Evaluation of physical-chemical and biological characteristics of two soils grown with pear (Pyrus communis L.) cv. Williams under conventional management

The objective of this work was to study the physico-chemical and biological properties of two surface soils fertilized with nitrogen and organic amendment in the Upper Rio Negro Valley (orchards H1 and H2). In both orchards, nitrogen fertilizer was applied during the 2008-2009 and 2009-2010 seasons and on H2 chicken manure was applied. Soil samples were collected in spring and autumn and determined: total organic carbon, electrical conductivity, exchangeable cations, sodium adsorption ratio and nitrate, microbial respiration, microbial biomass carbon, dehydrogenase activity and the rate of mineralization. The concentration of total organic carbon, nitrogen and potassium were suitable for the production of pears. The behavior of biological variables was different in the orchards. In orchard H1 were higher in spring, in both seasons, and the mineralization rate was slightly higher than 1 in autumn, indicating some balance between mineralization and humification of carbon. In H2 biological measurements were similar between seasons as a result of making nitrogen (N) fertilization in spring and autumn. The organic amendment did not increase the biological activity in the spring. Microbial and enzymatic activities in H1 and H2 were sensitive to changes occurring in soils.