Increased Soil Organic Carbon Research Articles

Carbon sequestration potential and its main drivers in soils under alfalfa (Medicago sativa L.).

As a perennial forage crop, alfalfa (Medicago sativa L.) has been extensively utilized for the vegetation restoration of degraded soil and provides feedstock for forage. Its high usage can be attributed to its high yield potential and the increasing soil organic carbon (SOC) sequestration of alfalfa cultivation. However, the impact of land conversion to alfalfa on SOC content and its underlying drivers remain unclear. We performed a meta-analysis at the global scale to explore the quantified effects of alfalfa cultivation on SOC content and identify its controlling factors. We employed 1699 pairwise data points from 90 publications based on cropland/abandoned land conversion to alfalfa. Globally, cropland (cropland-alfalfa) and abandoned land (abandoned land-alfalfa) conversion to alfalfa enhanced SOC content by 12.1 % and 13.7 %, respectively. Alfalfa exhibited greater SOC content benefits in the surface soils (0-20 cm) with a lower level of initial SOC (<16 g kg-1), regardless of the land conversion type. Cropland-alfalfa was observed to increase SOC content with fertilization, irrigation, and conventional tillage in the long term (>5 years). Furthermore, abandoned land-alfalfa enhanced SOC content in the absence of alfalfa biomass removal and for longer cultivation durations (>5 years). Boosted regression tree analyses indicated variations in soil properties (75 % for cropland-alfalfa and 65 % for abandoned land-alfalfa) as the primary factors driving changes in SOC content. The dominant drivers were determined as the soil layer (51.6 %), cultivation duration (13.1 %), and initial SOC (12.9 %) for cropland-alfalfa, and initial SOC (43.7 %), soil layer (24.6 %) and cultivation duration (17.1 %) for abandoned land-alfalfa. Land conversion to alfalfa has great potential for SOC sequestration, particularly in low-fertility soils. Therefore, alfalfa cultivation is highly recommended for degraded lands due to its SOC sequestration benefits in vegetation restoration.

Long-term residue returning increased subsoil carbon quality in a rice-wheat cropping system

Residue returning (RR) was widely implemented to increase soil organic carbon (SOC) in farmland. Extensive studies concentrated on the effects of RR on SOC quantity instead of SOC fractions at aggregate scales. This study investigated the effects of 20-year RR on the distribution of labile (e.g., dissolved, microbial biomass, and permanganate oxidizable organic) and stable (e.g., microbial necromass) carbon fractions at aggregate scales, as well as their contribution to SOC accumulation and mineralization. The findings indicated a synchronized variation in the carbon content of bacterial and fungal necromass. Residue retention (RR) notably elevated the concentration of bacterial and fungal necromass carbon, while it did not amplify the microbial necromass carbon (MNC) contribution to SOC when compared to residue removal (R0) in the topsoil (0–5 cm). In the subsoil (5–15 cm), RR increased the MNC contribution to SOC concentration by 21.2%–33.4% and mitigated SOC mineralization by 12.6% in micro-aggregates (P < 0.05). Besides, RR increased soil β-glucosidase and peroxidase activities but decreased soil phenol oxidase activity in micro-aggregates (P < 0.05). These indicated that RR might accelerate cellulose degradation and conversion to stable microbial necromass C, and thus RR improved SOC stability because SOC occluded in micro-aggregates were more stable. Interestingly, SOC concentration was mainly regulated by MNC, while SOC mineralization was by dissolved organic carbon under RR, both of which were affected by soil carbon, nitrogen, and phosphorus associated nutrients and enzyme activities. The findings of this study emphasize that the paths of RR-induced SOC accumulation and mineralization were different, and depended on stable and labile C, respectively. Overall, long-term RR increased topsoil carbon quantity and subsoil carbon quality.

