An experimental study of the influence of traditional slash-and-burn practices on soil erosion

A study of the effects of slash-and-burn on two 4 × 20 m plots with 30% slope and initial vegetation cover dominated by Ulex is reported. The plots were prepared, burnt and sown with rye following methods used in the area in the 18th century. Available nutrient contents in the plots, and in sediments removed from the plots by surface runoff, were monitored for nine months after burning. Similar data were collected from an adjacent undisturbed control plot. and-burn increased the availability of phosphorus and, to a lesser extent, of other plant nutrients. These effects were largely confined to the soil surface, with no appreciable changes being observed below 5 cm. Total soil losses by surface runoff from the burnt plots were 45.7 T ha−1 and 57.2 T ha−1, as compared with 1.4 T ha−1 from the control plot. Total rainfall during this period was 1636 mm; total runoff amounts from the burnt plots were 142 and 181 mm, as compared with 46 mm from the control plot. Available nutrient losses in surface runoff from the burnt plots over this period, particularly by particulate transport, were 23–28 kg ha−1 for phosphorus, 265–290 kg ha−1 for nitrogen and 1380–1710 kg ha−1 for potassium. s indicate that slash-and-burn as traditionally practised in Galicia leads to considerable soil degradation, confirming the assertions of agricultural historians such as Bouhier (1979).