Phosphorus (P) is an indispensable element for all life on Earth and, during the past decade, concerns about the future of its global supply have stimulated much research on soil P and method ...development. This review provides an overview of advanced state‐of‐the‐art methods currently used in soil P research. These involve bulk and spatially resolved spectroscopic and spectrometric P speciation methods (1 and 2D NMR, IR, Raman, Q‐TOF MS/MS, high resolution‐MS, NanoSIMS, XRF, XPS, (µ)XAS) as well as methods for assessing soil P reactions (sorption isotherms, quantum‐chemical modeling, microbial biomass P, enzymes activity, DGT, 33P isotopic exchange, 18O isotope ratios). Required experimental set‐ups and the potentials and limitations of individual methods present a guide for the selection of most suitable methods or combinations.
Land application of farmyard manure (FYM) is a widespread agronomic practice used to enhance soil fertility, but its long-term effects on soil microbial carbon (C) and nitrogen (N) cycling have not ...been investigated in detail. Topsoils (0–23 cm) and subsoils (23–38 cm) were collected from a field trial on a sandy-textured soil where FYM had been applied at high (50–25 t ha−1 yr−1, 28 yr) and low rates (10 t ha−1 yr−1, 16 yr), and compared to soil treated only with synthetic NPK fertilisers. The turnover rate of key components of soil organic matter (SOM; proteins, peptides, amino acids, cellulose, and glucose) were evaluated by 14C labelling and measuring cellobiohydrolase, β-glucosidase, β-1,4-N-acetylglucosaminidase, L-leucine aminopeptidase, protease, and deaminase activities, whereas gross NH4+ and NO3− production and consumption were determined by 15N-isotope pool dilution. Microbial communities were determined using phospholipid fatty acid (PLFA) profiling. Our results indicate that long-term FYM addition significantly enhanced the accumulation of soil C and N, soil organic N (SON) turnover, exoenzyme activity, and gross NO3− production and assimilation. Rates of protein, peptide, and amino acid processing rate were 169–248, 87–147, and 85–305 mg N kgDWsoil−1 d−1, respectively, gross NH4+ and NO3− production and consumption were 1.8–5.8 mg N kgDWsoil−1 d−1, and the highest rates were shown under the high FYM treatment in topsoil and subsoil. The half-life of cellulose and glucose decomposition under the high FYM treatment were 16.4% and 31.0% lower than them in the synthetic NPK fertiliser treatment, respectively, indicating higher rates of C cycling under high manure application as also evidenced by the higher rate of CO2 production. This was ascribed to an increase in microbial biomass rather than a change in microbial community structure. Based on the high pool sizes and high turnover rate, this suggests that peptides may represent one of the dominant forms of N taken up by soil microorganisms. We conclude that long-term FYM application builds SOM reserves and induces faster rates of nutrient cycling by boosting microbial biomass rather than by changing its community composition.
•The influence of manure application on soil C/N cycling was evaluated.•14C labeling and 15N-pool dilution techniques were used.•Manure application significantly affects C/N cycling in soil by boosting microbial biomass.•Peptides may be important for terrestrial cycling and supply of N.
Microplastics (MPs, <5 mm in diameter) have been widely recognized as a critical environmental issue due to their extensive use and low degradation rate. Based on current evidence, our aim is to ...evaluate whether MPs represent an emerging threat to plant-soil health in agroecosystems. We assess the ecological risks to plant-microbe-soil interactions associated with MPs and discuss the consequences of MPs on soil carbon (C), nutrient cycling, as well as greenhouse gas emissions in agroecosystems. We also identify knowledge gaps and give suggestions for future research. We conclude that MPs can alter a range of key soil biogeochemical processes by changing its properties, forming specific microbial hotspots, resulting in multiple effects on microbial activities and functions. Mixed effects of MPs on plant growth and performance can be explained by the direct toxicity of MPs or the indirect alteration in soil physical structures and microbial communities (i.e. symbiotic arbuscular mycorrhizal fungi). Because of the diverse nature of MPs found in soils, in terms of polymer type, shape and size, we also see differing effects on soil organic matter (SOM) decomposition, nutrient cycling, and greenhouse gases production. Importantly, increased bioavailable C from the decomposition of biodegradable MPs, which enhances microbial and enzymatic activities, potentially accelerates SOM mineralization and increases nutrient competition between plant and microbes. Thus, biodegradable MPs appear to pose a greater risk to plant growth compared to petroleum-based MPs. Although MPs may confer some benefits in agroecosystems (e.g. enhanced soil structure, aeration), it is thought that these will be far outweighed by the potential disbenefits.
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•MPs can alter rhizodeposition input and soil organic matter decomposition.•Effects on soil C and nutrient cycling depend on MP types, concentration, size, and shape.•Nano-sized MPs can accumulate in roots and be transported to the shoot.•Bio-based MPs can exert strong negative effects on plant by increasing nutrient competition.
