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The soil-water characteristic curve (SWCC) is an essential tool to determine hydraulic and mechanical properties of unsaturated soils. As an inherent influencing factor, soil texture controls the characteristics of SWCCs. Fractal theory can quantitatively describe the physical characteristics of soil. This study used particle size distribution data and water content data contained in the UNSODA2.0 database to explore the fractal characteristics of 12 soil types with different textures under different matrix suctions. The SWCC fractal model was adopted to characterize the hydraulic properties of soil with various soil textures. The findings revealed that the mass fractal dimensions of particles from these 12 different soil types significantly differed and were closely related to the clay content. Fractal dimension increased with increasing clay content. The fractal dimension established a good relationship between soil structure and hydraulic properties. Fractal analysis can be used to determine the connection between physical properties and soil hydraulic parameters. The estimated results of the SWCC fractal model indicated that it had a good performance regarding the description of SWCCs for the 12 soil textures. The soil structure could be described through fractal dimensions, which can effectively indicate soil hydraulic characteristics. The estimated fractal dimension of this model could be obtained by particle size distribution. Furthermore, using the SWCC fractal model, we found that the SWCC of coarse textured soil changed sharply in the low suction stage and its residual water content was small, and the SWCC of fine textured soil changed gently with a large residual water content. The water retention capacity followed the order clay > silty clay > sandy clay > clay loam > silty clay loam > sandy clay loam > loam > silt loam > sandy loam > silt > loamy sand > sand.

PurposeTo compare Cd removal from different soils with three washing agents recovered from sewage sludge (dissolved organic matter (DOM), soluble humic-like substances (HLS), soluble humic substances (SHS)). Also, to investigate how washing with these agents changes soil organic-matter composition (OM).Materials and methodsSandy clay loam (S1) and clay (S2) highly contaminated with Cd (300 mg kg−1) were washed with DOM, HLS, or SHS solutions at various pHs, and with various washing times and washing modes (single or double). Cd distribution and OM composition were determined (including content of humic substances (HS), fulvic fraction (FF), labile humic acids (L-HA), and stable humic acids (S-HA)).Results and discussionCd removal proceeded with pseudo-second-order kinetics. Equilibrium was reached in 30 min (S1) and 60 min (S2). DOM, HLS, and SHS removed 75–82% of Cd from S1, and 80–87% from S2. The most mobile fraction of Cd was removed after one wash. S2 retained more OM, including HS, than S1. Although washing did not change the HA/FF ratio in most variants, washing with DOM and HLS increased the percentage of L-HA in both soils. Washing with SHS increased S-HA content in both soils, but the percent content of S-HA was similar to that in the unwashed soil.ConclusionsDOM, HLS, and SHS derived from sewage sludge can effectively remediate clay and sandy clay soils highly contaminated with Cd. Washing with an SHS solution can increase the content of the most stable carbon forms (HA), which is beneficial for carbon sequestration in remediated soils.

Background and aims We studied the effect of different biochar (BC) application rates on soil properties, crop growth dynamics and yield on a fertile sandy clay loam in boreal conditions. Methods In a three-year field experiment conducted in Finland, the field was divided into three sub-experiments with a split-plot experimental design, one for each crop: wheat (Triticum aestivum), turnip rape (Brassica rapa), and faba bean (Vicia faba). The main plot factor was BC rate (0, 5 and 101 DM ha⁻¹) and the sub-plot factor was the N-P-K fertiliser rate. Soil physico-chemical properties as well as plant development, yield components and quality were investigated. Results BC addition did not significantly affect the soil chemical composition other than the increased C and initially increased K contents. Increased soil moisture content was associated with BC application, especially at the end of the growing seasons. BC decreased the N content of turnip rape and wheat biomass in 2010, thus possibly indicating an initial N immobilisation. In dry years, the seed number per plant was significantly higher in faba bean and turnip rape when grown with BC, possibly due to compensation for decreased plant density and relieved water deficit. However, the grain yields and N uptake with BC addition were not significantly different from the control in any year. Conclusions Even though BC application to a fertile sandy clay loam in a boreal climate might have relieved transient water deficit and thereby supported yield formation of crops, it did not improve the yield or N uptake.

