Increased Soil Organic Carbon Content Research Articles

Growth and Yield of Okra Using Bio-Stimulant of Golden Apple Snails Extracts and Fertilizer on Ultisol

Cultivation of okra on ultisol soils having poor physical, chemical and biological soil properties can be improved by administering a bio-stimulant extract of golden snails and combined with NPK fertilizer. This research objective was to study a combination of bio-stimulant treatment of golden apple snail extract and NPK fertilizer dosage in increasing the growth and yield of okra on ultisol soil. This study used a factorial completely randomized design with two factors. The first factor was Bio-stimulant golden apple snails extract consisting of 4 treatment, and the second factor was levels of NPK fertilizer consisting of 3 treatment. Fertilizers had a significant effect on increasing overall plant growth. The bio-stimulant extracts of golden apple snails contain organic materials that can improve physical properties (increasing aggregation, moisture retention, soil hydraulic conductivity), chemical (increasing soil organic carbon content) and biology (increasing soil microbial biomass). The nutrient content in NPK fertilizers can increase nutrients; the availability of nutrients in the soil is balanced and can be absorbed by plants so that the photosynthesis process in plants can run well and increase on growth and yield of okra. The combination of bio-stimulant extract of golden apple snails of 20 mL/L water and NPK fertilizer of 150 kg/ha (1 g/polybag) had the highest resulted in the average value of growth and yield of okra on the ultisol soils.

Phytoavailability of Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Tl and Zn in Arable Crop Systems Amended for 13 to 15 Years with Organic Waste Products

Repeated applications of organic waste products (OWP) are a source of trace elements (TE) inputs to agricultural topsoils. The present study aimed at (i) assessing the effects of repeated OWP inputs on the chemical properties of topsoils in two long-term field experiments (13 and 15 years; calcareous and non-calcareous soils), (ii) evaluating TE phytoavailability and their transfer to grain (winter wheat and maize) and (iii) identifying the underlying factors causing alterations of TE phytoavailability. In both field experiments, receiving compliant or slightly high doses of OWP in compliance with regulations, OWP and soil physicochemical properties and TE concentrations in soils and grains were determined. In situ phytoavailability of TE was assessed at two juvenile crop growth stages by analyzing TE concentrations in shoot plantlets. Depending on the OWP input amount, results showed that compared to the soil receiving no organic amendment, repeated OWP inputs significantly increased soil organic carbon content, pH, cation exchange capacity, total soil Cu, Mo and Zn concentration and the phytoavailability of Mo, while the phytoavailability of Cd, Mn, Ni and Tl was significantly reduced. No notable effect was observed for Cr, Cu, Hg, Pb and Zn phytoavailability. Statistical approaches suggested that due to the repeated OWP applications, increased soil organic carbon content and pH, were likely responsible for decreased TE phytoavailability (e.g., Cd).

Soil organic carbon is affected by organic amendments, conservation tillage, and cover cropping in organic farming systems: A meta-analysis

Meta-analysis is often used to compare how soil health differs between organic and conventional farming systems. However, the burgeoning primary literature on organic farming now allows direct evaluation of the best management practices (BMPs) within organic farming systems on soil health improvements. Therefore, the main objective of this meta-analysis was to investigate the effect of BMPs, such as organic amendments, conservation tillage, and cover cropping, on soil health within organic farming systems. We focused on two principal soil health metrics: soil organic carbon (SOC) and microbial biomass carbon (MBC) concentrations. On average, adoption of BMPs increased depth-weighted SOC and MBC concentrations by 18 and 30 %, respectively, relative to organically-managed control groups. Among BMPs, organic amendments and conservation tillage practices showed net positive effect on soil health with 24 and 14 % increase in depth-weighted SOC concentrations, respectively. Although cover cropping did not have an overall influence on SOC concentrations, we found a temporal trend such that cover cropping significantly increased SOC concentrations after 5 years of its adoption. This indicates that the soil health benefits from BMPs accrue over time and highlights the need of long-term adoptability of BMPs to achieve agricultural sustainability. Future primary articles that focus on under-researched cropping practices in organic systems (e.g., crop rotation length and diversity, biochar addition) and the additive effects of multiple BMPs on soil health, will add to the synthesizable evidence base. Therefore, this meta-analysis confirms the soil health benefits of adopting BMPs within organic farming systems, identifies critical knowledge gaps, and provides directions for future organic farming research.

