Key Soil Properties Research Articles

Characterization of the salt marsh soils and visible-near-infrared spectroscopy along a chronosequence of Spartina alterniflora invasion in a coastal wetland of eastern China

Introduction of exotic Spartina alterniflora (S. alterniflora) is important to re-establish the structure and function of salt marsh ecosystems along the coast of China. Characterization the spatial-temporal patterns of S. alterniflora soils is thus essential for the assessment of the pace of ecosystem development. However, the determination of soil properties by traditional analysis almost impossible achieve a timely detection of soil changes that is generally required by soil monitoring tasks for demonstrating impacts of S. alterniflora invasion. This work focused on the use of visible-near-infrared spectroscopy (VNIRS) for characterizing soils and predicting key physical and chemical soil properties in S. alterniflora areas. A set of soil profiles representing a chronosequence of S. alterniflora invasion was used, comprising 45 samples from 15 sites. The results showed that approximately 20-year of S. alterniflora invasion has altered soil characteristics especially in the topsoil. Changes of soil associated with sampling horizons and ages of S. alterniflora could be distinguishable using soil variables and VNIRS, and high correlations were found between soils and spectra information. The results of predictions showed that predictive accuracy for salinity, pH, clay, the ratio of carbon to nitrogen, organic carbon and calcium carbonate were acceptable, but models for total nitrogen, bulk density, sand and silt were less satisfactory. These results suggested the possibility of VNIRS for the rapid assessment of key physical and chemical soil properties in S. alterniflora areas. This work highlights that VNIRS technique could be taken as a useful tool to investigate soil changes and explore understanding of soil development in S. alterniflora marshes.

Variation of soil microbial and earthworm communities along an agricultural transect with tree windbreak

Windbreaks are among the most widespread agroforestry systems in the temperate biome. Tree windbreaks are expected to have unique soil properties and biotic communities, compared to adjacent agricultural fields. We compared key soil properties and communities of earthworms, bacteria and fungi along an agricultural transect through a tree windbreak into a cropped field. Soil properties, earthworm abundance and diversity, and bacterial and fungal alpha-diversity (16S-rRNA and ITS gene sequencing) were assessed along transects at distances of 0 (directly under the tree canopy), 8 (ecotone in the cropped field) and 50 m from the tree row in six mature (20- to 70-years-old) tree windbreaks located in southeastern Quebec, Canada. Soil organic C, total N and C:N ratio were higher, while soil pH was lower in the tree row than in the adjacent cropped fields at distances of 8 m and 50 m from the windbreak. Each group of biota had a distinct pattern along the agricultural transect. Earthworm abundance and biomass were greater at 50 m than 8 m from the windbreak. Epigeic, endogeic, and anecic earthworms varied similarly along the agricultural transect. Fungal diversity was higher at 8 m than at 0 m from the windbreak. Bacterial diversity was higher at 50 m than at 0 m from the windbreak. Tree windbreaks made the soil environment in the ecotone more favorable for fungal communities, but less favorable for earthworm communities. Greater bacterial diversity was associated with agricultural activities than windbreaks.

Evaluating the effects of soil erosion and productivity decline on soil carbon dynamics using a model-based approach

Abstract. Sustained accelerated soil erosion alters key soil properties such as nutrient availability, water holding capacity, soil depth and texture, which in turn have detrimental effects on crop productivity and therefore reduce C input to soils. In this study, we applied a 1-D soil profile model that links soil organic carbon (SOC) turnover, soil erosion and biomass production. We used observational data to constrain the relationship between soil erosion and crop productivity. Assuming no change in effort, we evaluated the model performance in terms of SOC stock evolution using published observational data from 10 catchments across Europe and the USA. Model simulations showed that accounting for erosion-induced productivity decline (i) increased SOC losses by 37 % on average compared to a scenario where these effects were excluded, and (ii) improved the prediction of SOC losses when substantial soil truncation takes place. Furthermore, erosion-induced productivity decline reduced soil–atmosphere C exchanges by up to 30 % after 200 years of transient simulation. The results are thus relevant for longer-term assessments and they stress the need for integrated soil–plant models that operate at the landscape scale to better constrain the overall SOC budget.

