Soils with Smart Carbon

Prof. Genxing Pan1

1Nanjing Agricultural University, Nanjing, China

Enhancement of carbon storage in global soils has been urged as per the “C 4 per mil Initiative”, launched following “the Paris Agreement” for climate change mitigation. However, what kind of carbon should be increased or how the increased carbon could serve soil fertility and ecosystem functioning while mitigate climate change, has been not yet well understood. Global agricultural soils have been depleted organic carbon and therefore have a big potential to feed carbon. Any forms of organic carbon ultimately derived from biomass could help to build up soil C storage but their effects on carbon cycling and food production are widely variable. While to captured or stabilize C in soil, we need carbon to restore soil fertility and soil health and to promote plant growth and food quality, the “Smart C” in agriculture. Such carbon should have stable structure, high reactivity and bioactivity (for example, plant growth/metabolism promotion). Biochar, as an example, is engineered carbon from crop straw and functions in improving soil aggregation/structure, root growth and plant development, and in stabilizing potentially toxic metals, organic pollutants and even pathogenic microbes. The co-benefits to food production, soil/water conservation and environment protection should be assessed and accounted for in the fight against climate change. The characterization, processing and production, and application of smart carbon in agriculture deserve urgent international collaboration, particularly under the framework of “C 4 per mil” action.


Dr Genxing Pan is  a science leader of soil science in Nanjing Agricultural University. He has been devoted his main career to science and technology of soil carbon enhancement in agricultural, particularly of agrochar, in boosting soil C stock and crop productivity for climate change and food

Changes in chemical and thermal indices of soil organic matter stability with time – method validation using a controlled incubation study

Dr Adam Gillespie1, Dr Amanda Diochon2, Dr Omid Haeri-Ardakani3, Dr Ed Gregorich4

1University Of Guelph, Guelph, Canada, 2Lakehead University, Thunder Bay, Canada, 3Geological Survey of Canada, Calgary, Canada, 4Agriculture and Agri-Food Canada, Ottawa, Canada

Soil organic matter stability is thought to be influenced by a combination of physical and chemical constraints.  We have seen relationships between thermal analysis and the carbon mineralization potential of a microbial community1,2,3.  In addition, chemical information obtained using spectroscopic methods (synchrotron-based XANES) can also be used to learn how C is stabilized in soils.  This study shows results of a controlled incubation study4 to track, over time, the changes in thermal stability using Rock-eval pyrolysis and XANES measurements of a soil incubated for the equivalent of 21 months of accumulated crop heat units in the Ottawa area.


Adam Gillespie is a new faculty member at the University of Guelph’s School of Environmental Sciences in Canada.  He is a soil chemist with a research focus on soil organic matter characterization, mapping and modelling. He has a strong interest in using innovative research and instrumentation to link land management with soil health and sustainable land use.

Sole cropping of legumes, resultant soil organic carbon and microbial biomass: A prerequiste to rotational benefit in cropping systems

Dr Ifeyinwa Uzoh1,2, Mr Chukwuebuka  Okolo3, Prof Olubukola Babalola1

1North-west University, Mafikeng, South Africa, Mafikeng, South Africa, 2University of Nigeria, Nsukka, Nigeria, 3Mekelle University, Mekelle, Ethiopia

Crop rotation requires the initial sole cropping particularly legumes as first crops. Therefore, the success of sole crops in improving soil properties determines the beneficial effect of crop rotations. Soil organic carbon and microbial biomass are employed in accessing the effect of crop management on soil properties. This research was conducted for two years in two locations of the derived savanna zone of Nigeria to assess the effect of sole cropping of grain legumes, herbaceous legume and maize on soil organic carbon and microbial biomass carbon, nitrogen and phosphorus. The result showed that soil organic was only significantly (p<0.05%) affected in the second year in Moniya location by the sole crops. Velvet bean had the highest soil organic carbon with 25% improvement of over maize cropping. In the first year, soil microbial biomass N and P were significantly affected in UNN but only soil microbial biomass C in Moniya. In the second year, all the soil microbial biomass fractions were significantly affected by the sole cropping with velvet bean having improved these properties better than other sole crops. More so, 76% and 52% of variations in subsequent maize dry matter and grain yields were explained by soil microbial biomass carbon and nitrogen, and soil microbial biomass carbon respectively.


