Effects of phosphate, carbonate, and silicate anions on CO2 emission in a typical oxisol from cerrado region

Abstract

The effects of agricultural practices on greenhouse gases emissions (e.g. CO₂) at the soil-atmosphere interface have been highlighted worldwide. The use of ground limestone has been considered as the main responsible for CO₂ emission from soils. However, liming is need as conditioner of acidic soils and the CO₂ emission can be compensated due to carbon sequestration by plants. This study simulated under laboratory conditions the effects of two common agricultural practices in Brazil (P-fertilization and liming) on soil CO₂ emission. Columns made of PVC tubes containing 1 kg of a typical Dystrophic Red Latosol from Cerrado region were incubated with CaCO₃ (simulating liming), CaSiO₃ (simulating slag), and different doses of KH₂PO₄ (simulating P-fertilization). The soil columns were moistened to reach the field capacity (0.30 cm³ cm^-3) and, during 36 days, CO₂ emissions at the soil surface were measured using a portable Licor LI-8100 analyzer coupled to a dynamic chamber. The results showed that CO₂ emission was influenced by phosphate, carbonate, and silicate anions. When using CaSiO₃, accumulated CO₂ emission (36-day period) was 20% lower if compared to the use of CaCO₃. The same amount of phosphate and liming (Ca-carbonate or Ca-silicate) added to the soil provided the same amount of CO₂ emission. At the same P dose, as Si increased the CO₂ emission increased. The highest CO₂ emission was observed when the soil was amended with the highest phosphate and silicate doses. Based on this experiment, we could oppose the claim that the use of limestone is a major villain for CO₂ emission. Also, we have shown that other practices, such as fertilization using P + CaSiO₃, contributed to a higher CO₂ emission. Indeed, it is important to emphasize that the best practices of soil fertility management will undoubtedly contribute to the growth of crops and carbon sequestration.