Increased Soil Microbial Biomass Research Articles

Biochar improves soil quality and wheat yield in saline-alkali soils beyond organic fertilizer in a 3-year field trial.

The objective of this study was to examine the effects of biochar compared to organic fertilizer on soil quality and wheat yield in the saline-alkaline lands. A 3-year field trial was conducted on moderately saline-alkaline land in the Yellow River Delta region (YRD) with six treatments: biochar (B1: 5 t, B2: 10 t, B3: 20 t ha-1year-1) and organic fertilizer (OF1: 5 t, OF2: 7.5 t ha-1year-1) as well as control (CK). The results showed that both biochar and organic fertilizer increased total organic carbon (TOC), total nitrogen (TN), NH4+-N, and NO3--N, and reduced pH, thereby increasing soil microbial biomass carbon (MBC) and nitrogen (MBN), MBC/TOC ratio, and MBN/TN ratio, but organic fertilizer increased soil nutrients and microbial biomass better than biochar. Correlation analysis revealed that soil water content (SWC), soil salt content (SSC), and Na+ were the most important factors influencing wheat yield. When compared to CK, the SSC and Na+ decreased by 5.55-7.52% and 3.86-9.39%, respectively, and SWC increased by 5.14-5.62% in the biochar treatment, while they increased by 1.07-10.19%, 1.08-7.58%, and 2.96-3.84% in the organic fertilizer treatment, respectively. Accordingly, wheat yield of biochar treatment was 0.90-14.71% higher than that of organic fertilizer treatment (4.49-4.80 t ha-1) and CK (4.47 t ha-1). Collectively, B2 had the lowest SSC and Na+ and the highest yield and was significantly better than the organic fertilizer treatment, as well as efficiently increasing soil nutrients and microbial biomass, suggesting that it may be a better agricultural practice for improving soil quality and increasing wheat yield in the YRD.

Effects of Chemical Fertilizer Reduction Combined with Straw Application on Diazotrophic Communities in a Double Rice Cropping System

Based on a three-year field experiment, the effects of reduced chemical fertilizer combined with straw application on paddy yield, soil fertility properties, and community structure of diazotrophs in a double-rice cropping field three years after straw application were examined. Three treatments were applied:conventional fertilizer application (CF), chemical fertilizer reduction combined with a low straw application rate (CFLS, 3 t·hm-2), and a high straw application rate (CFHS, 6 t·hm-2). The results showed that CFLS and CFHS did not significantly reduce rice grain yield (P>0.05); significantly neutralized soil acidification; increased soil microbial biomass carbon and nitrogen, dissolved organic carbon, and organic carbon content (P<0.05); and significantly reduced soil redox potential, ammonium nitrogen, and nitrate nitrogen contents (P<0.05). This was more conducive to improve soil nitrogen use efficiency. Compared with those under the CF treatment, the natural nitrogen fixation functional communities of CFLS and CFHS increased the Shannon, PD, and Evenness indexes (P<0.05) due to the improvement of conditions such as the increase in soil carbon storage and the decrease in acidification degree. The relative abundance of microbial communities with nitrogen fixation, carbon fixation, and plant growth promotion functions such as Ferrigenium, Sulfurivermis, Methylomonas, Methylovulum, Ectothiorhodospira, and Nostoc increased significantly (P<0.05). In conclusion, the reduction in chemical fertilizer combined with 3 t·hm-2 and 6 t·hm-2 straw application was an effective measure to improve the community structure of soil diazotrophs and the potential of soil nitrogen fixation.

Can multi-cropping affect soil microbial stoichiometry and functional diversity, decreasing potential soil-borne pathogens? A study on European organic vegetable cropping systems.

Crop diversification in spatial and temporal patterns can optimize the synchronization of nutrients plant demand and availability in soils, as plant diversity and soil microbial communities are the main drivers of biogeochemical C and nutrient cycling. The introduction of multi-cropping in organic vegetable production can represent a key strategy to ensure efficient complementation mediated by soil microbiota, including beneficial mycorrhizal fungi. This study shows the effect of the introduction of multi-cropping in five European organic vegetable systems (South-West: Italy; North-West: Denmark and Belgium; North-East: Finland and Latvia) on: (i) soil physicochemical parameters; (ii) soil microbial biomass stoichiometry; (iii) crop root mycorrhization; (iv) bacterial and fungal diversity and composition in crop rhizosphere; (v) relative abundance of selected fungal pathogens species. In each site, three cropping systems were considered: (1) crop 1—monocropping; (2) crop 2—monocropping; (3) crop 1—crop 2—intercropping or strip cropping. Results showed that, just before harvest, multi-cropping can increase soil microbial biomass amount and shape microbial community toward a predominance of some bacteria or fungi phyla, in the function of soil nutrient availability. We mainly observed a selection effect of crop type on rhizosphere microbiota. Particularly, Bacteroidetes and Mortierellomycota relative abundances in rhizosphere soil resulted in suitable ecological indicators of the positive effect of plant diversity in field, the first ones attesting an improved C and P cycles in soil and the second ones a reduced soil pathogens' pressure. Plant diversity also increased the root mycorrhizal colonization between the intercropped crops that, when properly selected, can also reduce the relative abundance of potential soil-borne pathogens, with a positive effect on crop productivity in long term.

