Timothy regrowth, tillering and leaf area dynamics following spring harvest at two growth stages

Abstract

Timothy is the most widely grown grass species in Scandinavia. It is more winter-hardy than ryegrasses, but less tolerant to frequent cutting. Its intolerance to frequent defoliation is not well understood. This has hampered efforts to optimise the cutting regime, and made it difficult to develop and test mechanistic models for growth. In the present study, in order to identify the key determinants of regrowth capacity, we quantified time courses after cutting of physiological and morphological processes in timothy swards. In three consecutive years, field experiments were carried out with cv. ‘Grindstad’, the most commonly grown timothy cultivar in Norway. The sward was first cut either at a silage stage (early heading) or at a hay stage (full heading to anthesis). The effects of cutting time on tillering and leaf area dynamics were measured. Early cutting increased the length of the lag-phase of the sigmoid regrowth curve by more than 1 week on average, but once the sward entered the period of rapid biomass accumulation, growth rate was similar in both cutting treatments. Early cutting reduced the number of surviving tillers in the sward, leading to a slower rate of leaf area recovery. A lower carbohydrate concentration in the sward at the early cutting date, observed in 2 years out of 3, may also have contributed to this effect. Cutting time did not affect the chronological order in which the different processes contributed to recovery from cutting. The data assembled in this research will be used for testing a previously developed mechanistic model of timothy growth.