Soil Enzyme Activities Research Articles

Polyaspartic calcium improved soil quality and altered nitrification process in saline‐sodic paddy soils

AbstractSaline‐sodic paddy soils in the Songnen Plain suffer from nitrogen loss due to nitrification. The purpose of the study is to explore soil saline improvement and nitrification mitigation effects of polyaspartic calcium (PASP‐Ca) by evaluating changes of soil quality, nitrification, and microbial communities. Four PASP‐Ca application treatments (additions of 0, 500, 1000, and 1500 kg hm−2) were studied in an experiment in saline‐sodic paddy soils of the Songnen Plain, China. Results showed that PASP‐Ca application significantly decreased soil pH, electrical conductivity (EC), and water‐soluble salt ions, and significantly increased soil total carbon (TC), total nitrogen (TN), urease activity (UA), and sucrase activity (SA). PASP‐Ca application significantly slowed down soil nitrification, which was manifested in a significant increase in ammonium nitrogen () and a significant decrease in nitrate nitrogen () and ammonia monooxygenase activity (AMO). The composition and distribution of soil nitrifying microbial communities were affected by soil salinity, nutrient, and enzyme activities. Ammonia‐oxidizing bacteria (AOB) plays an important role in the nitrification process of saline‐sodic paddy soils, while PASP‐Ca application significantly inhibited nitrification by suppressing AOB amoA gene abundance. This study shows that PASP‐Ca, as an effective amendment, can improve soil salinization and slow down nitrification, which has an important role and significance in improving nitrogen utilization and reducing nitrogen loss of saline‐sodic soils.

Field-scale assessment of vermicompost amendments for diuron-contaminated soil: Implications for soil quality and pesticide fate

This comprehensive study investigated the distribution, dissipation, and environmental impact of diuron and its metabolites (DPMU, DPU, and DCA), as well as its effects on enzyme activities, bacterial abundance, and community composition in response to different soil treatments using two vermicomposts. One vermicompost was derived from vine shoot waste, and the other from wet olive cake (alperujo). The study was conducted under field conditions in a semi-arid region. The results indicated that diuron concentrations decreased with soil depth, with the highest levels in the upper 0–5 cm layer. The application of both vermicomposts reduced diuron leaching into the soil, facilitating its dissipation compared to the organically unamended soil. DPMU was the main metabolite detected in the soil, especially at the end of the experiment. Enzyme activities, including dehydrogenase, β-glucosidase, protease, and acid phosphatase, showed variations with treatment and time, indicating microbial adaptation. In general, both vermicomposts increased soil enzyme activities, even when diuron was co-applied. Bacterial communities were affected by diuron and vermicomposts, with Actinobacteria and Alphaproteobacteria showing significant shifts in relative abundance. Principal Component Analysis (PCA) confirmed structural changes in bacterial communities due to diuron and vermicomposts. Warmer temperatures and evapotranspiration may contribute to the distribution of diuron in the different layers of soil and affect microbial activity. Overall, vermicomposts from wet olive cake proved effective in mitigating diuron in the different soil layers, promoting enzyme activities, and influencing bacterial communities. These findings underscore the complexity of interactions between diuron, organic amendments, and soil microorganisms, highlighting the potential for enhanced herbicide dissipation and microbial resilience and adaptation.

Environmental risks of mask wastes binding pollutants: Phytotoxicity, microbial community, nitrogen and carbon cycles

The increasing contamination of mask wastes presents a significant global challenge to ecological health. However, there is a lack of comprehensive understanding regarding the environmental risks that mask wastes pose to soil. In this study, a total of 12 mask wastes were collected from landfills. Mask wastes exhibited negligible morphological changes, and bound eight metals and four types of organic pollutants. Masks combined with pollutants inhibited the growth of alfalfa and Elymus nutans, reducing underground biomass by 84.6 %. Mask wastes decreased the Chao1 index and the relative abundances (RAs) of functional bacteria (Micrococcales, Gemmatimonadales, and Sphingomonadales). Metagenomic analysis showed that mask wastes diminished the RAs of functional genes associated with nitrification (amoABC and HAO), denitrification (nirKS and nosZ), glycolysis (gap2), and TCA cycle (aclAB and mdh), thereby inhibiting the nitrogen transformation and ATP production. Furthermore, some pathogenic viruses (Herpesviridae and Tunggulvirus) were also found on the mask wastes. Structural equation models demonstrated that mask wastes restrained soil enzyme activities, ultimately affecting nitrogen and carbon cycles. Collectively, these evidences indicate that mask wastes contribute to soil health and metabolic function disturbances. This study offers a new perspective on the potential environmental risks associated with the improper disposal of masks.

