Soil Physical Parameters Research Articles

Investigation on the influence of the Bohai Sea Geological Environment on the submarine stratum stability based on data mining: an intelligent prediction model.

The Bohai Sea has unique characteristics of the marine geological environment, with strong water closure and weak self-purification ability. Assessment of the submarine stratum stability plays an essential part in ocean engineering construction, preventing marine geological disasters and controlling environmental pollution for the Bohai strait. Nevertheless, limited studies have investigated quantitative classification of the submarine stratum stability or the influence of Bohai Sea's engineering geological environment on the submarine stratum stability using laboratory experiments and the data mining method. Thus, this study carried out physical and mechanical experiments based on the submarine borehole soil samples from the Bohai Sea. And a database containing 60 groups of submarine soil samples' mechanical parameters was established. The physical and mechanical parameters of the Bohai sea's submarine soil, i.e., depth, water content, void ratio, density, internal friction angle, and cohesion, are the prediction indicators. And the submarine soil samples' unconfined compressive strength and elastic modulus are used for quantifying the stability grade of Bohai Sea's submarine stratum. Furthermore, the submarine stratum stability prediction model was established based on the multiple linear regression analysis method and the nonlinear regression analysis method (i.e., BPNN, normal cloud, and TOPSIS method). The testing results indicate that the submarine stratum stability prediction model obtained by the linear regression analysis does not have obvious linear characteristics and gives a poor prediction performance (MAE=0.9333, MAPE=0.3, RMSE=1.2111). In contrast, the nonlinear analysis methods presented a higher fitting version. Compared to the cloud model and the TOPSIS method, the BPNN model with the lowest testing error (MAE=0.2, MAPE=0.1, RMSE=0.4472) presented the best prediction accuracy. The proposed submarine stratum prediction model has been validated as an effective submarine stratum stability prediction method and has good prospects for further ocean engineering applications.

Spatial Distribution of Quinolone Antibiotics and Its Correlation Relationship with Microbial Community in Soil of Shijiazhuang City

Microbial communities are an important component of soil ecosystems. Long-term low content antibiotic pollution will affect the structure and function of microbial communities in soil. Therefore, Shijiazhuang City was selected as the study area, in which twelve sample points were set up in September 2020. These sample sites were divided into four areas (S1, S2, S3, and S4) according to spatial orientation. Ultra-high performance liquid chromatography-mass spectrometry (HPLC-MS/MS) was applied to determine the content of typical antibiotic-quinolones (QNs) in the soil. 16S rRNA high-throughput sequencing technology was used to study the microbial community structure and diversity in the soil. The results showed that:① the total detected contents of QNs in the four areas were S3 (313.5 μg·kg-1)>S4 (65.54 μg·kg-1)>S1 (46.19 μg·kg-1)>S2 (12.63 μg·kg-1). The content of norfloxacin (NOR) was the highest (91.99 μg·kg-1), whereas the content of oxolinic acid (OXO) was the lowest (0.4486 μg·kg-1). ② For grain size, the proportion of powder (2-50 μm) was the highest (66.7%-93.2%), whereas the proportion of clay (less than 2 μm) was the lowest (2.50%-9.10%). For physical and chemical parameters, total phosphorus (TP) and ammonia nitrogen (NH4+-N) showed non-significant spatial differences, whereas nitrate nitrogen (NO3--N), nitrite nitrogen (NO2--N), and grain size showed significant spatial differences. ③ For microbial community composition, there were six dominant bacteria phyla and five dominant bacteria genera, among which Actinobacteriota (18.3%-34.6%) and Proteobacteria (13.6%-34.1%) were the dominant bacteria phyla, and Arthrobacter (3.24%-8.61%) and Nitrososphaeraceae (2.93%-9.46%) were the dominant bacteria genera. The diversity results showed the highest value in the S2 area (6.48) and the lowest value in the S3 area (5.89). ④ QNs and soil physical and chemical parameters significantly changed the structural composition of microbial communities, and OXO, NO3--N, and soil particle size affected the diversity of microbial communities. FLU, NH4+-N, NO2--N, and soil particle size affected the function of the microbial community. Therefore, it is necessary to further strengthen the risk control of antibiotics in the soil of Shijiazhuang City.

