Partial defoliation treatments to reduce carrot (Daucus carota L.) taproot splitting

Abstract

Carrot taproots with longitudinal tissue fractures (splits) are commonly deemed unsaleable. This study examined the use of partial leaf defoliation treatments to reduce the incidence of taproots that fracture during growth of the crop (growth splitting) and susceptibility to splitting during harvest (harvest splitting). Two leaf-trimming treatments, vertical and vertical plus horizontal leaf trimming, were compared with untreated control plots. The vertical plus horizontal trimming was the most effective treatment at reducing both harvest and growth splitting. Harvest splitting was significantly reduced by partial leaf defoliation the day prior to commercial harvest. The effectiveness of the treatments declined with time from treatment application. Growth splitting occurred mainly in the weeks prior to commercial harvest and the application of partial defoliation treatments during that period significantly reduced their incidence in crops predisposed to the disorder. A positive correlation between taproot splitting susceptibility and growth splitting was also identified, supporting previous assumptions that both harvest and growth splitting were induced by the same underlying mechanism. The leaf trimming treatments did not preclude mechanical harvesting.