Conservation tillage increases nutrient accumulation by promoting soil enzyme activity: a meta-analysis

Conservation tillage increases nutrient accumulation by promoting soil enzyme activity: a meta-analysis

Combining Organic and Inorganic Fertilization Enhances Soil Enzyme Activity, the Bacterial Community, and Molecular Ecological Network Complexity in Coal Mine Reclamation Areas

Combined organic and inorganic fertilization can improve soil fertility in coal mine reclamation areas. However, the contribution of the bacterial community (especially its occurrence patterns) to soil physicochemical properties and enzyme activity needs further evaluation. The objective of this research was to clarify the bacterial community diversity, composition, and intraspecific interactions in response to combined organic and inorganic fertilizer application in coal mine reclamation areas in the Loess Hilly Region, China. Maize rhizosphere soil samples were collected under four fertilization regimes (CK, no fertilization control; NPK, compound inorganic fertilizer; M, organic fertilizer; and NPKM, combined organic and inorganic fertilization) in a 10-year field experiment in Gujiao city, Shanxi Province. Bacterial communities were characterized using high-throughput sequencing of the 16S rRNA gene V3–V4 region. A cross-treatment Spearman correlation network was constructed to explore the bacterial co-occurrence patterns. Compared with CK, NPK, M, and NPKM decreased the pH by 0.59%, 2.27%, and 0.12%; increased the soil organic carbon by 11.25%, 11.69%, and 27.05%; and significantly decreased the bacterial Shannon diversity by 3.68%, 0.14%, and 3.54%, respectively. Compared with CK, NPKM significantly increased sucrase, urease, and alkaline phosphatase activities (p < 0.05). Critically, oligotrophic Acidobacteria were significantly more abundant in CK than in the other treatments. Gemmatimonadetes were more abundant in NPK and M, and Actinobacteria, Bacteroidota, and Patescibacteria were more abundant in NPKM. In addition, network analysis revealed that the keystone taxa in the different fertilization treatments belonged to different network modules and were significantly correlated with soil nutrient content and enzyme activity. Simultaneously, the Actinobacteria enriched in NPKM formed specific clusters through strong symbiosis, and there were significant positive correlations among sucrase, urease, and alkaline phosphatase. In summary, long-term combined organic and inorganic fertilization improved maize rhizosphere soil fertility by regulating enzyme activity, bacterial community composition, and bacterial species interactions in coal mine reclamation areas in the Loess Hilly Region.

Assessment of Soil Enzyme Activities in Plant Root Zone of Saline Soil Reclaimed by Drip Irrigation with Saline Groundwater

Drip irrigation with saline water is frequently adopted to realize the sustainable utilization of saline–sodic soil with high water tables, and soil enzyme activities can be used to indicate changes in soil quality. In the current study, spatiotemporal changes in soil urease enzyme (URE), alkaline phosphatase (ALP) and invertase (INV) activities were investigated during consecutive growing seasons. Soil in beds was sampled before planting (0 y) and one, two, three and four years after the growing season (1 y, 2 y, 3 y, 4 y), and these samples were distributed at four horizontal distances from the drip line (0, 10, 20 and 30 cm) and four vertical soil depths (0–10, 10–20, 20–30 and 30–40 cm). The results showed that a distribution pattern of URE and ALP activities formed during the first growing season, while the distribution of INV activity formed until the third growing season. All three soil enzyme activities in the upper soil layers and positions close to the drip line were more greatly affected by planting year. The average URE activity of the soil profile decreased slightly during the first year and increased by about 220% and decreased by 20% after reclamation for two and three years, and finally, it increased to 4.9 μg NH4+·g−1·h−1 at the end of the fourth growing season. ALP activity remained stable during the first two years and rapidly increased in the following years; in particular, in the fourth year, it reached 32.7 μg ph(OH)·g−1·h−1. INV activity increased continually with the number of years after planting and reached 1009.0 μg glu·g−1·h−1 at the fourth season’s end. An analysis of variance indicated that URE, ALP and INV activities varied insignificantly among the time points of 0 y, 1 y, 2 y and 3 y (p < 0.05), while they were significantly higher for 4 y than for 0 y and 1 y. In addition, all three enzyme activities of the soil profile had an exponentially increasing trend with the number of years after planting. These results indicated the soil quality in saline–sodic soils could be improved with time under drip irrigation with local saline groundwater, especially around the drip line.