Mapping at 30 m Resolution of Soil Attributes at Multiple Depths in Midwest Brazil

The Midwest region in Brazil has the largest and most recent agricultural frontier in the country where there is no currently detailed soil information to support the agricultural intensification. Producing large-extent digital soil maps demands a huge volume of data and high computing capacity. This paper proposed mapping surface and subsurface key soil attributes with 30 m-resolution in a large area of Midwest Brazil. These soil maps at multiple depth increments will provide adequate information to guide land use throughout the region. The study area comprises about 851,000 km2 in the Cerrado biome (savannah) in the Brazilian Midwest. We used soil data from 7908 sites of the Brazilian Soil Spectral Library and 231 of the Free Brazilian Repository for Open Soil Data. We selected nine key soil attributes for mapping and aggregated them into three depth intervals: 0–20, 20–60 and 60–100 cm. A total of 33 soil predictors were prepared using Google Earth Engine (GEE), such as climate and geologic features with 1 km-resolution, terrain and two new covariates with 30 m-resolution, based on satellite measurements of the topsoil reflectance and the seasonal variability in vegetation spectra. The scorpan model was adopted for mapping of soil variables using random forest regression (RF). We used the model-based optimization by tuning RF hyperparameters and calculated the scaled permutation importance of covariates in R software. Our results were promising, with a satisfactory model performance for physical and chemical attributes at all depth intervals. Elevation, climate and topsoil reflectance were the most important covariates in predicting sand, clay and silt. In general, for predicting soil chemical attributes, climatic variables, elevation and vegetation reflectance provided to be the most important of predictive components, while for organic matter it was a combination of climatic dynamics and reflectance bands from vegetation and topsoil. The multiple depth maps showed that soil attributes largely varied across the study area, from clayey to sandy, suggesting that less than 44% of the studied soils had good natural fertility. We concluded that key soil attributes from multiple depth increments can be mapped using Earth observations data and machine learning methods with good performance.

Digital soil mapping of key GlobalSoilMap properties in Northern Karnataka Plateau

Accurate and quantitative information on soil properties of each and every location is essential for site specific sustainable management of land resources. A study was conducted to predict the different key soil properties of Northern Karnataka as per GlobalSoilMap specifications using Quantile Regression Forest (QRF) Model. Along with Sentinel-2 data, terrain attributes such as elevation, slope, aspect, topographic wetness index, topographic position index, plan and profile curvature, multi-resolution index of valley bottom flatness, multi-resolution ridge top flatness and vegetation factors like NDVI and EVI were used as covariates. Equal-area quadratic splines were fitted to soil profile datasets to estimate soil properties viz. pH, OC, CEC, clay, sand, silt, field capacity and permanent wilting point at six standard soil depths (0–5, 5–15, 15–30, 30–60, 60–100 and 100–200 cm) as per GlobalSoilMap specifications. The coefficient of determination (R2), mean error (ME) and root mean square error (RMSE) were calculated in order to assess model performance. Prediction interval coverage percentage (PICP) was calculated to evaluate the associated uncertainty predictions. The predicted soil properties are reliable with minimum errors and the QRF model captured maximum variability for most of the soil properties.

Plant invasion alters the physico-chemical dynamics of soil system: insights from invasive Leucanthemum vulgare in the Indian Himalaya.