Effects of long-term fertilizer management on soil labile organic carbon fractions and hydrolytic enzyme activity under a double-cropping rice system of southern China.

Fertilization is an effective way to improve soil quality, increase soil fertility and soil microbial diversity in paddy soil. To explore the changes of soil labile organic carbon (C) fractions and hydrolytic enzyme activity after 34 years fertilization treatments in a field experiment in double-cropping rice system of southern China. There were four treatments, including chemical fertilizer alone (MF), rice residue and chemical fertilizer (RF), 30% organic matter and 70% chemical fertilizer (OM), and the control without fertilizer input (CK). We measured soil organic carbon (SOC) content, soil labile organic C fractions, SOC related hydrolytic enzyme activity, correlation coefficients of soil enzyme activity with SOC content and its labile organic C fractions. The results showed that MF, RF and OM increased SOC content by 4.5%, 22.4% and 53.5%, respectively. Compared with MF and CK, RF and OM increased soil labile organic C fractions [cumulative C mineralization (Cmin), permanganate oxidizable C (KMnO4-C), particulate organic C (POC), dissolved organic C (DOC), light fraction organic C (LFOC), microbial biomass C (MBC)] and the proportion of each labile organic C fractions to total organic C. The contents of Cmin, KMnO4-C, POC, DOC, LFOC and MBC under OM treatment were 3.5, 3.1, 3.7, 1.9, 1.2 and 1.9 times higher than CK treatment, respectively. The proportion of labile organic C fractions to total organic C of RF and OM treatments was significantly higher than that in CK. The order of soil hydrolytic enzyme activity [α-glucosidase (αG), β-glucosidase (βG), β-xylosidase (βX), cellobiohydrolase (GBH), and N-acetyl-β-glucosaminidase (NAG)] was OM>RF>MF>CK. The soil hydrolytic enzyme activity under OM treatment increased by 111.8%, 14.1%, 127.3%, 285.6% and 91.4% compared with CK, respectively. Furthermore, RF and OM treatments were beneficial to soil peroxidase (POD) activity. MF treatment was beneficial to soil polyphenol oxidase (PPO) activity. There was a significant positive correlation between soil hydrolytic enzyme activity and SOC content and its labile organic C fractions. In conclusion, the combined application of organic manure, rice straw returning and chemical fertilizer is an effective method to improve soil labile organic C fractions and hydrolytic enzyme activity in a double-cropping rice paddy field of southern China.

Effects of aboveground and belowground litter inputs on the balance of soil new and old organic carbon under the typical forests in subtropical region.

Litter is one of the most important factors controlling the accumulation, stabilization, and turnover of soil organic carbon (SOC) in forests. There is a knowledge gap of the impacts of aboveground and belowground litter inputs on the balance of new and old SOC under different forests in subtropical region. We examined the effects of aboveground and belowground litter inputs on SOC turnover using isotopic tracing technique, based on a 3-year C3 plants/C4 soil replacement experiment in natural forest (NF), Masson pine (Pinus massoniana) plantation (PM) and Chinese fir (Cunninghamia lanceolata) plantation (CL). Our results showed that forest types, litter treatments, and sampling time significantly affected SOC contents, δ13C, new and old SOC contents. Moreover, there were significant interactions between forest types and litter treatments. Litter input increased SOC content and net SOC increment, with higher sensitivity of NF than CL. Litter inputs decreased soil δ13C, with lower values in NF and PM compared to CL. For PM, the new SOC content in belowground litter treatment was significantly higher than that in aboveground litter treatment. The contents of old SOC were lower in belowground litter treatment than aboveground litter treatment in the NF and CL. Above- and below-ground biomass were positively correlated with SOC content and net increment. Belowground litter biomass were positively correlated with soil C/N ratio and new SOC content. Our results implied that belowground litter input had stronger effects on SOC turnover compared to aboveground litter input, with the effects varying among different forests. Our results provided new information on SOC accumulation and on sustainable management of the typical forests in subtropical region.

