.9 A 35.5 B Butlerville, IN Columbia City, IN Farmland, IN Lafayette, IN Wanatah, IN Conley et al. 2007 IN Row Spacing Affect on Grain Yield Row spacing Butlerville, IN Farmland, IN Columbia City, IN 2005 2006 2005 2006 2005 2006 ----------------------------Grain yield (bu a -1 )---------------------------- 7.5 70.2 a 44.2 a 69.3 a 48.3 a 35.8 a 48.2 a 15 70.5 a 43.8 a 66.3 a 47.4 a 36.9 a 45.6 a 30 65.6 b 36.5 b 56.8 b 41.9 b 36.8 a 48.2 a Means followed by the same letter within a column are not different (p < 0.05) Narrow vs. wide 9.2% difference Hanna et al. 2007

Row Spacing Affect on Grain Yield 70 De Witt, Nevada, and Whiting, IA 2004-06 15 vs. 30 inch 6.7% difference Grain yield (bu a -1 ) 65 60 55 50 45 40 35 A B 30 15 30 Source: P. Pedersen, 2007 Does Row Spacing Impact My Decision to Reduce My Soybean Seeding Rate Soybean Yield Response to Row Spacing and Plant Population 12 Environments in 1999-2000 50 10" Rows 20" Rows 49 30" Rows Yield (Bu / A) 48 47 46 45 44 43 Source: Seth Naeve, Univ. Minn. 100,000 175,000 250,000 Plant Population (seeding rate)

Reasons for Differential Row Spacing Yield Response Light interception and canopy development Affected by planting date and population Plant height and photosynthetically-active radiance Water availability In irrigated systems or when rainfall is sufficient narrow rows generally out-yield wide rows Source: C. Lee, CM, 2006. http://www.plantmanagementnetwork.org/sub/cm/review/2006/wide/ Weed Management Issues in Wider Rows Weed control implications Weeds are the #1 IN soybean pest (Conley and Santini, 2007 CM) Glyphosate resistance is a reality Delayed canopy closure as row spacing increases Row Spacing 7.5 15 30 ----------May planting date ---------- < 5/5 5/6 to 5/15 5/16 to 5/25 35 30 25 50 45 40 75 70 65 Source: Purdue Extension publication ID-179, Corn & Soybean Field Guide

Soybean Yield Loss Influenced by the Timing of Weed Removal and Row Spacing Yield Loss (% weed free) 40 35 30 25 20 15 10 5 0 V1 V2 V3 V4 V5 V6 V7 R1 R2 R3 Timing of weed removal (Soybean growth stage) 7.5" 15" 30" Source: Knezevic et al. 2003. Weed Management in GR Soybean 26% of respondents indicated that they applied a preemergence herbicide to their soybean crop. 23% of growers indicated that they utilized a one pass weed control program. The percentage of growers utilizing a one trip weed control programs was 40% (99 or less), 34% (100 to 249), 20% (250 to 499), 13% (500 to 999), and 11% (1000+). One pass program produced a 5.8% yield loss compared to those growers with 2+ passes. Source: Johnson Johnson et al. et 2007. al. 2007 CM.

Does Row Spacing Effect Spray Coverage? Our studies showed no difference in spray penetration or total coverage between soybean planted in 7.5-, 15-, or 30-inch rows across locations and years We recommend that growers base their soybean row spacing decisions on other factors, such as yield potential, equipment availability, or weed control Hanna et al. 2007 Do Wheel Tracks Affect Yield? Sprayer wheel traffic from first flower (growth stage R1) through harvest can damage soybean plants and reduce yield if soybean stands are thin (<100,000 plants per acre) or late planted Regardless of stand, plants could not compensate for wheel tracks made at R3 (early pod development) or R5 (early seed Yield loss per acre is based on boom width Hanna et al. 2007