Nitrogen Fertilization Increases Soil Microbial Biomass and Alters Microbial Composition Especially Under Low Soil Water Availability.

Soil microbial biomass and composition are affected by resource supply and water availability. However, the response of soil microbial communities to nitrogen fertilization under different water availability conditions is unclear. Therefore, this study conducted a 6-year pot experiment comprising five watering regimes (40%, 50%, 60%, 80%, and 100% of field capacity (FC)) and three nitrogen fertilization levels (NH4NO3 solution; 0 [N0], 20 [N1], and 40 [N2] g N m-2year-1) to investigate soil microbial biomass, composition, and properties. The results indicated that soil microbial biomass and composition were more strongly affected by nitrogen fertilization compared with water regime. Nitrogen fertilization increased soil microbial biomass and altered soil microbial community composition, especially under low soil water availability. Soil microbial biomass was positively linearly associated with soil water regimes under N0, whereas it responded polynomially to soil water regimes under N1 and N2. The maximal soil microbial biomass was observed at FC80 for N1 and FC60 for N2. Furthermore, the biomass of soil microbial groups with high nitrogen and carbon acquisition ability as well as the enzyme activities of carbon and nitrogen cycling (β-1,4-glucosidase and β-1,4-N-acetyl-glucosaminidase, respectively) were stimulated by nitrogen fertilization. Soil microbial biomass was affected directly by nitrogen fertilization and indirectly by nitrogen and water regimes, via altering soil pH, dissolved inorganic nitrogen (NH4+-N and NO3--N) concentration, and soil organic carbon concentration. This study provides new insights into the effect of interaction between soil nitrogen and water availabilities on soil microbial biomass, composition, and its underlying mechanism.

Compost amendment maintains soil structure and carbon storage by increasing available carbon and microbial biomass in agricultural soil – A six-year field study

Soil organic amendments in agricultural production can benefit crop production and a wide range of soil properties, including soil aggregation. Soil aggregate formation is largely driven by microbial activities, and can in-turn influence microbial communities by generating distinct microbial habitats, as well as associated impacts on water and nutrient dynamics. We investigated the long-term effects of two fertilizer management strategies (poultry manure compost vs. mineral fertilizer) and biochar amendment (0 vs. 10 t ha−1 walnut shell biochar, 900 °C pyrolysis temperature, by-product of gasification) on soil aggregation, soil organic C, and microbial community dynamics in water-stable aggregate fractions in corn-tomato rotations. Using wet-sieving, soils (0–15 cm) were divided into four size fractions: large macroaggregates (2000–8000 μm), small macroaggregates (250–2000 μm), microaggregates (53–250 μm) and silt and clay (<53 μm) for calculation of mean weight diameter in both 2014 and 2018. The total C and microbial community composition and abundance within each fraction were evaluated in 2018. Across all treatments, six years of continuous compost application maintained soil aggregate stability and C storage by increasing soil microbial biomass and associated dissolved organic C. Bacterial and fungal populations under compost treatments were significantly higher than under mineral fertilizer treatments based on 16S rRNA gene copy number and internal transcribed spacer (ITS) abundance, which likely contributed to the formation and maintenance of macroaggregates in compost treatments. Interestingly, continuous application of manure compost may increase microbial available C sources by increasing the abundance of bacteria with the potential to degrade aromatic C as predicted from 16S sequences. Soil under the mineral fertilizer treatment showed decreases in the proportion of large macroaggregates, bulk soil C, and aggregate-associated C storage compared to the compost treatment. The application of highly recalcitrant walnut shell biochar had limited long-term impacts on soil aggregation and C dynamics, likely due to its lack of microbially-available C and limited interaction with the soil environment. Our results indicate that continuous compost inputs maintained soil structure and associated physical stabilization of SOM by enlarging soil microbial available C pool, higher soil microbial biomass, and increasing aggregate formation. The soil aggregate structure, in-turn, generated diverse habitats and altered soil microbial communities. Compost inputs, in addition to or in partial replacement of mineral fertilizer inputs, can provide valuable microbial-driven ecosystem services, such as carbon storage and soil structure, while still providing fertility for crop growth.

