The importance of nitrogen for net carbon sequestration when considering natural climate solutions

Davies, Christian A.; Robertson, Andy; McNamara, Niall P.

doi:10.1111/gcb.15381

Cited by 9 publications

(3 citation statements)

References 11 publications

(27 reference statements)

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“…An increase in SOC is often associated with higher N 2 O emissions, which could counteract the mitigation benefits derived from C sequestration (Davies et al, 2020). However, it is precisely in these trade‐offs where biochar might have the greatest advantage compared to other soil amendments and other SOC sequestration strategies.…”

Section: Biochar's Role In Climate Change Mitigationmentioning

confidence: 99%

How biochar works, and when it doesn't: A review of mechanisms controlling soil and plant responses to biochar

et al. 2021

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We synthesized 20 years of research to explain the interrelated processes that determine soil and plant responses to biochar. The properties of biochar and its effects within agricultural ecosystems largely depend on feedstock and pyrolysis conditions. We describe three stages of reactions of biochar in soil: dissolution (1–3 weeks); reactive surface development (1–6 months); and aging (beyond 6 months). As biochar ages, it is incorporated into soil aggregates, protecting the biochar carbon and promoting the stabilization of rhizodeposits and microbial products. Biochar carbon persists in soil for hundreds to thousands of years. By increasing pH, porosity, and water availability, biochars can create favorable conditions for root development and microbial functions. Biochars can catalyze biotic and abiotic reactions, particularly in the rhizosphere, that increase nutrient supply and uptake by plants, reduce phytotoxins, stimulate plant development, and increase resilience to disease and environmental stressors. Meta‐analyses found that, on average, biochars increase P availability by a factor of 4.6; decrease plant tissue concentration of heavy metals by 17%–39%; build soil organic carbon through negative priming by 3.8% (range −21% to +20%); and reduce non‐CO2 greenhouse gas emissions from soil by 12%–50%. Meta‐analyses show average crop yield increases of 10%–42% with biochar addition, with greatest increases in low‐nutrient P‐sorbing acidic soils (common in the tropics), and in sandy soils in drylands due to increase in nutrient retention and water holding capacity. Studies report a wide range of plant responses to biochars due to the diversity of biochars and contexts in which biochars have been applied. Crop yields increase strongly if site‐specific soil constraints and nutrient and water limitations are mitigated by appropriate biochar formulations. Biochars can be tailored to address site constraints through feedstock selection, by modifying pyrolysis conditions, through pre‐ or post‐production treatments, or co‐application with organic or mineral fertilizers. We demonstrate how, when used wisely, biochar mitigates climate change and supports food security and the circular economy.

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Section: Biochar's Role In Climate Change Mitigationmentioning

confidence: 99%

How biochar works, and when it doesn't: A review of mechanisms controlling soil and plant responses to biochar

et al. 2021

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“…Though DOC sorption is a fast process, the rate of C sequestration by this mechanism is still limited by the amount of nitrogen and phosphorus required to sequester C as soil organic matter. Recent discussions have pointed out that it would require 593 Tg N year -1 (assuming a soil C:N of 15) and 35-75 Tg P year -1 to achieve the '4 per 1000' goal of sequestering 8.9 Pg C year -1 , the rate of anthropogenic emissions (Davies et al 2020;Spohn 2020). The amount of N required is greater than global natural and anthropogenic nitrogen fixation combined, 413 Tg N year -1 (Fowler et al 2013), and the amount of phosphorus required is a substantial proportion of global phosphate rock mined each year, 240 Tg P year -1 (USGS 2020).…”

Section: Discussionmentioning

confidence: 99%

How much carbon can be added to soil by sorption?

et al. 2021

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Quantifying the upper limit of stable soil carbon storage is essential for guiding policies to increase soil carbon storage. One pool of carbon considered particularly stable across climate zones and soil types is formed when dissolved organic carbon sorbs to minerals. We quantified, for the first time, the potential of mineral soils to sorb additional dissolved organic carbon (DOC) for six soil orders. We compiled 402 laboratory sorption experiments to estimate the additional DOC sorption potential, that is the potential of excess DOC sorption in addition to the existing background level already sorbed in each soil sample. We estimated this potential using gridded climate and soil geochemical variables within a machine learning model. We find that mid- and low-latitude soils and subsoils have a greater capacity to store DOC by sorption compared to high-latitude soils and topsoils. The global additional DOC sorption potential for six soil orders is estimated to be 107 $$\pm$$ ± 13 Pg C to 1 m depth. If this potential was realized, it would represent a 7% increase in the existing total carbon stock.

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“…More recently, N addition was shown to promote microbial decomposition of SOM in an N-limited Tibetan meadow (Du et al, 2020;. The importance of N for C sequestration has drawn increased attention in natural and managed ecosystems since C and N cycles are coupled (Davies et al, 2021;Soares & Rousk, 2019).…”

Section: Drivers Of Soil Dom Molecular Composition and Degradability ...mentioning

confidence: 99%

Patterns and drivers of the degradability of dissolved organic matter in dryland soils on the Tibetan Plateau

Chen

Kong

Shi

et al. 2021

Journal of Applied Ecology

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1. Dryland soils consistently exhibit a low capacity for the long-term accumulation and storage of organic matter, which has been primarily attributed to low plant biomass inputs under drought suppression. Whether, and how, soil organic matter (SOM) compositions contribute to the consistently low SOM storage have been puzzling. A fundamental understanding of this mechanism is particularly essential to achieve the aspiration of '4 per mille Soils for Food Security and Climate'.2. By screening the molecular composition of dissolved organic matter (DOM), the gatekeeper of SOM decomposition, we explored the transformation processes among the pools of SOM, DOM and microbial biomass carbon (MBC) in soils along a precipitation gradient on dryland grasslands of the Tibetan Plateau. 3. The results revealed that the number and mean weight of DOM molecules significantly decreased, and the soil DOM composition gradually shifted to be more labile along the transition from meadow, steppe, to desert with decreasing precipitation, coinciding with the substantial reduction in SOM. Compared with meadow soils, DOM degradability increased by 8.7% in steppe soils and by 23.4% in desert soils. The ratio of soil MBC to total organic carbon was threefold higher in desert than in meadow, and positively correlated with DOM degradability, indicating that labile DOM accelerated microbial growth and SOM decomposition in desert soils. Structural equation model and correlation analyses demonstrated that the DOM degradability was primarily controlled by soil dissolved nitrogen and soil organic C and soil DOC/DN ratio. 4. Synthesis and application. This study at a molecular level provides a novel insight into the important role of the degradability of dissolved organic matter in carbon | 885

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The importance of nitrogen for net carbon sequestration when considering natural climate solutions

Cited by 9 publications

References 11 publications

How biochar works, and when it doesn't: A review of mechanisms controlling soil and plant responses to biochar

How biochar works, and when it doesn't: A review of mechanisms controlling soil and plant responses to biochar

How much carbon can be added to soil by sorption?

Patterns and drivers of the degradability of dissolved organic matter in dryland soils on the Tibetan Plateau

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