Growth analysis and regrowth potential of three cool season grasses in spring

Abstract

The analysis of the accumulating canopies of Dactvlis glornerata L., Festuca arundinacea Schreb., and Bromus inermis L. along with the regrowth potential under field conditions and under controlled environments (in light at three temperature regimes and in the dark at one temperature) for different stages of growth were studied. The analysis of the accumulating canopies showed that there was no difference among the grasses in CGR when averaging all weekly samplings. The non-structural carbohydrates in the stubble generally showed an inverse relation with the CGR. There were differences in total LAI among grasses when averaging the weekly cuts. The regrowth in the field after harvesting at different dates was found to be influenced by variation in temperature, LAI and soluble carbohydrates in the stubble, and change in the morphology of the accumulating canopies in late spring. The regrowths in 35/29 C, 26/21 C, and 18/31 C temperature were influenced by the LAI and carbohydrate content in the stubble, and by the change in the morphology of the grasses in late spring except in 35/29 C temperature regime the LAI in the stubble had only very little influence. The high temperature regime produced the least and the medium temperature regime the highest weight per tiller. The percent tiller regrowth was adversely affected by high temperature regime. In dark growth only a weak relationship existed between the soluble carbohydrates in the stubble and weight per tiller in regrowth. Better regrowth was observed when the accumulating canopies were cut prior to jointing than when cut later in all grasses. This suggests that utilizing forages prior to jointing will produce a good aftermath growth and persistence. The response of stubble LAI in cool environment to produce heavier tillers shows that frequent grazing can be made in early spring to obtain much needed forage in that period. This will keep the canopy short with high LAI in the stubble. The response in high temperature regime shows that stubble LAI had only little effect in producing heavier tillers in regrowth. Hence harvesting cool season forages at a time of low carbohydrate content, even with high LAI values in the stubble, is harmful to rapid regrowth when the temperature environments are high.