Soil Enrichment Research Articles

Ecological and human health risk assessment of heavy metal(loid)s in agricultural soil in hotbed chives hometown of Tangchang, Southwest China

To determine the heavy metal(loid)s (HMs) contamination of agricultural soil in hotbed chives hometown of Tangchang, 788 topsoil samples were collected and analyzed for their heavy metal(loid)s concentration. The index of geo-accumulation (Igeo), pollution index (PI) and potential ecological risk index (EIi) were used to assess the degree of pollution. Correlation analysis and principal component analysis (PCA) were used to determine the sources of soil HMs. Human health risks estimated with hazard index (HI) and carcinogenic risk (CR) indices based on ingestion, inhalation and dermal exposure pathways for adults and children. The mean values of Cd, Hg, As, Pb, Cr, Cu, Ni and Zn were 0.221, 0.155, 9.76, 32.2, 91.9, 35.2, 37.1 and 108.8 mg kg−1, respectively, which did not exceed the threshold values of the risk screening value for soil contamination. The potential ecological risk of soil heavy metal(loid)s was low level and there was no significant human health risk. Based on PCA, Pb and Hg may originate from transportation and atmospheric deposition, Zn, Cr and Ni may originate from natural sources and industrial activities, and Cu and Cd may originate from agricultural activities. Overall, from the perspective of HMs content, the soil quality in this study area was at a clean level. This study provides a reference and a basis for formulating effective measures to prevent and control HMs enrichment in agricultural soils.

Post-fire dynamics of the main biogenic nutrients of the Pinus pinaster forest soil of Jijel, Northeastern Algeria

Abstract Forest fires are part of the natural dynamics of Mediterranean forest ecosystems. In the Mediterranean regions, the ecosystems are shaped by this disturbance that they have been subjected to for a long time. This work aimed to study the effect of fire on the superficial soil of the Pinus pinaster forest of Jijel, Northeastern Algeria. Soil samples were taken at a depth of 0–5 cm at different dates over a period of 24 months, in a diachronic mode. The following parameters have been tested: total carbon (C), total nitrogen (N), pH, cations exchange capacity (C.E.C.) and main exchangeable bases: calcium (Ca2+), magnesium (Mg2+), sodium (Na+) and potassium (K+). The results of the study showed a significant soil enrichment during the first few months after the fire; this temporary high fertility decreases with time due to ecosystem recovery, which could be interpreted as a return to the pre-fire state.

DISTRIBUTION OF HEAVY METALS IN SOILS ON THE TERRITORY OF THE SMALL TOWN (ON THE EXAMPLE OF NESVIZH)

The results of geochemical studies of soils on the territory of Nesvizh are presented in the context of the distribution of heavy metals. Statistical data processing has been performed. For the purposes of the study, the regional and local geochemical background was calculated. The features of enrichment and pollution of urban soils by the studied components are revealed. The concentration coefficients and the total pollution coefficient are calculated. Monocomponent and polycomponent maps were constructed, reflecting the revealed regularities in the distribution of heavy metals. The results of correlation and factor analyses are presented. Associations of heavy metals, typical for the soils of the city, were revealed. Factor loadings are calculated. A graphical representation of the matrix of factor loadings is given. The factors responsible for the formation of the technogenic situation have been established, and their contribution has been determined. The map of factor loadings has been constructed. The interpretation of geochemical data both at the level of individual points and in the space of the entire city was carried out.

Role of feather reed grass (Calamagrostis acutiflora) in phytoremediation of urban soils

Samples of soil and aerial mass of Calamagrostis acutiflora were obtained from an urban area adjacent to a street. The sampled material was analyzed to determine the content of Fe, Mn, Zn, Cu, Pb, Cd, Ni, Cr and Co, in addition to which soil was analyzed for the content of total organic carbon (TOC), salinity (EC) and reaction (pH). Based on the results, the enrichment factor (EF) and biological accumulation coefficient (BAC) of heavy metals as well as correlations between the analyzed characteristics were calculated. The content of heavy metals in the soil did not exceed the standards set for transportation areas, but the EF value implicated anthropogenic enrichment of soils with Zn, Cu, Pb, Cd and Co. Numerous, highly significant and positive correlations were obtained between the content of the elements in the soil, plants and in the soil-plant system, which suggests their relatively high bioavailability. The BAC values achieved for Co, Cr, Cu, Cd and Ni indicate that Calamagrostis acutiflora can be a useful species for phytoextraction of these elements from urban soils. Moreover, Calamagrostis acutiflora is a good choice for planting in urban areas due to its good adaptability, long growing season and tall conformation.

