Table 3. Model II estimated GEE coefficients for corn field-acreage allocation equations by field
structural practice (technology), and by conservation program participation.
[Model II: (Aj,p) = f(normalized input prices, technology class, installation, & socio-environmental variables)].
|
Equation/Variable____________________ |
________Program Non-Participants_______ |
Program Participants | ||
|
_________Estimate_______ |
T-Tests b |
Estimate |
T-Tests | |
|
Model II | ||||
|
Constant |
2.5478 |
1.04 |
4.4805 |
1.30 |
|
Corn Field Acres Planted (with): | ||||
|
EQ1: No structural practices: a | ||||
|
N price |
119.9414 * |
3.64 |
- 41.1041 |
- 0.62 |
|
Ag. wage |
0.4437 *** |
1.56 |
- 2.2255 * |
- 4.25 |
|
Diesel price |
- 21.7852 * |
- 3.37 |
15.5230 |
1.30 |
|
EQ2: Only infield structures: a | ||||
|
N price |
- 68.3726 * |
- 2.56 |
4.6041 |
0.10 |
|
Ag. wage |
0.1951 |
0.77 |
0.3661 |
0.75 |
|
Diesel price |
9.3637 ** |
1.96 |
- 4.5506 |
- 0.51 |
|
EQ3: Only perimeter-field structures: a | ||||
|
N price |
- 14.6446 |
- 0.94 |
29.8064 |
0.91 |
|
Ag. wage |
- 0.3468 * |
- 3.54 |
1.2607 * |
4.37 |
|
Diesel price |
6.1154 ** |
1.97 |
- 12.9867 * |
- 2.20 |
|
EQ4: Both structural practices: a | ||||
|
N price |
- 5.4257 |
- 0.98 |
- 25.2886 |
- 1.37 |
|
Ag. wage |
0.1431 |
0.93 |
0.2792 |
0.71 |
|
Diesel price |
________2.4690_______ |
1.20 |
0.8440 |
_________0.19 |
|
Technology class variables: |
Units_________________ |
Estimate |
______T-tests | |
|
Only infield structures |
(Yes = 1) |
- 0.9789 |
- 0.25 | |
|
Only perimeter-field structures |
(Yes = 1) |
- 4.1142 |
- 1.43 | |
|
Both structures |
(Yes = 1) |
- 4.5246 *** |
- 1.71 | |
|
Installation dummy variables: | ||||
|
Installed in 2005 |
(Yes = 1) |
0.0080 |
0.12 | |
|
Installed within last 10 years |
(Yes = 1) |
- 0.0088 |
- 0.20 | |
|
Installed prior to 1990 |
(Yes = 1) |
0.0213 |
0.19 | |
|
Socio-Environmental Variables: | ||||
|
Farm tenure rate |
(owned/operated acres) |
0.0735 |
1.04 | |
|
Farm cropland acres |
(acres) |
0.0001 * |
3.06 | |
|
Crop rotation |
(Yes = 1) |
- 0.2240 * |
- 2.46 | |
|
Gully erosion on field |
(Yes = 1) |
0.1264 *** |
1.52 | |
|
Field next to water body |
(Yes = 1) |
- 0.1150 ** |
- 1.98 | |
|
Surface drainage |
(Yes = 1) |
0.1811 * |
2.75 | |
|
Improve wildlife habitat |
(Yes = 1) |
- 0.1356 |
- 1.25 | |
|
Log Likelihood Value (L2) = - 2872.0891 |
R2 = 0.10 Likelihood Ratio (L1:L2) = 68.10, d.f. = 7, |
p = .05 | ||
a State average per unit prices (2005) for nitrogen ($/lb.), agricultural wage ($/hr.), and diesel ($/gal.) were normalized using State average
2005 corn price ($/bu.).
b Critical values for the t tests are 1.52 (***), 1.76 (**), and 2.14 (*) for the 15 %, 10 %, and 5 % significance levels, respectively.
Standard errors were computed using the delete-a-group Jackknife approach (Dubman, 2000).
Note: Infield conservation structural practices included terraces, grassed waterways, vegetative buffers, contour buffers, filter strips, and grade
stabilization structures. Perimeter-field conservation structural practices included hedgerow plantings, stream-side forest buffers, stream-
side herbaceous buffers, windbreaks or herbaceous wind barriers, field borders, and critical area plantings.
Source: 2005 CEAP-ARMS Phase II data (for corn), Economic Research Service, USDA.
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