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Resumo -O objetivo deste trabalho foi avaliar a influência de doses crescentes de nitrogênio sobre o crescimento vegetativo, a produção e os níveis foliares de nutrientes da amoreira-preta (Rubus spp.). O experimento foi realizado com as cultivares Tupy e Xavante, na região sul do Rio Grande do Sul, de 2008 a 2012. Os tratamentos consistiram da aplicação de cinco doses de N (0,0, 7,5, 15,0, 22,5 e 30,0 g por planta), aplicados na adubação de manutenção, após a implantação da lavoura. Utilizou-se o delineamento de blocos ao acaso, com quatro repetições. Foram avaliadas as variáveis: densidade de hastes, massa de matéria seca de poda, índice de clorofila, produção por planta, número de frutos e composição nutricional das folhas (N, K, Ca, Mg e S). A adubação nitrogenada influenciou significativamente o crescimento vegetativo, a produção e a composição nutricional das folhas. As cultivares apresentaram resposta distinta à aplicação de N, em que 'Tupy' foi mais exigente que 'Xavante'. As doses de N atualmente recomendadas para a cultura da amoreira-preta são satisfatórias para a máxima produção de 'Xavante', mas insuficientes para 'Tupy'.Termos para indexação: Rubus, crescimento vegetativo, nitrogênio, nutrição mineral, pequenas frutas, produção. Nitrogen fertilization and agronomic characteristics in blackberryAbstract -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'.

The objective of this work was to evaluate the distribution pattern and composition of soil organic matter (SOM) and its physical pools of Leptosols periodically affected by fire over the last 100 years in South Brazil. Soil samples at 0-5, 5-10, and 10-15 cm depths were collected from the following environments: native pasture without burning in the last year and grazed with 0.5 livestock per hectare per year (1NB); native pasture without burning in the last 23 years and grazed with 2.0 livestock per hectare per year (23NB); and an Araucaria forest (AF). Physical fractionation was performed with the 0-5 and 5-10 cm soil layers. Soil C and N stocks were determined in the three depths and in the physical pools, and organic matter was characterized by infrared spectroscopy and thermogravimetry. The largest C stocks in all depths and physical pools were found under the AF. The 23NB environment showed the lowest soil C and N stocks at the 5-15 cm depth, which was related to the end of burning and to the higher grazing intensity. The SOM of the occluded light fraction showed a greater chemical recalcitrance in 1NB than in 23NB. Annual pasture burning does not affect soil C stocks up to 15 cm of depth.

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