Content Of Available Nitrogen Research Articles

Effects of Applying Organic Amendments on Soil Aggregate Structure and Tomato Yield in Facility Agriculture.

Amendment significantly improves soil structure and promotes crop growth. To combat soil degradation and low crop yields in facility agriculture, it is crucial to study the optimal application rate of amendments. This study analyzed the effects of biochar, vermicompost, and mineral-source potassium fulvic acid on the stability of aggregate structure, soil nutrient content, and tomato yield in cambisols, providing a theoretical basis for improving the soil quality of plastic greenhouses in Southern China. A pot experiment on tomato cultivation was carried out in yellow-brown soil in plastic greenhouses. The experiment included eight treatments: 1% biochar (B1); 3% biochar (B3); 5% biochar (B5); 3% vermicompost (V3); 5% vermicompost (V5); 0.1% mineral-source potassium fulvic acid (F1); 0.2% mineral-source potassium fulvic acid (F2); and the control condition without adding soil amendments (CK). The results showed that the biochar and vermicompost treatments effectively reduced soil bulk density and increased total soil porosity. Compared to the control, treatments with soil amendments significantly increased soil pH and had different effects on soil nutrients: F2 showed the most significant improvement in the content of available nitrogen, available phosphorus, and available potassium, with an increase of 133.33%, 834.59%, and 74.34%, respectively; B3 treatment had the highest increase in dissolved organic carbon (DOC), while B5 treatment had the highest organic matter content. Compared to the CK, the particle size of the biochar treatment was mainly 0.053~0.25 mm, while the V3, F1, and F2 mainly occurred with a particle size > 0.25 mm; and V3 has the best aggregate stability. Biochar, vermicompost, and mineral potassium fulvic acid can all promote tomato yield, with the F2 and V3 treatments having a yield increase effect of over 30%. Furthermore, Pearson's correlation analysis showed a highly significant positive correlation between geometric mean diameter (GMD) and mean weight diameter (MWD), water-stable macroaggregate content (R0.25), and a positive correlation between alkaline-dissolved nitrogen, available phosphorus, dissolved organic carbon content, and aggregate stability indicators. Adding 0.2% mineral-source potassium fulvic acid optimizes cambisols' properties, enhances aggregate formation and stability, boosts tomato yield, and shows great application potential.

Effects of Freeze−Thaw Cycles on Available Nitrogen Content in Soils of Different Crops

In order to study the effect of freeze−thaw cycles on the content of available nitrogen in soils of different crops and obtain an in-depth understanding of changes in soil fertility and soil environment in cold regions, a laboratory simulation experiment was conducted with different freeze−thaw times, temperature differences, and periods. The changes in available nitrogen concentrations in the 0–15 cm and 15–30 cm layers of corn, vegetable, and paddy soils were measured by the alkaline-hydrolysis diffusion method. The results were as follows. (1) The freeze−thaw process had significant effects on the available nitrogen content in the three soils. Under the treatment with different numbers of freeze−thaw cycles, the available nitrogen content in the 0–15 cm layers of corn soil, vegetable soil, and paddy soil reached the maximum values at the 8th, 1st, and 3rd freeze−thaw cycle, at 156.92 mg/kg, 479.17 mg/kg and 181.75 mg/kg, respectively; the available nitrogen content decreased slowly after reaching the maximum value. (2) Under the freeze−thaw temperature-difference treatment, the available nitrogen concentration in the 0–15 cm layers of corn soil, vegetable soil, and paddy soil reached the maximum value at a temperature difference of 30 °C, at 147 mg/kg, 476 mg/kg and 172.5 mg/kg, respectively, and the available nitrogen content of the 15–30 cm soil layers changed slightly. (3) Under different freeze−thaw periods, the magnitudes of the changes in soil available nitrogen concentration in 0–15 cm of corn soil and paddy soil were, in descending order, short-term freezing and long-term melting > long-term freezing and long-term melting > short-term freezing and short-term melting > long-term freezing and short-term melting. The soil available nitrogen concentration at different depths in the vegetable soil reached the maximum value under the treatment with long-term freezing and short-term melting. (4) The available nitrogen content of paddy soil under the high-water-content condition was higher than that of paddy soil under the low-water-content condition, and the change in available nitrogen content was more obvious under the high-water-content condition under different freeze−thaw period treatments; the opposite was true for corn soil and vegetable soil. Simulation studies on rapid changes in soil nitrogen content during tests that simulate winter freeze−thaw conditions are important for understanding crop growth, the application of nitrogen fertilizer in spring, and the prevention of surface-water pollution from agricultural runoff.

