CARBON STOCKS, LITTERFALL AND PRUNING RESIDUES IN MONOCULTURE AND AGROFORESTRY CACAO PRODUCTION SYSTEMS

SUMMARYAgroforestry systems (AFS) can serve to decrease ecosystem carbon (C) losses caused by deforestation and inadequate soil management. Because of their shade tolerance, cacao plants are suitable to be grown in AFS, since they can be combined with other kinds of trees and shrubs. The potential for C sequestration in cacao farming systems depends on various factors, such as management practices, stand structure and plantation age. We compared conventionally and organically managed cacao monoculture systems (MCS) and AFS in Sara Ana (Bolivia) with respect to C stocks in plant biomass and to amounts of litterfall and pruning residues. The total aboveground C stocks of the AFS (26 Mg C ha−1) considerably exceeded those of the MCS (~7 Mg C ha−1), although the biomass of cacao trees was greater in the MCS compared to the AFS. Due to higher tree density, annual litterfall in the AFS (2.2 Mg C ha−1 year−1) substantially exceeded that in the MCS (1.2 Mg C ha−1 year−1). The amounts of C in pruning residues (2.6 Mg C ha−1 year−1 in MCS to 4.3 Mg C ha−1 year−1 in AFS) was more than twice those in the litterfall. Annual nitrogen (N) inputs to the soil through pruning residues of cacao and N-fixing trees were up to 10 times higher than the N inputs through external fertiliser application. We conclude that appropriate management of cacao AFS, involving the pruning of leguminous trees, will lead to increases in biomass, litter quantity and quality as well as soil C and N stocks. Thus, we recommend stimulating the expansion of well-managed AFS to improve soil fertility and enhance C sequestration in soils.

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Carbon stocks in Tasmanian soils

Soil Research ◽

10.1071/sr11211 ◽

2012 ◽

Vol 50 (2) ◽

pp. 83 ◽

Cited By ~ 14

Author(s):

W. E. Cotching

Keyword(s):

Management Practices ◽

Agricultural Soils ◽

C Sequestration ◽

Mean Annual Temperature ◽

Soil C ◽

C Stocks ◽

Initial Soil ◽

If Current ◽

Intensive Cropping ◽

The Difference

Soil carbon (C) stocks were calculated for Tasmanian soil orders to 0.3 and 1.0 m depth from existing datasets. Tasmanian soils have C stocks of 49–117 Mg C/ha in the upper 0.3 m, with Ferrosols having the largest soil C stocks. Mean soil C stocks in agricultural soils were significantly lower under intensive cropping than under irrigated pasture. The range in soil C within soil orders indicates that it is critical to determine initial soil C stocks at individual sites and farms for C accounting and trading purposes, because the initial soil C content will determine if current or changed management practices are likely to result in soil C sequestration or emission. The distribution of C within the profile was significantly different between agricultural and forested land, with agricultural soils having two-thirds of their soil C in the upper 0.3 m, compared with half for forested soils. The difference in this proportion between agricultural and forested land was largest in Dermosols (0.72 v. 0.47). The total amount of soil C in a soil to 1.0 m depth may not change with a change in land use, but the distribution can and any change in soil C deeper in the profile might affect how soil C can be managed for sequestration. Tasmanian soil C stocks are significantly greater than those in mainland states of Australia, reflecting the lower mean annual temperature and higher precipitation in Tasmania, which result in less oxidation of soil organic matter.

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The potential for full inversion tillage to increase soil carbon storage following pasture renewal in New Zealand

10.5194/egusphere-egu2020-13082 ◽

2020 ◽

Author(s):

Mike Beare ◽

Erin Lawrence-Smith ◽

Denis Curtin ◽

Sam McNally ◽

Frank Kelliher ◽

...

Keyword(s):

