Dependence of Photosynthetic Activity and Yield of Plum Varieties on the Use of Non-Root Fertilizing in the Arid Zone of the Northern Caspian Sea

In 2021–2023, the effect of non-root fertilizer application on photosynthetic activity and yield of plum varieties in the arid zone of the Northern Caspian Sea was studied. It was found that the leaf surface area on average during the growing season in the variant of the combined use of Aquarin + Ultramag boron + + Ultramag calcium exceeded the control by 50%. An increase in photosynthetic potential was noted when treated with Aquarin and Master fertilizers by 25.0 and 42%, respectively. The maximum increase in yield (12.8 t/ha) was obtained during leaf processing in the variant of the combined use of Aquarin + + Ultramag boron + Ultramag calcium preparations, which exceeded the control by 34.7%. It should be noted that the best responsiveness to non-root top dressing was distinguished by the Gigantic variety, whose yield was 13.2 t/ha, which was 39% more than the control.