Soil Fragments Research Articles

Soil properties and climate drive ponderosa pine seedling presence in the southwestern USA

A continual improvement of our understanding about factors that influence tree regeneration is needed to inform landscape-scale restoration efforts across the western USA. This is increasingly important because changing climate and disturbance regimes will influence where restoration efforts should be implemented across landscapes. In this study, we used Forest Inventory and Analysis (FIA) data to model ponderosa pine (Pinus ponderosa C. Lawson var. scopulorum Engelm.) seedling presence across FIA plots in Arizona and New Mexico, USA. Additionally, we analyzed archived soil samples from FIA plots for percent clay, silt, and sand; samples were collected from the upper 20 cm of the mineral soil. Soil particle size is correlated with soil parent material, which has been shown to influence ponderosa pine regeneration. We used structural equation modeling to determine the relative importance of direct and indirect factors affecting ponderosa pine seedling presence. For the 0–10 cm depth increment of the mineral soil, soils with high inorganic C (carbonate) concentrations, a low percentage of coarse fragments (>2 mm) in the mineral soil, a low percentage of sand in the fine fractions (<2 mm) of the mineral soil, and low average May minimum temperature had the greatest probability of ponderosa pine seedling presence. Average annual precipitation also influenced pine regeneration through its negative correlation with inorganic C concentration. A partial explanation for the latter correlation could be that carbonates in the upper soil horizons leach into lower layers over time in areas with greater precipitation. Inorganic C concentration was also associated with soil parent material and was correlated with the soil cation exchange capacity and several macronutrient concentrations. Overall, our results indicate that soils and climate are key drivers of tree regeneration in the southwestern USA. Other factors such as the forest overstory, including the presence of seed trees, and the herbaceous plant community can also influence ponderosa pine regeneration. However, these factors were not statistically significant in the current study, likely because a small subset of FIA plots were used in the analyses. As soils are collected on additional FIA plots, new models of tree regeneration based on the current structural equation model could be evaluated and refined. Our results also indicate that information about the soil series associated with FIA plots would be useful for modeling tree regeneration, especially because soil series are commonly used by land managers in decision-making processes.

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The changing dynamics of agricultural lands throughout 2005-2020 has been investigated. Transformation of agricultural lands is related to various unresolved legislative issues. According to the research results the efficient use of agricultural lands is interfered with the current legislative environment, degradation factor, huge amount of unused soils registered in the agricultural land assets and soil fragmentation. To eliminate the mentioned factors and to reduce their effect, it is necessary to make legislative changes and to implement land management activities.

Quantifying organic carbon stocks using a stereological profile imaging method to account for rock fragments in stony soils

Accounting for soil organic carbon (SOC) in stony soils is critical for estimating global SOC stocks. However, accurate and cost-effective assessments of SOC stocks in stony soil profiles remain challenging due to the difficulties in accurately determining the rock fragment volume. The objective of this study was to develop a stereological profile imaging method for rock fragment volume fraction estimation and SOC stock assessment in stony soil profiles. Three soil profiles with different rock fragment lithologies, concentrations, and distributions were imaged and quantitatively sampled. The stereological profile imaging method reproduced consistent estimation of the 3-dimensional rock fragment number density distribution and volume fraction compared to the direct measurement. The SOC stocks of the three stony profiles estimated by visual estimation, profile imaging, and stereological profile imaging methods were also assessed and compared to direct measurement. The average difference in total SOC stock between direct measurement and visual estimation, profile imaging, and stereological profile imaging methods was 0.32, 0.17, and 0.09 kg m−2, respectively. The total profile (0–100 cm) SOC stock for profile 2 differed among the visual estimation and profile imaging methods, but estimated SOC stock from the proposed method did not differ from direct measurement for the three profiles. Results also showed that the differences in SOC stock assessment between rock fragment estimation methods increased with rock fragment concentration. The proposed method was less affected by rock fragment concentration and was more stable compared to the visual and profile imaging methods. The stereological profile imaging method was demonstrated to be a reasonably accurate method for the quantification of rock fragment number density distribution, volume fraction, and SOC stock in stony soil profiles.