Can plants integrate information on above-ground competition in their directional responses below ground?

Light competition can induce varying above-ground responses in plants. However, very little is known regarding the effect of above-ground light competition cues on plant responses below ground. Here we asked whether light competition cues that indicate the occurrence and direction of neighbours above ground might affect directional root placemat. In a common-garden experiment, we examined the integrated responses of the annual procumbent plant Portulaca oleracea to light competition cues and soil nutrient distribution. Soil nutrients were distributed either uniformly or in patches, and light competition was simulated using a transparent green filter, which was spatially located either in the same or opposite direction of the soil nutrient patch. As predicted, root proliferation of P. oleracea increased in the direction of the enriched soil patches but was homogenously distributed under the uniform nutrient distribution. Interestingly, root distribution was also affected by the light competition cue and increased in its direction regardless of the location of the soil patches. Our results provide initial support to the idea that below-ground plant responses to competition might also be regulated by above-ground neighbour cues, highlighting the need to further investigate the combined effects of both above- and below-ground competition cues on root behaviour.

Streptomyces can be an excellent plant growth manager

Streptomyces, the most abundant and arguably the most important genus of actinomycetes, is an important source of biologically active compounds such as antibiotics, and extracellular hydrolytic enzymes. Since Streptomyces can have a beneficial symbiotic relationship with plants they can contribute to nutrition, health and fitness of the latter. This review article summarizes recent research contributions on the ability of Streptomyces to promote plant growth and improve plant tolerance to biotic and abiotic stress responses, as well as on the consequences, on plant health, of the enrichment of rhizospheric soils in Streptomyces species. This review summarizes the most recent reports of the contribution of Streptomyces to plant growth, health and fitness and suggests future research directions to promote the use of these bacteria for the development of a cleaner agriculture.

End of the road: Short-term responses of a large mammal community to forest road decommissioning

Anthropogenic disturbances are increasing worldwide, causing wildlife habitat loss, alteration, and fragmentation. In Canada, the decommissioning of linear anthropogenic structures is identified as a promising tool to restore the habitat of threatened populations of boreal caribou (Rangifer tarandus caribou) by reducing food availability for alternate prey and decreasing encounter probabilities with predators. In this study, we monitored the use of 40 km of decommissioned forest roads by caribou, gray wolves (Canis lupus), black bears (Ursus americanus), and moose (Alces americanus) 1–3 years after reclamation, using 232 motion-activated camera traps. We compared four additive treatments (meaning that each successive treatment included the treatment prior): closing the road to human access, decompacting its soil, planting black spruce (Picea mariana) trees, and adding enriched soil. We assessed the influence of treatments, use by other large mammals, and characteristics of the surrounding environment on road use by the four species. Caribou used the planted treatment (which also included closing and decompacting) more than the closed-only (reference) treatment, but treatments did not influence the use of decommissioned roads by bears and moose. We could not assess the use of treated roads by wolves because of low sample size. Road use by caribou declined with local moose density, but increased with local bear density. Caribou were observed more frequently on roads surrounded by regenerating and mature coniferous stands; caribou also preferentially used roads surrounded by wetlands. Our results suggest that the treatment combining road closure, soil decompaction, and tree planting could be beneficial to caribou, highlighting the relevance of including active restoration efforts in caribou conservation programs. We recommend that such a treatment be added to road decommissioning protocols for the conservation of caribou, alongside broad-scale habitat protection.

