Soil Bulk Density Research Articles

Characteristics of the Soil Organic Carbon Pool in Paddy Fields in Guangdong Province, South China

To understand the role of paddy soils in the global carbon cycle, it is necessary to analyze the characteristics of the organic carbon pool at different soil depths. It was hypothesized that soil organic carbon fractions including labile organic carbon fraction I (LOCF-I), labile organic carbon fraction II (LOCF-II), and recalcitrant organic carbon (ROC) distributed differently within the soil profile. In this study, soil was collected from 27 typical rice fields in Guangdong Province, south China. The carbon fractions of the paddy field soils were analyzed and compared over a 0–60 cm depth profile. The relationship between carbon content and the physical and chemical properties of the soils was further analyzed using correlation analysis and structural equation modeling. The results showed that soil total organic carbon concentration in paddy fields was increased by 22.1% during the last four decades. In the soil organic carbon pool of 0–60 cm profile, the proportion of 67.31 to 70.31% in ROC, 21.75 to 22.06% in LOCF-I, and 7.7 to 10.63% was recorded, respectively, indicating that ROC was the dominating fraction. Storage of soil total organic carbon and fractions all decreased with the increase in soil depth. Correlation and path analysis showed that total nitrogen was the main driving factor affecting the soil carbon fractions, whereas pH and soil bulk density indirectly affected the content of carbon fractions by influencing total nitrogen. The results imply the importance of soil total nitrogen in paddy carbon management of rice cultivation.

Trade-Offs in Plant Functional Traits Driven by Soil Changes under Urban Hardened Surfaces

The large-scale surface hardening has changed the urban environment and affected the normal growth of urban plants. However, it is still unclear how the urban hardened surface affects the functional urban plant traits. To explore whether the urban hardened surface affects the ecological strategies of plants by changing the urban soil properties and reflecting them on the plant traits, we studied the physical and chemical properties and plant functional traits of three different types of hardened surface in Shandong Province, China. Our results showed that the physical and chemical properties (soil bulk density, soil total porosity, capillary porosity, non-capillary porosity, soil moisture content, pH, organic carbon, total nitrogen, total phosphorus, total potassium, available phosphorus, and available potassium) of urban soils showed obvious differences with the increase of hardening strength. In this case, the plant functional traits (branch diameter, branch length, leaf thickness, branch weight, internode length, leaf dry weight, leafing intensity, leaf area, specific leaf area, and leaf dry matter content) were also differentiated to varying degrees. Meanwhile, there was a strong correlation among plant functional traits. Nevertheless, hardened surfaces break the quantitative relationship among functional traits of urban trees. They do not affect their stable correlation: as the hardening intensity gradually increases, its correlation weakens. In addition, plant functional traits have a significant response mechanism to soil physicochemical properties. There was a transformation of plant resource utilization strategy by changing plant functional traits to adapt to the hardened environment. Urban trees exhibit strong and rapid resource-allocation strategies. They are mainly reflected in the reduction of branch diameter, branch weight, leaf dry matter content, leaf area, mass ratio of branches and leaves, and the improvement of leafing intensity and leaf thickness. Overall, there were tight connections among urban soil properties, plant branches, and leaves functional properties. This finding reveals that urban trees can change their functional traits and the plasticity of their trait combinations under the background of hardened urban surface expansion, which is conducive to survival and growth.

Ecosystem multifunctionality is more related to the indirect effects than to the direct effects of human management in China's drylands

Drylands provide a wide range of important ecosystem functions but are sensitive to environmental changes, especially human management. Two major land use types of drylands are grasslands and croplands, which are influenced by intensive grazing activities and agricultural management, respectively. However, little is known about whether the ecosystem functioning of these two land use types is predominated affected by human management, or environmental factors (intrinsic environmental factors and factors modified by human management). This limits our understanding of the ecosystem functions under intensive human management in drylands. Here we reported a study where we collected data from 40 grassland and 30 cropland sites along an extensive aridity gradient in China's drylands to quantify the effects of human management intensity, intrinsic environmental factors (i.e., aridity), and environmental factors modified by human management (i.e., soil bulk density and plant density) on specific ecosystem functions (ecosystem multifunctionality, productivity, carbon storage, soil water, and soil nutrients). We found that the relative importance of each function differed between croplands and grasslands. Ecosystem functions varied with human management intensity, with lower productivity and plant carbon storage in grasslands under high grazing intensity than un-grazed, while multifunctionality and carbon storage increased with greater fertilization only in arid croplands. Furthermore, among environmental factors, soil bulk density had the greatest negative effects, which directly reduced multifunctionality in grasslands and indirectly reduced multifunctionality in croplands via suppressing crop density. Crop density was the major environmental factor that positively related to multifunctionality in croplands. However, these effects would be exacerbated with increasing aridity. Our study demonstrated that compared with the direct impacts of human management, environmental factors modified by human management (e.g., soil bulk density) are the major drivers of ecosystem functions, indicating that improving soil structure by alleviating human interferences (e.g., reducing livestock trampling) would be an effective way to restore ecosystem functions in drylands under global warming and drying.

