| |
Duck Creek Watershed, Texas
Economic and environmental impacts of
broiler industry expansion and phosphorus control BMPs were
simulated for Duck Creek watershed, a small watershed located
mostly in Robertson County, in southeast Texas. Modelers simulated
the impacts of various scenarios on ambient nutrient and sediment
concentrations and soil phosphorus with SWAT. The economic impact
of broiler industry expansion was estimated using the Impact
Planner (IMPLAN). Costs (or benefits) of BMP implementation
for representative pasture, hay, broiler operations, the broiler
integrator, and for the entire watershed were also estimated.
Environmental and economic impacts of 0X,
1X, 1.2X, 2X, 2.3X, and 6.1X expansion scenarios were calculated,
where 1X denotes the level of litter application estimated
for year 2000. For the greatest expansion scenario considered
(6.1X), Robertson County economic activity expands by five
percent, jobs in Robertson County increase by an estimated
seven percent, while simulated loads of soluble and organic
phosphorus in Duck Creek approximately double.
Simulation of BMP scenarios utilized the
6.1X expansion scenario (N rate) as the baseline reference
condition. BMP scenarios considered were double the P rate,
P rate, haul-off of cleanout litter, haul-off of all litter,
phytase addition to feed, and alum amendment of litter.
The BMP analysis indicates that substantial reductions in
watershed phosphorus loads can be accomplished by reducing
the rates or areas to which broiler litter is applied.
The P rate and double P rate scenarios are more cost-effective
than the haul-off scenarios, although absolute reductions
in ambient P levels are greater for the haul-off scenarios.
The phytase and alum BMPs are new technologies that have not
yet been widely adopted. Both of these technologies
produce net economic benefits in addition to reduced P loads,
and hence, are classic “win-win” solutions. The
complete haul-off and alum amendment scenarios produce reductions
in soluble P of similar magnitude. The complete haul-off
scenario, however, is estimated to cost $334,000, whereas
the alum amendment scenario produces estimated net economic
benefits of about $310,000.
The win-win nature of the phytase and alum
scenarios is an attractive feature for policy makers, integrators,
and broiler growers to consider when assessing strategies
to reduce phosphorus runoff from litter application areas.
Due to technical aspects of these practices, unilateral implementation
by growers of either practice is unlikely. To be effectively
utilized, phytase must be added to feed when it is milled
suggesting that any public action to increase the use of phytase
in broiler feed would need to be directed at feed mills, which
are often owned by integrators. Alum addition to litter at
phosphorus control rates is not cost-effective for growers.
Because integrators capture the majority of economic benefits
attributable to alum use whereas broiler growers sustain net
costs, it may be appropriate for poultry integrators and government
agencies to help cost share alum use at the phosphorus control
rate by growers.
|
|