The crucial biogeochemical processes such as carbon and nutrient cycling are increasingly altered at the ecosystem scale by global environmental changes. Although soil extracellular enzyme activities ...(EEAs) play a critical role in biogeochemical processes, the global patterns of soil EEAs in a changing world remain elusive. Here, we synthesized eight EEAs involved in carbon (C), nitrogen (N) and phosphorus (P) acquisition in response to seven global change factors based on 132 peer-reviewed papers. Our results showed that elevated CO2 concentration had no significant effects on soil EEAs. Nitrogen addition stimulated C-acquisition (9.1%) and P-acquisition (9.9%) EEAs, but suppressed oxidase activity (−6.8%). Phosphorus addition decreased P-acquisition EEA (−19.8%), while combined N and P addition increased C-acquisition EEA (30.7%). Moreover, decrease in precipitation dramatically suppressed oxidase activity (−47.2%), increase in precipitation marginally stimulated N-acquisition EEA (16.7%), while warming significantly decreased oxidase activity (−10.9%) and had minor positive effect on hydrolytic enzymes. Overall, our results provide some evidence (with exceptions) for the resource allocation theory of microbial enzyme production, and indicate that EEAs are generally more sensitive to nutrient addition than to atmospheric and climate change. We have shown that global environmental changes can alter EEAs, which have implications for soil carbon storage, nutrient cycling, and plant productivity. Further research is needed to elucidate the underlying mechanisms driving the responses of EEAs to global change and to collect data from particularly non-forest ecosystems (e.g., wetland, tundra and desert) and global-change drivers (other than N addition) that lack of EEA data. Our synthesis of the responses of soil enzyme activities to global-change drivers can be used to develop better representations of microbial processes in ecosystem and earth system models.
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•We performed a global meta-analysis of soil enzymes in response to global change drivers.•Data include eight enzymes and seven drivers from field experiments in natural ecosystems.•Enzymes are more sensitive to nutrient addition than to atmospheric and climate change.
Deadwood decomposition modulates habitat structure and enhances resource availability within forest ecosystems. Deadwood decomposition is influenced by a combination of abiotic and biotic factors, ...wherein climatic variables, tree species, and wood characteristics play fundamental roles. However, the scarcity of studies conducted in dry and semiarid regions restricts our understanding of deadwood decomposition dynamics. Here, we studied the decomposition of logs in four plots across an elevation gradient spanning approximately 1000 m (from 1477 to 2317 m a.s.l.). The site was a burnt reforestation of different pine species in a Mediterranean mountain (Sierra Nevada, SE Spain). Logs of a range of diameters were cut to a similar length (75 cm), and their density loss was monitored over 15 years. We fitted three different types of functions (linear, negative exponential and negative sigmoidal) to evaluate the temporal trajectory of decomposition across the elevation gradient. Average wood density loss through the 15-year period ranged from 30.4 % to 63.3 % depending on the elevation plot, and it was highest at an intermediate elevation. The negative sigmoidal equation showed the best fit, but all functions rendered similar half-life values, which ranged between 12.8 and 29.4 years depending on the elevation plot. Contrary to most studies, larger-diameter logs experienced a quicker decomposition process, which could be linked to increased moisture retention and greater activity of large invertebrates in the larger-diameter logs. The variations observed across the elevation gradient are consistent with expectations on how the interaction between precipitation and temperature influences decomposition rates. The observed decomposition patterns in these mountain forests indicate a relatively rapid process, and underline the vital contribution of deadwood biological legacies to the preservation of soil fertility in the Mediterranean region.
•We studied wood decomposition for 15 y in a Mediterranean mountain at 1477 – 2317 m elevation.•Trunks lost 30.4 % – 63.3 % of density, peaking at intermediate elevation.•A negative sigmoidal curve explained the process better than a linear or negative exponential.•Modelled half-life of wood ranged from 12.8 to 29.4 y across elevations.•Thicker logs decomposed faster, challenging findings from other regions.
Microorganisms mediate nutrient cycling in soils, and thus it is assumed that they largely control responses of terrestrial ecosystems to anthropogenic nutrient inputs. Therefore, it is important to ...understand how increased nitrogen (N) and phosphorus (P) availabilities, first, affect soil prokaryotic and fungal community composition and second, if and how changes in the community composition affect soil element cycling. We measured soil microbial communities and soil element cycling processes along a nine-year old experimental N-addition gradient partially crossed with a P-addition treatment in a temperate grassland. Nitrogen addition affected microbial community composition, and prokaryotic communities were less sensitive to N addition than fungal communities. P addition only marginally affected microbial community composition, indicating that P is less selective than N for microbial taxa in this grassland. Soil pH and total organic carbon (C) concentration were the main factors associated with prokaryotic community composition, while the dissolved organic C-to-dissolved N ratio was the predominant driver of fungal community composition. Against our expectation, plant biomass and plant community structure only explained a small proportion of the microbial community composition. Although microbial community composition changed with nutrient addition, microbial biomass concentrations and respiration rates did not change, indicating functional redundancy of the microbial community. Microbial respiration, net N mineralization, and non-symbiotic N2 fixation were more strongly controlled by abiotic factors than by plant biomass, plant community structure or microbial community, showing that community shifts under increasing nutrient inputs may not necessarily be reflected in element cycling rates. This study suggests that atmospheric N deposition may impact the composition of fungi more than of prokaryotes and that nutrient inputs act directly on element-cycling rates as opposed to being mediated through shifts in plant or microbial community composition.