The potential of soil endemic microorganisms in ameliorating the physicochemical properties of soil subjected to a freeze-thaw cycle

Establishing soil biological crusts will result in the long-term restoration of ecosystems. Nonetheless, little research has been conducted to demonstrate the influence of soil endemic microorganisms on suppressing the adverse effects of freezing-thawing on soil properties. This current study evaluated the formation of biological crusts, the enhancement of physical and chemical characteristics of soil, and surface soil stability by inoculating native bacteria and cyanobacteria into the soil during a freezing-thawing cycle. The soil was collected from the Badranlou Region in North Khorasan Province, Northern Iran, and native bacteria and cyanobacteria were isolated, identified, chosen, and cultured. The native treatments of bacteria and cyanobacteria were then inoculated in individual bacteria, cyanobacteria, and combined inoculation of cyanobacteria and bacteria onto an experimental soil in six replications. After 60 days, they were subjected to freezing-thawing conditions to have maximum effect on the soil environment, and finally, the soil surface properties were statistically compared. The results of the significant effect (p<0.001) of inoculation treatments on the physical and chemical properties of the study soil revealed that the carbon, nitrogen, organic matter, phosphorus, potassium, and surface soil stability in bacterial treatment compared to the control treatment increased by 68, 39, 68, 17, 25, 99 %, respectively. While under cyanobacterial treatment, they rose by 83, 61, 83, 18, 73, and 172 %, respectively. The combination inoculation treatment of bacteria and cyanobacteria enhanced the study variables by 73, 66, 73, 25, 58, and 189 %, respectively. Compared to control plots, the soil bulk density in bacterial, cyanobacterial, and compound inoculation treatments was substantially reduced (p<0.001) by 9, 15, and 12 %, respectively. The soil stability, carbon, and organic matter were among the most essential properties of the soil, and they best showed the difference between the various treatments applied. It confirmed the region's potential restoration by inoculating native soil microorganisms.

Liming and phosphate fertilization influence soil fertility, physical properties, and carbon stock in a subtropical Ferralsol in Brazil

Understanding the effects of liming plus phosphate fertilization on soil physical and chemical properties, as well as carbon stock, is critical for improving soil fertility management under conventional till (CT) and no-till (NT) systems. This study aimed to quantify changes in these soil properties resulting from incorporation (CT) or not (NT) of limestone and phosphorus (P) in a subtropical Ferralsol in southern Brazil. The experiment was conducted in Campo Mourão, Paraná State, Brazil, according to a randomized complete block design with a 6 × 4 factorial arrangement and four replications. The treatments comprised six strategies for limestone and P management and four soil depth layers (0–0.05, 0.05–0.10, 0.10–0.20 and 0.20–0.40 m), as follows: NLNT - no liming under no-till; NLCT - no liming under conventional till; LPNT - liming and P fertilization under no-till; LPCT - liming and P fertilization under conventional till; LNT - liming under no-till; and LCT - liming under conventional till. In 2012, 5.0 Mg ha−1 dolomitic limestone and 53.3 kg ha−1 P were applied. In 2016, dolomitic limestone was reapplied to a soybean–wheat rotation. Liming and liming plus P treatments influenced soil properties up to a depth of 0.10 m, increasing pH and decreasing Al3+, without significant differences between CT and NT. Higher levels of Ca2+ and Mg2+ were observed at 0–0.05 m, except in unlimed treatments. Liming and liming plus P fertilization treatments resulted in mean increments of 1.83 and 1.37 cmolc dm−3 in Ca2+ and Mg2+ levels, respectively, regardless of the tillage system. Base saturation did not differ between treatments in the 0.10 m layer. However, LPCT resulted in higher base saturation in the 0.10–0.20 m (55 %) and 0.20–0.40 m (53 %) layers. P contents were affected up to 0.10 m depth, being 30 % higher in LPNT than in LPCT at 0–0.05 m. In the 0–0.05 m layer, soil bulk density was highest in NLCT and LPCT, and macroporosity was lowest in LPCT. Carbon stock was not affected by tillage practices, liming, or P fertilization. There was a positive correlation between P content and carbon stock at 0.20–0.40 m, suggesting that increased P availability at depth contributes to carbon sequestration. At 0–0.05 m, soil physical properties were negatively influenced by the combined application of liming and P fertilization under CT, indicating possible simultaneous effects on clay dispersion and pore obstruction.

