Soil-Specific Inventories of Landscape Carbon and Nitrogen Stocks under No-till and Native Vegetation to Estimate Carbon Offset in a Subtropical Ecosystem

Abstract

Inventories of C and N footprints on a landscape scale are essential tools for estimating C offsets from agricultural emissions. Therefore, the aims of this study conducted in the subtropical humid ecosystem in southern Brazil were to: (i) conduct a soil-specific inventory of landscape soil C and N stocks with reference to soil order, soil texture, and land use/management type; (ii) estimate accretion rates for soil organic C (SOC) and total N (TN) for areas managed under no-till (NT) practices management with reference to native vegetation (NV) based on this inventory; (iii) generate a map of C stocks for each land use system; and (iv) calculate estimated C offset for the region through the use of NT compared to conventional tillage (CT). Soil samples were collected at 324 points to a 1-m depth from the entire region. Soil texture and duration of NT had a strong influence on C and N stocks. The average soil C stock across all types of soils for depths of 0–40 and 40–100 cm was 57.0 and 43.0%, respectively. The extrapolation of C stored in the 0- to 40-cm depth based on the NT management for 11 and 20 yr for 1.52 million hectare (Mha) was 9.08 ± 0.62 Tg (1 Tg = 1012 g) representing 11.9% of the C stored in all soil orders. The long-term of C sink capacity by conversion of arable land from CT to NT in this region is 33.2 Tg of CO2, with the C offset of 22.5% of all anthropogenic emissions.