Understanding the impact of plant invasions on the terrestrial ecosystems, particularly below-ground soil system dynamics can be vital for successful management and restoration of invaded landscapes. Here, we report the impacts of a global plant invader, Leucanthemum vulgare Lam. (ox-eye daisy), on the key physico-chemical soil properties across four sites selected along an altitudinal gradient (1600-2550 m) in Kashmir Himalaya, India. At each site, two types of spatially separated but environmentally similar sampling plots: invaded (IN) and uninvaded (UN) were selected for soil sampling. The results revealed that invasion by L. vulgare had a significant impact on key soil properties in the IN plots. The soil pH, water content, organic carbon and total nitrogen were significantly higher in the IN plots as compared with the UN plots. In contrast, the electrical conductivity, phosphorous and micronutrients, viz. iron, copper, manganese and zinc, were significantly lower in the IN plots as compared with the UN plots. These changes in the soil system dynamics associated with L. vulgare invasion were consistent across all the sites. Also, among the sites, soil properties of low-altitude site (1600 m) were different from the rest of the sampling sites. Overall, the results of the present study indicate that L. vulgare, by altering key properties of the soil system, is likely to influence nutrient cycling processes and facilitates positive feedback for itself. Furthermore, the research insights from this study have wide management implications in the effective ecological restoration of the invaded landscapes.

Interrelationships among ecological factors of brachyuran crabs, trees and soil in mangrove community assemblage in Northeast Brazil

Mangroves are dynamic ecosystems due to influence of abiotic and biotic factors, but the latter are far less studied. Interactions between key invertebrate groups, trees, and soil properties, among others, determine the community structure throughout mangrove stand developing. Covariation among these factors, however, obscures their mutual relationships in shaping mangrove community assemblage patterns. In the estuary of Pacoti River (Ceara State, northeast Brazil), we compared the diversity and distribution of brachyurans and trees among several mid-littoral areas, and their relation with sediment features, to understand their relationships in community assemblage of new mangrove stands in developing. To discriminate the relation among these variables, ordination of data (PCA) and multivariate multiple correlation (PLS) were used. Data show that intertidal establishment of Brachyura was determined primarily by sediment properties, but further spatial distribution and diversity of this key faunal group, and the tree species that establishes, can influence each other. The prop roots habitat of Rhizophora mangle supports a higher brachyuran richness, since it allows the existence of multispecific crab burrow systems underground. Our results show that Rhizophora and brachyurans are key engineer organisms involved in shaping the physical and, hence, the ecological structure of newly established mangrove stands at Neotropics.

Interactive effects of multiple heavy metal(loid)s on their bioavailability in cocontaminated paddy soils in a large region

Heavy metal(loid) pollution in large regions is often highly complex due to the coexistence and interactions of metal(loid)s and complex soil environments. However, the interaction effects of heavy metal(loid)s on their bioavailability in large regions remain obscure. Here, we identified the interaction effects of Pb, Cd and As on their bioavailability in cocontaminated paddy soils of Shaoguan City, China. The results showed that pH (12.40%) was the most important impact factor among the key soil properties of the pH, CEC, and SOM for the bioconcentration factor (BCF) of Cd. As the soil Pb content decreased and the soil Cd content increased, the interaction of soil Pb and Cd increased the BCF of Pb. As the soil Pb content increased and the soil Cd content decreased, the interaction of soil Pb and Cd increased the BCF of Cd. The synergistic interaction of Pb and Cd in soil promoted the accumulation of both Pb and Cd in rice under certain soil conditions. Specifically, when the average pH and CEC were below 6.19 ± 0.82 and above 7.23 ± 2.55 cmol (+)/kg, respectively, the average BCF of Cd varied from 0.70 ± 0.80 to 1.47 ± 0.62 due to the interactive effect of soil Cd and Pb on the BCF of Cd. When the average pH was above 6.19 ± 0.82 and the average SOM was below and above 27.12 ± 20.34 mg/kg, respectively, the corresponding average BCF of Cd varied from 0.70 ± 0.63 to 0.10 ± 0.26. As the average soil Cd and As contents increased, the interactive effect of soil As and Cd on the average BCF of As decreased. The negative interaction of As and Cd in soil mitigated As accumulation in rice at certain soil Cd and As contents. Our results suggest that to achieve the large-scale control of heavy metal(loid) pollution, the interactions among multiple metal(loid)s and soil properties should be considered.