Environmental impact and health risk assessment of potentially toxic metals emanating from different anthropogenic activities related to E-wastes

The global desire for modernization through technology has thrown up a major disposal challenge for e-wastes, especially in low-economic countries. This study assessed the environmental impacts and possible health risks of potentially toxic metals emanating from poorly managed e-wastes across three main representative sites in southwest Nigeria. Soil samples were collected from three major cities in Southwestern Nigeria and analyzed for As, Cd, Pb, Cu, Cr, Ni and Zn. Pollution assessments were done using indices including contamination factor (Cf), pollution load index (PLI) and potential ecological risk index (PERI) coupled with evaluation of non-cancer and cancer health risks. Results showed enrichment of the local soil with metals due to e-wastes related activities, with an elevated level of Cf (>6), revealing that the soils around the e-waste dumpsites were severely contaminated. In addition, the assessment of individual metal potential ecological risk index (Eif) showed a high level of potential ecological risk for Cd (Eif >320) at all the sites while As, Pb, Cu and Ni exhibited high ecological risk at the sites, especially at topsoil layer. Furthermore, the study established varying potentials for carcinogenic health risks for residents around the dumpsites, such that while a negligible risk index occurred for Cd and Ni (RI < 10−6), the risk is tolerable for Pb (0−6 < RI < 10–4) but within cancer-development range for As and Cr (RI > 10−4). The study concluded that poorly managed e-wastes in the area poses significant threats to the health of humans and the entire ecosystem. Further study is recommended to identify similar e-waste dumpsites at regional and national – scales for sustainable restoration and improved e-waste management.

Implementation of Circular Economy in Peatlands to Support Sustainable Food Security in Post Covid-19 Era

The peatlands in Indonesia have changed quite a lot in recent years due to over-exploitation and climate change. The land-use change on peatlands resulted in soil infertility. The impacts of the degradation of peatlands are almost certain to worsen with the COVID-19 pandemic because the peatlands have an important role in providing food resources. Therefore, the peatlands restoration must be carried out considering the importance of the peatlands as food resources and carbon capture. One of the alternative solutions is to recycle the waste from agroforestry into organic fertiliser. This study aimed to investigate the application of organic fertiliser to restore soil fertility in the peatlands. The study also offered the circular economy scheme that can be applied in the peatlands to restore sustainability. The results showed that the degraded peatland that has been restored by adding organic fertiliser from local sources has a higher soil pH level than the one without adding organic fertiliser. The increase in pH level can decrease soil hydrophobicity and increase microorganism activities, encouraging biodiversity in the peatlands. In this study, the circular economy scheme by the integration between agroforestry and livestock was assessed economically and environmentally. Recycling cows’ manure and leaf litter from peatlands into energy and recycling biogas sludge into biochar for biogas purification and soil enrichment benefit economically and contribute to mitigating greenhouse gas emissions.

Abundance, isolation, and characterization of halotolerant microbes from common oligosaline soils

Halotolerant microbes that grow at high NaCl concentrations were studied in common soils with low salinity. The abundance of microbes in common oligosaline (<1.0% salinity) soils was measured by most probable number analyses, where statistically valid replicates of serial dilutions were assessed for growth in liquid Salt Plains medium with 0.1, 10, or 20% (w/v) NaCl. Common Kansas soils were collected from oligosaline agricultural fields (corn, cotton, sorghum, and soybean), pond margin, prairie grassland, and woodland. The abundance of microbes able to grow at 10% NaCl was 0.0025–0.32% of the total counts at 0.1% NaCl. Only marginal growth was observed at 20% NaCl, about 100-fold lower than at 10% NaCl. Bacterial isolates were collected from 20% NaCl enrichments of oligosaline turf soil by repetitive streak-plating. The bacteria were identified by 16S rRNA gene sequencing and characterized. The isolates clustered with low G+C Gram-positive genera (Bacillus, Halobacillus, Staphylococcus, and Virgibacillus). Broad halotolerances (0.1–20% NaCl) were observed for most isolates, but all grew at low salt. Soils were boiled to kill vegetative cells and compared by most probable number analyses with unboiled specimens. The abundance of microbes able to grow at 10% NaCl showed a 3-log decrease with boiling, while microbes able to grow at 0.1% NaCl showed a 5-log decrease in abundance with boiling. It appears that halotolerant microbes in oligosaline soils are cultivable vegetative cells, not perennating structures such as spores. Discrete salt phases are not obvious in oligosaline soils, but could provide a selective advantage to autochthonous halotolerant microbes. Allochthonous microbes associated with salt evaporite particles may be transported by winds, thereby dispersing deliquescent hypersaline microhabitats.

Soil Amendments with Spearmint, Peppermint and Rosemary Enhance the Community of Free-Living Nematodes and Improve Soil Quality, While Having Strikingly Different Effects on Plant Growth.