New Zealand ◽

Management Practices ◽

Management Practice ◽

Mineral Soil ◽

C Sequestration ◽

Atmospheric Concentration ◽

Soil C ◽

C Stocks ◽

Soil C Sequestration ◽

Accumulation Efficiency

The global atmospheric concentration of CO2 and other greenhouse gases (GHG) is steadily increasing. It is estimated that, worldwide, soil C sequestration could offset GHG emissions by 400&#8211;1200 Mt C per year. Relative to 1990, New Zealand&#8217;s CH4 and N2O emissions in 2013 had increased by 7% and 23% respectively, which translates to an annual emission increase of 1.09 Mt C that could be offset by a similar annual increase in soil C stock. Recent research has shown that some New Zealand pastoral soils are under-saturated in SOC. Subsurface soils (15&#8211;30 cm depth) typically have a greater soil C saturation deficit than topsoil (0-30 cm) because plant C inputs (roots) are lower. Using management practices that expose more of the under-saturated soil to higher C inputs could result in increased soil C storage and stabilisation.Pasture renewal (destruction and re-establishment of pasture) is promoted to livestock farmers to improve pasture performance. This typically involves shallow cultivation or direct drilling to establish new grass. Whereas shallow cultivation of soil typically results in a loss of SOC, deeper full inversion tillage (FIT) of soil would result in the burial of C-rich topsoil in closer proximity to mineral material that has a higher stabilisation capacity.&#160; Buried SOC is expected to have a slower decomposition rate owing to less variable temperatures and more anoxic conditions. Deep FIT would also bring under-saturated mineral soil to the surface, where the deposition of SOC from high producing pastures could increase the stabilisation of SOC.&#160; Both the slower turnover of buried SOM and greater stabilisation of new carbon on under-saturated minerals at the soil surface are expected to result in increased SOC sequestration. There is a lack of experimental data to directly address the effect of FIT on soil C stocks in pastoral soils. We applied a simple empirical model to predicting changes in soil C stocks following a one-off application of FIT (30 cm) during pasture renewal. The model accounts for the decomposition of SOC in buried topsoil and the accumulation of C in the new topsoil (inverted subsoil). The model was used to derive national estimates of soil C sequestration under different scenarios of C accumulation efficiency, farmer adoption of FIT and pasture renewal rates.Our modelled estimates suggest that 32 Mt C could be sequestered over 20 years following a one-time application of FIT (0-30 cm) to 2 M ha of High Producing Grasslands on suitable New Zealand soils. This estimate is based on 100% accumulation efficiency (i.e. topsoil C stocks are returned to pre-inversion levels within 20 years) and a 10% annual rate of pasture renewal. In the absence of direct experimental evidence, a more conservative estimate is warranted, where topsoil C stocks are projected to return to 80% of pre-inversion levels, thus sequestering 20 Mt C. This paper will present our modelled estimates of SOC sequestration during FIT pasture renewal and discuss the potential benefits and adverse effects of deploying this management practice.

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Importance of resilient pastures for New Zealand’s agricultural soil carbon stocks

NZGA: Research and Practice Series ◽

10.33584/rps.17.2021.3455 ◽

2021 ◽

Vol 17 ◽

Author(s):

Aaron Wall ◽

Jordan Goodrich ◽

Louis Schipper

Keyword(s):

Soil Carbon ◽

Management Practices ◽

C Sequestration ◽

Co2 Uptake ◽

Soil C ◽

Supplemental Feed ◽

Natural Processes ◽

C Stocks ◽

Soil Carbon Stocks ◽

Below Ground

New Zealand’s agricultural pastures contain significant soil carbon (C) stocks that are susceptible to change when impacted by management and natural processes (e.g., climate). Inputs of C to these pastoral soils is through photosynthetic uptake of atmospheric CO2 either on-site or elsewhere. Changes in soil C stocks are in response to the management of the system that alters the input-output balance. Increasing the resilience of pastures to climatic events such as hot and dry summers or cool and wet winters can increase inputs of C to the soil while sustaining above-ground production and so provide an opportunity for C sequestration. Furthermore, increased pasture for grazing can reduce the need for management practices identified as detrimental for soil C stocks such as irrigation or the production of cropped supplemental feed. A reduction in the need for renewal and its associated soil C losses, and the establishment of a more diverse sward, especially if deeper-rooting species are included, has the potential for increasing soil C stocks provided the diversity can be maintained. From a soil C perspective, a resilient pasture maximises CO2 uptake to ensure adequate above- and below-ground inputs to maintain or increase soil C stocks and minimise the need for management activities detrimental to soil C.

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Modeling Experiments for Evaluating the Effects of Trees, Increasing Temperature, and Soil Texture on Carbon Stocks in Agroforestry Systems in Kerala, India

Forests ◽

10.3390/f10090803 ◽

2019 ◽

Vol 10 (9) ◽

pp. 803

Author(s):

Ann E. Russell ◽

B. Mohan Kumar

Keyword(s):

