Chemical pattern of vegetation and topsoil of rangeland fertilized over 21 years with phosphorus sources and limestone

Abstract

The Pampa’s rangeland in South America is underused or replaced by annual crops or forest cultivation with higher economic returns. Our goal was to test the long term effects of phosphorus fertilizer and limestone applications on P availability, aluminum neutralization in deep soil layer and rangeland productivity. For this, three rates of three phosphorus sources combined with limestone were applied in a 21 year field trial. The dry matter (between 2016 and 2019) and nutrient accumulation in plant shoot were measured. The topsoil was divided in four layers (0–2.5, 2.5–5.0, 5.0–7.5, and 7.5–10.0 cm), and chemical properties were determined. Rock phosphate application at rate 249 kg ha−1 of P increased the soil P content along the soil profile down to 7.5 cm. After 21 years of liming, the neutralizing front reached depths greater than 10 cm and the reacidification was not significant. In these conditions, the contents of exchangeable Ca, Mg and Al and pH are greater than, and Al saturation is lower than without limestone. The effect of fertilization and limestone amendments are however limited in time and there was no response of rangeland dry matter production after more than four years after the last fertilization.