Soil properties predict below-ground community structure, but not nematode microbiome patterns in semi-arid habitats.

Microbial and microeukaryotic communities are extremely abundant and diverse in soil habitats where they play critical roles in ecosystem functioning and services that are essential to soil health. Soil biodiversity is influenced by above-ground (vegetation) and below-ground factors (soil properties), which together create habitat-specific conditions. However, the compound effects of vegetation and soil properties on soil communities are less studied or often focused on one component of the soil biota. Here, we integrate metabarcoding (16S and 18S rRNA genes) and nematode morphology to assess the effects of habitat and soil properties shaping microbial and microeukaryotic communities as well as nematode-associated microbiomes. We show that both vegetation and soil properties (soil bulk density) were major factors structuring microbial and microeukaryotic communities in semi-arid soil habitats. Despite having lower nutrients and lower pH, denser soils displayed significantly higher alpha diversity than less dense soils across datasets. Nematode-associated microbiomes have lower microbial diversity, strongly differ from soil microbes and are more likely to respond to microscale variations among samples than to vegetation or soil bulk density. Consequently, different nematode lineages and trophic groups are likely to display similar associated microbiomes when sharing the same microhabitat. Different microbiome taxa were enriched within specific nematode lineages (e.g. Mycobacterium, Candidatus Cardinium) highlighting potentially new species-specific associations that may confer benefits to their soil nematode hosts. Our findings highlight the importance of exploring above- and below-ground effects to assess community structure in terrestrial habitats, and how fine-scale analyses are critical for understanding patterns of host-associated microbiomes.

Achieving SOC Conservation without Land-Use Changes between Agriculture and Forests

Global land-use changes impact soil’s ability to perform essential functions. This study investigates whether soil organic carbon (SOC) can be conserved without altering land use in traditional farming systems and degraded natural forests, focusing on ‘disturbed’ agricultural soils and ‘undisturbed’ forest soils. We also examine the influence of dominant crops on SOC within the top 30 cm of soil in data-deficient regions of Nepal. Using a multi-stage cluster sampling design, we tested 12 regression models to identify the best relationships among variables such as SOC, soil bulk density (BD), pH, dominant crops, climate, topography, and management practices. Our analysis revealed similar SOC levels in both disturbed and undisturbed soils, indicating significant degradation in forested areas, whereas traditional farming systems could support SOC and preserve farm-based indigenous knowledge alongside food security. Further, SOC stocks varied significantly (p &lt; 0.05) across different cropping systems, suggesting that managing dominant crops could be a strategy to optimize SOC, with these crops serving as indicators. Additionally, our results show that the weak linear correlation between SOC and BD in regularly disturbed soils, such as farmlands, where anthropogenic activities frequently alter soil bulk density, may be misleading when estimating bulk density-dependent SOC. This finding suggests the need for further research into varying degrees of anthropogenic disturbance in soil to confirm these results. While the site-specific nature of the findings warrants caution with respect to generalization, they provide valuable insights for carbon monitoring, climate actions, ecosystem health, and land-use management in similar traditional farming systems and degraded forests, particularly in data-poor regions.