Microbial electrochemical enhanced composting of sludge and kitchen waste: Electricity generation, composting efficiency and health risk assessment for land use

To realize the energy and resource utilization from organic solid waste, a two-phase microbial desalination cell (TPMDC) was constructed using dewatered sludge and kitchen waste as the anode substrate. The performance of electricity generation and composting efficacy was investigated, along with a comprehensive assessment of the potential health risks associated with the land use of the resulting mixed compost products. Experimental outcomes revealed a maximum open-circuit voltage of 0.893 ± 0.005 V and a maximum volumetric power density of 0.797 ± 0.009 W/m³. After 90 days of composting enhanced by microbial electrochemistry, a significant organic matter removal rate of 31.13 ± 0.44 % was obtained, and the anode substrate electric conductivity was reduced by 30.02 ± 0.04 % based on the anode desalination. Simultaneously, there was an increase in the content of available nitrogen, phosphorus, and potassium, as well as an improvement in the seed germination index. The forms of heavy metals shifted from bioavailable to stable residual states. The non-carcinogenic hazard index (HI) values for heavy metals and polycyclic aromatic hydrocarbons (PAHs) during the land use of compost products were less than 1, and the total carcinogenic risk (TCR) values for heavy metals and PAHs were below the acceptable threshold of 10−4. The occupational population risk of infection from five pathogens was higher than that of the general public, with all risk values ranging from 8.67 × 10−8 to 1, where the highest risk was attributed to occupational exposure to Legionella. These outcomes demonstrated that the mixture of dewatered sludge and kitchen waste was an appropriate anode substrate to enhance TPMDC stability for electricity generation, and its compost products have promising land use suitability and acceptable land use risk, which will provide important guidance for the safe treatment and disposal of organic solid waste.

Suitability of coconut bran and biochar as a composite substrate for lettuce cultivation in aquaponic systems

Growth substrates are essential for aquaponic systems and play an important role in vegetable growth and water quality. In this study, we explored an innovative combination of coconut bran and coconut shell biochar (CSB) as a composite growth substrate for lettuce cultivation in aquaponic systems. The study included the control (100 % coconut bran as the growth substrate) and treatment groups (T1–T5; containing 10 %, 20 %, 30 %, 40 %, and 50 % CSB as the growth substrate, respectively). The substrate properties; lettuce growth performance; and soil enzyme activity, nitrogen content, and abundance of microbial communities in the substrate were analyzed to determine the optimal substrate. Our findings indicated that CSB incorporation significantly altered the properties of the substrate, resulting in increased dry and bulk densities, pH, and water-holding capacity, and decreased electrical conductivity, water-absorption capacity, and porosity. Furthermore, the fresh weight of lettuce was notably increased in the treatment groups. The activities of fluorescein diacetate hydrolase, urease, nitrate reductase, and hydroxylamine reductase initially increased and further decreased, reaching the maximum in the T3 group. Conversely, the activity of nitrite reductase and contents of available nitrogen, nitrate-nitrogen, and ammonium-nitrogen in the substrates initially decreased and further increased, with the minimum values observed in the T3 group. The microbial sequencing results indicated that CSB incorporation significantly increased the microbial diversity and relative abundance of microorganisms associated with nitrogen transformation. Moreover, 30 % CSB incorporation exhibited the greatest effect on lettuce growth, with a 34.5 % and 31.6 % increase in fresh weight compared to the control during the growth and harvest periods, respectively. This study indicated the enormous potential of biochar in the research and development of green technologies for substrate amendment in aquaponic systems.

Responses of Soil C, N, P and Enzyme Activities to Biological Soil Crusts in China: A Meta-Analysis.

Biological soil crusts (BSCs) are often referred to as the "living skin" of arid regions worldwide. Yet, the combined impact of BSCs on soil carbon (C), nitrogen (N), phosphorus (P), and enzyme activities remains not fully understood. This study identified, screened and reviewed 71 out of 2856 literature sources to assess the responses of soil C, N, P and enzyme activity to BSCs through a meta-analysis. The results indicated that BSC presence significantly increased soil C, N, P and soil enzyme activity, and this increasing effect was significantly influenced by the types of BSCs. Results from the overall effect showed that soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), and available phosphorus (AP) increased by 107.88%, 84.52%, 45.43%, 27.46%, and 54.71%, respectively, and four soil enzyme activities (Alkaline Phosphatase, Cellulase, Sucrase, and Urease) increased by 93.65-229.27%. The highest increases in SOC, TN and AN content occurred in the soil covered with lichen crusts and moss crusts, and significant increases in Alkaline Phosphatase and Cellulase were observed in the soil covered with moss crusts and mixed crusts, suggesting that moss crusts can synergistically enhance soil C and N pool and enzyme activity. Additionally, variations in soil C, N, P content, and enzyme activity were observed under different environmental settings, with more pronounced improvements seen in coarse and medium-textured soils compared to fine-textured soils, particularly at a depth of 5 cm from the soil surface. BSCs in desert ecosystems showed more significant increases in SOC, TN, AN, and Alkaline Phosphatase compared to forest and grassland ecosystems. Specifically, BSCs at low altitude (≤500 m) with an annual average rainfall of 0-400 mm and an annual average temperature ≤ 10 °C were the most conducive to improving soil C, N, and P levels. Our results highlight the role of BSCs and their type in increasing soil C, N, P and enzyme activities, with these effects significantly impacted by soil texture, ecosystem type, and climatic conditions. The implications of these findings are crucial for soil enhancement, ecosystem revitalization, windbreak, and sand stabilization efforts in the drylands of China.

