The first release of Phygrow (1.0) used formulas from Epic, Spur,and Creams for soil hydrology and plant growth modeling. Nine test plots at the Texas A&M Experement Station in College Station were clipped, and soil moisture samples were cored twice a quarter in 1993 for callibration purposes. Irrigated test plots of Little Bluestem were clipped 8 times a year for 3 years (91-93). Urs Kruter organized the collected data, and ran the Phygrow 1.0 simulations for the different sites (with appropriate soil parameters, and estimated maximum potential yield curves.)
Evaluation of the irrigated Little Bluestem plots showed that even on the same test site, with unlimited water, there were variations of rate of growth and peak standing crop that could not be modeled with a single "TRANCO" (transpiration coefficent, from Epic, that relates a crops rate of transpiration to that of alfalfa) and "CROPCO" (a similar coefficent from Epic for the rate of growth) value for all 3 years.
Some of the sites had co-dominant species with dissimilar growth forms. As the values for the plant community were site based, the model did poorly when trying to predict the total forage for the site.
The site moisture samples were sparse and not well correlated with rainfall incidents. As a result of this the model did not appear to match soil moistures well, even when site production was within 2 percent of the measured value.
The first release of Phygrow (1.0) was a Dos text based application with 3 high resolution graphics plots (Daily Forage Growth, Daily Cumulatice Forage Growth, Relative Transpiring Live Phytomass) and 4 reports (Hydrologic, Evapotranspiration, Soil Water Balance, and Forage Production.)