Biochar is an efficient amendment to improve soil quality and crop productivity, but the potential of biochar as a substitute for chemical fertilizers is still unknown. Here we conducted a 6-year ...field experiment to investigate how partial substitution of biochar to NPK fertilizers affect soil quality and rice yield in the northeast of China. The experiment included three treatments: Control (B0: NPK fertilizers only: 240 kg N ha−1, 52 kg P ha−1, and 100 kg K ha−1); Low-input biochar (B1.5: 95% N, 89% P, 75% K + 1.5 t biochar ha−1 year−1); and High-input biochar (B3.0: 90% N, 78% P, 50% K + 3.0 t biochar ha−1 year−1). The amounts of NPK application in the biochar treatments were determined according to an equivalent method. We evaluated the soil pore structure characteristics via a CT technology, and investigated soil nutrients, plant biomass, root growth, and grain yields. The results showed that, after the 6-year application, the soil pore structure and rice productivity of B1.5 were significantly improved in compared to those of B0 and B3.0. B1.5 had similar soil available NPK contents, but 6.6% higher rice yield as compared to B0, because of increased root length density (33.2%) and aboveground biomass (10.2%). B1.5 also increased soil macroporosity (>100 μm) (141.4%), fraction dimension (8.4%), and pore connectivity (16.6%) in compared with those of B0. However, B3.0 showed the lowest rice yield due to lower soil available N content (19.2%), macroporosity (28.5%), fraction dimension (5.5%), and pore connectivity (85.3%) than B0. This study demonstrated that a moderate NPK fertilizer replacement by biochar could be an effective practice that improves soil quality, increases rice growth and yield, and reduces the input of chemical fertilizers for rice production.
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•This study was based on a 6-year biochar application experiment in paddy soil.•1.5 t ha−1 of biochar maintained sufficient soil nutrients and improved pore structure.•1.5 t ha−1 of biochar increased rice productivity, but inverse in 3.0 t ha−1.
Biochar is a valuable soil amendment and is recognized to have a positive effect on the crop yield, soil quality, nutrient cycling, and carbon sequestration. However, the effect depends on biochar ...characteristics, doses, and soil properties. This paper reports the study on determination of the effect of different rates of biochar based on their size fractions on water retention characteristic of sand-based rootzone mixture characteristic for natural turfgrass rootzone.
The pot experiment was established using a soil with the texture of loamy sand. Mixtures of biochar and soil were prepared in March 2014. Biochar was produced using the straw of two species, namely miscanthus and winter wheat, by pyrolysis process at a temperature of 300°C for 15min with limited air access. Then, biochar particles were separated into three size fractions as follows: 0–500μm, 500–1000μm, and 1000–2000μm. The following four biochar rates were used in this experiment: 0.5%, 1%, 2%, and 4%.
The results indicated that biochar application significantly improved the physical properties of the tested sandy soil. The basic soil physical parameters, such as bulk density and total porosity, were not only dependent on the rate but also on the size of the biochar. Small particles of biochar reduced the volume of soil pores in diameter below 0.5μm but increased the volume of larger pores with a diameter 0.5–500μm. Biochar application increased the available water content (AWC), especially when the finest fraction was used (0.064cm3cm−3). Biochar made of miscanthus was characterized by higher AWC (0.056cm3cm−3) than that made of winter wheat (0.050cm3cm−3). In the present study, the soil water repellency was increased by biochar application, but it was still classified as non-repellent.
•Effect of rates and size of biochar particles on physics of sandy soil was investigated.•Soil physical parameters were dependent on the feedstock, rate, and particle size of the biochar.•Biochar application increased the available water content.•Soil water repellency was increased by biochar.
•Biochars pyrolyzed at different temperatures affect differently soil pore characteristics.•RSB increased total pore volume (TPV) in soil, while CSB decreased soil TPV.•Biochar altered the pore size ...distribution of soils, differing with soil type and feedstock.•RSB promoted the formation of 0.1–30 μm pores, and CSB increased 0.1–5 μm pores in soils.•Biochars made at 450 °C was the optimal for improving soil pore characteristics.
