|
Table 3. Integrated Alfalfa Management Regression Results, Model B, 1983 to 1987 ____________________________Estimated Coefficient3________________________ | ||||||||
|
Independent |
Herbicide |
Insecticide |
1983 |
1984 |
1985 |
1986 |
1987 |
1983-87 |
|
— |
- — ($/Acre) |
— | ||||||
|
Intercept |
462.73*** |
593.28*** |
586.52*** |
219.19"* |
105.74"* |
1963.99*" | ||
|
(39.12) |
(32.29) |
(32.39) |
(19.31) |
(7.19) |
(48.51) | |||
|
Cultivar: | ||||||||
|
WL318 |
2.33 |
27.92" |
115.03*** |
150.48"* |
145.52"* |
447.42*** | ||
|
(30) |
(2.32) |
(9.71) |
(20.24) |
(15.11) |
(16.88) | |||
|
Arc |
21.04" |
50.99*** |
109.60*** |
129.60"* |
94.12*" |
412.1Γ** | ||
|
(2.72) |
(4.24) |
(9.25) |
(17.44) |
(9.77) |
(15.55) | |||
|
OKO8 |
Base |
Base |
Base |
Base |
Base |
Base | ||
|
Fall |
No |
No |
65.83*** |
34.80 |
20.91 |
26.98* |
-4.45 |
44.65 |
|
Cut |
(4.25) |
(1.45) |
(.88) |
(1.81) |
(∙23) |
(.84) | ||
|
Yes |
No |
42.09** |
8.63 |
-7.96 |
.27 |
39.12* |
76.35 | |
|
(2.72) |
(.36) |
(.34) |
(.02) |
(2.03) |
(1.44) | |||
|
No |
Yes |
48.43*** |
27.92 |
17.∞ |
61.24"* |
53.55" |
188.59"* | |
|
(3.13) |
(1-16) |
(.72) |
(4.12) |
(2.78) |
(3.56) | |||
|
Yes |
Yes |
34.53** |
4.59 |
-7.15 |
77.84*" |
117.77*** |
233.24*" | |
|
(2.23) |
(.19) |
(.30) |
(5.24) |
(6.11) |
(4.40) | |||
|
Winter |
No |
No |
37.37" |
68.26*** |
60.16" |
53.42"* |
24.69 |
214.76*" |
|
Grazed |
(2.41) |
(2.84) |
(2.54) |
(3.59) |
(128) |
(4.05) | ||
|
Yes |
No |
66.23*** |
42.76* |
17.40 |
93.21 *** |
101.58"* |
276.27*" | |
|
(4.28) |
(1.78) |
(.73) |
(6.27) |
(5.27) |
(5.21) | |||
|
No |
Yes |
61.38*** |
13.35 |
98.75*" |
109.13*** |
61.65"* |
302.31"* | |
|
(3.96) |
(.56) |
(4.17) |
(7.34) |
(3.20) |
(5.70) | |||
|
Yes |
Yes |
55.17*** |
25.63 |
64.89" |
142.86*** |
133.41"* |
379.33*" | |
|
(3.56) |
(1.07) |
(2.74) |
(9-61) |
(6.93) |
(7.16) | |||
|
Unhavested |
No |
No |
Base |
Base |
Base |
Base |
Base |
Base |
|
Yes |
No |
-1.08 |
-2.97 |
.00 |
34.53" |
47.21” |
77.70 | |
|
(.07) |
(12) |
(.00) |
(2.32) |
(2.45) |
(1.47) | |||
|
No |
Yes |
33.45“ |
27.25 |
33.32 |
91.86"* |
73.65*** |
259.27*" | |
|
(2.16) |
(1.13) |
(1.41) |
(6.18) |
(3.82) |
(4.89) | |||
|
Yes |
Yes |
17.13 |
9.98 |
-7.69 |
118.30"* |
110.08*** |
247.67*" | |
|
(111) |
(■41) |
(-32) |
(7.96) |
(5.71) |
(4.67) | |||
|
N |
36 |
36 |
36 |
36 |
36 |
36 | ||
R2_______________________________________.727________.607________,887________.972________.942________.954
aNumbers in parentheses are absolute values of calculated t-statistics; and *** = .01 ** = .05 and * = .10 significance
levels.
combined, WL318 had slightly higher adjusted
returns than Arc. Nearly the entire OK08 stand had
died by the end of the sixth growing season, suggest-
ing that the level of pest resistance in improved
cultivars could be important for increased stand
longevity.
ModeIB
Model B estimated the potential interaction be-
tween end-of-season harvest options and both insect
and weed controls, while holding cultivars constant
(Table 3). The base interaction variable was the
unharvested option with no herbicide and insecticide
treatments.
For each year and for the five-year period, nearly
all combinations of winter grazing, insecticide treat-
ments, and herbicide treatments increased adjusted
returns compared with the base variable (unhar-
vested with no pest control). Fall cutting did not
increase adjusted returns when insect and weed pests
were controlled. Results suggest alfalfa forage taken
from a fall cutting does not offset the additional
harvesting costs, nor does fall cutting contribute to
reduced pest populations and higher yields when
113