Identification Model of Soil Physical State Using the Takagi–Sugeno Fuzzy Neural Network

Adjusting tillage parameters according to soil conditions can reduce energy consumption. In this study, the working parameters and soil physical parameters of plowing were determined using a designed electric suspension platform and soil instrument. The soil conditions were classified into three physical states, namely ‘hard’, ‘zero’, and ‘soft’ using a fuzzy C-means clustering algorithm, taking the soil moisture content and cone penetration resistance as the grading indexes. The Takagi–Sugeno (T–S) fuzzy neural network classifier was constructed using traction resistance, operating velocity, and plowing depth as inputs to indirectly identify the soil’s physical state. The results show that when 280 groups of test data were used to verify the model, 264 groups were correctly identified, indicating a soil physical state identification accuracy of 94.29%. The T–S fuzzy neural network prediction model can achieve the real-time and accurate physical state identification of paddy soil during plowing.

Litter removal impacts on soil biodiversity and eucalypt plantation development in the seasonal tropics

The little layer of tree plantations provides primary nutrients for uptake, buffers changes in soil moisture, and provides habitat and substrate to soil epigeic fauna. However, this layer in eucalypt plantations is often removed to reduce fuel load during the fire season in the Brazilian savanna (Cerrado). Therefore, it is necessary to quantify the effects of changes in litter dynamics on the function of these plantations, on key nutrient cycling processes and on epigeic fauna diversity and abundance. In two adjacent stands (one juvenile and one mature), the consequences of two years of litter removal were quantified as monthly litterfall, leaf and fine wood litter decomposition, epigeic fauna abundance and diversity, soil biogeochemical variables, and tree diameter and basal area increments. Monthly litterfall rates in juvenile and mature stands did not change with litter removal over the study period. Annual litterfall ranged from 4.1 to 4.9 Mg ha−1a−1 in litter removal plots and from 3.9 to 4.8 Mg ha−1a−1 in control plots. Fine wood litter decomposition was slower in litter removal plots compared to controls, while leaf decomposition rates were similar in both. Two years of litter removal in the juvenile stand did not affect topsoil biogeochemical parameters but decreased available phosphorus at 20–40 cm depth relative to controls. In the mature stand, total cation exchange capacity (0–20 cm) was higher in controls (6.4 cmolc dm−3) relative to litter removal plots (6.3 cmolc dm−3), while soil moisture (0–40 cm depth) was lower in litter removal (25.45 m3 m−3) compared to control plots (26 m3 m−3) in the dry season. A non-metric multidimensional scaling ordination revealed an increased homogeneity in epigeic fauna where litter was removed. Litterfall, decomposition, diameter increment, four soil physical parameters and fourteen chemical parameters at 0–20 and 20–40 cm depth explained the differences in soil epigeic fauna composition between litter removal and control plots. Diameter increment decreased with litter removal only in the juvenile stand, which had reached its growth peak. The results indicate that removing excess litter to decrease fuel volume can alter soil biodiversity and edaphic conditions that negatively affect nutrient cycling and tree growth.

Fine-scale effect of karst rock outcrops on adjacent soil and plant communities in Southwest China

Rock outcrops (ROCs) are common structures in terrestrial ecosystems, particularly in regions characterised by karst-type landscapes. However, their effects on adjacent soil and plant communities have rarely been studied. In this study, soil physical and chemical parameters and plant biomass along distances adjacent to ROCs were investigated and compared to evaluate their effects on the surrounding environment. Thirty isolated ROCs were randomly selected from semi-humid karst grasslands in Southwest China. Rainfall and ROC runoff were collected for chemical analyses. The soil physical and chemical parameters as well as the aboveground and belowground biomass (AGB and BGB, respectively) of plants were determined at 0–30, 31–60, 61–90, 91–190, and 191–290 cm intervals, adjacent to the ROC rock–soil interface. The pH and total organic carbon and Ca contents were higher but P and K contents were lower in ROC runoff than in rainwater. A few of the soil physical and chemical parameters were significantly high in samples at 0–30 cm and corresponded with the contents in runoff. The AGB and BGB in the 0–30 cm and 31–60 cm plots were significantly higher than those located at a greater distance and correlated to the size parameters of ROCs. The maximum effective distance of ROCs was approximately 75 cm. Plant biomass increased sharply in the 0–30 cm and 31–60 cm plots, with an increase in coverage in the range of 0.7 and 1.3 m2. Our findings suggest that karst ROCs affect the physical and chemical parameters of soil and adjacent plant biomass significantly on fine scales, and these effects are correlated with the size parameters associated with ROCs, such as coverage area.