Soil physical properties are potentially affected by the addition of biochar. The effect is largely determined by the pore characteristics of biochar, especially the biochar’s feedstocks and pyrolysis processes. This study examined the pore characteristics of rice straw biochars (RSB) and canola stalk biochars (CSB) produced at pyrolysis temperatures of 250, 350, 450, 550, and 650 °C, and evaluated the effects of biochars on soil pore properties. The pore characteristics of biochars were characterized by nitrogen adsorption isotherm (NAI), mercury intrusion porosimetry (MIP), and scanning electron microscope (SEM). Each biochar was mixed into two soils (Ultisol and Alfisol) at the rate of 1% (w/w), then the soil-biochar mixtures were incubated for 90 days. The specific surface area (SSA) and total pore volume (TPV) measured by NAI technique increased with increasing pyrolysis temperature of biochar. Biochars pyrolyzed at 450 °C had the highest porosity and TPV measured by MIP. The largest pore class for RSB was the macropore (>75 μm), while the main pore classes for CSB were micropore (5–30 μm) and ultramicropore (0.1–5 μm). Incubation experimental results showed that biochar addition altered the pore size distribution of the Alfisol and Ultisol. RSB enhanced the total porosity and microporosity of soils, whereas CSB decreased total porosity, macroporosity, and mesoporosity. The water-holding capacity of soil was increased by increasing the amount of soil storage pores caused by biochar. Heatmap analysis on the correlation among pyrolysis temperature of biochar, pore characteristic and water retention capacity of biochar-amended soils illustrated that the pore properties of the Ultisol amended with CSB and the water properties of the Alfisol with CSB were highly correlated with pyrolysis temperature of biochar. Our results suggested the meso- and micro-pores in biochars played an important role to affect the soil response to biochar addition. Based on pore properties, pyrolysis temperature around 450 °C was found to be the optimal condition for producing porous biochar with larger porosity.
•We evaluated soil physical properties in 0–30cm depth•We evaluate how no-tillage would affect the soil physical properties.•Soil Physical quality has maintained after more than two decades in ...no-tillage systems.•The soil chiselling is dispensable in no-tillage systems.•The no-tillage is the best systems for climate subtropical regions.
Sustainability of crop production systems depends on the preservation of soil physical quality over time. This study aimed to determine long-term effects of soil tillage and cropping systems on physical attributes and hydraulic properties of an Oxisol in Southern Brazil, emphasising management practices to preserve or improve the soil structure quality under no-tillage system. The experiment was conducted in randomized block design, using a 5×2 factorial arrangement (tillage×cropping systems), with four replications. The five tillage systems consisted of conventional tillage (CT); minimum tillage, chiselled soil every year (MTC1); minimum tillage, chiselled soil every three years (MTC3); continuous no-tillage for 11 years (NT11); and continuous no-tillage for 24 years (NT24). The two cropping systems consisted of annual crop sequence with wheat in the winter and soybean in the summer, designated as crop succession (CS); and a 4-year crop rotation (CR) with white lupine-maize—black oat-soybean—wheat-soybean—wheat-soybean in winter–summer, respectively. Undisturbed soil cores were collected from 0–0.10; 0.10–0.20 and 0.20–0.30 m of soil depth, to determine the soil bulk density (BD), total porosity, macroporosity, microporosity, pore size distribution and classes, soil water retention curve, infiltration rate and field-saturated hydraulic conductivity. There was no interaction between tillage and cropping systems, and no effects of cropping systems on soil physical and hydraulic properties. Regardless the cropping system, chiselling effects on soil physical properties persisted for less than 22 months, and were restricted to below 0.20m soil depth. The CT resulted in soil pulverization at 0–0.10 m depth, leading to lower BD and higher macroporosity compared to the other soil tillage systems. At layers below 0.10m, CT increased the BD and reduced the macroporosity to critical levels for crop growth. Continuous use of no-tillage improved soil physical quality mainly at deeper layers, and provided higher plant available water retention in the soil at matric potentials ranging from −10 to −200kPa in relation to CT and MTC1. The adoption of NT improves soil physical quality and plant available water over time, and periodic soil chiselling aiming to disrupt compacted layers should be avoided because of its effects on reducing soil compaction level are short-lived.
