Soil Biochemical Properties Research Articles

Effects of the Severity of Wildfires on Some Physical-Chemical Soil Properties in a Humid Montane Scrublands Ecosystem in Southern Ecuador

Humid montane scrublands (HMs) represent one of the least studied ecosystems in Ecuador, which in the last decade have been seriously threatened by the increase in wildfires. Our main objective was to evaluate the effects of wildfire severity on physicochemical soil properties in the HMs of southern Ecuador. For this purpose, fire severity was measured using the Normalized Burn Ratio (NBR) and the difference between pre-fire and post-fire (NBR Pre-fire-NBR Post-fire) over three contrasted periods (years 2019, 2017, and 2015) was determined. Likewise, 72 soil samples from burned HMs and 72 soil samples from unburned HMs were collected at a depth of 0 to 10 cm, and some physical (bulk density and texture) and biochemical (pH, soil organic matter, and total nutrients) soil properties were analyzed and statistically processed by one-way ANOVA and principal component analysis (PCA). Results indicate that burned HMs showed mixed-severity burning patterns and that in the most recent wildfires that are of high severity, SOM, N, P, Cu, and Zn contents decreased drastically (PCA: component 1); in addition, there was an increase in soil compaction (PCA: component 2). However, in older wildfires, total SOM, N, P, K, and soil pH content increases with time compared even to HMs that never burned (p-value < 0.05). These results can help decision makers in the design of policies, regulations, and proposals for the environmental restoration of HMs in southern Ecuador affected by wildfires.

Calorific Value of Festuca rubra Biomass in the Phytostabilization of Soil Contaminated with Nickel, Cobalt and Cadmium Which Disrupt the Microbiological and Biochemical Properties of Soil

The choice of optimal plant species for phytoremediation and organic fertilization plays an important role in stabilizing the functions of soils contaminated with heavy metals. The influence of nickel, cobalt and cadmium on the biomass yield and calorific value of Festuca rubra, heavy metal concentrations in soil and plants and the microbiological, biochemical and physicochemical proprieties of soil were analyzed in a pot experiment. The tolerance index (TI) describing Festuca rubra’s ability to tolerate heavy metals, as well as the translocation (TF), accumulation (AF) and bioaccumulation (BF) factors of heavy metals in Festuca rubra were calculated. The experiment was conducted in two series: In soil fertilized and not fertilized with compost. Nickel and cobalt significantly inhibited the growth and development of Festuca rubra. The experiment demonstrated that this plant species can be grown on soil contaminated with heavy metals. Festuca rubra contained on average 46.05% C, 34.59% O, 5.91% H, 3.49% N, 0.19% S and 9.76% ash. Festuca rubra has a stable calorific value which is not affected by heavy metals; therefore, biomass harvested from heavy metal-polluted soil can be used for energy generation. The calorific value of Festuca rubra ranged from 15.924 to 16.790 MJ kg−1 plant d.m., and the heat of combustion from 17.696 to 18.576 MJ kg−1. It has a stable calorific value which is not affected by heavy metals, therefore biomass harvested from heavy metal-polluted soil can be used for energy generation. Festuca rubra is particularly useful for the phytostabilization of soil contaminated with cadmium and cobalt. Compost minimizes the adverse effects of heavy metal pollution on the microbiological, biochemical and physicochemical properties of soil.

Potential application of Chlorella sp. biomass cultivated in landfill leachate as agricultural fertilizer

ABSTRACT This study was to investigate the possibility of nutrient removal from landfill leachate using Chlorella sp. and its potential as agricultural fertilizer. Chlorella sp. was inoculated to a leachate suspension (1:1 ratio). Phosphate, ammonium and nitrate concentrations in the suspension and the dry cell weight of algae were measured at 0, 2, 4, 6 and 8 days of incubation. Then, the harvested microalgae biomass was mixed with a nutrient-poor soil at three levels: 0 (A0), 2 (A2) and 4 (A4) g 100 g−1. The mixtures were incubated for 2 months, and soil biochemical properties, including soil organic carbon (OC), available phosphorus (Pava), mineral nitrogen (Nmin), microbial basal respiration (MBR) and microbial biomass carbon (MBC), were determined in soil at 7, 14, 28, 35, 42, 49 and 56 days of incubation. The dry cell weight of the microalgae increased over time and removed ammonium, phosphate and nitrate from the leachate by 98.7, 92.7 and 56.9%, respectively. The added microalgae biomass to soil caused positive and significant changes in soil OC, Pava, Nmin, MBR and MBC. Therefore, it seems that Chlorella sp. cultivated in landfill leachate can be used as an agricultural fertilizer in soil.

