Temporal Variability of Soil Biological Properties in Temperate Grasslands and Croplands Amended with Organic and Inorganic Fertilizers

Soil biological properties have been widely used as indicators of soil quality, but the wide use of these properties as soil quality indicators is hindered by the uncertainty of their seasonal patterns. In our work we have assessed the seasonal variation of several biological properties (biomass carbon and nitrogen, net nitrogen mineralization, soil basal respiration, dissolved organic nitrogen, and dissolved organic carbon) over an almost 3-year period, starting in February 2008 and finishing in December 2010, in two different trials: (A) grazed grasslands and (B) corn cultivated cropland. In trial A we studied the influence of stock density on soil biological properties, whereas in trial B we studied how biological properties are affected by fertilizer type. Trials, located in a temperate area (43° 14′ N latitude, 8° 15′ W longitude, and 97 m above sea level) of northwestern Spain, were carried out as a completely randomized block design with three replicates. Our data show a high seasonality for the studied properties and a consistent influence of management.