•A model is built for the effective electrolyte diffusion in porous media.•Effects of microstructural and electrokinetic parameters are analyzed.•Good agreement between our present model and results ...is observed.
Electrolyte diffusion in electrolyte solutions exists in various areas including rechargeable batteries, soil physics and chemical engineering. In this paper, a fractal model based on the capillary model and fractal theory of porous media is proposed to quantify the effective electrolyte diffusivity in porous media with consideration of the electrical double layer (EDL) effects. The present model explicitly relates to the micro-structural parameters of porous media and electrokinetic parameters. To validate this model, a comparison is carried out with experimental data and semi-analytical model results, and yields satisfying agreement. Besides, the influences of the parameters (the porosity, equivalent particle diameter, ratio of the minimum pore radius to the maximum pore radius, molar concentration, zeta potential, and dimensionless parameter β) are discussed in details.
Biochar is a pyrogenous, organic material synthesized through pyrolysis of different biomass (plant or animal waste). The potential biochar applications include: (1) pollution remediation due to high ...CEC and specific surface area; (2) soil fertility improvement on the way of liming effect, enrichment in volatile matter and increase of pore volume, (3) carbon sequestration due to carbon and ash content, etc. Biochar properties are affected by several technological parameters, mainly pyrolysis temperature and feedstock kind, which differentiation can lead to products with a wide range of values of pH, specific surface area, pore volume, CEC, volatile matter, ash and carbon content. High pyrolysis temperature promotes the production of biochar with a strongly developed specific surface area, high porosity, pH as well as content of ash and carbon, but with low values of CEC and content of volatile matter. This is most likely due to significant degree of organic matter decomposition. Biochars produced from animal litter and solid waste feedstocks exhibit lower surface areas, carbon content, volatile matter and high CEC compared to biochars produced from crop residue and wood biomass, even at higher pyrolysis temperatures. The reason for this difference is considerable variation in lignin and cellulose content as well as in moisture content of biomass. The physicochemical properties of biochar determine application of this biomaterial as an additive to improve soil quality. This review succinctly presents the impact of pyrolysis temperature and the type of biomass on the physicochemical characteristics of biochar and its impact on soil fertility.
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•Pipeline construction on cropland negatively impacts soil physical attributes.•Physical properties improved with increasing time elapsed since completion of reclamation.•Recovery of ...saturated and near-saturated hydraulic conductivity within 6.5 to 12.5 years.•Effective macroporosity will require more than 12.5 yr to recover.•Aggregate stability appeared to have recovered within 4.5 yr of reclamation.