Irrigation Practices and Their Effects on Soil Quality and Soil Characteristics in Arid Lands: A Comprehensive Geomatic Analysis

Comprehension of the long-term effects of irrigation on basic soil characteristics and quality is essential for sustainable land management and agricultural production, particularly in arid regions where water availability is limited. This study aimed to investigate long-term irrigation effects on soil quality, soil organic carbon (SOC), and nitrogen (N) stocks in the arid lands of Egypt. Seventy soil samples were collected and analyzed to determine various soil properties. A soil quality index (SQI), SOC, and N stocks were computed. ANOVA and PCA analyses were used to identify significant differences between alluvial soils in the southwest part of the investigated area and coastal marine soils in the northeast of the study area. The results demonstrated that most of the studied soil parameters had significantly greater values in alluvial compared to coastal marine soils. Long-term irrigation led to an 8.00% increase in SOC and 7.22% increase in N stocks compared to coastal marine soils production. Furthermore, a 39.53% increase was found in the SQI upon long-term irrigation practice. These results suggest that shifting from rain-fed in coastal marine areas to irrigated production systems in alluvial fields can improve soil quality, SOC, and N stocks. Therefore, further studies are required to investigate the impact of additional factors, such as irrigation method and salinity status of sub-surface soil layers, to enhance agricultural productivity and sustainable land use.

Regulation of soil organic carbon dynamics by microbial communities during reforestation of Chinese fir plantations after clear‐cutting

AbstractReforestation after forest clear‐cutting is an effective measure to increase soil organic carbon (SOC) sequestration; still, the soil C balance under reforestation and the role of microbial communities in that process remain to be determined. Samples of organic (0–2 cm) and mineral (2–10 cm) horizons were collected from the 7‐, 15‐, 20‐, 29‐, and 36‐year‐old forest stands of Chinese fir (Cunninghamia lanceolata) after plantation clear‐cutting in subtropical zone under the condition of phosphorus limitation. Particulate organic carbon (POC), mineral‐associated organic carbon (MAOC), microbial phospholipid fatty acids (PLFAs), and enzymatic activities for C, nitrogen (N), and phosphorus (P) acquisition were analyzed. The lowest contents of POC (10%) and MAOC (13%) in the organic horizon were found in 7‐year‐old stands due to the slow tree regrowth and extensive decomposition of SOC in the first years of forest regrowth. POC (2.0×) and MAOC (0.8×) increases in the organic horizon with forest age were attributed to the stand development and accumulation of above‐ and belowground litter. The organic horizon had a higher POC:MAOC ratio than the mineral (0.7–1.1 vs. 0.2–0.5), indicating lower SOC stability in the first one. The ratio of POC:MAOC increased with the Gram‐positive to Gram‐negative bacteria (G+:G‐) ratio, pointing out that microbial communities developed a specific community structure and substrate utilization strategies of organic matter under plantation restoration. The increase of total PLFAs and the G+:G‐ ratio was closely linked with the microbial C and P limitations, indicating that microorganisms shifted community structure to slow‐growing species and increased their content to cope with the C and P restrictions. In the soils of young plantations, microorganisms were limited by C and P; however, the C limitation was alleviated in the 36‐year‐old plots in the organic horizon due to increased litter input, whereas the P limitation was not. This discrepancy between C and P limitation suppressed the decomposition of litter entering the soil, which was seen in decreased specific activity of C degrading enzymes and led to the accumulation of POC in the organic horizon. Thus, soil C sequestration under reforestation of Chinese fir can be controlled by the amount of litter entering the soil and by metabolic C, N, and P limitations that force microorganisms to shift community structure and change their activity.

Changes in soil N2O emissions and nitrogen use efficiency following long-term soil carbon storage: Evidence from a mesocosm experiment

Policy and market incentives are rapidly expanding to promote soil organic carbon (SOC) sequestration in global croplands. Evidence suggests that long-term increases in SOC can influence both crop yield and nitrogen (N) fertilizer requirements, with the potential to help address two important sustainability challenges. However, increases in SOC may also trigger higher soil nitrous oxide (N2O) emissions, which would represent an important tradeoff for climate change mitigation. We tested the hypothesis that long-term increases in SOC are associated with higher crop yields and fertilizer N use efficiency (NUE), but at the cost of higher N2O emissions. Wheat was grown in two soils (SOClow and SOChigh) under three N fertilizer rates (0, 100, and 200 kg N ha−1) in a mesocosm experiment. Soils were obtained (0–25 cm) from a 22-yr field experiment on no-till and cover cropping in California. Results indicate that total biomass and grain yield were higher for SOClow than SOChigh at 100 kg N ha−1 but not the other N levels. Crop N uptake was also 28% greater for SOClow at 200 kg N ha−1, resulting in higher overall NUE. Soil N2O emissions increased for SOChigh by 25–112% compared to SOClow, likely due to long-term changes in labile C and N pools, microbial activity, and soil structure influencing porosity and gas diffusion. While there are well-documented crop and environmental benefits from enhancing SOC in agricultural soils, results from this study suggest that changes in soil N2O emissions should be considered to accurately determine net GHG emission reductions.