Soil organic matter distribution governed by aggregation and decoupled from clay content

Mr. Steffen Schweizer1, Ms. Franziska Bucka1, Dr. Markus Graf-Rosenfellner2, Prof. Ingrid Kögel-Knabner1,3

1Soil Science, TU Munich, Freising, Germany, 2Soil Ecology, University of Freiburg, Freiburg, Germany, 3Institute for Advanced Study, TU Munich, Garching, Germany

The accumulation of soil organic matter (OM) through organo-mineral interactions is anticipated to be stimulated by the soil clay content. The mixing of soil particles into larger aggregate structures impedes the identification of which particles comprise the aggregates and how these control the OM distribution. Here we show how the influence of clay content can be resolved based on the underlying impact of size-specific aggregation on OM sequestration. We used dynamic image analysis to differentiate the size distributions of free water-stable microaggregate size fractions (<250 µm) and those occluded in larger soil structures from their dispersible particle-size composition. Differentiating aggregated from dispersed size distributions also enabled to identify the preferential size ranges of aggregates that break down to particles and non-aggregated particles that remain. To investigate the impact of soil texture, we analyzed topsoil samples of an arable site on Cambisol soils with a gradient in clay content within a range of 16–37 %. Our results demonstrate that soil texture governs aggregate distributions and sizes. High-clay soils contain more water-stable macroaggregates (>250 µm) and larger microaggregates in the 50–180 µm size range. Non-aggregated sand-sized particles >100 µm probably impede the buildup of larger water-stable aggregates in low-clay soils. The size distribution of particles <100 µm in size fractions showed a similar prevailing pattern for all clay contents, whereas 4 % more clay-sized particles helped build up water-stable macroaggregates. In the low-clay soils, the aggregates were smaller and had higher OM concentrations. This explains the fact that higher amounts of OM could be held in aggregates of the low-clay soils despite containing coarser texture. This interaction reveals that OM sequestration is decoupled from the particle-size distribution. Instead, the occlusion of aggregate size fractions led to lower alkyl:O/N-alkyl ratios in 13C NMR spectroscopy indicating increased preservation.


Almost-finished PhD student (since December 2015) working on ‘Soil microaggregation and microspatial patterns of organic matter accrual’. Previous to his PhD, he has worked on the impact of organic farming on soil aggregates in Indian Vertisols. Therefore, he’s excited to present his work in the surrounding where the dynamic nature of soil aggregation has been systematically described for the first time.

Nitrogen mineralization related to light-fraction and hot-water extractable carbon in pasture and cropping soils

Mr Tord Ranheim Sveen1, Prof. Deli Chen1, Dr Helen  Suter1

1School of Agriculture and Food, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria 3010, Australia, Melbourne, Australia

Nitrogen mineralization is an essential part of the soil nitrogen cycle, and solid knowledge of mineralization rates is crucial to optimize fertilizer application levels and avoid reactive nitrogen loading into the environment. However, mineralization rates will depend on climate- as well as management factors; most notably temperature, moisture levels and SOM contents. Here, we assessed the rate of nitrogen mineralization in soils of differing properties and land use in Southeast Australia and related these to the soils’ organic matter content through light fraction separation (LFOM) and hot-water extraction (HWC). Soil (0-100mm) was collected from 10 pasture- and 6 continuous cropping systems, with pastures grazed by dairy cows, and cropping systems consisting of 2:1 wheat and canola rotation. Rates of net mineralization were measured at three temperature (10, 20, 30°C) and three moisture levels (air dry, FC, 150% FC), after 14- and 28 days of aerobic incubation. Sampling was conducted at three times over the course of a year to incorporate seasonal differences. Preliminary results indicate soil moisture as the main limiting factor of nitrogen mineralization, with significantly higher mineralization rates in the group of pasture soils at higher levels of moisture conditions. At 150% FC, variation between soils increased for both groups, which is attributed to transient waterlogging conditions. The obtained mineralization rates are to be further correlated to LFOM and HWC.