Geotechnical Mapping for Soil Physical and Mechanical Parameters and Hard Soil Depth in Badung Regency

The infrastructure is important for the great life of a region and most of the country. Therefore, infrastructure must be always in proper condition in its functionality. Furthermore, it must follow the main principle which is infrastructure asset management. In this case, geotechnical mapping is also related to the principles of Infrastructure Asset Management in planning, designing, and feasibility studies of an infrastructure project in Badung Regency, hence the infrastructure projects are better prepared. The research methods include collecting soil investigation data, processing soil investigation data, describing the results of soil investigation data with mapping tools, and geotechnical zoning with statistical analysis. The results obtain geotechnical map of Badung Regency in 2 and 3-dimensional form. The 2D results in the form of a hard soil depth map can be concluded that South Kuta District has a variation depth of 0.4 – 15 meters, North Kuta District has a variation depth of 1.5 – 5 meters, Kuta District has a variation depth of 1.5 – 10 meters, Mengwi District has a variation depth of 1.5 – 10 meters, Abiansemal District has a variation depth of 5-15 meters, Petang District has a variation depth of 5-22 meters. The 3D Zone 1 lithology map can be concluded that Zone 1 area covered with hard soil depth around 5 – 10 meter is dominated by sandy silt, silty sand, sand and a little clayey silt. That area covered with hard soil depth about 1.5 – 5 meter is dominated by clay, clayey silt, sandy silt, silty sand and sand with heterogeneous distribution. The Zone 1 area is dominated by the specific volume saturated value (γsat) range of 1.5 – 2.0 t/m3. The values > 2.0 t / m3 is found in Sading area with hard soil depth of 5-10 meters. The Zone 1 area is dominated by the range of N-SPT values = 0 - 30. The N-SPT values > 30 are found in Sading area with hard soil depth 5-10 meters.

Development of a soil quality index for sequences with different levels of land occupation using soil chemical, physical and microbiological properties

The sustainable intensification of agricultural systems through crop rotations and/or the use of winter service crops can contribute to the diversification of the systems. This alteration of the surface layer creates conditions that favor an increase in the diversity of soil microbial communities, which improves the recovery capacity of the edaphic system, thereby contributing beneficial effects to plants, soil, and ecosystem. Our objectives were: 1) to evaluate the effect of crops sequences on soil chemical, physical and microbial parameters, and 2) to develop a soil quality index (SQI) from a minimum set of indicators for cropping sequences with different levels of land occupation. A long field experiment under no-tillage was established in 2006, where soil samples were collected during three agricultural seasons (2015, 2016, and 2017). We compared the effects of four different crop sequences that included soybean (S), maize (M) and wheat (W), and also incorporated wheat as a winter cover crop (CC), being S-S, CC/S, M-W/S, and W/S-CC/M. We found that sustainable management practices, crop rotation and inclusion of CC increased soil organic carbon. The highest basic infiltration rate and lowest penetration resistance values were found for double-cropped wheat/soybean-winter cover crop/maize (W/S-CC/M), the most intensified sequence. The average microbial biomass carbon level for soybean monoculture, was reduced by 32 % compared to maize-double-cropped wheat/soybean in the three agricultural seasons, while the metabolic coefficient in soybean monoculture and winter cover crop/soybean was significantly higher. In soybean monoculture, hydrolysis of fluorescein diacetate was decreased by 28.5 %, while dehydrogenase activity was increased by 43 % with respect to double-cropped wheat/soybean-winter cover crop/maize. The abundance of fungal and bacterial communities did not reveal significant variations between sequences by quantitative PCR analysis. The SQI was constructed by selecting a minimum set of indicators based on soil chemical, physical and microbial parameters. The parameters selected by the model were soil organic carbon, total organic nitrogen, basic infiltration rate, microbial respiration and hydrolysis of fluorescein diacetate, that revealed the differences among crop sequences in response to land occupation. The inclusion of different crops increased the SQI in comparison with soybean monoculture. The double-cropped wheat/soybean-winter cover crop/maize system improved the SQI by 73 % compared to soybean monoculture. Our findings show that crop sequences with high soil occupation improved their chemical and physical properties, as well as increasing the abundance and functionality of the microbial community, which is related to a better SQI.

