Microbial Biomass Nitrogen Research Articles

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.

Seasonal changes in the phenolic compound contents and bioactivities in Betula platyphylla bark determined by soil properties

The white birch (Betula platyphylla Suk.) is widespread in eastern Asia, and its bark is a valuable resource for secondary metabolite extraction. Limited information is available regarding seasonal variations of secondary metabolites in white birch bark. In our study, we analyzed the phenolic compound contents and bioactivities of white birch bark in different seasons and their relationship to climatic factors and soil properties. The data suggested that the levels of total phenol, total flavonoid, seven individual phenolic compounds, and bioactivities all peaked in September. The antioxidant activity was positively correlated with the contents of phenolic compounds. Soil microbial properties like microbial biomass nitrogen (MBN) and soil urease activities (URE) explained more than 40 % of the variation in phenolic compound contents. This study highlighted that seasons regulate the contents of phenolic compounds and bioactivities by influencing soil microbial properties. The soil with low microbial activity was more favorable for the accumulation of secondary metabolites.

The Effects of Different Vegetation Restoration Models on Soil Quality in Karst Areas of Southwest China

Rocky desertification is a devastating process in Karst areas of Southwest China and induces serious fragmentation in ecosystems. Therefore, vegetation restoration and the scientific evaluation of soil quality are key restorative strategies in these areas. In this study, a natural closed forest and a disturbed forest with three restoration models, including an evergreen broad-leaved forest, mixed forest, and deciduous forest, were investigated in Huanjiang County. More than nineteen soil properties (including physical, chemical, and biotic properties) were analyzed across treatments, and principal component analyses (PCA) were combined with a minimum data set (MDS) applied to evaluate the soil quality. Our study sought to identify a vegetation restoration model to improve the soil quality in this area. We demonstrated that soil physical and chemical properties, microbial biomass, and enzyme activities significantly differed across all of the models. Soil water content, capillary porosity, total porosity, organic carbon, total phosphorus, available phosphorus, and urease activity were high in the mixed forest, leading to better physical soil properties. Also, relatively high soil total nitrogen, total potassium, available nitrogen, available potassium, microbial biomass C and N, catalase, sucrose, and alkaline phosphatase levels were observed in the deciduous broad-leaved forest, resulting in improved soil chemical properties. Based on the minimum data set (MDS) method, six indicators, including non-capillary porosity, organic carbon, total phosphorus, pH, microbial biomass nitrogen, and urease activity, were selected to evaluate the soil quality across the models. Our data showed that, among the five models, the deciduous broad-leaved forest had the highest soil quality index (0.618), followed by the mixed forest (0.593). Stepwise regression analysis showed that soil organic carbon explained 79.9% of the variations in the soil quality indices, suggesting it was a major factor affecting the soil quality. Thus, vegetation restoration models mainly comprised of native tree species effectively improved the soil quality in Karst rocky desertification areas, with deciduous broad-leaved forests displaying the best effects, followed by mixed forests.

Pear (Pyrus communis)-based agroecosystem improves soil nutrient dynamics, microbial biomass, enzymatic activity, farm productivity and profitability

