Winter oilseed rape: Effect of partial defoliation


Cereals & Oilseeds
Project code:
01 July 1991 - 30 June 1992
AHDB Cereals & Oilseeds.
Project leader:
J H Spink ADAS Rosemaund



About this project


This study was initiated to determine the physiological basis for yield response from winter oilseed rape caused by partial defoliation as observed by Dr Vaidyanathan of ADAS Cambridge in previous years.

Two existing field experiments were monitored - one at ADAS Boxworth (funded by MAFF Policy Division) and one at ADAS Rosemaund (funded by ADAS). Both were replicated randomised block designs. Defoliation was carried out at both sites during January 1991 using a reciprocating blade mower. The plots were sampled at growth stage 8.1- 8.5. The samples were used to assess total biomass production, harvest index, yield components and distribution within the canopy.

No yield responses were observed. However at ADAS Boxworth there was a significant increase in harvest index in response to defoliation. The increase in harvest index was due to a significant decrease (p < 0.05) in vegetative dry matter produced whilst seed production was maintained. Plant number and seed production from the terminal raceme were reduced, but increases in branch number and production from the lower branches resulted in no net change in seed production per unit area.