Oakes Irrigation Research Site
Carrington Research Extension Center * North Dakota State University
P.O. Box 531, Oakes, ND 58474-0531, Phone: (701) 742-2744, FAX: (701) 742-2700, E-mail: Kelly.c.Cooper@ndsu.edu
Evaluation of Plant Populations and Row Spacing for Management of Sclerotinia in Soybeans
M. Wunsch, M. Schaefer, B. Kraft and S. Kallis, K. Cooper, L. Besemann, H. Eslinger
METHODS
General Agronomics: The study was on a Maddock sandy loam soil type. The previous crop was spring wheat.  The tillage operation consisted of cultivation with a soil finisher (May 2). The maintenance herbicide application was a PRE-EMERGENCE application of Spartan Elite (sulfentrazone, 0.7 lb ai/gal, and s-metolachlor, 6.3 lb ai/gal; FMC Corp., Philadelphia, PA) applied at 22 fl oz/ac on May 19 and a POST-EMERGENCE application of Roundup PowerMax (5.5 lbs/gal of the a.i. glyphosate = 4.5 lbs/gal of the acid equivalent; Monsanto Corp., St. Louis, MO) applied June 13 at 32 fl oz/ac with 1 lb AMS/10 gal and 0.125% v/v NIS.
Experimental design:  A completely randomized split-split block design.  Main factor = variety, sub-factor = seeding rate (132,000 pure live seeds/ac; 165,000 pls/ac; or 198,000 pls/ac), sub-sub-factor = row spacing (7-inch, 14-inch, 21-inch, or 28-inch row spacing).  The seeded plot size was 5 feet (center to center) by 25 feet long. The harvested plot size was 5 feet (center to center) and approximately 20 feet long.
To maintain a consistent gap from each outermost row of plots with 7-inch, 14-inch, and 21-inch row spacing and the outermost rows of adjacent plots, unharvested filler plots seeded to 14-inch rows were established on both sides of plots with 28-inch row spacing.  The use of these filler plots resulted in a consistent 18-inch gap between the outermost row of plots seeded to rows 7, 14, and 21 inches apart and the outermost rows of adjacent plots.  The outermost rows of plots with 28-inch row spacing were 25 inches from the outermost rows of adjacent plots. 
Planting details: The study was planted on May 16, 2016. Seed treatments used were Apron Maxx RTA (5.0 fl oz/100 lbs seed) + Imidacloprid 4ST (3 fl oz/100 lbs seed).  Imidacloprid 4ST (Willowood) contains 4 lbs/gal thiamethoxam; Apron Maxx RTA (Syngenta) contains 0.096 lb/gal mefenoxam and 0.064 lb/gal fludioxonil.
Plant establishment: Soybean establishment was assessed on June 16 when soybeans were at the V2 growth stage and on Sept. 8-12 at the R7 growth stage by counting all plants along the full length of the plot in rows 2, 3, 5, and 6 of each 7-row plot (7-in. row spacing), rows 2 and 3 of each 4-row plot (14-in. row spacing), row 2 of each 3-row plot (21-in. row spacing) and the northern row of each 2-row plot (28-in. row spacing). 
Bloom initiation: Bloom initiation, defined as 80 to 90% of plants at the R1 growth stage, was assessed three times a week as soon as the soybeans first began entering bloom and until the last variety reached 80-90% of plants with an open blossom.  Ten sequential plants within a row were evaluated at an arbitrarily selected location in each of six arbitrarily selected plots within each 12-plot main-factor block of each variety.  
Canopy closure and height: The percent canopy closure was assessed three times a week as soon as the canopy began to close in the first plots until the canopy reached full closure in all plots.  The height of the canopy at bloom initiation was assessed at one location per plot in all 12 plots of each main-factor (soybean variety) block when 80-90% of plants within that block, as assessed in bloom initiation notes, reached the R1 growth stage. 
