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Variable names and definitions for the statistical models comparing no-till yields with tillage yields.

 
Variable name Variable definition Mean Hypothesized sign
Dependent variables
ln(RR) natural logarithm of the ratio of no-till to tillage yields –0.038
NTPROB = 1 if no-till yields < tillage yields; 0 otherwise 0.63
Explanatory variables
TECH natural logarithm of the year the experiment began 2.81
LOGYR natural logarithm of each year of the experiment 1.41 +
RAIN actual annual rainfall at experiment location, cm 76.96 +/–
Crop variables
SORG = 1 if sorghum; 0 otherwise 0.07 +/–
WHEAT = 1 if wheat; 0 otherwise 0.22 +/–
CORN† = 1 if corn; 0 otherwise 0.50 +/–
SOY = 1 if soybean; 0 otherwise 0.16 +/–
OAT = 1 if oat; 0 otherwise 0.01 +/–
COTT = 1 if cotton; 0 otherwise 0.04 +/–
Tillage variables
TILL = 1 if comparing conventional tillage to no-till; 0 for comparing reduced tillage to no-till 0.61 +/–
Soil texture variables
SAND = 1 if sandy soil; 0 otherwise 0.09 +
SILT = 1 if silty soil; 0 otherwise 0.01
CLAY = 1 if clay soil; 0 otherwise 0.03
LOAM† = 1 if loamy soil; 0 otherwise 0.87
Farm resource region
HEART† = 1 if Heartland region; 0 otherwise 0.39 +/–
NCRES = 1 if Northern Crescent region; 0 otherwise 0.13
NGP = 1 if Northern Great Plains region; 0 otherwise 0.07
PGATE = 1 if Prairie Gateway region; 0 otherwise 0.20 +/–
EASTU = 1 if Eastern Upland region; 0 otherwise 0.02 +/–
SOSEA = 1 if Southern Seaboard region; 0 otherwise 0.11 +
FRIM = 1 if Fruitful Rim region; 0 otherwise 0.02 +/–
BANDR = 1 if Basin and Range region; 0 otherwise 0.04 +/–
MISS = 1 if Mississippi Portal region; 0 otherwise 0.02 +
Reference dummy variables excluded from the regression models.



View Full Table | Close Full ViewTable 2.

Empirical mean yield regression model comparing no-till yields with tillage yields. The dependent variable is the natural logarithm of the ratio of no-till to tillage yields.

 
Explanatory variable† Coefficient t value
INTERCEPT –0.005370 –0.11
SORG 0.444500** 5.33
WHEAT 0.222500** 2.62
SOY –0.169500 –1.01
OAT –0.518700* –2.47
COTT –1.019900 –1.59
SAND 0.001908 0.07
SILT –0.122800‡ –1.83
CLAY 0.009623 0.20
TILL –0.002650 –0.28
TECH 0.004154 0.34
LOGYR –0.022690** –2.67
RAIN –0.000200 –0.92
NCRES –0.006180 –0.39
NGP –0.039590 –1.13
PGATE 0.003242 0.18
EASTU 0.038120 1.19
SOSEA 0.071550** 2.72
FRIM –0.097470** –2.77
BANDR –0.107100* –2.46
MISS 0.085000‡ 1.68
SORG × SAND –0.219500* –2.57
SORG × CLAY 0.022640 0.29
SORG × TECH –0.074340** –3.60
SORG × LOGYR 0.025760 1.06
SORG × RAIN –0.003000** –4.62
WHEAT × SAND –0.211600** –4.49
WHEAT × CLAY –0.098090 –1.08
WHEAT × TECH –0.049200* –2.21
WHEAT × LOGYR –0.001380 –0.08
WHEAT × RAIN –0.000700 –1.48
SOY × SAND –0.206300** –4.16
SOY × CLAY 0.002139 0.03
SOY × TECH 0.046260 0.98
SOY × LOGYR 0.023290 1.36
SOY × RAIN 0.000340 0.65
OAT × LOGYR 0.151500 1.48
OAT × RAIN 0.009060* 2.58
COTT × SAND 0.155300 1.43
COTT × CLAY 0.012990 0.10
COTT × TECH 0.249700 1.26
COTT × LOGYR 0.168900** 3.40
COTT × RAIN 0.000510 0.65
n 1546
–2 Residual log likelihood –811.1
Akaike information criterion –807.1
Sample-size-corrected Akaike information criterion –807.1
Bayesian information criterion –811.1
*Significant at the 0.05 confidence level.
**Significant at the 0.01 confidence level.
INTERCEPT contains the reference categories of corn crop, loam texture, and Heartland region; SORG, sorghum crop; WHEAT, wheat crop; SOY, soybean crop; OAT, oat crop; COTT, cotton crop; SAND, sand texture; SILT, silt texture; CLAY, clay texture; TILL, comparison of tillage; TECH, natural logarithm of year experiment began; LOGYR, natural logarithm of each year of experiment; RAIN, actual rainfall at location; NCRES, Northern Crescent region; NGP, Northern Great Plains region; PGATE, Prairie Gateway region; EASTU, Eastern Upland region; SOSEA, Southern Seaboard region; FRIM, Fruitful Rim region; BANDR, Basin and Range region; MISS, Mississippi Portal region.
Significant at the 0.10 confidence level.



View Full Table | Close Full ViewTable 3.

Predicted no-till yields as a percentage of tillage yields by USDA Economic Research Service farm resource region (Fig. 1) and soil texture.

