Growth and persistence of perennial ryegrass lines with different tolerances to "pulling" during grazing

Abstract

The effects of ryegrass genotype, nitrogen (N) fertiliser and soil type on the level of plant losses by "pulling" during grazings were studied over 2 years. Plots of high-endophyte pipeline perennial ryegrass lines, coded A1 and A3, were established on the Dairying Research Corporation No. 2 Dairy in May 1994. Three plots of each line were sown on a Te Kowhai silt loam and three on a Te Rapa peaty silt loam soil. Half the area of each plot received nitrogen fertiliser (30 kg N/ha) after grazings from September 1995 to February 1996. Line A1 pulled more than did A3. Pulling was worse on the peat than on the silt loam, and was highest during summer-autumn 1994-95, which included a prolonged dry spell. N fertiliser increased post-flowering tillering, especially for A1. A1 had a higher leaf shear strength (6.21 vs 5.91 kg, SED = 0.087) and a wider leaf (3.40 vs 3.22 mm, SED = 0.054) than A3. It is argued that these morphological differences were important contributors to the observed pulling differences. Since A1 outyielded A3, we consider that plant losses owing to pulling did not constitute a serious loss of herbage dry matter. Keywords: dairying, leaf morphology, leaf shear strength, Lolium perenne, nitrogen fertiliser, persistence, pulling losses, tiller dynamics, tillering