Disease severity:  Sclerotinia incidence and severity were assessed on September 8-12 at the R7 growth stage using the 0 to 3 scale developed by Craig Grau (Grau and Radke 1984; Plant Disease 68: 56-58):  0 = no symptoms, 1 = lesions on lateral branches only, 2 = lesions on main stem, no wilt, and normal pod development, 3 = lesions on main stem resulting in wilting, poor pod fill, and plant death.  All plants were assessed along the full length of the plot in rows 2, 3, 5, and 6 of each 7-row plot (7-in. row spacing), rows 2 and 3 of each 4-row plot (14-in. row spacing), row 2 of each 3-row plot (21-in. row spacing) and the northern row of each 2-row plot (28-in. row spacing).  An average of 133 plants and minimum of 60 plants were assessed in each plot. 
Disease establishment and irrigation: This trial was established on a site with a prior history of Sclerotinia epidemics, and all pathogen inoculum originated from ambient disease pressure.  Supplemental irrigation was applied from mid-vegetative growth through mid-pod-fill as needed to maintain soil moisture an inch below the surface. 
Harvest, seed yield and quality assessment: The soybeans were harvested September 26. Yields were calculated on the basis of a 5-ft plot width and the measured plot length. Seed yield was adjusted to correct for sclerotia remaining in the mechanically cleaned grain.  Sclerotia contamination in the harvested grain (% by weight) was assessed on a 400-gram subsample of grain from each plot by manually removing sclerotia.  Sclerotia contamination in the mechanically cleaned grain was not assessed due to very low levels of sclerotia remaining in the grain after cleaning.
Test weight:  Test weight was evaluated by evaluating the weight of the grain that filed a dry pint.  Test weights were calculated on grain that was mechanically and manually cleaned; grain was cleaned on a mechanical shaker, and test weights were assessed on a subsample of the mechanically cleaned grain from which all remaining contaminants (including sclerotia) were manually removed. 
Management of Sclerotinia in Soybeans
FUNDED BY THE NORTH DAKOTA SOYBEAN COUNCIL 
Evaluation of plant populations and row spacing for management of Sclerotinia in soybeans at Oakes, ND (2016)  
Dairyland 'DSR 0711/R2Y'                                        
        Plant  Plant  Bloom to canopy closure y Sclerotinia Sclerotinia  Sclerotinia Yield Test weight Sclerotia in 
  Seeding rate   Row spacing population z population z Plant height x  incidence (%) v severity (1-3) u  sev. Index (0-3) t harvested grain s
        June 16 | V2 Sept. 8-12 | R7   R1 growth stage September 8-12  |  R7 growth stage 13% moisture  
        plants/ac plants/ac Days cm % 1 to 3 0 to 3 bu/ac lbs/bu % by weight
1 132,000 pls/ac   7-inch 96210   87504   3 a* 41 b* 3 a* 1.86 a* 0.05 a* 59 bc* 58.7 a* 0.01 a*