Organo-mineral complexes alter bacterial composition and induce carbon and nitrogen cycling in the rhizosphere.

It is widely thought that organo-mineral complexes (OMCs) stabilize organic matter via mineral adsorption. Recent studies have demonstrated that root exudates can activate OMCs, but the influence of OMCs on plant rhizosphere, which is among the most active areas for microbes, has not been thoroughly researched. In this study, a pot experiment using Brassica napus was conducted to investigate the effects of OMCs on plant rhizosphere. The result showed that OMC addition significantly promoted the growth of B. napus compared to the prevalent fertilization (PF, chemical fertilizer + chicken compost) treatment. Specifically, OMC addition increased the relative abundance (RA) of nitrogen-fixing bacteria and the bacterial α-diversity, and the operational taxonomic unit (OTU) group with RA > 0.5% in the OMC-treated rhizosphere was the result of a deterministic assembly process with homogeneous selection. Gene abundance related to nitrogen cycling and the soil chemical analysis demonstrated that the OMC-altered bacterial community induced nitrogen fixation and converted nitrate to ammonium. The upregulated carbon sequestration pathway genes and the increased soil microbial biomass carbon (23.68%) demonstrated that the bacterial-induced carbon storage in the rhizosphere was activated. This study shows that the addition of OMCs can influence the biogeochemical carbon and nitrogen cycling via regulating microorganisms in the rhizosphere. The findings provide fresh insights into the effects of OMCs on the biogeochemical cycling of important elements and suggest a promising strategy for improving soil productivity.

Effects of Byproduct Amendments and Nitrogen on Carbon Mineralization and Soil Enzyme Activities in Acidic Brown Soil from Jiaodong Peninsula of China

ABSTRACT It has been proposed strategy that acidic soil quality can be improved by addition of alkaline byproduct amendments containing silicon, calcium, magnesium and potassium. The effects of amendments and three different forms of nitrogen [(NH2)2CO, NaNO3 and NH4Cl] on quality of acidic soil were investigated in Jiaodong Peninsula of China. A 120-day incubation test was carried out to assess the effect of amendments and nitrogen on soil physicochemical properties, soil carbon (C) mineralization and enzyme activities. The results showed that the addition of alkaline amendments can increase soil pH from 5.93 to 6.99 at the beginning of cultivation, while when amendments combined with urea or NH4Cl, soil pH decreased with incubation time. The response of C mineralization was inversely proportional to soil pH value. The addition of amendments could improve soil C content via decreasing soil C-CO2 emissions, and the mineralization rate was reduced by 26%. Addition of amendments in combination with urea or NH4Cl, which could decrease soil pH, stimulated soil C mineralization and increased soil microbial biomass carbon (MBC) and dissolved organic carbon (DOC) fractions in acidic brown soil. However, when amendments were applied with NaNO3, the soil C mineralization could be inhibited. The addition of amendments or combination of amendments and nitrogen increased the soil invertase and phenol oxidase activities, and inhibited soil urease activity. Therefore, the chemical and biological properties of the acidic brown soil in Jiaodong Peninsula of China might be better improved by combination of amendments and NaNO3.

Crude glycerol, a biodiesel byproduct, used as a soil amendment to temporarily immobilise and then release nitrogen

AbstractLoss of nitrate‐nitrogen (NO3−–N) from Midwestern U.S. agricultural fields can impair water quality and be an economic loss to farmers. Winter cover crops have shown promise as a remedy, but low adoption illustrates the need for alternatives. Here, we tested whether adding a carbon (C)‐rich soil amendment (i.e., crude glycerol, a biodiesel byproduct) can increase soil microbial biomass (MB) and promote N immobilisation under various conditions and then determined whether and when immobilised N would be released. We conducted a laboratory incubation with a full factorial combination of four glycerol rates (0, +117, +468 and +1872 mg C kg−1 soil), three supplemental NO3−–N rates (0, +10 and +40 mg N kg−1) and two soils (Clarion clay loam and Sparta loamy sand). Soil inorganic N (NH4+–N and NO3−–N) and MB were measured at seven and three time points, respectively, across the 98 days incubation period. Across all treatments, glycerol increased MBN in both short term (7 days; 4%–1137% compared to no glycerol addition) and long term (98 days; 10%–169%) and decreased NO3−–N with increasing rate of glycerol. Adding glycerol caused net N immobilisation of 21%–61% (+117 mg C kg−1 addition) and ~100% (+468 and +1872 mg C kg−1 addition) compared to the control. Some of that immobilised inorganic N was likely released through MB turnover, but timing and rate of release depended on the soil and added N rate. Adding 40 mg N kg−1 with no glycerol showed nearly twice the net N mineralisation rate than with the low or no applied N – providing evidence for soil N priming. Overall, glycerol has the potential for use as a soil amendment to increase MB and temporarily immobilise NO3−–N and then make some of that N crop available through MB turnover.Highlights Crude glycerol, a biodiesel by‐product, was evaluated as a soil amendment to reduce soil nitrate. Glycerol strongly increased soil microbial biomass and decreased nitrate under all conditions. N immobilisation was temporary, and N was mineralised at a lower glycerol rate. Glycerol rates, N rates and soil type affected N immobilisation‐mineralisation dynamics.

