Increasing yield and carbon sequestration in a signalgrass pasture by liming and fertilization in São Carlos, São Paulo, Brazil.
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This study case aimed to evaluate the impact of liming and mineral fertilization of a Signalgrass pasture on C accumulation in surface and deeper layers of a Brazilian Oxisol. A 27-yr old Signalgrass pasture ((Urochloa decumbens cv. Basilisk Stapf (Syn: Brachiaria)) was used in the trial. This pasture has been grazed in a stocking rate of one animal per ha and did not receive any liming and fertilizer until the beginning of the experiment. Treatments used in a 6-year trial are described in Table 129, and both limestone and fertilizers were applied to the soil surface with no soil plowing or disc-harrowing. Soil C stocks were calculated in equivalent soil mass, taking the native Cerrado (Savanna forest) soil mass as reference. Limed soil (0-100 cm) under non-fertilized pasture showed an annual increase of 1.71 tC/ha after 6 years over the soil under native vegetation. In contrast, fertilization of low productive and degraded pasture resulted in C accumulation rates varying from 5.4 to 7.2 t/ha/yr. The results illustrate that despite the C saturation in the surface soil layer, as evidenced by a sigmoid relationship between C contents in the whole soil and the clay fraction through the soil profile, the large proportion of C accumulation (from 55 to 68 percent) in deeper soil layers makes tropical pasture soils suitable long-term C sinks.
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Mineral fertilization, Soil organic carbon stocks, Adaptation to climate change, Mitigation to climate change, Potential drawbacks, ILPF, Soil management, Liming, No-tillage, Grasslands, Greenhouse gas emissions