Simulation modeling of the soil flow movement process in the air, supplied by a ground gun while extinguishing a forest fire

The article presents a technological scheme of the operation process of a soil-throwing unit, which has a milling-throwing working body and a guiding casing, and a developed simulation model of the process of movement in the air of a directed flow of soil particles supplied by a soil launcher when extinguishing a forest fire. The aim of the study is to assess the influence of soil and air flow parameters on the indicators of its suitability for extinguishing a ground forest fire by using simulation modeling of the process. The study of this work covers the process of flow, which received the necessary impulse from the milling cutters of the soil launcher. The theoretical description of this direction of research is complex, since it considers both the packing of flying particles and individually detached spherical elements that come into contact with air particles, also presented in the form of discrete elements. As a result of modeling the movement of soil in the air, a vertical cut of the system of fragments of soil and air, graphs of dependences on time, the average distance between soil elements and the average resistance force of the air environment were obtained.

Pilot bioremediation of contaminated soils by hydrocarbons, from an electricity production and distribution site in Ouagadougou, Burkina Faso

The bioremediation of polluted soils by hydrocarbons is a set of decontamination techniques which exploit the depolluting activity of living organisms in order to reduce the toxicity, mobility or quantity of a contaminant in the environment. This work has enabled the bioremediation of a soil contaminated with hydrocarbons by exploiting endogenous microorganisms of the environment. The depollution method used was the off situ treatment. Thus, a pilot sample of polluted soil excavated on a site was conveyed to another site accommodating a structure specialized for the biotreatment of the polluted environments. The soil was successively placed in heaps (heap 1 and heap 2) on two compartments of a treatment platform and submitted for 08 months to bio-pollution with an improvement in the living conditions of endogenous microorganisms like contribution of substrates, periodic watering and reversal of the medium. Previously, a pre-treatment was carried out on the samples including screening, breaking of large fragments of soil and homogenization. A total oil reduction rate of 62.32% was observed for heap 1 and 67.92% for heap 2. The temperature, pH and humidity of the two heaps were varied, respectively between 16 and 39°C, 6.5 and 8 and 35 and 80%. Otherwise, microbiological analysis showed a proliferation of aerobic microflora such as bacteria and molds in the two soil piles. Key words: Hydrocarbon, polluted soil, bioremediation, microorganisms.

Evaluation of Abiotic Controls on Windthrow Disturbance Using a Generalized Additive Model: A Case Study of the Tatra National Park, Slovakia

Windthrows are the most important type of disturbance occurring in the forests of Central Europe. On 19 November 2004, the strong northeastern katabatic winds caused significant damage and land cover change to more than 126 km2 of spruce forests in the Tatra National Park. The risk of subsequent soil erosion and accelerated runoff has increased in the affected habitats. Similar situations may reoccur this century as a consequence of climate change. A geographical approach and detailed research of the damaged area with more comprehensive statistical analyses of 47 independent variables will help us to obtain a deeper insight into the problem of windthrow disturbances. The results are based on a detailed investigation of the damaged stands, soil, and topography. A comprehensive input dataset enabled the evaluation of abiotic controls on windthrow disturbance through the use of a generalized additive model (GAM). The GAM revealed causal linear and nonlinear relationships between the local dependent quantitative variables (the damage index and the uprooting index) and independent variables (various soil and topography properties). Our model explains 69% of the deviance of the total damage. The distribution of the wind force depended upon the topographical position—mainly on the distance from the slope’s foot lines. The soil properties (mainly the soil skeleton, i.e., rock fragments in stony soils) affect the rate and manner of damage (uprooting), especially on sites with less wind force. Stem breakage with no relation to the soil prevailed in places with high force winds. The largest number of uprooted trees was recorded in localities without a soil skeleton. The spruce’s waterlogged shallow root system is significantly prone to uprooting. The comprehensive research found a significant relationship between the abiotic variables and two different measures of forest damage, and can expand the knowledge on wind impact in Central European forests.