Double no-till and rice straw retention in terraced sloping lands improves water content, soil health and productivity of lentil in Himalayan foothills

Designing suitable conservation tillage and rice straw management practices are vital to conserve limited soil water in sloping terraced lands for growing a second crop like lentil (Lens esculentum L.) after rice (Oryza sativa L.). A field study was conducted to evaluate the effects of tillage, rice straw management and supplemental irrigation on soil physico-chemical properties and productivity of lentil grown in rice fallow land. The maximum soil water content in lentil was observed in plots under rice residue retention as mulch (@ 5 Mg ha−1) which was followed by 20 cm standing rice stubble and residue removal. Rice residue retention and 20 cm standing stubble also increased infiltration rate, cumulative infiltration and sorptivity. Adoption of double no-till (NT) for rice and subsequent lentil crop increased soil organic carbon (SOC) concentration by 2.8%, 3.4% and 7.4% at 0–5, 5–10 and 10–15 cm soil depth, respectively than those under conventional tillage (CT). Soil available nitrogen and phosphorus contents were higher under residue retention either as mulch or standing rice stubble as compared to residue removal. Double NT and added residues (mulch and 20 cm standing stubble) increased soil microbial biomass carbon and dehydrogenase activity than CT without rice residues. Application of one supplemental irrigation did not significantly influence the soil properties. The NT in both rice and lentil enhanced lentil yield by 10–18% than lentil grown after rice under CT. Rice residue retention as mulch @ 5 Mg ha−1 and 20 cm standing rice stubble gave 35–42% and 23–27% higher lentil yield against residue removal over the years, respectively. Therefore, NT in both rice and subsequent lentil along with rice residue retention @ 5 Mg ha−1 as mulch or 20 cm standing stubble would pay substantial dividends for improving the soil health, enhancing lentil productivity and ensuring double cropping in rice fallow areas of Himalayan foothills and in similar agro-ecologies elsewhere.

Increasing soil microbial biomass nitrogen in crop rotation systems by improving nitrogen resources under nitrogen application

Soil microbial biomass nitrogen (MBN) contains the largest proportion of biologically active nitrogen (N) in soil, and is considered as a crucial participant in soil N cycling. Agronomic management practices such as crop rotation and mono-cropping systems, dramatically affect MBN in agroecosystems. However, the influence of crop rotation and mono-cropping in agroecosystems on MBN remains unclear. A meta-analysis based on 203 published studies was conducted to quantify the effect of crop rotation and mono-cropping systems on MBN under synthetic N fertilizer application. The analysis showed that crop rotation significantly stimulated the response ratio (RR) of MBN to N fertilization and this parameter reached the highest levels in upland-fallow rotations. Upland mono-cropping did not change the RR of MBN to N application, however, the RR of MBN to N application in paddy mono-cropping increased. The difference between crop rotation and mono-cropping systems appeared to be due to the various cropping management scenarios, and the pattern, rate and duration of N addition. Crop rotation systems led to a more positive effect on soil total N (TN) and a smaller reduction in soil pH than mono-cropping systems. The RR of MBN to N application was positively correlated with the RR of mineral N only in crop rotation systems and with the RR of soil pH only in mono-cropping systems. Combining the results of Random Forest (RF) model and structural equation model showed that the predominant driving factors of MBN changes in crop rotation systems were soil mineral N and TN, while in mono-cropping systems the main driving factor was soil pH. Overall, our study indicates that crop rotation can be an effective way to enhance MBN by improving soil N resources, which promote the resistance of MBN to low pH induced by intensive synthetic N fertilizer application.

