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:
Chemical defoliation of white clover (Trifolium repens L.) seed crop leaf canopies is one management technique used to increase flower population and survival. It is intended to increase light intensity at the base of the canopy where flower buds are emerging. This experiment measured canopy development of a conventionally established white clover 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 monitored for development with twice-weekly leaf counts until seed harvest. There was no difference between treatments in the rate of leaf accumulation between treatment and flower bud emergence (0.164 leaves/°Cd (± 0.013)) or senescence during seed fill until harvest (-0.045 leaves/°Cd (±0.011)). However, during flowering, the defoliated plots continued to build their canopy (0.02 leaves/°Cd), whereas control plots decreased in leaf number (-0.017 leaves/°Cd (±0.025)), P=0.05). The defoliation treatment gave no increase in flower population (mean 1213 flowers/m2 (± 74), P=0.619) or seed yield (mean 126 g/m2 (± 4), P=0.565). Defoliation in early spring did not result in any seed yield increase. The defoliated plants appeared to prioritise leaf canopy recovery ahead of flowering. The costs of chemical and its application were not recovered in saleable product, which would reduce crop profitability.