Contours of saturated and unsaturated overhanging slopes at limiting equilibrium condition

SummaryOverhangs are frequently observed in riverbanks, coastal headlands, and rock formations. The geometry of an overhang is an input into most slope stability analyses and is often idealised or back‐calculated from empirical data. This study investigates the geometries of overhang slopes, which exist while in limiting conditions satisfying static equilibrium with soil strength governed by the Mohr‐Coulomb failure criterion. The overhanging contour is formulated as the unknown in a boundary value problem and solved for using the slip line theory. Analyses consider nonhomogeneous soils, where cohesion and, if unsaturated, the contribution of suction to the effective stress vary linearly with depth. The solutions are presented in general dimensionless charts. Applications of the charts are illustrated via examples. It has been observed that soil with varying amounts of friction and cohesion could develop overhanging arches of different sizes and shapes. This study shows that the curvature of an overhang becomes more pronounced for small values of φ′. It is also demonstrated that changing the contribution of suction to the effective stress has a direct impact on the size of an unsaturated soil overhang. Overhanging slope shapes observed in reality may be different from the idealised subset studied in this paper since real slopes are not necessarily at impending failure. The real shapes may be influenced by various physical processes such as weathering, stress variations caused by cycles of wetting‐drying. Even so, the results presented in the paper indicated how key soil properties influence slope shapes, albeit it while in limiting conditions.

Development and environmental implication of pedotransfer functions of Cd desorption rate coefficients in historically polluted soils

The desorption rate is an important factor determining cadmium (Cd) ecotoxicity and pollution remediation in soils. The pedotransfer functions (PTFs) of desorption rate coefficients of fresh Cd in soils have been developed in literature. We hypothesized that the aging of Cd pollution would alter Cd desorption process. Taking historically polluted soils as the object, this study aimed at testing the hypothesis and developing new PTFs of desorption rate coefficients for historical Cd. 15 d batch extraction experiments and 13 kinetic models were employed to define Cd desorption rate coefficients in 27 historically polluted soil samples. Compared with fresh Cd, the desorption rate coefficients of historical Cd were lower, and the break time of biphasic desorption processes was retarded to 3 d (4320 min). Different with the usual models for fresh Cd desorption (e.g. parabolic diffusion and two constant rate models), the best models to mimic the historical Cd desorption processes were the pseudo first order, logarithmic, Elovich, and simple Elovich models. The rate-limiting step controlling Cd desorption was changed from the intraparticle diffusion to the interface reaction with aging of pollution. New PTFs of desorption rate coefficients of historical Cd were established (R2 ≥ 0.71). Cd desorption rate coefficients increased with organic matter and clay contents, but decreased with oxalate extractable Fe content, solution pH, cation exchange capacity, and silt content. The key soil properties influencing desorption rate coefficients were not altered by the aging of pollution. The developed PTFs could guide us to adjusting the ecotoxicity and pollution remediation of Cd in historically polluted field soils.

Do Conservation Practices Bring Quick Changes to Key Soil Properties for Resource-Limited Farmers?

Soil conservation practices such as minimum tillage, crop rotation, cover crops, and manure application have strong advocacy. Short-term evidence that these practices are beneficial might improve their adoption by resource-limited producers. A two-year study (2015–2017) was conducted on a privately-owned small, limited-resource farm in southwestern Kentucky to evaluate how cover crops and manure application, alone or in combination, influenced soil nutrient availability, nitrogen mineralization, and crop yield. Three fertilization treatments were used: 1) poultry manure; 2) chemical fertilizers (urea, diammonium phosphate, and potash); and 3) a non-fertilized control. A second set of treatments consisting of presence or absence of winter cover crop was used within each fertilization treatment. The cover crop consisted of a cereal rye (Secale cereale L.), Austrian winter pea (Pisum sativum L.), and crimson clover (Trifolium incarnatum L.) mix. Summer crops consisted of a no-till maize (Zea mays L.) - soybean (Glycine max L.) rotation. Soil samples were taken before and after each summer crop season and analyzed for bulk density, organic carbon content, pH, cation exchange capacity, total phosphorus (P), potassium (K), trace elements, and soil nitrogen (N) mineralization. Cover crops with or without manure enhanced soil N mineralization rates and increased soil extractable P and K, but did not significantly improve yield. Considering the site-specific soil conditions, cover crop and manure use may need longer-term assessment to reveal their effect on the yield and soil quality benefits, especially to resource-limited producers adopting these conservation practices.