Evaluation of lateritic soils of Mbé for use as compressed earth bricks (CEB)

This work was carried out on the lateritic soils of Mbé in the Adamawa region of Cameroon. For this study, twenty (20) soil samples were taken from four (04) sites (Kabaa, Ndom, Mbé Norwegian camp, and Nyéssé). To assess their suitability for the production of compressed earth bricks, physical parameters were obtained by geotechnical tests to determine particle size distribution, water content, atterbergs limits, specific gravity, methylene blue value, maximum dry density (MDD), and optimum moisture content (OMC). Chemical and mineralogical properties were obtained by X-ray fluorescence and X-ray diffraction, respectively, followed by the determination of technological parameters (water absorption and mechanical properties) on compressed earth brick specimens. The results show that the studied lateritic soils contain mainly sand (52.8–90.3 wt%) and clay particles (8.4–42.1 wt%), gravel particles are slightly represented (1.1–16.3 wt%). The plasticity index of the studied materials is average (5–38%), about their methylene blue values (1–5), these soils correspond to clayey-silty soils. The materials studied are classified by the USCS as clayey sands/silty clays; according to the Highway Research Board (HRB), they are classified as A-7-5 or A-7-6 clayey soils with group index of 1 for Kabaa, 7 for Ndom, 9 for Mbé Norwegian Camp, and 12 for Nyéssé. These soils are rich in silica (SiO2, 62.6–78.1 wt%), followed by aluminum (Al2O3, 11.8–18.2 wt%) and iron oxides (Fe2O3, 3.2–8.1 wt%); other oxides are in lower proportions (<1 wt%). The mineralogical content consists mainly of clay minerals such as kaolinite, illite, smectite (montmorillonite), and non-clay minerals such as quartz, muscovite, biotite, gibbsite, and hematite. The bulk density and mechanical properties of the specimens are within the standard NC 102-115 (2007) of compressed earth bricks (CEB), which recommends minimum compressive strengths of 2 Mpa for unstabilized CEB and 4 Mpa for stabilized CEB. Water absorption of CEB and physical parameters of soils have a significant impact on the mechanical behavior of CEB. According to the test results, Mbe lateritic soils are suitable for engineering applications in the production of stabilized compressed earth bricks.

Soil water retention capacity surpasses climate humidity in determining soil organic carbon content but not plant production in the steppe zone of Northern China

Soil hydraulic properties determine water transport, distribution and storage in soils, thus affect ecosystem functioning. Soil water retention parameters, such as saturation water content (SAT), water drained upper limit (DUL) and lower limit (DLL), characterize soil water-holding capacity, thus are important for plant growth and carbon and nutrient cycling in grassland ecosystem. However, we are still unclear to what a content these soil water retention parameters may regulate plant production and soil organic matter content in natural ecosystems in semi-arid grassland environment. We investigated plant species richness (SR) and aboveground biomass (AGB), soil organic carbon (SOC) and nitrogen (SON) contents, and soil water retention and other physical parameters in the steppe ecosystems along a climate transect, which spans the desert steppe, typical steppe and meadow steppe zones in Northern China. We analyzed the relative importance of climate factors, soil water retention parameters and other soil physical parameters in regulating plant AGB and SOC and SON contents using partial correlation analysis, and quantified the contribution of each separate and combined climate and soil physical parameters in predicting plant AGB and SOC and SON contents using geographic detectors method. We found that (i) plant SR and AGB, soil SAT and DUL, and SOC and SON are all significantly inter-correlated, and increased with the increase of climate humidity. (ii) Climate, but not soil physical parameters, was the most preponderant factor in predicting plant SR and AGB. (iii) Soil physical parameters were more important than climate parameters in regulating soil organic matter content; soil DUL was the best predictor to SOC content. Our results suggest that soil water retention parameters especially soil DUL, may play a greater role than climate factors in modulating SOC content, though climate is more predominant in regulating plant SR and production. Our results imply that we need to be cautious in estimating SOC content based on climate factors and vegetation biomass or remotely-sensed vegetation indices, and that soil physical properties need also to be incorporated along with vegetation parameters for improving SOC estimation at a regional scale.

