Soil Organic Matter Research Articles

Reducing nitrogen fertilizer usage coupled with organic substitution improves soil quality and boosts tea yield and quality in tea plantations.

The utilization of chemical fertilizers is a key measure for maintaining tea yield and quality, but excessive use has negative environmental impacts. The substitution of chemical fertilizer with organic fertilizer has been promoted to sustain crop yield and soil quality. However, knowledge gaps regarding the effects of organic substitution on soil quality and tea yield in tea plantations still exist. A field experiment was conducted to investigate the influence of organic substitution treatments (i.e. 25% partial substitution: biogas slurry + green manure + formula fertilizer, BFG; sheep manure + formula fertilizer, OFF; 100% complete substitution: sheep manure + green manure, OG) on the soil quality, tea yield and quality, and nitrogen utilization efficiency in southwestern China. Results showed that all organic substitution treatments slightly increased soil pH, and significantly increased soil organic matter by 13.22-14.88% compared to conventional fertilization (CF). The BFG treatment was the most effective in enhancing the soil quality index, showing increases of 16.80%, 8.37% and 24.87% higher than the CF, OFF and OG treatments, respectively. Tea yield significantly increased under the BFG, OFF and OG treatments by 11.97%, 13.58% and 5.90% compared to CF, respectively. The BFG treatment increased the amino acid content by 7.78% and decreased the tea polyphenol/amino acid ratio by 6.87%. Additionally, the BFG, OFF and OG treatments greatly increased the nitrogen utilization efficiency of young sprouts by 70.71%, 82.54% and 34.28%, respectively. Overall, partial organic substitution could effectively improve soil quality while maintaining tea yield. © 2024 Society of Chemical Industry.

Effects of groundwater level changes on soil characteristics and vegetation response in arid and semiarid coal mining areas.

Coal mining in arid and semiarid regions often leads to numerous ecological and environmental problems, such as aquifer depletion, lake shrinkage, vegetation degradation, and surface desertification. The drainage from coal mining activities is a major driving force in the evolution of the groundwater-soil-vegetation system. In order to explore the effect of groundwater level fluctuation on soil properties and the response mechanism of surface vegetation in coal mining areas, this study is based on hydrogeological and ecological vegetation investigations in the Bojianghaizi Basin, and soil and vegetation samples are collected in the areas with different groundwater levels, and soil and vegetation indexes are analyzed with the aid of methods such as numerical statistics, linear regression, and correlation analysis with the aid of the Origin software. The results show that there is a significant negative correlation between groundwater table (GWT) and soil water content (SWC), soil conductivity, soil organic matter (SOM), soil available nitrogen (SAN), and soil available potassium (SAK). Mining activities have led to the destruction of the soil structure, greatly reducing its ability to retain water and fertilizer. The contents of SWC, SOM, and SAN in the mining area are significantly reduced, which are at least 49.73%, 47.56% and 59.90% lower than those around the mining area. On the northern and southern sides of the lake, serious soil salinization exists in the lakeshore zone where the depth to the water table is <0.5m, and the water required for the growth of vegetation here mainly comes from the groundwater, so there are only a few water-loving and saline-resistant plants; when the depth to the water table is 0.5-7m, the growth of surface vegetation is influenced by the double impacts of the water table and atmospheric precipitation with a high degree of species richness; when the depth to the water table is >7m, the surface vegetation is only dependent on the limited atmospheric precipitation for water. When the depth of groundwater is >7m, the surface vegetation only relies on limited atmospheric precipitation for water, and drought-tolerant plants mainly grow in these areas. This study not only provides a scientific basis for the sustainable development and environmental protection of similar mines in the world, but also has important significance in guiding the ecological management and rational utilization of water resources in coal mine areas. What is more, This study provides valuable insights into sustainable water resource management in arid and semi-arid regions, crucial for mitigating the ecological impacts of coal mining activities.

Study on Nano-Zn, Inorganic, and Organic Nutrient Management Practices and Their Impact on Nutrient Availability in Kharif Maize (Zea mays L.)

