Tillering in ‘Grasslands Nui’ perennial ryegrass swards 1. Effect of cutting treatments on tiller appearance and longevity, relationship between tiller age and weight, and herbage production

Abstract

An irrigated ‘Grasslands Nui’ perennial ryegrass (Lolium perenne L.) sward was mown during reproductive growth and subsequent vegetative summer growth using 6 cutting treatments. The treatments included combinations of stages of interruption of reproductive development and regrowth intervals. Tagged ryegrass tillers were used to measure tillering, tiller longevity, and tiller weight at different ages. Periods of rapid tillering in spring before culm elongation started, and after interruption of reproductive growth were observed. Interruption of reproductive development at inflorescence emergence increased tillering in the second period compared with other treatments. Later interruption of reproductive development reduced the number of pre-flowering tillers surviving into summer. Longevity of tillers tagged at the start of the experiment was greatest with early interruption of reproductive growth followed by infrequent cutting. Youngest tillers were smallest, and new tillers took 60–100 days after appearance to reach the same weight as old, established tillers tagged at the start of the experiment. There was evidence that the growth rate of established tillers declined with time. Herbage accumulation was greater with mowing at 95% light interception than with mowing every 3 weeks. Delaying mowing after 95% light interception increased dead herbage accumulation, but only increased ryegrass accumulation during reproduction growth. The age structure of tiller populations did not greatly affect herbage accumulation.