Miss Fiona Anderson1, Dr Mariana Andreucci1, Professor Timothy Clough1, Professor Derrick Moot1
1Faculty of Agriculture & Life Sciences, Lincoln University, Lincoln, New Zealand
Biography:
Fiona has a Bachelor of Agricultural Science with Honours in nitrous oxide emissions from soils. She is currently a PhD candidate at Lincoln University studying white clover seed crop production and modelling.
Abstract:
White clover (Trifolium repens L.) seed production management aims to enhance light levels at the base of the canopy to increase flower population and survival. This is usually achieved by using a wide row spacing and defoliating herbage material. This experiment observed flowering of a conventionally established white clover commercial seed crop grown in Canterbury, New Zealand. Two treatments were implemented; a non-sprayed control, and a chemical defoliation treatment of 1.5 L/ha of Argosy® (25 g/L diflufenican and 250 g/L bromoxynil) and 1.5 L/ha of Relay® (680g/L 2,4-D), applied on 7 September 2022. Marked plants were measured twice weekly for flower development. The thermal time taken between each flowering stage was calculated using air temperature. There was no difference between treatments in the thermal time accumulation to peak bud emergence (2580°Cd (± 15), P=0.87) or peak flowering (2800°Cd (± 17), P=0.94). Plants had on average 18 live flowers (± 3) at harvest (P=0.76), 70% (± 3) of which were mature (P=0.97). Both treatments (P=0.42) senesced 20% (± 4) of flowers before harvest. Of these, 79% (± 6) were immature flowers in the defoliated plants compared with 46% (± 7) in the control (P=0.047). Defoliation in early spring did not result in any yield benefit. There was no difference between treatments in the number of ripe seeds per flower or thousand seed weight. The recovery period from defoliation may have limited the supply of resources to immature flowers, resulting in their loss. Without any increase in seed yield, the cost of chemicals required for defoliation is difficult to justify.