MODELING SEEDLING JOHNSONGRASS (SORGHUM-HALEPENSE) EMERGENCE AS INFLUENCED BY TEMPERATURE AND BURIAL DEPTH

Research was conducted to formulate a seedling johnsongrass emergence model as influenced by temperature and burial depth using the poikilot herm rate equation. A series of constant-temperature growth chamber ex periments with johnsongrass seed buried at various depths in fritted c lay was conducted to develop a temperature/ burial emergence database. The poikilotherm rate equation was fit to the emergence data from bur ial depths of 0 to 2.5 cm at constant temperatures between 20 and 44 C . These data were then combined to formulate a single poikilotherm rat e equation to model the emergence of seedling johnsongrass from 0 and 2.5 cm deep and 20 to 44 C. This combined model was validated against two independent emergence data sets with good results.