Effect of Nitrogen Fertiliser on Growth and Production of Apples in the Conditions of Latvia

Nitrogen is a nutrient necessary for many functions of plants, e.g. shoot growth, fruit and flower bud set, and fruit size. In Latvia use of mineral fertilisers is limited by EU Directives and Regulations developed on the basis of the Guidelines of Integrated Production. The aim of the study was to investigate the effect of nitrogen (N) fertiliser on apple growth and production in the conditions of Latvia. The study was performed during 2013 to 2015. In an apple trial, seven cultivars on rootstock B.396 were planted in 2009. There were two fertiliser treatments: without fertilising and N 6 g·m^-2. Significant effect of treatment was observed only in cultivar ‘Ligol’. Tree crown in the N treatment was over-dense, shoots too long, yet all cultivars had over-long shoots also in the unfertilised treatment. Effect of nitrogen in regard to amounts of acceptable and unacceptable shoots of the cultivars included in trial was negative. Nitrogen significantly increased the amount of unacceptable shoot types of cultivars ‘Gita’, ‘Rubin’ (Kazakhstan), and ‘Ligol’. Additional nitrogen as fertiliser had no significant effect on growth and yield of cultivars ‘Antei’, ‘White Transparent’ and ‘Konfetnoye.’ The cumulative yield of ‘Kovalenkovskoye’ and ‘Ligol’ was positively affected by nitrogen fertiliser. The most pronounced biennial yielding was observed for cultivar ‘Rubin’. Cultivar ‘Ligol’ had the most active and longer vegetation, especially in the nitrogen fertilisers treatment.