North-western Indian farmers are increasingly showing interest in adopting horticulture-based systems to enhance their farm productivity with anticipated profits. So, there is a need for systematic evaluation of different pear-based agroecosystems with respect to its productivity, profitability, soil health, and biodiversity to tackle the problems of modern agriculture (food security, declining soil health, and sustainability). Therefore, an intercropping experiment comprising 11 treatments viz. [T1: Pear (Pyrus communis) + Pea (Pisum sativum), T2: Pear + Radish (Raphanus sativa), T3: Pear + Coriander (Coriandrum sativum), T4: Pear + Kasuri fenugreek (Trigonella corniculata), T5: Pear + fenugreek (Trigonella foenum-graecum), T6: Pear + Spinach (Spinacia oleracea), T7: Pear + Green onion (Allium fistolosum), T8: Pear + Cauliflower (Brassica oleraceae var. botrytis), T9: Pear + Toria (Brassica rapa), T10: Pear + Knol khol (Brassica oleraceae var. gongylodes) and T11: Pear monoculture] were laid out in randomized block design with three replications at farmer's field, Tarn Taran district, Punjab, India during 2021–22 and 2022–23. The results showed that the lesser values of bulk density (1.30 g/cm3) and higher water holding capacity (42.52%) were observed in the Pear + kasuri fenugreek intercropping system. All the legumes-based intercropping systems viz. Pear + kasuri fenugreek, Pear + fenugreek, and Pear + pea were significantly efficient in bringing enhancements to the chemical properties of the orchard's soil. Under various pear-based intercropping systems, different microbial populations (bacteria, fungi, actinomycetes, and diazotrophs) were significantly higher in legume-based intercropping systems of Pear + kasuri fenugreek, Pear + fenugreek, and Pear + pea and resulting in more enzymatic activity in the soil in terms of dehydrogenase (63.02, 61.88, and 60.48 µg TPF/g of soil/hour, respectively), alkaline phosphatase (10.05, 9.92, and 9.75 µg PNP/g of soil/hour, respectively) and urease (17.84, 17.18, 17.00 µg /g of soil/hour, respectively). The intercropping system of Pear + kasuri fenugreek significantly increased microbial biomass carbon (42.20%) and microbial biomass nitrogen (65.02%) over Pear monoculture. The correlation analysis of various soil's physiochemical and biological parameters indicated significant associations among themselves at p = 0.01, 0.05. The intercropping system of Pear + kasuri fenugreek also produced significantly higher system productivity in early (122.20 kg/ha/day in 2021–22 and 123.86 kg/ha/day in 2022–23) and main season (119.08 kg/ha/day in 2021–22 and 121.60 kg/ha/day in 2022–23) due to significantly higher pear yield (340.02 q/ha in 2021–22 and 341.89 q/ha in 2022–23) and higher pear equivalent yield (105.99 in early season, 94.64 q/ha in main season of 2021–22 & 110.20 in early season, 101.94 q/ha in main season of 2022–23) observed by kasuri fenugreek, resulting in higher net returns, BC ratio and economic efficiency in both seasons during both years over other intercropping systems.

Conservation tillage: a way to improve yield and soil properties and decrease global warming potential in spring wheat agroecosystems.

Climate change is one of the main challenges, and it poses a tough challenge to the agriculture industry globally. Additionally, greenhouse gas (GHG) emissions are the main contributor to climate change; however, croplands are a prominent source of GHG emissions. Yet this complex challenge can be mitigated through climate-smart agricultural practices. Conservation tillage is commonly known to preserve soil and mitigate environmental change by reducing GHG emissions. Nonetheless, there is still a paucity of information on the influences of conservation tillage on wheat yield, soil properties, and GHG flux, particularly in the semi-arid Dingxi belt. Hence, in order to fill this gap, different tillage systems, namely conventional tillage (CT) control, straw incorporation with conventional tillage (CTS), no-tillage (NT), and stubble return with no-tillage (NTS), were laid at Dingxi, Gansu province of China, under a randomized complete block design with three replications to examine their impacts on yield, soil properties, and GHG fluxes. Results depicted that different conservative tillage systems (CTS, NTS, and NT) significantly (p < 0.05) increased the plant height, number of spikes per plant, seed number per meter square, root yield, aboveground biomass yield, thousand-grain weight, grain yield, and dry matter yield compared with CT. Moreover, these conservation tillage systems notably improved the soil properties (soil gravimetric water content, water-filled pore space, water storage, porosity, aggregates, saturated hydraulic conductivity, organic carbon, light fraction organic carbon, carbon storage, microbial biomass carbon, total nitrogen, available nitrogen storage, microbial biomass nitrogen, total phosphorous, available phosphorous, total potassium, available potassium, microbial counts, urease, alkaline phosphatase, invertase, cellulase, and catalase) while decreasing the soil temperature and bulk density over CT. However, CTS, NTS, and NT had non-significant effects on ECe, pH, and stoichiometric properties (C:N ratio, C:P ratio, and N:P ratio). Additionally, conservation-based tillage regimes NTS, NT, and CTS significantly (p < 0.05) reduced the emission and net global warming potential of greenhouse gases (carbon dioxide, methane, and nitrous oxide) by 23.44, 19.57, and 16.54%, respectively, and decreased the greenhouse gas intensity by 23.20, 29.96, and 18.72%, respectively, over CT. We conclude that NTS is the best approach to increasing yield, soil and water conservation, resilience, and mitigation of agroecosystem capacity.

