Andy M. Cranmer1, James P. Bordovsky1, Wyatte L. Harman2, Evelyn M. Steglich2, and Jimmy Williams2. (1) Texas AgriLife Research, 823 West US Hwy 70, Plainview, TX 79072, (2) Texas A&M University, Texas Agricultural Experiment Station, 720 E. Blackland Road, Temple, TX 76502
Abstract
Among other elements, the optimum
economic allocation of limited water resources depends on the crop(s) being
produced, the cropping system, irrigation capacity, and commodity price. The
computer model “CroPMan” was calibrated in an attempt to provide an irrigation
management tool for the Texas High Plains, particularly in areas of low
irrigation capacity. CroPMan is a production-risk management model developed
by scientists at the Blackland Research and Extension Center in Temple, TX and is the windows based application of the USDA-ARS's Environmental/Policy
Integrated Climate (EPIC) model. Field data from a cotton-sorghum cropping
system experiment conducted from 2001 to 2004 at the Texas Agricultural
Experiment Station at Halfway were used to calibrate the model. Biomass to
energy ratio (BER), harvest index, and growing degree units were systematically
adjusted during multiple simulations in an attempt to determine one set of
parameters for acceptable model calibration over a range of irrigation
treatments. These treatments were from dryland to 2.5 gpm/ac irrigation
capacity. The best set of crop parameters gave a high linear correlation of
actual to simulated lint yields indicated by a regression beta coefficient near
1.0. However, the coefficient of determination (r2) of 0.53 was low
possibly due to extreme weather and cotton lint yield variation from 2001 to
2004 and/or using only one set of calibration parameters when trying to
simulate a wide range of irrigation treatments.
