Effects of Nitrogen fertilisation and stocking rates on soil erosion and water infiltration in a Brazilian Cerrado farm

Abstract

Ever-increasing water-food-energy demand has led to the depletion of soil resources by mainly inadequate grazing practices. Nevertheless, the effects of different grazing practices on hydrological and soil erosion processes have not yet been well-understood. Therefore, we investigated the influence of different Nitrogen application doses and stocking rates in a pasture under rotational stocking (RS) on soil erosion and water infiltration in the Brazilian Cerrado region. The experimental area was a Panicum maximum pasture and was divided into three treatments with N applications of 100, 200, and 300 kg ha-1, which respectively allowed three stocking rates from 2014 to 2018: 3 (RS-3), 4.1 (RS-4), and 5 AU ha-1 (RS-5). We respectively adopted start and stop grazing heights of 80–90 and 40–50 cm (forage height) in all treatments. To evaluate infiltration and soil erosion, we performed 28 rainfall simulations with intensities ranging from 73.5 to 93.5 mm h-1 in plots of 0.7 m2 from November 2017 to February 2018. The simulations were carried out in random sites inside the central paddocks of each treatment comprising four repetitions in each treatment under vegetation and bare soil. We found stable water infiltration (SIR) and soil loss (SLw) ranging from 65.5 to 87.2 mm h-1 and from 0.03 to 0.15 mg s-1 m-2, respectively. SIR and SLw under RS-5 were respectively 33% greater and 78% lower than under RS-3 despite the 67% higher stocking rate in RS-5. We found that higher stocking rates at optimal grazing pressure did not deteriorate water infiltration and soil erosion. Our findings reveal an opportunity for a 5-fold productivity increase while reducing soil degradation since adaptive stocking rates are supported by grazing processes along with an increase in N fertiliser dose to increase vegetation cover.