Improved stabilization of loess soil using magnesium oxysulfate cement-based ecological composite binder

The technology of loess solidification plays a crucial role in addressing issues such as soil erosion, with the key material in this process being the loess stabilizer. To tackle the high energy consumption problem associated with traditional loess stabilizers primarily composed of Portland cement, this study employed a more ecological sustainable alternative by incorporating solid waste coal gangue and magnesium oxysulfate (MOS) cement as a binding agent for consolidating loess. The alterations in bulk density, porosity, mineral structure, and microstructure of the consolidated soil with different MOS content were systematically investigated and validated. The pore size of MOS-solidified loess decreased significantly to a range of 0.04–3.60 μm compared to 0.80–3.88 μm for pure loess. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and thermogravimetric (TG/DTG) analysis revealed that the addition of MOS binder generated hydrated magnesium silicate (M-S-H), Mg(OH)2, and a small amount of 5Mg(OH)2·MgSO4·7H2O phase which filled the gaps between soil particles and bonded them together effectively. When the proportion of MOS binder added reached 11 %, the compressive strength of stabilized loess after curing for 28 days increased up to 9.4 MPa. After immersion in water for 24 h, the strength only decreased by 5.3 %, with a softening coefficient of 94.7 %. The test results consistently indicate that the enhancement in mechanical properties can be attributed to the binding effect facilitated by MOS. The ecological composite binder based on coal gangue and MOS demonstrates great potential in the field of soil stabilization.

Environmental role of different‐aged pine and oak stands growing on post‐agricultural and forest lands in forming the Mesostigmata mites communities

AbstractReclamation of agricultural soil and forest succession after afforestation proceeds slowly and at many levels. Therefore, the history of land use is recorded in the soil's physical, chemical and ecological parameters for many decades. This process depends on time and the form of afforestation, which primarily includes tree species. In our study, we analyzed differences in the physical and chemical characteristics of pine and oak stands on forest and post‐agricultural land at 22, 42 and 62 y/o. Our study revealed that 14 of 24 examined parameters (litter pH, soil pH, litter thickness, soil organic matter, Corg, bulk density, C/N ratio, soil moisture, soil K, Mg and Mn content, N and Ca litter content, Mg litter content) differed significantly among examined habitats (land use, stand age and tree species). We calculated the abundance, species richness and diversity of the mite communities (Acari, Mesostigmata) for each habitat type. In total, 6730 mites were classified into 72 taxa (60 species, 11 genera and one taxon as family). The highest abundance was recorded in 42 y/o. oak stands on post‐agricultural land, while the lowest is in 22 y/o. pine and oak stands on post‐agricultural land. The highest species richness and diversity were recorded in the oldest oak stand on post‐agricultural land. In contrast, the lowest diversity was recorded in the youngest oak and pine stands on post‐agricultural land. Our results demonstrate that the negative impact of the agricultural history of land use weakens over time and provides a better understanding of land use history on the relations between the soil environment and soil fauna, including mesostigmatid mite assemblages.

Sustainable soil health and agricultural productivity with biochar-based indigenous organic fertilizers in acidic soils: insights from Northwestern Highlands of Ethiopia

Depletion of soil fertility in tropical regions is a pressing concern contributing to lower crop yields. This study aimed to evaluate the effects of biochar and co-composted biochar on acidic soil and the growth performance of teff (Eragrotis teff (Zucc.)) in the sub-tropical highlands of Ethiopia. Co-composted biochar was produced by mixing Acacia decurrens biochar with chicken litter and cow dung manure at different ratios of 100:0:0, 25:75:0, 15:85:0, and 25:0:75. Treatment impact on soil properties and crop yields were evaluated with applications of 0, 5, 10, and 20 t ha–1 in field trials. The study shows interaction effects of biochar-based amendments significantly (P < 0.001) improved soil bulk density (g/cm3), moisture content (%), pH, total nitrogen (%), total organic carbon (%), available phosphorus (mg/kg), cation exchange capacity (cmol ( +)/kg)) and teff yield. The application of 20 t ha–1 sole biochar significantly improved soil acidity by 0.99 units. Soil treated with 20 t ha–1 of BCLL and BCM resulted in notable increases in soil pH, ranging from 0.12 to 0.83 units for BCLL and 0.15 to 0.81 units for BCM. Soil treated with 20 t ha–1 BCLL showed a significant increase in tef grain yield, with improvements of 315%, 48%, 48%, and 84% compared to the control, compost, inorganic fertilizer, and sole biochar application, respectively. In conclusion, the application of 20 t ha–1 BCLL has significantly improved soil properties and crop yield. This emphasizes the need to expand the intervention to assist farmers facing similar soil fertility challenges.

