It was assessed the evolution of tillering, forage biomass, leaf area index (LAI), interception of photosynthetically active radiation (IPAR), efficiency of radiation use (ERU) in Panicum maximum "cv" Mombaça during the regrowth period of the grass, in the Summer and Autumn seasons. Similarly, grass growth indices were assessed: net assimilation rate (NAR), leaf area ratio (LAR) and relative growth rate (RGR). All these variables were estimated from field observations taken on the 7th, 14th, 21st, 28th, 35th, 42nd and 49th days of the regrowth period (treatments), in the Summer and Autumn seasons. The experimental design was completely randomized with four replications. One area of 1,200m² was used in each season; 28 and 24 sampling points were chosen in the Summer and the Autunm seasons, respectively, for their similarity regarding canopy height and soil cover condition and randomly assigned to the treatments. The grass tillering was more intense in the first regrowth week and declined afterwards to reach negligible values from the fourth week on. Interception of the photosynthetically active radiation evolved in an asymptotic manner reaching highest value of 96%, without difference between Summer and Autumn. Leaf area index figures showed the same pattern in the Summer and Autumn, reaching the values of 8 and 4, respectively; on the other hand, forage biomass responded quadractically to the duration of the regrowth period. Radiation use efficiency reached the values of 1.76 and 0.54gDM/MJ in Summer and Autumn, respectively. RGR and NAR figures decreased in an asymptotic pattern in both seasons, with higher values in the Summer, while LAR figures increased initially in the first four weeks reaching values of 0.017 and 0.013m²/g towards the 28th day of the regrowth period, respectively in Autumn and Summer.
interception of photosynthetically active radiation; leaf area index; leaf area ratio; rate of net assimilation; rate of relative growth; tillering
