Amendments with humified compost effectively sequester organic carbon in agricultural soils

Abstract

Preventing degradation of soil quality and productivity entails development of sustainable practices to enhance soil organic matter. We followed soil organic carbon (OC) accumulation during 3 years long‐field experiments in two different Italian soils under conventional tillage (TRA), reduced tillage (MIN), green manure (GM) and two rates (low, CMPL, and, high, CMPH) of mature compost amendments. Despite soil textures differences, CMP additions enhanced in both field sites OC accumulation in either bulk soils or water‐stable aggregates (WSA), especially for CMPH, that was more pronounced than for MIN and GM. While the sum of OC in WSA showed an average retention of 80–90% of cumulative carbon added with compost, incorporated OC in WSA of MIN and GM reached only 26 and 55% of total carbon amended with fresh biomass for the light and heavy textured soils, respectively. Hence, MIN and GM accumulated SOC only up to the physical saturation limit dictated by soil texture, whereas CMP retained a larger additional SOC than TRA due to hydrophobic affinity among apolar domains progressively added to soil with humified compost. Nuclear magnetic resonance spectra of humus extracted after the first and third treatment year confirmed this behaviour. While no changes were observed in spectra for MIN and GM, humic extracts from CMP showed significantly larger content of apolar alkyl and aromatic moieties after the third experimental year. Our results suggest that soil amendment with well humified compost is an effective practice to sequester carbon into agricultural soils, besides improving their organic fertility.

Organic Amendments and Sampling Date Influences on Soil Bacterial Community Composition and Their Predictive Functional Profiles in an Olive Grove Ecosystem

“…At the same time, the enzymes related to organic carbon mineralization, i.e., K05349 (beta-glucosidase [EC: 3.2.1.21]) and K15371 (glutamate dehydrogenase (GDH2) [EC: 1.4.1.2]), decreased. These results showed that the soil management under rainfed conditions proposed in this study (i.e., compost amendment and incorporation of weed biomass in an olive grove) affected some pathways of soil metabolism and environmental information processing in a manner comparable to that evidenced by other authors and for conservation management [54,55], promoting the humification of both exogenous and natural organic carbon [56]. Finally, we did not find significant differences in the global metabolic pathways related to the P cycle (K01113_K01077_alkaline phosphatase).…”

Chemistry and Associations of Carbon in Water-Stable Soil Aggregates from a Long-Term Temperate Agroecosystem and Implications on Soil Carbon Stabilization

“…37 The substitution of compost at the latter stage of the experiment may have added more stable forms of C. The addition of humified compost is an effective strategy to store C in agricultural soils. 38 Even though the biochemical recalcitrance of the compost is unknown, 7 the added compost (after 2000) may have played a significant role in increasing SOC. Previous research from the studied agroecosystem, indicated that the organic additions (1992−2014) resulted in an increase of 65% and 228% in SOC in tilled and no-till soils (0−5 cm depth), respectively.…”

Validation and comparisons of NaOH and Na4P2O7 extraction methods for the characterization of organic amendments

“…Humified mature composts were observed to promote the stability of SOM in agricultural soils and significantly increased the content of non-polar alkyl and aromatic moieties after 3 years of application (Spaccini and Piccolo, 2020). Spaccini et al (2019) reported that the biochemical stability of ligno-cellulose residues from biorefinery wastes was similar to that found for the persistent fraction of SOM.…”

“…For example, organic amendments rich in alkyl and N‐alkyl groups improved soil organic C (SOC) content and accelerated macroaggregation in soils (Yu et al., 2015). Humified mature composts were observed to promote the stability of SOM in agricultural soils and significantly increased the content of nonpolar alkyl and aromatic moieties after 3 yr of application (Spaccini & Piccolo, 2020). Spaccini et al.…”