A study was conducted to assess the impact of Nano-Zn, inorganic, and organic nutrient management practices on the physico-chemical properties and nutrient availability in Kharif maize (Zea mays L.) grown during 2022 and 2023 at Chandra Shekhar Azad University of Agriculture &amp; Technology, Kanpur. The experiment followed a split-plot design, with organic manures (Control, FYM at 10 t/ha, and Vermicompost at 5 t/ha) as the main plot treatments and various nutrient management strategies (Control, 75% RDF, 75% RDF + ZnSO4 at 25 kg/ha, 75% RDF + Nano-Zn at 10 ml/litre, 100% RDF, 100% RDF + ZnSO4, and 100% RDF + Nano-Zn) as the subplot treatments. Results showed that combining 100% RDF with Nano-Zn and ZnSO4 significantly enhanced soil nutrient availability and improved physico-chemical properties compared to control treatments. The organic carbon content was highest in the 100% RDF + Nano-Zn treatment (0.492%), suggesting an increase in soil organic matter. Nitrogen availability was significantly higher in this treatment, with a pooled value of 151.167 kg/ha, compared to 143.443 kg/ha in the control. Phosphorus availability also increased in the 100% RDF + Nano-Zn treatment (16.337 kg/ha), indicating better phosphorus mobilization. Potassium availability was enhanced, with the highest recorded value (216.39 kg/ha) in the 100% RDF + Nano-Zn treatment, while the control treatment had 213.597 kg/ha. Zinc availability was markedly improved, with the 100% RDF + Nano-Zn treatment reaching 0.853 mg/kg, compared to 0.79 mg/kg in the control. This study demonstrated that integrating Nano-Zn and ZnSO4 with inorganic fertilizers significantly improved soil fertility, nutrient availability, and potentially enhanced crop performance in Kharif maize. These findings indicate that combining inorganic and nano-fertilizers could be an effective nutrient management strategy, contributing to sustainable agricultural practices and improved productivity in maize cultivation, alongside better soil health.

Soil Organic Carbon Dynamics: Drivers of Climate Change-induced Soil Organic Carbon Loss at Various Ecosystems

At roughly 2500 Peta gram (Pg) C, soil organic carbon (SOC) is the biggest carbon store in terrestrial ecosystems and is a crucial contributor to vital soil functions and ecosystem services, such as agricultural soil productivity. SOC stocks are in a dynamic equilibrium between C inputs, primarily from crop residues and organic manures, and C loss owing to decomposition and mineralization of soil organic matter (SOM) under long-term constant land management and environmental circumstances. In addition, the rate of C addition in native ecosystems is governed by the nature and productivity of the local flora, which is mostly influenced by climatic conditions. However, being a complex system, various factors, such as soil management and land-use change influence the soil C pool. Along with temperature gradients from temperate to tropical regions, SOC supplies were shown to be shrinking on a global and regional basis. This reflects the rates of SOM decomposition as a function of temperature, which fluctuates more rapidly than net primary production (NPP). SOM decomposition rates are also influenced by several parameters, including soil temperature and moisture, soil respiration and pH, and soil physical properties including texture and clay mineralogy. Nonetheless, increased temperatures as a result of climate change are thought to be the primary driver of accelerated decomposition, which results in considerable reductions in SOC supplies and sequestration. Furthermore, climatic change contributes to soil deterioration by increasing the mineralization of the SOC pool and causing desertification (irreversible expansion of desert landforms). Similarly, erosion is a degrading process that affects C dynamics and leads to terrestrial carbon loss through the breakdown of structural aggregates, as well as lower productivity in eroding areas due to a lack of soil nutrients. Thus, for an in-depth understanding of worldwide soil C dynamics and to provide support to C management and decision support systems to policymakers and land managers in the face of changing climates, comprehensive research on the influence of multiple climate-induced drivers on soil C is required.

Residue Addition Can Mitigate Soil Health Challenges with Climate Change in Drylands: Insights from a Field Warming Experiment in Semi-Arid Texas

Texas cotton production is facing challenges from increased temperatures and extended droughts. We sought to determine whether applying a multi-species grass mulch on the surface of cotton fields in a semiarid region would mitigate some of the negative effects of climate change. We used open-top chambers (OTCs) to mimic climate warming and compared whether the effects of residue addition were similar between dryland and irrigated cotton fields located in the High Plains region of Texas during the summer of 2021. The OTCs raised the average air temperature by 2 °C. Under experimental warming, residue addition increased moisture content in non-irrigated (i.e., dryland) soils (+9.2%) and reduced the daily temperature range (by −1.4 °C) relative to uncovered soils. Furthermore, when pooled across irrigation and warming treatments, the addition of residue increased microbial biomass, soil respiration (+78.2%), and cotton yield (+15.2%) relative to uncovered soils. OTCs further enhanced the residue effects on microbial biomass by 34.9%. We also observed higher soil organic matter, microbial biomass, cotton biomass, and yield in irrigated fields compared to dryland, irrespective of residue addition. Our findings suggest that residue addition in dryland agriculture can mitigate the adverse effects of warming by stabilizing soil microclimates and promoting microbial growth and biomass by providing a more labile source of carbon, which, in turn, could boost the yield of cotton plants.