Underground oil and natural gas pipeline rights-of-way (ROWs) sometimes traverse croplands, leaving behind tracts of disturbed land characterized by poor productivity even after reclamation. This study investigated temporal post-reclamation changes in soil penetration resistance (PR), field saturated hydraulic conductivity (Kfs), near-saturated hydraulic conductivity (KΨ), soil pore indices, and wet aggregate stability (WAS) on natural gas pipeline ROWs on cropland. These attributes were measured in two fields in late summer of 2021 and 2022. Across the two fields, three ROWs that had been reclaimed four to thirteen years prior (i.e., time since reclamation (TSR) of 4 to 13 yr) were assessed along with adjacent undisturbed (off-ROW) transects located 50 m from the ROWs. Measurement locations on each ROW and on off-ROW were 25 m apart. Samples for WAS were collected from the 0–15 cm layer. The results showed a significant (p < 0.05) TSR by soil depth interaction for PR. Treatments were not significantly different in the 0- to 20-cm and 40- to 60-cm layers, but in the 20- to 40-cm depth interval, PR was 57.7–64.2 % greater on the 4.5-yr ROW than on off-ROW. Saturated hydraulic conductivity was three to four times lower on the 4.5- and 6.5-yr ROWs than on the off-ROW. Near-saturated hydraulic conductivity on the 4.5-yr ROW was 61.6 % lower than that on the off-ROW, while no significant differences were detected between the 6.5-yr and 12.5-yr ROWs and the off-ROW. Effective water conductive macroporosity was 72.5 % lower on the 4.5-yr ROW than on the off-ROW. All measured physical properties improved with increasing TSR. These results indicate a significant but slow recovery in soil physical attributes with increasing TSR of ROWs on cropland. This has implications on the productivity of these ROWs as crop yields, which depend on these soil physical properties, are also expected to recover slowly.
Soil hydraulic conductivity is a property that describes how easily water can move through a porous space and its determination is important because it controls many soil hydrological processes. The ...objectives of this work were: i - to assess the suitability of lab tension mini-infiltrometry to measure hydraulic conductivity, by comparing with field tension disc infiltrometer data; and ii - to assess the effect of different tillage practices on hydraulic conductivity values and pore network in three different soils from Argentinean Pampas Region. Additionally, three analytical approaches to obtain K from mini-infiltrometry data were compared. Field infiltration with tension disc infiltrometer (TI) and laboratory infiltration with a proposed mini-infiltrometer (MI) were conducted in three different textured soils of Argentinian Pampas Region (loam, silty loam and sandy loam) in long-term experiments under no-tillage (NT) and conventional tillage (CT). Hydraulic conductivity (K) at different tensions (h) (6, 3 and 0 cm), namely K6, K3 and K0, and soil pore connectivity were estimated. There was no significant difference between K (h) values obtained from TI and MI, ranging between 0.47 and 2.36 cm h−1 and 0.52 and 1.77 and cm h−1, respectively. We concluded that NT reduces soil hydraulic conductivity, affecting soil pore connectivity, especially in fine textured soils. CT showed higher total pore connectivity in all studied sites. The proposed laboratory mini-infiltrometry method allows determining soil hydraulic conductivity function and pore connectivity in a simple, fast and inexpensive way.
•Laboratory mini-infiltrometry method was used to measure hydraulic conductivity.•Hydraulic conductivity values were comparable with field tension infiltrometer.•Pore connectivity was reliably determined using mini-infiltrometry data.•Conventional tillage promotes higher values of hydraulic conductivity.
·Random distribution of the inclusions in a composite material is simulated by a finite element model.·Effective thermal conductivity is calculated through finite element method.·Proposed numerical ...procedure is validated by experimental results and compared to empirical model results.
Many materials (e.g. soil) are multi-phase composites in engineering, and the thermal conductivity of mixtures is a critical parameter for analyzing the temperature field. Owing to its heterogeneity, the effective thermal conductivity of multi-phase materials is also not deterministic. The prediction of the thermal properties of a multi-phase material remains a challenging task. In this study, soil is considered to be a typical multi-phase material. A numerical simulation model is established by the finite element method to predict the meso-scale effective thermal conductivity of soil. Monte Carlo simulation is employed to account for the random distribution of voids. Comparisons among numerical, experimental and empirical results suggest that the proposed model can predict reasonably accurate results. In addition, the effective thermal conductivity of unfrozen soil, partially frozen soil and fully frozen soil is calculated. The effects of soil type, porosity and saturation degree on effective thermal conductivity are considered via parametric studies. The proposed numerical method can be used as an effective supplement to empirical model and experimental tests for evaluating the thermal conductivity of multi-phase materials.
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