2 132,000 pls/ac   14-inch 102373   89372   6 b 43 ab 3 a 1.96 a 0.06 a 63 ab 58.8 a 0.02 a
3 132,000 pls/ac   21-inch 88677   84528   13 c 43 ab 1 a 3.00 a 0.04 a 66 a 58.5 a 0.01 a
4 132,000 pls/ac   28-inch 110885   102665   18 d 45 a 1 a 2.75 a 0.02 a 54 c 58.6 a 0.01 a
      F:     220.95 2.86 1.94 3.32 0.71 11.72 0.45 2.50
      P>F:     < 0.0001 0.0721 0.1661 0.0864 0.5633 0.0003 0.7237 0.0989
      CV:     11.1 5.9 96.0 26.0 110.3 6.2 0.9 74.2
1 165,000 pls/ac   7-inch 137373   128136   1 a* 41 b* 2 a* 2.61 a* 0.05 a* 62 a* 58.7 a* 0.02 a*
2 165,000 pls/ac   14-inch 132279   117097   5 b 44 ab 3 a 2.10 a 0.06 a 60 a 58.6 a 0.02 a
3 165,000 pls/ac   21-inch 132923   122923   9 c 45 ab 2 a 2.56 a 0.04 a 65 a 58.2 a 0.02 a
4 165,000 pls/ac   28-inch 142156   128829   17 d 46 a 2 a 2.67 a 0.05 a 55 b 58.2 a 0.02 a
      F:     185.49 3.43 0.26 2.07 0.22 14.57 1.38 0.03
      P>F:     < 0.0001 0.0445 0.8513 0.1924 0.8833 0.0001 0.2875 0.9938
      CV:     16.2 5.5 113.9 18.8 112.0 4.5 0.9 143.1
1 198,000 pls/ac   7-inch 154502   140730   0 a* 42 a* 1 a* 1.70 a* 0.02 a* 65 a* 58.5 a* 0.00 a*
2 198,000 pls/ac   14-inch 163959   152061   3 a 43 a 3 a 2.51 a 0.07 a 66 a 58.6 a 0.03 a
3 198,000 pls/ac   21-inch 184125   164202   9 b 44 a 2 a 2.73 a 0.05 a 65 ab 58.8 a 0.01 a
4 198,000 pls/ac   28-inch 165264   155724   16 c 46 a 1 a 2.08 a 0.03 a 58 b 58.4 a 0.01 a
      F:     96.05 1.86 2.63 2.65 2.79 4.94 0.42 3.03
      P>F:     < 0.0001 0.1794 0.0884 0.1199 0.0764 0.0140 0.7391 0.0623
      CV:     24.8 5.9 80.4 24.7 90.5 6.5 1.1 116.2
SUMMARY  Dairyland 'DSR 0711/R2Y'
1 AVERAGE   7-inch 129362   118790   1 a* 41 b* 2 ab*‡ 2.06 a* 0.04 a* 62 a* 58.6 a* 0.01 a*
2 AVERAGE   14-inch 132870   119510   4 b 43 ab 3 b 2.19 a 0.06 a 63 a 58.7 a 0.02 a
3 AVERAGE   21-inch 135242   123885   10 c 44 a 2 ab 2.76 b 0.04 a 65 a 58.5 a 0.01 a
4 AVERAGE   28-inch 139435   129073   17 d 45 a 1 a 2.50 ab 0.03 a 55 b 58.4 a 0.01 a
      F:     435.20 7.55 2.81 4.25 1.46 24.34 0.94 1.35
      P>F:     < 0.0001 0.0003 0.0498 0.0164 0.2376 < 0.0001 0.4281 0.2690
      CV:     17.0 5.8 77.2 23.2 106.6 5.8 1.0 130.6
1 132,000 pls/ac   AVERAGE 99536   91018   10 b* 43 a* 2 a*‡ 2.39 a* 0.04 a* 60 b* 58.7 a* 0.01 a*
2 165,000 pls/ac   AVERAGE 136182   124246   8 a 44 a 2 a 2.48 a 0.05 a 60 b 58.4 a 0.02 a
3 198,000 pls/ac   AVERAGE 166962   153179   7 a 44 a 2 a 2.26 a 0.04 a 64 a 58.6 a 0.01 a
      F:     21.32 2.24 0.12 2.34 0.22 12.85 0.76 4.80
      P>F:     0.0002 0.1569 0.8850 0.1464 0.8030 0.0017 0.4948 0.0506
      CV:     17.0 5.8 77.2 23.2 106.6 5.8 1.0 130.6
Pioneer 'P07T50R'
        Plant  Plant  Bloom to canopy closure y Sclerotinia Sclerotinia  Sclerotinia Yield Test weight Sclerotia in 
