Seasonal dynamics of mineral nitrogen in the soil of apple orchard

The purpose of the study was to investigate mineral nitrogen (Nmin) behavior in the soil of young apple orchard, with the aim of clarification of the indices necessary for precision diagnostics of apple tree nitrogen nutrition. Seasonal dynamics of Nmin (nitrate and ammonia) in the soil was investigated during 2016-2019 growing seasons in the orchard situated in the forest-steppe zone of the Central Russian Upland (Oryol Region). Fruit plantings were represented by the trees of the apple-tree of the varieties Sinap Orlovsky and Venyaminovskoe on the stock 54-118, planted in 2013. Soil samples were collected from soil layers 0-20, 20-40 and 40-60 cm monthly from May to September and analyzed on N-NH4 and N-NO3 content. The samples of the leaves were collected in late July. Without fertilizers loamy haply luvisol of experimental orchard provided high level of nitrogen nutrition for the apple trees during 6 years after planting. During vegetative periods of 2016 and 2019 the average content of mineral nitrogen in the soil layer of 0-60 cm made 23.06 ± 3.08 mg/kg. In 2017 and 2018 the average content of Nmin in the soil was twice lower (12.47 ± than 1.95 mg/kg) because of adverse weather conditions. At the same time the leaf nitrogen status of both cultivars was favorable (varied within 2-3.5 % dry matter) during all the years of the experiment. Mineral nitrogen dynamics had specific features in every growing season, but annually the lowest Nmin content in the soil was observed in August (within 5.68-15.63 mg kg-). Significant positive correlation (R=+0.80; P function show_eabstract() { $('#eabstract1').hide(); $('#eabstract2').show(); $('#eabstract_expand').hide(); }