Quantitative evaluation and mechanism analysis of soil chemical factors affecting rice yield in saline-sodic paddy fields

Salinization and sodication have become an important abiotic stress affecting soil fertility and crop production in the western of the Songnen Plain in Northeast China. And rice cultivation is considered as one of the most effective biological methods to reclaim saline-sodic soils and ensure food security. However, it is difficult to select the optimal measures to regulate rice growth for increasing yield, because the independent and comprehensive influences of the soil limitation factors on rice yield are not quantitatively evaluated. In this study, the hierarchical partitioning (HP) and the structural equation model (SEM) were used to quantitatively evaluate the influences of salinization parameters, salt ion concentrations and soil nutrients to identify the dominant limitation factors and obstacle mechanism for rice yield. The results showed that soil pH was the key index in salinization parameters, [CO32− + HCO3−] was the key index in salt ion concentrations and available nitrogen (AN) was the key index in soil nutrients to impact rice yield, which independent influences reached 53.7 %, 45.4 % (negative) and 53.2 % (positive), respectively. Soil pH was determined by [CO32− + HCO3−], and the negative effect of alkali stress on rice yield mainly caused by [CO32− + HCO3−] was greater than that of salt stress mainly caused by [Na+] in saline-sodic paddy fields. Among the soil chemical factors, soil pH and AN were the most important explanatory variables of rice yield in saline-sodic paddy fields, which standardized total effects were − 0.32 and 0.40, respectively. Furthermore, the AN showed a more significant negative correlation with soil pH and a higher yield-increasing potential in severe saline-sodic soils (9 ≤ pH < 10) than that in moderate saline-sodic soils (8 ≤ pH < 9). Therefore, decreasing [CO32− + HCO3−] and increasing the content of AN are key to improve rice yield in saline-sodic paddy fields.

Effects of Intercropping and Nitrogen Application on Soil Fertility and Microbial Communities in Peanut Rhizosphere Soil

The intercropping of peanuts and sugarcane is a sustainable planting model that deserves in-depth research. For this study, two variables, i.e., intercropping status (peanut monocropping or sugarcane/peanut intercropping) and the level of nitrogen fertilization (low, medium, or high), were evaluated to analyze the effects of intercropping and nitrogen application on soil fertility and microbial communities in peanut rhizosphere soil. These analyses revealed that higher nitrogen application led to increased total nitrogen (TN), available nitrogen (AN), and soil organic matter (OM) levels in rhizosphere soil for both monocropped and intercropped peanuts, with a decrease in pH. Monocropped peanuts had higher TN, total phosphorus (TP), and total potassium (TK) levels compared to intercropped peanuts at the same nitrogen level but lower AN content and pH levels. The diversity of microbial communities in the rhizosphere soil of intercropped peanuts was significantly higher than that of monocropped peanuts under high levels of nitrogen fertilizer application. Higher levels of Gemmatimonadetes abundance were observed in intercropping rhizosphere soil, compared to that associated with peanut monocropping under low, middle, and high levels of nitrogen fertilizer application, whereas the opposite trend was observed for Chloroflexi abundance. Nitrospira abundance levels rose gradually in the monocropping treatment group, whereas the opposite trend was evident under intercropping conditions. Further analyses of nitrogen cycle-related genes demonstrated higher levels of nitrogen conversion cycle activity in intercropping peanut rhizosphere soil under low nitrogen levels, whereas nitrogen transformation cycle activity levels were higher in monocropping peanut rhizosphere soil under high levels of nitrogen amendment. It can be concluded that intercropping and nitrogen fertilizer application change the physical and chemical properties of soil, thus affecting the diversity and function of soil microbial communities in the peanut rhizosphere. These results offer a theoretical foundation for more efficient sugarcane/peanut intercropping systems.