Break Even Yield Break Even Yield Required (bu a -1 ) 6 5 4 3 2 1 0 NWT 60' 90' 120' $5.00 $6.00 $7.00 $8.00 $9.00 $10.00 Soybean Price 60: 2.5% 90: 1.9% 120: 1.3% Fungicide + adjuvant + application = $21.00 (50 bushel beans) Hanna et al., 2007 Summary Row Spacing Yield response of narrow vs. wide rows in soybean is variable (0-18%) Variability is water and light interception driven (Average yield loss: 7%) Increased risk of yield loss due to weed competition Row spacing does not affect canopy penetration of foliar fungicides Wheel tracks from ground driven sprayers decrease grain yield in 7.5 and 15 inch row spacings when applied at R3 and R5 soybean

Common Grower Questions Related to Reduced Soybean Seeding Rate Systems What is the minimum I can plant and still achieve 100% yield potential? Should I select and plant a bush over an erect stem soybean variety? Real or marketing/grower perception? What about maturity group response? Should I adjust my seeding rate based on maturity group adaptiveness? Current State Soybean Seeding Rec s State Illinois Iowa-seeds Kentucky-plants Michigan-seeds Missouri-seeds Ohio-seeds Indiana-seeds Wisconsin Germination -----Recommended Seeding Rates ----- 30 15 7.5 -----------Seeds or plants acre -1 ----------- - - - 90% 125 to 140 125 to 140 200* 80% 111 to 139 139 to 167 119 to 179 90% 122 to 157 139 to 174 175 to 280 90% 140,000 175,000 200,000 90*90% 129,000 160,000 196,000 90*90% 129,000 160,000 196,000 - - - *Old versus new

Maturity Group and Stem Phenotype Response to Decreased Soybean Populations Northern: 2.8 and 3.6 M.G Southern: 3.6 and 4.2 Plant populations 50,000 to 250,000 Erect vs. bushy beans 8 site years; 4 varieties Drilled soybean (7.5 ) Population Affect on Seed Mass Population affected seed mass at all N. locations 34 32 R 2 = 0.99 PPAC 2005 Population did not affect seed mass at S. locations Seed mass was greater in early MG soybean varieties than full season Seed Mass (g 200-1 seeds) 30 28 26 24 gliu AG2801 22 D3640CR AG3602 2702-4 20 0 100 200 300 400 500 600 700 Seeding rate (1000 seeds ha -1 )

2005-2006 Population Affect on Pod Number Plant -1 Seeding rate ACRE NEPAC PPAC SEPAC 50,000 81 a 55 a 109 a 75 a 100,000 45 b 35 b 66 b 55 a,b 150,000 39 b 25 c 43 c 44 b 200,000 37 b 22 c 35 d 43 b 250,000 36 b 21 c 30 d 38 b Means within the same column and followed by the same letter are not considered different p < 0.05 Population Affect on Oil Content (ACRE 05-06) 20 19 R 2 = 0.99 AG2801 D3640CR AG3602 2702-4 Oil (%) 18 17 gliu 16 0 100 200 300 400 500 600 700 Seeding rate (1000 seeds ha -1 )

Population Affect on Seed Protein (ACRE 06) 39 R 2 = 0.98 38 Protein (%) 37 36 AG2801 D3640CR AG3602 2702-4 35 gliu 34 0 100 200 300 400 500 600 700 Seeding rate (1000 seeds ha -1 ) Summary Oil and Protein Content Oil content as not affected by population Oil content was affected by variety at ACRE Protein content varied among years, varieties, and locations In general protein content increased as population increased

Population Affect on Grain Yield (ACRE 05-06) 5000 4800 R 2 = 0.90 4600 Yield (kg ha -1 ) 4400 4200 4000 3800 3600 3400 Seeding rate (1000 seeds ha -1 ) AG2801 gliu D3640CR AG3602 2704-2 3200 0 100 200 300 400 500 600 700 Population Affect on Grain Yield (NEPAC 05-06) 4500 4000 R 2 = 0.88 AG2801 D3640CR AG3602 2702-4 Yield (kg ha -1 ) 3500 3000 2500 gliu 2000 0 100 200 300 400 500 600 700 Seeding rate (1000 seeds ha -1 )

