Soil Organic14C Dynamics: Effects of Pasture Installation on Arable Land

Abstract

In a study addressing composition and recovery of soil carbon following pasture installation on arable land, radiocarbon isotope ratios were measured in size- and density-separated soil organic matter (SOM) fractions in a pasture and maize plot. The average soil carbon age increased with depth from 444 yr in the 0–30-cm layer to 2456 yr in the 60–80-cm layer in the pasture soils, and from 42 to 1625 yr in the maize-cultivated soil. Weight fractionation of the macro-organic matter (size >150 μm) in a light (density -3) intermediate (1.17 g cm^-3< density < 1.37 g cm^-3), and heavy fraction (density >1.37 g cm^-3) resulted in markedly different ages for different fractions with ages increasing from 2 yr in the light fraction to >3000 yr in the heavy fractions.¹³C and¹⁴C (accelerator mass spectrometry (AMS)) isotope ratios in the 13C and¹⁴C analysis, resulted in a better insight in carbon dynamics that occur after the conversion of arable land to pasture.