  Seeding rate   Row spacing population z population z Plant height x  incidence (%) v severity (1-3) u  sev. Index (0-3) t harvested grain s
        June 16 | V2 Sept. 8-12 | R7   R1 growth stage September 8-12  |  R7 growth stage 13% moisture  
        plants/ac plants/ac Days cm % 1 to 3 0 to 3 bu/ac lbs/bu % by weight
1 132,000 pls/ac   7-inch 110740   104274   -4 a*† 55 a* 13 a* 2.52 a* 0.33 a* 56 a* 58.5 a* 0.11 a*
2 132,000 pls/ac   14-inch 119368   110002   -3 a 57 a 17 a 2.65 a 0.45 a 55 a 58.3 a 0.22 a
3 132,000 pls/ac   21-inch 117104   110262   2 b 55 a 12 a 2.68 a 0.32 a 57 a 58.6 a 0.17 a
4 132,000 pls/ac   28-inch 119691   114086   9 c 55 a 15 a 2.74 a 0.41 a 47 b 58.1 a 0.21 a
      F:     159.08 1.41 0.58 0.77 0.69 9.08 1.61 1.03
      P>F:     < 0.0001 0.2797 0.6369 0.5305 0.5723 0.0011 0.2287 0.4073
      CV:     14.8 4.1 48.4 9.8 50.6 6.6 0.8 70.1
1 165,000 pls/ac   7-inch 131462   128247   -6 a*† 57 a* 6 a* 2.64 a* 0.17 a* 61 a* 58.3 a* 0.09 a*
2 165,000 pls/ac   14-inch 135531   128170   -4 b 56 a 9 a 2.62 a 0.24 a 61 a 58.8 a 0.15 a
3 165,000 pls/ac   21-inch 138329   134193   1 c 58 a 10 a 2.78 a 0.28 a 59 a 58.5 a 0.15 a
4 165,000 pls/ac   28-inch 140924   131544   9 d 58 a 9 a 2.70 a 0.26 a 53 b 58.1 a 0.10 a
      F:     278.94 0.48 1.67 0.57 1.76 10.16 1.69 1.23
      P>F:     < 0.0001 0.7033 0.2149 0.6454 0.1987 0.0007 0.2114 0.3340
      CV:     14.2 5.8 35.4 9.0 36.9 4.9 1.0 58.6
1 198,000 pls/ac   7-inch 163910   160177   -7 a*† 58 a* 9 a* 2.65 a* 0.26 a* 60 a* 58.2 a* 0.13 a*
2 198,000 pls/ac   14-inch 177151   163868   -5 b 59 a 8 a 2.69 a 0.23 a 61 a 58.8 a 0.14 a
3 198,000 pls/ac   21-inch 165225   161610   0 c 59 a 11 a 2.76 a 0.28 a 60 a 58.7 a 0.16 a
4 198,000 pls/ac   28-inch 180983   165578   8 d 59 a 11 a 2.91 a 0.32 a 52 b 58.6 a 0.18 a
      F:     179.20 0.33 0.38 0.87 0.48 6.69 2.90 0.49
      P>F:     < 0.0001 0.8014 0.7713 0.4779 0.7036 0.0044 0.0697 0.6931
      CV:     15.6 5.3 51.4 10.7 51.9 7.0 0.7 54.3
SUMMARY  Pioneer 'P07T50R'
1 AVERAGE   7-inch 135371   130899   -6 a*† 56 a* 10 a*‡ 2.60 a* 0.25 a* 59 a* 58.3 ab* 0.11 a*
2 AVERAGE   14-inch 144017   134014   -4 b 57 a 11 a 2.65 a 0.31 a 59 a 58.6 a 0.17 a
3 AVERAGE   21-inch 140219   135355   1 c 57 a 11 a 2.74 a 0.30 a 59 a 58.6 ab 0.16 a
4 AVERAGE   28-inch 147199   137069   9 d 58 a 12 a 2.78 a 0.33 a 51 b 58.2 b 0.16 a
      F:     588.37 0.56 1.91 1.70 0.86 23.96 2.87 1.60
      P>F:     < 0.0001 0.6414 0.1420 0.1801 0.4705 < 0.0001 0.0466 0.2018
      CV:     15.0 5.2 22.0 9.9 49.5 6.2 0.8 63.4
1 132,000 pls/ac   AVERAGE 116726   109656   1 a*† 56 b* 14 a*‡ 2.65 a* 0.38 a* 54 b* 58.4 a* 0.18 a*
2 165,000 pls/ac   AVERAGE 136562   130539   0 a 57 ab 9 a 2.69 a 0.24 a 58 a 58.4 a 0.12 a
3 198,000 pls/ac   AVERAGE 171817   162808   -1 a 59 a 10 a 2.75 a 0.27 a 58 a 58.5 a 0.15 a
      F:     2.07 4.71 1.21 0.67 1.09 8.43 0.89 0.60
