Determining optimal seeding times for tall fescue using germination studies and spatial climate analysis

This paper describes a new approach for determining optimal seeding times using laboratory-based germination studies and spatial climate analysis, with tall fescue as the test species and China as the targeted application area. Since temperature is one of a number of influential environmental factors for germination and establishment of grass species, experiments were conducted to determine the effect of temperature on seed germination of tall fescue (Lolium arundinaceum (Schreb.) Darbysh. = Festuca arundinacea Schreb. var. arundinacea Schreb.) (cv. ‘Vegas’, cv. ‘Barlexas I’, and cv. ‘Barlexas II’). Seeds were placed on moistened filter paper and subjected to 36 regimes of constant and altering temperatures from 5 to 40 °C. Germination data from the 36 temperature profiles were used to construct quadratic response surfaces for estimated percent germination with confidence intervals for each cultivar tested. Seeds germinated over a wide range of temperature. Optimal germination, defined as not less than the maximum observed minus one-half of the confidence interval at the 0.05 level of probability, occurred at constant temperatures of 20 and 25 °C and the 20/25 °C regime (16/8 h). Fluctuating temperature did not increase seed germination. Highest germination for all three cultivars occurred along the constant temperature gradient diagonal. Response surface predictions were used to develop species-based rules. These rules, in conjunction with national grids of temperature data, were modeled and mapped to predict and illustrate optimum sowing times for tall fescue in China.