A strategy to enhance soil quality and soil organic carbon stock in abandoned lands: Pasture regeneration through shrub clearing

AbstractFarmland abandonment in Mediterranean mid‐mountain areas can lead to the degradation or recovery of soil properties. Typically, after abandonment, fields are covered with shrubs, which hinders livestock grazing and constitutes high wildfire risk. To avoid these negative effects, shrubs are cleared in selected areas. The main objective of this study is to evaluate whether shrub clearing can improve soil quality and enhance carbon sequestration. A case study was conducted in the Leza Valley (La Rioja, Spain), examining five different land uses/management practices in both acid and alkaline soil environments. These included shrubland (control), three shrub clearing sites (managed &lt;5, 15, and 25 years ago), and control pasture (reference). Soil replicates at different depths (0–40 cm) were collected, and physico‐chemical properties were analysed. A theoretical map of potential shrub clearing areas was created, and the potential to accumulate carbon was evaluated. Results showed that shrub clearing increases soil organic carbon and nitrogen, specially in 25‐year clearings. The increases were greater and significant on alkaline environments. The cartographical analysis reveals that 3388 ha can be still cleared in the Leza Valley, which could increase soil organic carbon accumulation by up to 31.6% in 25‐year period. We propose shrub‐clearing as a strategy for enhancing carbon sequestration in Mediterranean mountain areas.

Response of soil organic carbon to straw return in farmland soil in China: A meta-analysis

Straw return is an effective measure to promote sustainable agriculture by significantly improving soil fertility. At present, few studies have been conducted on the most effective carbon enhancing management measures for various crops. Therefore, we conducted a meta-analysis using data collected from 184 literature sources, comprising 3297 data sets to analyze the carbon increase effects of straw returning in three main crops (rice, maize, and wheat) in China and to explore the influence mechanism of natural factors, soil properties, straw return measures, and cropping systems on the carbon enhancement effect. The study showed that straw return significantly increased soil organic carbon and the rate of increase was higher for wheat at 15.88% (14.74%–17.03%) than for rice at 12.7% (11.5%–13.91%) and maize at 12.42% (11.42%–13.42%), with varying degrees of improvement in other soil physicochemical properties. Natural factors have the greatest impact on the carbon increasing effect of rice fields, reaching 28.8%, especially at temperature between 10 °C and 15 °C, less than 800 mm precipitation, low latitude, and short frost-free period. Maize and wheat are most affected by soil properties, reaching 41% and 34.5% respectively. Furthermore, field management practices also play a pivotal role, organic carbon increasing obviously was observed when the C/N ratio of exogenous nutrients is bigger than 20 with the low initial organic matter. Shallow tillage and less than 7.5 t hm−2 straw returning with 3–10 years to the field are ideal for rice and maize. Crop rotation, especially in drylands, increased soil organic carbon more significantly than continuous. The results of our analysis can provide valuable insights into the effect of straw return on carbon increase. In the future, the soil carbon can be improved by adopting rational cropping patterns and straw return measures with taking into account climate and soil characteristics for different crops.

Estimation of Maize Residue Cover Using Remote Sensing Based on Adaptive Threshold Segmentation and CatBoost Algorithm

