The effects of post-harvest management on the seed yield of a tall fescue (Festuca arundinacea) seed crop : A thesis submitted in partial fulfilment of the requirements for the degree of Master of Science at Lincoln University

Abstract

Tall fescue seed crops require post-harvest residue management to prepare the crop for the following season. Previously farmers relied on methods such as burning residue, but due to a change in social license around air quality and public safety concerns, there has been a reduction in this management practice. The objective of this research was to investigate non-thermal post-harvest residue management practices required to maximise seed yield for a tall fescue seed crop with full post-harvest straw load retained. Two experiments were conducted on a crop of tall fescue (cv. Volupta) entering its third year of seed production. Trial 1 showed that in the absence of grazing, the most effective method of residue management was to leave the crop stubble at a post-harvest height of 14 cm, and to mow the crop either under a frequent (monthly) or lax (once at closing) regime. The frequency of the mowing treatments had no effect on seed yield. These treatments produced an average seed yield of 435 kg/ha. Trial 2 showed that under grazing, seed yields were highest in plots left with 14 cm of stubble after harvest, with an average seed yield of 327 kg/ha. Spring nitrogen applications in the grazed trial had no effect on final seed yield. The lower seed yield in the cutting to 7 cm and nil cut treatments, was a result of a lower number of fertile tillers. For the former, cutting removed all of the leaf tissue, while in the latter, plants were shaded. Both reduced the leaf surface area for photosynthesis and therefore the ability to support tiller initiation and growth. This in turn reduced the final seed yield of the crop and showed the most effective management practice is to leave the crop at 14 cm and mow frequently or laxly.