Effect of biochar on biochemical properties of saline soil and growth of rice.

To amend physical properties of coastal saline soil for rice production, six biochar treatments (0, 0.5, 1, 2, 4 and 6 kg biochar per m2 soil) were set up as CK, T1, T2, T3, T4 and T5, respectively and their effect on the biochemical properties of coastal saline soil and rice growth characteristics were evaluated in a barrel planting experiment. The results showed that compared with CK (with no biochar added), the soil EC of T1 and T2-T5 was reduced by 11.5 %, but increased by 8.8-62.9 %, respectively. The available potassium and organic matter contents of T1-T5 increased ranging from 3.7-10.2 % to 8.0-46.8 %, respectively. With the increase of the biochar amount, the urease activity of soil in the 0-10 cm deep soil showed an increasing trend by 194.8-744.6 % with T1-T5, compared with that of the CK treatment. The activity of alkaline phosphatase in soil increased first and then decreased, and its increment with T1-T5 was between 28.2 and 64.8 % in comparison with that of CK. With more biochar added to soil, the leaf dry weight, root dry weight, total dry matter mass, total root length, single panicle quality and weight per 100 grains showed a trend of increase first and then decrease. The highest incremental values of all measurements were obtained with T1 by 21.8 %, 23.9 %, 13.8 %, 33.9 %, 30.8 % and 11.6 % respectively, compared with those with CK. However, adding biochar in soil demonstrated insignificant effect on the weight of single panicle, panicle length, stem thickness, tillers, setting rate, soil hydrolyzable nitrogen, available phosphorus content, rice protein, amylose, and taste quality among all treatments. In summary, the application of 0.5 kg m-2 biochar can improve the biochemical properties of saline soil and therefore increase rice yield.

Elucidating the impact of biochar with different carbon/nitrogen ratios on soil biochemical properties and rhizosphere bacterial communities of flue-cured tobacco plants.

Background and aims: In agriculture, biochar (BC) and nitrogen (N) fertilizers are commonly used for improving soil fertility and crop productivity. However, it remains unclear how different levels of BC and N fertilizer affect soil fertility and crop productivity. Methods: This study elucidates the impact of different application rates of BC (0, 600, and 1200 kg/ha) and N fertilizer (105 and 126 kg/ha) on biomass accumulation, soil microbial biomass of carbon (SMC) and nitrogen (SMN), and soil biochemical properties, including soil organic carbon (SOC), total nitrogen (TN), soil nitrate nitrogen (NO3--N), ammonium nitrogen (NH4+-N), urease (UE), acid phosphatase (ACP), catalase (CAT), and sucrase (SC) of tobacco plants. In addition, a high throughput amplicon sequencing technique was adopted to investigate the effect of different application rates of BC/N on rhizosphere bacterial communities of tobacco plants. Results: The results confirm that high dosages of BC and N fertilizer (B1200N126) significantly enhance dry matter accumulation by 31.56% and 23.97% compared with control B0N105 and B0N126 under field conditions and 23.94% and 24.52% under pot experiment, respectively. The soil biochemical properties, SMC, and SMN significantly improved under the high application rate of BC and N fertilizer (B1200N126), while it negatively influenced the soil carbon/nitrogen ratio. Analysis of rhizosphere bacteriome through amplicon sequencing of 16S rRNA revealed that the structure, diversity, and composition of rhizosphere bacterial communities dramatically changed under different BC/N ratios. Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes, and Acidobacteria were highly abundant bacterial phyla in the rhizosphere of tobacco plants under different treatments. Co-occurrence network analysis displayed fewer negative correlations among rhizosphere bacterial communities under high dosages of biochar and nitrogen (B1200N126) than other treatments, which showed less competition for resources among microbes. In addition, a redundancy analysis further proved a significant positive correlation among SMC, SMN, soil biochemical properties, and high dosage of biochar and nitrogen (B1200N126). Conclusions: Thus, we conclude that a high dosage of BC (1200 kg/ha) under a high application rate of N fertilizer (126 kg/ha) enhances the biomass accumulation of tobacco plants by improving the soil biochemical properties and activities of rhizosphere bacterial communities.

Compositional Shifts and Assembly in Rhizosphere-Associated Fungal Microbiota Throughout the Life Cycle of Japonica Rice Under Increased Nitrogen Fertilization.

