Managing plant surplus carbon to generate soil organic matter in regenerative agriculture

Prescott, Cindy E.; Rui, Yichao; Cotrufo, M. Francesca; Grayston, Susan J.

doi:10.2489/jswc.2021.0920a

Cited by 28 publications

(21 citation statements)

References 57 publications

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“…A higher maize productivity for +N compared to -N treatments was found in about half of the treatments of this experiment Laub et al, (in review), so the absence of ±N differences in SOC indicates that aboveground biomass productivity cannot automatically be assumed to translate into belowground inputs. Plants may invest less into roots if they are supplied too well (Prescott et al, 2021). Additionally, Silva-Sánchez et al (2019), studying forest soils, found a reduced microbial carbon efficiency in treatments of mineral N addition.…”

Section: Effect Of Mineral N Fertilizermentioning

confidence: 99%

“…This effectively means that to increase SOC at landscape scale, further agronomic practices that increase primary production and biomass availability, such as intercropping, rotations with grasses or agroforestry practices (Corbeels et al, 2019;Tessema et al, 2020), are needed. Additionally, the focus should be on direct plant inputs from the roots, which is considered the most efficient pathway of SOC buildup (Prescott et al, 2021;. Both roots and root exudates are known to form new SOC with higher efficiency than external organic resource inputs (Rasse et al, 2005;Jackson et al, 2017;, partly due to the fact that microbes can easily assimilate root exudates, which contributes to the formation and stabilization of microbial necromass (e.g.…”

Section: Effect Of Mineral N Fertilizermentioning

confidence: 99%

“…While a recent lab study indicated that geochemistry may be as important as organic resource quality in the formation of new, stable SOC (Bucka et al, 2021), both need to be studied under field conditions. Thus, we are only beginning to understand the fundamental principles behind their interactions and a better understanding of all factors that regulate the microbial processing, stabilization and decomposition of SOC in soils is needed as old paradigms get cast into doubt (Cotrufo et al, 2021). For example, the idea that low-quality organic resources, rich in recalcitrant lignin and polyphenol, lead to more soil organic matter formation than high-quality resources Palm et al (2001a, b) has been replaced by concepts that consider SOC of microbial origin, which favorably forms from high-quality resources, to be the most stable (Cotrufo et al, 2013;Denef et al, 2009).…”

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confidence: 99%

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High quality organic resources are most efficient in stabilizing soil organic carbon: Evidence from four long-term experiments in Kenya

Laub

Corbeels

Couëdel

et al. 2022

Preprint

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Abstract. In sub-Saharan Africa, long-term maize cropping with low external inputs has been associated with the loss of soil fertility. While adding high-quality organic resources combined with mineral fertilizer has been proposed to counteract this fertility loss, the long-term effectiveness and interactions with site properties still require more understanding. This study used repeated measurements over time to assess the effect of different quantities and qualities of organic resource addition combined with mineral N on the change of soil organic carbon concentrations (SOC) over time (and SOC stocks in the year 2021) in four ongoing long-term trials in Kenya. These trials were established with identical treatments in moist to dry climates, on coarse to clayey soil textures, and have been managed for at least 16 years. They received organic resources in quantities equivalent to 1.2 and 4 t C ha−1 per year in the form of Tithonia diversifolia (high quality, fast turnover), Calliandra calothyrsus (high quality, intermediate turnover), Zea mays stover (low quality, fast turnover), sawdust (low quality, slow turnover) and local farmyard manure (variable quality, intermediate turnover). Furthermore, the addition or absence of 240 kg N ha−1 per year as mineral N fertilizer was the split-plot treatment. At all sites, a loss of SOC, rather than gain, was predominantly observed due to a recent conversion from permanent vegetation to agriculture. The average reduction of SOC concentration over 19 years in the 0 to 15 cm depth ranged from 42 % to 13 % of the initial SOC concentration for the control and the farmyard manure treatments at 4 t C ha−1 yr−1, respectively. Adding Calliandra or Tithonia at 4 t C ha−1 yr−1 limited the loss of SOC concentrations to about 24 % of initial SOC, while the addition of saw dust, maize stover (in 3 of 4 sites) and sole mineral N addition, showed no significant reduction in SOC loss over the control. Site specific analyses, however, did show, that at the site with the lowest initial SOC concentration (about 6 g kg−1), the addition of 4 t C ha−1 yr−1 farmyard manure or Calliandra plus mineral N led to a gain in SOC concentrations. All other sites lost SOC in all treatments, albeit at site specific rates. While subsoil SOC stocks in 2021 were little affected by organic resource additions (no difference in 3 of 4 sites), the topsoil SOC stocks corroborated the results for SOC concentrations. The relative annual change of SOC concentrations showed a higher site specificity in high-quality organic resource treatments than in the control, suggesting that the drivers of site specificity in SOC buildup (mineralogy, climate) need to be better understood for effective targeting of organic resources. Even though farmyard manure showed the most potential for reducing SOC loss, our results clearly show that maintaining SOC with external inputs only is not possible at organic resource rates that are realistic for small scale farmers. Thus, additional agronomic interventions such as intercropping, crop rotations or strong rooting crops may be necessary to maintain or increase SOC.

