The impact of the tree performance and water balance characteristics on nutritional status of apple trees

Accumulation of mineral nutrients in leaves is a major indicator of the nutrient status of perennial crops. It is often affected by a number of physiological and environmental factors complicating the nutrient status interpretation. Still, their mutual impact in field conditions has been rarely studied. This study aimed at characterizing the intensity of the parallel effects of crop load and the growth vigor of apple trees as internal factors and the effects of weather conditions and irrigation as external factors on the macro- and micronutrient contents in leaves of two apple cultivars. The evaluation was carried out with six -year -old 'Gala Brookfield' and 'Red Jonaprince' on M9 rootstock planted in field conditions. The study was designed to analyze the variability of nutrient leaf content of the apple trees using linear -mixed models and multiple linear models. For the nutrient content analyses, crop load, relative growth rate, water balance, and cultivar were used as fixed effects and the inter -annual variability was used as random effect. All the studied factors were found to impact the leaf nutrient content of apple trees. Their relative importance depends on their actual intensity during particular vegetation season. The effect of crop load was higher than the relative growth rate. On the other hand, increased relative growth rate can deepen the depletion of N, P, Mg, Fe, and Mn. The difference between irrigation regimes is less important for mineral nutrient status than that between the wet and semi -dry year conditions. The content of N, K, Fe, and Mn is prone to decrease with pronounced drought of the soil, but with continuous water logging the content of leaf N and Fe may decrease, while P, Mn, and B increase. The year may explain 30-90 % of the observed variability. The inter -annual variability increased with changeable weather as well as with alternating trees performance and may counteract with or even overcome the effect of particular factors. In this context, the content of phosphorus and the micronutrients (Fe, Mn, Zn, and B) seems to be more susceptible than that of the macronutrients N, K, Mg, and Ca.