Effects of harvest residue management on soil organic nitrogen fractions in young Cunninghamia lanceolata plantation

Different treatments of harvest residues will change the quantity and quality of soil organic matter, with direct or indirect effects on the composition and content of soil nutrient. Nitrogen is one of the most important soil nutrients. However, the response of soil organic nitrogen fractions to different harvest residue treatments is still unclear. In this study, harvest residue treatments, including harvest residue removed, residue retained and residue burnt, were set up after clear-cutting a 50-year-old mature Cunninghamia lanceolata forest in Sanming City, Fujian, China. The H2SO4 hydrolysis method was used to determine soil organic nitrogen fractions and their driving factors in the 0-10 cm and 10-20 cm soil layers after 5 years of harvest residue treatments. The results showed that residue retained treatment significantly enhanced the contents of soil organic nitrogen and its liable fractions. In the 0-10 cm soil layer, soil organic nitrogen content under residue retained treatment (3.36 g·kg-1) was 1.5 and 1.3 times as those of residue removed and residue burnt treatments, respectively. Residue retained treatment had the highest contents of labile nitrogen Ⅰ and Ⅱ fractions. In 10-20 cm soil layer, the contents of soil organic nitrogen and labile nitrogen Ⅱ fraction were also significantly higher in residue retained treatment (2.20, 0.73 g·kg-1) than that in residue removed and residue burnt treatments. The labile nitrogen index Ⅱ in residue retained treatment (33.9%) was significantly higher than in residue burnt treatment (26.1%). The contents of total carbon, dissolved organic carbon, dissolved organic nitrogen, microbial biomass under residue retained treatment were the highest in both soil layers. Compared with residue removed treatment, residue retained treatment significantly enhanced the abundance of soil bacteria (Gram-positive bacteria and Gram-negative bacteria) in 0-10 cm soil layer. In 10-20 cm soil layer, residue retained treatment had the highest content of fungi and the lowest content of actinomycetes. Pearson analysis showed that there were significant positive correlations of labile fractions of soil organic nitrogen with total carbon, dissolved organic carbon, dissolved organic nitrogen, microbial biomass carbon, microbial biomass nitrogen, bacteria (Gram-positive bacteria, Gram-negative bacteria), and fungi, and negative correlations with actinomycetes. It was concluded that the retention of harvest residue was beneficial to increase the content of soil organic nitrogen and labile fractions, improve soil biochemical properties and had a positive effect on soil microbial community composition. Retention of harvest residue was an effective management measure to maintain soil fertility and improve forest productivity.

Root-soil facilitation in mixed Eucalyptus grandis plantations including nitrogen-fixing species

The success of mixed plantation systems is ultimately the net result of positive and negative interactions, including belowground interactions, among the respective species. Despite increasing knowledge on positive interactions on biomass and productivity in mixed-species plantations, relatively little is known about the mechanisms underlying belowground interactions. Based on biodiversity data from four mixed Eucalyptus grandis plantations, we determined the optimal ecological facilitative interactions of mixed plantation, i.e., E. grandis and Alnus formosana. We then investigated in situ root exudation of E. grandis using a cuvette-based method and analysed root patterns, defence chemicals, bacterial communities, and biochemical properties of rhizosphere soils in mixed E. grandis with alder. Compared with pure Eucalyptus plantations, the fine root production by E. grandis was higher in subsoil layers (40–80 cm) in mixed plantations with alder. Autotrophic root respiration and associated enzymes were also increased in mixed plantations. Root exudates and defence allelochemicals of E. grandis changed in the presence of alder. Compared with the pure Eucalyptus plantations, E. grandis roots in mixed plantations reduced the release of potential allelochemicals, such as phenolic acids, flavonoids, unsaturated lactone, and glycosides. Methyl jasmonate, a common signal chemical, was significantly decreased in mixed-species plantations. The bacterial community of E. grandis rhizosphere soil was improved in mixed stands and recruited more nitrifying, N-fixing, and cellulose-decomposing bacteria, such as family Nitrosomonadaceae, genera MND1, Marmoricola, and Rikenellaceae RC9 gut groups. Thus, belowground ecological facilitative interactions occurred in mixed plantations with alder, which were due to E. grandis altering its rooting pattern, reducing the levels of released allelochemicals, recruiting more beneficial bacteria, and improving the biochemical properties of rhizosphere soil. This mechanism may be useful in reforestation programs for Eucalyptus monocultures that are suffering from problems associated with low biodiversity and reduced soil fertility.

