Soil Basal Respiration Research Articles

Utility of wood ash, paper sludge and biochar for the mitigation of greenhouse gases emissions from acid boreal soils

Land-use change in the boreal forest region leads to agriculture to be carried out on acid, shallow and low fertility soils. To correct soil fertility and promote crop productivity, manure and inorganic fertilizers are added, increasing the risk for greenhouse gas emissions (GHGE). To reduce the reliance on synthetic soil amendments while taking advantage of locally relevant industrial by-products, wood ash (WA) and paper sludge (SL) have been proposed as soil amendments for a range of soil types. We posited that amending soils with WA, SL and biochar will improve soil health parameters and fertility of boreal soils. Microbial activity resulting to nitrogen losses and availability were assessed. WA had a stronger ameliorative effect on acid boreal soils compared to SL. Both WA and SL increased soil microbial biomass and basal respiration resulting in higher net mineralization and thus significant increases in CO2 emissions. Co-application of urea with WA or SL further increased net mineralization compared to when used independently. Conversely, the biochar's effect was short-lived and not significant. Nevertheless, addition of biochar was shown to reduce CO2 emissions in all cases except in WA amended soils. No significant differences were observed in CH4 emissions across all treatments. WA and SL may improve soil fertility and quality but could also contribute significantly to GHG emissions in acid boreal soils. Further research is recommended to assess the mitigating effect of various biochar feedstocks on GHG emissions when co-applied with WA and SL.

Under-vine cover crops: Impact on physical and biological soil proprieties in an irrigated Mediterranean vineyard

Despite their potential benefits, cover crops in vineyards under to Mediterranean climate conditions are still not widespread, especially in the vine row. This under-vine space is normally kept weed-free through the application of herbicides and/or tillage. In this work, we evaluate the effect of a Trifolium fragiferum L. under-vine cover crop (UV) on soil quality, as reflected by a variety of physical, chemical, and biological soil indicators. 15 months after under-vine cover crop implementation, total (SOC) and particulate (POC) organic carbon storage, and soil aggregation (abundance (WSA) and mean weight diameter (MWD) of water stable aggregates) were compared with a control without cover (T) at 0–15 cm. In addition, for three consecutive years after under-vine cover crop implementation, the evolution of soil microbial communities was monitored through the determination of soil basal respiration, soil microbial biomass carbon and nitrogen (MBC and MBN), and community-level physiological profiles (CLPPs). The establishment of the under-vine cover crop resulted in higher values of SOC (27.78 Mg·ha−1 in UV vs. 20.71 Mg·ha−1 in T, +33%) and POC (4.75 Mg·ha−1 in UV vs. 2.73 Mg·ha−1 in T, +74%), as well as aggregation parameters (MWD: 1.82 µm in UV vs. 1.56 µm in T, +17% and WSA: 84.68% in UV vs. 71.58% in T, +18%). An evolution towards progressively greater values of biological activity (basal respiration) and microbial biomass was detected in under-vine cover crop soils as time elapsed. It was concluded that the Trifolium fragiferum L. under-vine cover crop led to soil quality improvement in our Mediterranean climate vineyard. Interestingly, this positive effect was noticed shortly after its implementation.

The effect of plant mycotrophy and soil disturbance on soil microbial activity

AbstractIn cropping systems, the choices adopted for the tillage system used and plants cultivated can strongly influence the soil microbial population and its functional profile. Arbuscular mycorrhizal fungi are an important component of soil microbiome and their mutualistic symbiosis with the majority of higher plants grant the latter a wide range of benefits. The extraradical mycelium developed by these fungi expands the volume of soil influenced and harbours a diversity of microbes establishing a distinct environment of complementary interactions. We assessed how growing plants with different levels of mycotrophy modifies the biological activity profile in the soil under Mn toxicity and whether this is modified by soil disturbance. Following mycotrophic plants, soil contained a more active microbiome than after the non‐mycotrophic plants, as expressed by higher values of soil basal respiration or dehydrogenase activity. Additionally, the count of phosphorus solubilizes and activity of phosphatase were greater after mycotrophic plants. Even among mycotrophic plants, different profiles of biological activity can be distinguished after growing a legume or grass. ERM disruption by soil disturbance decreased most of the parameters studied and for phosphatase activity and P solubilizers in a more significant way. These results indicate that even under Mn toxicity, the microbiome associated with AMF symbiosis following mycotrophic plants growth presented a higher biological activity and had a differential biological response towards the stress imposed by soil disturbance, when compared with the microbiome associated with non‐mycotrophic roots.