Effects of experiment duration on carbon mineralization and accumulation under no-till

Conservation tillage incorporating no-till (NT) is often recommended to reduce soil organic carbon (SOC) mineralization and sequester SOC, thus mitigating carbon dioxide production. The rates of SOC accumulation and mineralization are significantly affected by the time since the introduction of NT, however, there is currently poor understanding of exactly how rates change over time under long-term NT. Thus, an 11-year field experiment, a 60-day laboratory incubation, and a meta-analysis were used to better understand the effects of NT, experiment duration, and their interaction on SOC accumulation and mineralization. Our field experiment showed that, compared with plow tillage (PT), NT had a higher proportion of more stable SOC fractions and significantly increased SOC concentration by 12.6 % in the 5th year of the field experiment, and 52.2 % in the 11th year. A significant interaction between tillage and experiment duration was observed for SOC mineralization using laboratory incubation. NT decreased bulk SOC mineralization by 20.1 % in the 5th year of the field experiment and by 44.8 % in the 11th year when compared with PT. This was associated with an increase in SOC concentration and a decrease in SOC mineralization from macro-aggregates (>2 mm) over time and thus the accumulation of SOC was attributed to the physical protection of SOC within macro-aggregates. Meta-analysis confirmed these results and found that, compared with PT, NT significantly decreased SOC mineralization by ∼11 % when experiment duration was ≤8 years and by ∼27 % when it was 8–16 years (P < 0.05). This indicated that SOC mineralization was reduced in NT to an increasing degree as experiment duration increased and additional SOC could be sequestered with an experiment duration of up to 16 years.

Space-time monitoring of soil organic carbon content across a semi-arid region of Australia

Monitoring and mapping organic carbon throughout the soil profile is an important task, as land management and fluctuations in rainfall patterns have the potential to substantially alter the levels of soil organic carbon (SOC). This study aims to monitor the change in SOC content between 2002 and 2015 in a semi-arid, irrigated cotton-growing region in Australia under various land uses. One multivariate linear mixed model (MLMM) was used to model SOC content with four response variables – at two sampling depths (0–0.1, and 0.3–0.5 m), and two time points (2002 and 2015). This involved a four-dimensional model (horizontal and vertical space, and time) to monitor the spatio-temporal shifts of SOC content. Such a model utilises the correlation between the four measurements of SOC at the different depths and times. When tested with leave-one-site-out cross-validation, SOC content was predicted with a Lin's concordance correlation coefficient (LCCC) of 0.68, and a root mean square error (RMSE) of 0.21%. The MLMMs produced coherent soil maps, and an ability to detect statistically significant change in SOC content over time. While no change in subsoil (0.3–0.5 m) SOC content was observed across the study area, a small section of the study area revealed a statistically significant increase in SOC content in the topsoil (0–0.1 m). It was not completely clear whether this change was a function of land management, or the extended wet period from 2010 to 2012. The ability of MLMMs to take advantage of the relationship between different soil properties, soil depths, and time points, makes them advantageous for spatio-temporally monitoring soil.

Biochar-compost addition benefits Phragmites australis growth and soil property in coastal wetlands

Salinity stress is common for plants growing in coastal wetlands. The addition of biochar in the soil may alleviate the negative effect of salinity through its unique physicochemical properties. To test this, we conducted a greenhouse experiment where the cosmopolitan wetland plant Phragmites australis was subjected to four salinity treatments (0, 5, 10 and 15‰) and three biochar treatments (no biochar addition, with biochar addition and with biochar-compost addition, both biochar and compost were made from P. australis) in a factorial design. Both biochar addition and biochar-compost addition to the substrate enhanced belowground mass of P. australis, application of biochar-compost significantly increased total mass by 35.5% and net photosynthesis rate of P. australis by 51.4%. Both biochar addition and biochar-compost addition significantly increased soil organic carbon content by 62.9% and 31.7%, respectively, but decreased soil ammonium nitrogen content. In the saline soil, application of the mixture of biochar-compost had a strong, and positive effect on the growth of P. australis, compared to biochar alone. Therefore, incorporation of biochar and compost might be an appropriate approach to improve the productivity of P. australis growing in coastal wetlands, where soil salinity is a common environmental stress.