Increasing plant species diversity benefits soil protein accumulation in a subtropical forest

Abstract Protein, derived from plant and microbial residues, constitutes a significant portion of soil nitrogen or organic carbon pool and plays a crucial role in determining soil nitrogen and carbon sequestration. Though diversifying plant species has been regarded as a promising strategy for promoting soil nitrogen or organic carbon accumulation during vegetation restoration or afforestation, how increasing plant species diversity (PSD) would influence soil protein pool remains unknown. We selected 45 plots covering a natural gradient of PSD, which was reflected by the Shannon index and varied from 0.15 to 3.57, in a subtropical karst forest. The major objective was to investigate the impact of increasing PSD on soil protein abundance, with soil protein depolymerization rate and multiple biotic and abiotic variables being measured to explore the underlying mechanism. The relative abundance of soil protein, that is proportion in soil organic matter varied between 24.1 and 34.0% with an average of 29.2 ± 2.3% across the 45 plots. Soil protein abundance increased on average by 1.56% with each unit of PSD increase. Nevertheless, soil protease activity, protein depolymerization rate and microbial amino acid uptake rate all significantly (p &lt; 0.05) decreased as PSD increased. The mechanism underlying the increase of soil protein abundance in response to higher PSD included three aspects, that is stimulating microbial biomass and subsequent microbial residue input to the soil, promoting mineral protection of soil protein via elevating levels of soil exchangeable calcium and magnesium, and decreasing soil protease activity and protein depolymerization due to aggravated soil microbial phosphorus limitation. Synthesis and application: Our study suggests that increasing PSD is an efficient way to promote soil protein accumulation. Given that protein is a major component of soil nitrogen or organic carbon pool, diversifying plant species during vegetation restoration or afforestation would hence benefit soil nitrogen and organic carbon sequestration.

Reducing the Sodium Adsorption Ratio Improves the Soil Aggregates and Organic Matter in Brackish-Water-Irrigated Cotton Fields

The assessment of soil health relies on key parameters such as soil aggregates and organic matter content. Therefore, examining the impact of irrigation water ion composition and variations in salinity on soil aggregates and organic matter is imperative, which is key to developing a theoretical basis for the sustainable utilization of saline water resources, particularly in extremely arid regions. This experiment was conducted to investigate the impact of different irrigation water salinity treatments (T3: 3 g/L, T5: 5 g/L, and T7: 7 g/L) on the root zone soil of cotton fields. Each salinity treatment included three variations of the sodium adsorption ratio (SAR) at S10: 10 (mmol/L)1/2, S15: 15 (mmol/L)1/2, and S20: 20 (mmol/L)1/2. Local freshwater irrigation served as the control, resulting in a total of 10 treatments. Our findings show that the soil Ca2+ and Mg2+ content increased with higher irrigation water salinity but decreased with increasing irrigation water SAR. The relative macroaggregate stability and the content of water-stable macroaggregates and soil organic matter (SOM) decreased as the irrigation water salinity and SAR increased. In comparison to T3S20, T5S10 did not improve the soil Na+ content but significantly increased the soil Ca2+ content by 147.76%, while the water-stable aggregate and SOM saw a notable increase of 7.66% and 9.86%, respectively. Reducing the SAR in brackish water lessens its negative impact on soil aggregates in cotton fields. This is primarily because Ca2+ counteracts the dispersive effect of high Na+ concentrations and promotes aggregate formation. Irrigation water with a salinity of 3 g/L and an SAR of 10 (mmol/L)1/2 positively affected the stabilization of soil aggregates and organic matter.

Effect of Land Cover Variations on the Fertility Status of Soils of Umuhu in Ngor-Okpala Area of Imo State