Tobacco/Salvia miltiorrhiza Intercropping Improves Soil Quality and Increases Total Production Value

Unreasonable cultivation methods and management measures have led to widespread obstacles in tobacco continuous cropping in planting areas, resulting in reduced tobacco yield and soil degradation. Therefore, intercropping tobacco with other crops is an effective strategy to improve continuous cropping barriers. In this study, flue-cured tobacco NC102 and conventional planting varieties of Salvia miltiorrhiza were used as materials, and four treatments of flue-cured tobacco monoculture (CK), flue-cured tobacco, and Salvia miltiorrhiza at a ratio of 1:1 (TS11), 2:2 (TS22), and 2:3 (TS23), respectively, were set up to study their effects on soil microorganisms, physical and chemical properties, and yield and quality of flue-cured tobacco. The results showed that intercropping Salvia miltiorrhiza increased the number of soil bacteria and actinomycetes, decreased the number of fungi, and increased the activity of urease and sucrase. The content of available nitrogen and available phosphorus in intercropping Salvia miltiorrhiza soil was significantly higher than that of the flue-cured tobacco monoculture, while the content of available potassium was lower than that of the flue-cured tobacco monoculture. The soil environment was more conducive to the growth of flue-cured tobacco. Compared with the flue-cured tobacco monoculture, the proportion of superior tobacco in intercropping Salvia miltiorrhiza increased by 2.2–3.4%, and the ratio of potassium to chlorine in leaves of different parts of flue-cured tobacco increased by 12.3–75.0%. The content of total sugar and soluble sugar in middle and upper leaves of intercropping flue-cured tobacco was higher than that of the flue-cured tobacco monoculture, which improved the quality of flue-cured tobacco. From the analysis of the chemical composition of tobacco leaves, TS11 (flue-cured tobacco and Salvia miltiorrhiza intercropping row ratio of 1:1) had the best treatment effect, potassium content, total sugar, reducing sugar content, and potassium chloride ratio of flue-cured tobacco were the highest, the chlorine content was the lowest, and the quality was better than other treatments. From the analysis of total output value, the total output value of TS22 (flue-cured tobacco and Salvia miltiorrhiza intercropping row ratio of 2:2) was higher than that of other intercropping treatments. In 2018 and 2019, the total output value increased by 21.3% and 22.4%, respectively, compared with the flue-cured tobacco monoculture. The intercropping advantage was obvious, and the treatment effect was the best.

Effect of Inorganic Fertilizer, Farmyard Manure and Biofertilizer on Physical and Chemical Properties of Soil and System Yield of Maize – Wheat Rotation in Mollisol

A field experiment was conducted during the Kharif and Rabi seasons of 2020-21 and 2021-22 at the Norman E. Borlaug Crop Research Centre, G.B.P.U.A &amp; T., Pantnagar. Randomized block design was followed with 11 treatments and 3 replications. The main objective was to assess the influence of fertilizer and farmyard manure application, with or without Azotobacter and zinc, on crop yield and soil properties in a maize-wheat crop rotation. The data demonstrated that application of 100% RDF + FYM 5 t ha-1, resulted in a significantly higher system yield of 12,137 kg ha-1. Intercropping of cowpea with maize along with the application of FYM 10 t ha-1 showed the lowest bulk density in both surface (1.38 Mg m-3) and sub-surface (1.49 Mg m-3) soil and also it led to a reduction in the soil pH and EC. Additionally, hydraulic conductivity was higher in organic treatments, specifically in T6. However, the application of 100% RDF + FYM 5 t ha-1 resulted in the maximum retention of organic carbon (1.06% and 0.71%) as well as higher content of available nitrogen (185.11 and 175.95 kg ha-1), phosphorus (36.17 and 31.65 kg ha-1) and potassium (147.90 and 120.68kg ha-1) in surface and subsurface soil, respectively. The study suggests that the application of 100% RDF + FYM 5 t ha-1 contributes to improved soil fertility and sustainable crop yields.

ВИРОЩУВАННЯ СОРГО ЗЕРНОВОГО НА КИСЛИХ ГРУНТАХ В УМОВАХ ЗАКАРПАТСЬКОЇ ОБЛАСТІ

The work aims to conduct production field research to determine the potential yield level of grain sorghum on acidic soils, as well as work out the generally accepted basic elements of cultivation technology with its subsequent cultivation in the Zakarpattia region. Materials and methods. In 2023, the production range for growing grain sorghum at Karpatiagroproduct LLC was located in the lowland zone of Uzhgorod district, Zakarpattia region. The article describes agrotechnical operations related to soil cultivation, application of fertilizers and plant protection products that were used in the farm, the main of which was the application of mineral fertilizer diammonium phosphate (NP 18:46) at the rate of 160 kg during sowing. The sowing rate was 165,000 seeds per hectare with a row width of 37 sm. Results. Sorghum is not picky about soils, so it can grow on both clay and sandy soils. The landfill where sorghum was grown is characterized by a low content of mobile phosphorus (6.33 mg/kg), a very low content of total nitrogen (N-NO3- + N-NH4+ – 8.92 mg/kg). According to the degree of acidity, the soil belongs to a very acidic soil (the hydrogen index of the saline extract of the soil is 4.08). In the economic conditions of 2023, the yield of sorghum grain hybrid Iceberg was 4.4 t/ha, which is 1.0 t/ha more than the average yield of sorghum in Ukraine over the past 10 years. Taking into account the genetic potential of this crop and the sufficient level of moisture supply of the territory, the level of the sorghum harvest should be twice as large. Because sorghum is not recommended to be grown on acidic, waterlogged soils with a close occurrence of groundwater, the underachieved level of the harvest to some extent may be related to this. In addition, the low content of mobile phosphorus and very low content of available nitrogen, which is characteristic of acidic clay soils, to some extent negatively affected the processes of crop yield formation. Conclusions. The obtained sorghum yield at Karpatiagroproduct LLC - 4.4 t/ha is lower than the average yield in Italy, by 2.6 t/ha, and in France - by 0.6 t/ha. However, it was in the territory of Ukraine that the record yield of sorghum in the world was obtained - 14.43 t/ha, which testifies to the high potential of grain sorghum and the unlimited potential of scientific and industrial research to reveal the genetic expression of this crop. Keywords: grain sorghum, yield, soil pH, «Iceberg» hybrid, agricultural technology.