Effects of applying peanut shell and its biochar on the microbial activity and community structure of dryland red soil

Due to its soil formation process, dryland red soil has certain characteristics that are unfavorable for crop growth, including acidity, fineness, plate structures, and erosivity. The use of large amounts of fertilizer can decrease fertility and biodiversity and increase acidification, thereby seriously restricting the sustainable utilization of dryland red soil resources. Therefore, there is an urgent need for techniques that improve the crop quality and yield in dryland red soil areas. Returning crop waste to fields as fertilizer is a promising approach to sustainable agriculture. In the present study, the effects of applying peanut shell and an associated biochar product to dryland red soil were investigated, with a focus on soil microbial activity and community structure. Field experiments were conducted in Jiangxi Province, southern China, in 2020, in field plots of sweet potato crops. Seven treatments were set up according to the principle of equal carbon return to farmland: Control: (conventional fertilization); S1, S2, S3 (peanut shell application of 3000, 4500 and 6000 kg hm-2, respectively); and BC1, BC2, BC3 (peanut shell biochar application of 1000, 1500 and 2000 kg hm-2, respectively). The application of peanut shell and its biochar improved soil basal respiration, with the greatest increase relative to controls of 161.06% found in treatment S3 at the root harvest stage. The most obvious increase in microbial biomass carbon content due to biochar application was 206.50% in treatment BC2 at the root harvest stage. The application of peanut shell and its biochar increased the phospholipid fatty acid (PLFA) contents of total soil microorganisms and different microbial groups. The maximum increases in the PLFA contents of total soil microorganisms, gram-positive bacteria, and gram-negative bacteria occurred at the early root formation stage in treatment BC2, which were 112.16%, 102.52%, and 115.64%, respectively. Both peanut shell and biochar increased the PLFA contents of soil actinomycetes, arbuscular mycorrhizal fungi (AMF), and other fungi to certain extents. The soil actinomycetes PLFAs increased by 120.08% at the early root formation stage in BC2, while the AMF PLFAs increased by 79.44% at the seedling stage in S2. This study provides theoretical and practical guidance for the comprehensive utilization of peanut shell and the implementation of circular agriculture in dryland red soil regions. It also provides a scientific basis for improving the fertility of dryland red soil.

Evaluating Different Soil Amendments as Bioremediation Strategy for Wetland Soil Contaminated by Crude Oil

This study evaluated the efficacy of using Tween 80 surfactant (TW80) and food-waste anaerobic digestate fibre (FWAD) as soil amendments for the remediation of wetlands contaminated by crude oil. A 112-day mesocosms experiment was carried out to simulate hydrocarbon degradation under typical acidified wetland conditions. Soil was spiked with 50,000 mg kg−1 crude oil and TW80 and FWAD were added to mesocosms at 10%, 20% and 30% w/w. The soil basal respiration, microbial community dynamics, environmental stress, alkanes, and PAHs degradation were monitored throughout the mesocosm experiment. Amending the mesocosms with FWAD and TW80 enabled the recovery of the soil microbial activities. This was evidenced by soil basal respiration which was the highest in the 30% FWAD and 30% TW80 mesocosms and translated into increased degradation rate of 32% and 23% for alkanes, and 33% and 26% for PAHs compared to natural attenuation, respectively. Efficient total hydrocarbon degradation was achieved in soil mesocosms with 30% FWAD and 30% TW80 at 90% and 86.8%, respectively after 49 days. Maize seed germination results showed significant improvement from 29% to over 90% following the FWAD and TW80 treatment.