Aggregate stability and carbon and N dymamics in macroaggregate size fractions with different soil texture

Soil nutrient cycling, the distribution of soil aggregates, and their stability are directly influenced by soil texture. Different sizes of soil aggregates provide microhabitats for microorganisms and therefore influence soil carbon (C) and nitrogen (N) mineralization. The purpose of the present study was to assess the aggregate stability and dynamics of carbon and nitrogen in macroaggregate size fractions (1-8 mm) with different clay content from meadow soils. Surface soil samples (0-15 cm) were collected from 4- to 5-year-old forage crops. Four macroaggregate size classes were isolated by dry sieving and analyzed for their mass proportions: fine macroaggregates (FM) (less than 1 mm), medium-fine macroaggregates (MFM) (1-2 mm), medium-coarse macroaggregates (MCM) (2-4 mm), and large-coarse macroaggregates (LCM) (4-8 mm). The dry mean weight diameter (MWD), organic carbon (OC), total nitrogen (TN), carbon and nitrogen of microbial biomass (C-MB, N-MB) were determined. CO2 emission and net nitrogen mineralized (NM) were measured after 14 weeks of incubation. The amounts of FM were significantly lower than those of intermediate macroaggregates (MCM and MFM) and decreased markedly with increasing clay content within soil macroaggregates. In general, the amounts of macroaggregate size fractions were lowest in soils with high clay content. MWD exhibited a significant correlation with particle size distribution, OC, and MB-C. OC, TN, MB-C, and MB-N contents within macroaggregates increased with decreasing macroaggregate size and increasing clay content of macroaggregate fractions. The CO2 emission and NM content increased with increasing macroaggregate size, indicating higher organic C and N mineralization activity in larger macroaggregates. Mineralization of OC was lowest in macroaggregate fractions with the highest clay content. We conclude that clay content can increase the protection of microbial biomass in meadow soils. Small macroaggregates tend to contain more recalcitrant organic matter compared to larger macroaggregates.

Bacteria, Fungi, and Protists Exhibit Distinct Responses to Managed Vegetation Restoration in the Karst Region.

Bacteria, fungi, and protists occupy a pivotal position in maintaining soil ecology. Despite limited knowledge on their responses to managed vegetation restoration strategies in karst regions, we aimed to study the essential microbial communities involved in the process of vegetation restoration. We compared microbial characteristics in four land use types: planted forests (PF), forage grass (FG), a mixture of plantation forest and forage grass (FF), and cropland (CR) as a reference. Our findings revealed that the richness of bacteria and protists was higher in FF compared to PF, while fungal richness was lower in both PF and FF than in CR. Additionally, the bacterial Shannon index in FF was higher than that in CR and PF, while the fungal and protist Shannon indices were similar across all four land use types. Significant differences were observed in the compositions of bacterial, fungal, and protist communities between FF and the other three land use types, whereas bacterial, fungal, and protist communities were relatively similar in PF and FG. In FF, the relative abundance of bacterial taxa Acidobacteria, Firmicutes, and Gemmatimonadetes was significantly higher than in PF and CR. Fungal communities were dominated by Ascomycota and Basidiomycota, with the relative abundance of Ascomycota significantly higher in FF compared to other land use types. Regarding protistan taxa, the relative abundance of Chlorophyta was higher in FF compared to CR, PF, and FG, while the relative abundance of Apicomplexa was higher in CR compared to FF. Importantly, ammonium nitrogen, total phosphorus, and microbial biomass nitrogen were identified as key soil properties predicting changes in the diversity of bacteria, fungi, and protists. Our results suggest that the microbial community under FF exhibits greater sensitivity to vegetation restoration compared to PF and FG. This sensitivity may stem from differences in soil properties, the formation of biological crusts and root systems, and management activities, resulting in variations in bacterial, fungal, and protist diversity and taxa in PF. As a result, employing a combination restoration strategy involving plantation forest and forage grass proves to be an effective approach to enhance the microbial community and thereby improve ecosystem functionality in ecologically fragile areas.