Maize residue cover (MRC) is an important parameter to quantify the degree of crop residue cover in the field and its spatial distribution characteristics. It is also a key indicator of conservation tillage. Rapid and accurate estimation of maize residue cover (MRC) and spatial mapping are of great significance to increasing soil organic carbon, reducing wind and water erosion, and maintaining soil and water. Currently, the estimation of maize residue cover in large areas suffers from low modeling accuracy and poor working efficiency. Therefore, how to improve the accuracy and efficiency of maize residue cover estimation has become a research hotspot. In this study, adaptive threshold segmentation (Yen) and the CatBoost algorithm are integrated and fused to construct a residue coverage estimation method based on multispectral remote sensing images. The maize planting areas in and around Sihe Town in Jilin Province, China, were selected as typical experimental regions, and the unmanned aerial vehicle (UAV) was employed to capture maize residue cover images of sample plots within the area. The Yen algorithm was applied to calculate and analyze maize residue cover. The successive projections algorithm (SPA) was used to extract spectral feature indices from Sentinel-2A multispectral images. Subsequently, the CatBoost algorithm was used to construct a maize residue cover estimation model based on spectral feature indices, thereby plotting the spatial distribution map of maize residue cover in the experimental area. The results show that the image segmentation based on the Yen algorithm outperforms traditional segmentation methods, with the highest Dice coefficient reaching 81.71%, effectively improving the accuracy of maize residue cover recognition in sample plots. By combining the spectral index calculation with the SPA algorithm, the spectral features of the images are effectively extracted, and the spectral feature indices such as NDTI and STI are determined. These indices are significantly correlated with maize residue cover. The accuracy of the maize residue cover estimation model built using the CatBoost model surpasses that of traditional machine learning models, with a maximum determination coefficient (R2) of 0.83 in the validation set. The maize residue cover estimation model constructed based on the Yen and CatBoost algorithms effectively enhances the accuracy and reliability of estimating maize residue cover in large areas using multispectral imagery, providing accurate and reliable data support and services for precision agriculture and conservation tillage.

Cover crops and poultry litter impact on soil structural stability in dryland soybean production in Southeastern United States

AbstractThis study explored the efficacy of soil aggregate indices in quantifying soil structural development, utilizing 5‐year field experiment data from the Southeastern United States. The experiment utilized a split‐plot design with cover crops (native vegetation as control, cereal rye (Secale cereale L.), winter wheat (Triticum aestivum), hairy vetch (Vicia villosa), and mustard (Brassica rapa) plus cereal rye as the main factor and fertilizer source (no fertilizer as control, inorganic fertilizer with phosphorus, potassium, and elemental sulfur, and poultry litter) as the secondary factor. Aggregate size fractions were determined using the wet‐sieving method, and aggregate stability index (ASI), mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimension (FD) were calculated to assess soil structural stability. Main effects results indicated that cereal rye (55.11%) and poultry litter (50.97%) exhibited the highest ASI values. The highest MWD, GMD, and FD were observed under mustard plus cereal rye (1.187 mm), cereal rye (0.462 mm), and hairy vetch (2.573), respectively. Principal component analysis revealed that cover crops significantly improved soil aggregate structure and stability, overcoming limitations of sole fertilization practices. Regression analysis suggested that ASI, MWD, and GWD positively correlated with soil organic carbon, whereas FD negatively correlated with MWD, GMD, and ASI. Principal component analysis exhibited that FD decreased with increasing soil organic carbon, ASI, MWD, and GMD, demonstrating that lower FD values indicate enhanced soil aggregation and structure. Assessed indices, FD included, effectively gauged soil structural stability. These metrics should be prioritized in managerial decisions to support soil productivity and health in agricultural systems.

Long‐term successive biochar application increases plant lignin and microbial necromass accumulation but decreases their contributions to soil organic carbon in rice–wheat cropping system

AbstractBiochar application is widely recognized as an effective approach for increasing soil organic carbon (SOC) and mitigating climate change in agroecosystems. However, the effects of biochar application on net accumulations and relative contributions of different SOC sources remain unclear. Here, we explored the effects of biochar application on plant‐derived (PDC) and microbial necromass C (MNC) in a 10‐year experimental rice–wheat rotation field receiving four different intensities of biochar application (0, 2.25, 11.5, and 22.5 t ha−1 for each crop season), using phospholipid fatty acids (PLFAs), lignin phenols and amino sugars as biomarkers of microbial biomass, PDC and MNC, respectively. Our results showed that biochar application increased SOC content and stock by 32.6%–203% and 26.4%–145%, respectively. Higher biochar application (11.5 and 22.5 t ha−1) increased soil pH, total nitrogen (TN), total phosphorus (TP), SOC/TN, and root biomass. In addition, higher biochar application enhanced bacterial, fungal, and total microbial biomass. Plant lignin phenols and MNC contents significantly increased, whereas their contributions to SOC significantly decreased with the increase in biochar application rates due to the disproportionate increase in PDC and MNC, and SOC. Fungal necromass had a greater contribution to SOC than bacterial necromass. The fungal/bacterial necromass decreased from 2.56 to 2.26 with increasing biochar application rates, because of the higher abundances of bacteria than that of fungi as indicated by PLFAs under higher biochar application rates. Random forest analyses revealed that pH, TP, and SOC/TN were the main factors controlling plant lignin and MNC accumulation. Structural equation modeling revealed that biochar application increased lignin phenols by stimulating root biomass, whereas enhanced MNC accumulation was primarily from increased microbial biomass and lignin phenols. Overall, our findings suggest that biochar application increases the accumulation of the two SOC sources but decreases their contributions to SOC in paddy soils.