Spatiotemporal heterogeneity of soil available nitrogen during freeze–thaw cycles in a watershed: A 3‐year investigation

AbstractThe spatial pattern of soil available nitrogen (AN) is the key reference for farmland fertilization however, it is still unclear how freeze–thaw cycles (FTC) altered the spatiotemporal heterogeneity of AN at the watershed scale. In this study, the geostatistical, traditional analysis and structural equation models were used to detect how topography, land management, and soil properties influence the spatiotemporal heterogeneity of AN in both before‐ and after FTCs of Mollisols of a watershed in Northeast China for three consecutive years. The results showed that AN decreased in &gt;88% of areas of the watershed after FTCs, and the mean value significantly decreased by &gt;7.6% (&gt;10.4 mg kg−1) in 0–20 cm soil depth during 2016–2017 years and 2017–2018 years. The AN distribution, especially in the surface soil layer, tended to be aggregated after FTCs. The AN decreased in the areas near the areas of top slope position, while it tended to increase in areas of downslope position covered by forest although the total N decreased here after FTCs. The AN‐change (ANbefore FTCs minus ANafter FTCs) influenced by land use types was greater than slope steepness. The slope aspect as the key factor combined with slope steepness, slope position, and previous crops influenced the spatiotemporal heterogeneity of AN‐change after FTCs. The higher content of AN before FTCs accelerated more N loss during FTCs, and this process was mainly influenced by soil pH, nitrogen (N), and phosphorus. The N loss (5.7%) did not significantly alter the AN‐change after FTCs in the watershed. Generally, the spatial heterogeneity of AN‐change was mainly influenced by topography, land management, and soil properties (before FTCs) during FTCs in the watershed. In order to sustain a high level of AN, the mediation of N transformation and both vertical‐ and horizontal migration, caused by the dynamics of soil water potential and snowmelt erosion should be considered during FTCs.

Impact of typical land use type on the stability and content of carbon and nitrogen of soil aggregates in western Hubei

AbstractIn order to investigate the characteristics of soil structural stability and the factors influencing it under typical land use types in the karst region of western Hubei, soil samples were collected from five land use types (natural mixed forest [NF], cypress forest [CF], stone dike terrace [ST], stone dike forest [SF], and abandoned land [AL]) in Xialaoxi to analyze the particle size distribution of aggregates, structural stability, and the distribution characteristics of carbon, nitrogen, and extracellular enzyme contents. The results showed that the aggregates of NF, CF, SF, and AL were dominated by &gt;2‐mm aggregates, while ST showed mostly 2–0.25‐mm aggregates. The mean weight diameter (EMWD) and the geometric mean diameter (EGMD) of mechanical aggregates showed a trend of CF &gt; NF &gt; SF &gt; AL &gt; ST, whereas the erodibility factor K showed an opposite trend. The total organic carbon (TOC), labile organic carbon (LOC), and total nitrogen (TN) contents of aggregates of each particle size were significantly higher in NF and CF than in ST and AL under the five land types. The content of available nitrogen (AN) was highest in NF and ST. The content of carbon and nitrogen and extracellular hydrolases (β‐glucosidase [BG], cellulose disaccharide hydrolase [CBH], β‐N‐acetyl‐aminoglucosidase [NAG], and leucine aminopeptidase [LAP]) in soil aggregates were mainly concentrated in &lt;0.25–0.053‐mm aggregates. The variation in carbon and nitrogen abundance of each particle size agglomerate mainly originated from the LAP content of that particle size agglomerate and showed significant correlation. The partial least squares path models (PLS‐PM) showed that the main influences on the stability of soil aggregates in small watersheds were land use types, soil physical properties, carbon and nitrogen abundance, and extracellular enzyme activity. In conclusion, the structural stability of soil aggregates in Xialaoxi watershed is the result of the interaction between human disturbance and soil nutrient self‐cycling. In general, NF and CF have better soil aggregate stability and are conducive to soil carbon and nitrogen accumulation, whereas for later development and management of SF, ST, and AL sample plots, scientific cultivation means should be adopted, and attention should be paid to long‐term carbon and nitrogen accumulation and conservation.