Response of oxidative stability of aggregate-associated soil organic carbon and deep soil carbon sequestration to zero-tillage in subtropical India

Conservation agriculture (CA) practices have been recognized to enhance soil health by optimizing key soil attributes and are being implemented worldwide. But, the potential of CA to soil organic carbon (SOC) sequestration and enhancing its oxidative stability (OXS) in deep layers and aggregates are less highlighted. Thus, our aim was to study the long-term (9 years) effects of contrasting tillage treatments and residue addition on soil aggregation, OXS in bulk soils (0–5, 5–15, 15–30 and 30–60 cm) and aggregates (0–5 and 5–15 cm), and C pools and sequestration (0–5, 5–15, 15–30 and 30–60 cm). For this an experiment was laid out in a split plot design with two tillage practices in main plots (zero-tillage: ZT and conventional tillage: CT) and four residue management practices in sub-plots (No residue: NR, wheat residue: WR, soybean residue: SR and wheat + soybean residue: WR + SR) in 2008. Soil samples collected from 0–5, 5–15, 15–30 and 30–60 cm layers were analyzed. The ZT plots had ∼26 and 15% higher macroaggregate associated C than CT plots in 0–5 and 5–15 cm soil layers, respectively. In macroaggregates of first two soil layers, recalcitrant C was (a) ∼57, 76 and 63%; and (b) 85, 59 and 40% greater in WR + SR, SR and WR plots over NR, respectively. Similar trend was observed for microaggregate associated recalcitrant C. The OXS of C in ZT was ∼21% more than CT, but residue addition had no impact on OXS. In 15–30 and 30–60 cm soil layers, OXS in WR + SR plots were ∼28 and 31% greater than NR. Although deep soil layers (15–60 cm) accounted for ∼68% of sequestered C, tillage had no impact on deep soil C sequestration. About ∼85% of total SOC stock was accumulated in soil aggregates of topsoil. Contrarily, of total sequestered SOC in top soil, only ∼30% was sequestered by aggregates of that layer indicating the role of silt + clay fraction in SOC sequestration in tropical Inceptisol. Thus, SOC sequestration in tropical soil is very sluggish and would require long time to meet saturation deficit. Interestingly, crop yield was significantly influenced by active and labile C of bulk soils and aggregates, but not by recalcitrant C in ZT plots. Thus, ZT in combination with crop residue retention has great potential in enhancing deep soil C sequestration and C stability of soil aggregates to sustain soil health and crop production.

VIV simulation of riser-conductor systems including nonlinear soil-structure interactions

This paper presents a fully three-dimensional numerical approach for analyzing deepwater drilling riser-conductor system vortex-induced vibrations (VIV) including nonlinear soil-structure interactions (SSI). The drilling riser-conductor system is modeled as a tensioned beam with linearly distributed tension and is solved by a fully implicit discretization scheme. The fluid field around the riser-conductor system is obtained by Finite-Analytic Navier-Stokes (FANS) code, which numerically solves the unsteady Navier-Stokes equations. The SSI is considered by modeling the lateral soil resistance force according to nonlinear p-y curves. Overset grid method is adopted to mesh the fluid domain. A partitioned fluid-structure interaction (FSI) method is achieved by communication between the fluid solver and riser motion solver. A riser-conductor system VIV simulation without SSI is firstly presented and served as a benchmark case for the subsequent simulations. Two SSI models based on a nonlinear p-y curve are then applied to the VIV simulations. Also, the effects of two key soil properties on the VIV simulations of riser-conductor systems are studied.