Higher soil organic carbon accumulation in the subsoil layer by 37 years combined application of inorganic fertilizers with manure than with rice straw in a double-rice paddy soil

ABSTRACT Organic incorporation is widely recommended to increase Soil Organic Carbon (SOC) content, but little was done to compare the effects of using manure and straw in different soil layers. The study was set up to assess the changes of SOC and oxidizable organic carbon fractions in three soil depths (0–15, 15–30 and 30–45 cm) in a double-rice paddy field subjected to 37 years fertilization schemes [control (CK), combined inorganic fertilization (NPK), inorganic fertilizer NK with pig manure (NKM), and inorganic fertilizer NP or NPK incorporated with rice straw (NPS and NPKS)]. The 37 years’ application of NPK, NKM, NPS and NPKS increased SOC content up to 16.5%, 38.7%, 24.4% and 24.2% across the three soil depths, respectively, compared with CK. Both NPS and NPKS treatment had 77% higher SOC accumulation by sequestering more labile SOC fraction (CHL) in topsoil but not the subsoil layers compared with NPK. Long-term NKM application performed best in SOC accumulation (threefold higher compared with NPK) in all studied soil depths, and in the content of CHL in topsoil. Overall, the integration of inorganic fertilizer with organic manure is more effective than straw incorporation on improving SOC accumulation and stability in not only the topsoil but also the subsoil layers.

The influence of tree species on soil organic carbon stability under three temperate forests in the Baihua Mountain Reserve, China

Soil organic carbon (SOC) is an important component of the carbon (C) cycle in forest ecosystems, and is largely influenced by tree species. Leaf litter originated from different vegetations introduce organic materials into soil with different quantities and qualities, and influence the formation and stability of soil C pool. We present a study on the influence of tree species on SOC stability under three temperate forests: pine (Pinus tabuliformis Carr.), larch (Larix principis-rupprechtii Mayr.) and birch (Betula dahurica Pall.) in the Baihua Mountain Reserve. The SOC and permanganate oxidizable C (POXC) concentrations in the 0–5, 5–10, 10–20 and 20–30 cm soil layers were determined. The SOC stability was evaluated by analyzing the chemical composition of SOC and the distribution of organic C in soil particle-size fractions under different tree species. The birch forest had significantly higher SOC and POXC concentrations than pine and larch in all the four soil layers. These differences might be partly related to the altitude, and also caused by the differences in litter characteristics between birch and the two coniferous species. The organic C was enriched in clay-sized fraction in birch forest soil, but showed higher concentrations in coarse sand fraction (2000-250 μm) under pine, suggesting a higher potential of birch forest for C accumulation in stable SOC pools. The chemical composition of SOC was determined by solid-state 13C nuclear magnetic resonance (NMR) spectra and showed that the birch forest soil had higher alkyl C/O-alkyl C, aromatic C/O-alkyl C and hydrophobic C/hydrophilic C ratios than pine and larch forest soils in the top 5 cm soil layer, reflecting a more recalcitrant SOC composition under birch than under pine and larch. We concluded that the birch forest could not only increase SOC concentration in mineral soils but also had a higher potential to accumulate C in stable soil C pools, and thus is more beneficial to SOC stabilization than the pine and larch forests. This study highlights that future strategy of tree species selection needs to consider the potential effects of tree species on the stability in addition to the concentration of SOC.

Aggregate-associated soil organic carbon dynamics as affected by erosion and deposition along contrasting hillslopes in the Chinese Corn Belt

Soil erosion and deposition processes act as key drivers of soil organic carbon (SOC) translocation and transformation, resulting in a spatially heterogenous distribution of SOC in terms of its quantity and composition. Soil aggregation and its interactions with geomorphic processes exert significant control over SOC dynamics, particularly in landscapes that are undergoing accelerated soil erosion. Here, we investigated the combined effects of erosion-induced soil redistribution and pedogenesis on aggregate-associated SOC dynamics in the sloping croplands of the seriously eroded, yet under-studied, Chinese Corn Belt, by conducting aggregate size fractionation and size-specific stable C isotope analyses. Soil samples from three depth intervals were taken at Summit, Mid-slope and Bottom-slope positions of two contrasting hillslopes, one located in Jiutai (JT) characterized by SOC-rich Chernozems and the other in Helong (HL) with poorly-structured sandy Luvisols. Results show that erosion-induced preferential redistribution of fine particles was found consistently in JT and HL, resulting in an elevated percentage of clay + silt sized particles and concurrent enrichment in SOC content at the Bottom-slope locations. As revealed by the δ13C signature, the loss of SOC at Mid-slope was accompanied by a higher degree of 12C depletion in soil organic matter, particularly in the micro- and macroaggregate fractions, indicating that young and labile SOC previously associated with these fractions was released during the breakdown of soil aggregates by erosive forces and subsequently redistributed to the Bottom-slope position. Comparing the two soil types, the JT site had a hierarchical aggregate structure and increasing SOC concentration with aggregate size, while the opposite pattern was found at the HL site due to the high percentage of primary sand particles in the coarser fractions. This highlights the important control of pedogenesis over soil aggregation and that its interactions with erosion processes greatly affect SOC storage in eroding landscapes, requiring targeted conservation practices to prevent excessive SOC loss.