Time since fire affects ecological stoichiometry of plant–soil–microbial systems of Betula platyphylla, a pioneer species in burnt areas of China’s boreal forest

Plant stoichiometry and nutrient allocation may reflect adaptation strategies to environmental nutrient changes. Fire, as a major disturbance in forests, mediates soil nutrient availability that may influence plant nutrient dynamics. However, plant–soil stoichiometric allocation strategies during different post-fire periods and the effects of soil, enzymes, and microbial biomass on plant stoichiometry are largely unknown. The pioneer tree species Betula platyphylla in burnt forests of northern China was the object of this study, and severely burned areas selected with different fire years. Nearby unburned areas acted as a control. Carbon (C), nitrogen (N), and phosphorus (P) contents in leaves, branches, and fine roots and rhizosphere soil, C-, N- and P-acquiring enzyme activities were examined. Microbial biomass C, N, and P were measured, and factors influencing C:N:P stoichiometry of plants during the burned area restoration were explored. Our results show that C and N contents in leaves increased with time since fire, while C and P in branches and C, N and P in fine roots decreased. Activities of C-, N-, and P-acquiring enzymes and microbial biomass N increased with time since fire. Redundancy analysis showed that changes in soil N-acquiring enzyme activity, microbial biomass C, and N had significant effects on plant ecological stoichiometry. These results show a significant flexibility in plant nutrient element allocation strategies and C:N:P stoichiometric characteristics. Soil extracellular enzyme activity drives the changes in stoichiometry during the process of post-fire restoration.

Kinetic and thermodynamic parameters of urease in soils with different fertilization regimes

In recent years the growing demand for food led to intensification of agricultural practices, especially by the excessive use of fertilizers, which increased the environmental pollution. Therefore, pollution control by improving the efficiency of fertilizers and reducing their application is of great interest. Urease is one of the most active hydrolases in soil, having an important role in soil N cycle and being used as an indicator of soil quality. The objective of this study was to assess the urease activity in soils with different fertilization treatment, as well as its kinetic and thermodynamic parameters to better understand its driving factors. The results show a better enzymatic activity in soils treated with combined manure and mineral fertilizers. Soil urease has two optimal pH values, in the neutral and basic domains. Enzymatic activity has a steep increase with the temperature in the interval 45–65°C. The KM values increase with temperature from 11 to 23.5 mM, indicating a lower substrate affinity. The activation enthalpies for enzyme-substrate formation as well as for the rate limiting step are 7.59 and 14.18 kcal/mol respectively. The relationship between urease activity and microbial biomass will be further investigated.

Recover of Soil Microbial Community Functions in Beech and Turkey Oak Forests After Coppicing Interventions

Forest management influences the occurrence of tree species, the organic matter input to the soil decomposer system, and hence, it can alter soil microbial community and key ecosystem functions it performs. In this study, we compared the potential effect of different forest management, coppice and high forest, on soil microbial functional diversity, enzyme activities and chemical-physical soil properties in two forests, turkey oak and beech, during summer and autumn. We hypothesized that coppicing influences soil microbial functional diversity with an overall decrease. Contrary to our hypothesis, in summer, the functional diversity of soil microbial community was higher in both coppice forests, suggesting a resilience response of the microbial communities in the soil after tree cutting, which occurred 15–20 years ago. In beech forest under coppice management, a higher content of soil organic matter (but also of soil recalcitrant and stable organic carbon) compared to high forest can explain the higher soil microbial functional diversity and metabolic activity. In turkey oak forest, although differences in functional diversity of soil microbial community between management were observed, for the other investigated parameters, the differences were mainly linked to seasonality. The findings highlight that the soil organic matter preservation depends on the type of forest, but the soil microbial community was able to recover after about 15 years from coppice intervention in both forest ecosystems. Thus, the type of management implemented in these forest ecosystems, not negatively affecting soil organic matter pool, preserving microbial community and potentially soil ecological functions, is sustainable in a scenario of climate change.

