Physical recovery of an oxisol subjected to four intensities of dairy cattle grazing

The expansion of dairy farming in southern Brazil, mainly under a rotational grazing system, has generated soil physical changes with loss of soil quality, which in turn must be evaluated to determine how long they persist and how the soil recovers from these changes. The objective of this study was to evaluate the natural recovery of the soil physical attributes of a clayey Oxisol (Latossolo Vermelho distrófico típico, with clayey texture), which had been managed under different intensities of dairy cattle grazing: T0 = no grazing, T30 = consumption of 30 % of available forage, T50= consumption of 50 % of available forage and T80= consumption of 80 % of available forage. The rotational grazing system consisted of a grazing period (an average of 4 h) with a variable stoking rate to achieve forage consumption. For T0, zero animals, T30 three animals, T50 six animals and T80 nine animals per 100 m ² plot were used, followed by animal exclusion until the forage reached an average height of 35 cm. The grazing system was conducted for approximately 7 months, after which the animals were permanently removed from the area. The recovery of soil physical properties was monitored by soil sampling every three months for one year. The evaluated soil physical properties were porosity, bulk density and air permeability. The increase in grazing intensity negatively affected the soil physical quality. At all grazed areas, T30, T50 and T80, there was a reduction of the total porosity, the macroporosity and the soil air permeability, as well as an increase of the soil bulk density compared with the no grazed area, T0. However, 90 days after exclusion, increases in total porosity and macroporosity were observed. The angular coefficient between soil air-filled porosity and air permeability decreased as the grazing intensity increased and increased with time after grazing exclusion. Rotational grazing areas, when managed properly, can be an important tool for sustainable production. The use of grazing exclusion periods alleviates compaction, reducing the risk for forage production for the following grazing season.