The Soil and Water Assessment Tool, or
SWAT model, is a small watershed to river basin-scale model to simulate the
quality and quantity of surface and ground water and predict the environmental
impact of land use, land management practices, and climate change. SWAT is
widely used in assessing soil erosion prevention and control, non-point source
pollution control and regional management in watersheds. It has been
successfully used to predict alterations in streamflow, evapotranspiration and
soil water; however, it is not clear how effective or accurate SWAT is at
predicting crop growth.
Previous research
suggests that while the hydrologic balance in each watershed is accurately
simulated with SWAT, the SWAT model over or under predicts crop yield relative
to fertilizer inputs. The SWAT model now has three alternative N simulation
options: 1) SWAT model with an added flush of N (SWAT-flush); 2) N routines
derived from the CENTURY model (SWAT-C); and 3) a one-pool C and N model
(SWAT-One). The objective of this study was to evaluate the performance of
SWAT-flush, SWAT-C, and SWAT-One as they affect wheat yield prediction.
Simulated yields
were compared to wheat yields in a 28-year fertilizer/wheat yield study in
Lahoma, OK. Simulated yields were correlated with actual 28-year mean yield;
however, none of the available N cycling models predicted yearly yields. SWAT-C
simulated average yields were closer than other N sub-models to average actual
yield. Annually there was a stronger correlation between SWAT-flush and actual
yields than the other submodels. However, none of the N-cycling routines were
able to accurately predict annual variability in yield at any fertilizer rate.
In conclusion, this
research indicates that SWAT-C or SWAT-flush provides the most accurate
prediction of average wheat yield and can be used for wheat cropland yield
assessment. Further research is
needed to determine the effectiveness of SWAT-C and SWAT-flush in determining
average and annual yield in various farming regions and with numerous agronomic
crops.
Article by Elizabeth Brooke Haney, et
al, from USA.
Full access: http://suo.im/4pc5Pt
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