Influence of 9 years of permanent raised beds and contour furrowing on soil health in conservation agriculture based systems in Tigray region, Ethiopia

AbstractConservation agriculture (CA) systems represent a set of three soil management principles: minimarbance, permanent soil cover and crop rotations ‐ whereas the CA‐based systems in this study add the bed and furrow tillage techniques as integral elements of CA. Studies on the effects of long‐term CA‐based systems on soil health and crop productivity are rare globally, particularly in Ethiopia. This study aimed at investigating the long‐term (2005–2013) influence of CA‐based systems on soil health and crop productivity in northern Ethiopia. The treatments we used include two types of CA‐based systems (permanent raised bed PRB and contour furrowing CF) and conventional tillage (CT) arranged in a randomized complete block design. Soil samples were collected at 0–10 cm soil depth to assess soil health. Piecewise structural equation modeling (PSEM) was used to analyze linkages between management practices, soil health and crop productivity. Arbuscular mycorrhizal fungi spore abundance and root colonization was higher in PRB followed by CF compared to CT (p &lt; 0.05). Significantly different soil N of 1.4 and 0.9 g kg−1 and available P of 6.7 and 4.1 ppm were recorded for PRB and CT, respectively. Higher straw and grain yield of 12 and 4.3, 10 and 3.5, 8 and 2.8 t ha−1 were recorded for PRB, CF and CT, respectively. Outputs of the PSEM highlighted two pathways in which CA‐based systems contributed to improved productivity: (a) via higher density of bacteria and improved hydraulic conductivity, and (b) via higher density of fungi and increase soil organic carbon content in the topsoil. The study concludes that CA‐based systems have the potential to improve crop productivity through improved soil health.

Impact of surface soil manuring on particulate carbon fractions in relevant to nutrient stoichiometry in a Mollisol profile

Organic matter application significantly influences soil carbon storage and sequestration in cropland. The investigation of C sequestration through soil organic carbon (SOC) fractions in the soil profile and its relation to nutrient stoichiometry are essential for evaluating the effect of farming practice on soil fertility. This study aimed to examine the effect of cattle manure application on nutrient stoichiometry, which would be associated with soil C stock in SOC fractions, such as microbial biomass C (MBC), dissolved organic C (DOC) and water-soluble organic C (WSOC), coarse particulate organic carbon (cPOC), fine particulate organic carbon (fPOC) and the mineral-associated organic carbon (MOC). A four-year manure application experiment was conducted in a Mollisol, in which fertilization treatments comprised (1) NoF: the non-fertilizer control, (2) F: synthetic fertilizer, i.e. 20.3, 21.2 and 12.2 kg ha−1 of nitrogen (N), phosphorus (P) and potassium (K) in soybean, and 69.0, 28.1 and 6.1 kg ha−1 of N, P and K for corn on an annual basis, respectively, (3) F + M: synthetic fertilizer plus 15 Mg ha-1 of cattle manure and (4) F + 2M: synthetic fertilizer plus 30 Mg ha−1 of cattle manure in a soybean-corn rotation. SOC concentration in top 10 cm of soil was 18 % and 19 % higher under F + M than that under NoF and F, respectively. Whereas, F+2 M significantly increased SOC concentration by 32 %, 32 %, 14 %, and 11 % in 0−10, 10−20, 20−30, and 30−40 cm of soil depth compared to that in respective soil depth under NoF. Compared to NoF and F, manure application (F + M and F+2 M) significantly increased MBC in the top 30 cm of soil depth and DOC concentration in the top 20 cm of soil depth, but significantly decreased WSOC concentration in the top 20 cm of soil depth. F+2 M significantly increased cPOC concentration in the top 30 cm of soil depth compared to NoF and F. F + M significantly increased fPOC concentration in the top 50 cm of soil depth, compared to NoF, and F. F+2 M further increased the fPOC concentration in the top 30 cm of soil depth, compared to F + M. There was no difference among fertilization treatments in MOC concentration in any soil depth. There were significant exponential correlations of C concentration in POC fractions with soil N, P and N/P ratio. These results indicate that the combination of manure and synthetic fertilizer increased C accumulation in the POC fraction especially in the top 30 cm of soil depth. The change of nutrient stoichiometry was responsible to the accumulation of soil organic matter, highlighting that N, rather than P mainly regulated C accumulation in POC. Increasing input of N fertilizer combined with manure application would benefit the formation of soil organic matter in agricultural Mollisols.