Inversion Tillage Combined with Organic Fertilizer Application Increased Maize Yield via Improving Soil Pore Structure and Enzymatic Activity in Haplic Chernozem

Inversion tillage and organic fertilizer application can break the plow pan and improve soil quality. However, the effects of combining these practices on the soil microbial resource limitation and maize yield in Haplic Chernozem are unclear. In this research, a field experiment was established in 2018, and soil samples were collected in 2021 in Longjiang County in Northeast China, which is a Haplic Chernozem region. Four treatments comprising conventional tillage (T15), conventional tillage with organic fertilizer (T15+M), inversion tillage (T35), and inversion tillage with organic fertilizer (T35+M) were randomly arranged with four replications. Compared with T15 and T15+M treatments, soil bulk density significantly decreased by 11.1–16.3% in the 15–35 cm layer under T35 and T35+M treatments, accompanied by the improvement in soil pore structure (e.g., soil porosity, circularity, and Euler number). T15+M treatment significantly increased soil organic carbon and soil nutrient contents by 11.1–16.3% and 3.9–24.5% in the 0–15 cm layer compared with other treatments. However, soil organic carbon, total nitrogen, available phosphorus content, microbial biomass, and enzymatic activities reached the maximum values in the 0–35 cm layer under T35+M treatment. In addition, T35+M treatment had the highest maize yield and sustainable yield index. Extracellular enzymatic stoichiometry suggested that soil microorganisms are generally co-limited by carbon and phosphorus in Haplic Chernozem. However, T35+M treatment significantly reduced soil microbial resource limitation, which was one important factor impacting maize yield and sustainability. Random-forest and partial least-squares path modeling showed that T35+M treatment could reduce soil microbial resource limitation and increase the stability and sustainability of the maize yield by improving soil available nutrients, microbial biomass, and pore structure. Therefore, the incorporation of inversion tillage and organic fertilizer is a suitable soil management practice in view of increasing soil quality and crop yields in a Haplic Chernozem region.

Disentangling the effects of mineral fertiliser N, P and K on microbial biomass, necromass and ionome in soil from the Askov long-term field experiment

Given the increasingly recognised importance of microbial biomass (MB) in soil organic carbon (SOC) sequestration, knowledge of the microbial ionome beyond carbon (C), nitrogen (N) and phosphorus (P) becomes crucial. The microbial ionome could indicate nutritional restrictions related to MB growth and microbial necromass C (MN-C) accumulation. In this study, soils receiving different combinations of mineral N, P and potassium (K) were sampled in the Askov long-term field experiment, Denmark, and analysed for MB elemental composition including N, P, K, magnesium (Mg), manganese (Mn) and zinc (Zn) using fumigation-extraction and ICP-OES. Furthermore, bacterial, archaeal and fungal gene abundance was determined by qPCR as microbial community shifts may relate to microbial ionome shifts. MN-C was determined by amino sugar analysis. MB-C was unaffected by fertiliser treatments and not correlated with MN-C. N fertilisation increased MN-C. N and K additions increased plant-derived SOC, indicating the importance of N for microbial and plant-derived SOC accumulation. Availability of P and K increased MB-P and MB-K, respectively, and reduced the MB-C:P ratio but not MB-C:K. N fertilisation reduced the pH and increased Mn availability which increased MB-Mn and reduced MB-C:Mn. ITS1 gene copies responded positively to P availability. A reduced MB-C:Mn ratio was associated with a relative increase in fungal gene copy abundance. This was linked to an increase in SOC, indicating a positive link between Mn availability, fungal abundance and SOC level, yet this was not reflected in MN-C accumulation, but by the accumulation of plant-derived SOC, possibly due to reduced plant C turnover.