Sustainable farming practices aim to replace agrochemicals with plant-based alternatives to increase productivity and soil quality. To evaluate the potential use of aromatic plants as soil amendments in tomato seedbeds, in a greenhouse experiment, we used spearmint, peppermint, and rosemary, separately, as soil amendments, in pots sown with tomato, and studied their effect on seedling growth, soil nutrients, and the soil nematode community in terms of trophic and functional structure, metabolic footprint, and genera composition. Non-amended soil was used in the control pots. We further explored the dynamics of the plant–soil–nematode interactions by using aromatic plants at different stages of decomposition (0, 28, and 56 days). Incorporating aromatic plants into the soil led to the proliferation of free-living nematodes, especially of the opportunistic kind, resulting in vigorous and enriched soil. This was more pronounced in the case of the spearmint and peppermint, which also increased the tomato growth. The high soil nutritional status and enhanced plant growth were most prominent when the aromatic plants were left for 28 days to decompose in the soil before sowing. Compared with the mint plants, the rosemary had similar, yet less intense, effects on the soil community, but completely inhibited the growth of the tomato seedlings. Therefore, it is not recommended for use as a soil amendment in tomato seedbeds.

Biogeoaccumulation of zinc in hybrid rice (Oryza sativa L.) in an Inceptisol amended with soil zinc application and its bioavailability to human being

Soil Zn amended is an efficient agronomical Zn biofortification approach in rice. However, it is still need to know if higher rate of Zn over recommended dose can influence other essential nutrient uptake, high accumulation of Zn in soils and health risk for human consumption. This study was conducted by taking ten treatments (T1: control, T2: RDF, T3: RDF + 1.25 mg kg-1, T4: RDF + 2.5 mg kg-1, T5: RDF + 3.75 mg kg-1, T6: RDF + 5 mg kg-1, T7: RDF + 6.25 mg kg-1, T8: RDF + 7.5 mg kg-1, T9: RDF + 8.75 mg kg-1, T10: RDF + 10 mg kg-1) on hybrid rice in Zn (1.20 mg kg-1) enriched soil. The findings have shown that 6.25 mg kg-1 Zn application significantly increased crop growth and grain concentrations of N, K, Zn, Cu and Fe by 71.4, 125, 78.9, 28.5 and 2.4%, respectively. Nutrient harvest index was significantly affected by ranged between 29.1–36.4%. Application of Zn at 6.25 mg kg-1 (T7) recorded the highest Zn concentration in grain (28.2 mg kg-1) and bioavailability of the fortified Zn (2.05 mg Zn day-1). The lowest phytatic acid concentration in grain was recorded in T8 (RDF + Zn at 7.5 mg kg-1) and after that a significant increase was observed. Transfer coefficient was inversely behaving with Zn application and ranged between 6.03–18.0 grain. The average daily intake of Zn was ranged between 0.075–0.118 mg-1 kg-1 day. Across different treatments the Zn build-up factor, geo-accumulation index and soil enrichment factor was ranged between 0.98–4.90, -0.61–1.70 and 0.24–1.82, respectively in post-harvest soil. In conclusion, agronomic biofortification of Zn through soil applications at 6.25 mg Zn kg-1 was a sustainable way to improving growth and grain Zn, N, K, Cu and Fe uptake of hybrid rice to meet human recruitment.

Legacy of war: Pedogenesis divergence and heavy metal contamination on the WWI front line a century after battle

AbstractIn Europe, the First World War left a legacy on the environment due to the extensive and intense use of artillery during this period. This study examined a small wooded area in the Pas‐de‐Calais region in France which was subject to considerably less intense fire than previously studied WWI battlefields. In a process named “bombturbation,” significant physical changes have occurred to the landscape subject to artillery fire, resulting in a divergent soil development in craters. Cratering led to higher organic matter and electrical conductivity values, but—unlike other studies—no significant difference in soil pH. Soil heavy metal concentrations did not differ within craters compared to the flat landscape. However, lead (Pb) and copper (Cu) enrichment was observed above the baseline values for the region. Despite the average concentrations of Cu and Pb being within legal limits for soils in the UK and European Union, it is likely that enrichment of Cu and Pb in the concentrations observed has caused detrimental ecotoxicological and human health effects.Highlights Few studies investigate the legacy of WWI on soil, particularly from low intensity fighting. WWI bomb craters alter soil development, resulting in changes to organic matter and salinity. Cu and Pb enrichment of soil from WWI may lead to ecotoxicological and human health impacts.