Gradients of geochemical change in relic charcoal hearth soils, Northwestern Connecticut, USA

Relic charcoal hearths (RCHs) have produced distinct legacy effects in forest soils around the world. Recently, LiDAR imagery has revealed thousands of 18th–early 20th century RCHs in Litchfield County, Connecticut, USA; however, the effects of RCHs on a landscape-scale are not well-documented, particularly fine-scale heterogeneity within RCHs and surrounding soils. This study examines the long-term impacts of charcoal production by measuring RCH soil chemical and physical properties from three perspectives: (1) compared to adjacent reference sites (RSadj), (2) laterally at systematic distances away from the RCH center, and (3) vertically within the RCH soil profile. Mean charcoal abundance was greater in RCH sites than RSadj (p < 0.01). Soil organic carbon (SOC), total C, and extractable Ca2+, Mg2+, Na+ were greater in RCH sites as compared to RSadj (p < 0.01), and available phosphorus (p < 0.01), K+, and trace elements (Mo, Ag, Hg, and Se) were lower (p < 0.05). In vertical profiles, many RCHs had 2 charcoal-rich layers within the anthropic epipedon, demonstrating multiple episodes of charcoal production. Peaks in SOC, C:N, Ca2+, Mg2+ corresponded with charcoal-rich layers. Systematic transect sampling across the RCH boundary identified charcoal fragments in soils at distances up to 25 m beyond the RCH boundary, increasing the surface-level (0–15 cm) area of impact for an individual RCH by more than 30×, from a 5-m radius (RCH area = 78.5 m2) to a 30-m radius (total area of impact = 2826 m2). These findings capture fine-scale variations within and among RCH and reference sites and contribute to estimating the total area of forest soils impacted by historical charcoal production.

Modelling the aggregate structure of a bulk soil to quantify fragmentation properties and energy demand of soil tillage tools in the formation of seedbeds

Designing tillage tools to promote only the necessary amount of soil fragmentation with minimum power input have great potential to reduce production costs concomitantly with environmental impacts. Thus, it was developed a model using discrete element method (DEM) of a bulk soil that accounts for the mechanical behaviour of soil aggregates and implemented an aggregate size classifier algorithm to quantify aggregate size distribution and the location of particle bond breaks promoted by tillage in different positions of the soil bin. Using this numerical approach, simulations of tillage activities were carried out for two furrow openers for sugar cane planting: a conventional one and a new tool concept with distinct soil fragmentation principle. The calibrated DEM model was able to reproduce the empirical measurements of soil friability and power demand of tillage. Through the model it was possible to quantify the level of soil structural fragmentation caused by tillage, revealing specific details of aggregate breakage promoted by the evaluated tools. The new tool concept showed potential to decrease the power demand by 28.5% at the same time it increases the fractal fragmentation by 10% in comparison to the conventional tool. From these simulations it was estimated that the implementation of the new tool in the Brazilian sugarcane production may reduce fuel consumption by up to 16%.

Ecohydrological effects of litter cover on the hillslope-scale infiltration-runoff patterns for layered soil in forest ecosystem

The litter interception of rainfall have great effect on the water balance in the hydrological process, especially for the process of infiltration and runoff. Infiltration plays a significant role in soil erosion, evapotranspiration, and overland flow. Runoff generation is a main component of the hydrological cycle, and the simulations of soil moisture can improve infiltration process modeling. And hillslope is the basic unit of hydrological response and the key place of hydrological process. It is also the basis of distributed hydrological simulation to explore and understand the hillslope scale rainfall infiltration and runoff generation. A hillslope infiltration-runoff model in mountain area was established, including vegetation and litter interception. Field experiments on runoff yield and confluence of natural precipitation were carried out for model verification, and the simulation results of the present model were compared and analyzed with that of existing hillslope infiltration-runoff models. The results show that compared with existing models, the model proposed in this study can well simulate the runoff and infiltration amount, and the measured values are in good agreement with the simulated ones. However, during storm periods, the simulated infiltration rates are far less than the measured ones. A possible reason is that fragments in soils may cause the formation of fast flow paths in the earth-rock interface，which is neglected in the present model. This model needs to be further refined and improved to consider the priority flow paths inside the soil layers in the hillslope.

Influence of Geometric and Setup Parameters of the Arrangement of Working Tools on Agrotechnical and Power Characteristics