Contrasting roles of plant, bacterial, and fungal diversity in soil organic carbon accrual during ecosystem restoration: A meta-analysis

Plant and microbial diversity plays vital roles in soil organic carbon (SOC) accumulation during ecosystem restoration. However, how soil microbial diversity mediates the positive effects of plant diversity on carbon accumulation during vegetation restoration remains unclear. We conducted a large-scale meta-analysis with 353 paired observations from 65 studies to examine how plant and microbial diversity changed over 0–160 years of natural restoration and its connection to SOC accrual in the topsoil (0–10 cm). Results showed that natural restoration significantly increased plant aboveground biomass (122.09 %), belowground biomass (153.05 %), and richness (21.99 %) and SOC accumulation (32.34 %) but had no significant impact on microbial diversity. Over time, bacterial and fungal richness increased and then decreased. The responses of major microbial phyla, in terms of relative abundance, varied across restoration and ecosystem types. Specifically, Ascomycota and Zygomycota decreased more under farmland abandonment than under grazing exclusion. In forest, Bacteroidetes, Ascomycota, and Zygomycota significantly decreased after natural restoration. The increase in SOC and Basidiomycota was higher in forest than in grassland. Based on standardized estimates, structural equation modeling showed that plant diversity had the highest positive effect (0.55) on SOC accrual, and while fungal diversity (0.15) also had a positive effective, bacterial diversity (−0.20) had a negative effect. Plant diversity promoted SOC accumulation by directly impacting biomass and soil moisture and total nitrogen and indirectly influencing soil microbial richness. This meta-analysis highlights the significant roles of plant diversity and microbial diversity in carbon accumulation during natural restoration and elucidates their relative contributions to carbon accumulation, thereby aiding in more precise predictions of soil carbon sequestration.

Shifting Mountain Tree Line Increases Soil Organic Carbon Stability Regardless of Land Use.

Climate and land use changes are causing trees line to shift up into mountain meadows. The effect of this vegetation change on the partitioning of soil carbon (C) between the labile particulate organic matter (POM-C) and stable mineral-associated organic matter (MAOM-C) pools is poorly understood. Therefore, we assessed these C pools in a 10 cm topsoil layer along forest-meadow ecotones with different land uses (reserve and pasture) in the Northwest Caucasus of Russia using the size fractionation technique (POM 0.053-2.00 mm, MAOM < 0.053 mm). Potential drivers included the amount of C input from aboveground grass biomass (AGB) and forest litter (litter quantity) and their C/N ratios, aromatic compound content (litter quality), and soil texture. For both land uses, the POM-C pool showed no clear patterns of change along forest-meadow ecotones, while the MAOM-C pool increased steadily from meadow to forest. Regardless of land use, the POM-C/MAOM-C ratio decreased threefold from meadow to forest in line with decreasing grass AGB (R2 = 0.75 and 0.29 for reserve and pasture) and increasing clay content (R2 = 0.63 and 0.36 for reserve and pasture). In pastures, an additional negative relationship was found with respect to plant litter aromaticity (R2 = 0.48). Therefore, shifting the mountain tree line in temperate climates could have a positive effect on conserving soil C stocks by increasing the proportion of stable C pools.

Long‐term continuous maize: Impacts on the soil microbiome and implications for residue management

AbstractContinuous maize (Zea mays L.) (CM) cropping has been proposed to increase soil organic carbon stocks through greater residue return to soils. These residues, however, can contribute to a yield decrease known as the continuous maize yield penalty (CMYP). The objectives of this research were to (1) evaluate the efficacy of residue management practices to mitigate the CMYP when compared to a maize–soybean [Glycine max (L.) Merr.] (MS) rotation and (2) determine effects of long‐term rotation or residue sizing on soil microbial communities and carbon‐cycling enzyme activities. Two long‐term sites (17 and 19 years) with replicated blocks of CM and MS rotation were used. The yield response to management was similar at both sites, with an average CMYP of 2570 kg ha−1 with no residue management, while chopping the residue along with broadcast ammonium sulfate (AMS) reduced the CMYP by 728 kg ha−1 (28.3%). The CMYP was further reduced when a microbial blend was applied with AMS to the sized residues, reducing the CMYP by a total of 1303 kg ha−1 (50.7%). Soil bacterial communities differed by site but were unchanged by crop rotation or residue sizing. Soil fungal assemblage, particularly arbuscular mycorrhizal fungi, was influenced by rotation and site. Sizing of residues resulted in higher soil cellobiohydrolase activity for CM, but not for MS. These findings indicate that the CMYP was not directly associated with the soil bacterial community, and that management to mitigate the CMYP may be aided by elevated levels of fungal diversity under CM.