Organic amendment regulates soil microbial biomass and activity in wheat-maize and wheat-soybean rotation systems

Long-term heavy application of inorganic fertilizers is associated with a decrease in soil quality and biodiversity. Organic amendments have been reported to positively affect soil quality; however, relatively little is known regarding soil carbon (C) cycle enzyme kinetic parameters (Vmax and Km), community-level physiological profiles (CLPP), and the interactions between these factors and soil microbes and physicochemical properties under sustained organic amendment. Therefore, this study aimed to evaluate the effect of organic amendments on crop yield, soil chemical properties, microbial activity, enzyme kinetic parameters of five extracellular C cycle-related hydrolase enzymes, and soil microbial functional diversity in wheat-maize (WM) and wheat-soybean (WS) rotation crop systems. The results of the study showed that combined application of organic and inorganic fertilizers increased crop yield (6.81–17.47%), soil total organic C (TOC, 29.44–39.54%), total nitrogen (TN, 24.22–50.79%), available potassium (AK, 39.47–59.62%), total dissolved nitrogen (TDN, 19.68–33.75%), dissolved organic C (DOC, 14.54–55.10%), available phosphorus (AP, 34.81–243.90%), and microbial biomass C and nitrogen (MBC, 17.65–40.86% and MBN, 18.63–50.76%) concentration. The combined application also enhanced microbial growth when compared with an inorganic amendments regime. Additionally, the combined application of organic and inorganic fertilizers increased soil microbial activity and catabolic diversity and maintained a high substrate-induced respiration (SIR) value. Furthermore, the conversion from a WM rotation to a WS rotation increased both soil pH and microbial biomass, and the resultant soil exhibited lower potential activity and higher enzyme-substrate affinity. Overall, the findings of this study showed that an increase in soil microbial biomass is a key determinant of microbial catabolic activity and functional diversity.

Long-term impact of integrated nutrient management on sustainable yield index of rice and soil quality under acidic inceptisol

ABSTRACT An in-depth knowledge on impact of integrated nutrient management (INM) practice on yield sustainability and soil quality is important to scale INM practice across regions. Therefore, field experiment was initiated in 2006, which consisted of five treatments: absolute control, 100% recommended doses of nitrogen (N), phosphorus (P) and potassium (K) (RDF), 50% recommended doses of NP + 100% K + biofertilizers, 50% recommended doses of NP + 100% K + 1 t ha−1 enriched compost (ECM) and 25% recommended doses of NP + 100% K + 2 t ha−1 ECM (25RDF + 2ECM). The use of 25RDF + 2ECM increased soil organic carbon by 32 and 24% over control and RDF, respectively, at 0–5 cm soil layer. It also increased soil microbial biomass carbon, microbial phosphorus and phenol oxidase activity by 13.7, 20.9 and 55.7% than RDF, respectively, at 0–5 cm layer. Notably, phenol oxidase activity, pH, DTPA-extractable iron, available K, mineral N and microbial biomass phosphorus came out as the key indicators of soil quality in acidic soil after 10 years. The study recommends that INM practice comprising ECM and reduced inorganic fertilizers could enhance soil quality and yield sustainability of rice in the long-run in acidic soil ecology.

Manure applications combined with chemical fertilizer improves soil functionality, microbial biomass and rice production in a paddy field

AbstractThe current farming system is highly reliant on synthetic fertilizers, which adversely affect soil quality, the environment, and crop production. Improving crop productivity on a sustainable basis is a challenging issue in the current agricultural system. To address this issue, we assumed that the combined use of manure and chemical fertilizers (CF) could improve rice (Oryza sativa L.) grain yield and soil properties without the expense of the environment. Therefore, a 2‐yr field experiment was conducted to explore optimal fertilizer management strategies using a combination of CF and organic fertilizer in the form of cattle manure (CM) or poultry manure (PM). Manure was added at two levels and soil microbial biomass production, enzyme activities, nutrient content, as well as grain yield of rice were measured. The study consisted of six treatments: no N fertilizer control, 100% chemical fertilizer (Pos‐Con), 60% cattle manure + 40% chemical fertilizer (High‐CM), 30% cattle manure + 70% chemical fertilizer, 60% poultry manure + 40% chemical fertilizer, and 30% poultry manure + 70% chemical fertilizer. Results showed that the addition of manure significantly increased soil enzymatic activities such as soil invertase, acid phosphatase (POH), urease, catalase (CAT), β‐glucosidase, and cellulase as compared to sole CF application. Similarly, the combined fertilizers application led to significant increases in soil microbial biomass C (MBC), microbial biomass N (MBN), soil pH, soil organic C (SOC), total N, available N (AN), available P (AP), and rice yield. Average increases in soil MBC, MBN, SOC AN, and AP in the 0‐to‐20‐cm soil depth were 62.2, 54.5, 29.2, 17.4, and 19.8%, respectively, across the years in the High‐CM treatment compared with the Pos‐Con. In addition, the linear regression analysis showed that soil enzymatic activities were highly positively correlated with soil MBC and MBN. The principal component analysis and linear regression analyses showed that the increased soil enzyme activities and microbial biomass production played a key role in the higher grain yield of rice. Overall, the results of this study demonstrate that the combined use of synthetic fertilizer and organic fertilizer in paddy fields could be beneficial for the farmers in southern China by improving soil functionality and yield of rice on a sustainable basis.