The paper contains the analysis results of the influence of geometric and setup parameters of the plow working tools on agrotechnical indicators and traction resistance of a plow. ( Research purpose ) To determine the agrotechnical indicators of tillage quality depending on the type of a plow moldboard and determine the optimal moldboard for loamy soils. ( Materials and methods ) Agrotechnical indicators included crumbling, soil layer turnover, and the incorporation (embedding) degree of plant residues. More intensive lumpiness is observed as the content of clay particles increases. The angle of plow body setup relative to the furrow walls is changed using the middle bolts securing the plow body rack of the frame and installing additional washers on one of the two remaining bolted joints. For experiments on the influence of the inclination angle of the plow-bottom surface relative to the furrow wall, the plow bodies were located at angles of 30 to 55 degrees. ( Results and discussion ) It has been established that at angles of 30-35 degrees, the diameter of clods increases to values exceeding the permissible norm by 10-20 percent. An increase in the angle of more than 45 degrees reduced the diameter of clods to 10-30 millimeters. With an increase in angle to 50-55 degrees, shearing chips changed into shifting chips. The authors determined traction resistance of plows with various types of moldboards and identified the results of analytical calculations and experimental data in field trials using a dynamometer. Traction resistance of the plow decreases as cylinder moldboards are substituted with screw (auger-type) ones. ( Conclusions ) It has been determined that as the angle of plow body setup relative to the furrow walls increases, the size of soil fragments decrease, and shearing chips change into shifting chips. It has been proved that general-purpose and half-screw moldboards demonstrate the best agrotechnical indicators on loamy soils

Response of Preferential Soil Flow to Different Infiltration Rates and Vegetation Types in the Karst Region of Southwest China

The widespread preferential flow phenomenon has an important impact on the water resource allocation of vegetation restoration in karst regions. In this study, four kinds of water infiltration experiments were conducted on six kinds of vegetation types (Pinus yunnanensis Franch. var. tenuifolia plantation forestlands, Eucalyptus robusta Smith plantation forestlands, Platycladus orientalis (L.) Francoptmxjjkmsc plantation forestlands, secondary forestlands, scrublands, and natural grasslands) separately to evaluate the effect of vegetation restoration on preferential flow in karst regions. The distribution of soil water infiltration was visualized via Brilliant Blue staining (290 images of soil vertical section staining) and data were processed via structural equation model (SEM). Results showed that 15–35 mm water accumulation was beneficial to the visualization of preferential flow. The experimental statement of a higher matrix flow in grassland than in plantations made it possible to draw conclusions of economic importance. Therefore, undergrowth of vegetation coverage in plantation forestlands should be increased. Experimentally analyzing the water-vegetation-soil interaction, shows an increase in vegetation coverage inhibits the development of matrix flow, an increase in soil erodibility may inhibit the development of preferential flow, and an increase in soil clay content may promote the deepening of matrix flow depth. The artificial forest can improve the soil structure and can effectively restore the degree of soil fragmentation; vegetation can be restored reasonably to prevent desertification in karst regions. Therefore, identifying and analyzing the structure characteristics of the soil macropore network under the conditions of natural vegetation communities and artificial vegetation communities in karst-geologic settings is an urgent study, which can provide a reference for improving the restoration measures of artificial forests and sustainable forestry development in karst desertification areas.

A vertical profile imaging method for quantifying rock fragments in gravelly soil

Rock fragments (RFs) play an important role in soils that can influence land use and management decisions. Rock fragment concentrations most often are visually estimated (VE) in the field, for which accuracy strongly depends on experience and practice of soil classifiers. The direct measurement (DM) method is more accurate, but is costly and labor-intensive. Due to its importance, a simple and inexpensive method for estimating RF concentrations without destructive soil sampling is necessary. The development of camera technology and digital image processing provide an opportunity for soil descriptions and quantitative analyses using an alternative soil profile imaging (PI) method. Therefore, the objective of this study was to explore the potential for RF concentration estimation using a PI method as compared to the VE and DM methods. Apart from VE and DM, different image processing procedures inside the PI method were compared in a natural, gravelly, alluvial profile (Entisol) with low contrast among RFs in order to develop an alternative and efficient RF quantification method. Results showed that the hue-saturation-value (HSV) color model performed better than the red-greenblue color model for identifying RFs. The proposed profile imaging method accurately segmented 84.9% of the RFs from the soil matrix. The PI had a greater correlation with DM (r = 0.81) compared to the VE method (r = 0.78). Results showed that the alternative PI method could be used to accurately and efficiently estimate RF concentrations in a natural, gravelly soil profile with low contrast among RFs.