Soil fungal microbiomes facilitate a range of beneficial functions for their host plants, and rhizosphere fungal community composition, richness, and diversity affect plant growth and development, and crop yield. Therefore, exploring the community structure and assembly of the rhizosphere fungal microbiome and its relationship with soil biochemical properties are fundamental to elucidating how rice plants benefit from their fungal symbionts. In this study, soil samples were collected at seedling, tillering, heading, and ripening stages of rice subjected to three levels of nitrogen fertilization. Plant growth demonstrates a substantial influence on fungal community composition and diversity. From the tillering to the ripening stage, the fungal communities were governed by homogenizing dispersal and dispersal limitation. The prevalence of Glomeromycota, the beneficial fungi, was considerably higher during the heading stage compared to the three other growth stages. This increase in abundance was strongly associated with increased levels of soil nutrients and enhanced activity of nitrogen acquisition enzymes. This may be a strategy developed by rice grown in flooded soil to recruit beneficial fungi in the rhizosphere to meet high nitrogen demands. Our study findings contribute to elucidating the influence of plant development and nitrogen fertilization on the structure and composition of the fungal community as well as its relationship with soil key soil nutrient content and nitrogen-related enzyme activities. They also illustrate how a shift in the fungal community mediates and reflects the effects of nitrogen fertilization input in rice agroecosystems. These findings provide new insights into the effects of changes in nitrogen application in rice rhizosphere at different growth stages on fungal communities and soil biochemical characteristics.

Evaluation and Assessment of Trivalent and Hexavalent Chromium on Avena sativa and Soil Enzymes.

Chromium (Cr) can exist in several oxidation states, but the two most stable forms-Cr(III) and Cr(VI)-have completely different biochemical characteristics. The aim of the present study was to evaluate how soil contamination with Cr(III) and Cr(VI) in the presence of Na2EDTA affects Avena sativa L. biomass; assess the remediation capacity of Avena sativa L. based on its tolerance index, translocation factor, and chromium accumulation; and investigate how these chromium species affect the soil enzyme activity and physicochemical properties of soil. This study consisted of a pot experiment divided into two groups: non-amended and amended with Na2EDTA. The Cr(III)- and Cr(VI)-contaminated soil samples were prepared in doses of 0, 5, 10, 20, and 40 mg Cr kg-1 d.m. soil. The negative effect of chromium manifested as a decreased biomass of Avena sativa L. (aboveground parts and roots). Cr(VI) proved to be more toxic than Cr(III). The tolerance indices (TI) showed that Avena sativa L. tolerates Cr(III) contamination better than Cr(VI) contamination. The translocation values for Cr(III) were much lower than for Cr(VI). Avena sativa L. proved to be of little use for the phytoextraction of chromium from soil. Dehydrogenases were the enzymes which were the most sensitive to soil contamination with Cr(III) and Cr(VI). Conversely, the catalase level was observed to be the least sensitive. Na2EDTA exacerbated the negative effects of Cr(III) and Cr(VI) on the growth and development of Avena sativa L. and soil enzyme activity.

Effects of different rotation cropping systems on potato yield, rhizosphere microbial community and soil biochemical properties.

Continuous potato cropping systems cause yield reduction, soil-borne disease aggravation, and soil degradation, but crop rotation can alleviate these negative effects. However, there are limited studies on the relationships between microbial community and other soil biochemical properties of continuous potato cropping at both pre-planting and harvest in North China. A 4-year study was conducted to explore the effects of different rotation system on soil biochemical properties, microbial community at pre-planting and harvest, and potato yield, tuber number and black scurf incidence at harvest in 2020 and 2021, which included 4 treatments vis. potato-potato-potato-potato (PC), potato-oat-faba bean-potato (PR), oat-faba bean-potato-oat (O), and faba bean-potato-oat-faba bean (B). The results showed that soil biochemical properties and microbial community among all treatments showed no significant difference at pre-planting after a long cold winter generally. At harvest, PC reduced tuber yield and number and significantly increased black scurf incidence relative to potato rotation systems. PC also reduced soil enzyme activities, the content of soil nutrients, and fungal community diversity, and increased bacterial community diversity compared with the other treatments, insignificantly when compared with PR. Relative abundance of microorganisms related to the degradation of organic residues, soil nitrogen cycling, and disease suppression, such as the genera Devosia, Aeromicrobium, Paraphoma, and Papiliotrema, were significantly higher in O or B than in PC and PR, while microorganisms related to disease infection such as the genera Pseudomonas, Colletotrichum, Plectosphaerella, Fusarium, and Verticillium exhibited increased in PC and PR. Principal Coordinates Analysis (PCoA) showed that there were significant differences in the microbial community structure of PC and PR at harvest compared with that of O and B. Redundancy analysis (RDA) revealed that soil available potassium (AK), acid phosphatase (ACP), available phosphorus (AP), sucrase (SUC) and pH were the dominant factors that significantly affected bacterial and fungal community structure. Partial least squares structural equation model indicated rotation system had significant negative effect on fungal community. It was concluded that growing oat or faba bean after potato can increase soil beneficial microorganisms and maintain the ecosystem healthy, thus reducing the incidence of tuber black scurf and increasing potato yield.