Interactions between soil organic matter chemical structure and microbial communities determine the spatial variation of soil basal respiration in boreal forests

Interactions between soil organic matter (SOM) composition and microbial communities determine soil basal respiration (BR, SOM-derived CO2). However, few studies have investigated the relative importance of SOM chemical structure, microbial community composition, and soil environmental factors to the spatial variability of soil BR on a large scale. Here, organic and mineral layer soils were collected along a 650-km boreal forest transect in Northeast China. Combining 13C-nuclear magnetic resonance spectroscopy and high-throughput sequencing techniques, SOM chemical structure, microbial community composition, and soil physicochemical properties were determined to investigate the biotic and abiotic drivers of soil BR. Soil BR, microbial communities, and soil physicochemical properties exhibited significant spatial heterogeneity across sites, but the variations were independent of latitude regardless of soil layer. Soil BR rates were significantly higher in the organic layer than in the mineral layer (0.82 vs. 0.31 CO2-C kg−1soil−1 h−1, P < 0.001). Multi-model averaging and partial regression showed that SOM chemical structure exhibited the strongest control on the spatial variation of soil BR (contributing 23.0 %), followed by the organic layer soil C/N ratio (contributing 17 %). However, only soil C/N ratio was the most important predictor of soil BR variation in the mineral layer. Copiotrophic bacteria had a higher impact on soil BR than oligotrophic bacteria. In addition, soil physicochemical properties (i.e. pH, mechanical composition) indirectly affected soil BR through regulating soil microbial composition, especially bacteria. Overall, these results highlighted that SOM chemical structure directly or indirectly affected the microbial decomposition of SOM, and contributed more relative to SOM quality. These findings should be incorporated into ecosystem process models to better predict the response of boreal forest soil C emissions to climate change.

Changes in Wheat Rhizosphere Carbon Pools in Response to Nitrogen and Straw Incorporation

Large-scale burning of rice straw causes air pollution and deterioration of soil health, which challenges the sustainability of the rice–wheat system (RWS) in north-western India. In a field experiment on sandy loam (Typic Ustochrept) soil at Punjab Agricultural University, India, with split plot design, effects of four nitrogen (N) levels (0, 90, 120, and 150 kg N ha−1) in main plots and four levels of rice straw (RS) incorporation (0, 5, 7.5, and 10 Mg ha−1) in wheat in sub-plots were studied after 7 years on carbon (C) pools at maximum tillering (MT) and flowering (FL) stages of wheat and crop yields. Rice straw (RS) incorporation at 10 Mg ha−1 with N application at 120 kg N ha−1 in wheat not only increased labile C pools significantly especially at MT but also increased the wheat yield compared with no straw incorporation. Principal component analysis suggests that total polysaccharide carbon, basal soil respiration, and pH can be used as sensitive parameters for assessing soil quality in RWS.

Ecotoxicity of parathion during its dissipation mirrored by soil enzyme activity, microbial biomass and basal respiration

The application of parathion (PTH) in agriculture can result in its entry into the soil and threaten the soil environment. Monitoring the PTH residues and assessing toxicity on soil health are of paramount importance to the public. Herein, the dissipation of PTH and concomitant influence on microbial activities [FDA hydrolase (FDA‒H), microbial biomass carbon (MBC) and basal respiration (BR)] in coastal solonchaks were investigated. Results showed that the dissipation of PTH in tested soil declined linearly, and the half-lives varied from 5.6 to 56.8 days, depending on pollutant concentrations. The FDA‒H activity and MBC were negatively affected by PTH pollution and exhibited a significantly positive correlation. Two‒way ANOVA analysis demonstrated that microbial activities were affected not only by PTH dose and incubation time but also by their interactions. The integrated biomarker response (IBR/n) index values on day 120 were between 1.02 and 2.89, larger than those on day 1 during PTH dissipation. This implied that the soil quality did not recover though there was no PTH residue in the soil at the end of the experiment. These findings suggested that microbial activities integrated with IBR/n index could elucidate the hazardous impacts of PTH dissipation on biochemical cycling and microorganisms in soil.

Essential oil chemotypes of turmeric (Curcuma longa L.) cultivated in four different farmers in Southwest of Paraná State - Brazil

Turmeric (Curcuma longa L.) has economic value for its medicinal and nutritional properties. This study aimed to evaluate the yield and phytochemical profile of essential oil (EO) from turmeric rhizomes produced by family farmers in rural communities in Francisco Beltrão – PR, and soil microbiological quality from those farmers. Four turmeric farmers from the communities of São Braz, Rio Tuna, Rio Saudade and Nova Sessão were selected. Soil samples and rhizomes of turmeric were collected and subsequently evaluated for soil microbial biomass carbon, soil basal respiration and soil metabolic quotient and EO yield of rhizomes by hydrodistillation. After, EO yield (%) was calculated and the chemical identification by GC/MS. The Nova Sessão community had better soil microbiological quality, whereas the EO yield (3.02%) was higher for the Rio Tuna community. The four rural communities showed good results for the EO yield (ranging from 1.68 to 3.02% and compared to the literature, which ranged from 0.2 to 5.27%), with the São Braz community, showing a significant reduction and the Rio Tuna community had the highest EO yield. Also was observed variation in the major EO chemical compounds, e.g.: ar-turmerone (44.27 to 64.21%), curlone (12.27 to 20.83%), α-zingiberene (1.30 to 15.97%) and β-sesquiphellandrene (1.24 to 10.07%). It is concluded that among the four communities studied, there was significant variation in the EO yield and differences in EO quality of turmeric, especially in the major components ar-turmerone and α-zingiberene.