Soil Texture ◽

Growth Form ◽

C Sequestration ◽

Agroforestry Systems ◽

Individual Factors ◽

Agricultural Systems ◽

Soil C ◽

C Storage ◽

C Stocks ◽

Increasing Temperature

Research Highlights: Agroforestry systems in the humid tropics have the potential for high rates of production and large accumulations of carbon in plant biomass and soils and, thus, may play an important role in the global C cycle. Multiple factors can influence C sequestration, making it difficult to discern the effect of a single factor. We used a modeling approach to evaluate the relative effects of individual factors on C stocks in three agricultural systems in Kerala, India. Background and Objectives: Factors such as plant growth form, management, climate warming, and soil texture can drive differences in C storage among cropping systems, but the relationships among these factors and their effects are complex. Our objective was to use CENTURY, a process-based model of plant–soil nutrient cycling, in an experimental mode to evaluate the effects of individual factors on C stocks in soil and biomass in monocultures (annuals or trees) and agroforestry systems. Materials and Methods: We parameterized the model for this region, then conducted simulations to investigate the effects on C stocks of four experimental scenarios: (1) change in growth form; (2) change in tree species; (3) increase in temperature above 20-year means; and (4) differences in soil texture. We compared the models with measured changes in soil C after eight years. Results: Simulated soil C stocks were influenced by all factors: growth form; lignin in tree tissues; increasing temperature; and soil texture. However, increasing temperature and soil sand content had relatively small effects on biomass C. Conclusions: Inclusion of trees with traits that promoted C sequestration such as lignin content, along with the use of best management practices, resulted in the greatest C storage among the simulated agricultural systems. Greater use and better management of trees with high C-storage potential can thus provide a low-cost means for mitigation of climate warming.

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Balancing litterfall and decomposition in cacao agroforestry systems

Plant and Soil ◽

10.1007/s11104-021-05279-z ◽

2022 ◽

Author(s):

Rika Ratna Sari ◽

Danaë M. A. Rozendaal ◽

Danny Dwi Saputra ◽

Kurniatun Hairiah ◽

James M. Roshetko ◽

...

Keyword(s):

Litter Quality ◽

Production Systems ◽

Nutrient Release ◽

Agroforestry Systems ◽

Soil Protection ◽

Decomposition Rates ◽

Soil C ◽

Pruning Residues ◽

Standing Litter ◽

Underlying Soil

Abstract Backgrounds and aims Litter protects the underlying soil, depending on litterfall and decomposition, but dynamics of the standing litter stock in agroforestry systems remain poorly understood. We aimed to unravel effects of litter quality, temporal patterns, microclimate, and a possible home-field advantage (HFA) on standing litter dynamics across a land-use gradient. Methods We quantified litterfall, the standing litter stock, and microclimate during a year in (remnant) forest, cacao-based simple and complex agroforestry, cacao monocultures, and annual crops in a cacao producing area in Indonesia. We conducted a reciprocal litter transfer experiment, and tested decomposition rates of pruning residues. Standing litter stocks during the year were estimated from monthly litterfall and decomposition rates. Results Variation in litter quality influenced decomposition rates more strongly than variation in microclimate or HFA. Lower litter quality in complex agroforestry and in the cacao monoculture decreased the decay rate compared to simple agroforestry systems; mean litter residence time was over a year. Mixing high- and low-quality material in pruning residues modified the decomposition rate, soil C and N changes, offering options for targeted management of soil protection and nutrient release. Conclusions The seasonal patterns of litterfall and relatively slow decomposition rates supported permanence of the litter layer in all cacao production systems, protecting the underlying soil.

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Effects of Organic Fertilizers on the Soil Microorganisms Responsible for N2O Emissions: A Review

Microorganisms ◽

10.3390/microorganisms9050983 ◽

2021 ◽

Vol 9 (5) ◽

pp. 983

Author(s):

Cristina Lazcano ◽

Xia Zhu-Barker ◽

Charlotte Decock

Keyword(s):