The retention and mobility of arsenic (As) in soil depend on various physical and chemical factors. The knowledge of the sorption–desorption chemistry of As in soil is necessary for predicting the fate and behavior of As in soil environments. Therefore, this study assessed different organic (sugarcane bagasse and vermicompost) and inorganic amendments (steel slag and fly ash) for their impact on sorption–desorption of As in texturally different contaminated soils (of sandy clay (SC) and sandy clay loam (SCL) texture) to understand the effect of amendments on As retention and mobility. The results showed that the sorption data fitted well with both Langmuir and Freundlich isotherm equations. The As sorption capacity was significantly enhanced with the application of all amendments. At 30 °C, the adsorption maxima ( q max ) of SC soils enhanced to a greater extent following the order: steel slag (278 mg kg −1 ) > sugarcane bagasse (264 mg kg −1 ) > vermicompost (246 mg kg −1 ) > fly ash (242 mg kg −1 ). Whereas, in SCL, the order of q max was steel slag (145 mg kg −1 ) > sugarcane bagasse (132 mg kg −1 ) > fly ash (120 mg kg −1 ) > vermicompost (118 mg kg −1 ). Desorption index (DI) was invariably to > 1 at both temperatures with the application of amendments indicating hysteretic desorption of As. The free energy change (Δ G °) was negative in all treatments and soils (indicating a favorable sorption process) with positive entropy change (Δ S °) values. The study recommends steel slag as the most effective amendment for enhancing As (V) retention in contaminated soils, due to its higher sorption capacity compared to other amendments like sugarcane bagasse, vermicompost, and fly ash. The amendments generally improved As sorption in both soils, reducing As mobility and potentially limiting its environmental spread.

Soil salinization typically inhibits the ability of decomposer organisms to utilize soil organic matter, and an increase in soil clay content can mediate the negative effect of salinity on carbon (C) mineralization. However, the interactive effects of soil salt concentrations and properties on C mineralization remain uncertain. In this study, a laboratory experiment was performed to investigate the interactive effects of soil salt content (0.1%, 0.3%, 0.6% and 1.0%) and texture (sandy loam, sandy clay loam and silty clay soil with 6.0%, 23.9% and 40.6% clay content, respectively) on C mineralization and microbial community composition after cotton straw addition. With increasing soil salinity, carbon dioxide (CO2) emissions from the three soils decreased, but the effect of soil salinity on the decomposition of soil organic carbon varied with soil texture. Cumulative CO2 emissions in the coarse-textured (sandy loam and sandy clay loam) soils were more affected by salinity than those in the fine-textured (silty clay) soil. This difference was probably due to the differing responses of labile and resistant organic compounds to salinity across different soil texture. Increased salinity decreased the decomposition of the stable C pool in the coarse-textured soil, by reducing the proportion of fungi to bacteria, whereas it decreased the mineralization of the active C pool in the fine-textured soil through decreasing the Gram-positive bacterial population. Overall, our results suggest that soil texture controlled the negative effect of salinity on C mineralization through regulating the soil microbial community composition.

Core Ideas Meta‐analysis showed that poultry litter’s influence on crop productivity is comparable to that of inorganic fertilizer.Poultry litter’s effectiveness on crop yield is influenced by soil properties, tillage, application practice, and crop species.More positive effects were found in acidic soil compared with neutral or alkaline, in loam soil compared with sand or clay, under conservation tillage compared with conventional, by subsurface banded poultry litter compared with broadcast or incorporation through tillage.The full benefits of using poultry litter was achieved from long‐term studies, with litter improving crop yield compared with inorganic fertilizer. Research has shown that poultry litter (PL) can be used as a nutrient source for crop production. However, yield responses often varied when compared with inorganic fertilizer (IF) depending on soil type, management conditions, and PL application practices. Therefore, we reviewed the literature and conducted a meta‐analytic assessment to summarize the effects of PL vs. IF on yield response under different agricultural practices. A total of 866 observations from 90 studies were evaluated to determine how soil properties, tillage, application practices, crop species, and repeated applications influenced yield. Poultry litter significantly increased yield in loam, sandy loam, and silty‐clay loam soils, whereas yields were significantly greater with IF in sand and silty‐clay soils; no differences were observed between PL and IF with clay loams or silt loams. Under conventional tillage, IF’s effect on yield was positive, albeit not significant, whereas PL had a significant positive effect under strip‐till or no‐till. Poultry litter produced slightly lower yield when surface incorporated, but higher yield with subsurface band application when compared with IF. Poultry litter had significantly higher yield with cotton (Gossypium hirsutum L.), corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and peanut (Arachis hypogaea L.), significantly lower with bermudagrass [Cynodon dactylon (L.) Pers] than IF, and no effects on tall fescue (Festuca arundinacea Schreb.), corn silage, rice (Oryza sativa L.), and wheat (Triticum aestivum L.). Overall, PL was comparable to IF. However, the greatest benefits of PL on yield when compared to IF tended to occur following repeated (three or more) annual applications.

