Table 2. Integrated Alfalfa Management Regression Results Model A1983 to 1987
Estimated Coefficient9
Independent
|
Variables |
1983 |
1984 |
1985________ |
1986 |
1987 |
1983-87 |
|
— |
---------($/Acre) |
— | ||||
|
Intercept |
474.50“* |
612.32"* |
591.13*** |
228.28*** |
106.64*** |
2010.02*** |
|
(51.42) |
(46.72) |
(46.58) |
(27.93) |
(10.11) |
(70.07) | |
|
Harvest: | ||||||
|
Fall Cut |
35.34*“ |
10.42 |
-11.16 |
-33.08“* |
-6.24 |
-10.45 |
|
(4.14) |
(.86) |
(.95) |
(4.37) |
(.64) |
(.39) | |
|
Winter |
42.66*** |
28.94** |
53.89*** |
38.48*** |
22.60“ |
147.00*** |
|
Grazed |
(4.99) |
(2.38) |
(4.59) |
(5.09) |
(2.31) |
(5.54) |
|
Unharvested |
Base |
Base |
Base |
Base |
Base |
Base |
|
Herbicide: | ||||||
|
None |
Base |
Base |
Base |
Base |
Base |
Base |
|
Treated |
-5.40 |
-13.83 |
-21.47** |
29.72*** |
56.68*** |
46.83“ |
|
(.77) |
(1.40) |
(2.24) |
(4.81) |
(7.11) |
(2.16) | |
|
lns⅜et⅛i<⅛. | ||||||
|
None |
Base |
Base |
Base |
Base |
Base |
Base |
|
Treated |
6.61 |
-7.13 |
25.07** |
74.46*" |
56.99*** |
153.45"* |
|
(.95) |
(.72) |
(2.61) |
(12.05) |
(7.15) |
(7.08) | |
|
SnJiiyar; | ||||||
|
WL318 |
2.33 |
27.92“ |
115.03*** |
150.48*** |
145.52*** |
447.42*** |
|
(.27) |
(2.30) |
(9.79) |
(19.89) |
(14.90 |
(16.85) | |
|
Arc |
21.04“ |
50.99*** |
109.60*** |
129.60"* |
94.12“* |
412.11*** |
|
(2.46) |
(4.20) |
(9.33) |
(17.13) |
(9.64) |
(15.52) | |
|
OKO8______ |
Base |
Base |
Base________ |
Base_____ |
Base |
Base |
|
N |
36 |
36 |
36 |
36 |
36 |
36 |
|
R2 |
.563 |
.473 |
.853 |
.961 |
.921 |
.936 |
aNumbers in parentheses are absolute values of calculated t-statistics; and *** = .01, ** = .05, and * = . 10 significance
levels.
and higher quality alfalfa, which could be marketed
at a higher price, enhanced adjusted returns.
Removal of fall growth by late-fall harvesting was
not cost-effective, i.e. returns from small yields did
not offset harvest costs.
Weed Control
Applying herbicides in 1983 through 1985
reduced adjusted returns, though not significantly,
with the exception of 1985 returns. Weed inter-
ference was not serious enough in these early years
of the stand to justify economically the application
of herbicides. However, herbicide applications in-
creased adjusted returns in 1986 and 1987, as well
as for the five years combined. These results were
expected, i.e., increasing returns to weed control
with increasing age of the alfalfa stand and decreas-
ing competitive ability of alfalfa plants as the stand
declined. Decreasing alfalfa plant populations in
older stands provided greater opportunities for
weeds to compete for light and nutrients.
Insect Control
Returns resulting from insecticide applications
also increased as the alfalfa stand aged. However,
the greatest difference in returns was likely due to
relatively low population levels for alfalfa weevils
in 1983 and 1984 in comparison with later years of
the study (Dowdy). Potential savings through
reduced use of insecticide are dependent on insect
infestation level (i.e. damage potential) regardless of
alfalfa stand age.
Cultivar Selection
Both improved alfalfa cultivars provided in-
creased returns relative to OK08 for the five-year
period. Arc resulted in significantly higher adjusted
returns in all years except 1983. For the five years
112