Structural Conservation Practices in U.S. Corn Production: Evidence on Environmental Stewardship by Program Participants and Non-Participants



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:
no conservation structures = 61.0 %

# 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.

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