The Invasion of Alternanthera philoxeroides Increased Soil Organic Carbon in a River and a Constructed Wetland With Different Mechanisms

Wetlands have been considered as a vital reservoir of global carbon and are vulnerable to plant invasion. However, the influence mechanism of plant invasion on soil organic carbon (SOC) in wetlands remains unclear. In this study, we investigated SOC, soil physicochemical properties, and soil microbes in the invaded and non-invaded sites in Xinxue River and Xinxue River Constructed Wetland to research the effects of Alternanthera philoxeroides invasion on SOC and explore the related mechanisms. The invasion of A. philoxeroides increased SOC content and density in both the river and the constructed wetland. SOC in the two types of wetlands was positively correlated with moisture content and negatively correlated with bulk density, dissolved oxygen, water temperature, soil temperature, and pH. The invasion decreased the dissolved oxygen in the river and the soil temperature in the constructed wetland which might be the explanation for the increase of SOC in the two types of wetlands. In the river, the decrease of dissolved oxygen caused by plant invasion could alter the microbial community and limit the decomposition of SOC by microbes, which was confirmed by the increase of microbial α diversity indices and the correlations between soil microbial community in the river and dissolved oxygen showed by RDA analysis. The invasion of A. philoxeroides significantly shifted the soil microbial community in the constructed wetland. Redundancy analysis showed that the variation of soil microbial community structure in the constructed wetland could be mainly explained by soil pH and soil temperature. The decrease of soil temperature in the constructed wetland might inhibit microbial activities and result in the accumulation of SOC. In addition, the indicator species reflecting soil microbial community shifted by plant invasion were highly correlated with SOC, suggesting that the variation of indicator species between invaded sites and non-invaded sites might be another reason for the difference in SOC. The study indicates that A. philoxeroides invasion might increase the carbon storage in rivers and constructed wetlands with different mechanisms.

Corn straw return can increase labile soil organic carbon fractions and improve water-stable aggregates in Haplic Cambisol

Corn straw return to the field is a vital agronomic practice for increasing soil organic carbon (SOC) and its labile fractions, as well as soil aggregates and organic carbon (OC) associated with water-stable aggregates (WSA). Moreover, the labile SOC fractions play an important role in OC turnover and sequestration. The aims of this study were to determine how different corn straw returning modes affect the contents of labile SOC fractions and OC associated with WSA. Corn straw was returned in the following depths: (1) on undisturbed soil surface (NTS), (2) in the 0–10 cm soil depth (MTS), (3) in the 0–20 cm soil depth (CTS), and (4) no corn straw applied (CK). After five years (2014–2018), soil was sampled in the 0–20 and 20–40 cm depths to measure the water-extractable organic C (WEOC), permanganate oxidizable C (KMnO4-C), light fraction organic C (LFOC), and WSA fractions. The results showed that compared with CK, corn straw amended soils (NTS, MTS and CTS) increased SOC content by 11.55%–16.58%, WEOC by 41.38%–51.42%, KMnO4-C and LFOC by 29.84%–34.09% and 56.68%–65.36% in the 0–40 cm soil depth. The LFOC and KMnO4-C were proved to be the most sensitive fractions to different corn straw returning modes. Compared with CK, soils amended with corn straw increased mean weight diameter by 24.24%–40.48% in the 0–20 cm soil depth. The NTS and MTS preserved more than 60.00% of OC in macro-aggregates compared with CK. No significant difference was found in corn yield across all corn straw returning modes throughout the study period, indicating that adoption of NTS and MTS would increase SOC content and improve soil structure, and would not decline crop production.