 
USDA-ERS region Annual precipitation Soil texture No-till yield increase†
Corn Sorghum Cotton Soybean Wheat Oat
cm %
Heartland 81.5 loam 95.63 98.29 –‡ 97.67 147.50
clay 96.56 98.82
Northern Crescent 71.9 loam 95.23 96.94 98.32
sand 95.41
Northern Great Plains 38.4 loam 98.00
Prairie Gateway 64.8 loam 96.27 104.03 91.84 97.76 99.89
clay 98.46 107.44 93.94 91.43
Eastern Upland 96.7 loam 99.05 101.68 100.51
Southern Seaboard 110.1 loam 102.14 99.73 105.33 102.68
sand 102.34 77.51 116.70 85.86 83.25
Fruitful Rim 34.1 loam 92.85
sand 87.75
Basin and Range 22.0 loam 92.97
silt 82.22
Mississippi Portal 132.8 loam 101.79 107.10
clay 108.37 93.33
Predictions were calculated using the estimated regression coefficients in Table 2, sample means for TECH (2.81), LOGYR (1.41), and RAIN for each farm resource region, and TILL = 1.
Crop yield data were not available for the farm resource region and soil texture classification.



View Full Table | Close Full ViewTable 4.

Estimated logit model predicting the probability of no-till yields lower than tillage. The dependent variable is 1 if no-till yields < tillage yields, 0 otherwise.

 
Explanatory variable† Coefficient t value
INTERCEPT –0.64740 –0.74
SORG –4.77400* –2.40
WHEAT –1.33500 –0.84
SOY 3.24960 1.40
OAT 6.19830 1.36
COTT 15.43730 1.64
SAND –0.77000 –1.47
SILT 5.99220 0.79
CLAY –0.14550 –0.20
TILL –0.10150 –0.73
TECH 0.28530 1.16
LOGYR 0.23180‡ 1.83
RAIN 0.01057**
NCRES –0.35170 –0.98
NGP –0.98830 –1.30
PGATE –0.56220 –1.36
EASTU –0.29090 –0.46
SOSEA –0.91590* –2.05
FRIM 0.76980 0.99
BANDR –0.22560 –0.21
MISS –0.89940 –1.05
SORG × SAND 5.74460 0.46
SORG × CLAY –0.38470 –0.32
SORG × TECH 0.25120 0.51
SORG × LOGYR –0.13440 –0.30
SORG × RAIN 0.05326**
WHEAT × SAND 2.62090** 3.17
WHEAT × CLAY 0.86650 0.70
WHEAT × TECH 0.42720 0.96
WHEAT × LOGYR 0.08420 0.37
WHEAT × RAIN –0.00740** –∞
SOY × SAND 3.3580** 4.42
SOY × CLAY 0.78220 0.70
SOY × TECH –0.86690 –1.32
SOY × LOGYR –0.41300‡ –1.81
SOY × RAIN –0.01580** –∞
OAT × LOGYR –2.25860 –1.25
OAT × RAIN –0.10030 –1.43
COTT × SAND –6.14070 –0.57
COTT × CLAY 4.99320 0.31
COTT × TECH –4.26560 –1.48
COTT × LOGYR –1.38340‡ –1.82
COTT × RAIN –0.00830** –∞
n 1546
–2 log likelihood 1719.07
Akaike information criterion 1807.07
Bayesian information criterion 1915.06
Sample-size-corrected Akaike information criterion 1809.71
*Significant at the 0.05 confidence level.
**Significant at the 0.01 confidence level.
INTERCEPT contains the reference categories of corn crop, loam texture, and Heartland region; SORG, sorghum crop; WHEAT, wheat crop; SOY, soybean crop; OAT, oat crop; COTT, cotton crop; SAND, sand texture; SILT, silt texture; CLAY, clay texture; TILL, comparison of tillage; TECH, natural logarithm of year experiment began; LOGYR, natural logarithm of each year of experiment; RAIN, actual rainfall at location; NCRES, Northern Crescent region; NGP, Northern Great Plains region; PGATE, Prairie Gateway region; EASTU, Eastern Upland region; SOSEA, Southern Seaboard region; FRIM, Fruitful Rim region; BANDR, Basin and Range region; MISS, Mississippi Portal region.
Significant at the 0.10 confidence level.



View Full Table | Close Full ViewTable 5.

Predicted no-till downside yield risk probabilities relative to tillage yields by USDA Economic Research Service farm resource region (Fig. 1) and soil texture.

 
USDA-ERS region Annual precipitation Soil texture Predicted no-till downside risk probability†
Corn Sorghum Cotton Soybean Wheat Oat
cm
Heartland 81.5 loam 0.78 0.79 –‡ 0.55 0.02
clay 0.75 0.69
Northern Crescent 71.9 loam 0.69 0.47 0.56
sand 0.50
Northern Great Plains 38.4 loam 0.38
Prairie Gateway 64.8 loam 0.62 0.42 0.81 0.43 0.50
clay 0.59 0.30 1.00 0.67
Eastern Upland 96.7 loam 0.75 0.45 0.59
Southern Seaboard 110.1 loam 0.65 0.77 0.29 0.45
sand 0.46 1.00 0.00 0.85 0.84
Fruitful Rim 34.1 loam 0.78
sand 0.68
Basin and Range 22.0 loam 0.87
silt 1.00
Mississippi Portal 132.8 loam 0.78 0.27
clay 0.41 0.65
Predictions were calculated using the estimated regression coefficients in Table 4, sample means for TECH (2.81) and LOGYR (1.41) for each farm resource region, and TILL = 1.
Crop yield data were not available for the farm resource region and soil texture classification.