The study was conducted to ascertain the effect of four different land covers (cassava cultivated field (CCF), oil palm plantation (OPP), plantain plantation (PP) and forest land (FL)) on the fertility status of soils of Umuhu in Ngor-Okpala area of Imo State, Nigeria. Random sampling technique was used in the collection of soil samples from the four different land covers. The sampling was done at the beginning, middle and end of each land cover. Twelve (12) composite samples were collected from all the land cover types with 3 per land cover. The composite samples were prepared for routine laboratory analyses. Data generated were analyzed statistically using analysis of variance. The textural classes of all the sampled soils were of loamy sand. The soil which had plantain plantation as its cover had the highest pH (6.4), Total N (0.229 %), Soil organic matter 4.70%, Available P (27.05 mg kg-1), Exch. Ca (6.492 cmolc kg-1), Exch. Mg (3.942 cmolc kg-1), Exch. K (0.953 cmolc kg-1), Exch. Na (0.06 cmolc kg-1), Exch. H (1.2 cmolc kg-1) and CEC (28.4 cmolc kg-1) with its Exch. Al in trace amount (&lt;0.001 cmolc kg-1). The soil under CCF, despite being under low cover, did not show much degeneration due to the shifting cultivation being practiced in the study location. However, the result obtained from the study indicated that the different land covers especially that under plantain plantation (PP) have affected the soils fertility at different rates. This observed factor is strongly controlled by high content of organic materials, a dense vegetative cover which mitigates erosion effects and the addition of ash as a means of fertilizing the soils under plantain plantation being practiced in the study area.

Effects of mulch films with different thicknesses on the microbial community of tobacco rhizosphere soil in Yunnan laterite.

The mulch film (MF) management model of the agricultural field affects the physical and chemical properties of soil (PCPS) and the structure of the microorganism community; however, studies on the relationship between the rhizosphere microorganism community structure and the thickness of MF are still limited. To understand the interactions among the MF thickness, PCPS, and rhizosphere microorganism, a study was conducted by using an integrated metagenomic strategy, where tobacco rhizosphere soil was treated with four commonly representative and used thicknesses of MFs (0.004, 0.006, 0.008, and 0.010 mm) in Yunnan laterite. The results showed that agronomic traits such as the tobacco plant height (TPH), leaf number (LN), fresh leaf weight (FLW), and dry leaf weight (DLW) were significantly (p < 0.01) improved in the field mulched with the thickest film (0.010 mm) compared with the exposed field (CK), and there was a 6.81 and 5.54% increase in the FLW and TPH, separately. The correlation analyses revealed a significant positive correlation of the MF thickness with the soil water content (SWC), soil organic matter (SOM), total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), and available phosphorus (AP; all p < 0.01), while the MF thickness was negatively correlated with the soil temperature (ST; p < 0.01). In addition, the community structure of the rhizosphere soil bacteria was significantly changed overall by the MF thickness, which also interfered with the function of the rhizosphere soil bacteria. The correlation analyses also showed that the abundance of Bradyrhizobium and Nitrospira was positively correlated with the MF thickness, while the abundance of Sphinsinomonas and Massilia was negatively correlated with it. This indicated that with the increase of the MF thickness, the ability of the rhizosphere soil to utilize N and remove harmful molecules was strengthened, while the capacity of the rhizosphere soil to degrade pollutants was greatly reduced. These findings provide additional insights into the potential risks of the application of different thicknesses of MFs, particularly concerning the PCPS and soil microbial communities.

Применение биоугля на основе отработанных грибных блоков в условиях агротемно-серых почв

Recycling of organic waste from mushroom production will improve their environmental safety and optimize the applied agricultural technologies. The aim of the work was to assess the environmental performance of the agricultural technology of using a soil fertilizing material – biochar obtained from spent lignin-cellulose mushroom blocks. It was found that the introduction of biochar from mushroom production waste materials into Gray-Luvic Phaeozems Hortic helps stabilize soil organic matter and increase the productivity of lawn grasses. It was noted that the quality and agroecological efficiency of biochar obtained from spent mushroom blocks based on cereal straw are significantly higher than biochar from spent mushroom blocks based on sunflower husk. Keywords: SOIL ORGANIC MATTER, CO2 EMISSION, SUNFLOWER HUSK, LAWN GRASSES, OYSTER MUSHROOM

Impact of fertilizer doses on soil properties, vegetative growth, fruit quality and biochemical compounds of strawberry (Fragaria × ananassa Duch)