Community Structure ◽

Microbial Community ◽

Best Management Practices ◽

Management Practices ◽

Organic Fertilizers ◽

N2o Emissions ◽

Soil C ◽

Best Management ◽

C Stocks ◽

Denitrifying Microorganisms

The use of organic fertilizers constitutes a sustainable strategy to recycle nutrients, increase soil carbon (C) stocks and mitigate climate change. Yet, this depends largely on balance between soil C sequestration and the emissions of the potent greenhouse gas nitrous oxide (N2O). Organic fertilizers strongly influence the microbial processes leading to the release of N2O. The magnitude and pattern of N2O emissions are different from the emissions observed from inorganic fertilizers and difficult to predict, which hinders developing best management practices specific to organic fertilizers. Currently, we lack a comprehensive evaluation of the effects of OFs on the function and structure of the N cycling microbial communities. Focusing on animal manures, here we provide an overview of the effects of these organic fertilizers on the community structure and function of nitrifying and denitrifying microorganisms in upland soils. Unprocessed manure with high moisture, high available nitrogen (N) and C content can shift the structure of the microbial community, increasing the abundance and activity of nitrifying and denitrifying microorganisms. Processed manure, such as digestate, compost, vermicompost and biochar, can also stimulate nitrifying and denitrifying microorganisms, although the effects on the soil microbial community structure are different, and N2O emissions are comparatively lower than raw manure. We propose a framework of best management practices to minimize the negative environmental impacts of organic fertilizers and maximize their benefits in improving soil health and sustaining food production systems. Long-term application of composted manure and the buildup of soil C stocks may contribute to N retention as microbial or stabilized organic N in the soil while increasing the abundance of denitrifying microorganisms and thus reduce the emissions of N2O by favoring the completion of denitrification to produce dinitrogen gas. Future research using multi-omics approaches can be used to establish key biochemical pathways and microbial taxa responsible for N2O production under organic fertilization.

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Potential soil carbon sequestration of agricultural land around the world

10.5194/egusphere-egu21-3083 ◽

2021 ◽

Author(s):

Sylvia Vetter ◽

Michael Martin ◽

Pete Smith

Keyword(s):

Organic Carbon ◽

Management Practices ◽

Agricultural Land ◽

Ghg Emissions ◽

C Sequestration ◽

Organic Soils ◽

Soil C ◽

Sequestration Potential ◽

The World ◽

Soil C Sequestration

Reducing greenhouse gas (GHG) emissions in to the atmosphere to limit global warming is the big challenge of the coming decades. The focus lies on negative emission technologies to remove GHGs from the atmosphere from different sectors. Agriculture produces around a quarter of all the anthropogenic GHGs globally (including land use change and afforestation). Reducing these net emissions can be achieved through techniques that increase the soil organic carbon (SOC) stocks. These techniques include improved management practices in agriculture and grassland systems, which increase the organic carbon (C) input or reduce soil disturbances. The C sequestration potential differs among soils depending on climate, soil properties and management, with the highest potential for poor soils (SOC stock farthest from saturation).Modelling can be used to estimate the technical potential to sequester C of agricultural land under different mitigation practices for the next decades under different climate scenarios. The ECOSSE model was developed to simulate soil C dynamics and GHG emissions in mineral and organic soils. A spatial version of the model (GlobalECOSSE) was adapted to simulate agricultural soils around the world to calculate the SOC change under changing management and climate.Practices like different tillage management, crop rotations and residue incorporation showed regional differences and the importance of adapting mitigation practices under an increased changing climate. A fast adoption of practices that increase SOC has its own challenges, as the potential to sequester C is high until the soil reached a new C equilibrium. Therefore, the potential to use soil C sequestration to reduce overall GHG emissions is limited. The results showed a high potential to sequester C until 2050 but much lower rates in the second half of the century, highlighting the importance of using soil C sequestration in the coming decades to reach net zero by 2050.

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Reforestation can sequester two petagrams of carbon in US topsoils in a century

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1719685115 ◽

2018 ◽

Vol 115 (11) ◽

pp. 2776-2781 ◽

Cited By ~ 33

Author(s):

Lucas E. Nave ◽

Grant M. Domke ◽

Kathryn L. Hofmeister ◽

Umakant Mishra ◽

Charles H. Perry ◽

...

Keyword(s):

National Level ◽

Mineral Soil ◽

C Sequestration ◽

The United States ◽

Forest Sector ◽

Soil C ◽

C Storage ◽

C Stocks ◽

The Us ◽

Land Use And Management

Soils are Earth’s largest terrestrial carbon (C) pool, and their responsiveness to land use and management make them appealing targets for strategies to enhance C sequestration. Numerous studies have identified practices that increase soil C, but their inferences are often based on limited data extrapolated over large areas. Here, we combine 15,000 observations from two national-level databases with remote sensing information to address the impacts of reforestation on the sequestration of C in topsoils (uppermost mineral soil horizons). We quantify C stocks in cultivated, reforesting, and natural forest topsoils; rates of C accumulation in reforesting topsoils; and their contribution to the US forest C sink. Our results indicate that reforestation increases topsoil C storage, and that reforesting lands, currently occupying >500,000 km2 in the United States, will sequester a cumulative 1.3–2.1 Pg C within a century (13–21 Tg C·y−1). Annually, these C gains constitute 10% of the US forest sector C sink and offset 1% of all US greenhouse gas emissions.