Beneficial and biocontrol effects of Trichoderma atroviride, a dominant species in white birch rhizosphere soil.

White birch (Betula platyphylla Suk.) is a typical pioneer tree species that is important in forest restoration in northern China, Japan, and Korea. In the present study, 37 isolates were obtained from B. platyphylla rhizosphere soils in Heilongjiang Province; they were identified as T. pleuroticola (3 isolates), T. virens (2 isolates), T. hamatum (8 isolates), T. atroviride (21 isolates, dominant species) and T. asperelloides (3 isolates). Stress tolerance tests (salt, alkali, and nutritional stress that simulated saline alkali or barren soil) and confrontation assays (with four pathogens) were performed to determine which isolates had good biocontrol ability in barren soil; the results show that T. atroviride was outstanding. Then, in order to determine the effect of T. atroviride on plants and soil, Gynura cusimbua seeds were sown and treated with a T. atroviride spore suspension, as was unsown soil. The seedlings treated using T. atroviride had significantly greater height, stem diameter, soluble protein content, soluble sugar content, and malonaldehyde (MDA) content and their catalase (CAT) activity was also significantly increased. In addition, when the plants were inoculated with Alternaria alternata, the plants treated using T. atroviride had stronger CAT activity, significantly higher soluble protein content and soluble sugar content, and significantly lower MDA content, which indicates stronger resistance and less injury caused by the pathogen. In addition, T. atroviride not only increased the content of available nitrogen and available phosphorus in the soil, but also promoted G. cusimbua seedlings' absorption of available nitrogen and available phosphorus. Thus, the characteristics of T. atroviride may make it the main factor that helps B. platyphylla colonise cut-over lands. T. atroviride, a promising biocontrol candidate, can be used in agriculture and forestry.

Degradation of betaine aldehyde dehydrogenase transgenic maize BZ-136 straw and its effects on soil nutrients and fungal community.

The development of salt-alkali tolerant genetically modified crops represents an important approach to increase grain production in saline-alkali soils. However, there is a paucity of research on the impact of such genetically modified crops on soil microbial diversity. This study aims to investigate the straw degradation of betaine aldehyde dehydrogenase (BADH) transgenic maize BZ-136 and its effects on soil chemical properties, fungal community composition, community diversity and ecological function compared to non-transgenic maize Zheng58 straw. The degradation experiments of BZ-136 straw were carried out under a simulated burying condition with saline-alkali soil for 210 days. The results showed that the degradation rate of C and N of BZ-136 straw was significantly faster than that of Zheng58 in the early stage (p < 0.05). Compared to Zheng58, the straw degradation of BZ-136 increased the soil available nitrogen (AN), total phosphorus (TP), and available phosphorus (AP) in the early stage (p < 0.05). The AN content of soil with BZ-136 straw was 18.16 and 12.86% higher than that of soil with Zheng58 at day 60 and 120 (p < 0.05). The TP content of soil with BZ-136 was higher 20.9 and 20.59% than that with Zheng58 at day 30 and 90 (p < 0.05). The AP content of soil with BZ-136 was 53.44% higher than that with Zheng58 at day 60 (p < 0.05). The straw degradation of BZ-136 increased the OTU number of soil fungal community by 127 (p < 0.05) at day 60, and increased Chao1 and Shannon index at day 60 and 180 (p < 0.05). The degradation rate of C and N in BZ-136 straw was higher than that in Zheng58 at early stage, which led to the phased increase of soil AN and TP contents, and the obvious changes of relative abundances (RA) of some genera and guilds. These findings are important as they provide insight into the potential benefits of BADH transgenic crops in upgrading the soil fertility and the fungal community diversity.

Effects of coal-derived compound fertilizers on soil bacterial community structure in coal mining subsidence areas.