In situ degradation of biodegradable plastic mulch films in compost and agricultural soils

The global use of agricultural plastic films, which provide multiple benefits for food production, is expected to grow by 59% from 2018 to 2026. Disposal options for agricultural plastics are limited and a major global concern, as plastic fragments from all sources ultimately accumulate in the sea. Biodegradable plastic mulches could potentially alleviate the disposal problem, but little is known about how well they degrade under different environmental conditions. We quantified the degradation of biodegradable plastic mulches in compost and in soil at warm and cool climates (Tennessee and Washington). Mulch degradation was assessed by Fourier-transformed infrared (FTIR) spectroscopy, molecular weight analysis, thermogravimetric analysis (TGA), nuclear-magnetic resonance (NMR), and mulch surface-area quantification. Biodegradable plastic mulches degraded faster in compost than in soil: degradation, as assessed by surface-area reduction, in compost ranged from 85 to 99% after 18 weeks, and in soil from 61 to 83% in Knoxville and 26 to 63% in Mount Vernon after 36 months. FTIR analyses indicate that hydrolytic degradation of ester bonds occurred, and a significant reduction of molecular weight was observed. TGA and NMR confirmed degradation of biodegradable polymers. Our results indicate that biodegradable plastic mulches degrade in soil, but at different rates in different climates and that degradation occurs over several years. Faster degradation occurred in compost, making composting a viable disposal method, especially in cool climates, where mulch fragments in soil may persist for many years.

Spatial Variability of Preferential Flow and Infiltration Redistribution along a Rocky-Mountain Hillslope, Northern China

Rock fragments in soil strongly increase the complexity of hydrological processes. Spatial variability of preferential flow and infiltration characteristics, especially along a rocky-mountain hillslope are poorly understood. In this study, five rainfall–dye tracer experiments were performed in the rocky Taihang Mountains, northern China, to investigate the spatial variability of preferential flow and infiltration redistribution on different hillslope positions. Tracers were used to distinguish macropore flow and actual water flow patterns, and preferential flow indices and spatial non–uniformity of the infiltration redistribution were calculated using image analysis. Results showed increasing trends in the dye coverage, maximum infiltration depth, and steady infiltration rate with increased hillslope position, with a preferential flow fraction of 0.10, 0.11, 0.15, 0.29, and 0.26 for the bottom–, down–, mid–, upper–, and top–slope positions, respectively. With increased hillslope position, the spatial non–uniformity of the infiltration redistribution gradually increased in orthogonal and parallel directions to the stained section, and was supported by the fractal dimensions. Positive (gravel mass ratio, saturated water content, altitude, hydraulic conductivity and roots) and negative (bulk density and clay content) impacts on preferential flow and infiltration redistribution were quantitatively emphasized. The characteristic and mechanism of infiltration process were further identified along a rocky-mountain hillslope.

Spectral characteristics of some agricultural crops in different phenological phases of vegetation

For deciphering crops from satellite images at different time periods, it is necessary to have information about the spectral reflectivity of plants during their passage through the phenological phases of vegetation. An attempt was made to evaluate the spectral reflectivity of the main fruit crops and grapes in different phenological phases of the growing season using Sentinel-2 satellite images and the ENVI software package. Field research methods, plots were selected on which peach, grapes, cherries, apple trees, plums, and apricots grow are used. It was established that planting crops was carried out by mixing cultivars in order to reduce the risk of additional costs as a result of possible adverse natural processes and phenomena. For each section, the maximum, minimum, and average values of the spectral brightness coefficient were obtained and analyzed within 13 bands of Sentinel-2 satellite images. Space images were selected for 04/07/2019, 04/27/2019 and 05/12/2019, as the most suitable for the periods of the beginning of flowering (04/07/2019), the end of flowering (04/27/2019) and the beginning of fruit ripening (12/05/2019), with minimal cloud overlap values. To eliminate the external influence of the soil within each pixel of the image, the linear spectral separation module of the ENVI software package was used, a reference soil fragment was selected and its spectral characteristics were obtained, which made it possible to depict graphs of the spectral curves of the crops under study within each section. It was not possible to obtain a distinction of the spectral brightness coefficient for all sections, which is associated with the presence of additional external elements.

