Impact of Intensity and Season of Grazing on Carbohydrate Reserves of Perennial Ryegrass

Abstract

Carbohydrate reserves of perennial ryegrass declined during winter and early spring and began replenishment during seed formation. The primary reserve accumulation in roots occurred during fall growth, while crowns replenished about half of their reserves from seed formation to fall and the balance during fall. Total nonstructural carbohydrate (TNC) reserves in roots were highest following a relatively wet year when compared to an average year but carbohydrate reserves were found to be more concentrated in the average year. Biomass of storage organs had a greater effect than concentration of carbohydrates on TNC reserves. Complete protection of perennial ryegrass from grazing did not induce greater accumulation of carbohydrate reserves when compared to any season of grazing treatment and they were sometimes significantly lower than for grazed treatments. No advantage from deferment of grazing in spring, summer, or fall could be determined based on carbohydrate reserves as along as stocking intensity did not exceed one ewe per 650 kg of herbage production per year. At stocking rates above this, deferment during part of the growing season should be beneficial.