Table 2. Model I estimated GEE coefficients for corn field acreage allocation equations by field
structural practice (technology), and by conservation program participation.
[Model I: (Aj,p) = f(normalized input prices, technology class & installation variables)].
|
Equation/Variable______________________ |
Program Non-Participants_____ |
_______Program Participants_______ | ||
|
Estimate______ |
T-Tests b |
_____Estimate________ |
T-Tests | |
|
Model I | ||||
|
Constant |
2.8045 |
1.13 |
5.6368 *** |
1.71 |
|
Corn Field Acres Planted (with): EQ1: No structural practices: a | ||||
|
N price |
119.8528 * |
3.78 |
- 50.6681 |
- 0.78 |
|
Ag. Wage |
0.4036 |
1.41 |
- 2.3509 * |
- 3.88 |
|
Diesel price |
- 21.9501 * |
- 3.48 |
16.7863 |
1.43 |
|
EQ2: Only infield structures: a | ||||
|
N price |
- 66.1984 * |
- 2.48 |
2.9938 |
0.07 |
|
Ag. Wage |
0.1891 |
0.76 |
0.2749 |
0.61 |
|
Diesel price |
8.9845 ** |
1.88 |
- 4.7731 |
- 0.59 |
|
EQ3: Only perimeter-field structures: a | ||||
|
N price |
- 13.4583 |
- 0.93 |
29.6982 |
0.91 |
|
Ag. Wage |
- 0.3608 * |
- 3.83 |
1.1760 * |
4.73 |
|
Diesel price |
5.8741 ** |
1.96 |
- 13.4898 * |
- 2.27 |
|
EQ4: Both structural practices: a | ||||
|
N price |
- 4.4147 |
- 0.82 |
- 24.6257 |
- 1.25 |
|
Ag. Wage |
0.1283 |
0.95 |
0.1979 |
0.52 |
|
Diesel price |
2.2566 |
1.17 |
0.1968 |
0.04 |
|
Technology class variables: |
Units_______________ |
Estimate |
T-tests_________ | |
|
Only Infield structures |
(Yes = 1) |
- 1.2985 |
- 0.36 | |
|
Only perimeter-field structures |
(Yes = 1) |
- 4.3706 |
- 1.31 | |
|
Both structures |
(Yes = 1) |
- 4.7776 *** |
- 1.56 | |
|
Installation dummy variables: | ||||
|
Installed in 2005 |
(Yes = 1) |
- 0.0131 |
- 0.18 | |
|
Installed within last 10 years |
(Yes = 1) |
0.0128 |
0.31 | |
|
Installed prior to 1990 |
(Yes = 1) |
- 0.0106 |
- 0.04 | |
|
Log Likelihood Value (L1) = - 2906.1413 |
R2 = 0.09 |
Corn field observations (weighted) with: | ||
|
# of corn farms surveyed c = 380 [for 39 million planted corn acres] |
only infield |
conservation structures = 25.9 % | ||
|
Conservation program participants = 15 % |
only perimeter conservation structures |
= 9.0 % | ||
|
Conservation program non-participants = 85 % |
both infield |
and perimeter structures = |
4.1 % | |
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).
c Surveyed States for the 2005 Ceap-Arms for corn included IN, IA, IL, and NE.
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.
28
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