Tord Ranheim Sveen is a Master’s student at the Office for Environmental Programs, The University of Melbourne. He received his BS (2015) degree from the University of Gothenburg in Sweden. Tord’s general area of interest lies in soil science with agricultural implications, and he is currently finishing his master thesis’ research project on nitrogen mineralisation related to soil organic matter in dairy pasture and cropping soils. After having graduated from his master’s in July 2019, Tord is looking to further deepen his knowledge in the field of soil science and is looking for suitable PhD opportunities.

Methodology to predict nitrogen mineralisation in agricultural soils in New Zealand

Dr Mike Beare1, Dr Denis Curtin1, Mr Craig Tregurtha1, Mr Weiwen Qiu1, Mr Richard Gillespie1

1Plant and Food Research, Lincoln, New Zealand

Improved fertiliser management is critical to lifting the economic and environmental sustainability of agricultural production systems. Forecasting fertiliser N requirements depends on predicting the supply of plant-available N from soil and the demand for that N by crops/pastures during their growth. The nitrogen released by mineralisation of soil organic matter can contribute a large (but variable) amount of plant-available N. Accurately predicting the supply of N from mineralisation remains a key limitation to properly forecasting the amount and timing of fertiliser N additions. Predicting the supply of plant-available N under field conditions requires knowledge of the soil’s N mineralization potential (i.e. N released under “optimal” conditions of temperature and soil moisture) as well as capability to predict how much of that N will actually be mineralised under varying environmental conditions (e.g. soil temperature and moisture). Soil type and management history affect the quality and quantity of soil organic matter that determines the amount of potentially mineralisable N (PMN). PMN is best measured using a longer-term aerobic incubation, but the procedure is laborious and time-consuming. A reliable, “laboratory-friendly” test for soil N mineralization potential is not available; this remains a major barrier to implementation of best management practices for N on farm. This paper will describes recent advances in measuring PMN based on analysis of hot water extractable organic matter from a wide range of soils and land uses across New Zealand. We also describe preliminary results from field validation trials that shows how PMN may be used to predict the supply of plant available N under field conditions.


Relationships between SOM and nitrogen availability

Mr Thomas Carter1, Dr Diane Allen2, Dr Ben Macdonald3, Dr Mark Farrell1

1CSIRO, Agriculture And Food, Urrbrae, Australia, 2DES, Brisbane, Australia, 3CSIRO, Agriculture And Food, Canberra, Australia

Soil organic matter (SOM) is intrinsically linked to nitrogen (N) availability, not only harbouring the majority of soil N as solid organic matter, but also mediating its release and processing by the soil microbial community. Given the recent advances in our understanding of both SOM and N processing over the past 20 years, gaps still exist in our understanding of the role of SOM in N release. Our objective was to build a better understanding of the diversity of N pools and processes in relation to SOM across a broad range of Australian soils of different types and land uses, and to relate this to plant N uptake. A total of 358 topsoil (0-10 cm) samples were collected from 89 sites in Australia, consisting of 13 different land uses. These were measured for pools of N (bulk DON, free amino acid N (FAA-N), nitrate and ammonium) and rates of mineral N and plant available DON production quantified. A subset of 100 soils were selected for a pot experiment to observe plant N uptake. Investigating the different variables measured from the pot experiment showed that the strongest relationship to plant N concentrations was microbial biomass N (r=0.634, P<0.001, n=97). Other factors that played an important role were found to be pH, C:N ratio, FAA-N and DON. When examining relationships between soil C content and the various N pools and rates, surprisingly little direct correspondence was observed (r=0.1771) between total soil C and proteolysis, the main rate limiting step of N production. The relationship between total C and plant N uptake was not much stronger (r=0.2560). These findings indicate that across this diverse range of soils, SOM content has only a small direct influence on plant N availability, and it is likely that other multi-step processes are involved.