      P>F:     0.1768 0.0363 0.3389 0.5345 0.3741 0.0072 0.4418 0.5669
      CV:     15.0 5.2 22.0 9.9 49.5 6.2 0.8 63.4
Pioneer '90M80' (0.8 maturity)
        Plant  Plant  Bloom to canopy closure y Sclerotinia Sclerotinia  Sclerotinia Yield Test weight Sclerotia in 
  Seeding rate   Row spacing population z population z Plant height x  incidence (%) v severity (1-3) u  sev. Index (0-3) t harvested grain s
        June 16 | V2 Sept. 8-12 | R7   R1 growth stage September 8-12  |  R7 growth stage 13% moisture  
        plants/ac plants/ac Days cm % 1 to 3 0 to 3 bu/ac lbs/bu % by weight
1 132,000 pls/ac   7-inch 114067   99520   5 a* 38 ab* 15 a* 2.54 a* 0.37 a* 56 a* 58.8 a* 0.15 a*
2 132,000 pls/ac   14-inch 114994   104251   6 a 37 a 13 a 2.58 a 0.34 a 57 a 58.7 a 0.23 a
3 132,000 pls/ac   21-inch 123690   107468   11 b 41 b 22 a 2.73 a 0.59 a 54 a 58.7 a 0.31 a
4 132,000 pls/ac   28-inch 109798   100531   18 c 38 ab 16 a 2.61 a 0.42 a 46 b 58.7 a 0.22 a
      F:     85.89 3.41 1.17 0.64 1.60 12.18 0.09 1.19
      P>F:     < 0.0001 0.0452 0.3551 0.6034 0.2316 0.0003 0.9645 0.3453
      CV:     16.2 5.7 50.5 9.4 49.0 6.4 1.1 62.8
1 165,000 pls/ac   7-inch 138239   126100   4 a* 39 b* 24 a* 2.69 a* 0.65 a* 53 a* 58.8 a* 0.23 a*
2 165,000 pls/ac   14-inch 146402   132977   5 a 39 ab 21 a 2.68 a 0.57 a 54 a 58.8 a 0.24 a
3 165,000 pls/ac   21-inch 150561   133765   10 b 42 ab 25 a 2.89 a 0.72 a 54 a 58.9 a 0.27 a
4 165,000 pls/ac   28-inch 151507   136629   15 c 42 a 20 a 2.80 a 0.55 a 45 b 59.2 a 0.33 a
      F:     47.14 3.39 2.66 1.70 0.55 10.48 0.80 0.85
      P>F:     < 0.0001 0.0459 0.0862 0.2107 0.6545 0.0006 0.5112 0.4856
      CV:     23.5 5.2 33.6 6.6 40.9 6.7 0.8 47.5
1 198,000 pls/ac   7-inch 171369   150511   3 a* 38 b* 22 a* 2.86 a* 0.64 a* 54 ab* 58.9 a* 0.30 a*
2 198,000 pls/ac   14-inch 183022   159082   4 a 39 ab 26 a 2.84 a 0.74 a 57 a 59.3 a 0.33 a
3 198,000 pls/ac   21-inch 165178   148267   10 b 41 ab 33 a 2.78 a 0.94 a 50 bc 59.2 a 0.41 a
4 198,000 pls/ac   28-inch 189928   173093   14 c 41 a 20 a 2.87 a 0.58 a 44 c 58.7 a 0.24 a
      F:     47.14 3.39 2.66 0.62 2.43 11.69 3.07 1.66
      P>F:     < 0.0001 0.0459 0.0862 0.6100 0.1058 0.0003 0.0599 0.2186
      CV:     23.5 5.2 33.6 4.5 34.5 7.9 0.7 0.6
SUMMARY  Pioneer '90M80' (0.8 maturity)
1 AVERAGE   7-inch 141225   125377   4 a* 38 c* 20 ab* 2.69 a* 0.55 ab* 55 ab* 58.8 a* 0.23 a*‡
2 AVERAGE   14-inch 148139   132103   5 a 38 bc 20 ab 2.70 a 0.55 ab 56 a 58.9 a 0.27 a
3 AVERAGE   21-inch 146476   129833   10 b* 41 a 27 b 2.80 a 0.75 b 53 bc 58.9 a 0.33 a
4 AVERAGE   28-inch 150411   136751   16 c 41 ab 18 a 2.76 a 0.52 a 45 c 58.9 a 0.27 a
      F:     202.85 5.67 3.21 1.16 3.54 32.86 0.16 1.86
      P>F:     < 0.0001 0.0022 0.0318 0.3366 0.0220 < 0.0001 0.9247 0.1495