Improving Soil Quality and Yield of Intercropping-System Crops in a Dry Land Area through Plant Growth Promoting Rhizobacteria Application Frequency

The future of agriculture is prone to choose technology that can enhance the quality of the resources to support the sustainability of food production. Plant Growth Promoting Rhizobacteria (PGPR) is a reliable technology for future agriculture as it is environment-friendly, and able to optimize resource utilization and decrease external input. This research aimed to analyze the effect of PGPR (Pseudomonas fluorescens + Bacillus polymyxa) application frequency on chemical soil properties, a yield of an intercropping system in dry land, the in-between correlation of the parameters, and to determine the best PGPR application frequency. Randomized Complete Block Design (RCBD) was used in this research to put the treatment in the experimental unit properly. The treatments consisted of i) one-time application of PGPR at the planting time, ii) twice application of PGPR at the planting time and 15 Days After Planting (DAP), iii) three times application of PGPR at the planting time, 15 DAP and 30 DAP, iv) without application of PGPR as control. The results showed that PGPR application frequency improved chemical soil properties, yield, and total by-products as livestock feed. The activity of soil enzymes, nitrogenase, and phosphatase, was enhanced compared to the control. The application of PGPR in dryland areas is recommended to maintain soil fertility and support sustainable intercropping crop production. Further studies are needed to conduct mixed farming between agriculture, animal husbandry, clean energy (biogas), and organic fertilizer (residue from the biogas digester).

Effect of Nitrogen and Phosphorus on Soil Enzyme Activities and Organic Carbon Stability in Qinghai–Tibet Plateau

Alpine grassland ecosystems are the most important ecosystem type, exhibiting a high sensitivity to anthropogenic nitrogen (N) and phosphorus (P) inputs into terrestrial ecosystems and significantly affecting the carbon (C) cycle within these ecosystems. However, the effects of N and P additions on soil C stability and the processes of organic C transformation remain unclear. This study measured the soil enzyme activities and oxidizable C fractions over a 9-year period following N and P additions to an alpine meadow in the Qinghai–Tibet Plateau. It included four treatments: control (CK), N addition, P addition, and combined N and P addition (NP), utilizing statistical methods such as analysis of variance (ANOVA), correlation analysis, and redundancy analysis. The findings indicated that NP addition significantly increased the non-labile soil oxidizable C fraction in the topsoil layer. Redundancy and correlation analyses revealed strong associations between the vegetation characteristics, C-cycling enzyme activities, soil-oxidized C fractions, and SOC stability index. These results underscore the role of NP addition in enhancing SOC accumulation and stability in grassland ecosystems, with the soil vegetation properties and C source enzyme activities serving as key regulators of the SOC stability. This study offers valuable insights into predicting the SOC dynamics amid rising N and P availability, thereby elucidating the effect of nutrient addition on soil C-cycling mechanisms.

The Plant Growth Promoting Potential of Saline Tolerant Rhizobacteria under In vitro Saline Stressed Conditions

Since the beginning of agricultural operations, soil salinity has been one of the most significant abiotic variables limiting agricultural production. Saline tolerant plant growth-promoting rhizobacteria (PGPR) enhance nutrient equitation and soil enzyme activities, which serve as indicators of soil biological health, and help to correct nutritional imbalances in plants. Potential bioinoculants for boosting crop yield in saline agriculture include saline tolerant plant growth-promoting rhizobacteria (PGPR). Therefore, in the present study the potential saline tolerant rhizobacteria isolated from saline patches of Karnataka were screened for Exopolysacchride production and Phosphate solubilization and phytohormone production potential under in vitro saline conditions. The results revealed that among the eight organisms were the highest EPS production, phosphate solubilization and phytohormone production recorded by Bacillus subtilis GAN-4 and Staphylococcus cohnii MAN-3 under both normal and saline stressed conditions compared to other organisms. Therefore,these strains show potential as plant growth-promoting rhizobacteria (PGPR) for mitigating salinity in saline agriculture.

