Study of effects of concentration and time of chemical thinning on improve the quality and quantity characteristics of nectarine "Shabrang"

In most fruit trees, despite the fact that all the flowers are not converted to fruit, the amount of production is more than the tree's capacity, which reduces the quality of the crop and reduces the yield of the tree. While in many fruit trees, the conversion of 5 to 15 percent of the flowers into fruits leads to economic production. The size and quality of the fruit produced should be consistent with market conditions. The goal of horticultural Science is to achieve the desirable annual yield and produce throughout the life of the garden. This research was carried out to investigate the effect of a few mineral thinners and a biological regulator on the quantitative and qualitative characteristics of the nectarine "Shabrang" and its comparison with hand-thinning of flowers and fruits. The experiment was conducted in a commercial garden in Semirom in 2012-2014 as a randomized complete block design with 15 treatments and 5 replications. The treatments consisted of lime-sulfur (6, 8% and twice the application of 6%), ammonium thiosulfate (20, 25 ml per liter and twice the application of 20 ml per liter), urea (4, 8% and twice 4%) and Apogee (300, 450 mg / L and twice the use 300 mg / L) at flowering stage (spraying in single stage treatments in 70-80% of flowering and two-stage treatments first in 30-40% and then in 70-80% flowering), flower hand- thinning in the 70-80% flowering stage and then four weeks after the flowering stage were applied to selected trees. The results showed that all treatments had a significant effect on the traits of nectarine "Shabrang" at 1% level. The treatments reduced the fruit set, so that in the hand-thinning treatment of flowers, twice ATS 20 ml per liter and twice lime sulfur 6% reduced the fruit set by 50%. Flower hand-thinning were the best treatment in terms of size (11.33 cm3) and weight (151.34 gr) and the highest yield was related to control (90.42 kg per tree) and the least yield was related to fruit hand-thinning treatment (64.04 kg per tree). The yield efficiency in control treatment (3.32 )fruit/trunk cross-section area) was higher than other treatments and its least amount was for the twice lime sulfur 6% (1.99 fruit/trunk cross-section area) and twice apogee 300 mg / lit (2.01 fruit/trunk cross-section area). In terms of qualitative traits, the highest total soluble solids were recorded in flower (17.49%) and fruit (16.53%) hand-thinning respectively, after which the best results were obtained in the twice treatments of thinning compounds. The highest amount of total acid was recorded in lime sulfur 6% (4.88 mg / 100 ml juice) and flower hand-thinning (4.26 mg / 100 ml juice) had the highest index of ripening among all treatments. The highest of leaf area was in twice ATS 20 ml/L (70.42 cm2) and twice urea 4% (69.18 cm2) and the least of leaf area was recorded in control (55.81 cm2). Fruit color as one of the qualitative indices in flower hand-thinning (4.74) was higher than other treatments and the least amount of fruit color was related to lime sulfate 6% treatment (3/38). Flower hand-thinning created a more regular thinning, larger and more colorful fruits and with higher sugar. The results also showed that the flower hand-thinning was better than the fruit hand-thinning. In general, two-step treatments of the compounds produced more suitable effects on the quantitative and qualitative traits of nectarine. However lime sulfur in 8% and twice using 6% caused some leaf burning.