Crop Load Management with Blossom Thinners in 'Redchief' Apple and Their Effects on Fruit Mineral Composition

The aim of this study was to determine the effect of ammonium thiosulphate (ATS) and potassium thiosulphate (KTS) on crop load, fruit quality and fruit mineral content of the eight-year-old 'Redchief'/M26 apple. Seven different treatments were performed in the study as ATS (1%, 2%, 3%), KTS (1%, 2%, 3%) and hand thinning (after June drop) except for unthinned control. Thinning treatments were carried out as single application in full bloom period. Hand thinning and 3% ATS treatments were the best practices to increase fruit quality (diameter, weight). The fruit set ratio among the applications varied between 13.20% (2% ATS) and 23.46% (1% ATS). Yield was lowest in 2% and 3% ATS. Thinning with ATS was found more effective compared to KTS. The lowest Fe, Cu and Zn elements were determined in 2% ATS application, and the difference between the applications in terms of other elements was found to be insignificant. Phytotoxic effect was not observed for any ATS or KTS doses. As a result, flower thinners can be used as an alternative to hand thinning to improve fruit quality in 'Redchief' variety.