Fertilizers are important for plant growth, yield enhancement, and achieving food security, but overdose can have negative effects. This study sought to determine the impact of different fertilizer doses on soil properties, vegetative growth, fruit quality, and biochemical compounds of strawberry (Fragaria × ananassa Duch) cv. ‘Camarosa’. During the years 2022-2023, strawberry seedlings were grown in pots in a greenhouse. Four increasing dosages of fertilizers were applied. The results showed that following treatment, electrical conductivity and soil organic matter rose to maximum values of 176.26 µS. cm-1 and 2.63%, respectively, with d2 treatment. However, the pH was initially high before dropping considerably to 7.34 with d4 dosage. Treatment d1 was highly suggested for enhanced fruit number (5.8) and total yield (729 g. plant-1). The treatment d2 produced the highest fruit weight (24.3 g), volume (27.71 cm3), length (5.55 cm), and width (5.15 cm). The medium dose d3 drastically increased leaf area (2652.76 cm2), total soluble solids (7.4 °Brix), total phenols (1,332.54 mg GAE· L-1) and antioxidant activity (89.53%), but not significantly. The maximum petiole length (12.66 cm), petiole number (29.4), chlorophyll content, runners number (6), roots length (22.33 cm), fresh root and shoot weight (73.11 and 96.41 g), root and shoot dry weight (10.84 and 30.64 g), were recorded at d4 treatment. In control plants, all of these measures were lower, despite having higher fruit pH (3.72), titratable acidity (0.87%), and flowers number (4.40). In conclusion, increasing fertilizer doses may affect soil and strawberry plant qualities, and farmers must use them appropriately.

Effect of altitudes and aspects on carbon sequestration potential of Quercus floribunda forests of Garhwal Himalayas

The forests are major resources for carbon sequestration and help to mitigate the adverse effect of atmospheric carbon and reduce global warming. The present study was conducted to estimate the carbon sequestration potential of the Quercus floribunda forests at two different aspects and three altitudes. Ten quadrates of 10 × 10 m size were laid out in each forest for the estimation of stand density, tree biomass, and soil samples were collected from each quadrate. Q. floribunda was the dominating tree at studied altitudes and aspects with the IVI values of 161.14 and 124.96 in the southern aspect and northern aspects, respectively. the highest values of above-ground biomass density (AGBD), below-ground biomass density (BGBD), total biomass density (TBD), and total carbon density (TCD) was recorded at the upper elevation (2500–2700 m) of southern and northern aspects. In the southern aspect values of AGBD (476.67 < 575.67 Mg/ha), BGBD (124.8 < 148.9 Mg/ha), TBD (601.53 < 724 Mg/ha), TCD (300.83 < 362.03 Mg/ha) were higher than northern aspect. The values of AGBD, BGBD, TBD, and TCD were reported maximum (638 Mg/ha, 163.1 Mg/ha, 800.5 Mg/ha, and 400.35 Mg/ha; respectively) in the upper elevation. Soil organic carbon (SOC), soil organic matter (SOM), and soil organic carbon stock (SOCS) decreased with increasing altitudes and depths which were found higher in the southern aspect. Bulk density (BD) and P increased with altitudes and depth however bulk density was equal (1.29 g cc-1) in both aspects whereas P was also found higher (31.43 kg/ha) in the southern aspect. Highest available nitrogen (398 kg/ha) was recorded in the northern aspect at middle altitude. The available potassium was highest in the northern aspect. At lower altitudes, available potassium ranges between 246–615 kg/ha. Soil pH was found slightly acidic in all the sites ranging from 4.91 to 5.74 in different soil depths. Dehydrogenase activity was ranged between 1.35 and 8.74 µg/g/h from lower to upper soil depth and decreased with an increase in soil depths and increased with altitudes, whereas found highest in the southern aspect. The present study suggested that tree density, tree biomass, carbon sequestration potential, and soil health in Q. floribunda forests were substantially influenced by the altitude as well as the aspect. These findings contribute valuable insights for climate change mitigation and forest management strategies in the study region.

Carbon sequestration through conservation tillage in sandy soils of arid and semi-arid climates: A meta-analysis

This meta-analysis assessed soil organic carbon (SOC) percent changes in sandy soils, transitioning from conventional tillage (CT) to conservational tillage (CST) in arid and semi-arid climates. High levels of SOC in sandy soils are difficult to attain especially when precipitation levels are very low, contributing to low biomass production, and increased decomposition of organic matter. While CT practices are known to reduce SOC through the breakdown of soil aggregates, accelerated decomposition of soil organic matter, and promote erosion, CST methods (i.e., mulch tillage, no tillage, reduced tillage, ridge tillage, etc.) offer the potential to preserve soil aggregates and increase SOC concentration. Analyzing 55 peer-reviewed publications in arid and semi-arid climates with ≥ 45 % sand content, this study compared SOC content between CST and CT over short- and long-term periods (349 paired observations). Results showed that CST increased SOC in sandy soils, with an estimated 12.74 ± 1.46 % increase. Specifically, reduced tillage (RdT), mulch tillage (MchT), and no tillage (NT) exhibited the highest increases of SOC by 18.94 ± 2.48 %, 11.45 ± 2.46 %, and 10.06 ± 2.46 %, respectively, compared to CT. Studies with durations of up to 15 years (n = 297) showed a progressive increase in SOC concentrations under CST; however, the long-term stability of the accrued carbon content in sandy soils of arid and semi-arid climates is still uncertain, as studies extending beyond 15 years (n = 52) did not demonstrate significant changes in SOC levels. CST significantly raised SOC concentrations in precipitation up to 600 mm, though no significant changes were observed for precipitation over 600 mm. In soils with over 56 % sand content, CST increased SOC by approximately 13 %. This study highlights both positive and limited impacts of CST practices for soil conservation and climate change mitigation, emphasizing their significance for both existing agricultural areas in arid regions and those in parts of the world where aridity is on the rise.

