(Micro)biological, chemical and physical properties of soils subjected to conventional or no-till management: an assessment of their quality status

In order to evaluate the impact of no-tillage (NT) against conventional-tillage (CT), or the effect of different fertilizers and herbicides, soils recently incorporated to agriculture from the El Salado basin river (Buenos Aires, Argentina) under a corn (1996/1998)-pasture (1998-)rotation were monitored for several soil (micro)biological, physical and chemical properties during the second (1997) to fourth (1999) years from the beginning of the experiment (1996). The rates of exchange of O2 and CO2 expressed in terms of kg O2 or CO2–C per hectare per day, are denoted as qO2 and qCO2. They decreased at the end of the corn growth cycle (T2) along with an increase of the respiratory quotient (RQ=qCO2/qO2), when compared to the time of land preparation (T0), irrespective of the management system. Both, qO2 and qCO2, increased 8 months after the mixed-grass-legume pasture planting (T3) keeping similar RQs with values slightly higher for NT than CT. At T4 (after 20 months of pasture), a 22 and 21% decrease of organic carbon was registered for NT and CT, respectively, with respect to the beginning of the experiment. A 22% (not significative) and a significative 31% diminish of total nitrogen was observed in the NT and CT systems, respectively. The results obtained are discussed in terms of soil function and sustainability in both management systems tested.