      CV:     18.7 6.9 39.5 7.0 40.4 7.0 0.9 43.8
1 132,000 pls/ac   AVERAGE 115637   102942   10 b* 38 a* 16 a* 2.62 a* 0.43 a* 53 a* 58.7 b* 0.23 a*‡
2 165,000 pls/ac   AVERAGE 146677   132367   8 ab 41 a 22 a 2.76 ab 0.62 a 51 a 58.9 ab 0.27 a
3 198,000 pls/ac   AVERAGE 177374   157738   8 a 40 a 25 a 2.83 b 0.73 a 52 a 59.0 a 0.32 a
      F:     5.27 3.67 2.79 7.55 3.35 1.26 7.49 1.18
      P>F:     0.0273 0.0637 0.1090 0.0100 0.0771 0.3239 0.0103 0.3477
      CV:     18.7 6.9 39.5 7.0 40.4 7.0 0.9 43.8
Pioneer 'P08T36R' (0.8 maturity)
        Plant  Plant  Bloom to canopy closure y Sclerotinia Sclerotinia  Sclerotinia Yield Test weight Sclerotia in 
  Seeding rate   Row spacing population z population z Plant height x  incidence (%) v severity (1-3) u  sev. Index (0-3) t harvested grain s
        June 16 | V2 Sept. 8-12 | R7   R1 growth stage September 8-12  |  R7 growth stage 13% moisture  
        plants/ac plants/ac Days cm % 1 to 3 0 to 3 bu/ac lbs/bu % by weight
1 132,000 pls/ac   7-inch 103498   96100   -1 a*† 50 b* 5 a* 2.49 a* 0.14 a* 62 a* 58.5 a* 0.04 a*
2 132,000 pls/ac   14-inch 121098   101908   2 a 55 a 4 a 2.44 a 0.10 a 62 a 58.6 a 0.06 a
3 132,000 pls/ac   21-inch 118821   110362   6 b 57 a 4 a 2.42 a 0.10 a 62 a 58.3 a 0.05 a
4 132,000 pls/ac   28-inch 126702   105544   14 c 58 a 6 a 2.56 a 0.14 a 51 b 58.9 a 0.07 a
      F:     56.41 7.44 0.35 0.20 0.44 19.20 1.94 0.51
      P>F:     < 0.0001 0.0028 0.7912 0.8942 0.7253 < 0.0001 0.1667 0.6797
      CV:     25.4 5.3 73.0 17.1 76.8 5.3 0.9 72.4
1 165,000 pls/ac   7-inch 131084   126333   -3 a*† 54 b* 7 a* 2.50 a* 0.16 a* 62 a* 58.6 a* 0.07 a*
2 165,000 pls/ac   14-inch 140804   129907   0 a 55 b 6 a 2.48 a 0.15 a 62 a 58.7 a 0.07 a
3 165,000 pls/ac   21-inch 138469   124504   5 b 57 ab 6 a 2.80 b 0.16 a 62 a 58.6 a 0.11 a
4 165,000 pls/ac   28-inch 143242   134699   12 c 60 a 4 a 2.58 ab 0.11 a 52 b 58.6 a 0.08 a
      F:     82.18 5.51 0.38 4.37 0.29 20.60 0.17 0.41
      P>F:     < 0.0001 0.0094 0.7707 0.0294 0.8337 < 0.0001 0.9150 0.7451
      CV:     26.6 5.1 73.9 8.4 75.6 4.4 0.8 83.1
1 198,000 pls/ac   7-inch 159978   149744   -2 a*† 52 c* 4 a* 2.34 a* 0.09 a* 64 a* 58.5 a* 0.03 a*
2 198,000 pls/ac   14-inch 164795   168599   -2 a 55 bc 10 a 2.70 a 0.27 b 66 a 58.6 a 0.08 a
3 198,000 pls/ac   21-inch 169662   153664   7 b 60 ab 9 a 2.80 a 0.26 ab 63 a 58.6 a 0.14 a
4 198,000 pls/ac   28-inch 179291   160831   12 c 63 a 5 a 2.88 a 0.14 ab 55 b 58.5 a 0.11 a
      F:     65.65 7.23 3.05 2.29 3.30 10.14 0.15 2.37
      P>F:     < 0.0001 0.0032 0.0614 0.1201 0.0489 0.0007 0.9248 0.1142
      CV:     24.4 7.4 63.3 14.4 63.4 5.9 0.7 80.2
SUMMARY  Pioneer 'P08T36R' (0.8 maturity)
1 AVERAGE   7-inch 131520   124059   -2 a*† 52 c* 5 a*‡ 2.44 a* 0.13 a* 63 a* 58.5 a* 0.05 a*
2 AVERAGE   14-inch 142232   133471   0 a 55 bc 7 a 2.54 a 0.17 a 63 a 58.6 a 0.07 a