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Organic soil amendments as a tool to increase biological activity and C sequestration in clay soil

10.5194/egusphere-egu21-11965 ◽

2021 ◽

Author(s):

Jussi Heinonsalo ◽

Anna-Reetta Salonen ◽

Rashmi Shrestha ◽

Subin Kalu ◽

Outi-Maaria Sietiö ◽

...

Keyword(s):

Soil Structure ◽

Soil Amendments ◽

C Sequestration ◽

Organic Soil ◽

Plant Production ◽

Soil C ◽

Soil Microbial ◽

Organic Soil Amendments ◽

C Stocks ◽

Soil C Sequestration

Soil C sequestration through improved agricultural management practices has been suggested to be a cost-efficient tool to mitigate climate change as increased soil C storage removes CO2 from the atmosphere. In addition, improved soil organic carbon (SOC) content has positive impacts on farming though better soil structure and resilience against climate extremes through e.g. better water holding capacity. In some parts of the world, low SOC content is highly critical problem for overall cultivability of soils because under certain threshold levels of SOC, soil loses its ability to maintain essential ecosystem services for plant production. Soil organic amendments may increase soil C stocks, improve soil structure and boost soil microbial activities with potential benefits in plant growth and soil C sequestration. Additional organic substrates may stimulate microbial diversity that has been connected to higher SOC content and healthy soils.We performed a two-year field experiment where the aim was to investigate whether different organic soil amendments have an impact on soil microbial parameters, soil structure and C sequestration.The experiment was performed in Parainen in southern Finland on a clay field where oat (Avena sativa) was the cultivated crop. Four different organic soil amendments were used (two wood-based fiber products that were leftover side streams of pulp and paper industry; and two different wood-based biochars). Soil amendments were applied in 2016. Soil C/N analysis was performed in the autumns 2016-2018 and soil aggregate in the summer and autumn 2018, as well as measures to estimate soil microbial activity: microbial biomass, soil respiration, enzymatic assays, microbial community analysis with Biolog &#174;&#160; EcoPlates and litter bag decomposition experiment. The relative share of bacteria and fungi was determined using qPCR from soil samples taken in the autumns 2016, 2017 and 2018.Data on how the studied organic soil amendments influence soil structure and C content, as well as soil microbial parameters will be presented and discussed.

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Site-level simulations of measurable soil fractions with Millennial Version 2

10.5194/ismc2021-19 ◽

2021 ◽

Author(s):

Rose Abramoff ◽

Bertrand Guenet ◽

Haicheng Zhang ◽

Katerina Georgiou ◽

Xiaofeng Xu ◽

...

Keyword(s):

Meta Analysis ◽

C Sequestration ◽

Current Understanding ◽

Century Model ◽

Mineral Association ◽

Microbial Decomposition ◽

Organic C ◽

Soil C ◽

Soil Fractions ◽

C Stocks

Soil carbon (C) models are used to predict C sequestration responses to climate and land use change. Yet, the soil models embedded in Earth system models typically do not represent processes that reflect our current understanding of soil C cycling, such as microbial decomposition, mineral association, and aggregation. Rather, they rely on conceptual pools with turnover times that are fit to bulk C stocks and/or fluxes. As measurements of soil fractions become increasingly available, soil C models that represent these measurable quantities can be evaluated more accurately. Here we present Version 2 (V2) of the Millennial model, a soil model developed to simulate C pools that can be measured by extraction or fractionation, including particulate organic C, mineral-associated organic C, aggregate C, microbial biomass, and dissolved organic C. Model processes have been updated to reflect the current understanding of mineral-association, temperature sensitivity and reaction kinetics, and different model structures were tested within an open-source framework. We evaluated the ability of Millennial V2 to simulate total soil organic C (SOC), as well as the mineral-associated and particulate fractions, using three soil fractionation data sets spanning a range of climate and geochemistry in Australia (N=495), Europe (N=176), and across the globe (N=730). Millennial V2 (RMSE = 1.98 &#8211; 4.76 kg, AIC = 597 &#8211; 1755) generally predicts SOC content better than the widely-used Century model (RMSE = 2.23 &#8211; 4.8 kg, AIC = 584 &#8211; 2271), despite an increase in process complexity and number of parameters. Millennial V2 reproduces between-site variation in SOC across a gradient of plant productivity, and predicts SOC turnover times similar to those of a global meta-analysis. Millennial V2 updates the conceptual Century model pools and processes and represents our current understanding of the roles that microbial activity, mineral association and aggregation play in soil C sequestration.

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