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



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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