3 AVERAGE   21-inch 142317   129510   6 a 58 ab 6 a 2.67 a 0.17 a 62 a 58.5 a 0.10 a
4 AVERAGE   28-inch 149745   133691   13 a 60 a 5 a 2.67 a 0.13 a 53 b 58.7 a 0.09 a
      F:     197.74 18.55 0.55 2.00 0.94 45.22 0.65 2.44
      P>F:     < 0.0001 < 0.0001 0.6485 0.1315 0.4294 < 0.0001 0.5878 0.0773
      CV:     25.5 6.0 46.7 13.7 71.2 5.3 0.8 81.8
1 132,000 pls/ac   AVERAGE 117530   103479   5 a*† 55 a* 5 a*‡ 2.48 a* 0.12 a* 59 a* 58.6 a* 0.05 a*
2 165,000 pls/ac   AVERAGE 138400   128861   4 a 57 a 6 a 2.59 a 0.14 a 60 a 58.6 a 0.08 a
3 198,000 pls/ac   AVERAGE 168431   158209   3 a 57 a 7 a 2.68 a 0.19 a 62 a 58.5 a 0.09 a
      F:     2.93 2.55 1.16 2.37 1.04 2.97 0.15 1.05
      P>F:     0.0995 0.1276 0.3530 0.1441 0.3883 0.0971 0.8603 0.3844
      CV:     25.5 6.0 46.7 13.7 71.2 5.3 0.8 81.8
z Plant population:  assessed on June 16 when soybeans were at the V2 growth stage and again near maturity on Sept. 8-12 at the R7 growth stage by counting all plants along the full length of the plot in rows 2, 3, 5, and 6 of each 7-row plot (7-in. row spacing), rows 2 and 3 of each 4-row plot (14-in. row spacing), row 2 of each 3-row plot (21-in. row spacing) and the northern row of each 2-row plot (28-in. row spacing).
y Days from bloom to canopy closure:  Number of days between bloom initiation (80-90% of the plants with an open blossom) and canopy closure (canopy fully covered ground between the rows).
x Canopy height:  Height of the canopy when 80 to 90% of plants had at least one open blossom; assessed at one location per plot.
v Sclerotinia stem rot incidence: assessed on Sept. 8-12 at the R7 growth stage by evaluating all plants along the full length of the plot in rows 2, 3, 5, and 6 of each 7-row plot (7-in. row spacing), rows 2 and 3 of each 4-row plot (14-in. row spacing), row 2 of each 3-row plot (21-in. row spacing) and the northern row of each 2-row plot (28-in. row spacing).  An average of 133 plants and minimum of 60 plants were assessed in each plot.
u Sclerotinia severity:  Average disease severity among plants expressing Sclerotinia stem rot.  Assessed on Sept. 8-12 at the R7 growth stage using the 1 to 3 scale developed by Craig Grau (Grau and Radke 1984; Plant Disease 68: 56-58):  1 = lesions on lateral branches only, 2 = lesions on main stem, no wilt, and normal pod development, 3 = lesions on main stem resulting in wilting, poor pod fill, and plant death.  All plants were assessed along the full length of the plot in rows 2, 3, 5, and 6 of each 7-row plot (7-in. row spacing), rows 2 and 3 of each 4-row plot (14-in. row spacing), row 2 of each 3-row plot (21-in. row spacing) and the northern row of each 2-row plot (28-in. row spacing).  An average of 133 plants and minimum of 60 plants were assessed in each plot.