Comparative assessment of soil health attributes between topsoil and subsoil influenced by long-term wastewater irrigation

The reuse of wastewater (WW) for crop irrigation is increasingly recognized as an alternative to freshwater irrigation in arid and semi-arid regions. However, there is a significant gap in knowledge regarding the soil health index (SHI) and factors influencing topsoil and subsoil in cropland under long-term WW irrigation. This study aimed to comparatively assess soil health attributes between topsoil and subsoil in smallholder farmlands that have been irrigated with WW for over 50 years. This assessment utilized a combination of soil physico-chemical and fertility attributes, along with heavy metal concentrations. The soil health index (SHI) was developed using linear (SHI - L) and nonlinear (SHI - NL) models, based on the Total Data Set (TDS) and Minimum Data Set (MDS). Statistically significant differences (P ≤ 0.05) were observed between topsoil and subsoil for the soil stability index (SSI), organic matter (SOM), calcium carbonate equivalent (CCE), electrical conductivity (EC), sodium adsorption ratio (SAR), macro- and micronutrients, and heavy metals (Zn, Cu, Cd, Pb, and Ni). In contrast, soil bulk density (BD), pH, and cation exchange capacity (CEC) did not show significant differences. The mean SHI - L and SHI - NL values ranged from 0.68 to 0.77 and 0.46–0.53 for topsoil, and from 0.66 to 0.74 and 0.45–0.51 for subsoil, respectively. The SHI values were higher in the topsoil, with increases ranging from 2.3 % to 7.1 % for SHI - L and 0.65–11.3 % for SHI - NL compared to the subsoil. The regression coefficients between SHIs and corn yield were higher in the topsoil (0.46–0.49) than in the subsoil (0.20–0.22). Furthermore, the SHI - NL model demonstrated greater precision than the SHI - L model in predicting corn yield in both soil depths. These findings highlight the effectiveness of SHI assessments, particularly the SHI - NL model, in analyzing changes in soil health indices with depth and their relationship with crop performance in long-term WW-irrigated smallholder farmlands. This research provides valuable insights into addressing soil health challenges in similar agricultural systems.

Grasslands and flood mitigation – Contrasting forages improve surface water infiltration rates

Grasslands globally deliver many ecosystem services, including water management to alleviate flood risk reduction. Two replicated field experiments were conducted to study how agricultural forage species with diverse rooting systems, sown as single species, affected rooting, soil structure and earthworm populations, and consequently water infiltration to understand how they each might influence flood risk from grasslands. Experiment One showed soils under red clover (Trifolium pratense), white clover (Trifolium repens) and chicory (Cichorium intybus) had higher infiltration rates three years after establishment, compared to perennial ryegrass (Lolium perenne). Higher red clover and chicory root biomass or increased earthworm abundance under white clover may have caused these effects. Experiment Two monitored infiltration at intervals over several years post establishment to understand the timeframe for changes in rates; plantain (Plantago lanceolata) was sown as an additional forage. Infiltration declined post establishment, the timing and extent of decline varying with forages; forage effects were significant after 27 months (P < 0.05). Infiltration rates were higher under red and white clover compared to ryegrass, with chicory and plantain intermediate (P < 0.05). Forages again differed in likely mechanisms delivering higher water infiltration, notably between the two clover species. White clover had higher earthworm biomass (P < 0.05), whereas red clover had a higher average root diameter compared to the other forages (P < 0.05). Drivers of intermediate benefits of chicory and plantain also differed: chicory had higher earthworm abundance (month 38) compared to plantain, which had higher average root diameter compared to ryegrass (month 41); 30 months post-establishment soil bulk density was lower under both forages compared to ryegrass and red clover, with white clover intermediate (P < 0.05); bulk density and penetration resistance did not relate to infiltration. Findings demonstrate that a shift from perennial ryegrass-dominated pastures to swards with more contrasting forages provides an ecohydrological approach to mitigating flood risk and climate adaptation.

Scots pine roots (Pinus sylvestris L.) as dendrogeomorphological indicators of soil erosion on a hiking trail in the Brodnica Lakeland, Poland NE