Impact of cropping intensity on soil nitrogen and phosphorus for sustainable agricultural management

Sustainable agriculture plays a critical role in maintaining environmental health and also promotes long-term food security and the preservation of natural resources. We therefore, examined the response of intensified cropping systems over four years across five diverse cropland ecosystems viz. Basmati rice-Wheat-Cowpea, Basmati Rice-Potato-Wheat-Mixed Fodder (Maize + Cowpea + Charni), Basmati Rice-KnolKhol-Potato-Greengram, Basmati Rice-Radish-Green onion-French bean vegetable-Okra, and Rice-Fenugreek-KnolKhol-Green Onion-Dry Onion-Black gram to assess the changes in substrate availability and fertilizer application on nitrogen and phosphorus pools. Soil samples were collected from three different depths (0–5 cm, 5–15 cm, and 15–30 cm) during the kharif season. Significant results were observed in the mean values of mineralizable nitrogen, total nitrogen, ammonical nitrogen, nitrate nitrogen, and soil microbial biomass nitrogen at the 0–5 cm depth, with the highest values recorded under Rice-Fenugreek-KnolKhol-Green Onion-Dry Onion-Black gram. At the soil depth of 0–5 cm, available phosphorus and labile organic phosphorus exhibited significant differences, with the highest values observed in Basmati Rice-Potato-Wheat-Mixed Fodder. Moderately labile phosphorus reached its maximum values under T2 at both 0–5 cm, and at 5–15 cm depths. The peak values of non-labile organic phosphorus were found in T4 (Basmati Rice-Radish-Green onion-French bean vegetable-Okra) at the 0–5 cm soil depth. On a regional scale, the results suggest that more diversified cropping systems hold promise as sustainable agricultural practices that support nitrogen and phosphorus retention, contributing to overall soil sustainability.

Effects of seasonal precipitation regimes on microbial biomass and extracellular enzyme activity during shrub foliar litter decomposition in a subtropical forest

Elucidating the mechanisms underlying microbial biomass and extracellular enzyme activity responses to the seasonal precipitation regime during foliar litter decomposition is highly important for understanding the material cycle of forest ecosystems in the context of global climate change; however, the specific underlying mechanisms remain unclear. Hence, a precipitation manipulation experiment involving a control (CK) and treatments with decreased precipitation in the dry season and extremely increased precipitation in the wet season (IE) and decreased precipitation in the dry season and proportionally increased precipitation in the wet season (IP) was conducted in a subtropical evergreen broad-leaved forest in China from October 2020 to October 2021. The moisture, microbial biomass, and extracellular enzyme activities of foliar litter from two dominant shrub species, Phyllostachys violascens and Alangium chinense, were measured at six stages during the dry and wet seasons. The results showed that (1) both IE and IP significantly decreased the microbial biomass carbon and microbial biomass nitrogen content and the activities of β-1,4-glucosidase, β-1,4-N-acetylglucosaminidase, acid phosphatase and cellulase in the dry season, while the opposite effects were observed in the wet season. (2) Compared with those of IE, the effects of IP on foliar litter microbial biomass and extracellular enzyme activity were more significant. (3) The results from the partial least squares model indicated that extracellular enzyme activity during foliar litter decomposition was strongly controlled by the foliar litter water content, microbial biomass nitrogen, the ratio of total carbon to total phosphorus, foliar litter total carbon, and foliar litter total nitrogen. These results provide an important theoretical basis for elucidating the microbial mechanisms driving litter decomposition in a subtropical forest under global climate change scenarios.

Variations in soil enzyme stoichiometry and microbial nutrient limitations in Camellia oleifera plantations with different ages