No-Tillage Combined with Appropriate Amount of Straw Returning Increased Soil Biochemical Properties

(1) Background: Few studies have focused on the interaction of tillage and straw returning on soil carbon and nitrogen. Therefore, this study was conducted for investigating the effects of tillage and straw returning on soil biochemical properties under a rice–wheat double cropping system; (2) Methods: Six treatments were set up to determine soil biochemical properties, including no-tillage with all straw returning (NTS), wheat plow tillage and rice no-tillage with half straw returning (RT1), wheat no-tillage and rice plow tillage with half straw returning (RT2), plow tillage with all straw returning (CTS), less tillage with half straw returning (MTS), and plow tillage with no straw returning (CT); (3) Results: Straw returning increased soil microbial biomass carbon (SMBC) and soil microbial biomass nitrogen (SMBN), but had no significant effects on total nitrogen (TN) and soil organic carbon (SOC). In the treatments of straw returning, the contents of SMBC, SMBN, TN, and SOC under no-tillage were increased in the 0–7 cm soil layer. Tillage and straw returning had no significant effects in the 7–14 cm and 14–21 cm soil layers. In addition, SMBC/SMBN for all the treatments was maintained within a reasonable range, and microbial quotient (SMQ) and SMBN/TN in the no-tillage treatment had a significant improvement; (4) Conclusions: The results showed that no-tillage with an appropriate amount of straw returning improved the soil biochemical properties and maintained the nitrogen mineralization capacity in the 0–7 cm soil layer for this region.

Effect of biostimulant and biofertilizers on soil bio-chemical properties and plant growth of apple (Malus x domestica Borkh.) nursery

Aim: To assess the effect of biostimulant and biofertilizers on soil properties and plant growth of apple nursery under eco-friendly production system. Methodology: The experiment was laid out in a randomized block design comprising 18 treatments of biostimulant, biofertilizers and their combinations. Each treatment was replicated thrice. Nursery beds of apple seedling rootstocks were prepared and Arbuscular mycorrhizal fungi, PGPR (Bacillus sp.) were applied by soil drenching method and commercial formulations of granular bio-stimulant containing humic acid (39%) + kelp extract (25%) + amino acids (9.0%) + ascorbic acid + thiamine + inositol + tocopherol (27%) were applied in two split doses by broadcasting in root zone. The effects of these various formulations were investigated during the course of studies. Results: Linear growth, radial growth of scion (6.66 mm), number of leaves per plant, leaf area, success rate, saleable plants, total root length, fresh weight of shoots, dry weight of shoots, fresh weight of roots, dry weight of roots and total plant biomass of apple nursery plants were significantly increased with the combined application of biostimulant (200 g m-2 nursery bed) + AM fungi (20 g per plant) + PGPR (50 ml per plant). This treatment also significantly improved the status of available soil N, P, K and population of fungi, bacteria as well as actinomycetes in the rhizosphere. Interpretation: Application of biostimulant (200 g m-2 nursery bed) + AM fungi (20 g per plant) + PGPR (50 ml per plant) proved to be the most effective combination of eco-friendly inputs for the production of good quality apple nursery plants with well developed shoot and root system and improved the soil bio-chemical properties.

