Soil Bulk Density Research Articles

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 & 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<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<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.

Effects of autumn tillage with straw return on soil physical characteristics of corn fields in the eastern loess plateau

The implementation of unsuitable tillage practices has the potential to disrupt the structure integrity of the ploughed layer, as well as to influence the physical parameters of the soil. The application of a reasonable tillage method has been demonstrated to result in an improvement in the physical quality of the soil. Three autumn tillage practices have been implemented at the Dongyang Experimental Station of Shanxi Agricultural University since 2016: no-tillage with straw mulch (NTS), autumn rotary tillage with straw incorporation (RTS), and autumn plough tillage with straw incorporation (PTS). The impact of autumn tillage practices on soil physical quality in the 0–30 cm profile of spring corn fields was evaluated following the corn harvest in 2018 and 2019. The results showed that compared to the NTS treatment, the application of RTS was found to have decreased significantly by 9.6%–24.2% in soil bulk density, while it increased significantly by 12.8%–34.0% in total porosity and by 43.5%–146.4% in macroporosity at a depth of 5–10 cm. In comparison to the NTS treatment, the adoption of PTS was found to decrease significantly by 10.7%–30.5% soil bulk density, while it increased significantly by 9.9%–42.7% the total porosity and 23.1%–202.8% the macroporosity at a depth of 0–10 cm. Furthermore, the soil microporosity significantly increase of 7.5%–11.1% under the RTS treatment at the 0–5 cm soil depth and 7.7%–11.2% under the PTS treatment at the 10–20 cm soil depth. Soil physical quality index (SQI) significantly increase under the RTS and PTS treatments, with a 41.26% and 57.57% improvement, respectively, in comparison to the NTS treatment. In summary, the adoption of autumn tillage with straw return (RTS and PTS) demonstrated a reduction in soil bulk density, an increase in soil porosity, macroporosity, and a promotion of capillary porosity, and promoted the improvement of soil physical quality on the Eastern Loess Plateau when compared to no-tillage with straw mulch (NTS).

Mechanical Resistance to Penetration for Improved Diagnosis of Soil Compaction at Grazing and Forest Sites

Penetrometers and penetrographers are widely used to measure soil resistance to penetration, but the results are associated with other soil properties (such as bulk density, water content, and particle size distribution). Thus, for an adequate interpretation of results, site-specific studies are necessary to identify which properties are more related to soil resistance. We aimed to measure the resistance to penetration of a Typic Paleudalf under distinct soil uses and to identify soil properties that influence soil resistance. The soil uses in this study included anthropized forest (composed of tree and shrub species), pasture (5-year-old pasture), Eucalyptus 20 (a 20-year-old Eucalyptus saligna stand), and Eucalyptus 4.5 (a 4.5-year-old Eucalyptus saligna under the second rotation). Soil resistance to penetration was measured with an impact penetrometer, and the data were correlated with other physical and mechanical properties of soil, such as the particle size, soil moisture, air permeability, saturated hydraulic conductivity, porosity, bulk density, precompression stress, and compressibility index. We observed that a resistance of 1.3 MPa matches with other soil property values corresponding to soil compaction, and values greater than 1.3 MPa were verified at depths of 0–8 cm for pasture and 8–30 cm for Eucalyptus 4.5. Analyzing all soil uses together, the correlation was significant (p < 0.05) with gravel (r = 0.34), silt (r = −0.32), clay (r = 0.26), gravimetric moisture (r = −0.27), macroporosity (r = 0.24), and soil bulk density at the end of the compressibility test (r = 0.27). The penetrometer is useful for evaluating the physical conditions of soil, but we highlight that soil resistance is influenced by factors such as particle size and soil moisture, as examples. We recommend using a set of soil properties for a better interpretation of penetration resistance data and to support decision-making regarding soil management.

