Long-term field trials can provide important information about the effects of soil management practices on soil properties but there are relatively few such trials available. The Agricultural Research and Development Station in Oradea (Bihor county) provided opportunity to study the effects of 18 years of cultivation on preluvosoil. The objective of the reported work was to determine at this site the effects of soil management practices on phosphatase activities as an index of soil biology. Phosphatase (phosphomonoesterase) activities were determined for two years, from 2008 to 2009, in the 0-20, 20-40 and 40-60 cm layers of a preluvosoil, from a long term trials with various tillage practices (no-till and conventional tillage), crop rotation (2 and 6 crop rotations) and fertilization [mineral (NP) fertilization and farmyard-manuring] experiment. The determined activities decreased with increasing sampling depth. No-till - in comparison with conventional tillage - resulted in significantly higher soil phosphatase activities in the 0-20 and in significantly lower activities in the deeper layers. The soil under maize or wheat was more enzyme-active in the 6 than in the 2 crop rotation. In the 2 crop rotation, higher phosphatase activities were recorded under wheat than under maize. Farmyard-manuring of maize - in comparison with mineral (NP) fertilization - led to a significant increase in enzyme activities. Maintenance of enzyme activities over tens of years in agricultural soils is partly attributed to traditional management practices including rotations with legumes, additions of animal manures, and minimum tillage.