Manure replacing synthetic fertilizer improves crop yield sustainability and reduces carbon footprint under winter wheat–summer maize cropping system

Manure replacing synthetic fertilizer is a viable practice to ensure crop yield and increase soil organic carbon (SOC), but its impact on greenhouse gas (GHG) emissions is inconsistent, thus remains its effect on CF unclear. In this study, a 7-year field experiment was conducted to assess the impact of replacing synthetic fertilizer with manure on crop productivity, SOC sequestration, GHG emissions and crop CF under winter wheat–summer maize cropping system. Five treatments were involved: synthetic nitrogen, phosphorus, and potassium fertilizer (NPK) and 25%, 50%, 75%, and 100% of manure replacing synthetic N (25%M, 50%M, 75%M, and 100%M). Compared with NPK treatment, 25%M and 50%M treatments maintained annual yield (winter wheat plus summer maize) and sustainable yield index (SYI), but 75%M and 100%M treatments significantly decreased annual yield, and 100%M treatment also significantly reduced annual SYI. The SOC content exhibited a significant increasing trend over years in all treatments. After 7 years, SOC storage in manure treatments increased by 3.06–11.82 Mg ha−1 relative to NPK treatment. Manure treatments reduced annual GHG emissions by 14%–60% over NPK treatment. The CF of the cropping system ranged from 0.16 to 0.39 kg CO2 eq kg−1 of grain without considering SOC sequestration, in which the CF of manure treatments lowered by 18%–58% relative to NPK treatment. When SOC sequestration was involved in, the CF varied from −0.39 to 0.37 kg CO2 eq kg−1 of grain, manure treatments significantly reduced the CF by 22%–208% over NPK treatment. It was concluded that replacing 50% of synthetic fertilizer with manure was a sound option for achieving high crop yield and SYI but low CF under the tested cropping system.

Response of corn yield to water retaining agents, inhibitors, and corn stalks addition in semi-arid cropland,

Drought, excessive use of nitrogen fertilizer, and decline in soil organic matter threaten corn production. This study investigated the potential of water retaining agents, inhibitors, and corn stalks in enhancing soil physicochemical properties to bolster corn yield in semi-arid farmlands. In our study, polyacrylamide addition increased the content of ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3–-N) in the seedling stage, exchangeable potassium (K) in the mature stage but decreased the content of available phosphorus (P) in the seedling stage. Potassium polyacrylate addition increased the content of NH4+-N and decreased the content of available P in the seedling stage. The addition of inhibitors decreased the content of NH4+-N and available P in the seedling stage, NO3–-N and available P in the jointing stage, and NH4+-N in the mature stage, respectively. Corn stalks returning could maintain soil moisture, decrease the content of NH4+-N in the seedling stage and exchangeable K in the mature stage, and increase the content of available P and exchangeable K in the seedling stage. Combined application of inhibitors and corn stalks could increase soil organic carbon (SOC) and ensure corn yield, which was the best fertilization mode in semi-arid cropland.

No tillage and leguminous cover crop improve soil quality in a typical rainfed Mediterranean system