Variational data assimilation to improve subsurface drainage model parameters

• Identification of the most influential model parameters using the global adjoint SA. • Variational data assimilation significantly reduces the water volume discrepancy. • The gradient-based stochastic procedure performs without the need for the prior. • A new hybrid BV method offers an automatic tool to select a robust parameter set. Variational data assimilation (VDA) has been implemented to enhance the estimation of the unknown input parameters of a new agricultural subsurface drainage model (SIDRA-RU) through assimilating drainage discharge observations. The adjoint model of SIDRA-RU has been successfully generated through the generic automatic differentiation tool (TAPENADE). First, the adjoint model is used to explore the local and global adjoint sensitivities of the valuable function defined over the drainage discharge simulations with respect to model input parameters. Next, the most influential parameters are estimated by applying the Variational DA approach. The performed sensitivity analysis shows that the most influential parameters on drainage discharge are those controlling the dynamics of the water table; the second most influential parameters manage the drainflow start of each drainage season. Compared to an alternative gradient-free calibration performance, the estimation of these governing parameters by the variational method improves the overall quality of the drainage discharge prediction, in particular in terms of the cumulative water volume. Improved parameters generate less than 5 mm (1%) of the discrepancy between simulated and observed water volumes, based on the five years of daily discharge observations on the Chantemerle agricultural parcels (36 ha). Preliminary numerical tests have shown the potential presence of multiple local minima, thus pointing out the equifinality issues. The latter can be highlighted by the self-compensation of both the physical soil parameters and the main conceptual parameters. For improving the robustness of the parameter estimates, a novel hybrid “Bayesian Variational” method is suggested. This method is based on the Bayesian averaging of an ensemble of optimal estimates.

Polyester microplastic fibers affect soil physical properties and erosion as a function of soil type

Abstract. Microplastics are recognized as a factor of global change contaminating many environmental compartments. Agricultural soils are very likely to receive microplastic contamination and are of particular concern due to their role in food production. Microplastic fibers have already been shown to be able to affect soil properties, but their effect on different soil types is poorly understood. Moreover, limited information is available on how the presence of this pollutant can affect soil water erosion processes, which are extremely important issues in many environments. In the light of this, we performed two experiments (carried out on a microscale) to investigate how the presence of polyester microplastic fibers affects soil physical and hydrological parameters and processes such as aggregate formation and soil erosion in three different agricultural soil types (a Vertisol, an Entisol, and an Alfisol). Our data show that the effects of polyester microplastic fibers on soil physical parameters and erosion are strongly dependent on soil type. We found that microplastic fiber contamination can affect soil bulk density, capacitive indicators of soil physical quality, and decrease the formation of new aggregates (labile in the incubation period applied in our experiments) but did not affect their stability in water. However, we found that polyester microplastic fibers reduced soil loss and sediment concentration, especially in the most erodible soils. In this paper, we provide some hypotheses, but certainly future data are still needed to confirm or disprove our hypotheses. Overall, our results highlight the importance of broadly exploring soil properties, such as texture, mineralogy, organic carbon content, etc., to better understand how the various soil types respond to microplastic fiber contamination.

Effects of Sewage Sludge Application on Plant Growth and Soil Characteristics at a Pinus sylvestris var. mongolica Plantation in Horqin Sandy Land

The application of domestic sewage sludge (SS) may affect plant growth and soil quality through altering nutrient availability. However, the effect of SS application on the plant–soil system in sandy soils is poorly understood. In this study, we established SS application treatment plots (SL, 25 t ha−1) and control treatment plots without sewage sludge application (CK, 0 t ha−1). SS was applied to the soil surface of a Mongolian pine (Pinus sylvestris var. mongolica) plantation in Horqin Sandy Land, Inner Mongolia, China, to assess its potential effects on plants and soil. We analyzed tree growth performances (tree height, basal diameter, and diameter at breast height), understory traits (species diversity, coverage, and aboveground biomass), soil physical and chemical parameters (nutrient content, dissolved organic carbon, soil water content, bulk density, pH), and proxies of ecosystem services (soil organic carbon and total nitrogen stocks). The results showed that SS addition not only significantly increased soil nutrient contents, but also markedly enhanced aboveground productivity and plant coverage. Specifically, SS addition decreased soil bulk density and increased concentrations of soil organic carbon, total nitrogen, and total phosphorus and mineral nitrogen, and it also increased soil carbon and nitrogen stocks. Furthermore, the addition of SS significantly increased soil dissolved organic carbon contents and enhanced the fluorescence intensities of dissolved organic carbon components (humic acid-like and UV fulvic acid-like) in the topsoil (0–5 cm). This study provides evidence that SS is an acceptable, and possibly preferred organic fertilizer for improving the soil quality and tree–grass growth of Mongolian pine plantations.