The alteration of stand age instigates modifications in soil properties and microbial communities. Understanding the impacts of stand age on soil enzyme stoichiometry and microbial nutrient limitations in Camellia oleifera plantation is crucial for nutrient management. Taking C. oleifera plantation across four age groups (<10 a, 15-25 a, 30-50 a, >60 a) in a subtropical red soil region as test objects, we examined the response of soil enzyme stoichiometry and microbial nutrient limitations to change in stand age and analyzed the pathways for such responses. The results showed that, compared to that of stand age <10 a, enzyme C:N in the 15-25 a was increased and enzyme N:P was significantly reduced. Microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial biomass phosphorus (MBP) exhibited a trend of initially decreasing and then increasing with stand age. MBN and MBN:MBP were significantly higher in the <10 a compared to that in the 30-50 a. MBC:MBN was significantly higher in the 30-50 a and >60 a compared to the <10 a and 15-25 a. Results of redundancy analysis revealed that soil nutrients, microbial biomass and their stoichiometry explained 92.4% of the variations in enzyme stoichiometry. Partial least squares path modeling (PLS-PM) results demonstrated that soil organic carbon (SOC) had a positive effect on microbial C limitation; MBN, MBN:MBP, MBC:MBP, SOC, and total nitrogen had a nega-tive overall effect on microbial P limitation, whereas soil C:N had a positive overall effect on microbial P limitation. There was a significant positive correlation between microbial C and P limitations. With increasing stand age, microbial nutrient limitation shifted from N and P limitation (<10 a) to C and P limitation (15-25 a, 30-50 a, >60 a).

Soil Ecological Stoichiometric Characteristics and Influencing Factors of Degraded Alpine Grassland in Northwest Sichuan

Alpine grasslands are important ecosystems providing a variety of ecosystem services. However, alpine grassland degradation poses significant threats impacting soil health, stabilization and soil ecosystem function. This study aims to investigate the soil ecological stoichiometric characteristics and influencing factors in alpine grasslands, to find the primary contributing factors in soil degradation process. Soil samples were collected from alpine grassland areas with varying degrees of degradation, including non-, lightly, moderately and severely degraded (ND, LD, MD, SD). Soil characteristics including soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), available phosphorus (AP), available nitrogen (AN), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) were measured. The results revealed that soil TN, N:P ratios and C:P ratios were below the average level of China’s soil, while C:N ratio were above the average. With increasing aggravation of grassland degradation, SOC, TP, AN, MBN and MBC significantly decreased. Correlation were observed between SOC and C:N ratios as well as C:P ratios in alpine grassland with different degradation degrees (P &lt; 0.05). The C:N ratios in degraded grasslands were lower than those in ND grasslands but higher than the average level of China’s soil. Additionally, the N:P and C:P ratios of LD and MD were significantly higher than those of ND, but lower than the China’s soil average level. In conclusion, soil degradation in alpine grasslands is associated with lower TN contents, higher C:N ratios, and lower N:P ratios, which can impact soil organic matter decomposition and act as plant growth restriction factor. This study provides comprehensive insights into the ecological stoichiometry of alpine grasslands, understanding these factors is essential for the sustainable management of alpine grasslands and restoration strategies for the ecosystem services.

Short-term service crops affect the spatial organization of soil aggregates, microbial C[sbnd]N biomass, and microbial activities in a degraded monoculture system

Service crops are grown to provide ecosystem services, such as the ability to increase soil organic matter and fertility. Also, they reduce erosion processes, weed control, disease regulation, water purification, soil biodiversity, and physical restoration. The physical arrangement of elemental particles in soil aggregates controls many ecosystem functions such as soil stability and carbon sequestration. This study aimed to analyze the short-term effect of including different service crops on the soil aggregate dynamics in a degraded common bean monoculture system and how it influences the rhizospheric microbial activity, carbon, and nitrogen microbial biomass. Here, we measured soil water-stable aggregates, particulate and associated organic carbon, soil microbial biomass, microbial activity, service crop aerial biomass, and cash crop yield in bulk soils during the 2020/2021 and 2021/2022 agricultural cycles. Soil samples from depths of 0–10 cm from five management treatments (annual service crop/common bean) were analyzed under no-tillage: 1) Oat (O) = Avena sativa/common bean; 2) Wheat (W) = Triticale/common bean; 3) Vetch (V) = Vicia villosa/common bean; 4) Melilotus (Me) = Melilotus alba/common bean; 5) common bean monoculture (M) = common bean without service crop. Additionally, two controls were analyzed: 6) Brachiaria perennial (BP) = Brachiaria brizantha perennial; 7) Native vegetation (NV). Service crops significantly increased aggregate stability, mean weight diameter, particulate matter and associated organic carbon, promoting the formation of large macroaggregates (0.25–2 mm and > 2 mm). This led to an increase in carbon stocks. Microbial activity expressed as hydrolysis of fluorescein diacetate and acid phosphatase activity, increased in the largest fraction for all service crops. Vicia improved surface residues; on average all service crops increased the common bean yield by 107.25 %. In summary, Vicia represents the best alternative as a service crop to improve the quality and health of degraded monoculture soils.

