Resumen

GILI, Perla; ARUANI, Cristina; REEB, Pablo  y  AUN, Elizabeth. Biological changes in nitrogen fertilized soil of apple orchards in the Alto Valle of Rio Negro. Cienc. suelo [online]. 2009, vol.27, n.2, pp.209-216. ISSN 1850-2067.

The aim of this study was to determine the effect of nitrogen application at different moments during the apple crop cycle on the population of soil microorganisms in terms of microbial biomass carbon, enzymatic activity and edaphic properties. Nitrate content, total nitrogen, organic carbon, microbial biomass carbon, deshidrogenase and catalase activity were determined and the carbon mineralization index, the proportion of microbial biomass carbon in organic carbon and the metabolic coefficient (qCO₂) were calculated. Nitrogen was applied as ammonium nitrate (NH₄NO₃) at two rates, 100 (N₁) and 200 kg N ha-¹ (N₂), and on two times, 50% at petal fall (October) and the rest at harvest (March), and the results compared with a control treatment without N (N₀). The experiment was repeated over two growing seasons, 2005-2006 and 2006-2007. Soil samples were taken before and after each fertilization. Nitrogen addition had differential effects on soils chemical and biological properties depending on the season and plant phenology. In autumn and spring, soil nitrates (NO₃ -) increased significantly and soil biota was modified during both growing seasons. In the 2005-2006 season, spring nitrogen additions increased soil biota activity in terms of C-BM, RE and Dh-asa; whereas in the second growing season, 2006-2007, nitrogen addition had no effect on soil chemical and biological properties. Soil biological activity was affected by orchard management practices, fertilization and pruning.

Palabras clave : Nitrogen fertilization; Biological indicators; Apple.

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