Tom Carter is a Research Support Officer at CSIRO with over 10 years experience in a number of methods to quantify soil organic matter and nutrient pools and fluxes. Most recently, he has focussed his expertise in the use of radio-labelled tracers to understand fluxes of low molecular weight compounds such as amino acids and sugars.

Biochar activation by co-application with manure into the soil

Mr Martin Brtnicky1, Mr Oldrich Latal2, Miss Tereza Dokulilova1, Mr Jan Zloch1, Mr Vaclav Pecina1, Mrs Veronika  Janacova1, Mr Jiri Holatko1

1Mendel University In Brno, Brno, , 2Agrovyzkum Rapotin Ltd., Rapotin,

Plain, non-activated biochar applied in the soil affects microorganisms generally negligibly. If it does, biochar changes mostly the community of gram-negative bacteria and actinomycetes. Fungi and gram-positive bacteria are less affected. On the contrary, amendment of manure combined with inorganic fertilizer in the soil significantly increases abundance of all soil microbiota, both bacteria and fungi and among other groups also ammonia oxidizing bacteria (AOB).

We hypothesize that the co-application of inactivated biochar and manure in the soil could enhance positive effects of both amendments on the soil microbial community and other soil parameters.

Therefore, the effect of following variants of biochar, manure and inorganic fertilizer was tested in the pots experiment in greenhouse: 1) control – NPK only, 2) biochar + NPK (15 tons per hectar), 3) manure + NPK (50 tons per hectar), 4) biochar + manure + NPK (15 + 50 tons per hectar). Additional NPK fertilizer – 1) – 4) – was applied according to annual crop nutrient normative. The experiment was carried out on the soil from the topsoil (0-30 cm), collected from Rapotín locality in the Czech Republic, on soil type fluvisol at an altitude of about 345 m a. s. l. The soil in the pots was sown with wheat. The experiment was conducted in 2018.

Application of combined variant manure + biochar + NPK increased abundance of three microbial groups – bacteria, fungi, and AOB – significantly more as compared to both biochar + NPK and manure + NPK. The results showed that activation of biochar by co-application with manure is rather synergic and it exceeds additive effect of sole biochar and sole manure amendments.

This work has been supported by the project of the Technology Agency of the Czech Republic – TH 03030319.


Martin Brtnický  received his degree at Mendel University in Brno in 2005 (Agroecology). He has been interested in the soil science, landscape and ecology.  His research interests include soil quality, soil health, biochar and soil organic mater. He is involved in national research projects about soil quality from National Agency for Agricultural Research and Technology Agency of the Czech Republic. He is coordinator and co-coordinator of 9 projects. Example of projects – TH02030681-  Application of maize,  growing technology using mixed culture for the production of silage for a biogas plant. TH02030169-  Effect of biologically transformed organic matter and biochar application on the stability of productive soil properties and reduction of environmental risks and TH03030319- Promoting the functional diversity of soil organisms by applying classical and modified stable organic matter while preserving the soil’s production properties.

Microhabitat-associated hot spots and hot moments of nitrous oxide emissions (N2O) from floodplain soils

Dr Muhammad Riaz1,2, Dr.  Joerg Luster2, Dr.  Martin Ley2, Mrs. Anais Cattin2, Dr.  Pascal A.  Niklaus3, Dr. Andreas C.  Schomburg4, Dr. Claire Guenat5, Dr. Philip Brunner4, Dr. Moritz Lehmann6

1Department of Environmental Sciences & Engineering, Government College University Faisalabad, Faisalabad, Pakistan, 2Swiss Federal Research Institute WSL, Birmensdorf, Switzerland, 3University of Zurich, Zurich, Switzerland, 4University of Neuchâtel, Switzerland, 5EPFL, Lausanne, Switzerland, 6University of Basel, Switzerland