Tree diversity effects on soil microbial biomass and respiration are context dependent across forest diversity experiments

AbstractAimSoil microorganisms are essential for the functioning of terrestrial ecosystems. Although soil microbial communities and functions are linked to tree species composition and diversity, there has been no comprehensive study of the generality or context dependence of these relationships. Here, we examine tree diversity–soil microbial biomass and respiration relationships across environmental gradients using a global network of tree diversity experiments.LocationBoreal, temperate, subtropical and tropical forests.Time period2013.Major taxa studiedSoil microorganisms.MethodsSoil samples collected from 11 tree diversity experiments were used to measure microbial respiration, biomass and respiratory quotient using the substrate‐induced respiration method. All samples were measured using the same analytical device, method and procedure to reduce measurement bias. We used linear mixed‐effects models and principal components analysis (PCA) to examine the effects of tree diversity (taxonomic and phylogenetic), environmental conditions and interactions on soil microbial properties.ResultsAbiotic drivers, mainly soil water content, but also soil carbon and soil pH, significantly increased soil microbial biomass and respiration. High soil water content reduced the importance of other abiotic drivers. Tree diversity had no effect on the soil microbial properties, but interactions with phylogenetic diversity indicated that the effects of diversity were context dependent and stronger in drier soils. Similar results were found for soil carbon and soil pH.Main conclusionsOur results indicate the importance of abiotic variables, especially soil water content, for maintaining high levels of soil microbial functions and modulating the effects of other environmental drivers. Planting tree species with diverse water‐use strategies and structurally complex canopies and high leaf area might be crucial for maintaining high soil microbial biomass and respiration. Given that greater phylogenetic distance alleviated unfavourable soil water conditions, reforestation efforts that account for traits improving soil water content or select more phylogenetically distant species might assist in increasing soil microbial functions.

Harnessing Agricultural Potential of Degraded Alkaline Soils through Combined Use of Municipal Solid Waste Compost and Inorganic Amendments

ABSTRACT Management of degraded alkali soils is an overriding challenge for agricultural production. Salt toxicity and lack of organic matter and available nutrients are major causes for poor soil fertility and low productivity. Amelioration of these soils through inorganic amendments is costly. A field experiment with six treatment combinations of different doses of organic and inorganic amendments was conducted during 2014 to 2016 on highly alkali soil, with the hypothesis that the integration of organic and inorganic amendments may offer a pragmatic solution for sustainable reclamation and harnessing their productivity potential. From our study, it was observed that combined use of municipal solid waste (MSW) compost @10 Mg ha−1 with reduced dose of gypsum or phosphogypsum (25% gypsum requirement, GR) increased soil bulk density, infiltration rate, exchangeable sodium percentage (ESP), soil organic carbon (SOC), and available N by 11%, 54%, 14%, 10%, and 13%, respectively, over the control. Integrated use of organic and inorganic amendments also increased soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP), and dehydrogenase activity by 56.85, 82.90, 78.80, and 101.00%, respectively, over the control. These changes in soil properties resulted in a profound effect on crop productivity on widely distributed alkali soils in India and other arid and semi-arid regions of the world. Therefore, application of municipal solid waste compost in combination with inorganic amendments can be a sustainable approach for restoration of degraded alkali lands for harnessing their productivity potential and the monetary savings of inorganic amendments amounting about US$ 433 ha−1, which can be utilized for the amelioration of more alkali lands.

