Response of soil organic carbon stock to land use is modulated by soil hydraulic properties

Abstract

Understanding the effects of land use on soil organic carbon (SOC) stock is important to develop practices that promote agricultural sustainability and mitigate climate change. The objective of this study was to explore whether the effects of land use on SOC stock differed with soil type and, particularly, with soil hydraulic properties. For this purpose, 90 sites from the Canterbury Plains, New Zealand, were sampled to a depth of 30 cm. The sampled sites consisted of long-term (>20 years) dryland pasture [DP], irrigated pasture [IP], and irrigated cropping [IC] covering three contrasting soil types with different soil drainage levels, including well drained Lismore (LIS) soil, imperfectly drained Templeton (TEM) soil, and poorly drained Waterton/Temuka (WAT) soil. On average, compared with DP, IP increased SOC and hot water extractable carbon (HWEC) stock at all depths; IC decreased SOC and HWEC at 0–15 cm. The results highlighted that the effects of land use change from DP to IP and IC on total SOC and HWEC stock significantly differed between soil types. The greatest gains in SOC and HWEC stocks following change from DP to IP were found in LIS soil; the greatest losses in SOC and HWEC stocks following change from DP to IC were found in WAT soil; and no significant differences in SOC stocks with land use changes were found in TEM soil. The results implied that the interaction between land use and soil type on SOC and HWEC stocks was associated with soil hydraulic properties (e.g. available water capacity and field capacity) that regulate the response of C inputs (net primary productivity) and outputs (microbial decomposition) to land use and management practices (e.g. irrigation and cultivation). Therefore, soil hydraulic properties should be taken into account in designing land use for the purpose of SOC sequestration.