Effects of fertigation on tree performance and nutrient availability in apple orchards of Central Russia

The apple cultivars have different responsiveness to fertilizer applications and changes of root nutrient conditions. We studied the impact of soil fertigation on leaf nutrient status and yield in two apple orchards of cultivars ‘Lobo’ and ‘Spartan’ grafted on B9 with a tree density of 2000 tree ha^‑1 at a distance of 130 km from each other in Tambov and Lipetsk regions (Russia). The study was carried out in 2013, 2014 and 2015 in fertigated and non-fertigated plots and in which soil profiles at 2 m depth were studied. The data analysis underlined the effect of drip irrigation and fertigation on the profiles of dark gray forest and meadow chernozem soils. As a result of fertigation application on dark gray forest soil, we found a trend to eliminate the intensity of the podzolization process. The mechanism of this process suggests that organic matter, aluminum and iron ions are moved from the upper parts of profile into deeper soil layers. We found the occurrence of podzolization in the soil profile of the non-irrigated plot. These signs (whitish strip under top layer on soil profile) were not present in the irrigated site. Moreover, it was observed a decrease in the soil pH value. In each year of the trial, we determined the content of nitrogen (N), phosphorus (P) and potassium (K) in the soil immediately under the emitter. We sampled soil and leaves after the periods of greatest plant needs for nutrients (soil sampling for P-analysis – 26-30 May, after blossoming; N – 25-28 June, after shoot growth; K – 15-20 August, after fruit ripening). The soils nutrient distribution under the emitters did not have significant variations in the different types of soil. Leaf samples were also analyzed to determine N, P and K status. ‘Lobo’ leaves had higher content of N and P in all the years of research, and more K in 2013 and 2015 by fertigation in dark forest soil. ‘Spartan’ had better P and K leaf nutrient status by fertigation on meadow-chernozem. Fertigation significantly increased yield of ‘Lobo’ on dark gray forest soil, whereas fertigation raised ‘Spartan’ productivity in conditions of meadow-chernozem soil.