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•Nutrient inputs differentially impacted microbial communities and element cycling.•Soil pH and total organic carbon were main drivers of prokaryotic communities.•DOC:DN ratio was the predominant driver of fungal community composition.•Element cycling was controlled by abiotic factors, not by microbial community change.•Microbial community change may not necessarily change ecosystem functioning.
In today's technologically advancing and increasingly urbanized world, the search for new materials like biochar has become crucial to address environmental challenges such as pollution and ...agricultural needs. Biochar, derived from pyrolyzed biomass, offers a sustainable solution for soil improvement and pollution control. This review explores biochar's diverse applications in waste management, pollution control, and agriculture, emphasizing its potential for promoting sustainability and circular economy practices, while also discussing emerging applications like supercapacitors. Compared to previous works, this review offers a comprehensive examination of biochar's diverse applications and its potential for future trends in environmental sustainability.
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•A review was conducted on the use of biochar for environmental remediation purposes.•Biochar plays a crucial role in enhancing soil health and boosting crop productivity.•Future research in biochar is poised to explore unconventional applications.•Biochar holds significant potential for addressing global.
Drought has the most significant impact on arid grassland ecosystems. Managed grazing, including the timing and intensity of defoliation, may interact with drought to differentially affect processes ...related to soil organic matter decomposition. Extracellular enzyme activity (EEA) provides integrated measure of soil microbial activity which affects nutrient cycling. This study examined EEAs in response to five defoliation regimes and drought at seven grasslands across temperate grasslands of Canada. All sites were dominated by perennial grasses and forbs, but differed in plant species, climate, and soils. Soil samples were analyzed for five EEAs involved in carbon (C), nitrogen (N) and phosphorus (P) cycling. Drought reduced activity of enzymes involved in C cycling, β-glucosidase and β-cellobiosidase by 16 and 17%, respectively, P cycling (acid phosphatase) by 11%, and N cycling (N-acetyl-β-glucosaminidase) by 12%. β-xylosidase showed close association with, and was not affected by drought, suggesting a reduction in C turnover under future drought. β-glucosidase activity was reduced by intermediate defoliation relative to both control and heavy. Acid phosphatase and N-acetyl-β-glucosaminidase were affected by three-way interaction of drought, defoliation and mean growing season precipitation, highlighting the complex mechanism underlying EEA responses. Findings suggest that EEA was affected by drought, but defoliation effects were largely dependent upon drought and local climate.
•Drought reduced activity of enzymes involved in C and N cycling, except β-xylosidase.•Effects of defoliation on extracellular enzyme activity were contingent upon drought.•β-xylosidase showed a positive association with drought.
•Sludge contains recyclable and agronomical valuable macro and micronutrients.•Sludge application on cropland reduces need of synthetic fertilizers, causing sustainability of agriculture.•Sludge can ...contain harmful organic and inorganic contaminants.•In some cases, sludge application on cropland can contaminate water, soil & food chain.•Interaction of inorganic and organic compounds with environment should be investigated for long-term risks.
Digested sludge is a good source of plant nutrients. However, depending on the feedstock, it might contain heavy metals, metalloids, organic compounds, pathogens, and pharmaceuticals, which can cause adverse effects on crop growth and contaminate the groundwater, soil, and food chain.
The aim of this review is to focus on the potential risks of inorganic and organic contaminants to plant growth, soil, groundwater, and consequently the food chain and environment related to the utilization of digested sludge as a fertilizer on cropland.
Inorganic compounds, such as metals and metalloids, in sludge can occasionally cause reductions in soil microbial biomass. In general, the uptake of metals and organic contaminants does not appear to cause a significant hazard to the plants and the concentrations do not surpass the maximum values allowed in soil. Organic compounds, harmful for human health or the environment, are to a large extent decomposed or volatilized from the land treated with sludge, which decreases their leaching into the environment. Many of the organic compounds are lipophilic and can be bound to soil organic matter. In conclusion, the application of sludge on cropland might be a sustainable management practice; however, further investigations are needed to determine the accumulation and persistence of possible hazardous emerging chemicals and pathogens in the environment and formation of harmful intermediate reaction of inorganic and organic compound products.
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