Pharmaceutical and Trace Metal Interaction within the Water-Soil-Plant Continuum: Implications for Human and Soil Health.

Unplanned water reuse for crop irrigation may pose a global health risk due to the entry of contaminants into the food chain, undesirable effects on crop quality, and impact on soil health. In this study, we evaluate the impact derived from the co-occurrence of pharmaceuticals (Phs), trace metals (TMs), and one metalloid within the water-soil-plant continuum through bioassay experiments with Lactuca sativa L. Results indicate that the co-occurrence of Phs and TMs has synergistic or antagonistic effects, depending on target contaminants and environmental compartments. Complex formations between drugs and TMs may be responsible for enhanced sorption onto the soil of several Phs and TMs. Concerning plant uptake, the co-occurrence of Phs and TMs exerts antagonistic and synergistic effects on carbamazepine and diazepam, respectively. With the exception of Cd, drugs exert an antagonistic effect on TMs, negatively affecting their uptake and translocation. Drug contents in lettuce edible parts do not pose any threat to human health, but Cd levels exceed the maximum limits set for leafy vegetable foodstuffs. Under Ph-TM conditions, lettuce biomass decreases, and a nutrient imbalance is observed. Soil enzyme activity is stimulated under Ph-TM conditions (β-galactosidase) and Ph and Ph-TM conditions (urease and arylsulfatase), or it is not affected (phosphatase).

Nano silica’s role in regulating heavy metal uptake in Calendula officinalis

BackgroundSoil contamination with heavy metals poses a significant threat to plant health and human well-being. This study explores the potential of nano silica as a solution for mitigating heavy metal uptake in Calendula officinalis.ResultsGreenhouse experiments demonstrated, 1000 mg•kg− 1 nano silica caused a 6% increase in soil pH compared to the control treatment. Also in 1000 mg. kg− 1 nano silica, the concentrations of available Pb (lead), Zn (zinc), Cu (copper), Ni (nickel), and Cr (chromium) in soil decreased by 12%, 11%, 11.6%, 10%, and 9.5%, respectively, compared to the control. Nano silica application significantly reduces heavy metal accumulation in C. officinalis exposed to contaminated soil except Zn. In 1000 mg.kg− 1 nano silica shoots Zn 13.28% increased and roots Zn increased 13% compared to the control treatment. Applying nano silica leads to increase the amount of phosphorus (P) 25%, potassium (K) 26% uptake by plant, In 1000 mg.kg − 1 treatment the highest amount of urease enzyme activity was 2.5%, dehydrogenase enzyme activity, 23.6% and the highest level of alkaline phosphatase enzyme activity was 13.5% higher than the control treatment.ConclusionNano silica, particularly at a concentration of 1000 mg.kg − 1, enhanced roots and shoots length, dry weight, and soil enzyme activity Moreover, it increased P and K concentrations in plant tissues while decreasing heavy metals uptake by plant.

Properties of psammozems of the Kama terraces above the floodplain and assessment of their sustainability to pollution by Cu and Cd

Pine forests growing on psammozems, found on sandy Kama terraces above the floodplain within the territory of Perm, encompass roughly 2 thousand hectares. The study was conducted on psammozems under the influence of advancing pollution caused by heavy metals, highlighting the significance of soil’s buffering capacity in preserving the ecosystem’s stability. It is of great interest to investigate the morphogenetic properties of psammozems and evaluate the risks linked to the accumulation of Cu and Cd in these soils through the analysis of changes in soil enzyme activity (catalase, urease, and invertase) and the occurrence of phytotoxicity. The psammozems found in the Kama region originated from periglacial sandy alluvium, which was deposited during glacial melting in the Mesozoic era. The variety of humus psammozems includes typical, podzolized, illuvial-ferruginous, and pseudofibrous subtypes. These soils are highly acidic, have a very low absorption capacity, low base saturation, and reduced activity of soil enzymes. The contents of Cu, Cd, Zn, and Pb in psammozems are notably lower compared to the regional soil clarks; however, in the underdeveloped humus horizons, the concentrations of these metals are slightly higher than in soil-forming sands. The experiment was conducted to determine the ecotoxicological load, where mixed soil samples from a 0–20 cm layer of humus psammozems were treated with solutions containing copper acetate and cadmium acetate. The application of solutions was done individually, with Cu and Cd ranging from 2.5 to 250 mg/kg of soil. Upon introducing Cu and Cd into the soil at the rate of 2.5–10 mg/kg, a decrease in invertase activity, deterioration of the physiological and biochemical parameters of the test crop (Lepidium sativum L.), along with the inhibition of Cd catalase activity, were observed.