Slow release of copper from jellyfish-based hydrogels for soil enrichment

Nanotechnology has shown great potential to increase global food production and enhance food security. However, large-scale application of nano-enabled plant agriculture necessitates careful adjustments in design to overcome barriers associated with targeted nanomaterial delivery and their safety concerns. The research herein proposes the delivery of copper (Cu) from immobilized and non-immobilized copper oxide nanoparticles (Cu2O), an active nanomaterial with antifungal and micro-nutrient properties. A benign and biodegradable jellyfish-based hydrogel was used as a platform during Cu2O delivery to soils. The delivery kinetics and Cu dissolution from the nanocomposite were compared to those obtained with crosslinked ionic Cu in hydrogel, which was found to be a less controlled composite. In addition, changing environmental conditions from DI to soil extracts resulted in a decrease in the Cu dissolution rate (from 0.025 to 0.015 h−1) and an increase in the overall normalized Cu release (0.27 to 0.76 mg g−1). Use of hydrogels from natural sources allowed biodegradability over several months, adding nutrients (in the form of elements such as sulfur, nitrogen, and carbon) back to the environment, which ultimately minimizes nanomaterial required for a given desired nanomaterial yield and enhances the overall performance. Altogether, this work demonstrates the potential of Cu2O embedded hydrogels as a benign composite for Cu slow-release and therefore bolsters the field of nano-enabled plant agriculture and supports its safe deployment at large scales.

Characterizing Mechanical, Heat Seal, and Gas Barrier Performance of Biodegradable Films to Determine Food Packaging Applications.

In an organic circular economy, biodegradable materials can be used as food packaging, and at end-of-life their carbon atoms can be recovered for soil enrichment after composting, so that new food or materials can be produced. Packaging functionality, such as mechanical, gas barrier, and heat-seal performance, of emerging biodegradable packaging, with a laminated, coated, monomaterial, and/or blended structure, is not yet well known in the food industry. This lack of knowledge, in addition to end-of-life concerns, high cost, and production limits is one of the main bottlenecks for broad implementation in the food industry. This study determines application areas of 10 films with a pragmatic approach based on an experimental broad characterization of packaging functionality. As a conclusion, the potential application of these materials is discussed with respect to industrial settings and food and consumer requirements, to support the implementation of commercially available, biodegradable, and, more specifically, compostable, materials for the identified food applications.

Optimizing textile dyeing wastewater for tomato irrigation through physiochemical, plant nutrient uses and pollution load index of irrigated soil

Reuse of wastewater for vegetable cultivation is becoming popular in order to augment the inadequate irrigation supplies and meet the growing demands of ground water for agriculture and industries production in different regions of the world. This study was investigated to optimize different stages of textile dyeing wastewater (TDW) for irrigation focusing on their effect on growth, yield and physiochemical attributes of tomato, plant nutrient use, heavy metals enrichment and pollution load of the irrigated soil. Textile wastewater were collected from the seven stages of (second wash after scouring and bleaching T2; enzyme treated water T3; second wash after bath drain T4; neutralization treatment T5; second wash after soaping T6; fixing treatment water T7; mixed effluent T8) of a dyeing process for physiochemical characterization and evaluation their irrigation feasibility for tomato cultivation in compare with the ground water (T1). The pot experiment consists of eight irrigation treatments was laid out following a completely randomized block design with three replications. Results showed the presence of plant nutrients and heavy metals in all the studied samples where T8 (mixed effluent) exceeded the limit of agricultural standard for almost all physiological parameters such as TDS, TSS, EC, BOD, COD affording the highest value. T8 also delivered the highest Cl- and heavy metals like Cd, Ni, Cr followed by T4 < T7. As a consequence, these provided comparatively higher enrichment factor (EF), pollution load index (PLI) and sodium absorption ratio (SAR) to transform fresh soil into the category of severe and slightly to moderate saline. Therefore, the yield and physiochemical attributes of tomato were dramatically reduced with T8 and T4 treatment. On the other hand, T2, T3 and T6 treatment had significant positive impact on growth and yield of tomato due to having higher N, P, K, S and lower heavy metals (Cu, Zn, Fe, Pb, Cd, Ni, Cr) than the recommended guideline. These features were contributed to cause minimum EF and PLI in the soil irrigated with T2, T3 and T6 stages of TDW. Correlation matrix demonstrated that EF and PLI of heavy metals (except Cd, Ni) were negatively related to yield, while positively related to SAR and fruit abortion. Although T6 (2nd wash after soaping) performed better in respect to growth, yield, yield attributes and nutrient use efficiency, principal component analysis revealed that T2 (2nd wash after scouring and bleaching) and T3 (enzyme treated water) were also belong to the same group of T6 and T1 (ground water). Thus, it may be suggested that T2, T3 and T6 stages of textile dyeing wastewater could be used profitably without ETP for vegetable cultivation and would effectively supplement not only the nutrient requirement of the crop but may also act as the alternate source of irrigation water. Although, further research is needed to sort out the health risk assessment through the heavy metals’ accumulation in the plant parts after irrigation with different stages of textile dyeing wastewater.