Contrasting assembly mechanisms and drivers of soil rare and abundant bacterial communities in 22-year continuous and non-continuous cropping systems

Despite many studies on the influence of cropping practices on soil microbial community structure, little is known about ecological patterns of rare and abundant microbial communities in response to different tobacco cropping systems. Here, using the high-throughput sequencing technique, we investigated the impacts of two different cropping systems on soil biochemical properties and the microbial community composition of abundant and rare taxa and its driving factors in continuous and rotational tobacco cropping systems in the mountain lands of Yunnan, China. Our results showed that distinct co-occurrence patterns and driving forces for abundant and rare taxa across the different cropping systems. The abundant taxa were mainly constrained by stochastic processes in both cropping systems. In contrast, rare taxa in continuous cropping fields were mainly influenced by environmental perturbation (cropping practice), while governed by deterministic processes under rotational cropping. The α-diversity indices of rare taxa tended to be higher than those of the abundant ones in the two cropping systems. Furthermore, the network topologies of rare taxa were more complex than those of the abundant taxa in the two cropping systems. These results highlight that rare taxa rather than abundant ones play important roles in maintaining ecosystem diversity and sustaining the stability of ecosystem functions, especially in continuous cropping systems.

Effect of nitrogen limitation and soil biophysics on Holocene greening of the Sahara

Abstract. The so-called Green Sahara (GS), which was a wet and vegetative Sahara region in the early to mid-Holocene, provides useful information on our climate simulation because it is a consequence of complex interaction between biophysical and climatic processes. It is still a challenge to simulate the GS in terms of vegetative extent and precipitation using current climate models. This study attempts to simulate the Green Sahara 8000 years ago by using the state-of-the-art Earth system model CESM that incorporates the nitrogen cycle and the soil–precipitation feedbacks. Our study puts more emphasis on the impact of soil biophysical properties (e.g., bare-soil albedo, porosity, heat capacity, and hydraulic conductivity) and soil nitrogen influenced by soil organic matter on the simulation of the GS. In this coupled simulation, vegetation interacts with changes in soil properties and soil organic matter by phenology, decomposition, and allocation of carbon and nitrogen. With changes in the Earth's orbit and dust in the early to mid-Holocene, the model simulates increased precipitation in North Africa but does not capture the extent of the GS. Our analysis shows that the Holocene greening is simulated better if the amount of soil nitrogen and soil texture is properly modified for the humid and vegetative GS period. Soil biochemical and physical properties increase precipitation and vegetation cover in North Africa through their influence on photosynthesis and surface albedo as well as their consequent enhanced albedo–precipitation and evapotranspiration–precipitation feedbacks. Our findings suggest that future climate simulation needs to consider consequent changes in soil nitrogen and texture with changes in vegetation cover and density for proper climate simulations.

Effects of Thinning Intensity on Forest Floor and Soil Biochemical Properties in an Aleppo Pine Plantation after 13 Years: Quantity but Also Quality Matters

In order to quantify the impacts of silvicultural treatments in semiarid forests, it is necessary to know how they affect key aboveground processes and also properties characterizing the forest floor and mineral soil compartments. The general objective of this work is to study the mid-term effects of thinning intensity on forest floor and soil properties after 13 years following the intervention. The experimental design consisted of a randomized block design with four thinning treatments (3 thinning intensity plots plus a control or unmanaged plot) and three blocks or replicates. Several determinations, such as total organic carbon, dissolved organic carbon, or basal respiration, were performed for characterizing forest floor and mineral soil by considering three random sampling points per experimental plot. Thirteen years after thinning, total organic content, the different organic carbon fractions studied, and basal respiration were higher in the forest floor of the unmanaged plot. These results, however, were contrasted to those obtained for the mineral soil, where significant differences between the treatments were only observed in basal respiration and C/N ratio, while the different organic carbon fractions were not affected by thinning intensity. Our results suggest better soil quality where biological activity is enhanced as a consequence of improved environmental conditions and also litterfall input. The latter is especially important in forests with tree leaves of low biodegradability, where new understorey species promoted by thinning can provide higher nutrient availability for the remaining trees and, therefore, better forest resilience.

