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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.

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.

Desertified land covers one-fourth of the world’s total land area. Meeting the high food demands in areas affected by desertification is a major problem. This case study provided fundamental information to demonstrate the potential for utilizing the desertified land. The soybean trial was established in two sandy clay loam soils (desertified land) and one silty clay loam soil. Two types of biochar were applied as treatments. We aimed to investigate the response of soybean plants to soil structure, soil nutrient condition, and biochar amendment in the two types of soil. In addition, ridge regression was employed to model the plant growth indicators by soil structure, soil nutrients condition, soil water content, and biochar amendment. We conclude that (1) overall soil productivity in sandy clay loam soil is lower than in silty clay loam soil. The sandy clay loam soil may have high efficacy for crop production due to its higher harvest index. (2) Aggregate size 0.5–1 mm, 1–2 mm, and 2–3 mm indicated more important in plant biomass formation in silty clay loam soil. The low aggregate stability of sandy clay loam soil made the field more vulnerable to wind erosion in the semi-arid monsoon climate. (3) Cob biochar and wood biochar increased soybean shoot biomass by 48.7% and 45.0% in silty clay loam soil. (4) The higher N-fixing ability of nodules in sandy clay loam soil indicates an advantage to reduce the use of N-fertilizers in desertified areas. (5) Exponential polynomial regression ameliorated the accuracy of prediction of plant growth indicators in comparison to linear regression.

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.

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.

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.

Alternative storm water management focuses on channeling rainwater to underground reservoirs, decreasing the surface flow, and reducing the load of wastewater treatment systems in urban planning. However, soil permeability is a major hindrance to alternative management techniques. Increasing soil permeability is necessary to manage rainwater harvesting and increase groundwater recharge. Additionally, earthworm density directly affects soil properties. In this study, we investigated the effects of earthworm density and species on the permeability of clay loam soil by a gravity-driven film flow. We conducted indoor and outdoor experiments by installing boxes/tanks with layers of materials (gravel, textile, clay loam soil, and organic matter). In the indoor experiments (IE), these materials were used to feed individuals of Lumbricus terrestris with an initial density of 25/m², 50/m², 100/m² while the outdoor experiments (OE) had the initial density of 108/m². All experiments were conducted in triplicate. The permeability velocity was measured using the gravity-driven film flow method with a flow rate of 1 cm/unit time. The coefficient of determination R² of 0.86, 0.93, 0.93 between infiltration velocity and time variable was determined using the data on the initial earthworm density in the IE in one year. Moreover, the growth percentage of L100 was the highest value at 1347% in 391st days. Meanwhile, in the OE, compared to the OE with two earthworms ( Lumbricus terrestris and Aporrectodea caliginosa ), the infiltration velocity of contained tanks by A. caliginosa were significantly greater than the ones by L. terrestris at 289% and 155%, respectively. The coefficient of determination R² of 0.89, 0.89, 0.98 between infiltration velocity and time variable was collected by the initial presence of two earthworm species for one year. The results of the experiment showed that burrowing earthworms can significantly facilitate the infiltration velocity of clay loam soil, and the density of earthworms was found to affect the capacity of permeability, based on the gravity-driven film flow methodology. This also illustrates that the two functional groups have different interactions with the infiltration velocity. Data provided in this study could be used to apply the functional earthworms in ameliorating the alternative techniques in stormwater management systems.

An accurate mathematical representation of particle‐size distributions (PSDs) is required to estimate soil hydraulic properties or to compare texture measurements from different classification systems. The objective of this study was to evaluate the ability of seven models (i.e., five lognormal models, the Gompertz model, and the Fredlund model) to fit PSD data sets from a wide range of soil textures. Special attention was given to the effect of texture on model performance. Several criteria were used to determine the optimum model with the least number of fitting parameters when other conditions are equal. The Fredlund model with four parameters showed the best performance with the majority of soils studied, even when three criteria that impose a penalty for additional fitting parameters were used. Especially, the relative performance of the Fredlund model in regard to other models increased with increase of clay content. Among all soil classes, the lognormal models with two or three parameters showed better fits for silty clay, silty clay loam, and silt loam soils, and worse fit for sandy clay loam soil.

Soil plays a pivotal role in enhancing global water and food security. Irrigation water constitutes more than 70% of the global water demand. The anticipated demographic increase and changing climate will impose more pressures on the global water and food systems. Therefore, and to achieve the target of “more crop per drop per area”, water management plans must be based on more accurate quantitative and dynamic approaches. It is increasingly obvious that the unique aggregates structure of the soil medium regulates water and nutrient circulations, and consequently defines soil and water health, productivity, and water use efficiency. However, the soil aggregates structure is not currently well considered in the quantification of soil–water holding properties. The authors applied a thermodynamic and soil structure-based approach to quantify soil–water holding properties. Specifically, the paper aims at providing a methodology, based on the pedostructure concept, to quantify field capacity (FC), permanent wilting point (PWP), and plant available water (AW). Pedostructure is a representative aggregates unit of a soil horizon that describes the structural organization of the soil medium. Four types of soil were analyzed considering various soil texture and aggregates structure: loamy fine sand, silt loam, clay loam, and silty clay loam. The calculated values for FC and PWP, based on the proposed pedostructure method, were compared with the recommended values by the standard FAO method and soil suction method. Results showed good agreement between the calculated values of the two methods. The proposed pedostructure method introduces a shift in quantifying the plant available water from a texture-based estimation to a soil aggregates structure-based calculation. Such a shift will enable capturing the changes in soil aggregates structure due to agro-environmental practices and the associated impact of these changes on soil–water holding properties.

Purpose The potential of industrial hemp ( Cannabis sativa L.) for phytoremediation of copper-contaminated Mediterranean soils was investigated. The accumulation of copper in hemp’s parts and the effect of contaminated soil on the production of cannabidiol (CBD) were, also, of primary concern. Methods Two soil types, a Clay Loam & a Sandy Clay Loam, were exposed to two levels of Cu contamination, with low & high Cu concentrations. The soils’ total and available Cu content, along with Cu in plant tissues, were determined. Height, fresh aboveground biomass and leaf chlorophyll content were further evaluated. Furthermore, the amount of cannabidiol (CBD) in the hemp flowers was determined. Results Hemp appeared to be highly resistant, as can successfully grow in both soil types having low or high Cu levels. The maximum Cu content was detected in the highest part of the plant roots, with a progressive decline towards the upper parts of the plant (CuRoots > CuShoots > CuLeaf), in both soil types. It has been observed that more than 50% of the plant’s copper concentration is accumulated in the roots. Furthermore, the hemp plants cultivated in high Cu-contaminated soils produced greater amounts of cannabidiol (CBD). Conclusion Ηemp proved to be a promising plant for phytostabilization in Cu-contaminated soils, as its above-ground biomass is almost free of metals and can be used further for fiber production. The presence of Cu in soils did not appear to disrupt the production of the important secondary metabolite CBD, but rather increased following increasing soil Cu content. Graphical Abstract