Sustainability of athletic field turf comparing organic and synthetic practices under two heights of cut

AbstractLong‐term comparisons over several years between organic and synthetic management are lacking in sports turf research. Our objective was to investigate playing surface qualities and soil properties over an 8‐year period. For this trial, Kentucky bluegrass (KBG, Poa pratensis L.) sod was established and annually inter‐seeded with perennial ryegrass (Lolium perenne L.) and KBG. Factors included height of cut (3.2 and 6.4 cm) and management systems (MSs; synthetic and organic) with three replicates. Synthetic practices included chemical fertilizers and pesticides, while the organic system used hand‐weeding and biological fertilizers (leaf compost and naturally derived organics) with biological controls. In all years, wear was simulated in the fall using a slip‐wear machine and evaluated for playing qualities including visual wear tolerance, ball bounce (BB), surface hardness, and traction. Soil properties were evaluated in some years including pH, soil organic matter (SOM), soil bulk density, soil aggregate stability (SAG), and soil available P. Both MS received the same total N of 196 kg ha−1 year−1 but P applied varied with the MS (synthetic, 7.6 kg ha−1 year−1; organic, 23.2 kg ha−1 year−1). Synthetic practices provided acceptable visual wear tolerance (1–9, ≥6 acceptable) in 4 of 8 years compared to only 1 year for organic practices. Shorter cut grass (3.2 cm) consistently provided better visual wear tolerance (average = 5.6), harder surfaces (average = 51 g), and higher BB (average = 35.8%) consistent with accepted player standards. Synthetic practices afforded better tolerance to wear compared to organic practices in 5 of 8 years but little difference was observed in the other surface properties. Organic practices were consistently above 6.0 in soil pH (higher by 12%), 20% higher in soil available P, 25% higher in SOM, and with lower soil bulk density. SAG was higher following 8 years of simulated traffic by the last year of the test under organic practices. Results suggest competing benefits with synthetic practices affording better wear tolerance while organic practices promote better soil health.

Mitigating the detrimental impacts of low- and high-density polyethylene microplastics using a novel microbial consortium on a soil-plant system: Insights and interactions

The accumulation of polyethylene microplastics (PE-MPs) in soil has raised considerable concerns; however, the effects of their persistence and mitigation on agroecosystems have not been explored. This study aimed to assess the detrimental effects of PE-MPs on a soil-plant system and evaluate their mitigation using a novel microbial consortium (MC). We incorporated low-density polyethylene (LDPE) and high-density polyethylene (HDPE) at two different concentrations, along with a control (0 %, 1 %, and 2 % w/w) into the sandy loam soil for a duration of 135 days. The samples were also treated with a novel MC and incubated for 135 days. The MC comprised three bacterial strains (Ralstonia pickettii (MW290933) strain SHAn2, Pseudomonas putida strain ShA, and Lysinibacillus xylanilyticus XDB9 (T) strain S7–10F), and a fungal strain (Aspergillus niger strain F1–16S). Sunflowers were subsequently cultivated, and physiological growth parameters were measured. The results showed that adding 2 % LDPE significantly decreased soil pH by 1.06 units compared to the control. Moreover, adding 2 % HDPE resulted in a more significant decrease in soil electrical conductivity (EC) relative to LDPE and the control. A dose-dependent increase in dissolved organic carbon (DOC) was observed, with the highest DOC found in 2 % LDPE. The addition of higher dosages of LDPE reduced soil bulk density (BD) more than HDPE. The addition of 2 % HDPE increased the water drop penetration time (WDPT) but decreased the mean weight diameter of soil aggregates (MWD) and water-stable aggregates (WSA) compared to LDPE. The results also revealed that higher levels of LDPE enhanced soil basal respiration (BR) and microbial carbon biomass (MBC). The interaction of MC and higher MP percentages considerably reduced soil pH, EC, BD, and WDPT but significantly increased soil DOC, MWD, WSA, BR, and MBC. Regarding plant growth, incorporating 2 % PE-MPs significantly reduced physiological responses of sunflower: chlorophyll content (Chl; −15.2 %), Fv/Fm ratio (-25.3 %), shoot dry weight (ShD; −31.3 %), root dry weight (RD; −40 %), leaf area (LA; −38.4 %), and stem diameter (StemD; −25 %) compared to the control; however, the addition of novel MC considerably reduced and ameliorated the harmful effects of 2 % PE-MPs on the investigated plant growth responses.

