Evaluation of subterranean clover cultivars for New Zealand dryland pastures

Abstract

Subterranean clover cultivars available in New Zealand have been currently and historically reliant on the Australian market and research. Currently there is very little information available which is related to cultivars performance under a cooler New Zealand climate. This study evaluated 11 subterranean clover cultivars and their performance in mixed swards. On average cultivars throughout this experiment performed poorly in their germination ability, under lab conditions (15°C). Large proportions of these seeds remained hard with the earliest flowering culivar ‘Monti’ consisting of 67% hard seed, while a later flowering cultivar ‘Napier’ consisted of 33% hard. Along with hardseededness a small proportion of seed throughout all cultivars were unable to germinate and defined as ‘dead’, suggesting issues during the development stage of the seeds. ‘Narrikup’ a mid-flowering cultivar, outperformed all other cultivars during the emergence stage, with 293 seedlings/m2 on the 5th a March and consisted of a high potential to bury its burrs (7/9) (Nichols et al. 2013). ‘Narrikup’ showed the ability to regenerate and survive throughout the 2015 season, still consisting of a 15% sub clover cover by the end of September. The cultivar ‘Antas’ showed huge potential in its first year with the highest overall yield in September 2014 (760 kgDM/ha) and highest sub clover content in November 2014 (2710 kgDM/ha). However in the following year ‘Antas’ performance dropped drastically, with its inability to regenerate. This was attributed to its subspecies family brachycalycinum, unlike subterraneum and yanninicum, brachycalycinum cannot actively burr its burrs and is therefore not protected from the aerial environment, effecting its seed potential to develop seed (Francis et al. 1972; Collins et al. 1976). Both ‘Narrikup’ and ‘Antas’ presents how essential the burial process can be under the cooler New Zealand climate. Older cultivars including both ‘Mt Barker’ and ‘Woogenellup’ (late flowering cultivars) began poorly in their ability to regenerate reaching only 47 seedlings/m2 and 78 seedlings/m2 respectively by the 5th of March. By the final visual score in spring however these cultivar had recovered with ‘Woogenellup’ consisting of around 17% sub clover cover and ‘Mt Barker’ roughly 10%. ‘Denmark’ a later flowering cultivar (Nichols et al. 2013) also showed an increase in performance by the end of spring with 11% sub clover cover. Currently studies throughout New Zealand have claimed late flowering cultivars will out compete both mid to late flowering cultivars (Chapman 1992; Collins et al. 1976; Smetham and Ying 1991; Sheath and Richardson 1983), under this experiment however this was not an obvious trend.