Climate change is a global challenge that is accelerated by contamination with hazardous substances like arsenic (As), posing threat to the agriculture, ecosystem and human health. Here, we explored the impact of various ameliorants on geochemical distribution of As in two soils with contrasting textures (sandy clay loam (Khudpur Village) and clay loam (Mattital Village)) under paddy soil conditions and their influence on the CO2-carbon efflux. The exchangeable As pool in clay loam soil increased as: lignite (0.4%) < biogas slurry (6%) < cow dung (9%), and < biochar (20%). However, in the sandy clay loam soil exchangeable soil As pool was found to be maximum with farmyard manure followed by biogas slurry, biochar and cow dung (17%, 14%, 13% and 7%, respectively). Interestingly, in the sandy clay loam soil the percentage As distribution in organic fraction was: biochar (38%) > cow dung (33%) > biogas slurry (23%) > sugarcane bagasse (22%) > farmyard manure (21%) that was higher compared to the clay loam soil (< 6% for all the amendments). In addition to the highest As immobilization by biochar in sandy clay loam soil, it also led to the lowest CO2-carbon efflux (1470 CO2–C mg kg−1) among all the organic/inorganic amendments. Overall, the current study advances our understanding on the pivotal role of organic amendments, notably biochar, in immobilizing As under paddy soil conditions with low (CO2) carbon loss, albeit it is dependent on soil and ameliorant types.

Chloramphenicol, a broad-spectrum antibiotic employed for controlling bacterial infections, presents an intriguing aspect in terms of its environmental fate in soils. 14 C-labeled chloramphenicol was used to explore its mineralization and residue characteristics in three distinct agricultural soils in China. The findings revealed a nuanced pattern in the fate of 14 C-chloramphenicol, with notable variations among the different soils under investigation. The chloramphenicol extract residue exhibited a reduction of 18.04% in sandy clay soil, 23.04% in clay loam soil, and 21.73% in loamy clay soil. Notably, the mineralization rate in sandy clay soil was 25.22% surpassed that in the other two soils, particularly during the initial stages of incubation. Over time, the diminishing extract residue underwent conversion into minerals and bound residue. The formation rate of bound residue was increased from 44.59 to 53.65% after adding 10% manure, suggesting that chloramphenicol easily binds with soils rich in organic matter. The bound residue is predominantly localized in the humin fraction across all soils. Additionally, the sterilized soil experiments indicated the pivotal role of microorganisms in influencing the fate of chloramphenicol under the specified experimental conditions. In conclusion, this study offers valuable insights into the environmental dynamics of chloramphenicol in soils, emphasizing the importance of soil composition, organic matter content, and microbial activity. The findings contribute to a scientific understanding of the environmental safety implications associated with chloramphenicol usage.

The aim of this study was to determine the effects of plant absence or presence on microbial properties and enzyme activities at different levels of salinity in a sandy clay soil. The treatments involved five salinity levels—0.5 (control), 2.5, 5, 7.5, and 10 dS m−1 which were prepared using a mixture of chloride salts—and three soil environments (unplanted soil, and soils planted with either wheat or clover) under greenhouse conditions. Each treatment was replicated three times. At the end of the experiment, soil microbial respiration, substrate-induced respiration (SIR), microbial biomass C (MBC), and enzyme activities were determined after plant harvest. Increasing salinity decreased soil microbial properties and enzyme activities, but increased the metabolic quotient (qCO2) in both unplanted and planted soils. Most microbial properties of planted soils were greater than those of unplanted soils at low to moderate salinity levels, depending upon plant species. There was a small or no difference in soil properties between the unplanted and planted treatments at the highest salinity level, indicating that the indirect effects of plant presence might be less important due to significant reduction of plant growth. The lowered microbial activity and biomass, and enzyme activities were due to the reduction of root activity and biomass in salinized soils. The lower values of qCO2 in planted than unplanted soils support the positive influence of plant root and its exudates on soil microbial activity and biomass in saline soils. Nonetheless, the role of plants in alleviating salinity influence on soil microbial activities decreases at high salinity levels and depends on plant type. In conclusion, cultivation and growing plant in abandoned saline environments with moderate salinity would improve soil microbial properties and functions by reducing salinity effect, in particular planting moderately tolerant crops. This helps to maintain or increase the fertility and quality of abandoned saline soils in arid regions.

To control outdoor exposure to natural radiation, assessment of activity concentrations of the radionuclides in soils is substantial. In this paper, the activity concentration of natural radionuclides (226Ra, 232Th, 40K) was estimated for 174 agriculture soil samples using a sodium iodide detector (NaI) of (3” × 3”). Soil samples were collected from seven regions (56 locations) in EL-Minya governorate, Upper Egypt. The variability of natural activity concentration with soil’s textures was checked. The texture types of soil samples were silt clay loam, clay loam, sandy clay loam, and sandy silt loam. The obtained results indicate that the mean values of specific activity ranged from 11.3 ± 0.5 (sandy silt loam) to 21 ± 1(silt clay loam), 6.8 ± 0.3 (sandy silt loam) to 13.7 ± 0.7 (sandy clay loam), and 112 ± 5 (sandy silt loam) to 272 ± 13.6 (sandy clay loam) Bq kg−1 for 226Ra, 232Th, and 40 K, respectively. The obtained results were compared with the global average and tolerable limits as recommended in UNSCEAR 2008. On the other side, the radiological hazard resulting from the total natural radioactivity in the studied soil samples was estimated by different approaches. The obtained values were within the recommended safety limit and do not pose significant radiation hazards.