Doymamış Kumlarda Toprağın Suyu Tutma Eğrisi Tayini, Karşılaştırmalı Çalışma - Asılı Kolon Tekniğine Karşı Filtre Yöntemi

Soil water retention characteristic is the key soil property used in many applications in the fields of irrigation, hydrology, geotechnical engineering and soil science in general and there are different methods used to obtain SWRC. Filter paper method and Hanging column test methods are two of them. The use of filter paper method for sands is quite limited in the literature in which only a number of studies have been conducted using this method. This study, therefore, aims to use the filter paper method for measuring matric suction for two different types of sands. Samples were prepared using the water pluviation technique. The samples were left to dry out and then monitored by weight to obtain different values of degree of saturation. This is to extend suction measurement beyond the residual suction and to fully define the shape of the soil water retention curve. The filter paper method then was validated with the hanging column technique, which is a method of controlling and applying suction. The obtained results are presented in order to highlight the differences / similarities between the methods and the advantages / disadvantages of each one. Although the FP is an indirect method of measuring suction in unsaturated soils, it has not been utilized broadly for fine-grained unsaturated sands. The use of the filter paper method for unsaturated fine sands is quite limited in the literature in which only a number of studies can be found using the filter paper method for unsaturated sands. Therefore, this paper provides an insight on the use of filter method for unsaturated fine sands. Testing two sand soil with different particle size distribution showed that Soil 1 is better than Soil 2 to be used for FP method. And this result is a good show for the range of utilization of FP method in fine sand soil.

Assessing the influence of soil abiotic and biotic factors on Nostoc commune inoculation success

A possible approach to restore drylands is to recover biocrusts by inoculating cyanobacteria. Many studies have demonstrated the ability of cyanobacteria to successfully colonize soil and improve its functions. However, most studies have focused on the abiotic factors influencing the inoculation success, overlooking biotic factors. We examined the influence of the soil indigenous community on the inoculated cyanobacteria by sterilizing soils and analyzing its effects on several key soil properties. Nostoc commune was inoculated under laboratory conditions on two soil types with different levels of degradation and under two watering frequencies. All treatments were carried out in natural and sterilized soils. The analysis of the cyanobacterial coverage (30–50% in all inoculated soils), chlorophyll a, visible albedo, roughness, water repellency, organic carbon (OC) and exopolysaccharides (EPS) content showed that cyanobacterial inoculation succeeded, improving soil properties that varied depending on the soil type. The sterilization of soils had little effect: in less degraded soils, the results suggest a faster growth of the indigenous community reaching coverage values of 10% and an interaction with the inoculum that led to a decrease in 2 and 0.3 g Kg−1 of OC and TB-EPS, respectively; in more degraded soils, the community reduced the cyanobacterial coverage around 11%, suggesting competitive interactions. N. commune can be employed to restore lifeless soils. Also, the analysis of native soil community should be considered before field inoculation to plan appropriate methodologies.

Temporal Effects of Biochar and Dairy Manure on Physicochemical Properties of Podzol: Case from a Silage-Corn Production Trial in Boreal Climate