Bacillus velezensis Associated with Organomineral Fertilizer and Reduced Phosphate Doses Improves Soil Microbial—Chemical Properties and Biomass of Sugarcane

Appropriately using phosphorus (P) for the fertilization of sugarcane is critical to achieving high productivity because it is one of the most limiting nutrients in agricultural cropping systems. Thus, the objective of this research was to evaluate the morphological, biochemical, and yield responses of sugarcane, and the soil microbial–chemical properties, under the use of organomineral fertilizer (OF) associated or not with Bacillus velezensis strain UFV 3918 (B) combined with mono ammonium phosphate (MAP) doses. The experimental design used was completely randomized, consisting of eight treatments [Control (3/3 MAP); OF (without MAP); OF + 1/3 MAP; OF + 2/3 MAP; OF + 3/3 MAP; B + OF + 1/3 MAP; B + OF + 2/3 MAP; B + OF + 3/3 MAP] and four replicates. B + OF + 1/3 MAP provided increases in accumulated soil basal respiration (11.9%), carbon of microbial biomass (35.9%), fluorescein diacetate (12.7%), arylsulfatase (25.5%), and acid phosphatase (10.1%) activity compared to the control, which implied in higher shoot and total biomass. These results present a potential strategy for sugarcane fertilization, using bacteria in combination with OF to improve P nutrition and growth in sugarcane with reduced economic and environmental impact.

Changes in soil microbial metabolic activity following long‐term forest succession on the central Loess Plateau, China

AbstractForest succession can alter terrestrial ecosystem processes and potentially impact subsurface carbon dynamics. However, the effects of long‐term forest succession on soil microbial metabolic activity remain unclear. This study investigated a long‐term forest succession approximately ~160 years after farmland abandonment on the central Loess Plateau, China, to explore the changes in soil microbial metabolism following the forest succession. Among them, the soil basal respiration (BR), microbial quotient (qMB), and metabolic quotient (qCO2) were studied. The results showed that the BR and qCO2 were increased following forest succession, whereas the qMB showed the opposite trend. Forest succession also increased the activities of β‐1,4‐glucosidase (BG) and β‐D‐cellobiosidase (CBH). The increase of BR and qCO2 and the decrease of qMB occurred in the early stage (&lt;60 years). However, the increase of BG and CBH mainly occurred in the later period (&gt;100 years). Soil microbial metabolic activity was closely related to litter biomass, dissolved organic carbon, fungal, and bacterial community composition. In conclusion, long‐term forest succession changes soil microbial community structure and promotes soil organic carbon accumulation, while the increase of soil respiration and metabolism promotes the release of carbon element following forest succession, thus reducing soil microbial carbon utilization efficiency.

Tree species is more effective than season dynamics on topsoil function andCO2emissions in the temperate forests

AbstractSoil respiration is one of the most important operations controlling carbon (C) erosion from territorial ecosystems and a useful index of whole underground allocation of C and stand efficiency. However, how tree species effects root (i.e., autotrophic respiration) and soil microbial respiration (i.e., heterotrophic respiration), based on precise experiential schemes, are still restricted, even though crucial to guide the selection of species for reforestation and C management purposes. This research was done to study how tree species effect soil characteristics and function at stand level and which are the main drivers of soil CO2emission in mixed temperate forests in northern Iran (Mazandaran province). Four most common tree species at the experimental site (Parrotia persica,Ulmus minor,Quercus castaneifolia, andPopulus caspica) that surrounded by same species, were selected. Around each selected tree, four replicates of soil and litter samples were taken from (30 × 30 × 15 cm) and mixed to characterize soil physicochemical characteristics (i.e., bulk density, texture, water content, pH, electrical conductivity, N, organic carbon, and available P, K, Mg, and Ca), basal respiration and substrate (i.e., D‐manitol, D‐glucose, L‐asparagine, L‐arginine, gluconic acid, quinic acid, succinic acid, malonic acid, D‐glucosamine, L‐glutamine) induced respiration. In the litter characteristics, total N, C (OC), and C/N ratio were measured. Our results confirmed that soil chemical properties are more sensitive to species composition than soil physical ones. Moreover, individual tree species in mixed deciduous forests strongly influence induced microbial respiration, independently of the used substrates. On the contrary, season was the major factor explaining variations of basal respiration.