Population Affect on Grain Yield (PPAC 05-06) 5000 4800 R 2 = 0.96 4600 4400 Yield (kg ha -1 ) 4200 4000 3800 3600 3400 3200 Seeding rate (1000 seeds ha -1 ) AG2801 gliu D3640CR AG3602 2702-4 3000 0 100 200 300 400 500 600 700 Population Affect on Grain Yield (SEPAC 05-06) 5200 5000 R 2 = 0.85 4800 Yield (kg ha -1 ) 4600 4400 4200 4000 3800 3600 Seeding rate (1000 seeds ha -1 ) AG2801 gliu D3640CR 434NRR 3832-4 3400 0 100 200 300 400 500 600 700

Summary Plant Populations Stem architecture (bushy vs. erect) did not affect soybean grain yield Soybean oil content was relatively stable among locations, varieties, and years Soybean protein content was variable Optimal seeding range was 100,000 to 150,000 plants a -1 Planting Date and Environment Impact on Row Spacing x Seeding Rate Interactions

Planting Date Shift Over the Last Decade How has your average soybean planting date changed from 10 years ago? (1253 respondents) Planting date shift One week earlier Two weeks earlier Three weeks earlier Later by one week Other No change Percent of growers 28% 32% 7% 3% 3% 27% Conley and Santini, 2007; CM What is Driving this Shift? Rank the importance of the following factors for that have influenced your planting date? (1 to 5) Reason for shift Yield increase Weather changes Improved soybean varieties Seed applied technology advances Spread out work load Industry re-plant programs Importance 1.9 2.0 2.1 2.5 2.8 3.5 Conley and Santini, 2007; CM

Location by Planting Date Affect on Soybean Yield Grain Yield (bu a -1 ) 70 65 60 55 50 45 40 35 *Row spacing yield was similar across all planting dates 61.7 54.7 59.8 58.3 46.5 45.2 58.9 67.4 67 64.7 49.2 47 47.2 47.4 63.5 62.3 61.1 50.4 49.5 45.7 41.5 51.5 44.7 43.6 0 15 30 45 60 75 90 105 Days Past 4/1/07 Butlerville Farmland Lafayette 45.1 35.8 Columbia City Wanatah 37.4 Variety by Planting Date Affect on Soybean Yield Planting Date Impact on Yield - Field Trial 2006, 2007, West Lafayette, IN 70 Yield (bu/acre) 65 60 55 MG 2.8 2006 MG 2.8 2007 MG 3.2 2006 MG 3.2 2007 MG 3.7 2006 MG 3.7 2007 50 45 20-Mar 3-Apr 17-Apr 1-May 15-May 29-May 12-Jun Planting Date Robinson et al. 2007

Changes in Soybean Flowering Characteristics, Node Number, and Grain Composition Early planted, early maturity group soybean cultivars are producing flowers in May Increased node number Number of Reproductive Nodes per Plant Planting Date Influence on Reproductive Node Number 16.0 15.0 R 2 = 0.84 15.0 14.6 13.8 14.0 12.9 13.0 12.4 12.0 11.3 11.0 10.0 9.0 8.0 3/30/2006 4/13/2006 4/27/2006 5/10/2006 5/30/2006 6/6/2006 Planting Date Modified grain composition 19.5 19.0 Soybean Grain Percent Oil Influenced by Planting Date Decreased seed size Percent Oil 18.5 18.0 Series1 MG 2.6 Series2 MG 3.2 Series3 MG 3.8 17.5 Robinson et al. 2006 17.0 3/24/06 4/3/06 4/13/06 4/23/06 5/3/06 5/13/06 5/23/06 6/2/06 6/12/06 Planting Date Does Planting Date Impact My Decision to Reduce My Soybean Seeding Rate Population effects on soybean yield across planting dates 1.0 Relative Yield (yield / max. yield) 0.9 0.8 0.7 100K seeds / acre 250K seeds / acre Source: Seth Naeve, Univ. Minn. 0.6 20 30 40 50 60 70 80 Days after 1 April 1 May 1 June