A field experiment was conducted to evaluate the effects of biochar and dairy manure (DM) on physicochemical properties of podzolic soils, as well as to establish the relationships between selected physicochemical properties and soil electrical conductivity (EC) in a silage-corn production system. Nutrient requirements of the crop were met through different nutrient sources considering soil nutrient status, nutrient availability from DM (DM, DM + biochar) and regional crop nutrient recommendations. Experimental treatments included control, inorganic nitrogen (IN), IN + biochar, IN + DM, and IN + DM + biochar. DM was applied at 30,000 L ha−1, whereas biochar was applied at 20 Mg ha−1 and mixed within the top 20 cm of the soil. Disturbed soil samples as well as time domain reflectometry (TDR) measurements were collected from treatment plots on four field days. Results showed no significant (p > 0.05) treatment effects on soil pH and cation exchange capacity (CEC) within each field day. However, significant temporal effects were recorded for pH, EC, apparent electrical conductivity (ECa) and electrical conductivity of the soil solution (ECw). Soil depth (0–10 cm and 10–20 cm) had no significant effect on treatments. Significant positive correlations were recorded for EC with soil organic carbon and CEC (ECa, ECw 0–10 cm, & 10–20 cm, p = 0.000). Correlation results show that ECa measurements as a proxy to investigate the variability of key soil properties over large areas, but further investigation between ECa data and soil properties should be carried out to address uncertainties associated in predicting these properties.

Electromagnetic-induction and spatial analysis for assessing variability in soil properties as a function of land use in tropical savanna ecosystems

Identifying spatial patterns in the variability of key soil properties to delineate the extent of land degradation could ensure efficient management of natural resources in terrestrial ecosystems. However, little is still known in tropical savannas that are subjected to indiscriminate land use. We evaluated the soil variability at the plot-scale in a terrestrial tropical ecosystem subjected to varying land use/land cover management to assess the impact of uncontrolled land uses on the soil natural capital. The non-invasive, time/cost efficient electromagnetic induction (EMI) technique was assessed for its potential, to determine the effect of land uses on soil spatial variability in a changing land use gradient from pristine land use/land cover conditions. The investigation was carried out in a natural tropical ecosystem in Aripo, Trinidad with soils of predominantly ultisols order and influenced by anthropogenic disturbances. EMI-based apparent electrical conductivity (ECa) measurements were obtained at two depth ranges (shallow = 0–0.5 m and deep = 0–1.5 m). Soil properties showed that the residential anthropogenic land use had a higher mean apparent electrical conductivity shallow (ECas) value (ECas = 305.9 mS/m) than all other land uses. Higher ECas values in the residential site suggest that human influences can increase the magnitude of electrical conductivity, which can alter the biogeochemical cycles of the soil affecting services provided by the ecosystem. Also anthropogenic land use/land covers exhibited lower coefficient of variation for soil texture (silt and clay) than natural land uses, indicating lower sensitivity of soil texture to land use due to the mixing of soils, which encourages uniformity in anthropogenic sites. Soil texture dominated the ECas signal in the natural land use/land covers with the relationship between ECas and silt in the Forest (r = 0.486) and Grass (r = − 0.495) significant at P < 0.05. Soil texture showed greater sensitivity to land use in natural sites than in anthropogenic sites. The dominance of soil texture in the natural sites indicates that in tropical soils that are predominantly light textured (clay content < 21%), silt content controls the EMI signal, which can become of low influence following disturbance. The magnitude of electrical conductivity can increase due to human influences. This can alter the biogeochemical cycles of the soil, affecting services provided by the ecosystem.

Quantifying Soil Phosphorus Dynamics: A Data Assimilation Approach

AbstractThe dynamics of soil phosphorus (P) control its bioavailability. Yet it remains a challenge to quantify soil P dynamics. Here we developed a soil P dynamics (SPD) model. We then assimilated eight data sets of 426‐day changes in Hedley P fractions into the SPD model, to quantify the dynamics of six major P pools in eight soil samples that are representative of a wide type of soils. The performance of our SPD model was better for labile P, secondary mineral P, and occluded P than for nonoccluded organic P (Po) and primary mineral P. All parameters describing soil P dynamics were approximately constrained by the data sets. The average turnover rates were labile P 0.040 g g−1 day−1, nonoccluded Po 0.051 g g−1 day−1, secondary mineral P 0.023 g g−1 day−1, primary mineral P 0.00088 g g−1 day−1, occluded Po 0.0066 g g−1 day−1, and occluded inorganic P 0.0065 g g−1 day−1, in the greenhouse environment studied. Labile P was transferred on average more to nonoccluded Po (transfer coefficient of 0.42) and secondary mineral P (0.38) than to plants (0.20). Soil pH and organic C concentration were the key soil properties regulating the competition for P between plants and soil secondary minerals. The turnover rate of labile P was positively correlated with that of nonoccluded Po and secondary mineral P. The pool size of labile P was most sensitive to its turnover rate. Overall, we suggest data assimilation can contribute significantly to an improved understanding of soil P dynamics.

