Variation in base temperatures for germination in warm season grasses

Recently efforts have been made to develop heat unit based growth models for warm season grass production in cool season environments. These models require the accurate determination of base temperatures. Variations in base temperatures for germination of four switchgrasses (Panicum virgatum L.), three big bluestem grasses (Andropogon gerardii Vitman), two indian grasses (Sorghastrum nutans L. Nash) and two prairie sandreeds (Calamovilfa longifolia (Hook) Scribn.) were determined. During the germination study seeds were allowed to germinate in Petri dishes at 4, 8, 12, 16 and 20°C. The germination rates were used in estimating base temperatures using regression techniques. There were variations, among and within species in germination. Estimates of base temperature for germination were 5.5 to 10.9, 7.3 to 8.7, 7.5 to 9.6 and 4.5 to 7.9 for switchgrass, big bluestem, indian grass and prairie sandreed. Absolute values in each case depended on whether linear or non-linear techniques were used. The results also indicated differences between base temperature estimates for germination.