Soils after forestry management activities in spruce plantations

The carbon accumulation in forest ecosystems helps to mitigate climate changes, therefore the interest in finding strategies for adapted forest management is a major goal of our time. The artificial plantations of Norway spruce (Picea abies Karst) are part of the Bulgarian project to restore the regulatory functions of forest ecosystems. Due to their low resistance, intensive processes of deposition and degradation take place in them, which emphasizes the need to understand the condition of soils and the amount of accumulated carbon in them. This paper reports results from a study on the thinning in even-aged Norway spruce plantations (Picea abies Karst) and its effect on some soil properties. The study includes two thinned plots and an untinned control: 1) Control – an unmanaged spruce plantation, without any activities in it through the last 20 years; 2) Thinned – managed with regular felling over the years, the last of which was carried out 10 years ago with 25% intensity; and 3) Ice storm – plantation damaged from an ice storm in 2007 (when it was 33 years old), felling followed by removal of all affected trees – over 95%, and afforestation with spruce saplings. The soil was examined by layers from 10 cm to 30 cm depth. The main soil characteristics connected with the carbon stocks in soil are analyzed - bulk density, skel-eton, and carbon content. The results of the experiment show that the performed forestry activities were conducted with abidance of the requirements for habitat protection and the ecosystem’s functionality in the studied sites. No significant changes in coarse fraction content and bulk density of soils were found. There is no statistical difference between the plots in the studied depths, but there is a trend of decrease in the organic carbon content in the managed sites. The differences in the soil carbon stocks are significant for the first two soil layers between the control and the managed trough thinning plot. 

Effect of Land Use Type on Soil Moisture Dynamics in the Sloping Lands of the Black Soil (Mollisols) Region of Northeast China

This study investigates the spatial and temporal heterogeneity of soil moisture on slopes of China’s northeastern black soil region, focusing on the effects of terrain adjustment and vegetation. Soil moisture dynamics in the 0–60 cm soil layer were measured at 10 cm intervals using the TRIME-PICO64 TDR® device on slopes with similar gradients representing three land use types: transverse ridge tillage (TRT) farmland, terraced fields (TFs) farmland, and pure forest woodland (WL). The results indicate significant variations in soil moisture content and water storage across different land use types in the order of TF > TRT > WL. The study further identified that soil bulk density, porosity, and water-holding indicators were in the order of WL > TF > TRT, inconsistent with the soil moisture results, indicating that soil quality cannot be the sole reason for the differences in moisture. The moisture differences between farmland types (TRT and TF) and WL are substantial, especially during the rainy season. In the rainy season (0–60 cm) and the dry season (30–60 cm), significant differences in moisture content are observed (p < 0.05). Significant differences in moisture content between farmland types are found at 0–40 cm during the rainy season and at 0–10 cm during the dry season. In the rainy season, soil moisture for TRT and TFs first decreases from 26.76% and 30.85% to 22.44% and 25.38%, then slightly increases to 27.01% and 27.07% along the slope. Meanwhile, WL displays the opposite pattern on upper, relatively steep slopes, with soil moisture increasing from 16.66% to 17.81%, and exhibits a pattern of change similar to TRT and TFs on lower, gentler slopes. TFs consistently show higher soil moisture and water storage at all slope positions than TRT and WL. TFs improve soil quality, reduce erosion and sedimentation, and shift the lowest soil moisture content to a lower slope position. During the dry season, soil moisture differences between slope positions for TRT and WL were small. In general, terracing can effectively modulate moisture distribution along slopes, increasing moisture by an average of 0.26~12.43%, while afforestation, despite improving soil quality, leads to an 18.14~31.13% reduction in soil moisture content, with the impact being particularly significant during the rainy season. These findings provide important insights for optimizing land use and ecological construction, including keeping the balance between soil and water conservation, especially for sub-humid slope terrain areas.