An Overview of the Soil Acidity Causes in Ethiopia, Consequences, and Mitigation Strategies

Soil acidity is a serious land degradation problem and worldwide danger, impacting approximately 50% of the world&amp;apos;s arable soils and limiting agricultural yield. Soil acidification is a complicated series of events that lead to the production of acidic soil. In its widest sense, it can be defined as the total of natural and human processes that reduce the pH of soil solutions. Soil acidity affects around 43% of agricultural land in Ethiopia&amp;apos;s humid and sub humid highlands. The main objective of this seminar is to highlight different literatures on the concepts of soil acidity and to give a wealth of knowledge on the causes of soil acidity, the effects it has on agricultural production, and management strategies for reducing soil acidity and raising crop yield. Acid soils in western Ethiopia are mostly caused by topsoil erosion caused by heavy rains and high temperatures. This results in the loss of organic matter and the leaching of exchangeable basic cations (Ca&amp;lt;sup&amp;gt;2+&amp;lt;/sup&amp;gt;, Mg&amp;lt;sup&amp;gt;2+&amp;lt;/sup&amp;gt;, Na&amp;lt;sup&amp;gt;+&amp;lt;/sup&amp;gt;, and K&amp;lt;sup&amp;gt;+&amp;lt;/sup&amp;gt;). Because ammonium-based fertilizers are easily converted to nitrate and hydrogen ions in the soil, they play a significant role in acidification. One of the reasons of soil acidity is inefficient nitrogen usage, which is followed by alkalinity exports in crops. Soil acidity in Ethiopian highlands is mostly caused by the clearance of crop residues, continuous crop harvest without sufficient fertilization, cation removal, and usage of acid-forming inorganic fertilizers. Acid soil reduces nutrient availability and produces Al and Mn toxicity. In addition to these effects, soil acidity may rapidly degrade soil physicochemical qualities such as organic carbon (OC), cation exchange capacity (CEC), soil structure, porosity, and texture. Liming, the use of organic materials as ISFM, and the adoption of crop types that are resistant to Al toxicity are all alternatives for correcting acid soils. Liming can minimize toxicity by lowering concentrations, improving the availability of plant nutrients like P, Ca, Mg, and K in the soil, and reducing heavy metal solubility and leaching. Application of organic matter has a liming impact because of its abundance in alkaline cations (such Ca, Mg, and K) that were released from OM during mineralization. The pH of the soil is raised by soil organic matter, which helps with soil acidity supplements.

A rhizosphere effect promotes the persistence of gas oxidization activity in soil

Labile carbon and nutrients of the rhizosphere promote the activity of trace gas oxidizing bacteria (TGOB), but the capacity of the rhizosphere effect to support their persistence upon activation has received less attention. Here, we hypothesized that the activation response of TGOB in soil before planting is proportional to the persistence of their activity after wheat growth. The TGOB were activated in sandy-loam and peat soils under a static atmosphere containing elevated concentration of hydrogen (H2), carbon monoxide (CO) or methane (CH4). Our hypothesis was proven to hold true in sandy-loam soil, whereas higher organic matter in peat soil was less favourable for the persistence of TGOB activity. We conclude that the energy potential of the trace gas oxidation reaction and soil nutrients both intervein in the persistence of TGOB activity.