Role of forest site type in determining bacterial and biochemical properties of soil

• The biological properties of the soil are determined by the site type. • The tested soils are significant differences in microbiological activity. • Soil from fresh mixed boron is the most fertile soil. The aim of the present study was to investigate the effect of forest site type on the bacterial and biochemical properties of the soil. Data for counts, diversity, and composition of bacterial communities, as well as soil enzymatic activity, was used for the assessment. A determination of the relationships between the parameters was also performed. Soil samples were collected in the Stare Jabłonki Forest Division (north-eastern Poland, Central Europe) from four sites: fresh coniferous forest (Fc), fresh mixed coniferous forest (Fm), fresh mixed forest (Mf), and moist mixed forest (Mm). The tested soils showed significant differences in enzyme activity and microflora. Organotrophic bacteria and actinobacteria proliferated the most in soil from fresh mixed coniferous forest. Organotrophic bacteria grew faster than actinobacteria in the soil, indicating that the former were represented by r-strategists, and the latter – by K-strategists. The soil sampled from site Fc2 (fresh coniferous forest) had the highest values of the diversity index. Alphaproteobacteria (phylum Proteobacteria ) were the dominant bacterial class in the soils, followed by Actinobacteria (phylum Actinobacteria ) and Acidobacteriia (phylum Acidobacteria ). Phyla Proteobacteria , Actinobacteria, and Acidobacteria were most abundantly represented by genera Rhodoplanes, Mycobacterium , and Candidatus Solibacter , respectively. According to the biochemical soil quality index (BA), the soil sampled from site Fc2 (fresh mixed coniferous forest) was the most fertile. The study demonstrates that microbial and biochemical parameters of the soil can serve as an accurate indicator of the status and health of forest ecosystems.

Contrasting response of soil N2O release to ammonium, nitrate, and urea addition rates is determined by substrate availability and microbial community abundance and composition

Although nonlinear responses of soil nitrous oxide (N2O) release to exogenous nitrogen (N) input have been reported, the contrasting effects of oxidized and reduced N forms and their driving mechanisms have rarely been investigated. Here, a 91-day microcosm incubation experiment with three forms (ammonium, nitrate, and urea) and eleven rates (0, 1, 2, 4, 6, 8, 10, 12, 14, 28, and 56 g N m−2 yr−1) of N addition was conducted to determine the response dose, saturation threshold, and turning point of N2O release from the temperate forest soil. Simultaneously, soil biochemical properties, N-cycling functional gene abundances, and bacterial and fungal community composition were determined to assess the biotic and abiotic contributions to changes in soil N2O release. The responses of soil N2O release rate to ammonium, nitrate, and urea addition rates exhibited saturation, sigmoidal, and exponential curves, respectively. The response dose of soil N2O release was higher in urea addition than in ammonium and nitrate additions (28 g N m−2 yr−1 vs. 8 g N m−2 yr−1). The tipping point and saturation thresholds for ammonium and nitrate additions were estimated to be 14 g N m−2 yr−1 and 56 g N m−2 yr−1, respectively, whereas neither occurred in urea addition. Except high rate of ammonium addition (≥28 g N m−2 yr−1), N inputs significantly increased AOB abundance and promoted soil NO3−-N accumulation. Also, N addition, especially high-rate ammonium, led to a shift in bacterial community from oligotrophic to copiotrophic groups. Oxidized nitrate input increased soil NO3−-N content and changed bacterial and fungal community structure, whereas reduced ammonium and urea additions increased soil NH4+-N content and AOB abundance, as well as altered bacterial community. These findings highlight that N forms contrastingly affect soil N2O release. Substrate availability, functional gene abundance, and microbial community composition equally contribute to soil N2O release, which should be considered in terrestrial ecosystem process models.