Trampling on hiking trails leads to vegetation degradation, promoting soil erosion. Erosion removes the topsoil, causing lasting changes and exposing tree roots. Yet, little is known about the environmental factors affecting soil erosion rates determined from tree root analysis. This study, exclusively utilizing microscopic preparations, examines tree root anatomical changes on a lowland trail in Brodnica Lakeland. It aims to understand the temporal and spatial variability of soil erosion rates using dendrogeomorphological records of Scots pine (Pinus sylvestris L.) roots. Up to 64 % of samples show exposure due to continuous denudation, significantly shaping the trail’s relief. Abrupt exposures and secondary growth occur in only 22 % and 14 %, respectively. The average soil erosion rate, calculated from 76 root exposures at the Bachotek site, is 1.93 ± 0.82 mm/year, ranging from 0.71 to 3.80 mm/year, with recently exposed roots exhibiting the highest average soil erosion values on the hiking trail. 45 % of root samples exhibit above-average erosion rates. Statistical analyses reveal that erosion rates (ER) are influenced by soil compaction (COM), bulk density (BULK), root orientation (ASP), and exposure length (EXP). Higher compaction and bulk density correlate with increased erosion, while roots parallel to the trail experience more erosion. Conversely, greater root exposure length leads to decreased erosion rates. These findings suggest that soil erosion on the hiking trail primarily results from gradual geomorphological processes. Wood anatomical analyses of pine roots confirm the role of trampling in initiating and accelerating these processes, altering the trail’s subsurface soil layers, and indirectly affecting soil erosion dynamics. Scots pine roots prove valuable as indicators of the temporal and spatial variability of soil erosion along the lowland trail.

Predicting the soil bulk density using a new spectral PTF based on intact samples

Sample collection and measurement of soil bulk density (BD) are often labor-intensive and expensive in large regions. Conversely, soil spectra are easy to measure and facilitate BD prediction. However, the literature suggests that the damage to the physical structure of soil during scanning spectra on the ground and/or sieved samples might hinder the capacity of spectral technology to accurately predict BD. In addition, because some soil properties that have high correlations with BD, such as the soil organic matter (SOM), are routinely measured and available in most soil databases, coupling them with soil spectra may improve BD prediction compared to using soil properties or spectra. Therefore, in this study, we propose a novel spectral pedo-transfer function (spectral PTF) that couples the measured visible and near-infrared spectra of soils on intact samples and other soil properties to accurately predict the BD (BD = f (soil spectra, soil properties)), which is different from the traditional PTF that uses only soil properties (BD = f (soil properties)) or spectra alone (BD = f (soil spectra)). In this study, we collected topsoil (0–20 cm) and subsoil (20–40 cm) samples from 586 sites in Northeast China, covering a large area of 1.09 million km2 characterized by black soils with high SOM contents. Five routinely measured soil properties were selected: SOM, moisture content (MC), Sand, Silt, and Clay, and various spectral PTFs with one, two, and three soil properties were calibrated using the partial least square regression. The cross-validation results show that the traditional PTF can only predict BD for subsoil with an R2 of 0.51 and an RMSE of 0.11 g·cm−3 when using SOM + MC + Silt or SOM + MC. Compared to subsoil, topsoil and all layers (topsoil + subsoil) had a lower BD prediction accuracy, and a saturation effect was observed for BD values above 1.5 g·cm−3. Unexpectedly, the soil spectra did not provide a higher BD prediction accuracy than traditional PTFs, although the spectra were measured on intact samples. However, adding soil properties to the spectral PTF improved the prediction accuracy and saturation effect for high BD values. The optimal spectral PTF with a single soil property (MC) showed an acceptable BD prediction performance with R2≥0.49, RPD>1.4, and RPIQ>1.7 regardless of whether the sample was topsoil, subsoil, or all layers. Furthermore, the spectral PTF with two or three soil properties yielded a slightly better prediction performance and a more stable prediction among different combinations of soil properties. These results indicate that soil properties and spectra are irreplaceable for BD prediction. Our study demonstrates the potential of spectral PTFs for the accurate prediction of BD and offers insights into the prediction of other soil properties using soil spectra.

Effect of jujube orchard abandonment time on soil properties and enzyme activities at soil profile in the Loess Plateau

In the Loess Plateau, the impact of abandoned farmland on soil properties and enzyme activity, along with its temporal variations and potential driving factors, remains a mystery. This study was designed to systematically and comprehensively examine the variations in soil enzyme activities, particle size distribution, and stability of soil aggregates at different stages of ecological recovery in the Loess Plateau. Our findings reveal a nuanced temporal pattern: with the progression of cropland abandonment, there is a notable decrease in soil bulk density. Concurrently, a dynamic trend in enzyme activities is observed—initially exhibiting a decline, followed by an increase over extended periods of recovery. Notably, prolonged abandonment leads to marked enhancements in soil structure. Parameters such as the mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates show an overall increasing trend. In terms of the Relative Dissipation Index (RSI), our data indicate a sequence of control > 2 years of abandonment > 4 years > 6 years > 14 years. From this, it can be seen that fallowing may be an effective natural restoration strategy for improving the physical structure of soils in the Loess Plateau and restoring soil nutrients. However, positive changes may take a long time to become evident.