Bioremediation of cadmium polluted soil using a novel cadmium immobilizing plant growth promotion strain Bacillus sp. TZ5 loaded on biochar.

Bioremediation of cadmium polluted soil using biochar (BC) and plant growth promotion bacteria (PGPB) have been widely concerned. In our study, a novel Cd immobilizing PGPB strain TZ5 was isolated based on the Cd immobilizing potential and plant growth promotion (PGP) traits. Further, changes of surface morphology and functional groups of TZ5 cells were observed after exposed to Cd2+ by SEM-EDS and FTIR analyses. Then, the strain TZ5 was successfully loaded on BC as biochemical composites material (BCM). Pot experiment indicated that the percentage of acetic acid-extractable Cd in BCM treatments significantly decreased by 11.34 % than control. Meanwhile, BCM significantly increased the dry weight of ryegrass by 77.78 %, and decreased the Cd concentration of ryegrass by 48.49 %, compared to control. Microbial counts and soil enzyme activities in rhizosphere were both significantly improved by BCM. Furthermore, the proportion of relative abundance of Bacillus genus was enhanced after treated by BCM, which indicated that the strain TZ5 was successfully colonized in the rhizosphere. This study provided a practical strategy for bioremediation of Cd contaminated soil.

Dataset of soil bacterial compositions and biochemical properties of a Moso bamboo forest under mulching-intensive management.

Bacterial 16S rRNA dataset of Moso bamboo forest was formed by 20 soil samples in four management modes corresponding to the soil properties data of each soil sample such as concentrations of soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), available phosphorus (AP), NH4 +-N, NO3 --N, water-soluble organic carbon (WSOC), Water-soluble organic nitrogen (WSON), microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN), and soil water content (SWC) and pH value. Due to the special climate in the northern edge of subtropical zone and the characteristics of non wood and non grass of bamboo plants, our data set is helpful for the further studies of soil management, microhabitats variations responding to global carbon, nitrogen and phosphorus cycle. The data is related to the research article "Response of bacterial compositions to soil biochemical properties under mulching-intensive management in a Phyllostachys edulis forest" [1].

Impacts of a novel strain QY-1 allied with chromium immobilizing materials on chromium availability and soil biochemical properties.

In-situ passivation of soil chromium (Cr) contamination based on chemical and biological passivators has been widely concerned, however, the cooperative effect of two types of passivators on Cr passivation and soil properties was little investigated. In this study, nano zero valent iron (nZVI) and humic acid (HA) as the chemical passivators were selected and were combined with a novel Cr resistant strain QY-1 to study these two points. Results demonstrated that the combination was more effective in Cr immobilization, among which, HA + QY-1 had the highest passivation rate (82.83%), followed by nZVI + QY-1. HA + QY-1 alleviated soil Cr stress most efficiently as its soil relevant fertility indicators, microbial quantity, respiration and seed gemination rate significantly increased. On the contrary, nZVI decreased soil respiration and microbial abundance, but the addition of QY-1 could relieve this phenomenon. The results highlighted the ability of HA + QY-1 to remediate Cr contaminated soil and improve soil stability.

[Effects of Different Levels of Nitrogen Fertilization on Soil Respiration Rates and Soil Biochemical Properties in an Alfalfa Grassland].