Orthodox Soil Science versus Alternative Philosophies: A Clash of Cultures in a Modern Context

In Australia, orthodox soil scientists dealing with land management and alternative practitioners who promote ‘regenerative agriculture’ have not been communicating and engaging effectively with each other. Over many years, scientists in the Commonwealth Scientific and Industrial Research Organization (CSIRO), state departments and universities have made significant achievements in mapping soil distribution, describing soil behaviour and identifying key soil properties and processes that are fundamental to healthy soil function. However, many alternative practitioners are dismissive of these achievements and highly critical of orthodox soil science. Yet many of the tools of soil science are essential to conduct evidence-based research towards elucidating how and why the exceptional results claimed by some alternative practitioners are achieved. We stress the importance of effective engagement and communication among all parties to resolve this ‘clash of cultures’.

Long-Term Effects of Different Passages of Vehicular Traffic on Soil Properties and Carbon Storage of a Crosby Silt Loam in USA

The passage of vehicles with heavy axle loads causes soil compaction, and this adversely affects soil properties and crop yield. The adverse effects can persist for several years due to significant changes in key soil properties. However, the mechanisms of the aforementioned effects are not well understood for conservation agriculture (CA) (e.g., no-till (NT)) wherein the use of heavy machinery is considerably common. Therefore, known compaction forces (0 Mg load for compaction (NT-0, control), two passages of 2.5 Mg water wagon axle load (NT-2), and four passages of 2.5 Mg water wagon axle load (NT-4)) were applied to all the plots annually for 20 consecutive years. The experiment was established in 1997 at the Waterman Agricultural and Natural Resources Laboratory (WANRL), Ohio State University, Columbus, Ohio. Each treatment was replicated thrice. Soil samples were obtained in November 2016 to determine the effects of variations in the axle load and vehicular passages on carbon (C) and nitrogen (N) storage and selected soil properties of a Crosby silt loam soil under NT-based corn-soybean rotation with residue retention in Central Ohio, USA. Three locations were also randomly selected in an adjoining natural woodlot (WL) soil plot and sampled (30 m away from the compaction field) to compare the effects of vehicular traffic on soil under NT with WL soil. Results revealed that soil bulk density (ρb) and total porosity at 0–10 and 10–20 cm depths were not affected by the passages of vehicular traffic for 20 years under the NT system. The penetration resistance (PR) (1.86 and 2.03 MPa at 0–10 and 10–20 cm soil depths, respectively) was significantly higher under NT-4 compared with that under other treatments. Saturated hydraulic conductivity at 0–10 and 10–20 cm soil depths ranged from 19.7 to 31.4 and 18.5 to 29.5 mm d−1, respectively, across all the treatments. The proportion of macroaggregates (> 0.25 mm) and microaggregates (< 0.25 mm), mean weight diameter and geometric mean diameter of aggregates, pH, electrical conductivity, and C and N contents and storage did not differ significantly between the treatments at either of the sampling soil depths. The data indicated that 2 to 4 passages of vehicles with 2.5 Mg of axle load did not cause significant compaction of the Crosby silt loam under NT compared with that under natural WL. Therefore, the continuous cultivation of row crops with NT and residue retention is feasible with passages of vehicular traffic for well-drained soils in Central Ohio.