Effects of different vegetation restoration on soil nutrients, enzyme activities, and microbial communities in degraded karst landscapes in southwest China

The karst area in southwestern China is one of the largest and continuous karst landforms in the world, and its ecosystem is highly sensitive and fragile. Appropriate vegetation restoration modes are of great significance for sustaining and improving the stability of the karst ecosystem, the dominant landform type in southwest China. Bacteria, linking soil and plants, play an important role in regulating the succession and restoration of karst vegetation. However, it remains unclear how soil bacterial communities and soil biochemical properties respond to vegetation restoration practices in karst areas. In this study, a 13-year long-term trial was performed using three planting restoration modes of deciduous broad-leaved, mixed evergreen and deciduous broad-leaved forest, and evergreen broad-leaved forests, with controls of natural enclosure. We aimed to investigate the impact of different vegetation restoration modes on the structure of soil microbial communities and their driving mechanisms using 16S rDNA Illumina sequencing, combined with the determination of 11 soil indicators and statistical models. The results showed that artificial restoration can improve soil nutrient contents, enzyme activities and microbial biomass more effectively than natural closure, which is beneficial to the rapid restoration of vegetation after abandoning of farmland. Among them, the effect of deciduous broad-leaved treatment on artificial restoration mode was better than that of mixed evergreen and deciduous broad-leaved forest and evergreen broad-leaved forest. In sequencing results, artificial restoration increased the relative abundance of Proteobacteria, but decreased that of Acidobacteria. In addition, pH, soil microbial biomass carbon, and urease activity significantly increased bacterial diversity. Different vegetation restoration measures significantly changed the soil bacterial community structure. The bacterial community of deciduous broad-leaved forest was the most beneficial to the benign development of soil. Mantel test showed that pH and soil microbial biomass carbon and nitrogen were the key driving factors of the soil bacterial community. FAPROTAX analysis showed a significant positive correlation between sucrase activity and phototrophy functional bacteria. The results demonstrated that compared with natural enclosure, artificial vegetation restoration promoted rapid community succession, and construction of deciduous broad-leaved forest was the most effective way to manage karst areas, improve soil nutrients, alter its key microbial populations, promote ecosystem services, and eventually benefit the restoration of vegetation in karst areas.

C:N:P stoichiometry associated with biochar in forest soils at historical charcoal production sites in Poland

Biochar amendment leads to change of physical, chemical and biochemical properties of soil. The aim of our research was to determine C/N/P stoichiometry of soils with biochar in pine forest in places of historical charcoal production. The research was carried out in the Manowo Forest District, northern Poland (54°08′52″N; 16°27′53″E). The research was carried out in an area where relict charcoal hearths are abundant. The burning of charcoal in this area took place about 200–250 years ago. Pine wood was used in relict charcoal hearths. The samples for analysis were taken from relict charcoal hearths and in the immediate vicinity (background). We determined the enzymatic activity and we recorded the content of C, N and P in testing samples. We also calculated the C/N/P stoichiometry for samples and we used soil enzyme activity stoichiometry for reflects the nutrient availability. Our research confirmed the role of biochar in shaping the C/N/P stoichiometry in forest soils. Soils with biochar were characterized by wider stoichiometry and significantly higher C and P content compared to the control soils. The enrichment of the soil with biochar resulted in a significant increase in the activity of enzymes involved in the carbon cycle (β-glucosidase and β-D-cellobiosidase), nitrogen (N-acetyl-β-D-glucosaminidase) and phosphorus (phosphatase). The enzyme stoichiometry confirmed limited availability of nutrients, especially nitrogen. Biochar in historical charcoal production sites increased total carbon stocks in temperate pine forests. This implied that relict charcoal hearths can significantly promote the carbon sequestration capacity.

Nutrient cycling and microbial responses to termite and earthworm activity in soils amended with woody residues in the Sudano-Sahel

