• Energy Research

Abstract Soil methane (CH4) and nitrous oxide (N2O) fluxes are difficult to predict from soil temperature and moisture alone, especially compared to carbon dioxide (CO2) fluxes. That difficulty is reflected in high spatial and temporal (spatiotemporal) variability of these two greenhouse gases (GHGs). We used a 16 ha field, under homogeneous soils and vegetation, to simultaneously explore spatial and temporal variability of soil CH4 and N2O fluxes. We also measured soil physical and chemical properties in order to explain, and predict, spatial variability of these two gases. Gas fluxes were measured using either a dynamic chamber (spatial variability study) or automated chambers using FTIR (temporal variability study). Soil samples were analysed for 30 chemical parameters (including at least two forms of soil carbon and nitrogen), while two proximal soil sensors were used to collect fine-resolution soil electrical conductivity and gamma radiometric concentration across the site. Fluxes of CH4 and N2O showed distinct spatial patterns, and were uniquely related to soil properties. Spatial variability in both CH4 and N2O fluxes was greater than five months of temporal variability (an increase in 112% and 39% in standard deviations for each gas respectively). If we relied solely on the autochambers for mean field fluxes, we would have underestimated fluxes by 59 and 197%, for CH4 and N2O respectively. CH4 fluxes were more spatially-dependent than those of N2O (semivariance analysis), but both showed greater spatial dependence than previously reported. Nearly 40 and 50% of the mean spatial flux of CH4 and N2O were from 1% of the area. Spatial variability in soil CH4 fluxes was predicted best by electrical conductivity measurements at 0–50 cm (r = 0.74) and soil C. Soil N2O fluxes, on the other hand, were predicted best by soil N and the gamma radiometric data (r = 0.48). Overall, our results clearly show that the large spatial variance of both CH4 and N2O fluxes requires great caution when scaling from chamber-based measurements to the field and beyond. Proximal sensors (as used here) can help map “hot spots” of soil CH4 and N2O fluxes at the field scale.

Soil ecosystem services (ES) provide multiple benefits to human well-being, but the failure to appreciate them has led to soil degradation issues across the globe. Despite an increasing interest in the threats to soil resources, economic valuation in this context is limited. Importantly, most of the existing valuation studies do not account for the spatial distribution of benefits that soil ES provide to the population. In this study, we present the results of a choice experiment (CE) aimed at investigating spatial heterogeneity of attitudes and preferences towards soil conservation and soil ES. We explored spatial heterogeneity of both attitudes and welfare measures via GIS techniques. We found that citizens of the Veneto Region (Northeast Italy) generally have positive attitudes towards soil conservation. We also find positive willingness-to-pay (WTP) values for soil ES in most of the study area and a considerable degree of heterogeneity in the spatial taste distribution. Finally, our results suggest that respondents with pro-environmental attitudes display a higher WTP based on the geographic pattern of the distribution of WTP values and attitudinal scores across the area.

The role of soil in the existential environmental problems of declining biodiversity, climate change, water and energy security, impacting on food security has highlighted the need to link the soil functions to ecosystem services. We describe and illustrate by a limited example, the concepts and assessment of soil’s capacity measured through its capability and condition as contributors to an overall soil security framework. The framework is based on the concepts of genosoils and phenosoils. The links to other notions, such as threats to soil and soil functions are made. The framework can be potentially applied elsewhere to quantify soil changes under natural processes and human activities.

Soil Security is an emerging sustainability science concept with global application for guiding integrated approaches to land management, while balancing ecosystem services, environmental, social, cultural, and economic imperatives. This discussion paper sets the scene for an Australian Soil Security framework as an example of how it might be developed for any country, defining the key issues and justification for Soil Security, as well as detailing implementation requirements and benefits; two examples of beneficial outcomes are provided in terms of facilitating decommoditization of agricultural products and the impact of urban encroachment on productive land. We highlight research gaps, where new knowledge will contribute to well-rounded approaches that reflect differing stakeholder perspectives. We also provide key nomenclature associated with a potential Soil Security framework so that future discussions may use a common language. Through this work we invite scientific and policy discourse with the aim of developing more informed responses to the myriad of competing demands placed on our soil systems.

Recent reviews have identified major themes within regenerative agriculture—soil health, biodiversity, and socioeconomic disparities—but have so far been unable to clarify a definition based on practice and/or outcomes. In recent years, the concept has seen a rapid increase in farming, popular, and corporate interest, the scope of which now sees regenerative agriculture best viewed as a movement. To define and guide further practical and academic work in this respect, the authors have returned to the literature to explore the movement’s origins, intentions, and potential through three phases of work: early academic, current popular, and current academic. A consistent intention from early to current supporters sees the regeneration, or rebuilding, of agricultural resources, soil, water, biota, human, and energy as necessary to achieve a sustainable agriculture. This intention aligns well with international impetus to improve ecosystem function. The yet to be confirmed definition, an intention for iterative design, and emerging consumer and ecosystem service markets present several potential avenues to deliver these intentions. To assist, the authors propose the Farmscape Function framework, to monitor the impact of change in our agricultural resources over time, and a mechanism to support further data-based innovation. These tools and the movement’s intentions position regenerative agriculture as a state for rather than type of agriculture.

The ‘4 per mille Soils for Food Security and Climate’ was launched at the COP21 with an aspiration to increase global soil organic matter stocks by 4 per 1000 (or 0.4 %) per year as a compensation for the global emissions of greenhouse gases by anthropogenic sources. This paper surveyed the soil organic carbon (SOC) stock estimates and sequestration potentials from 20 regions in the world (New Zealand, Chile, South Africa, Australia, Tanzania, Indonesia, Kenya, Nigeria, India, China Taiwan, South Korea, China Mainland, United States of America, France, Canada, Belgium, England & Wales, Ireland, Scotland, and Russia). We asked whether the 4 per mille initiative is feasible for the region. The outcomes highlight region specific efforts and scopes for soil carbon sequestration. Reported soil C sequestration rates globally show that under best management practices, 4 per mille or even higher sequestration rates can be accomplished. High C sequestration rates (up to 10 per mille) can be achieved for soils with low initial SOC stock (topsoil less than 30 t C ha− 1), and at the first twenty years after implementation of best management practices. In addition, areas which have reached equilibrium will not be able to further increase their sequestration. We found that most studies on SOC sequestration only consider topsoil (up to 0.3 m depth), as it is considered to be most affected by management techniques. The 4 per mille number was based on a blanket calculation of the whole global soil profile C stock, however the potential to increase SOC is mostly on managed agricultural lands. If we consider 4 per mille in the top 1m of global agricultural soils, SOC sequestration is between 2-3 Gt C year− 1, which effectively offset 20–35% of global anthropogenic greenhouse gas emissions. As a strategy for climate change mitigation, soil carbon sequestration buys time over the next ten to twenty years while other effective sequestration and low carbon technologies become viable. The challenge for cropping farmers is to find disruptive technologies that will further improve soil condition and deliver increased soil carbon. Progress in 4 per mille requires collaboration and communication between scientists, farmers, policy makers, and marketeers.