Soil carbon sequestration potential of permanent pasture and continuous cropping soils in New Zealand

Abstract

Understanding soil organic carbon (SOC) sequestration is important to develop strategies to increase the SOC stock and, thereby, offset some of the increases in atmospheric carbon dioxide. Although the capacity of soils to store SOC in a stable form is commonly attributed to the fine (clay + fine silt) fraction, the properties of the fine fraction that determine the SOC stabilization capacity are poorly known. The aim of this study was to develop an improved model to estimate the SOC stabilization capacity of Allophanic (Andisols) and non-Allophanic topsoils (0-15 cm) and, as a case study, to apply the model to predict the sequestration potential of pastoral soils across New Zealand. A quantile (90th) regression model, based on the specific surface area and extractable aluminium (pyrophosphate) content of soils, provided the best prediction of the upper limit of fine fraction carbon (FFC) (i.e. the stabilization capacity), but with different coefficients for Allophanic and non-Allophanic soils. The carbon (C) saturation deficit was estimated as the difference between the stabilization capacity of individual soils and their current C concentration. For long-term pastures, the mean saturation deficit of Allophanic soils (20.3 mg C g ) was greater than that of non-Allophanic soils (16.3 mg C g ). The saturation deficit of cropped soils was 1.14-1.89 times that of pasture soils. The sequestration potential of pasture soils ranged from 10 t C ha (Ultic soils) to 42 t C ha (Melanic soils). Although meeting the estimated national soil C sequestration potential (124 Mt C) is unrealistic, improved management practices targeted to those soils with the greatest sequestration potential could contribute significantly to off-setting New Zealand's greenhouse gas emissions. As the first national-scale estimate of SOC sequestration potential that encompasses both Allophanic and non-Allophanic soils, this serves as an informative case study for the international community.

Ideas and perspectives: Can we use the soil carbon saturation deficit to quantitatively assess the soil carbon storage potential, or should we explore other strategies?

“…(2014), Castellano et al (2015) or McNally et al (2017). However, the quantitative link between the Csat-def of a soil and its potential to store OC persistent at a pluri-decadal timescale has not been clearly established yet and deserves further research.…”

“…Recent studies using the Csat-def proposed appealing results to policy makers such as regional (Wiesmeier et al, 2014; or national estimates (Angers et al, 2011;McNally et al, 2017) of the soil C sequestration potential. Our point is that, if the soil 5…”

Carbon sequestration of cropland and paddy soils in China: potential, driving factors, and mechanisms

“…The chemical protective effect of soil on organic carbon refers to the interaction between soil inorganic molecules and organic molecules, which makes organic carbon difficult to be utilized by microorganisms. Among them, clay minerals and metal oxides are the main carriers of organic carbon . Organic carbon combines with soil minerals in various forms – such as through coordination exchange, hydrogen bond, cation bond bridge, and Van der Waals force – which is considered an important stabilizing mechanism of SOC …”

“…Among them, clay minerals and metal oxides are the main carriers of organic carbon . Organic carbon combines with soil minerals in various forms – such as through coordination exchange, hydrogen bond, cation bond bridge, and Van der Waals force – which is considered an important stabilizing mechanism of SOC …”

Accounting for Carbon Stocks in Soils and Measuring GHGs Emission Fluxes from Soils: Do We Have the Necessary Standards?

“…Schulte et al (2016) proposed a framework for climate smart land management in Ireland where they combine and map soil and land information including the current soil C stocks, the potential additional SOC storage and the sensitivity of soils to emit CO 2 . McNally et al (2017) estimated the C sequestration potential of soils from permanent pasture and continuous cropping in New Zealand using the concept of saturation deficit as previously used by Angers et al (2011). At the global scale, Paustian et al (2016) summarized soil management practices and estimated a potential of mitigation of around 8 Pg (Co 2 eq) a year.…”