Assessing environmental impacts of urban growth using remote sensing

ABSTRACTThis paper provides a study of the changes in land use in urban environments in two cities, Wuhan, China and western Sydney in Australia. Since mixed pixels are a characteristic of medium resolution images such as Landsat, when used for the classification of urban areas, due to changes in urban ground cover within a pixel, Multiple Endmember Spectral Mixture Analysis (MESMA) together with Super-Resolution Mapping (SRM) are employed to derive class fractions to generate classification maps at a higher spatial resolution using an Artificial Neural Network (ANN) predicted Wavelet method. Landsat images over the two cities for a 30-year period, are classified in terms of vegetation, buildings, soil and water. The classifications are then processed using Indifrag software to assess the levels of fragmentation caused by changes in the areas of buildings, vegetation, water and soil over the 30 years. The extents of fragmentation of vegetation, buildings, water and soil for the two cities are compared, while the percentages of vegetation are compared with recommended percentages of green space for urban areas for the benefit of health and well-being of inhabitants. Changes in Ecosystem Service Values (ESVs) resulting from the urbanization have been assessed for Wuhan and Sydney. The UN Sustainable Development Goals (SDG) for urban areas are being assessed by researchers to better understand how to achieve the sustainability of cities.

Design and test of automatic detection platform for soil fragmentation rate in rotary tillage

As an important index of soil crushing performance of rotary tiller, the soil fragmentation rate is still limited to manual measurement. In this study, an automatic detection platform for soil fragmentation rate was designed, which integrated soil intake, screening, weighing and calculation of soil fragmentation rate. This platform can solve the problem that the index of the soil fragmentation rate cannot be detected quickly and effectively after rotary tillage, which leads to difficulty in field quality evaluation. The platform was mainly composed of a shovel soil module, conveying module, screening module, weighing module and automatic control system, which could realize single-line and multi-point automatic soil fragmentation rate detection. Based on the homogeneous dry slope model, the tilting angles of soil intake and soil feeding after rotary tillage on the platform were determined to be 30.10° and 26.67°, respectively. According to the principle of flow conservation, a rotary circulation screening module was designed to obtain soil particle size grading. A method based on the principle of multi-line and multi-point measurement was developed to detect soil fragmentation rate. The influence of screening speed on screening effect was analyzed, and the reasonable value of screening speed was determined to be 0.5 m/s. A field performance test was carried out in October 2019 to verify the detection performance of the platform. The results showed that, compared with the manual test method, the maximum test error was no more than 11%, the minimum test error was less than 4%, the maximum single test time was no more than 2 min, and the total test time of each test area was no more than 30 min. The efficiency of single-point detection was significantly better than the manual detection, which indicated that the design in this study met the requirements of rapid detection of soil fragmentation rate, and provided a new idea for the automatic detection of quality of rotary tillage. Keywords: rotary tillage, soil fragmentation rate, automatic detection, design, test DOI: 10.25165/j.ijabe.20201305.5678 Citation: Du X W, Yang X L, Pang J, Ji J T. Design and test of automatic detection platform for soil fragmentation rate in rotary tillage. Int J Agric & Biol Eng, 2020; 13(5): 40–49.

Soil fragmentation and aggregate stability as affected by conventional tillage implements and relations with fractal dimensions

Due to a lack of accurate information regarding soil aggregate size distribution and stability, farmers in Sindh, Pakistan often apply excessive tillage, creating an overly fine seedbed that can lead to the depletion of soil organic matter (SOM) and make the soil more vulnerable to wind and water erosion. The current paper investigates the effects of conventional tillage implements on soil fragmentation and aggregate stability, along with how these factors relate to fractal dimensions. The study aims to: (i) achieve a better understanding of soil structure and establish which tillage implement provides the best soil structure and (ii) determine the function that best describes the proportion of small aggregates in the soil. Six tillage treatments were studied, including: moldboard plough + disk harrow two passes (MPDH2), disk plough + cultivator two passes (DPC2), cultivator two passes (C2), cultivator four passes (C4), cultivator six passes (C6), and minimum tillage (disk harrow one pass) (MT) for a clay loam soil. At each of two depths (0-0.15 m and 0.16-0.30 m), four soil samples from randomly selected locations in each plot were collected (3 blocks × 6 tillage × 2 depths × 4 samples, n = 144) with the help of a soil auger. Aggregate size distribution was measured by a dry sieving method, and aggregate stability was determined by a wet sieving method. The correlations between mean weight diameter (MWD), mass fractal dimension (Dm), and soil aggregation were investigated. The greatest proportions of small aggregates and the lowest proportions of intermediate aggregates were found under DPC2 followed by C6, while a greater proportion of intermediate aggregates and a lower proportion of small aggregates was observed under MT. However large aggregates (>25 mm) were negligible across all treatments. The highest values of Dm were found after DPC2, while the highest values of MWD were found after MT. The highest proportion of water stable aggregates (WSA) was found under DPC2, while the lowest proportion was found under MPDH2 followed by MT. Similarly, aggregate stability was greatest under DPC2. Across all tillage implements, the highest fuel consumption was recorded under C6 followed by MPDH2, while the lowest occurred under MT. The Dm showed a negative correlation with intermediate aggregates (5.0–25.0 mm) and a positive correlation with small aggregates (<5.0 mm), while MWD had a positive correlation with intermediate aggregates (5.0–25.0 mm) and a negative correlation with small aggregates (<5.0 mm). Similarly, Dm was negatively correlated with MWD. This suggests that farmers should adopt the technique of using a disk plough followed by two passes of the cultivator to achieve the best possible seedbed conditions in a clay loam soil. Higher values of Dm and lower values of MWD may be used to quantify fine seedbeds, with the converse being preferable for quantifying coarse seedbeds.