Comprehensive impacts of diversified cropping on soil health and sustainability

ABSTRACT Conventional agriculture in the Midwest US lacks diversity, relies heavily on external inputs to maintain crop yields, and contributes to soil and water quality degradation. Using diverse crop rotations and incorporating livestock are promising solutions to these and other problems linked to current cropping systems dominated by maize (Zea mays L.) and soybean (Glycine max (L.) Merr.). To better understand how agricultural diversification comprehensively affects soil health and function, we compared 20 soil health parameters linked to critical soil ecosystem services in 1) a conventional 2-year maize-soybean rotation, and 2) a diverse 4-year maize-soybean-oat (Avena sativa L.)+alfalfa (Medicago sativa L.)-alfalfa rotation that periodically received cattle manure. The strongest and most salient improvements in soil health from the diversified, 4-year cropping system included: 8% reduction in soil resistance to root growth (p = .006), 16% increase in cation exchange capacity (p = .001), 157% increase in salt-extractable soil carbon (p = .024), and 62% increase in soil microbial biomass (p = .017). These comprehensive improvements in general soil functioning coincided with enhanced crop yields, reduced requirement for agricultural inputs, and decreased environmental impacts – all while maintaining profitability. Despite declines in cropping system diversity globally, but especially in the Midwest US, these results provide strong evidence for the benefits of diversification.

A global meta-analysis of animal manure application and soil microbial ecology based on random control treatments.

The processes involved in soil domestication have altered the soil microbial ecology. We examined the question of whether animal manure application affects the soil microbial ecology of farmlands. The effects of global animal manure application on soil microorganisms were subjected to a meta-analysis based on randomized controlled treatments. A total of 2303 studies conducted in the last 30 years were incorporated into the analysis, and an additional 45 soil samples were collected and sequenced to obtain 16S rRNA and 18S rRNA data. The results revealed that manure application increased soil microbial biomass. Manure application alone increased bacterial diversity (M-Z: 7.546 and M-I: 8.68) and inhibited and reduced fungal diversity (M-Z: −1.15 and M-I: −1.03). Inorganic fertilizer replaced cattle and swine manure and provided nutrients to soil microorganisms. The soil samples of the experimental base were analyzed, and the relative abundances of bacteria and fungi were altered compared with no manure application. Manure increased bacterial diversity and reduced fungal diversity. Mrakia frigida and Betaproteobacteriales, which inhibit other microorganisms, increased significantly in the domesticated soil. Moreover, farm sewage treatments resulted in a bottleneck in the manure recovery rate that should be the focus of future research. Our results suggest that the potential risks of restructuring the microbial ecology of cultivated land must be considered.

亚热带米槠天然林凋落物和根系输入变化对土壤磷组分的影响

植物残体添加和去除试验(The Detritus Input and Removal Treatments, DIRT)是研究地上凋落物以及植物根系对土壤营养物质循环过程及机制探究的一种试验设计。于2012年6月选择福建省三明森林生态系统与全球变化研究站的米槠常绿阔叶天然林, 设置5种处理：对照(CT)、去除凋落物(NL)、去除根系(NR)、去除凋落物与根系(NI)、添加双倍凋落物(DL), 在2018年12月对各处理不同土层(0-10cm、10-20cm)土壤磷组分及其影响因子进行研究, 结果表明：(1)在0-10cm土层中DL处理总磷含量显著大于NL处理, NI处理无机磷含量最低, 在10-20cm中DL处理有机磷含量显著大于其他处理；(2)DL处理活性磷(Resin-P、NaHCO₃-Pi、NaHCO₃-Po)含量在0-10cm土层中显著大于其他处理。在10-20cm土层中NR处理活性磷以及中等活性磷显著大于NL处理。残留态磷(Residual-P)含量最高, 但在各处理与土层之间并没有明显差异；(3)酸性磷酸酶在0-10 cm土层不同处理间的变化趋势明显, CT处理活性最高, NI处理活性最低。NR与NL处理在10-20cm土层的差异并不明显。冗余分析表明, 土壤磷组分的变化主要受酸性磷酸酶、土壤含水率、可溶性有机氮以及总氮的影响。凋落物的输入对促进土壤磷素增加, 改善土壤质量具有重要意义；植物根系则对土壤磷的活化与稳定具有关键作用。;The detritus input and removal treatment is an experimental design to study the effects of aboveground litter and plant roots on soil nutrient cycling process and mechanism. In June 2012, we set up five treatments, viz. control (CT), no litter (NL), no roots (NR), no input (NI), and double litter (DL), in a natural evergreen broad-leaved forest of Castanopsis carlesii in Sanming, Fujian Province. Soil phosphorus fractions and their influencing factors in different soil layers (0-10 cm and 10-20 cm) of each treatment were studied in December 2018. The results showed that: (1) in the 0-10 cm soil layer, the total phosphorus content in DL treatment was significantly higher than that in NL treatment. The inorganic phosphorus content in NI treatment was the lowest, The organic phosphorus content in DL treatment was significantly higher than other treatments in 10-20 cm soil layer; (2) The contents of easily-available phosphorus fractions (Resin-P, NaHCO₃-Pi, NaHCO₃-Po) in DL treatment were significantly higher than those in other treatments in 0-10 cm soil layer. In 10-20 cm soil layer, the easily-available phosphorus and moderately-available phosphorus in NR treatment were significantly higher than those in NL treatment. The content of residual-P was the highest, but there was no significant difference between the treatment and soil layer; (3) The change trend of acid phosphatase in 0-10 cm soil layer was obvious among different treatments. CT treatment had the highest activity and NI treatment had the lowest activity. The difference between NR and NL treatments was not obvious in 10-20 cm soil layer. Redundancy analysis showed that the changes of soil phosphorus fractions were mainly affected by acid phosphatase, soil moisture content, dissolved organic nitrogen, and total nitrogen. Adding litter could mineralize organic phosphorus by increasing soil microbial biomass and enhancing soil acid phosphatase activity, promote the transformation of soil organic phosphorus to inorganic phosphorus, and improve the availability of soil phosphorus. However, root system could absorb soil active phosphorus and mineralize other phosphorus fractions. It had positive significance to improve the structure of P in soil.