Nitrogen Losses and Enrichment of Soil and Sawdust Coverings during Composting of Poultry Manure

Aims: Composting poultry manure is an effective way of enhancing its nutrient content and reduce nutrient losses. There is the need to reduce gaseous nutrient losses during composting through the use of covering materials. Assess the level of chemical enrichment of soil and sawdust used as covering materials; and identify the most suitable medium that can best perform as a covering material during composting of poultry manure.&#x0D; Materials and Methods: Experiments were set up to examine the changes in the chemical properties of soil and sawdust used as covering material for composted poultry manure. Five treatments – no covering, layers of 2.8 kg soil, 5.6 kg soil, 0.9 kg sawdust, and black polythene sheet on 5.28 kg broiler and layer manure heaps with four replications were arranged in a completely randomized design. Samples were taken from the manure piles and the soil and sawdust covering materials for chemical analysis at 3, 6 and 9 weeks after composting.&#x0D; Results: The pH, N, P, K, Na and Ca, in both soil covers increased as time elapsed, whereas the Mg and C/N ratios of the soil coverings decreased with time. With regards to the broiler manure, however, the pH and the nutrient content of the two levels of soils used as cover increased at all the stages of composting. Composting of both poultry manures resulted in the improvement of the chemical properties of both sawdust and soil coverings. The enrichment ratio of N was greater in the 5.6 kg soil than the 2.8 kg soil covering. Additionally, the 5.6 kg soil covering was highly efficient (P = .05) in reducing N losses by 57 and 83.85% from the broiler and layer piles, respectively. In general, the 5.6 kg soil was the most effective covering material.

Soil meets stream: Vertical distribution of soil phosphorus in streambanks

Characterizing the vertical distribution of total phosphorus (P) and P forms in streambanks can improve estimates of P loads to streams via bank erosion. Using a systematic literature review, this meta-analysis evaluated the vertical distribution of total P (Ptot), Bray-1 test P (PBray1), oxalate-extractable P (Pox), degree of P saturation (DPSox), and soil P storage capacity (SPSC) at 161 streambank locations encompassing diverse soil orders and riparian land covers. Across studies, maximum soil sampling depth (125 cm) was on average half that of streambank height (250 cm on average), and water quality-related P fractions such as water-extractable P (Pw) were not generally reported. Slightly weathered Entisols and Inceptisols collectively accounted for 84% of observations, likely reflecting alluvial deposition environments along stream corridors, and exhibited decreasing Ptot (820 to 400 mg kg−1) with increasing depth to 200 cm. Irregular changes in Ptot at depth > 200 cm of Entisols and Inceptisols suggested burial of organic-rich A horizons by alluvial deposition. Changes in riparian land cover mainly affect Ptot in the upper 60 cm, with depth-weighted mean Ptot increasing as grassland (217 mg kg−1) < forest (628 mg kg−1) ≈ wetland (624 mg kg−1) < developed (684 mg kg−1) < agriculture (739 mg kg−1), consistent with expected anthropogenic P enrichment of surface soils and posing increased P loading risk. Effect size analysis showed that riparian land cover had a large influence on Ptot within the top 30 cm depth whereas soil order and bedrock type had large influences on subsurface Ptot, suggesting depth-divergent drivers of P in streambank soils. Additionally, Ptot and Pox were positively correlated with silt, clay, carbon, cation exchange capacity (CEC), oxalate-extractable iron (Feox) and aluminum (Alox), and total Fe (Fetot) contents. This work helps advance understanding of the vertical variation of streambank soil P across diverse soil types, land covers, and soil properties, and their implications for P loading from bank erosion. We also identify gaps in sampling approaches (insufficient depth) and analysis (Pw) that may be hindering comprehensive assessment of bank erosion P loading and risk to water quality. Finally, we illustrate how fluvial erosion and deposition may generate complex vertical P distributions in streambanks, with implications for estimating erosional P loading that can benefit from a pedologically explicit approach.