Termites and earthworms are the main groups of invertebrates in dry tropical ecosystems and exert significant effects on bioturbation and soil reorganization. The dynamics of microbial communities, enzymes and substrates associated with the flux of energy and nutrients induced by their diverse biogenic structures are still under-investigated in agroecological-based cropping systems. The objective of this study was to determine whether the biogenic structures produced by a grass-woody forager termite (Nasutitermes torquatus) and an endogeic earthworm (Millsonia inermis) shift soil organic C (OC), nutrients, enzyme activities and microbial communities in soils amended with woody residues. The experiment was a randomized block design conducted in a Sudano-Sahelian cropping system that was amended annually with woody residues (3 Mg ha−1) or not amended (control soils) for six consecutive years. Samples were taken from fresh sheetings and casts (produced respectively by N. torquatus and M. inermis) and bulk soils in amended plots as well as from control soils in nonamended plots. Samples were analyzed for soil texture, OC, total nitrogen (N), available phosphorus (P), pH, enzyme activity and microbial composition. The results showed that sheetings and casts altered soil biochemical properties significantly. Sheetings and casts were remarkably enriched in OC (45–55% and 82–94%, respectively) and P (20–55% and 73–130%) compared to bulk soils and control soils. Sheetings and casts substantially stimulated β-glucosidase (153–178% and 158–183%, respectively) and N-acetyl-β-glucosaminidase (43–53% and 84–93%) activity, likely due to gut mucus excretions and favorable physicochemical conditions. Sheetings and casts did not fundamentally alter the microbial diversity but raised soil conditions favorable to selective microbial growth. Overall, casts exhibited higher nutrient content (N, P), enzyme activity, and larger total microbial biomass than sheetings. Both structures stimulated soil microbial communities and enzyme activity associated with the increase of pH, OC and nutrients. Earthworm casts and termite sheetings have ecological significance in OC dynamics in plant residues amended soils.

Biochar incorporation increases winter wheat (Triticum aestivum L.) production with significantly improving soil enzyme activities at jointing stage

The responses of yield production and soil nutrients availability to agricultural organic inputs are crucial for cropland management. However, the simultaneous impacts of straw-derived biochar and straw addition on yield production and soil properties (e.g., soil enzyme activities at winter wheat growing stages) as well as their potential relationships remain poorly evaluated in semi-arid areas. Here, a field experiment based on the long-term study (i.e., commenced in 2011) was conducted in the semi-arid Chinese Loess Plateau to explore the responses of soil water storage (SWS), winter wheat (Triticum aestivum L.) yield and a range of soil biochemical properties to straw-derived biochar and straw addition in 2018–2019 and 2019–2020. The four treatments were: 1) no straw and no biochar (Control), 2) conventional straw mulching (SM), 3) straw incorporated into the soil (SI), and 4) straw-derived biochar incorporated into the soil (BI). We found that the BI treatment on average increased SWS in 0–160 cm soil depth by 13%, 17%, and 21% across entire growing seasons, respectively, when compared to the SM, SI and Control treatments. Enhancements in grain yield and aboveground biomass were related to the BI treatment-induced increases in soil carbon and nitrogen content. The BI treatment had higher soil enzyme activities at jointing stage than at grain filling and maturity stages during winter wheat growing seasons. The mixed-effects models showed there were significant effects of growth stage and soil depth on soil microbial biomass and soil dissolved organic carbon and nitrogen, even when analyzed by each growing season. Moreover, no significant relationships were found between SWS and soil enzyme activities (invertase, urease, catalase, and alkaline phosphatase). Therefore, straw-derived biochar incorporation could be one of the appropriate practices for increasing crop yield and sustaining soil fertility in the Chinese Loess Plateau and other areas with similar climates.

Assessment of soil biochemical properties and soil quality index under rainfed land use systems in submontane Punjab, India