Soil and crop management influence soil organic carbon (SOC), chemical composition, and overall soil quality. In a Mediterranean region, a study initiated in 1994 examined the long-term effects of conventional tillage (CT) versus no-tillage (NT) practices. Initially focusing on continuous durum wheat cultivation until 2009, the experiment later introduced a two-year rotation of durum wheat and Vicia faba L. cover crops in half of the CT and NT fields. SOC was monitored from 2008 to 2018, while microbial biomass (as dsDNA), soluble nitrogen (N), and enzyme activities (EAs) were monitored from 2011 to 2014 to evaluate the rotation's impact.&#x0D; Between 2009 and 2018, CT yields were on average 15% higher than NT, especially during high rainfall years. NT significantly increased SOC content in the 0-30 cm soil layer, along with higher levels of soluble N, dsDNA, and EAs at 0-10 cm depth. NT led to a 23% and 10% increase in SOC stock and SOC stock per equivalent soil mass respectively compared to CT. EAs increased by over 50% under NT, indicating enhanced biological activity. The SOC increase due to NT was limited to the top 10 cm, with a decrease at deeper depths (up to 50 cm). Introducing cover crops over four years did not yield significant impacts, suggesting the need for a longer period to observe noticeable effects.&#x0D; Overall, adopting NT practices resulted in higher SOC concentration, enhanced soil biological activity, and improved biogeochemical cycles, emphasizing the positive impact of no-tillage on soil health and sustainability.

Effect of Windbreaks (Casuarina equisetifolia L.) on Productivity of Paddy in South Gujarat

The intentional integration of trees into an agroecosystem results in agroforestry practices such as windbreak, which simultaneously help the economy, the environment, and society. It is a crucial tool for safeguarding agricultural land and boosting crop productivity. An investigation was therefore conducted to determine the impact of windbreaks (Casuarina equisetifolia L.) on paddy productivity in South Gujarat. In the current study, we found that environmental competition caused paddy growth and production to decrease close to the Casuarina windbreak. The impact of the windbreaks on paddy growth and yield became positive, and the continuously increased distance from the windbreaks reached its maximum at 17 m (Plant height 97.34 cm, number of tillers per plant 11.17, total fresh weight plant 17,799 kg ha-1, dry straw weight 6,577 kg ha-1 and grain yield 4,103 kg ha-1) and then gradually decreased (plant height 83 cm, tillers per plant 8.17, total fresh weight plant 12,315 kg ha-1, dry straw weight 4,855 kg ha-1 and grain yield 3,101 kg ha-1). The wind velocity maximum (4.57 km hr-1) close to windbreaks exhibits an opposite tendency, decreasing continually to a minimum (3.32 km hr-1) at a distance of 17 meters from the windbreaks before increasing once again. In addition, this system's net returns (Rs. 40,619) and benefit-cost ratio (0.61) were noticeably higher than those of open fields (Rs. 34,749 and benefit cost ration 0.52). In contrast to the control, the pH of the soil beneath the windbreak was reported to be considerably closer to neutral (7.46), while electrical conductivity (0.19 dS/m) was reduced. The impact of windbreaks was found to considerably increase soil organic carbon (0.68%), accessible nitrogen (234.46 kg/ha), phosphorus (75.75 kg/ha), and potassium (398.07 kg/ha) as compared to control. According to the study's overall findings, windbreak-protected paddy fields perform noticeably better than open ones.

Manure fertilizer divergently affects organic and inorganic carbon in a dryland agricultural soil

AbstractSoil carbon (C) is important to support sustainable agriculture, affect global C cycling, and influence the climate system. Manure fertilization is an important and widely used practice to increase agricultural productivity and soil organic carbon (SOC) pools, whereas its effect on soil inorganic carbon (SIC) and total C in deep soils is not reported. This knowledge gap restricts our ability to accurately evaluate C budget in agricultural soils because SIC in deep soils accounts for more than half of the global soil C pools, while current earth system models rarely take them into account. Herein, we examined changes of soil C along 0‐ to 3.0‐m depth after 35 years of application of manure in a dryland agricultural ecosystem. We also measured C concentrations in soil samples (0–0.2 m) from 1985 to 2019 to evaluate C dynamics in topsoils. The objective was to understand how SIC and SOC in deep soils respond to manure fertilization in semiarid ecosystem, where SIC accounts for a large fraction of total C. We showed a divergent effect of 35 years of manure application on SOC and SIC in 0–3.0 m soil from a dryland agricultural ecosystem. Either within or across the two cropping systems examined, manure increased SOC in top 0.8 m layer but decreased SIC in 0.8–3.0 m layer, which offset SOC increase and resulted in 63.8 Mg ha−1 decrease of total C in 0–3.0 m soil layer. Given the importance of soil C for sustainable agriculture and that drylands contain 80% of the global SIC and ∼50% of world cropland, immediate attention should be paid to such divergent effects in both mechanisms understanding and model prediction.