Efecto de diferentes compensadores de frío aplicados en manzanos en el sur de Uruguay

One of the factors influencing fruit quality and yields of apple orchards in Uruguay is the insufficient winter cold for the plant to adequately break endodormancy. The objective of this work was to determine the response of apple trees (Malus domestica B.) “Maxi Gala” and “Red Chief” to the application of cold compensating products, to promote the exit of endodormancy state. The treatments consisted in the application of emulsifiable mineral oil (4%), emulsifiable mineral oil (2%) with hydrogenated cyanamide (1%) and calcium polysulfide (6%) at two times. In the “Maxi Gala”, applications were made to 696 and 932 UF for the first and second moment, respectively, and in Red Chief at 757 and 993 UF. The applications dates of the cold compensators were August 6 and 31, with a water consumption of 850 l/ha in Maxi Gala and 1450 l/ha in Red Chief. 50% leaf fall in Maxi Gala was on June 8^th and in Red Chief on May 29^th. Budbreak responses were evaluated from September 22 to October 12. Referring to “Maxi Gala”, there were no significant differences in the time of application of cold compensators. The chilling requirements in this cultivar were already covered at the time of the first application of compensators. However, “Red Chief” did not complete its chilling requirements at the time of the applications and budbreak percentages improved with the application of compensators at the later date. The percentage of buds sprouted in this cultivar increased from 70,38 to 79,74 and from 71,32 to 79,85 in the evaluations of October 6 and 12 respectively. Considering both cultivars, no differences were observed in final budbreak according to the active ingredients used. There were also no differences in the product-timing interaction. In regard to bud break according to their structure, there were significant differences for both varieties studied, with 10% more buds break on one-year shoots than on spur structures.