Study on the optimal water−biochar management mode based on pan evaporation for solar greenhouse tomato (Solanum lycopersicum L.) in Northeast China

Biochar is commonly employed to enhance soil structure. However, the soil structure degradation due to multi-year continuous cropping poses a significant obstacle to the advancement of solar greenhouse agriculture. This study aimed to optimize the water−biochar management mode for seasonal solar greenhouse tomatoes (Solanum lycopersicum L.), which have been continuously cultivated over three years, with irrigation guided by the evaporation of a 20 cm evaporation pan (Ep-20). The experimental design employed a split–plot arrangement with two factors. The primary factor, irrigation amount, was tested at three levels: 0.6 Ep-20 (W1), 0.8 Ep-20 (W2), and 1.0 Ep-20 (W3). The secondary factor, biochar amount, was tested at three levels: 0 (B0), 20 t ha−1 (B1), and 40 t ha−1 (B2). The results revealed that biochar reduced soil bulk density and enhanced field capacity, tomato plant height, and photosynthesis. Increased irrigation improved tomato appearance quality but reduced nutritional quality, whereas higher biochar application improved both aspects. Principal component analysis (PCA) and grey relational analysis (GRA) results identified W2B2 as the optimal mode for the quality of spring tomato and autumn tomato. Compared to the control (W3B0), W2B2 exhibited an average increase of 18.0 % in yield and 47.5 % in irrigation water productivity (WPI) with a 20 % reduction in irrigation amount across two seasons. The technique for order preference by similarity to ideal solution (TOPSIS) comprehensive evaluation determined that the W2B2 mode maximized comprehensive benefits, enhancing both the overall quality of tomato and achieving higher yield and WPI. This study utilized the Ep-20 to characterize the reference crop evapotranspiration (ETo) and the crop evapotranspiration (ETc). The investigation demonstrated the feasibility of utilizing Ep-20 to guide irrigation under biochar application conditions and develop ETc estimation models for water−biochar management modes to optimize solar greenhouse tomato production.

Impacts of bulk density and water content on the tire-soil contact area of agricultural field vehicles

We tested the hypothesis that the increase in soil stiffness, induced by variations in bulk density and water content at the tire-soil contact interface, causes a reduction in the contact area. For this, we examined the contact area from different tire-ground contact scenarios and compared the measurements and simulations using a contact area description model. Front and rear tractor tires were used for the measurement of the contact area under tilled soil, sugarcane field, unpaved road, and paved ground scenarios, which induced different bulk densities and water content levels. The results revealed that soil stiffness reduced the tire-soil contact area. The tire-soil contact area increased as the water content increased and the bulk density was reduced. For the front tractor tire, the theoretical contact area was similar to the values found for tilled soil, but there was a large difference between the measurements (2,200 cm2, for the tilled soil) and the theoretical estimates (3,100 cm2) for the rear tractor tire (likely induced by tire dimensions). Our results suggest that increases in soil stiffness reduce the tire-soil contact area. The higher the soil bulk density and the lower the soil moisture, the lower the contact area. The results also revealed that the tire tractor tread might reduce the contact at the hard surface, making the shape of the contact area more geometrically irregular and different from those predicted by models using regular geometry (e.g., cycles, ellipses, or rectangles). This study suggests that two-body (soil and tire) contact models for deformable surfaces should be used in future tire-soil contact models of agricultural field vehicles.

Intervention of Smallholder Homegarden Agroforestry Enhanced Soil Fertility Status and Soil Organic Carbon Stock in Tigray Lowlands, Northern Ethiopia