Short-term effects of post-fire soil mulching with wheat straw and wood chips on the enzymatic activities in a Mediterranean pine forest

Soils of Mediterranean forests can be severely degraded due to wildfire. However, post-fire management techniques, such as soil mulching with vegetal residues, can limit degradation and increase functionality of burned soils. The effects of post-fire mulching on soil functionality have been little studied in Mediterranean forests, and it is still unclear whether the application of straw or wood residues is beneficial. This study explores the changes in important soil chemical and biochemical properties in a pine forest of Central Eastern Spain after a wildfire and post-fire mulching with straw or wood chips. Only basal soil respiration (BSR), dehydrogenase activity (DHA), pH and water field capacity (WFC) significantly changed after the fire and mulching. In contrast, the other enzymatic activities - urease (UA), alkaline phosphatase (Alk-PA) and β-glucosidase (BGA), − total organic carbon (TOC) and electrical conductivity (EC) were not influenced by these soil disturbances. Time from fire and soil conditions (due to burning and management) were significant variability factors for BSR, pH, BGA, UA, TOC, EC. Mulching increased BSR compared to burned areas, especially in soils with straw (+30 %), thanks to addition of fresh organic residues, quickly incorporated in the soil. Soil pH showed a low variability among the four soil conditions, and TOC was higher in mulched soils (on average + 20 % compared to the burned soils), and this was correlated to the increased BSR. The role of mulching was essential with reference to WFC, as the post-fire management limited its reduction after the fire (on average from −30 % to −20 %). Finally, the Principal Component Analysis coupled to the Analytical Hierarchical Cluster Analysis confirmed the significant influence of the post-fire management on some enzymatic activities, although a sharp discrimination among the four soil conditions was only evident between unburned and burned sites, regardless of the management. Overall, it has been shown that mulching promotes conservation of fragile Mediterranean soils, indicating its effectiveness at preserving soil functionality in areas affected by forest fires.

Biogeochemical appraisal of carbon fractions and carbon stock in riparian soils of the Ganga River basin

The farmers are approaching river/reservoir beds to produce crops and vegetables during the lean periods, especially post-monsoon, winter, and summer, for their livelihood in changing climatic scenarios. Comparing C fractions, C stocks, and microbial indices between the terrestrial (conventional agricultural land: CAL) and riparian zones (reservoir riparian zones: RSRZ and river riparian zones: RRZ) reveals that cultivating riparian zones is environmentally stressful and climatically vulnerable to livelihood practices. The moist riverbed conditions for cultivation result in the accumulation of residual biomass and the burial of soil organic matter. The C fractions showed decreasing trends as CAL > RSRZ > RRZ. The mean TOC stock was found high in the CAL soils (45.04 Mg C ha−1) than in the RRZ (40.65 Mg C ha−1) and RSRZ soils (38.01 Mg C ha−1). The labile C fraction (KMnO4-C) varied from 2.34 to 3.29 % of TOC, and the RSRZ and RRZ soils showed 14.50 % and 40.32 % less KMnO4-C than the CAL soils. The relationship between KMnO4-C and mineralizable C (Cmin) showed high potential for organic carbon stabilization in riparian soils. The microbial biomass carbon (MBC) and basal soil respiration (BSR) values were nearly half of the CAL in the RRZ soils indicating limited carbon substrate availability to the microbial decomposition. Low mineralization quotient (qM) and high metabolic quotient (qCO2) indicated stressful microbial utilization of labile TOC in the RRZ soils. The high carbon management index (CMI) showed the potential to store and sequester TOC in riparian soils. The artificial neural networks (ANN) were used to examine the impact of soil properties on the prediction efficiency of TOC stocks in the three farming zones.