Effect of foraging tunnels created by small subterranean mammals on soil microbial biomass carbon and organic carbon storage in alpine grasslands

Extensive foraging tunnel disturbances created by small subterranean mammals have important impacts on soil physical properties and nutrients in grasslands. This study took plateau zokor (Eospalax baileyi) as an example mammal to investigate the impacts of foraging tunnel disturbances by small subterranean mammals on soil microbial biomass carbon (SMBC) and soil organic carbon (SOC) storage. A paired design was used to locate 90 tunnel quadrats and 90 non-tunnel quadrats in alpine grasslands across three sites. This study showed that SMBC, SOC concentrations and SOC storage in tunnel quadrats were 47.4 %, 26.8 % and 22.0 % lower than those in non-tunnel quadrats, respectively. This study also showed that soil microbial biomass nitrogen was a major factor affecting SOC storage in non-tunnel quadrats, while it was not a major factor in tunnel quadrats. Soil pH and soil ammonium nitrogen were not major factors in non-tunnel quadrats, while they were the major factors influencing SOC storage in tunnel quadrats. In contrast to non-tunnel quadrats, foraging tunnel disturbances led to a new pathway in which soil pH positively affected SOC storage in tunnel quadrats. The findings of this study demonstrated that foraging tunnel disturbances had negative impacts on soil fertility due to lower SMBC concentrations and might cause soil carbon loss in alpine grasslands because of lower SOC storage. Given the effect of foraging tunnels on soil carbon cycling and climate regulation in the Qinghai-Tibet Plateau's alpine grasslands, it is crucial to take them into account when assessing grassland carbon storage and formulating strategies for effective grassland management and conservation.

Straw return with fertilizer improves soil CO2 emissions by mitigating microbial nitrogen limitation during the winter wheat season

Straw return is the key measure of green agricultural production. Nitrogen (N) and phosphorus (P) play pivotal roles in crop growth and carbon (C) cycling in agroecosystems. However, the mechanism of soil CO2 emissions and enzyme stoichiometry regulation by straw return with N and P application remain unknown. Therefore, this study is aimed to use enzyme stoichiometry to investigate the effects of straw return with N and P fertilizer application on soil CO2 emissions, enzyme activity, and microbial nutrient limitation through a two-year field experiment. A split-plot experimental design was used (straw as the main plot and fertilizer as the sub plot). The results indicated that the addition of N, P (SNP) increased CO2 emissions by 25.54 %, and N application (SN) reduced CO2 emissions by 27.01 %, compared with straw return (SW). Enzyme stoichiometry indicated that straw return with N and P application exhibited significant C and N limitations. In soil nutrients and nutrient stoichiometry, compared with the S0W treatment, straw return with fertilizer (SNP, SN) significantly increased microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON); SNP treatment increased β-1,4- n −acetylaminoglucosidase (NAG) enzyme activity by 53.72 %, increased l −leucine aminopeptidase (LAP) enzyme activity by 58.11 %, and increased one P-acquiring enzyme alkaline monoalkaline phosphatase (AKP) enzyme activity by 39.49 % (P < 0.05). Structural equation modeling suggested that straw return and fertilization can influence microbial biomass phosphorus (MBP) and vector length (VL) by affecting MBN, which, in turn, affects CO2 emissions. Soil microbes regulate CO2 emissions using stoichiometric flexibility to maintain a stoichiometric balance of nutrients and microbes. Therefore, straw return with N and P fertilizers to winter wheat soils can meet the requirements of microbial stoichiometry, modulate microbial and extracellular enzyme activities, and effectively regulate CO2 emissions and resource limitations.

