RESPONSE OF CREEPING BLUESTEM TO VARYING MONTH OF BURN AND SOIL-WATERCONDITIONS

Research was designed to determine if Schizachyrium scoparium var. pol ycladus responses vary with month of burn and soil water conditions du ring fire. Bluestem was grown in tanks with a 2 x 2 x 3 factorial of m onth (June or January), soil water (saturated or dry), and defoliation treatments (burn, clip, or none). Tiller density, rhizome mass, and t otal nonstructural carbohydrates were lower (P<0.05) during the 50 day s after burning in June when dry soil (25mm depth) reached 90 degrees C and remained about 50 degrees C for 68 minutes postburn. Reproductiv e tiller density 94 days after June 1987 burn was not affected by wate r, but was lower in burn vs. other defoliation treatments. No treatmen t in January 1988 affected tiller density or rhizome mass in a 50 day postburn period. In September 1988, there were no effects due to month or water, but vegetative tiller density was lower in burn and clip vs . no defoliation, total tiller density was different among all treatme nts, and reproductive:vegetative tiller density (R:V) ratio was higher in burn vs. clip and no defoliation. In Florida, fire on hot, dry san dy soils in June may have short term negative effects, and fire at eit her season or soil water level may reduce total tiller density and inc rease R:V ratio in creeping bluestem for up to 476 days postburn.