Mineral Components, Organic Matter Quality and Soil Enzymatic Activity under the Influence of Differentiated Farmyard Manure and Nitrogen Fertilisation

Research was carried out on the impact of long-term use of cattle manure (30 t ha−1 FYM) and various doses of N (0, 40, 60 and 120 t ha−1) in the form of ammonium nitrate on the following soil parameters: salinity, hydrolytic acidity, total exchangeable base cations, cation exchange capacity, degree of base saturation of the sorption complex, total organic carbon and total nitrogen content, dissolved organic matter, fractional composition of organic matter and content of bioavailable macroelements: phosphorus, potassium and magnesium in the soil of a multi-year static field experiment. The activities of dehydrogenases, catalase, alkaline and acid phosphatase and proteases were also tested. A significant effect of FYM and N fertilisation on the content of bioavailable macroelements was found. The application of manure at a dose of 30 t ha−1 mitigated the negative effects of the application of N at a dose of 120 kg ha−1. A higher content of total organic carbon (8.42 g kg−1) and humic acid fraction (1761 mg kg−1) and higher values of the CHA/CFA ratio (0.79; parameters that are indicators of soil quality) were found in the soil fertilised with manure compared to the soil without manure added (TOC—7.00 g kg−1; CHAs—1285 mg kg−1; CHAs/CFAs 0.66). The activity of the tested enzymes was also significantly determined by the applied fertilisation. Enzyme activity was highest in the soil to which manure had been applied. Nitrogen fertilisation varied in its impact on the activity of enzymes according to the specifics of each enzyme. The content of humic acids and CHA/CFA values correlated positively with the content of soil minerals and the activity of dehydrogenases, catalase, alkaline and acid phosphatase and GMea and TEI indices. Dehydrogenases and acid phosphatase can be considered enzymes that take part in transforming organic matter towards the formation of FAs.

Biodegradation of phenol-contaminated soil and plant growth promotion by Myroides xuanwuensis H13.

Physicochemical methods for remediating phenol-contaminated soils are costly and inefficient, making biodegradation an environmentally friendly alternative approach. This study aims to screen for potential phenol-degrading bacteria and to verify the removal capacities of a selected strain in a bioaugmentation experiment at the greenhouse level using Brassica chinensis L. (Chinese cabbage) as the model plant and phenol-contaminated soil. In parallel, pot experiments were conducted using a collaborative approach based on this model system. We found that Myroides xuanwuensis strain H13 showed a high degradation capability, with a 97.67% efficiency in degrading 100 mg/L phenol. Under shaking flask conditions, H13 facilitated the solubilization of tricalcium phosphate and potassium feldspar powder. Pot experiments suggested a phenol removal percentage of 89.22% and enhanced availability of soil phosphorus and potassium for plants with H13 inoculation. In this case, the abundance of soil microbes and the activity of soil enzymes significantly increased as well. Furthermore, both photosynthesis and the antioxidant system in Chinese cabbage were enhanced following H13 inoculation, resulting in its increased yield and quality. Partial least squares path modeling revealed that H13 can primarily affect plant root growth, with a secondary impact on photosynthesis. These findings highlight the potential of biodegradation from phenol-degrading bacteria as a promising strategy for efficient phenol removal from soil while promoting plant growth and health.IMPORTANCEThis study is significant for environmental remediation and agriculture by its exploration of a more environmentally friendly and cost-effective bio-strategy in treating phenol-contaminated soil. These findings have essential implications for environmental remediation efforts and sustainable agriculture. By utilizing the biodegradation capabilities of Myroides xuanwuensis strain H13, it is possible to remove phenol contaminants from the soil efficiently, reducing their negative effects. Furthermore, the enhanced growth and health of the Chinese cabbage plants indicate the potential of this approach to promote sustainable crop production.

