Rick Graham1, Leigh Jenkins2, Kathi Hertel3, Rohan Brill4, Don McCaffery5, Neroli Graham1
1NSW DPI, Tamworth Agricultural Institute, 4 Marsden Park Road, Tamworth 2340, Australia, firstname.lastname@example.org
2NSW DPI, Trangie Agricultural Research Centre, Mitchell Highway, Trangie 2823, Australia
3NSW DPI, Australian Cotton Research Institute, Wee Waa Road, Narrabri 2390, Australia
4NSW DPI, Wagga Wagga Agricultural Institute, Pine Gully Road, Wagga Wagga 2650, Australia
5NSW DPI, 161 Kite Street, Orange 2800, Australia
Industry guidelines for windrowing of canola recommend that optimum cutting time occurs when 40–60% of seeds on the primary stem have changed colour from green to red, brown or black. Due to the increased prevalence of hybrid canola varieties, lower plant populations and perceived changes in plant architecture there has been increased discussion on how best to determine seed colour change (SCC) and therefore windrow timing. In 2016, experiments were conducted at three sites in northern NSW, to investigate the effect of SCC and windrow timing on seed size, oil concentration and seed yield. It was observed, from the partitioning of seed from pods on the primary stem and branches that SCC occurred later on branches compared to stems. Importantly, in the breakdown of yield components, it was found that seed from the primary stem only contributed 22% to 37% of seed yield. If SCC on the primary stem is solely relied upon for windrowing decisions overall seed development can be underestimated. This will negatively impact on seed size, oil concentration and yield potential. Furthermore, windrowing earlier than 40% SCC was shown to significantly reduce yield by up to 55% and oil concentration by 6.5%. Results clearly demonstrate the penalties associated with the current recommendation of early windrow timing at 40-60% SCC on the primary stem and the benefit of delayed windrow timings related to SCC, with yield optimised at the upper end of current industry guidelines. This study indicates that SCC should be measured on a whole plant basis not based solely on the primary stem, as branches contribute a large proportion of seed yield.