Soil physical properties as influenced by different agroforestry systems in Haryana

The present investigation was conducted out at Research Farm, Department of forestry, CCS Haryana Agricultural University, Hisar to assess the influence of different agroforestry system on dynamic soil physical parameters. Soil samples were collected randomly from varying depths viz. 0-15, 15-30, 30-60 and 60-90 cm from different agroforestry system viz. Poplar + wheat, Eucalyptus + barley, Melia + wheat, Shisham + mustard, wheat, barley and mustard. Analysis of different physical properties was done at all depths except infiltration rate. Infiltration rate was observed at surface depth (0-15 cm) only. Soil texture, being a static property was not found to be affected by agroforestry system. Non-significant effect was observed in case of soil texture among different agroforestry system. Poplar + wheat recorded maximum infiltration rate which was at par with Eucalyptus + barley, Melia+ wheat and Shisham + mustard agroforestry system. Saturated hydraulic conductivity was maximum under Eucalyptus + barley based agroforestry system. Theresult of the study showed that tree-based agroforestry system can significantly improve the soil physical properties.

Effect of reduced tillage under various mulch types on soil fertility and yield of an organic pepper crop

The effects of mulching on soil characteristics and plant development for pepper crops conducted in organic farming were studied in the Sahel coast of Tunisia. The types of mulching used for tests are straw mulching, compost mulching, and plastic mulching which were compared with bare soil without mulching (control). The soil characteristics under these different mulching systems were evaluated by soil physical and biological parameters such as penetration resistance at 0-60 cm layer, microbial biomass, organic matter, and water content at 0-20 cm layer. Measurements were performed every week for 50 days. The obtained results showed that compost mulching led to a better growth rate and improved the structural and water state of cultivated soil by decreasing its resistance to penetration and increasing its organic matter content. It can be concluded that the "Beldi" organic pepper crop under conservation tillage and compost mulching has presented the best combination thus leading to motivating results such as the positive effects of soil physical properties and microbial biomass on the final crop yield.

Soil tillage and machinery traffic influence soil water availability and air fluxes in sugarcane fields

Intensive soil disturbance by conventional tillage and heavy machinery traffic for planting, cultivation, and harvesting operations are the main causes of soil compaction and degradation of soil physical quality in sugarcane fields. However, the adoption of conservation soil tillage practices, such as no-till and reduced tillage associated with traffic control have been proposed as a key strategy to preserve soil physical quality, enhancing water availability and air fluxes. Nevertheless, the effects of reduced tillage associated with traffic control in sugarcane fields are still not well documented. A study was carried out to quantify soil water availability and air flux indicators in two soils with contrasting textures (named Sandy Loam and Clayey soil) under conventional and reduced tillage practices associated with and without controlled machinery traffic in central-southern Brazil. Soil physical parameters such as bulk density, total porosity, air-filled porosity, air permeability, pore continuity index, and the least limiting water range (LLWR) were measured. In both soils, there was no difference between conventional and reduced tillage in bulk density, air permeability, and LLWR. However, reduced tillage with non-traffic decreased bulk density and increased macroporosity, air-filled porosity, air permeability, pore continuity, and LLWR in Sandy Loam soil. In Clayey soil, the bulk density and LLWR did not change between tillage practices, but air permeability and pore continuity index were larger under reduced tillage with non-traffic. These results highlighted that soil disturbance by conventional tillage does not improve the water availability and air permeability during the crop cycle. However, the traffic control is essential to support the adoption of reduced tillage in sugarcane fields, preserving soil water availability and air fluxes for the subsequent ratoons. Reduced tillage and traffic control are two of the most important pillars for reducing soil compaction and promoting sustainability of sugarcane production in Brazil.

