EFFECT OF FLOWER THINNING ON YIELD AND QUALITY OF ‘`STANLEY`’ PLUM (PRUNUS DOMESTICA L.)

Abstract

Plum is the most important fruit crop for cultivation in Serbia. However, a small amount of plum fruit is sold as fresh fruit due to its poor quality. In order to improve fruit quality and obtain regular and high yield chemical blossom thinning agents were applied. The experiment was conducted on seven-year-old plum trees of cultivar `Stanley` which were planted on distance 5x5 m. Ammonium thiosulphate and ethephon were applied in the next treatments: 1) ammonium thiosulphate 1.5% (ATS); 2) ethephon 0.015% (E); 3) ammonium thiosulphate 1.5% + ethephon 0.015% (ATS + E); 4) hand thinning (HT); 5) untreated control treatment (UTC). Chemical thinning treatments were performed once during the phase of full bloom, while hand thinning treatment was performed after the fall of unfertilized fruitlets at the end of May. Parameters analyzed were yield, fruit size, fruit weight, pit weight, fruit firmness, fruit shape index, soluble solids content, total acid content and the amount of harvested fruits per time unit. The obtained results have shown that ATS + E, ATS and HT treatments significantly reduced the number of fruits on the trees compared to the control treatment. However, yield per tree was reduced significantly only in the ATS + E treatment. Other treatments compensated for the smaller number of fruits per tree with a significantly larger fruit size. Since the fruit size was larger on treated trees, the amount of harvested fruits per time unit was significant compared to control treatment. There were no significant differences among the applied treatments in terms of fruit firmness, soluble solids and total acid content.