BASE GROWTH TEMPERATURE AND PHYLLOCHRON FOR KIKUYU GRASS (Cenchrus clandestinus; Poaceae)

Abstract

In order to estimate the base temperature (Bt) of growth through the appearance of leaves and calculate the phyllochron for kikuyu grass, three plots were established on three farms in the Provincia of Ubate (Cundinamarca, Colombia) located at different altitudes (2560, 2640, 3143 m. a. s. l.). Measurements were made in four cycles in a period of eight months. The Bt was estimated by the least coefficient of variation method using a second order regression model and the model obtained was validated by the cross-validation method. The Bt values for the first, second, third and fourth leaf were 4.02, 3.68, 3.93, and 3.62 ° C, respectively. For the appearance of the first leaf, the kikuyu required more thermal time (TT) (97.5 accumulated growing degree days (AGDD)) than for the second (74.2 AGDD), third (73.8 AGDD) and fourth leaf (76.0 AGDD) (p 0.05). There was a tendency to a greater number of days required to reach each leaf stage in the farm located at higher altitude and with lower mean temperature. The validation showed an adequate adjustment (r2 = 0.94) and a substantial concordance (CCC = 0.97) between the observed values and the predicted values for the estimated TT with the Bt value obtained for each leaf stage. The results of Bt for kikuyu grass obtained, will allow to make more precise predictions about the phyllochron and generate growth models close to reality.