Foliar Top Dressing as a Way to Increase Plum Productivity Potential in Arid Conditions of the Northern Caspian Sea

The study investigated the impact of foliar top dressings on the yield and quality of home-grown plums in the arid conditions of the Astrakhan region. It was shown that the Great Blue variety on the BBAA-1 rootstock demonstrated a statistically based increase in productivity with the joint application of Aquarin, Ultremag Boron and Ultremag Calcium drugs, resulting in an increase in fruit yields of 1.1 tons per hectare compared to the control group. The variant with the use of Ultremag Boron and Ultremag Calcium fertilizers also showed an increase in plum yields of 0.8 tons per hectare. On the Eureka-99 rootstock, there was a statistically significant increase in yield caused by the interaction of Ultremag Boron and Ultremag Calcium agents, which accounted for 0.7 tons per hectare compared to the control group. An additional gain of 0.4 tons per hectare was reached in the Aquarin variant. On the BBAA-1 rootstock, the Great Blue variety stood out, showing maximum productivity. The average yield of this variety in all studied feeding variants was 5.8 tons per hectare. These figures slightly exceeded the yield of the Zainap variety, which was 5.7 tons per hectare. Despite being minor, this difference was statistically significant, indicating the superiority of the Great Blue variety on this rootstock under experimental conditions. It should be noted that the Great Blue variety had an average fruit weight of 53.8 grams, surpassing the control by 3.4 grams. The Zainap variety was characterized by an average fruit weight of 47.2 grams, which exceeded the control by 4.1 grams.