Defining Planting Date Responses in N. Illinois* 2001-2003 University of Illinois Source: E. Nafziger University of Illinois Seed rate 000/acre 75 125 175 225 Planting date Early April Late April Early May Late May -------------------- bushel/acre -------------------- 38.7 45.8 46.6 43.5 41.9 48.3 47.6 46.5 43.8 48.7 48.3 46.5 45.3 48.9 48.9 46.6 *Soybean yield averaged over nine environments in Northern Illinois. Seeding rates are expressed as viable seeds per acre. Defining Planting Date Responses in S. Illinois* 2001-2003 University of Illinois Source: E. Nafziger University of Illinois Seed rate 000/acre 75 125 175 225 Planting date Mid-April Early May Late May Early June -------------------- bushel/acre -------------------- 30.4 33.7 35.9 30.6 29.3 33.7 35.3 32.8 32.3 34.6 36.3 32.4 32.9 35.4 34.6 33.7 *Soybean yield averaged over four environments in Southern Illinois. Seeding rates are expressed as viable seeds per acre.

Defining Planting Date Responses in Illinois In Northern Illinois.Planting in early April reduced yield by about 10 percent, and planting in late May reduced yield by about 5 percent; these results suggest that planting too early tends to reduce yield more than planting late. It pays to wait to plant, but if planting is earlier than ideal, it pays to add extra seed. Source: E. Nafziger University of Illinois Defining Planting Date Responses in Illinois 2001-2003 University of Illinois CMRA Project In Northern Illinois.Optimum planting rates for planting in the optimum window were about 150,000 to 160,000 viable seeds per acre, but this rose to above 200,000 per acre if planting was earlier than the optimum time. Still it appears that planting rate should be between 150,000 to 175,000 viable seeds per acre in Southern Illinois. Source: E. Nafziger University of Illinois

Should Yield Environment Affect Seeding Rate Bu/Ac 70 60 50 40 30 20 10 0 Yield 167 159 Harvest Pop 138 116 106 High Yield Environment 70 250 220 190 160 130 100 Seeding Rate (1000 s) Source: J. Beuerlein, Ohio State Economic Analysis for a High Yield Field $ 350 300 250 200 150 100 50 0 Source: J. Beuerlein, Ohio State $ of Yield Profit Max Seed Cost ($) 250 220 190 160 130 100 Seeding Rate (1000 s)

Should Yield Environment Affect Seeding Rate Bu/Ac 60 50 40 30 20 10 0 225 204 175 Moderate Yield Environment Yield 150 Harvest Pop 108 78 250 220 190 160 130 100 Seeding Rate (1000 s) Source: J. Beuerlein, Ohio State Economic Analysis for a Medium Yield Field $ 300 250 200 150 100 50 0 Source: J. Beuerlein, Ohio State $ of Yield Profit Max Seed Cost ($) 250 220 190 160 130 100 Seeding Rate (1000 s)

Should Yield Environment Affect Seeding Rate Bu/Ac 60 50 40 30 20 10 0 197 177 154 Harvest Pop 131 Low Yield Environment Yield 92 65 250 220 190 160 130 100 Seeding Rate (1000 s) Source: J. Beuerlein, Ohio State Economic Analysis for a Low Yield Field $ 350 300 250 200 150 100 50 0 Max 245 $ of Yield Profit Seeding Rate (1000 s) Source: J. Beuerlein, Ohio State Seed Cost ($) 250 220 190 160 130 100

Conclusions 7.5 and 15 inch rows still out-yield 30 inch rows under optimal conditions Early planting pays if you seed the correct maturity group soybean All you need is 100,000 plants a -1 in moderate to high yield fields