Análisis de los escurrimientos de una microcuenca de Pampa Ondulada bajo diferentes sistemas de labranza

The runoff rate constitutes a key factor in the determination of soil losses in arable lands. In the last decade, no tillage system became widespread in the Rolling Pampa. However, scarce studies have been carried out in a watershed scale about its effects on runoff dynamics, as compared to other tillage systems. The aim of the present study was to compare different parameters related to the surface runoff response of a watershed associated with changes in the tillage systems. The studied watershed has 300 ha and is located in the Northern part of the mid basin of the Tala river in San Pedro, Buenos Aires Province. The soils belong to the Ramallo Series (Vertic Argiudoll) and its eroded phases. Hydrographs and hietographs belonging to different storms that took place through the period 1995-2002 were calculated and runoff was analyzed, first globally and then the increasing and decreasing branches of the flow separately. No tillage system originated larger curve number values than the conventional tillage system. The runoff duration was larger under no tillage due to the enlargement of the decreasing branch of the hydrograph. The runoff flow generated per rainfall unit was always lower under no tillage compared to conventional tillage. The amount of runoff during the decreasing branch of the hydrographs was not different between tillage systems because the lesser flow recorded under no tillage was compensated by the larger duration of this phase compared to conventional tillage