ESTIMATING THE TOTAL CARBON STOCK IN THE MANGROVE FOREST OF KOTA MARUDU, SABAH, MALAYSIA

Mangrove forests are capable of storing vast amounts of carbon and are recognised as one of the highest carbon densities in the world. This research examines the mangrove forest in Kota Marudu, Sabah, Malaysia, specifically its soil’s physico-chemical properties and total carbon stock. Using two 100-metre-long transect lines with seven-metre diameter circle subplots established at every 25 metres, a forest inventory and an allometric equation were used to determine the aboveground and belowground biomass. The carbon content was estimated to be 50% of biomass. Simultaneously, soil samples were collected at depths of 0-15 cm, 15-30 cm, 30-50 cm, and 50-100 cm for soil analysis and bulk density. A CHNS elemental analyser was used to determine the carbon content in the soil. The results showed that the Kota Marudu mangrove forest has a total carbon stock of 1,010.65 Mg C ha-1, where around 80% of it was contributed by the soil carbon pool at 876.16 Mg C ha-1. The results also revealed that the living tree and roots carbon pool were measured at 100.87 Mg C ha-1 and 33.62 Mg C ha-1, respectively. These findings highlight the crucial role of mangrove forests in carbon sequestering and mitigating climate change.

Multifactor analysis of the infiltration characteristics of film hole irrigation under muddy water conditions

Film hole irrigation under muddy water conditions is a new and effective water-saving irrigation technology. In order to determine the influence of multiple factors on the infiltration process of film hole irrigation under muddy water conditions, 12 sets of indoor infiltration tests were conducted to investigate the effects of four key influencing factors (muddy water sand content, hole diameter, soil bulk density, and infiltration time) on the infiltration characteristics of irrigation with film holes under muddy water conditions, in this study. Based on the experimental data, accurate and effective soil water infiltration and vertical and horizontal wetting front transport models were constructed. Based on the modeling results, the standard regression coefficients of each influencing factor against the fitted parameters were calculated and the effects of the factors on the fitted parameters were analyzed. Error analysis showed that both models could effectively simulate the soil water infiltration process under experimental conditions. Infiltration time was the dominant factor influencing the cumulative infiltration per unit of film hole area, followed by hole diameter, muddy water sand content and lastly, soil bulk density. Infiltration time was also the main influencing factor of the vertical wetting front transport distance, followed by soil bulk density, muddy water sand content, and lastly, hole diameter. Similarly, infiltration time exerted the greatest effect on the horizontal transport distance, followed by hole diameter, soil bulk density and muddy water sand content. The model validation revealed that both the calculated and measured values were distributed around the 1:1 line, reflecting the accuracy of the models. The results of this study can provide theoretical support for the design of film hole irrigation systems under muddy water conditions.

A method for estimating the bulk density and particle density of granite residual soil based on the construction of pedotransfer functions

AbstractParticle density (ρs) and bulk density (ρb) are key factors in the calculation of total soil porosity. However, direct measurements of ρs and ρb are labour‐intensive, time‐consuming, and sometimes impractical. Pedotransfer functions (PTFs) provide alternative methods for indirect estimation of ρs and ρb. In this paper, the accuracy of typical 12 ρs and 9 ρb PTFs was evaluated using easily measurable soil properties (sand, silt, clay, and soil organic matter (SOM) content) from granitic residual soils collected from six study areas in subtropical China, and the accuracy of PTFs constructed based on multiple linear stepwise regression (MSR) and machine‐learned algorithms (backpropagation neural network, k‐nearest neighbour algorithms, random forests, support vector machines, and gradient boosted decision trees) was compared to determine the accuracy of PTFs. The results show that typical PTFs have poor accuracy (R2adjusted < 0.020) and are not applicable to the indirect estimation of ρs and ρb in granitic residual soils. The PTFs constructed by machine learning algorithms all performed better than MSR, with the highest estimation accuracy of the PTFs constructed by the random forest algorithm, with R2adjusted values of 0.923 and 0.933 for the ρs and ρb PTFs, respectively, and root‐mean‐square error of 0.020 g·cm−3 and 0.023 g·cm−3, respectively. Compared with MSR, the random forest algorithm has greater accuracy and eliminates the restriction of PTFs on predictors, which provides support for understanding the changing rules of ρs and ρb in granite residual soils in subtropical regions, evaluating soil quality and improving soil structure.

