Winter growth stimulation by gibberellin in differentially grazed pastures of Phalaris tuberosa

Abstract

The effect of gibberellic acid sprays on' the winter growth of two pastures of Phalaris tuberosa L. differentially grazed for a period of four years prior to the investigation, was studied. The previously lightly grazed pasture had initially approximately ten times as much soluble carbohydrate in the underground parts as the heavily grazed pasture. Both pastures responded in the same way with an initial increase in yield with gibberelin but no subsequent increase. However, regrowth from cut areas treated with gibberellin was significantly greater on the lightly grazed pasture. Since the stubble remaining after cutting was very low in chlorophyll, it is suggested that the differential regrowth might be due to the higher levels of stored carbohydrate in the lightly grazed pasture.