Elevated carbon dioxide stimulates nitrous oxide emission in agricultural soils: A global meta-analysis

Elevated carbon dioxide (CO 2 ) (eCO 2 ) has been shown to affect the nitrous oxide (N 2 O) emission from terrestrial ecosystems by altering the interaction of plants, soils, and microorganisms. However, the impact of eCO 2 on the N 2 O emission from agricultural soils remains poorly understood. This meta-analysis summarizes the effect of eCO 2 on N 2 O emission in agricultural ecosystems and soil physiochemical and biological characteristics using 50 publications selected. The eCO 2 effect values, which equal to the percentage changes of N 2 O emission under eCO 2 , were calculated based on the natural logarithm of the response ratio to eCO 2 . We found that eCO 2 significantly increased N 2 O emission (by 44%), which varied depending on experimental conditions, agricultural practices, and soil properties. In addition, eCO 2 significantly increased soil water-filled pore space (by 6%), dissolved organic carbon content (by 11%), and nitrate nitrogen content (by 13%), but significantly reduced soil pH (by 1%). Moreover, eCO 2 significantly increased soil microbial biomass carbon (by 28%) and soil microbial biomass nitrogen (by 7%) contents. Additionally, eCO 2 significantly increased the abundances of ammonia-oxidizing bacteria (AOB) amoA (by 21%), nirK (by 15%), and nirS (by 15%), but did not affect the abundances of ammonia-oxidizing archaea (AOA) amoA and nosZ . Our findings indicate that eCO 2 substantially stimulates N 2 O emission in agroecosystems and highlight that optimization of nitrogen management and agronomic options might suppress this stimulation and aid in reducing greenhouse effect.

Can cover crops improve soil ecosystem services in water‐limited environments? A review

AbstractCover crops (CCs) are considered to deliver multiple soil ecosystem services, but such potential could vary by climatic region. This leads to the question: can CCs improve soil ecosystem services in low precipitation regions? To answer this, we reviewed published data up to 27 July 2021 regarding CC impacts on CC biomass production, soil organic C (SOC) accumulation, water and wind erosion, soil water, nitrate leaching potential, soil microbial biomass, weed management, crop yields, and livestock production (i.e., CCs as forage) across regions with &lt;500 mm precipitation. Literature indicates that CCs produce 2.37 ± 2.30 Mg ha−1 of aboveground biomass, but belowground biomass data are unavailable. Cover crops increased soil wet aggregate stability (63% of CC vs. no CC comparisons), suggesting reduced water erosion potential with CCs. Also, CCs reduced nitrate leaching potential (74% of comparisons) and soil water (50%), increased soil microbial biomass (73%), and did not affect dry aggregate stability (67%) and crop yields (56%). Cover crops accumulated SOC in 59% of comparisons. Averaged across all comparisons, CCs accumulated 0.43 Mg SOC ha−1 yr−1 in the upper 30‐cm depth. This SOC accumulation rate is within the range of SOC accumulation across all regions in previous reviews. Cover crops can reduce weed biomass by 89%. Also, when hayed or grazed, CCs could provide net economic returns without negating soil benefits. Overall, CCs improve most soil ecosystem services without many detrimental effects on crop yields in water‐limited environments, although more long‐term (&gt;10 yr) data are needed for definitive conclusions.