Crop rotations differ in soil carbon stabilization efficiency, but the response to quality of structural plant inputs is ambiguous

Evaluate crop rotation diversity, perenniality, carbon (C) inputs, and C input quality as predictors of soil organic carbon (SOC) concentration and aggregate mean weight diameter (MWD). At a crop rotation trial in its 37th year in Ontario, Canada, species in rotations included corn (C, Zea mays L.), alfalfa (A, Medicago sativa L.), soybean (S, Glycine max (L.) Merr.), winter wheat (W, Triticum aestivum L.), and red clover (rc, Trifolium pratense L.). Rotations were: CC, CCAA, CCSS, CCSW, CCSWrc, AA. Soils (0–20 cm) were analyzed for aggregate MWD, aggregate C, and SOC concentrations. We estimated C inputs from historical yields and C input quality (C:N, lignin: N, or NMR-derived index) from structural plant tissues. C stabilization efficiency was estimated as the ratio of SOC stock per unit total or root C input. Crop rotation diversity failed to increase SOC concentrations or aggregate MWD. Perennialized rotations (CCSWrc, CCAA, AA) maintained the numerically highest SOC concentrations, and root C input increased SOC concentration. Out of 12 statistical tests relating C input quality to C stabilization efficiency, only 3 indicated a positive effect and 6 tests indicated a negative effect. Including a perennial forage such as alfalfa and limiting soybean frequency promotes aggregate MWD and SOC concentration more so than optimizing crop rotation diversity. Quality of structural plant inputs does not explain differences in C stabilization efficiency, possibly due to overriding influence of living root inputs.

Effects of long-term phosphorus fertilizer applications on soil carbon and CO2 flux

ABSTRACT Long-term agricultural research with annual and perennial cropping systems provides significant insight into the carbon sequestration potential of agriculture in the East Mediterranean region of Anatolia. This study explored the effect of different application rates of phosphorus (P) fertilizer on the storage and quality of soil organic carbon (SOC) and soil CO2 flux to assess the relationship between SOC and P application. The study was based on the hypothesis that long-term P fertilization can affect carbon sequestration in soil and impact soil CO2 flux. The objectives of the present study were to: (i) analyze the effect of long-term inorganic chemical P fertilization on SOC content and (ii) estimate the effect of long-term P fertilization on CO2 flux. Under crop rotation, corn (Zea mays L.) and wheat (Triticum aestivum L.) (CW system) were exposed to four fertilizer doses (0, 50, 100, and 200 kg ha−1), which were repeated annually over 20 years. During plant growth, bare soil and treated soil CO2 fluxes were determined several times. The results demonstrated that P fertilizer did not have a direct impact on the SOC of the summer-maize growing season and had a positive impact on SOC during the winter-wheat growing season. P fertilization levels have positive impact on atmospheric CO2 capture and increased SOC content.

Isolation of Efficient Cellulose Decomposer in Sandy Cropland and Its Application in Straw Turnover in Agro-Pasture Ecotone of Northern China

Slow organic material and nutrient turnover is one of the limiting processes in arid and semi-arid ecosystems, and cellulose decomposers play important role in straw turnover and nutrient return in cropland ecosystem in drylands. In order to moderate the limiting effect of material turnover, a high efficient cellulose decomposing fungus was screened from 85 cellulose decomposing fungi and we named the isolated fugus as NMCel-crop1 in the sandy cropland of Horqin Sandy Land in a semi-arid agro-pasture ecotone in northern China. This fungal decomposer was identified as Rhizomucor variabilis by using morphological and rDNA-ITS molecular methods. The optimized temperature for expressing its CMC (carboxymethyl cellulose) enzyme activity ranges from 40-55 °C. The CMC enzyme activity was significantly and highly produced by the NMCel-crop1 than that in situ soil in the cropland, and the filter paper decomposition rate was 82% in 7 days. The field straw decomposition experiment showed that the decomposition rate of maize straw infected by NMCel-crop1 reached at 92.5% in one year, which was 26% higher than that without infection. Straw turnover accelerated by NMCel-crop1 significantly increased soil organic carbon (SOC) and total nitrogen (TN) by 34.08% and 14.26%, respectively, indicating that the selected high efficient decomposing fungus could accelerate straw turnover rate, and increase soil organic carbon and nitrogen content and promote soil fertility and soil health in the sandy cropland, as well as potentially improve crop productivity and quality in the sustainable agriculture management of the arid and semi-arid sandy cropland.

