pH and exchangeable aluminum are major regulators of microbial energy flow and carbon use efficiency in soil microbial communities

The microbial partitioning of organic carbon (C) into either anabolic (i.e. growth) or catabolic (i.e. respiration) metabolic pathways represents a key process regulating the amount of added C that is retained in soil. The factors regulating C use efficiency (CUE) in agricultural soils, however, remain poorly understood. The aim of this study was to investigate substrate CUE from a wide range of soils (n = 970) and geographical area (200,000 km2) to determine which soil properties most influenced C retention within the microbial community. Using a 14C-labeling approach, we showed that the average CUE across all soils was 0.65 ± 0.003, but that the variation in CUE was relatively high within the sample population (CV 14.9%). Of the major properties measured in our soils, we found that pH and exchangeable aluminum (Al) were highly correlated with CUE. We identified a critical pH transition point at which CUE declined (pH 5.5). This coincided exactly with the point at which Al3+ started to become soluble. In contrast, other soil factors [e.g. total C and nitrogen (N), dissolved organic C (DOC), clay content, available calcium, phosphorus (P) and sulfur (S), total base cations] showed little or no relationship with CUE. We also found no evidence to suggest that nutrient stoichiometry (C:N, C:P and C:S ratios) influenced CUE in these soils. Based on current evidence, we postulate that the decline in microbial CUE at low pH and high Al reflects a greater channeling of C into energy intensive metabolic pathways involved in overcoming H+/Al3+ stress (e.g. cell repair and detoxification). The response may also be associated with shifts in microbial community structure, which are known to be tightly associated with soil pH. We conclude that maintaining agricultural soils above pH 5.5 maximizes microbial energy efficiency

Soil Exchangeable Cations Increase Microbial Carbon Use Efficiency and Microbial Growth in Acidic Soils

Microbial growth and function is influenced by the properties of the surrounding soil where surface chemistry mediates interactions between individual organisms and their local microenvironment. We hypothesised that the addition of exchangeable base cations, necessary for microbial biochemical function, will increase microbial growth in acidic soils

Greenhouse gas and ammonia emission mitigation priorities for UK policy targets

Publication history: Accepted - 16 March 2023; Published online - 6th May 2023.Agriculture is essential for providing food and maintaining food security while concurrently delivering multiple other ecosystem services. However, agricultural systems are generally a net source of greenhouse gases and ammonia. They, therefore, need to substantively contribute to climate change mitigation and net zero ambitions. It is widely acknowledged that there is a need to further reduce and mitigate emissions across sectors, including agriculture to address the climate emergency and emissions gap. This discussion paper outlines a collation of opinions from a range of experts within agricultural research and advisory roles following a greenhouse gas and ammonia emission mitigation workshop held in the UK in March 2022. The meeting identified the top mitigation priorities within the UK’s agricultural sector to achieve reductions in greenhouse gases and ammonia that are compatible with policy targets. In addition, experts provided an overview of what they believe are the key knowledge gaps, future opportunities and co-benefits to mitigation practices as well as indicating the potential barriers to uptake for mitigation scenarios discussed.This work was supported with funding from the Scottish Government Strategic Research Programme (2022−2027, C2-1 SRUC) and Biotechnology and Biological Sciences Research Council (BBSRC) (BBS/E/C/000I0320 and BBS/E/C/000I0330). We also acknowledge support from UKRI-BBSRC (UK Research and Innovation-Biotechnology and Biological Sciences Research Council) via grants BBS/E/C/000I0320 and BBS/E/C/000I0330, and Rothamsted Research Science Initiative Catalyst Award supported by BBSRC

Soil Exchangeable Cations Increase Microbial Carbon Use Efficiency and Microbial Growth in Acidic Soils

Microbial growth and function is influenced by the properties of the surrounding soil where surface chemistry mediates interactions between individual organisms and their local microenvironment. We hypothesised that the addition of exchangeable base cations, necessary for microbial biochemical function, will increase microbial growth in acidic soils