Improving soil physical properties and cassava productivity through organic manures management in the southern Cameroon

Cassava cultivation causes serious soil fertility depletion in Cameroon. Organic manures can contribute to maintaining the productivity and sustainability of cassava production systems due to their availability and cheapness. This study was conducted during two successive cropping seasons (2016/2017 and 2017/2018) in the Southern Cameroon, to determine the effects of organic manures on soil physical properties, and cassava growth and yield. Tithonia diversifolia fresh biomass (TB) and poultry manure (PM) were used as organic manures. Different treatments were used, namely: (i) control (no amendment), (ii) mineral fertilizer (MF (450 kg ha−1 13-13-23 NPK + 100 kg ha−1 Urea)), (iii) two rates of TB (applied at 10 and 20 t ha−1), (iv) two rates of PM (applied at 10 and 20 t ha−1) and (v) two rates of the mixture of TB and PM (applied at 5 and 10 t ha−1 each). The experimental designed was randomized complete block with three replicates per treatment. The application of TB, PM and TB + PM (mixture) lowered bulk density by 14–22.6%, 21.5–26.2% and 18.2–25%, respectively. While total porosity and water holding capacity were increased with manure application by 9.8–15.1% and 13.3–30.3%, respectively. The mineral fertilizer had no significant effect on these soil physical parameters. Application of TB and PM either solely or mixed significantly improved growth of cassava. Stem height, stem diameter and canopy diameter increased by 34.3–60%, 17.4–30.4% and 19.7–32.7%, respectively. Organic manures performed better than the mineral fertilizer. Aboveground dry biomass and fresh tubers yield increased by 21.7–59.6 and 76.6–112.2% with organic manures, and by 23.2 and 68.5% with mineral fertilizer, respectively. The best performance of cassava in terms of fresh tubers yield (51.78 t ha−1) occurred with the mixture of TB and PM applied at 10 t ha−1 each. The study revealed that fresh biomass of Tithonia diversifolia and poultry manure can be used to improve cassava production and sustain soil productivity in the humid forest zone of Southern Cameroon.

Understanding Importance of Soil Testing and Significance of SOC on Crop Productivity

Healthy soils are important to grow healthy crops, raising healthy animals, and supporting a healthy human population through nutritionally balanced diets. As an indicator for soil health, SOC is important for its contributions to food production, mitigation and adaptation to climate change, and the achievement of the Sustainable Development Goals (SDGs). It supports multiple soil functions determining soil physical, chemical and biological quality parameters contributing to the productive capacity of soil. It improves soil structural stability by promoting aggregate formation which, together with porosity, ensures sufficient aeration and water infiltration to support plant growth. It is one of the factors that help in increasing water holding capacity, improves cation exchange capacity to hold huge quantities of positively charged nutrients such as calcium, magnesium and potassium until the plant needs them.

A comparative study of MIR and NIR spectral models using ball-milled and sieved soil for the prediction of a range soil physical and chemical parameters

This study evaluated the influence on predicted physical and chemical parameters of soil particle sizes commonly used in the infrared spectra acquisition, < 0.100 mm (ball-milled) and < 2 mm for MIR and NIR ranges, respectively. The influences were evaluated through the accuracy (RMSEP and RPIQ) results and the chemical information extracted by multivariate classification and regression models. For this a national population of soils containing 888 samples from 225 modal soil profiles, each with the reference values of sand, silt, clay, pH(CaCl2), pH(Water), total carbon, organic carbon (OC), cation exchange capacity, nitrogen, aluminium and bulk density, was used. Spectra were collected in MIR and NIR ranges using samples with both particle sizes. For each soil attribute, 29 random calibration and validation sets were generated and SVM, PLS and Cubist regression models were built. This same strategy was used to classify the soil samples according to their respective horizons (1 or 2-7) using SVM, PLS-DA and random forest algorithms. Results obtained by the randomised calibration and validation set did not present positive or negative bias on the RMSEP and RPIQ values based on soil particle sizes. In general, random variations of the RMSEP and RPIQ values were observed for all soil attributes. In addition, ball-milled and < 2 mm spectral models did not present large differences in both accuracy parameters simultaneously. The median Matthews correlation coefficient values calculated by the classification models showed minor variations of 2.61% and 0.65% for samples from both particle sizes in MIR and NIR ranges, respectively. The ‘Variable Importance in Projection’ or VIP scores, calculated by PLS and PLS-DA models, did not show any large variation in the chemical information extracted from MIR and NIR spectra for models built using samples from both particle sizes. The results from this study show that scanning ball-milled or < 2 mm sieved soil samples will result in spectra models in MIR and NIR ranges with the same accuracy and same chemical information. This suggests there is a big potential to eliminate the ball-milling sample step in soil laboratories that use MIR and NIR vibrational spectroscopy techniques to predict soil attributes, thereby reducing the time and costs associated with soil analysis.

