Effects of Degree and Time of Defoliation on Yield and Related Attributes of Safflower1

Abstract

From 1960–1962 four agronomically diverse safflower entries were grown in replicated field plots at Logan, Utah. These entries were partially or totally hand defoliated at seven stages of growth. Removal of all leaves — when averaged over dates, entries, and years — reduced yield by 23.0%, weight per 100 seeds by 7.7%, test weight by 2.6%, hull percentage by 6.0%, and increased oil by 6.9% in relation to the check plot. The increase in oil percentage was negatively correlated with the decrease in hull percentage (r= —0.86). Removal of leaves from the top half of the plant had a similar but slighter effect. Removal of branches from the bottom half of the plant reduced yield at the later stages of plant development. Removal of leaves from the bottom half of the plant regardless of growth stage did not affect the attributes measured. There was a differential response of safflower entries to the severe defoliation treatments (removal of all leaves or removal of leaves from the top half of the plant).