EFFECT OF ANIMAL TRAMPLING ON THE PROPERTIES OF A SOIL. PART I: BULK DENSITY, MOISTURE, PENETRATION RESISTANCE, AND ASSOCIATED MODELS

The intensification of animal production leads to increased soil trampling, which is an effect that has not been studied extensively. The objectives of this study were: 1) To compare the bulk density (DA) at two different depths for four levels of trampling intensity (Ip); 2) To compare the mechanical strength (Rp) of the soil, in the same range of soil moisture and at two different depths for four levels of Ip; 3) To study the dependence of Rp with DA, and the gravimetric moisture (H) for four levels of Ip using the models proposed by Busscher and by Ayers. The study was carried out in an animal production facility located in the province of Buenos Aires, Argentina, on a plain with planted legume and grass pastures. Certain sectors were used for grazing and other sectors for mechanical cutting without trampling. DA, H and Rp were measured for four Ip levels: zero (A), medium (B), high (C) and very high (D). Texture and total carbon (CT) of the soil were determined. It was found the lowest value of DA (0.98 g cm(-3)) in group D between 0 and 10 cm, attributed to its high content of CT (682 g kg(-1)). Group A had the lowest Rp value between 0 and 10 cm (4.41 MPa). It was concluded that, unlike DA, Rp was a good indicator of the Ip in the depths from 0-10 cm. Models that relate Rp with H and DA would not apply to soils where the content of CT is high and there is loss of structure by poaching.