The land damaged by coal mining can be recovered to healthy condition through various reclamation methods. Fertilization is one of the effective methods to improve soil fertility and microbial activity. However, the effects of coal-derived compound fertilizers (SH) on bacterial communities in coal mining subsidence areas still remain unclear. Here, we studied the effects on the nutrient characteristics and bacterial communities in fertilizer-reclaimed soil (CK, without fertilizer; CF, common compound fertilizers; SH, coal-derived compound fertilizers) in coal mining subsidence areas and we applied SH with four different nitrogen application rates (90, 135, 180, and 225 kg/hm2). The results showed that the application of SH significantly increased the contents of available nitrogen (AN), available phosphorus (AP), available potassium (AK), total phosphorus (TP) and soil organic matter (SOM) compared with CK, as well as the bacterial richness (Chao1) and diversity (Shannon) in reclaimed soil that increased first and then decreased with the increase of nitrogen application. Under the same nitrogen application rate (135 kg/hm2), the nutrient content, Chao1 and Shannon of SH2 treatments were higher than those of CF treatment. Meanwhile, SH increased the relative abundance of Proteobacteria, Actinobacteria and Gemmatimonadetes. LEfSe analysis indicated that the taxa of Acidobacteria and Actinobacteria were significantly improved under SH treatments. Canonical correspondence analysis (CCA) and Variance partitioning analysis (VPA) showed that SOM was the most important factor affecting the change of bacterial community structure in reclaimed soil. In conclusion, application of SH can not only increase nutrient content and bacterial diversity of reclaimed soil, but also improve bacterial community structure by increasing bacterial abundance.

Core microbiota of wheat rhizosphere under Upper Indo-Gangetic plains and their response to soil physicochemical properties.

Wheat is widely cultivated in the Indo-Gangetic plains of India and forms the major staple food in the region. Understanding microbial community structure in wheat rhizosphere along the Indo-Gangetic plain and their association with soil properties can be an important base for developing strategies for microbial formulations. In the present study, an attempt was made to identify the core microbiota of wheat rhizosphere through a culture-independent approach. Rhizospheric soil samples were collected from 20 different sites along the upper Indo-Gangetic plains and their bacterial community composition was analyzed based on sequencing of the V3-V4 region of the 16S rRNA gene. Diversity analysis has shown significant variation in bacterial diversity among the sites. The taxonomic profile identified Proteobacteria, Chloroflexi, Actinobacteria, Bacteroidetes, Acidobacteria, Gemmatimonadetes, Planctomycetes, Verrucomicrobia, Firmicutes, and Cyanobacteria as the most dominant phyla in the wheat rhizosphere in the region. Core microbiota analysis revealed 188 taxa as core microbiota of wheat rhizosphere with eight genera recording more than 0.5% relative abundance. The order of most abundant genera in the core microbiota is Roseiflexus> Flavobacterium> Gemmatimonas> Haliangium> Iamia> Flavisolibacter> Ohtaekwangia> Herpetosiphon. Flavobacterium, Thermomonas, Massilia, Unclassified Rhizobiaceae, and Unclassified Crenarchaeota were identified as keystone taxa of the wheat rhizosphere. Correlation studies revealed, pH, organic carbon content, and contents of available nitrogen, phosphorus, and iron as the major factors driving bacterial diversity in the wheat rhizosphere. Redundancy analysis has shown the impact of different soil properties on the relative abundance of different genera of the core microbiota. The results of the present study can be used as a prelude to be developing microbial formulations based on core microbiota.

Transcriptomics Combined with Photosynthetic Physiology and Leaf Structure Analysis Revealed Increased Sugarcane Yield by Fenlong-Ridging

Fenlong-ridging (FL) is a new type of conservation tillage. In many crops, FL increases crop yield and quality; however, the cytology and molecular mechanisms of crops under FL is not completely understood. This study investigated soil physical and chemical properties under FL and conventional tillage (CK) during 2018–2019 (plant cane) and 2019–2022 (first stubble), and analyzed the agronomic trait, physiology, leaf anatomical structure, and gene expression related to photosynthesis between FL and CK of sugarcane (Guitang 42). Soil bulk density significantly increased, and soil porosity, water storage, and content of available nitrogen and phosphorus under FL were significantly higher than those under CK. Plant height, stem diameter, single stem weight, effective stem number and yield significantly increased under FL compared to under CK. Sugar content significantly increased in plant cane under FL. Chlorophyll content and the photosynthetic rate increased, with significantly higher activity of photosynthetic enzymes including NADP-malate dehydrogenase (NADP-MDH), phosphoenolpyruvate carboxylase (PEPC), and ribulose-1,5-bisphosphate carboxylase (RuBPC) under FL compared to CK. Fenlong-ridging cytology results showed that the mesophyll cells were large and arranged well, the Kranz anatomy was noticeable, and there were a high number of large chloroplasts in mesophyll cell and in the vascular bundle sheath. Furthermore, the bundle sheath in FL was larger than that in CK. Transcriptomics results showed that 19,357 differentially genes (DEGs) were up-regulated and 28,349 DEGs were down-regulated in sugarcane leaves under FL vs. CK. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that abundant DEGs were enriched in photosynthesis, photosynthesis-antenna protein, carotenoid biosynthesis, and other pathways associated with photosynthesis. Most expression was up-regulated, thus, facilitating photosynthesis regulation. Quantitative real-time polymerase chain reaction analysis revealed the up-regulation of genes related to photosynthesis (PsaH and PsbS) under FL. Overall, this study provides insights into the role of FL in increased sugarcane yield by integrating physiology, cytology, and proteomics analysis. These findings could be used to further improve its application and promotion.

