Water-soluble carbohydrate and nitrogen concentrations after defoliation in perennial ryegrasses (Lolium perenne L.) in spring

Abstract

It is well documented that water-soluble carbohydrates (WSC) and nitrogen (N) are sources to start growth after defoliation, but there is little information about the concentration changes postdefoliation when normal and high sugar cultivars (CVS) are used under field conditions. The objective of this study was to evaluate, every three days, the WSC and N concentration change in stubble and regrowth of four perennial ryegrasses (AberAvon, AberDart AR1, Arrow AR1 and Jumbo). There was no interaction between CVS and day after defoliation on the WSC or N concentration for each tissue (p > 0.05). There were effects of time after defoliation in both tissues (p < 0.05). The WSC concentration on the stubble declined until day nine (148.9 g kg-1 DM), reaching initial levels on day 18 after defoliation (198.8 g kg-1 DM). In the regrowth the values changed from 114.4 to 159.5 g kg-1 DM, respectively. The N concentration in the stubble and regrowth increased up to day 9 (26.4 g kg-1 DM) and day 12 (38.2 g kg-1 DM), respectively. Later, there was a steady decline until the end of the regrowth period with N concentrations of 20.4 and 27.8 g kg-1 DM for stubble and regrowth, respectively. The results indicate that the use of CVS marketed as high sugar do not bestow any advantage in terms of higher concentrations of WSC in different tissues after defoliation.