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Analysis of variance for percentage control of cereal rye as influenced by year, cultivar, termination date, and planting date.

 
Effect % Control
P > F
Cover crop (CC) 0.0036
Termination date (TD) <0.0001
CC X TD <0.0001
Planting date (PD) <0.0001
CC X PD 0.4005
TD X PD 0.1982
CC X TD X PD 0.9886
Year 0.2407



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Mean cereal rye control as influenced by planting date (year, cultivar, and termination date pooled). Similar letters indicate no significant difference (P < 0.05) using the Tukey-Kramer method.

 
Planting date Control
%
25 August 79 a
5 September 77 ab
15 September 73 bc
25 September 70 cd
5 October 67 de
15 October 63 e



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Mean cereal rye control as influenced by cultivar × termination date (year and planting date pooled). Similar letters among both columns indicate no significant difference (P < 0.05) using the Tukey-Kramer method.

 
Termination date Aroostook Wheeler
% control
1 May 41 b 21 a
10 May 79 d 71 c
20 May 88 ef 86 e
30 May 94 f 93 f



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Cereal rye growth stage (Zadoks) as influenced by cultivar, planting date, and termination date for 2005 and 2006. Table values represent means of the four replications. Variability among replications was not estimable due to the fact that there was no variability among the replications.

 
Planting date 2005 2006
Cultivar 1 May 10 May 20 May 30 May 1 May 10 May 20 May 30 May
growth stage (Zadoks)
Aroostook 25 August 45 55 60 73 58 63 73 85
5 September 41 53 59 71 58 61 73 85
15 September 41 50 57 71 57 60 71 83
25 September 40 49 55 70 55 60 71 83
5 October 38 41 53 69 53 59 69 80
15 October 34 41 53 68 52 57 65 71
Wheeler 25 August 45 55 59 71 48 59 70 80
5 September 39 53 57 71 48 59 67 75
15 September 39 50 55 70 47 57 66 75
25 September 37 45 53 67 45 57 64 71
5 October 34 40 53 67 41 55 62 69
15 October 32 39 50 63 37 48 58 68



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Coefficients for the nonlinear regression using a dose response model of cereal rye percentage control as a function of phenological development where Y is % cereal rye control (%); d is the % control at the upper growth stage limit; e is the effective growth stage 50, the growth stage producing a response half-way between d and the lower limit; and b is the relative slope around e (% control/growth stage) (Ritz and Streibig, 2005). Analysis was conducted by year with cultivars pooled and by cultivar within years to test for significance of parameter estimates. Due to lack of data at the lower range of growth stages for Aroostook rye in 2006, differences in cultivars in 2006 could not be tested. The null hypothesis in this case is formulated as a ratio of estimates, and therefore the t test is comparing the observed ratio with a value of 1. The P values are probability of getting a t statistic greater than the calculated t value. Values in parentheses are the standard error.

 
Model parameters and control threshold Year comparison 2005
Cultivar comparison
2005 2006 P value Aroostook Wheeler P value
b −7.99 (0.48) −8.90 (0.62) 0.247 −8.71 (1.00) −7.52 (0.86) 0.365
d 95.37 (1.73) 99.39 (1.60) 0.089 94.41 (3.01) 95.81 (3.56) 0.766
e 43.91 (0.39) 50.22 (0.39) 0.001 44.42 (0.70) 43.23 (0.83) 0.271
EGS85 55 (1.41) 61 (0.65) 0.001 54 (2.13) 54 (1.78) 0.931



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Thermal-based phenological models predicting cultivars of cereal rye phenological development (years pooled). The parameter estimates characterize the effects of growing degree days (GDD) on growth stage of two cereal rye cultivars. Included are adjusted R2 values and Akaike Information criteria (AIC) for goodness of fit and model selection, respectively. The parameter β0 is the intercept, β1 and β2 are parameter coefficients defining the slope of the equation and the proportional relationship between FallGDD and SpringGDD

 
Thermal models β0 Total β1 Fall β1 Spring β2 Adj. R 2 AIC
Aroostook SpringGDD 21.08 0.067 0.88 1130
TotalGDD 35.96 0.017 0.34 1452
FallGDD and SpringGDD 15.19 0.007 0.068 0.93 1031
Wheeler SpringGDD 18.74 0.064 0.87 1121
TotalGDD 29.83 0.018 0.43 1402
FallGDD and SpringGDD 11.11 0.009 0.064 0.96 882