Meta-analysis of plant restoration impacts on soil microbial community structure in mining areas

Mining causes severe damage to soil ecosystems. Vegetation restoration in abandoned mine areas is an inevitable requirement for sustainable development. Soil microbes, as the most active component of soil organic matter, play a crucial role in the transformation of carbon, nitrogen, phosphorus, and other elements. They are often used as indicators to assess the extent of vegetation restoration in ecologically fragile areas. However, the impacts of vegetation restoration on soil microbial community structure in mining areas at the global scale remains largely unknown. Based on 310 paired observations from 44 papers, we employed the meta-analysis approach to examine the influence of vegetation restoration on soil microbial abundance and biomass in mining area. The results indicated that vegetation restoration significantly promotes soil microbial biomass in mining areas. In comparison to bare soil, vegetation restoration leads to a significant 95.1% increase in soil microbial biomass carbon and a 87.8% increase in soil microbial biomass nitrogen. The abundance of soil bacteria, fungi, and actinomycetes are significantly increased by 1005.4%, 472.4%, and 177.7%, respectively. Among various vegetation restoration types, the exclusive plan-ting of trees exhibits the most pronounced promotion effect on soil microbial biomass and population, which results in a significant increase of 540.3% in soil fungi and 104.5% in actinomycetes, along with a respective enhancement of 110.3% and 106.4% in microbial biomass carbon and nitrogen. Model selection results revealed that soil satura-ted water content and vegetation restoration history contribute most significantly to the abundance of soil bacteria and fungi. Soil available nitrogen has the most significant impact on the abundance of actinomycetes and microbial biomass carbon, while soil available phosphorus emerges as a crucial factor affecting microbial biomass nitrogen. This research could contribute to understanding the relationship between vegetation restoration and the structure of soil microbial communities in mining areas, and providing scientific support for determining appropriate vegetation restoration types in mining areas.

Soil erosion alters the composition of soil nitrogen and induces nitrogen immobilization along a sloping agricultural landscape

AbstractSoil erosion transports and redistributes sediment across the landscape, altering soil organic carbon (SOC) and nitrogen (N) availability and stocks. However, the effect of erosion on soil N remains largely unclear. In this study, SOC, soil total N (TN), mineral N ( and ), dissolved organic N (DON) and total dissolved N (TDN) were evaluated in 100‐cm soil profiles in different sites (including the non‐erosion flat site, erosional site and depositional site) to examine the responses of the concentration and composition of soil N to different erosional intensity. Additionally, N mineralization and microbial biomass nitrogen (MBN) were determined to evaluate the bioavailability of soil N. Our results showed that erosion depleted TN in the erosional sites while enriching it in the depositional site throughout the soil profile. The erosion, rather than the deposition, altered the composition of dissolved N, with TDN (DON and mineral N) dominating deeper soil profiles (40–100 cm, accounting for 18%–50% of TN). The wide soil C:N ratio in the erosional site altered microbial metabolism to mine N to maintain their growth rather than mineralizing organic matter into soil bioavailable forms. This was supported by the net N mineralization (Nm), which exhibited a significant negative correlation with MBN and soil C:N ratio. The imbalanced loss of SOC and TN caused by the erosion induces soil N limitations. Collectively, our results suggested that erosion decreased TN concentrations and altered the composition of dissolved N, inducing N immobilization and decreasing soil bioavailable N.

Differential responses of photosynthesis, yield and soil properties 4 years after a single application of zeolites and biochar in a rainfed olive orchard

AbstractOlive orchards represent a key agricultural system in the Mediterranean Basin. Soil degradation processes associated with unsustainable agronomic practices and climate change could severely impact the sustainability of Mediterranean rainfed olive orchards. In this context, soil amendments are important tools that can be used to enhance soil fertility for sustained environmental quality and plant performance. In this study, a field trial was conducted for 4 years in olive tree (Olea europaea L.) to assess the effects of a mineral fertilizer compound and the combination with a single application of zeolites or biochar on the physiological and biochemical performance, tree nutritional status, crop yield and soil chemical and biological properties to gain knowledge towards more sustainable management. Our results showed that the addition of zeolites and biochar to mineral fertilizer ameliorated the physiological and biochemical performance, as evidenced by consistent increments of relative water content, stomatal conductance and net photosynthesis and by lower signs of oxidative stress during the periods of greater climate adversity. However, crop yield was not significantly different among soil treatments. On the other hand, soil chemical and biological traits at the surface layer (0–10 cm) have shown different and relevant responses after 4 years of soil amendment application. In fact, zeolite supply stood out as increased pH, extractable K, cation exchange capacity, microbial biomass carbon and microbial biomass quotient and reduced extractable Cu. Furthermore, zeolites induced positive changes in soil enzymatic activity, leading to increases in 10 enzymes involved in C, N and P cycles. In contrast, the effects of biochar on soil properties were much more reduced, given that it decreased the microbial biomass nitrogen and enhanced the activities of three P‐cycle enzymes. In summary, our data demonstrated that both soil amendments can be an interesting complement to mineral fertilization, in order to increase trees' resilience under rainfed conditions and to promote soil health, although the use of zeolites appears to be a more promising strategy because of the induction of higher soil sustainability.