Justification: To reverse the challenges of land degradation, improve soil fertility and access to feed and wood, communities in the lowlands of northern Ethiopia started to establish homegarden agroforestry (HAF) decades ago. However, limited information is available and there was information gap on the effects of homegarden agroforestry systems (HAF) on soil properties and soil organic carbon stock enhancement in the Tigray lowlands, Northern Ethiopia. Aim: The objective of this was to explore the effect of conversion of mono-cropping systems (MCS) to HAF in Tselemti district, Tigray lowland, Northern Ethiopia. Materials, Methods and Statistical Methods Used: Two land use types, HAF and MCS fields replicated 15 times were considered. Thus, 30 fields, 15 from HAF &amp; 15 from MCS were used. From each field, 1 composite soil sample for analysis of soil nutrients and 1 undisturbed soil sample for soil bulk density (BD) determination were collected from a depth of 0-30cm. All values were subjected to SPSS version 20 and analyzed using paired samples t-Test statistics at 5% level of significance. Results: The intervention of HAF resulted in significantly higher (p&lt;0.05) and enhance SOC by 76% (1.66 +0.06 and 0.94 + 0.05 %); SOC stock by 82% (73+ 3 and 40+2); N by 75% (0.14 +0.02 and 0.08 + 0.01 %);avP by 37% (6.07 +0.58 and 4.42 + 0.21 ppm) and K by 26% (67.05+ 4.5 and 53.39+ 4.3 mg kg-1) (p&lt;0.05) as compared to the MCS. Conclusion: This study elucidated that home gardening can help for maintaining soil nutrients and soil organic carbon stock. Hence, additional HAF have to be established in the area and in areas with similar bio-physical and socio-economic set up and the government should establish programs and campaigns to disseminate HAF systems and promote the importance of the land use.

Effects of Biochar-Amended Composts on Selected Enzyme Activities in Soils

This study examines the effect of biochar as an agricultural soil supplement on soil quality indicators, specifically enzyme activity in Missouri regions. While the benefits of biochar on soil bulk density, soil organic carbon, and infiltration have been established, its effect on soil enzyme activity has remained underexplored in this region. A three-year field investigation was conducted with six treatments (compost, biochar, compost + biochar, biochar + compost tea, fescue, and control) to evaluate the effects on enzymes such as β-glucosidase (BG), acid and alkaline phosphatases (ACP-ALP), arylsulfatase (ARS), dehydrogenases (DG), arylamidase (AMD), cellulase (CLS), and urease (URS). Furthermore, soil pH, organic matter (OM), and cation exchange capacity (CEC) were determined. The results showed that compost and biochar treatments considerably increased soil enzyme activity compared to other treatments, with nitrogen application further increasing enzyme activity. Soil pH, OM, and CEC were all important determinants in determining enzyme activity, with BG demonstrating strong positive associations with ACP and AMD (99.5%). This study shows that compost and biochar amendments significantly improve soil physicochemical and biological properties, thereby enhancing soil health and assisting farmers’ sustainable soil management practices.

Enhancing Soil Resilience and Sugar Beet (Beta vulgaris L.) Yield: Mid‐Term Effects of Compost and Glauconite Integration

ABSTRACTSugar beet (Beta vulgaris L.) is a globally significant crop, valued for its economic importance in sugar production. Saline‐sodic soil environments negatively impact sugar beet productivity. This study investigates the effects of using compost, glauconite enriched‐K and their combinations in mitigating the saline‐sodic soil environment, sugar beet productivity and extracted sugar quality. A two‐season field experiment in split‐plot design with the main plots is three doses of compost: control (C0), recommended (100%) dose (C1) and 150% recommended dose (C2). Each group divided into four subplots of glauconite treatments arranged according to the recommended dose of potassium (K) as follows: G0 (no glauconite), G1 (50% K), G2 (100% K, 480 Kg glauconite Fed−1) and G3 (150% K). The results showed that compost and glauconite mitigated adverse soil effects caused by salinity and sodicity. The C2G3 treatment reduced electrical conductivity (EC) and exchangeable sodium percentage (ESP), improved organic matter and enhanced soil bulk density, porosity and penetration resistance. This combination also increased soil nutrients (N, K, Fe, Mn, Zn and Cu). Regarding the sugar beet yield, C2G3 improved root yield, top yield, sugar yield and extracted sugar. The application of glauconite increased root diameter by 20% and root length by 23%, enhanced sugar quality with minimal sugar losses to molasses (2.43%), and reduced impurities of K, α‐amino N and Na. Principal component analysis showed positive correlations between root yield and soil potassium, organic matter, cation exchange capacity and soil porosity, with negative correlations to bulk density, EC, pH and ESP. Two‐way analysis of main (ANOM) illustrated significant effects of compost and glauconite on soil–plant interactions. Multivariate analysis indicated that higher glauconite doses significantly enhanced root yield. The Gag run charts confirmed that compost (100%) and G3 levels explored more homogeneity reducing the ESP%, increasing sugar beet root yield, sugar yield and quality.