Effect of Indol Acetic Acid and Ammonium Thiosulphate Spray on Thinning Percentage, Fruit Yield, and Quality of Payizeh Znouz Apple

‘Payizeh Znouz’ apple trees have a high capacity for fruit bearing, leading to a small fruit size. Thinning of flowers and fruits can considerably increase the quality of the fruits in prunus trees by improving the size, color, and other features related to the quality of the fruit. An experiment was conducted to study the effects of ammonium thiosulphate (0.25%, 1% and 1.75%) at different stages of blooming (pre blooming, 30% blooming and 90% blooming) and indol acetic acid (15, 30, 45 ppm), at fruitlet size (7-21mm) on thinning percentage, fruit yield and quality of 'Payizeh Znouz' apple in Znouz zone of Marand city in 1390. Trees with relatively the same size, growth and strength were selected. The treatments were given separately on each tree. The experiment was arranged in a randomized complete block design with 13 treatments and 3 replications. Some of measured characteristics showed that there was a significant difference between the treatments. The highest thinning percentage and fruit weight were in treatments of ammonium thiosulphate and indol acetic acid when applied at high concentrations. The ammonium thiosulphate increased fruit diameter and indol acetic acid increased fruit length.