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Dates of key field operations and data collection.

 
Date
Operation 2008–2009 2009–2010
Planted cover crops 2 Sept. 4 Sept.
Evaluated cover crop emergence 29 Oct. 16 Oct.
Evaluated cover crop survival 12 May 2 Apr.
Sampled cover crop biomass 29 May 27 May
Evaluated vetch flowering 30 May 28 May
Flail-mowed cover crops 30 May 30 May
Strip-tilled 9 June 14 June
Planted sweet corn 21 June 15 June
Applied sidedress N 21 July 14 July
Harvested sweet corn 11 Sept. 25 Aug.



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Monthly growing degree days (GDD) and rainfall totals at East Lansing, MI, 2008–2010.

 
GDD†
Rainfall
Month 2008–2009 2009–2010 2008–2009 2009–2010
mm
September‡ 347 345 189 24
October 172 161 41 92
November 67 64 32 24
March 53 57 76 16
April 150 218 165 74
May 315 365 109 129
June§ 126 187 6 42
July 283 394 61 64
August 316 375 105 34
Sept. to Nov.‡ 586 570 261 141
March to May 518 641 351 218
June to August§ 725 956 171 140
The GDD calculated with base 4° C for period of vetch growth (September to May) and base 10° C for period of sweet corn growth (June to August).
Beginning after vetch planting (4 Sept. 2008; 5 Sept. 2009).
§Beginning after sweet corn planting (21 June 2009; 14 June 2010).



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Estimated shoot N fixation and cost of nitrogen fixed (CNF), 2009 and 2010.

 
Estimated shoot N fixed†
Cropping system and vetch variety Percentage
kg ha−1
CNF‡
2009 2010 2009 2010 2009 2010
% kg ha−1 $ kg−1
Monoculture
 Oregon 35a§ 79 48a 89a 2.79c 1.19ab
 Purple Prosperity 65b 62 93b 68ab 1.26bc 1.87ab
 Purple Bounty 65b 71 90b 112a 1.22bc 0.95ab
In mixture with rye
 Oregon 63b 71 62ab 46b 0.90a 1.35a
 Purple Prosperity 60b 75 60a 35bc 0.93ab 1.79ab
 Purple Bounty 72b 77 42ab 22c 1.45bc 3.12b
Sources of variation Significance of fixed effects
 System ns# ns *** * ns
 Variety ns ns ns ns ns ns
 System × variety * ns +_ + + +
*Significant at the 0.05 probability level.
**Significant at the 0.01 probability level.
***Significant at the 0.001 probability level.
From Eq. [1] and [3].
From Eq. [5].
§Within columns, means followed by the same letter are not significantly different according to LSD (0.05)
+, significant at the 0.10 probability level.
#ns, nonsignificant at the 0.10 probability level.



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Mean (± MSE) sweet corn yield and quality characteristics, 2009 and 2010.

 
Characteristics of marketable ears
Cropping system and vetch variety Marketable yield
Length Weight
Soluble solids
2009 2010 2009/2010 2009 2010 2009/2010
thousands of ears ha−1 cm ear−1 kg ear−1 °Bx†
Monoculture
 Oregon 12.9(2.2) 22.4(1.8) 17.1(0.3) 0.37(0.07) 0.25(0.07) 19.9(0.1)
 Purple Prosperity 18.7(3.2) 19.5(3.8) 17.4(0.1) 0.36(0.08) 0.26(0.15) 19.2(0.2)
 Purple Bounty 17.0(4.6) 20.0(3.4) 17.7(0.2) 0.33(0.07) 0.30(0.17) 19.8(0.2)
Mixture
 Oregon 19.2(2.5) 17.2(2.0) 17.7(0.3) 0.35(0.12) 0.30(0.16) 19.7(0.3)
 Purple Prosperity 20.2(1.5) 20.1(0.9) 17.8(0.2) 0.35(0.04) 0.30(0.10) 19.3(0.1)
 Purple Bounty 15.2(2.0) 21.3(1.0) 17.8(0.1) 0.37(0.10) 0.28(0.10) 20.5(0.1)
Sources of variation Significance of fixed effects
 Cropping system (CS) ns‡ ns ns ns ns ns
 Variety (V) ns ns ns ns ns ns
 CS × V ns ns ns ns ns ns
Degrees Brix (see methods for definition and interpretation of °Bx obtained from refractometer).
ns, nonsignificant at the 0.05 probability level.