Strategies to optimize modeling habitat suitability of Bertholletia excelsa in the Pan-Amazonia.

AimAmazon‐nut (Bertholletia excelsa) is a hyperdominant and protected tree species, playing a keystone role in nutrient cycling and ecosystem service provision in Amazonia. Our main goal was to develop a robust habitat suitability model of Amazon‐nut and to identify the most important predictor variables to support conservation and tree planting decisions.LocalizationAmazon region, South America.MethodsWe collected 3,325 unique Amazon‐nut records and assembled >100 spatial predictor variables organized across climatic, edaphic, and geophysical categories. We compared suitability models using variables (a) selected through statistical techniques; (b) recommended by experts; and (c) integrating both approaches (a and b). We applied different spatial filtering scenarios to reduce overfitting. We additionally fine‐tuned MAXENT settings to our data. The best model was selected through quantitative and qualitative assessments.ResultsPrincipal component analysis based on expert recommendations was the most appropriate method for predictor selection. Elevation, coarse soil fragments, clay, slope, and annual potential evapotranspiration were the most important predictors. Their relative contribution to the best model amounted to 75%. Filtering of the presences within a radius of 10 km displayed lowest overfitting, a satisfactory omission rate and the most symmetric distribution curve. Our findings suggest that under current environmental conditions, suitable habitat for Amazon‐nut is found across 2.3 million km2, that is, 32% of the Amazon Biome.Main conclusionThe combination of statistical techniques with expert knowledge improved the quality of our suitability model. Topographic and soil variables were the most important predictors. The combination of predictor variable selection, fine‐tuning of model parameters and spatial filtering was critical for the construction of a reliable habitat suitability model.

Investigation Tine Type Effect on Soil Fragmentation for Conservation Tillage

One of the main aims of tillage operation is to provide a seedbed with appropriate soil fragmentation and to create relatively large aggregates of topsoil to achieve conservation tillage. Considering that subsoiling is necessary for hardpan breakup, the creation of a seedbed with the same operation can increase the operation efficiency. The present study was conducted to investigate the effect of tine type on soil aggregate. For this purpose, we tested four subsoiling tines of conventional, Bentleg, Paraplow, and winged-Paraplow in the field at soil moisture contents of 8, 12, 16, and 20% and the tractor forward speeds of 0.5, 1, 1.2, and 1.4 m/s. Soil fragmentation was evaluated in different depths of 10, 20, 30, and 40 cm. Winged-Paraplow and Paraplow, compared with two other tools, showed more soil disturbance due to having a wing and chisel at the end of the tine. The highest mean weight diameter (MWD) =19.9 mm was reached using a Bentleg at a depth of 10 cm and moisture content of 20%. In comparison, the lowest value of 3.37 mm was related to the winged-Paraplow at a depth of 40 cm and moisture content of 8%.Considering the aggregate size of 0.5-8 mm for providing a proper seedbed, the winged-Paraplow tine is a suitable tool that can provide seedbed at any depth at a water content of 0.8PL, where PL denotes plastic limit. At slow forward speeds, fine particles had enough time to sift to a deeper layer, which is beneficial for seedbed creation. Reducing the soil moisture increased soil disturbance and its fragmentation. Moreover, it was observed that MWD was higher at high moistures..