Comparison of the Responses of Soil Enzymes, Microbial Respiration and Plant Growth Characteristics under the Application of Agricultural and Food Waste-Derived Biochars

The conversion of bio-wastes to useful products such as biochar provide a suitable option not only to minimize the mass of wastes, but also to use the biochar as soil amendment. In the present study, food waste biochar (FWB) and agricultural waste derived biochar (AB), either alone or in combination (FWB + AB), were tested for their effects on soil microbiological characteristics (soil enzymes, soil basal as well as substrate-induced respiration), plant growth and photosynthetic parameters. Four treatments were tested: control, FWB, AB and FWB + AB. The results indicated that the application of AB significantly enhanced the plant above ground and below ground fresh and dry biomass as compared to other amendments and control (+41 to +205% compared to control). The application of FWB enhanced the quantum yield of photosystem II (QY-max, +4% compared to control) and normalized difference vegetation index (NDVI, +13% compared to control). Moreover, the FWB application improved the soil dehydrogenase (DHA) activity (+24% compared to control). Furthermore, the soil basal respiration was found to be increased under AB application (+46% compared to control) and the substrate-induced respirations were relatively decreased, depicting negative effects of applied biochars on substrate-induced respirations. Thus, we concluded that the differential responses of observed crop and soil attributes might be related to the biochar specific effects on soil properties.

Food and agricultural wastes-derived biochars in combination with mineral fertilizer as sustainable soil amendments to enhance soil microbiological activity, nutrient cycling and crop production

The ever-increasing human population associated with high rate of waste generation may pose serious threats to soil ecosystem. Nevertheless, conversion of agricultural and food wastes to biochar has been shown as a beneficial approach in sustainable soil management. However, our understanding on how integration of biochar obtained from different wastes and mineral fertilizers impact soil microbiological indicators is limited. Therefore, in the present study the effects of agricultural (AB) and food waste derived (FWB) biochars with and without mineral fertilizer (MF) on crop growth and soil health indicators were compared in a pot experiment. In particular, the impacts of applied amendments on soil microbiological health indicators those related to microbial extracellular (C, N and P acquiring) enzymes, soil basal as well as different substrate induced respirations along with crop’s agronomic performance were explored. The results showed that compared to the control, the amendment with AB combined with MF enhanced the crop growth as revealed by higher above and below ground biomass accumulation. Moreover, both the biochars (FWB and AB) modified soil chemical properties (pH and electric conductivity) in the presence or absence of MF as compared to control. However, with the sole application of MF was most influential strategy to improve soil basal and arginin-induced respiration as well as most of the soil extracellular enzymes, those related to C, N and P cycling. Use of FWB resulted in enhanced urease activity. This suggested the role of MF and FWB in nutrient cycling and plant nutrition. Thus, integration of biochar and mineral fertilizers is recommended as an efficient and climate smart package for sustainable soil management and crop production.

Small-Scale Variability of Soil Quality in Permafrost Peatland of the Great Hing’an Mountains, Northeast China

Permafrost peatland is a unique ecosystem that represents a huge carbon terrestrial pool. Soil quality has a relatively high level of variation at small scale in this ecosystem and is closely related to the carbon cycle. To quantify this variability, we analyzed total organic carbon, total nitrogen, total phosphorus, nutrient, and element (sodium, magnesium, potassium, and calcium), and microbial respiration activities (microbial biomass carbon, soil basal respiration, metabolic, and microbial quotients) in the humus layer to deeper soil layer of 6 plots at small scale (meters). For all samples, the coefficients of variation (CV) values of total carbon concentrations were lowest and these values of sodium, magnesium, potassium, and calcium concentrations were higher than those of total carbon, nitrogen, and phosphorus concentrations. The largest variations of total phosphorus, ash, and Na were in the 10–20 cm layer with soil depths. The litter decomposition and water table may cause this variation at small-scale. The CV values of microbial respiration activities were largest compared with soil properties. There were different correlations between basal respiration and soil properties among the plots. Our results showed that soil properties and microbial respiration activities in permafrost peatland exhibits considerable variability at small scale. This variability indicates that sampling location and number are very important in peatland studies if we want to accurately estimate the biogeochemistry in a peatland.