Responses of soil microbial metabolism, function and soil quality to long-term addition of organic materials with different carbon sources

Biochar and green manure have been widely applied in agricultural production and are important means to achieve sustainable agriculture. However, there is limited research systematically and comprehensively exploring the response of soil microbiota and the changes in soil metabolomics after the addition of two different carbon source amendments to the soil, and the differential mechanisms of soil metabolomics between them remain unclear. In this study, a long-term field experiment (initiated in 2019) was conducted to investigate the effects of biochar and green manure application on soil nutrients and soil functions driven by soil microbes. Compared to the pure fertilizer treatment, biochar increased soil total carbon by 14.54% to 27.04% and soil available potassium by 4.67% to 27.46%. Ryegrass significantly increased soil available phosphorus and organic matter. Under different fertilization regimes, the ecological niches of soil microbes changed significantly. Network analysis revealed that long-term ryegrass returning reduced the complexity of soil microbial networks. Ryegrass and biochar increased dispersal limitation in fungal assemblages (reaching 93.33% and 86.67%, respectively), with biochar particularly enhancing variable selection in bacterial assemblages (accounting for 53.33%). Variation partitioning analysis based on redundancy analysis indicated that humic substances had the highest explanatory power for microbial community variation, with humic substances explaining 38.49% of bacteria and 52.19% of fungi variation. The ryegrass treatment mainly changed the abundance of carbohydrates (CH), amines (AM), c (AH), and lipids (LP), while the BC treatment mainly altered the abundance of organic acids (AC), amines (AM), and carbohydrates (CH). Meanwhile, both treatments significantly reduced the bisphenol A, one of the soil pollutants. Ryegrass incorporation significantly increased the abundance of genes related to soil C, N, P, and S cycling, especially genes involved in carbon decomposition, while biochar significantly enhanced the abundance of nitrogen fixation genes nifH and Hao in soil. Random forest model results indicated that carbohydrates, alcohols, aromatics (AR), and ester (ES) were the main categories of metabolites in soil influenced by differential microbes, and Finegoldia served as a common important metabolic driving species. In summary, this study reveals the processes of soil function, microbial community succession, and metabolism driven by ryegrass and biochar, providing important insights for optimizing soil management and improving soil quality.Graphical

Accurate quantification of soil organic matter content using VNIR-SWIR spectra: The role of straw and spectrally active materials

Soil organic matter (SOM) is crucial for carbon sequestration and sustainable agriculture, yet traditional quantification methods are challenging to apply at large scales. Hyperspectral technology combined with machine-learning offers promising prospects for rapid quantification. This study explores the impact of using VNIR-SWIR spectra on SOM quantification in regions characterized by distinctive soil properties and agricultural activity. Specifically, we propose an innovative approach using 105 soil samples from Yueyang City, China, to refine the range of spectrally active materials and evaluate the effectiveness of iron oxides and straw on SOM quantification. Three feature construction methods (conventional (VNIR-SWIR spectra), optimal (information spectrum subset, ISS), and straw-merged ISS (SISS)) and seven models were employed to evaluate the contributions of iron oxides and straw in SOM quantification. The results indicate that the SISS improved the generalization (RPD and R2) of nonlinear and linear models by approximately 9 % and 4 %, respectively. The relative contributions of straw and iron oxides in modelling are approximately 35 % and 10 %, respectively. Our research successfully developed the SISS by refining the range of spectrally active materials and considering the background formed by the soil properties of the study area. We used it to evaluate the impact of straw on SOM quantification and demonstrated that the spectroscopic characterization of SOM can assess the carbon sequestration benefits of agricultural activities. This approach can be applied to regions with similar soil properties globally, offering a new perspective for SOM quantification.

Effect of potassium fulvate on continuous tobacco cropping soils and crop growth.

Long-term continuous cropping of tobacco causes dysbiosis of soil microbial communities, the imbalance of soil nutrients, and the increase of pathogenic bacteria, which will slow the growth and development of tobacco plants, reduce the production quality, and cause significant losses to tobacco production and tobacco farmers. The application of Potassium fulvic acid can not only provide nutrients, but also inhibit the propagation of pathogens in soil along with raising the amount of organic matter in the soil, which is an effective way to improve soil health. In this experiment, Tobacco variety SNT60 was used as the test material, and 6 treatments were set up by pot test, they were: no fertilisation control group (CK), tobacco special fertiliser (NPK), 3.45 g/kg of potassium fulvic acid fertiliser (T1), 4.65 g/kg of potassium fulvic acid fertiliser (T2), 5.85 g/kg of potassium fulvic acid fertiliser (T3), 7.05 g/kg of potassium fulvic acid fertiliser (T4), Ten replications were set up for each treatment and the soil and fertiliser were mixed and potted before transplanting, 70% as basal fertiliser and 30% as supplementary fertiliser. We also analyzed soil properties, soil microorganisms and agronomic traits of tobacco plants in different treatments to provide reference for mitigating tobacco succession barrier. The test results are as follows: 4.65 g/kg of potassium fulvic acid fertiliser (T2) treatment was the best, soil organic matter, quick nitrogen, phosphorus, potassium, pH, soil catalase, soil sucrase, and soil urease content, compared to CK control, increased by 22.04%, 43.12%, 96.21%, 381.79%, 25.43%, 91.69%, 262.07% and 93.16%. In terms of microbial community, application of potassium fulvic acid fertiliser significantly increased the relative abundance of Ascomycetes, Chlorobacterium, Bacillus, Proteobacteria and Tephritobacterium in the soil. Meanwhile, 4.65 g/kg of potassium fulvic acid fertiliser (T2) promoted the growth of tobacco plants, improved leaf photosynthetic capacity, and enhanced plant disease resistance. This experiment provides practical measures to improve the microbial community of tobacco continuous cropping soils and to reduce the incidence of diseases.