A sigmoidal model for predicting soil thermal conductivity-water content function in room temperature

Apparent thermal conductivity of soil (λ) as a function of soil water content (θ), i.e., λ(θ) is needed to determine the heat flow in soil. The function of λ(θ) can be used in heat and water flow models for simplicity. The objective of this study was to develop a sigmoidal model based on logistic equation for entire range of soil water contents and a wide range of soil textures that can be used in simulation of heat and water flow in respected modes. Further, performance of the developed sigmoidal model along with two other models in literature was evaluated. In the proposed sigmoidal model, the constants of this model are estimated based on empirical multivariate equations by using soil sand content and bulk density. The sigmoidal model was validated with good accuracy for a wide range of soil textures, as the relationship between the measured and predicted λ showed slope and intercept values of nearly 1.0 and 0.0, respectively. Comparison of the results obtained by sigmoidal model with those obtained from Johansen and Lu et al. models indicated that, the sigmoidal model was superior to the other two models in prediction of λ for a wide range of soil textures and soil water contents. Furthermore, comparison with a recently proposed model by Xiong et al. indicated that our sigmoidal model is superior. Therefore, our developed sigmoidal model can be used in heat and water flow models to predict the soil temperature and heat flow.

Penilaian Tingkat Kekeritisan Lahan Pertambangan dan Beberapa Pengguanaan Lahan Lainnya di Kalimantan Selatan

Critical land is land that is no longer productive from an agricultural perspective, because management and use do not consider land management requirements and soil conservation principles. This research aims to assess the level of criticality of land based on the level of erosion that occurs at various coal mining land locations in several districts in South Kalimantan. This research is non-experimental research using exploratory descriptive methods. The data collected is secondary data obtained through official publications from the Environmental Service and related agencies from several environmental documents of coal mining companies that have received approval from the authorized Agency. The secondary data used is the data needed to calculate the amount of erosion which is used as a basis for evaluating land criticality. These data include: soil texture, permeability, bulk density, rainfall, slope and slope length, management factors, land cover vegetation factors and soil organic C. Erosion estimation uses the Universal Soil Loss Equation (USLE) method. The results of erosion calculations using USLE show that in open mine land in Banjar Regency it is 233.9 tons ha-1 year-1, while in Tanah Laut Regency is 173.1 tons ha-1 year-1 and in Kotabaru Regency is 275.1 tons ha-1 year-1. The level of criticality of land in the mining area is at a critical and very critical level compared to natural land and cultivated land due to differences in erosion values ​​and also the thickness of the soil solum studied.

No-tillage with straw retention influenced maize root growth morphology by changing soil physical properties and aggregate structure in Northeast China: A ten-year field experiment

Conservation tillage, particularly the implementation of no-tillage and straw retention (NTS), has been proposed as an effective practice to enhance soil structure and improve soil quality in Northeast China. However, the impact of NTS on maize (Zea mays L.) root growth morphology and the influence of tillage practices on maize root morphology through soil physical properties and structure in Northeast China remain understudied. To address this knowledge gap, a continuous ten-year experiment was conducted to assess the effects of NTS on soil physical properties, aggregate structure, maize root morphology, and their interconnections. Our findings demonstrate that the NTS treatment significantly increased soil water content and soil bulk density at depths of 0–5 cm (1.6%) and 5–10 cm (2.2%), while decreasing soil porosity at depths of 0–5 cm (1.4%) and 5–10 cm (2.0%) compared to conventional tillage (CT). Additionally, NTS resulted in a higher content of soil macro-aggregates (> 0.25 mm) and improved soil aggregate stability compared to CT. Notably, root length, root surface area, root volume, and root biomass in the NTS treatment were 6.04%, 22.15%, 10.04%, and 9.29% higher than those in CT, respectively. However, there was no significant difference in root diameter between the two tillage practices. These results reveal that NTS induces alterations in soil physical properties, aggregate size distribution and aggregate stability, thereby affecting maize root growth morphology.