GREEN MANURE AS A SOIL FERTILITY AND ENVIRONMENTAL OPTION IN SEMIARID AGROSYSTEMS: MINERALIZATION RATE AND N CONTENT

Green manures are an adequate alternative for improving the availability of nitrogen and phosphorus for crop nutrition, within a global context of decreasing soil fertility and the urgent need to care for the environment. Mixteca region, covers a wide area of central Mexico, characterized by a semi-arid climate, eroded calcareous soil, and rural poverty. With the aim of proposing technologies for improving soil quality and increasing the availability of nitrogen and phosphorus, an experiment was conducted using green manures: Canavalia ensiformis, Dolichos lablab, Leucaena leucocephala and Avena strigosa and Phaseolus vulgaris, that would ensure a balance between N and P release and the requirements of maize cultivation. The rate of enriched soil mineralization with green manures was determined through incubation, controlled for 15 days with CO2 emissions using an OxiTop OC110® kit as an indicator of decomposition. CO2 emissions were greatest in the soil established with Leucaena leucocephala and least in the soil with no fertilizer, with emissions descending in the following order: Leucaena leucocephala &gt; Canavalia ensiformis &gt; Avena strigosa +Phaseolus vulgaris &gt; Dolichos lablab &gt; soil without green manure. It is assumed that a greater flow of CO2 is accompanied by greater mineralization and release of nutrients. The Ntotal in the soil treated with green manures was similar and greater than that of the soil without fertilizer. Soil treated with Avena strigosa+Phaseolus vulgaris contained the highest values of Nmineral (N-ammonium + N-nitrate). POlsen content in soils with green manures was double that of the soil without fertilizer. Incubation provided the opportunity of identifying those green manures with higher agronomic potential in the area under study. The biomass comprising Leucaena leucocephala leaves and tender stems constitute an alternative for improving soil by providing OM. However, when considering the availability of N and P, the Avena strigosa+Phaseolus vulgaris combination is a superior alternative for meeting the needs of maize cultivation.

Changes in soil properties and CO2 emissions after biochar addition: Role of pyrolysis temperature and aging

Biochar has been regarded as an effective amendment for soil carbon sequestration and soil quality improvement. However, it remains unclear how pyrolysis temperature and biochar aging impact the responses of soil properties and CO2 emissions to biochar addition. Here, we investigated the effect of biochar on soil properties and CO2 emissions in a laboratory incubation using soils amended with/without fresh biochar produced at 300 (BC300), 450 (BC450), and 600 °C (BC600) and their corresponding naturally aged samples (aged in soil for 360 days). The results showed that biochar significantly increased soil total nitrogen (by 8–36%), available phosphorus (by 19–69%) and available potassium (by 1.5–4.2-fold) throughout the incubation. Both fresh and aged biochar promoted the formation of soil macroaggregate at the end of the incubation. Moreover, fresh and aged BC300 increased the soil dissolved organic matter (DOM) content, whereas for BC450 and BC600, at the beginning, the content of soil DOM was reduced, but the effects finally became insignificant. Generally, fresh biochar had no significant effect on soil enzyme activities and soil bacterial richness and diversity, but an inhibitory effect occurred in the aged samples. Both fresh and aged BC300 increased soil CO2 emissions, which was due to the biochar-induced increase in soil DOM content and enrichment of copiotrophic bacteria (Proteobacteria) as well as the decline of oligotrophic bacteria (Acidobacteriota). A significant decrease in soil CO2 emissions was observed after fresh BC450 and BC600 addition, owing to the biochar-induced decline in soil DOM content, while an opposite trend was found in aged samples, which could be attributed to the shift of the dominant soil phylum from Acidobacteriota to Proteobacteria. These findings enhance our understanding of biochar's potential to improve soil quality and sequester soil carbon.