Ecological and Geochemical Assessment of the State of Soils in the City of Baikalsk According to the Content of Polycyclic Aromatic Hydrocarbons

The pollution of the topsoils of the city of Baikalsk (Irkutsk region) under the influence of industrial emissions and wastes of the Baikal Pulp and Paper Mill (BPPM) was studied. The content of 16 individual PAH structures in samples of urban and background soils taken during the soil geochemical survey in the summer of 2019 was analyzed. Relatively low levels of PAH content were found in the lignin sludge from the BPPM and СHP ash. The concentration of total PAHs in CHP ash reaches 46 mg/ kg with a predominance of low molecular weight compounds (the proportion of naphthalene and its homologues is 24% and 34% of the total PAHs, respectively), among high molecular weight PAHs, 5-nuclear benzo(b)fluoranthene dominates (16%). In lignin sludge, the amount of PAHs is 7.16 mg/kg with the predominance of benzo(b)fluoranthene (83%). In the soils of Baikalsk, the average total content of PAHs (38.4 mg/kg) is 5 times higher than the background content. In urban soils, 4–5-nuclear fluoranthene (61.1%) and benzo(b)fluoranthene (29.4%) prevail. This makes it possible to attribute soil pollution to the fluoranthene type. The soils of the motor transport (total PAH 105 mg/kg) and industrial (59.5 mg/ kg) zones are the most polluted, where the most contrasting PAH anomalies were formed. In descending order of the amount of PAHs, the land use zones of the city form a series: motor transport industrial residential one-storey railway transport residential multi-storey recreational zone. Several local anomalies in the amount of PAHs are distinguished, forming two large pollution halos in the western and eastern parts of the city. The leading factors in the accumulation of high molecular weight PAHs in soils are acid-alkaline conditions and soil organic matter, while the accumulation of low molecular weight polyarenes is mainly controlled by pH. The environmental hazard of pollution of Baikalsk soils with polyarenes is due to benzo(b)fluoranthene, its contribution is 83.5%.

Mechanisms of soil organic carbon and nitrogen stabilization in mineral-associated organic matter – insights from modeling in phase space

Abstract. Understanding the mechanisms of plant-derived carbon (C) and nitrogen (N) transformation and stabilization in soil is fundamental for predicting soil capacity to mitigate climate change and support other soil functions. The decomposition of plant residues and particulate organic matter (POM) contributes to the formation of mineral-associated (on average more stable) organic matter (MAOM) in soil. MAOM is formed from the binding of dissolved organic matter (ex vivo pathway) or microbial necromass and bioproducts (in vivo pathway) to minerals and metal colloids. Which of these two soil organic matter (SOM) stabilization pathways is more important and under which conditions remains an open question. To address this question, we propose a novel diagnostic model to describe C and N dynamics in MAOM as a function of the dynamics of residues and POM decomposition. Focusing on relations among soil compartments (i.e., modeling in phase space) rather than time trajectories allows isolating the fundamental processes underlying stabilization. Using this diagnostic model in combination with a database of 36 studies in which residue C and N were tracked into POM and MAOM, we found that MAOM is predominantly fueled by necromass produced by microbes decomposing residues and POM. The relevance of this in vivo pathway is higher in clayey soils but lower in C-rich soils and with N-poor added residues. Overall, our novel modeling in phase space proved to be a sound diagnostic tool for the mechanistic investigation of soil C dynamics and supported the current understanding of the critical role of both microbial transformation and mineral capacity for the stabilization of C in mineral soils.