The conversion of natural systems to cultivated systems contributes to changes in the activities of microbial communities and biochemical processes in the soil. A total of 80 surface soil samples (0-15 cm) from 6 rainfed land use systems viz. agriculture, horticulture, agri-horticulture, forest, agroforestry and eroded lands were analyzed for biochemical properties and to derive soil quality index. The soils are slightly acid to neutral in reaction (pH-6.4-6.9) with 0.09-0.23 dS m−1 electrical conductivity (EC), loamy sand to sandy loam in texture, 1.4-6.1 g kg−1 soil organic carbon (SOC), 86-406 kg ha−1 available nitrogen, 29.3-32.6 kg ha−1 available phosphorus,65-226 kg ha−1 available potassium,10.3-21.3 mg kg−1 DTPA-Mn, 12.1-34.2 mg kg−1 DTPA-Fe, 0.34-1.01 mg kg−1 DTPA-Cu and 0.76-1.15 mg kg−1 DTPA-Zn, respectively under different land use systems. Among soil biochemical properties, the enzymic activity among land use systemsis varied from 7.4 to 12.8 µg TPF g−1 h−1 for dehydrogenase activity, 22.3 to 34.5 µg pNP g−1 h−1 for acid phosphatase, 43.4 to 60.1 µg pNP g−1 h−1 for alkaline phosphatase, 3.31 to 4.77 µg NH4-N g−1 soil min−1 for urease activity-, basal soil respiration −0.13 to 0.30 µg CO2 g−1 soil h−1 for basal respiration , 46.5 to 242.6 µg g−1 soil for soil microbial biomass carbon (MBC) and 8.68 to 30.6 g kg−1 for total easily extractable glomalin (TEGP), respectively. The principle component analysis showed that SOC, EC, TEGP, MBC and DTPA-Zn are robust soil quality indicators under different land use systems in submontane Punjab. The forestry system has higher values for physicochemical, biochemical properties and soil quality index as against agri-horticulture, horticulture, agroforestry, agriculture and eroded system. In subsystems, eucalyptus-based forestry and mango based agri-horticulture systems are served as a better system for soil quality assessment in submontane Punjab, India.

Seasonal and Spatial Variations in Soil Biochemical Properties in Areas with Different Degrees of Mining Subsidence in Central China

Seasonal and Spatial Variations in Soil Biochemical Properties in Areas with Different Degrees of Mining Subsidence in Central China

Changes in Soil’s Chemical and Biochemical Properties Induced by Road Geometry in the Hyrcanian Temperate Forests

Forest roads play an important role in providing access to forest resources. However, they can significantly impact the adjacent soil and vegetation. This study aimed to evaluate the effects of road geometry (RG) on the chemical and biochemical properties of adjacent soils to assist in environmentally friendly forest road planning in mountainous areas. Litter layer, canopy cover, soil organic carbon (SOC) stock, total nitrogen (TN), the activity of dehydrogenase (DHA), and urease (UA) enzymes at a 0–20 cm soil depth were measured by sampling at various distances from the road edge to 100 m into the forest interior. The measurements were done for three road geometries (RG), namely straight, curved, and bent roads, to ensure data heterogeneity and to reflect the main geometric features of the forest roads. Analysis of variance (ANOVA) showed that the effects of RG on the measured variables were statistically significant. Spearman’s correlation test clearly showed a strong positive correlation between environmental conditions, SOC, TN, DHA, and UA for given RGs. Based on piecewise linear regression analysis, the down slope direction of the straight and the inside direction of bent roads accounted for the lowest and highest ranges of ecological effects, respectively. The results of this study contribute to our understanding of the environmental effects brought about by road geometry, which can be important for forest road managers when applying the best management practices.

Remediation of Cd-, Pb-, Cu-, and Zn-contaminated soil using cow bone meal and oyster shell meal

To understand the environmental friendliness and high efficiency of organic materials during remediating soil polluted by heavy metals by assessing the feedback of soil ecosystems after organic materials were put into polluted soil. Incubation research was undertaken to examine the impact of amendments ranging from 0.1% to 3.0% (w/w), including single cow bone meal (BM), single oyster shell meal (OS), and a composite of 50% BM mixed with 50% OS (BO) on soil biochemical properties. The findings revealed that the implementation of BM and OS increased soil pH, the content of certain nutrients, and the activities of catalase (S-CAT), and urease (S-UE) while decreasing the availability of Cd, Pb, Cu, and Zn. Overall, the immobilization effect on Cd and Zn after a 108-day incubation was ranked as follows: BM group > OS group ≥ BO group, and the order of the immobilization effect of Pb and Cu was OS group > BO group > BM group. In addition, the dominant bacterial community flora shifted toward alleviating the re-dissolution of metal ions from the soil and promoting nutrient recycling in soil within 108 days of cultivation. RNA analyses showed that the strongest determinants for microbial communities between BM application and OS application at the genus level were soil pH, CEC, and heavy metal (Cd, Pb). These results increase our understanding of the leaching performance of Cd, Pb, Cu and Zn and the evolution trend of microorganisms when organic amendments remediate heavy metal contaminated soil.