Understanding the effects of different levels of nitrogen fertilizer applications on soil respiration rates and soil biochemical properties is of great importance for providing a theoretical basis for accurate assessments of the soil respiration intensity and carbon recycling in grassland ecosystems. A field experiment was performed from April 2017 to March 2018, in which four different levels of nitrogen applications were investigated, including 0 kg·hm-2 (N0), 60 kg·hm-2 (N1), 120 kg·hm-2 (N2), and 180 kg·hm-2 (N3). The seasonal changes in the soil respiration rate, soil temperature, and soil moisture in the alfalfa grassland under different levels of nitrogen applications were observed, and soil biochemical characteristics were observed after each harvest in the growing season. The results showed that soil respiration rate of the alfalfa grassland displayed significant seasonal variation under different nitrogen levels. In particular, the soil respiration rate reached a peak during the last 10-day period of July and then decreased to the minimum in mid-December. During the growing season of alfalfa, the soil respiration rate of the alfalfa grassland increased with the increases in the nitrogen application rate. The mean soil respiration rates of the N1, N2, and N3 treatments were 0.97, 1.04, and 1.07 g·(m2·h)-1, respectively, and these values were 10.2%, 18.2%, and 21.6% greater than that of N0[0.88 g·(m2·h)-1], respectively. The results from ANOVA testing indicated that nitrogen applications had no significant effect on the soil respiration rate during the non-growing season of alfalfa (P>0.05). According to the statistical analysis, the soil respiration rate had a significant exponential positive relationship with soil temperature during the growing season, non-growing season, and entire year of alfalfa grassland observations under different nitrogen application rates (P<0.01); the coefficients of determination were ranked as follows:growing season (0.46-0.62) < non-growing season (0.66-0.76) < whole year (0.80-0.86). Soil temperature (T) and soil moisture (W) interacted with each other and ultimately affected the soil respiration (RS), and by using a two-factor linear model of soil temperature and soil moisture, a better fit was obtained for the change in the soil respiration rate. Both of the two factors explained 68%-80% of the variation in the seasonal soil respiratory rate during the growing season of alfalfa. Nitrogen fertilization decreased the soil pH and available phosphorus content (AP) to varying degrees, but it increased the available potassium (AK), soil organic matter (SOM), and soil urease (URE) and invertase activity (INV). Total nitrogen (TN) and available nitrogen (AN) showed different trends under different nitrogen levels. The TN and AN contents increased considerably in soils; however, when the nitrogen rate was higher than N2 (120 kg·hm-2), TN and AN decreased with the increases in the nitrogen application rate. According to the correlation matrix analysis between soil respiration and soil biochemical properties during the growth period of alfalfa, data showed that the soil respiration rate (RS) was significantly and negatively correlated with soil pH (P<0.01), and it was significantly and positively correlated with soil TN and URE (P<0.01). Simultaneously, there was a significant positive correlation between the soil respiration rate (RS) and SOM (P<0.05), and there was a significant negative correlation with INV (P<0.05). The soil nutrient and enzyme activities of the alfalfa grassland explained the variations in the soil respiration rate under different nitrogen application levels to varying degrees.

Combining phytoextraction by Brassica napus and biochar amendment for the remediation of a mining soil in Riotinto (Spain).

Soil contamination in mining areas is an important environmental concern. In these areas, phytoremediation is often impeded because of the low fertility and pH. Assisted phytoremediation is increasingly being used in polluted areas. Biochar could assist plant growth via enhanced soil fertility. An experiment was performed in a mining soil (RIII) from the mining area of Riotinto (Spain) contaminated with Cu, Pb, Zn and As in order to study: (i) The effects of biochar on soil fertility; (ii) Biochar temperature of preparation effect and (iii) Effect of biochar on phytoremediation potential. A mesocosm experiment was designed using Brassica napus as test specie. Soil (RIII) was treated with rabbit manure biochars prepared at 450 °C (BM450) and 600 °C (BM600) at a rate of 10% in mass and incubated for 60 days with or without Brassica napus. Results showed that the combination of BM450 or BM600 with Brassica napus growth decreased the amount of As, Cu, Co, Cr, Se and Pb in the soil. Values of bioaccumulation factor (BAF) for Cd were particularly elevated (>10) in the unamended soil and reached values higher than 1 for other elements, indicating the potential of Brassica napus to accumulate several heavy metals. Translocation Factor (TF) was reduced for Co, Cr, Cd, Cu, Ni, Zn, Pb and As after biochar addition indicating root accumulation of these metals. In all cases, biochar addition increased biomass production. Finally, the addition of BM450 increased GMea index indicating also an improvement on soil quality.

Obtaining edaphic biostimulants/biofertilizers from sewage sludge using fermentative processes. Short-time effects on soil biochemical properties.