Contrasting short-term responses of soil heterotrophic and autotrophic respiration to biochar-based and chemical fertilizers in a subtropical Moso bamboo plantation

Application of biochar-based fertilizer (BF), produced by combining biochar with chemical fertilizer, is known to be an effective way to increase plant growth and soil organic carbon (SOC) stock, but its impact on soil respiration (RS) components and associated mechanisms in subtropical plantations remain unclear. The objectives of this 12-month field study were (1) to examine the effects of the application of a BF versus a chemical fertilizer (CF) on seasonal variations in soil heterotrophic (RH) and autotrophic (RA) respiration in a subtropical plantation of Moso bamboo (Phyllostachys edulis), and (2) to investigate relationships between soil RH and RA and soil environmental factors in different fertilizer treatments. Four treatments were tested: control (no fertilizer applied), BF application, CF application, and a 50: 50 mixture of BF and CF (BCF). Irrespective of the treatment, both RS and RH exhibited strong seasonal patterns. However, adding CF in the soil significantly increased the soil RH whereas BF decreased it (P < 0.05). Both CF and BF significantly (P < 0.05) increased soil RA. The RS, RH and RA were all exponentially related (P < 0.05) to soil temperature regardless of the treatment, and the Q10 value of RH was greater than that of RA (P < 0.05). Applying CF increased the Q10 for RH (P < 0.05), yet the application of BF did not affect it. Although the RS, RH and RA were not related to the soil moisture content in all treatments, both RS and RH were correlated (P < 0.05) with soil water soluble organic C and microbial biomass C concentrations, and also with soil invertase and β-glucosidase activities. In conclusion, compared with the conventional chemical fertilizer use, the novel management practice of biochar-based fertilizer application offers advantages, such as reducing soil C emissions and increasing SOC content, which has the implication of mitigating soil greenhouse gas emissions in subtropical Moso bamboo plantations.

Acid rain mediated nitrogen and sulfur deposition alters soil nitrogen, phosphorus and carbon fractions in a subtropical paddy

Agricultural ecosystems are globally important sinks of carbon and other nutrient elements. In China, acid rain events affect about 0.62 million km2, representing about 6.4% of total land area; however, the impacts of acid rain mediated nitrogen (N) and sulfur (S) depositions on soil organic carbon (SOC) fractions and nutrient stocks in paddy soils and implications for yield production under climate change are unclear. We conducted a field experiment during two annual crop seasons to determine the effects of simulated acid rain on SOC fractions and nutrients in a subtropical paddy in China. Acid rain treatments comprised solutions of HNO3 + H2SO4 to simulate N and S deposition at pH levels of 4.5, 3.5, and 2.5. The results showed that content of soil C fractions varied with acid rain pH. Acid rain led to increased SOC concentrations and decreased the ratios of soil labile organic carbon (LOC): SOC and dissolved organic carbon (DOC): SOC concentrations, independently of crop season and growth stage. Soil salinity was positively associated with SOC suggesting that higher levels of salinity inhibit C decomposition favoring SOC accumulation. Treatment effects of acid rain on soil microbial C and N depended on crop growth stage. Concentration of Fe2+ was positively correlated with DOC in early and late paddy soils under acid rain, possibly as a result of Fe2+ retention by DOC, when Fe3+ is reduced to Fe2+. Acid rain led to increases in soil TN, TP, available N, NH4+ concentration, and SOC, and decreases in ratios of DOC: SOC, indicating decreases in soil biological activity and mineralization processes. Increases in dead rice plant biomass under acid rain were consistent with the increase in soil N and P concentrations, due to reduced nutrient uptake, and higher levels of total SOC.