The Effect of Sheep Wool Fertilizer on Some Biochemical Properties of a Clay Loam Soil

ABSTRACT Soil is an essential element in sustainable agriculture. Improving soil properties and increasing soil fertility can be achieved by increasing the organic matter content of soils. Organic fertilizers are important in eliminating the negativity of the insufficiency of this component of soil. For this purpose, the study was carried out to determine the effect of manure made from sheep wool on some biochemical properties of soil with clay loam texture. Sheep wool manure (SWM) was added to the soil at rates of 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, and 5.0 t da−1. Pepper was grown and some biochemical analyses were done after the harvest. According to the results of the research, pH, salinity, organic matter content, potassium (K), sodium (Na), iron (Fe), manganese (Mn), zinc (Zn), and boron (B) concentrations of the soils increased. The contents of other elements [phosphorus (P), calcium (Ca), magnesium (Mg), copper (Cu)] did not change in the study. In addition, the effects of sheep wool manure applied in increasing doses on some biological properties of the soil [urease (UEA), dehydrogenase (DEA), acid (ACPEA) and alkaline phosphatase (ALPEA), catalase (CEA) and arylsulfatase enzyme activity (ARSEA), basal soil respiration (BSR)] were statistically significant (p < .01). As the dose of sheep wool manure increases, the aeration of the soil and the water-holding capacity increase.

Phosphate fertilization and bioactivator influences on fractions of organic matter and soil microbial biomass

Soil organic matter is considered a potential source of phosphorus (P) for plants because of biological cycling. Bioactivators are characterized as tools that can help soil microbial activity and the availability of P demanded by plants. The objective of this study was to evaluate the influence of the use of bioactivators and phosphate fertilization on the activity of soil microbial biomass and humified fractions of organic matter. The experimental design was completely randomized in a factorial scheme (6 × 2), with the first factor consisting of six doses of phosphorus applied to the soil (0, 30, 60, 90, 120, and 150 kg ha-1 of P2O5), using triple superphosphate as the source, and the second factor being the presence or absence of soil and plant bioactivator application, with four replications. The evaluated characteristics were soil microbial biomass carbon (SMBC), soil basal respiration (SBR), microbial biomass nitrogen (MBN), metabolic quotient (qCO2), microbial quotient (qmic), total organic carbon (TOC), fulvic acid fraction carbon (FAC), humic acid fraction carbon (HAC), and humin fraction carbon (HUMC). The use of soil and plant bioactivators and mineral phosphate fertilizer promoted changes in soil microbial activity. Increasing doses of phosphate fertilization promoted a reduction in the carbon characteristics of microbial biomass and basal soil respiration in the presence or absence of soil and plant bioactivators. Moreover, the use of bioactivator promoted higher averages for soil microbial biomass carbon, soil basal respiration, metabolic quotient, humic acid and humin and reduced the levels of microbial quotient, total organic carbon and fulvic acid.

Response of soil microbial activities and ammonia oxidation potential to environmental factors in a typical antimony mining area

Mining, smelting and tailing deposition activities can cause metal(loid) contamination in surrounding soils, threatening ecosystems and human health. Microbial indicators are sensitive to environmental factors and have a crucial role in soil ecological risk assessment. Xikuangshan, the largest active antimony (Sb) mine in the world, was taken as the research area. The soil properties, metal(loid) contents and microbial characteristics were investigated and their internal response relationships were explored by multivariate statistical analysis. The assessment of the single pollution index and Nemerow synthetic pollution index (PN) showed that the soils were mainly polluted by Sb, followed by Cd and As, in which sampling site S1 had a slight metal(loid) pollution and the other sampling sites suffered from severe synthetic metal(loid) pollution. The microbial characteristics were dissimilar among sampling points at different locations from the mining area according to hierarchical cluster analysis. The correlation analysis indicated that fluorescein diacetate hydrolase, acid phosphatase, soil basal respiration and microbial biomass carbon were negatively correlated with PN, indicating their sensitivity to combined metal(loid) contamination; that dehydrogenase was positively correlated with pH; and that urease, potential ammonia oxidation and abundance of ammonia-oxidizing bacteria and archaea were correlated with N (nitrogen) contents. However, β-glucosidase activity had no significant correlations with physicochemical properties and metal(loid) contents. Principal components analysis suggested bioavailable Sb and pH were the dominant factors of soil environment in Xikuangshan Sb mining area. Our results can provide a theoretical basis for ecological risk assessment of contaminated soil.