Saline-Alkali Soil Property Improved by the Synergistic Effects of Priestia aryabhattai JL-5, Staphylococcus pseudoxylosus XW-4, Leymus chinensis and Soil Microbiota.

Two saline-alkali-tolerant bacterial strains, Priestia aryabhattai JL-5 and Staphylococcus pseudoxylosus XW-4, were isolated, with high capabilities of hydrolyzing phosphate and producing cellulase, respectively. The molecular mechanisms regulating the saline-alkali tolerance in the strain JL-5 were further investigated using transcriptome analysis. The contents of lactic acid and proline and the enzymatic activity of glutamine synthetase in the strain JL-5 were significantly increased. The properties of saline-alkali soils were significantly improved by the enhanced growth of the indicator plant Leymus chinensis under the combined applications of the strains JL-5 and XW-4 mixed with corn straw. The contents of catalase, peroxidase, superoxide dismutase and proline of L. chinensis were significantly increased, and the content of malondialdehyde was significantly decreased in the combined treatment of both bacterial strains. The contents of available nitrogen, phosphorus and potassium and organic matters in the soil treated with both strains were significantly increased, as well as the diversity and abundance of the soil microbiota. Our study evidently demonstrated the synergistic effects of the strains JL-5 and XW-4, indicator plants and the local microbiota in terms of improving the saline-alkali soil properties, providing strong experimental evidence to support the commercial development of the combined application of both strains to improve the properties of saline-alkali soils.

The Changes in Rhizosphere Metabolome and Microbiota Are the Main Direct Obstacles to Continuous Cropping in Tobacco (Nicotiana tabacum L.)

Continuous cropping obstacles (CC), typical of negative plant–soil feedback, have become a non-negligible constraint to the development of agriculture. In order to investigate the main direct drivers influencing the formation of CC soils from the rhizosphere of CC, tobacco fields were collected and their physicochemical properties, microbial community, and metabolomics were measured and analyzed. We also built a mixed linear model to evaluate the impact of these factors on CC. The results suggested that the pH, available potassium (AK), and zinc (Zn) were significantly higher in CC than in normal tobacco (NOR). However, the content of available nitrogen (AN) decreased significantly. Alpha diversity of the bacterial community was significantly reduced. Bacterial community structure also varied significantly in CC. The study identified an ecological cluster with a significant negative correlation with the above-ground biomass of plants. In this cluster, the pathogenic microbiome increased and the beneficial microbiome decreased. The orthogonal partial least squares discriminant analysis (OPLS-DA) indicated clear variations in the metabolomic profiles of the rhizosphere soil between the CC and the NOR. There was an accumulation of toxic compounds and a decrease of beneficial compounds in rhizosphere soils with CC. The mixed linear model showed that only microbiome and metabolites, rather than the soil’s physicochemical properties, significantly affected plant above-ground biomass. According to the model’s standardized coefficients, metabolites contributed more to the continuous crop obstacles than the microbial community. The soil’s physicochemical properties do not directly cause the emergence of CC. The allelochemicals and microbial community are the main direct obstacles to continuous cropping in tobacco, and allelochemicals contribute more than the microbial community.

The characteristic difference between non-drilosphere and drilosphere-aged biochar: Revealing that earthworms accelerate the aging of biochar

Numerous researches have been conducted on the effects of biotic and abiotic-induced aging on the physicochemical characteristics and functions of biochar; however, the impacts of earthworm-induced aging on biochar have not been reported. Hence, we conducted a microscopic experiment simulating a ‘drilosphere’ to explore the influence of earthworm activity on the natural aging of rice husk biochar (RHBC) through the difference in biochar characteristics after aging in drilosphere and non-drilosphere. The earthworm activity increases the available nitrogen (AN) and dissolved organic matter (DOM) contents of aged RHBC and changes its composition. The increase of DOM and AN content may recruit more microorganisms to colonize biochar and accelerate the biological oxidation of biochar. Furthermore, earthworm activity significantly increased the contents of oxygen (O) and O-containing functional groups in the aged RHBC and decreased the stability (aromaticity) of the aged RHBC, suggesting that the earthworm activity accelerates the natural aging of biochar. Earthworm feeding promotes physical damage to biochar. Besides, the earthworm activity decreased the pH, hydrophilicity and specific surface area (SSA) of aged RHBC but enhanced the adsorption capacity of aged RHBC for heavy metals. The higher content of O-containing functional groups on the surface of drilosphere-aged RHBC was the main reason for its higher adsorption performance. Earthworm feeding promotes physical damage to biochar. These results indicate that earthworm activity can accelerate the natural aging of biochar and alter its physicochemical characteristics and functions. This study illustrates how biochar characteristics change in earthworm-soil systems, which will help scientifically evaluate the long-term effectiveness of biochar.