t Sclerotinia disease severity index:  Average disease severity across all plants, including those without any disease.  Assessed on Sept. 8-12 at the R7 growth stage using the 0 to 3 scale developed by Craig Grau (Grau and Radke 1984; Plant Disease 68: 56-58):  0 = no symptoms, 1 = lesions on lateral branches only, 2 = lesions on main stem, no wilt, and normal pod development, 3 = lesions on main stem resulting in wilting, poor pod fill, and plant death.  All plants were assessed along the full length of the plot in rows 2, 3, 5, and 6 of each 7-row plot (7-in. row spacing), rows 2 and 3 of each 4-row plot (14-in. row spacing), row 2 of each 3-row plot (21-in. row spacing) and the northern row of each 2-row plot (28-in. row spacing).  An average of 133 plants and minimum of 60 plants were assessed in each plot.
s Sclerotia in harvested grain:  Percent sclerotia contaminants (by weight) in the harvested grain; assessed on an approx. 400-gram subsample of grain from each plot by manually removing sclerotia.
* Within-column means followed by different letters are significantly different (P < 0.05; Tukey multiple comparison procedure).
‡ To meet model assumptions of homoskedasticity and normality, analysis of variance was conducted on data subjected to a systematic natural-log transformation.  For ease of interpretation, treatment means are presented for the untransformed data.
† To permit accurate assessment of the coefficient of variation, analysis of variance was conducted on data subjected to a systematic transformation in which all values were increased by a fixed integer such that the smallest value equaled zero.  This transformation had no impact on the F or P values but permitted accurate assessment of the CV.  For ease of interpretation, treatment means are presented for the untransformed data.      
        Plant  Plant  Bloom to canopy closure y Sclerotinia Sclerotinia  Sclerotinia Yield Test weight Sclerotia in 
  Seeding rate   Row spacing population z population z Plant height x  incidence (%) v severity (1-3) u  sev. Index (0-3) t harvested grain s
          Sept. 8-12 | R7   R1 growth stage September 8-12  |  R7 growth stage 13% moisture  
        plants/ac plants/ac Days cm % 1 to 3 0 to 3 bu/ac lbs/bu % by weight
SUMMARY  AVERAGE ACROSS ALL VARIETIES
1 AVERAGE   7-inch 134369   124781   -1 a*† 47 c* 9 a*‡ 2.45 a* 0.24 a*‡ 60 a* 58.6 a* 0.10 a*
2 AVERAGE   14-inch 141815   129775   1 b  49 b 10 a 2.52 a 0.27 ab 60 a 58.7 a 0.13 ab
3 AVERAGE   21-inch 141064   129646   7 c 50 a 11 a 2.74 b 0.31 b 60 a 58.6 a 0.15 b
4 AVERAGE   28-inch 146698   134146   13 d 51 a 9 a 2.68 b 0.25 ab 51 b 58.5 a 0.13 ab
      F:     signif interaction: signif interaction: 2.52 signif interaction: signif interaction: signif interaction: 1.77 4.44
      P>F:     variety x row sp variety x row sp 0.0592 variety x row sp variety x row sp variety x row sp 0.1546 0.0049
      CV:     17.9 5.9 30.8 12.5 47.8 6.0 0.9 69.6
1 AVERAGE   14-inch 112357   101774   6 b*† 48 b* 9 a*‡ 2.53 a* 0.24 a*‡ 57 a* 58.6 a* 0.12 a*
2 AVERAGE   21-inch 139455   129003   5 a 50 a 10 a 2.63 b 0.26 a 58 ab 58.6 a 0.12 a
3 AVERAGE   28-inch 171146   157984   4 a 50 a 11 a 2.63 ab 0.31 a 59 b 58.7 a 0.14 a
      F:     25.32 11.35 0.42 4.10 1.13 6.38 0.78 0.89
      P>F:     < 0.0001 0.0001 0.6582 0.0241 0.3324 0.0039 0.4669 0.4187
      CV:     17.9 5.9 30.8 12.5 47.8 6.0 0.9 69.6
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