Soil water content and RubisCO activity control the carbon storage in soil under different land uses in Sanjiang Plain, China

Soil carbon storage plays a crucial role in mitigating the climate warming and is significantly impacted by the land use pattern. To better understand soil carbon stability and the underlying microbial mechanism, based on qPCR, ELISA, and fluorescence techniques, the effects of land use changes on soil microbial abundance, enzyme activity, and soil carbon storage were investigated in the complex ecosystems of cropland, forestland, and wetland along three typical river (Wolvlan river, Bielahong river, Wusuli river) basin in Sanjiang Plain, China. We hypothesised that croplands soil carbon storage is lower than forestlands and wetlands, which is regulated by soil water content, microbe and enzyme activity. Results showed that topsoil TC in wetlands (85.54 mg·g−1) was higher than those in croplands (33.46 mg·g−1) and forestlands (46.13 mg·g−1). Topsoil water content increased 73.90 % and 71.64 % in wetlands than in farmland and forestlands, respectively. Additionally, reclamation diminished topsoil carbon storage. In croplands, soil dissolved organic carbon, microbial biomass carbon, microbial biomass nitrogen, available nitrogen, bacterial abundance, and soil enzymes (i.e., RubisCO, β-glucosidase, cellobiohydrolase, 1,4-N-acetylglucosaminidase and acid phosphatase) activities were substantially lower than those in wetlands. Structural equation modeling showed that soil carbon storage was positively related to soil water content and RubisCO activity but negatively related to soil bacterial abundance. Soil water content had the largest standardised total positive effect coefficient and indirectly influenced soil carbon storage by affecting RubisCO activity. Soil depth had a greater effect on SMC, hydrolase and site had a greater effect on bacteria and fungi abundance. The results highlight that the alteration of carbon fixing enzyme activity by soil water content is a crucial mechanism for soil carbon sequestration in response to land-use change. Management strategies that conserve natural wetlands, increase soil water content and minimize land disturbance would be effective in maintaining soil carbon stocks.

Alternative Cover Crops and Soil Management Practices Modified the Macronutrients, Enzymes Activities, and Soil Microbial Diversity of Rainfed Olive Orchards (cv. Chetoui) under Mediterranean Conditions in Tunisia

In Tunisia, the olive is the most cultivated fruit crop in the northern region, where annual rainfall exceeds 400 mm. This olive-growing area is characterized by a wide coverage of marginal soil with a high slope gradient. Therefore, the inclusion of cover crops in olive orchards is a sustainable solution to enhance ecosystem productivity, improve soil fertility, and increase oil yields. This study aimed to investigate the short-term (two cropping seasons in 2021 and 2022) effects of different seeded cover crops and soil management practices on soil characteristics, as well as soil health by measuring soil enzyme activities and microbial diversity. Six cover crop types consisting of wheat, vetch, oat, fenugreek, a vetch–oat mixture, and spontaneous vegetation were tested in association with rainfed olive trees (cv. Chetoui) in the north of Tunisia and compared to a control (which was tilled periodically three times per year without intercropping). During the first cropping season, cover crops were cut as animal feed, and only residues were incorporated into the soil. However, during the second year, all cover crop biomass was incorporated into the soil. The results indicated that the dry biomass production and carbon uptake were significantly higher in grass species (wheat and oat). All of the cover crops, including the spontaneous vegetation, significantly increased soil organic matter (SOM) and macronutrient levels, mainly, available phosphorus. On the other hand, the highest level of soil nitrogen was found in the fenugreek cover crop. The soil enzyme activities in the cover crops of wheat, oat, and the vetch–oat mix were higher than those in the control. Together with the increase in soil organic matter (SOM), this demonstrates a significant improvement in soil health with cover crops. Furthermore, this study proves that the utilization of carbon sources was dominated by amides, amines, and amino acids in the fenugreek plot, while it was dominated by polymers and carboxylic acids in the case of the wheat and oat. Overall, this study demonstrates that seeding cover crops is a sustainable management practice not only to integrate livestock but also to improve soil health in semiarid olive orchards.

Alterations in Soil Enzyme Activities in Response to New Generation Diamides

Alterations in Soil Enzyme Activities in Response to New Generation Diamides