In this manuscript, we study the manufacture and effect on soils of different edaphic biostimulants/biofertilizers (BS) obtained from sewage sludge using Bacillus licheniformis as biological tool. These BS consist of different combinations of organic matter, bacteria and enzymes that were subjected to several treatments. These BS were applied in soil in order to observe their influence on the biochemical properties (enzymatic activities and ergosterol content). Dehydrogenase, urease, ß-glucosidase, phosphatase activities and ergosterol content were measured at different incubation days. Only dehydrogenase activity and ergosterol content were significantly stimulated after the application of BS1 and BS4. Rest of the extracellular activities were not stimulated probably because B. licheniformis practically has digested all organic substrates during fermentation process.

Vermicompost Improves Tomato Yield and Quality and the Biochemical Properties of Soils with Different Tomato Planting History in a Greenhouse Study.

A greenhouse pot test was conducted to study the impacts of replacing mineral fertilizer with organic fertilizers for one full growing period on soil fertility, tomato yield and quality using soils with different tomato planting history. Four types of fertilization regimes were compared: (1) conventional fertilizer with urea, (2) chicken manure compost, (3) vermicompost, and (4) no fertilizer. The effects on plant growth, yield and fruit quality and soil properties (including microbial biomass carbon and nitrogen, [Formula: see text]-N, [Formula: see text]-N, soil water-soluble organic carbon, soil pH and electrical conductivity) were investigated in samples collected from the experimental soils at different tomato growth stages. The main results showed that: (1) vermicompost and chicken manure compost more effectively promoted plant growth, including stem diameter and plant height compared with other fertilizer treatments, in all three types of soil; (2) vermicompost improved fruit quality in each type of soil, and increased the sugar/acid ratio, and decreased nitrate concentration in fresh fruit compared with the CK treatment; (3) vermicompost led to greater improvements in fruit yield (74%), vitamin C (47%), and soluble sugar (71%) in soils with no tomato planting history compared with those in soils with long tomato planting history; and (4) vermicompost led to greater improvements in soil quality than chicken manure compost, including higher pH (averaged 7.37 vs. averaged 7.23) and lower soil electrical conductivity (averaged 204.1 vs. averaged 234.6 µS/cm) at the end of experiment in each type of soil. We conclude that vermicompost can be recommended as a fertilizer to improve tomato fruit quality and yield and soil quality, particularly for soils with no tomato planting history.

Determining soil quality in urban agricultural regions by soil enzyme-based index.

Urban agricultural soils are highly variable, and careful selection of sensitive indicators is needed for the assessment of soil quality. This study is proposed to develop an index based on soil enzyme activities for assessing the quality of urban agricultural soils. Top soils were collected from urban agricultural areas of Korea, and soil chemical properties, texture, microbial fatty acids, and enzyme activities were determined. The soils belonged to five textural classes with the highest frequency of sandy loam. There was no clear correlation between the soil chemical properties and soil microbial properties. Principal component analysis (PCA) and factor analysis were applied to microbial groups for identification of microbial community variation in soils. Two soil groups, namely group 1 (G1) and group 2 (G2), based on microbial community abundance were examined by PCA, and those were more prominent in factor analysis. The G1 soils showed higher microbial community abundance than G2 soils. The canonical discriminant analysis was applied to the enzyme activities of sandy loam soil to develop an index, and the index validation was confirmed using the unused soils and published data. The high-quality soils in published literature assigned the high valued index. Microbial fatty acids and soil enzyme activities can be suitable indicators for soil quality evaluation of urban agricultural soils.

Accelerated degradation of PAHs using edaphic biostimulants obtained from sewage sludge and chicken feathers.

We studied in the laboratory the bioremediation effects over a 100-day period of three edaphic biostimulants (BS) obtained from sewage sludge (SS) and from two different types of chicken feathers (CF1 and CF2), in a soil polluted with three polycyclic aromatic hydrocarbons (PAH) (phenanthrene, Phe; pyrene, Py; and benzo(a)pyrene, BaP), at a concentration of 100 mg kg(-1) soil. We determined their effects on enzymatic activities and on soil microbial community. Those BS with larger amounts of proteins and a higher proportion of peptides (<300 daltons), exerted a greater stimulation on the soil biochemical properties and microbial community, possibly because low molecular weight proteins can be easily assimilated by soil microorganisms. The soil dehydrogenase, urease, ß-glucosidase and phosphatase activities and microbial community decreased in PAH-polluted soil. This decrease was more pronounced in soils contaminated with BaP than with Py and Phe. The application of the BS to PAH-polluted soils decreased the inhibition of the soil biological properties, principally at 7 days into the experiment. This decrease was more pronounced in soils contaminated with BaP than with Py and Phe and was higher in polluted soils amended with CF2, followed by SS and CF1, respectively.