Effects of shallow non-inversion tillage on sandy loam soil properties and winter rye yield in organic farming

Due to an expected improvement of soil quality and soil water storage, the substitution of mouldboard ploughing by reduced tillage was identified as a potential climate change adaptation measure for organic farming in a relatively dry region with a humid continental climate. In a field trial on a sandy loam soil in eastern Germany, reduced tillage was carried out to 6 cm soil depth by means of a ring cutter and compared to mouldboard ploughing with 25 cm tillage depth. In the present study, the influence of ring cutter tillage on soil properties was investigated for the first time. The effects of shallow ring cutter tillage on soil physical parameters, soil organic matter distribution, soil mineral nitrogen content, total nitrogen uptake by the crop, root content, and grain yield of organically grown winter rye (Secale cereale L.) were analysed in the uppermost 20 cm of a sandy loam soil and compared to those of mouldboard ploughing.Under ring cutter tillage, soil bulk density was in 8–20 cm soil depth by up to 15% higher than under mouldboard ploughing. In 9–15 cm soil depth, ring cutter tillage resulted in smaller contents of coarse macropores and mesopores, more micropores, and an 11% smaller available water capacity compared to mouldboard ploughing. The total nitrogen uptake by winter rye was in the ring cutter treatment by up to 44% smaller than in the mouldboard plough treatment. Root content was up to 209% higher in 1–6 cm soil depth and up to 71% smaller in 8–20 cm soil depth after ring cutter tillage than after mouldboard ploughing. Winter rye yield declined by 22–43% in the ring cutter treatment relative to the mouldboard plough treatment.Shallow ring cutter tillage resulted in a root growth-restricting soil compaction in the non-tilled soil layers below 6 cm depth and led to a limitation of nitrogen mineralisation until spring. Both effects likely caused the considerable reduction of crop yield. The results suggest that shallow ring cutter tillage in organic farming seems to be not suitable for sandy loam soils as long as the risk of a soil compaction-induced limitation of root growth and nitrogen supply cannot be minimised.

Investigating Plant Response to Soil Characteristics and Slope Positions in a Small Catchment

Methods enabling stakeholders to receive information on plant stress in agricultural settings in a timely manner can help mitigate a possible decrease in plant productivity. The present work aims to study the soil–plant interaction using field measurements of plant reflectance, soil water content, and selected soil physical and chemical parameters. Particular emphasis was placed on sloping transects. We further compared ground- and Sentinel-2 satellite-based Normalized Vegetation Index (NDVI) time series data in different land use types. The Photochemical Reflectance Index (PRI) and NDVI were measured concurrently with calculating the fraction of absorbed photochemically active radiation (fAPAR) and leaf area index (LAI) values of three vegetation types (a grassland, three vineyard sites, and a cropland with maize). Each land use site had an upper and a lower study point of a given slope. The NDVI, fAPAR, and LAI averaged values were the lowest for the grassland (0.293, 0.197, and 0.51, respectively), which showed the highest signs of water stress. Maize had the highest NDVI values (0.653) among vegetation types. Slope position affected NDVI, PRI, and fAPAR values significantly for the grassland and cropland (p &lt; 0.05), while the soil water content (SWC) was different for all three vineyard sites (p &lt; 0.05). The strongest connections were observed between soil physical and chemical parameters and NDVI values for the vineyard samples and the selected soil parameters and PRI for the grassland. Measured and satellite-retrieved NDVI values of the different land use types were compared, and strong correlations (r = 0.761) between the methods were found. For the maize, the satellite-based NDVI values were higher, while for the grassland they were slightly lower compared to the field-based measurements. Our study indicated that incorporating Sentinel-derived NDVI can greatly improve the value of field monitoring and provides an opportunity to extend field research in more depth. The present study further highlights the close relations in the soil–plant–water system, and continuous monitoring can greatly help in developing site-specific climate change mitigating methods.