The relative effects of soil aggregation, plant-soil-earthworm interactions and litter accumulation on the emissions of nitrous oxide (N₂O) from floodplain soils were investigated in a restored section of the Thur River (NE Switzerland). We carried out a manipulation experiment in a frequently flooded and by Phalaris arundinacea dominated zone with loamy sand by comparing separated treatment plots: (i)  control, (ii) vegetaton free, (iii) reduced earthworm population, (iv) combination of (ii) and (iii). In the laboratory we performed a flooding experiment in mesocosms using silty-loamy soil from the Thur floodplains, applying the following treatments: (i) soil 250µm-4mm, (ii) (i) planted with salix viminalis, (iii) (i) mixed with willow leaves, (iv) to (vi) as (i) bis (iii) but soil < 250µm. In the laboratory experiment, the emission of N₂O during the hot moments after flooding was reduced in the planted treatment, very likely due to aeration of the rhizosphere via aerenchyma. In the field experiment, the vegetated plots emitted more N₂O under moist conditions and the hot moments after flooding occurred for a longer period. In this case, probably stimulation of microbial activity by root exudation is the dominant rhizosphere effect. Under dry conditions, the additional drying effect due to plant water uptake leads to lower N₂O emissions from plots with vegetation. According to the laboratory experiment, the formation of large aggregates increases the intensity of the hot moments during the drying phase after a flood probably due to the development of good conditions for coupled nitrification – denitrification. A local increase in litter-associated C availability appears to lead to a further increase of N²O production only under concurrent protection in large aggregates. Temporary lower emissions from field plots with earthworms suggest that in sandy soils the aeration effect of earthworm activity is larger than the one on aggregate formation.


Dr. Muhammad Riaz is working as an Associate Professor in the Department of Environmental Sciences & Engineering, Government College University Faisalabad (GCUF), Pakistan. He earned his PhD in Environmental Sciences from the University of York, UK. His research is mainly focused on soil biogeochemistry, CNP cycling in agroecosystems, biochar as a tool for soil C sequestration and soil quality management, and dynamics of soil organic matter cycling and recycling in semi-arid and arid agroecosystems.

Topsoil water repellence increased early wheat growth and nutrition

Mr Simon Yeap1, Professor Richard Bell1, Dr Craig Scanlan2, Professor Richard Harper1

1Murdoch University, Murdoch, Australia, 2Department of Primary Industries and Regional Development, Northam, Australia

Soil water repellence, derived from the accumulation of hydrophobic organic compounds, is a constraint to crop and pasture production worldwide predominantly in sandy soils. Inhibited water infiltration, unstable wetting, and preferential flow are key hydrologic issues in water-repellent soil which adversely affect plant germination and establishment. However, despite the general understanding that soil water repellence can reduce soil nutrient bioavailability due to the prevalence of dry topsoil, the implications of water-repellent topsoil for plant growth and nutrition per se are unclear. A controlled glasshouse study was conducted to assess early growth and nutrition responses to severe topsoil water repellence in wheat (Triticum aestivum cv. Mace) over 51 days, under uniform plant density (15 plants per container), variable topsoil thickness (20 or 100 mm), and limited water supply (4.2 mm every two days). Wheat grown in severely repellent topsoil treatments with a wettable furrow had significantly greater tiller number per plant, dry matter, and total nutrient uptake compared to plants grown in completely wettable topsoil treatments, regardless of topsoil thickness. Preferential flow in the furrow of repellent topsoil treatments presumably increased soil water availability at depth, but did not cause leaching beyond treatment containers, resulting in conditions conducive to early wheat growth and nutrient uptake. By contrast, increased retention of water at the surface of completely wettable topsoil treatments likely decreased plant-available water due to a reduction in wetting depth and an increased rate of evaporative water loss. Increasing the thickness of wettable topsoil from 20 to 100 mm also significantly reduced wheat growth and nutrient uptake, but topsoil thickness was not important in repellent topsoil treatments. This suggests that preferential flow along a wettable furrow in water-repellent soil can be advantageous for early plant growth and nutrition by improving water capture and plant water uptake under a limited supply.


Simon Yeap is a PhD candidate in agricultural science at Murdoch University and holds a Bachelor of Science in Environmental Science and Environmental Technology, with Honours in Environmental Science. Simon’s main research interest is in the agronomy of sandy soils.

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