Nitrogen fertilization and agronomic characteristics in blackberry

The objective of this work was to evaluate the influence of increasing doses of nitrogen on vegetative growth, yield and leaf nutrient levels of blackberry (Rubus spp.). The experiment was carried out with the cultivars Tupy and Xavante, in southern state of Rio Grande do Sul, Brazil, from 2008 to 2012. It was used a randomized block design, with four replicates. Treatments consisted of five N doses (0.0, 7.5, 15.0, 22.5 and 30.0 g per plant), applied as maintenance fertilization after the crop establishment. The following variables were evaluated: cane density, pruned dry mass, chlorophyll index, yield, number of fruit, and nutritional composition of leaves for N, K, Ca, Mg and S. The fertilization treatments significantly influenced the vegetative growth, yield, and nutrient composition of leaves. The cultivars responded differently to nitrogen application, with 'Tupy' being more demanding than 'Xavante'. The currently recommended nitrogen rate for blackberry cultivation is suitable for maximum yield of 'Xavante', but it is not sufficient for 'Tupy'.