insecticide and herbicide treatments are employed.
Insect and weed control by chemical treatment in-
creased adjusted returns within each harvest option
and is more important than the harvest option from
an interaction viewpoint
Summaryand conclusions
This study was designed to analyze economic im-
plications of alfalfa production practices, focusing
on cultivar selection, insect and weed control alter-
natives, and end-of-season harvest options. Binary
variable regression was applied to mean adjusted
returns per acre for years 2 through 6 of an ex-
perimental research alfalfa stand, and for the 5-year
period combined.
Results indicated there were significantly higher
economic returns resulting from improved alfalfa
cultivars which have some resistance to insects and
plant pathogens. Selection of an improved alfalfa
cultivar (either WL318 or Arc) consistently in-
creased adjusted returns compared with OK08,
which had no selection for pest resistance.
Winter grazing of fall alfalfa growth increased
returns to the alfalfa enterprise relative to other
end-of-season harvest alternatives, and without con-
sidering any benefit from grazed alfalfa in the live-
stock enterprise. Winter grazing contributed to
reduced insect and weed pest populations. Had a
value been assumed for alfalfa forage removed by
grazing (i.e. animal weight gain) the comparative
advantage from winter grazing would have been
increased further. Late-fall harvesting, while poten-
tially reducing population densities of insect pests
and weeds, did not increase adjusted returns because
harvest costs exceeded the revenue generated from
small yields of the late-fall cutting.
The combined use of insecticides and herbicides
produced the highest adjusted returns within cultivar
and harvest alternatives. Insect control alone in-
creased adjusted returns more than weed control
alone. Use of herbicides was not economical in the
early years of the alfalfa stand, since stands were
competitive with weeds. However, as the alfalfa
stand aged and thinned, interference by weeds in-
creased and the use of herbicides became cost-effec-
tive.
Insecticides and herbicides were applied in some
cases as part of the research design, regardless of
whether economic threshold population levels of
insects and weeds were reached. Therefore, treat-
ment of both insect and weed pests only when
populations reached economic threshold levels
would have further increased adjusted returns in this
study.
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