Influence of New Generation Herbicide on Microbial Biomass Dynamics in Sandy Loam Soil

A laboratory experiment was conducted with two new generation herbicide pyrazosulfuron ethyl treatments, namely, recommended dose 15 g a.i. ha-1 (RD) and 30 g a.i. h-1 (2RD), carfentrazone ethyl 25 g a.i ha-1(RD), 50 g a.i. ha-1 (2RD) along with control (without herbicide) applied to sandy loam soil to determine their effect on microbial biomass dynamics in soil. The application of pyrazosulfuron ethyl (T1 and T2) and carfentrazone ethyl (T3 and T4) did not show any significant effect at 0 day after application. While, at 7 days after application of herbicide declined soil microbial biomass status. Whereas, at 28 days after application significantly increasement microbial biomass carbon and microbial biomass nitrogen except for microbial biomass phosphorus under herbicidal treatments compared to untreated plot. Hence, pyrazosulfuron and carfentrazone ethyl may cause short term transitory change in microbial biomass dynamics in soil moreover at 28 day after application of herbicide no any harmful effect at recommended dose of pyrazosulfuron ethyl and carfentrazone ethyl.

Functional roles of biocrusts in enhancing soil quality in a semi-arid environment

Biocrusts play a wide range of ecological roles, especially in modifying surface soil properties and as a natural agent to combat soil degradation in fragile semi-arid and arid ecosystems globally. We examined the importance of biocrust on soil properties and quality in a semi-arid alluvial fan in northeastern Iran. The soil quality index (SQI) was used as the method for the quantitative evaluation of soil with or without biocrusts, using standard linear and nonlinear scoring methods. For this purpose, 17 biological, chemical, and physical soil properties were integrated into two indicator selection methods (total and minimum data set) and SQI has been calculated by the weighted additive method. The spatial patterns of SQI showed that overall the soil quality was (47%) increased in biocrust compared to non-biocrust soil. The increase of microbial biomass nitrogen, basal soil respiration, and microbial biomass carbon, and the decrease of available sodium and percentage sand were the most important indicators controlling the soil quality changes by biocrusts. In addition, biocrusts improved the soil structure by reducing bulk density and increasing the mean weight diameter of aggregates and available water capacity. Cyanobacteria communities of biocrusts were the initiators of soil quality improvement, while moss and cyanolichen communities played a major role from the moderate stages of biocrust occurrence. It is concluded that globally, in dry lands, biocrusts should be considered as signatures of enhanced soil quality.

Effects of water stress on nutrients and enzyme activity in rhizosphere soils of greenhouse grape.

In grape cultivation, incorrect water regulation will lead to significant water wastage, which in turn will change soil structure and disrupt soil nutrient cycling processes. This study aimed to investigate the effects of different water regulation treatments [by setting moderate water stress (W1), mild water stress (W2), and adequate water availability (CK)] on soil physical-chemical properties and enzyme activity in greenhouse grape during the growing season. The result showed that the W2 treatment had a negative impact on the build-up of dissolved organic carbon (DOC), nitrate nitrogen (NO3-N), and available phosphorus (AP). Throughout the reproductive period, the W1 and W2 treatments decreased the soil's microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) contents, and MBC was more vulnerable to water stress. During the growth period, the trends of urease, catalase, and sucrase activities in different soil depth were ranked as 10-20 cm > 0-10 cm > 20-40 cm. The urease activity in 0-10 cm soil was suppressed by both W1 and W2 treatments, while the invertase activity in various soil layers under W1 treatment differed substantially. The W1 treatment also reduced the catalase activity in the 20-40 cm soil layer in the grape growth season. These findings suggested that W2 treatment can conserve water and enhance microbial ecology of greenhouse grape soils. Therefore, W2 treatment was the most effective water regulation measure for local greenhouse grape cultivation.