Agriculture Reference
In-Depth Information
if they are equipped and willing to harvest at
higher-than-optimal grain moisture and make
use of on-farm drying equipment. Whatever the
system used, the key to profi table and sustainable
management in modern production systems is to
anticipate the effect that a decision today will
have 6 months or even 6 years from now. All
components of wheat management are inter-
twined, and one factor is rarely changed without
having an intended or unintended infl uence on
another factor of production.
America, and Australia. In this system, wheat is
sown in early fall with the expectation that wheat
growth will be suffi cient to allow for grazing by
stocker cattle (
Bos taurus
L.) within 8-10 weeks.
Cattle remain on wheat pasture until the wheat
canopy reaches the fi rst-hollow-stem stage of
growth in late winter. First hollow stem occurs
just before jointing (approximately Feekes GS 5)
and is characterized by 1.5 cm of hollow stem
below the growing point (Redmon et al., 1996)
(see Color Plate 5). By diversifying the farming
enterprise between crop and livestock production
on the same acreage, the dual-purpose system
spreads risk, increases income, and increases
nutrient utilization effi ciency (Redmon et al.,
1995).
There are several reasons why the dual-purpose
wheat production system fi ts in some areas and
not others. First and foremost, many farmers and
ranchers in areas where the system is utilized are
experienced cattle producers who understand
stocker cattle management and marketing. Also
critical is that wheat fi elds seldom have snow
cover which would prevent grazing. Wet soil con-
ditions reduce cattle weight gain and increase
damage to the developing wheat crop, so it is also
benefi cial if the winter months are typically the
driest months of the year. Finally, many farmers
and ranchers that utilize the system are in a mono-
crop, continuous wheat production system so that
rotational summer crops do not delay wheat
sowing in the fall.
Dual-purpose wheat production requires
several modifi cations from normal wheat produc-
tion practices. Grazing restrictions for many of
the most popular wheat herbicides, for example,
prevent timely herbicide application in the fall
when weeds are small and most susceptible to
chemical control. Likewise, fall-applied, soil-
activated herbicides frequently have reduced effi -
cacy due to soil movement from cattle hooves.
For these reasons, dual-purpose wheat producers
often fi nd themselves applying herbicides late in
the spring to well-established weeds that are
hardened from grazing and winter damage. Weed
control is just one of many management practices
that must be modifi ed for successful dual-purpose
wheat production.
Limitations of the system
Although intensifi cation of wheat management
practices has been regarded as a large step forward
in areas such as the southeastern US (Snyder
2000), it has not been a universal success in all
areas. In areas where intensively managed crops
such as vegetables are already the dominant
system, few benefi ts have been observed to further
increases in nitrogen fertility or increased inputs
(Mohamed et al., 1990). In spring wheat produc-
tion areas, delaying the bulk of nitrogen applica-
tions until wheat jointing can result in insuffi cient
tillering and lower yields. Similarly, in areas with
less predictable rainfall patterns, such as the US
Great Plains, rainfall may not occur for several
weeks after nitrogen application. Thus, delaying
nitrogen applications until jointing can sometimes
result in excessive nitrogen losses due to volatil-
ization or the failure to move nitrogen into the
rooting zone in time to have full impact on wheat
yield. Again, the key to a systems approach is to
understand which factors are limiting and to
determine whether or not those factors are
controllable.
DUAL-PURPOSE WHEAT
Description of the system and area
of adaptation
The dual-purpose wheat production system is an
integrated crop-livestock system that is common
in some areas of the US, southern Europe, South