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Section: Effect Of Mineral N Fertilizermentioning

confidence: 99%

Section: Effect Of Mineral N Fertilizermentioning

confidence: 99%

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confidence: 99%

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High quality organic resources are most efficient in stabilizing soil organic carbon: Evidence from four long-term experiments in Kenya

Laub

Corbeels

Couëdel

et al. 2022

Preprint

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“…The presence of such intermediate products could enhance soil microbial activity and the oxygen demand after soil application of the digestate, which can result in oxygen depletion and the consumption of the C provided by the digestate (Huygens et al 2020); even part of the soil OM can be degraded, provoking the so-called "priming effect." This must be taken into account in soil conservation strategies, since soil TOC (or OM) conservation is crucial to ensure good soil fertility and to promote soil conservation (Martín-Lammerding et al 2021;Prescott et al 2021). Thus, digestate composting is recommended over direct soil application for soil C conservation strategies (de la Fuente et al 2013).…”

Section: Discussionmentioning

confidence: 99%

Carbon and Nitrogen Mineralisation in Soils and Nutrient Efficiency of Digestates from Fruit and Vegetable Wastes

Álvarez-Alonso

Clemente

Bernal

2022

J Soil Sci Plant Nutr

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A significant amount of fruit and vegetable wastes is generated annually in markets, supermarkets, restaurants and households. Anaerobic digestion allows their appropriate management and helps to complete the cycle of the circular economy as it converts wastes into resources: biogas, a renewable source of energy, and digestate, rich in nutrients of interest for agriculture. The aim of this study was to define the agronomic value of digestate from fruit and vegetable wastes. Two digestates from fruit and vegetable residues were used in incubation experiments for C and N mineralisation in the soil, and in a pot experiment with crops (cardoon and maize), to calculate their fertiliser potential in comparison with a mineral fertiliser. The digestate quickly mineralised in the soil and nitrification processes led to fast formation of NO3−-N. However, increasing the digestate application rate enhanced N-immobilisation and reduced N-mineralisation in the soil. The addition of digestates to the soil resulted in adequate plant growth and nutrient composition, without any negative effects on the plants or soil. However, special attention should be paid to the salt accumulation in the soil for long-term digestate application. The nutrient recovery efficiency indicated that digestate could replace mineral fertiliser completely in cardoon crops and partially (44.5–82.6%) for maize, with an associated economic benefit. The salinity of the digestates limits their quality and their agricultural use to salt-sensitive crops should be limited.

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“…Many of these activities, such as minimizing soil disturbance due to tillage, retention of crop residues and crop diversification, including cover cropping, are drawn from the practices of conservation agriculture [10][11][12][13]. Others, such as the use of compost and manures, are consistent with a tenet of regenerative agriculture, whereby synthetic fertilizers are replaced by organic materials such as compost and manure [14]. However, such a substitution runs the risk of leakage, which describes the situation where sites from which the organic materials are derived suffer a loss of C inputs.…”

Section: Boxmentioning

confidence: 99%

The Role of Agriculture in the Australian Government’s Emission Reduction Fund

White¹

2022

Adv Environ Eng Res

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Australia’s greenhouse gas emissions from agriculture in 2022 were 67.8 million (M) tonnes (t) of carbon dioxide equivalent (CO2-e), amounting to 12.9% of total emissions. Erupted methane (CH4) from ruminant animals comprised 42% of agricultural emissions. By 2030, the Australian Government aims to reduce total emissions by 43% from the 2005 level. The primary policy instrument for achieving this reduction is the Emissions Reduction Fund (ERF) in which there are two main pathways for agriculture – emission avoidance through suppression of CH4 emissions and soil carbon sequestration (SCS) through approved projects. Although agriculture since 2014 has promised 15.2 Mt of abatement, by April 2022 it has delivered only 1.1 Mt. Examples are given of potential abatement by SCS for pasture and cropping land in different rainfall zones. Methods of suppressing CH4 emissions have yet to be scaled up commercially and proven for grazing animals. The main constraints on SCS are the unreliability of Australian rainfall, the high cost of project management relative to the value of a C credit, and the opportunity cost of maintaining an approved land management for at least 25 years.

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Managing plant surplus carbon to generate soil organic matter in regenerative agriculture

Cited by 28 publications

References 57 publications

High quality organic resources are most efficient in stabilizing soil organic carbon: Evidence from four long-term experiments in Kenya

High quality organic resources are most efficient in stabilizing soil organic carbon: Evidence from four long-term experiments in Kenya

Carbon and Nitrogen Mineralisation in Soils and Nutrient Efficiency of Digestates from Fruit and Vegetable Wastes

The Role of Agriculture in the Australian Government’s Emission Reduction Fund

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