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Approximately 20 years ago (June 11th, 2004), a highly reputable scientific journal, on a front cover much celebrated by soil scientists, printed an eye-catching phrase: "Soils: The Final Frontier". In the introduction to that special issue, it was mentioned that "in many ways the ground beneath our feet is as alien as a distant planet", to then state that, owing to the booming interest in soil research at that time, together with the development of advanced techniques (e.g., next-generation sequencing), subterraneana would be made "seem far less of an alien experience". In this perspective article, using as illustrations, by way of example only, two topics of great interest nowadays – soil carbon sequestration and soil biodiversity –, it is claimed that, despite all the efforts devoted in the last 20 years to the understanding of the soil ecosystem, the "final frontier" appears to have receded, as we are discovering increasing levels of complexity that are slowing down our trip to the far reaches of the edaphic universe. Due to, among other features, its high structural and functional complexity, biodiversity, heterogeneity, opacity, and processual and dynamic nature, the soil still remains a great unknown ("a black box"). The ultimate goal of this perspective article is to draw attention to the need for further long-term investment in research into this highly complex and fascinating ecosystem. [ABSTRACT FROM AUTHOR]

Karst landforms are widely distributed around the world, and karst rocky desertification has occurred on a large scale in many countries and regions, causing significant adverse impacts on local natural environments and societies. The improvement and rational use of karst soil is a key aspect of rocky desertification governance. Karst soil science studies are of great value in karst regions and are essential for controlling karst rocky desertification and ecological restoration. In order to understand the research hotspots and the development directions in the field of vulnerable karst soil environment, we undertook bibliometrics citation analysis on 1913 contributions to the literature written in the range from 2001 to 2019 based on the "Web of Science" core collection citation index database. Hopefully, this work will help to set up a scientific foundation for further studies. Using CiteSpace visualization software, we analyzed the distribution of disciplinary categories, reference co-citation clusters, and keyword clusters in the literature. The results show the basic characteristics and evolution of the literature related to karst pedology. We then recognized the main intellectual bases in the domain of karst soil science. This study also revealed the research hotspots and trends in this field. Through a bibliometrics citation analysis of research on karst vulnerable soil environment, the present study provides a quantitative and objective understanding of development directions that have emerged in this field over the past 19 years, offering a reference for future research. [ABSTRACT FROM AUTHOR]

Current environmental regulations for agriculture in the Netherlands and England focus on the application of certain selected management measures as an empirical basis for providing subsidies. Farmers like this simple, straightforward approach. The link with sustainable development is, however, not defined and this can become problematic when procedures may be challenged in future. A procedure focusing on the measurement of ecosystem services in line with selected UN Sustainable Development Goals (SDGs) can provide this link, but whether or not this more complicated procedure will be attractive for farmers is still unclear. The soil science community would be well advised to discuss their future role in developing scientifically sound operational procedures that would be acceptable to both farmers and policy makers and would be aimed at contributing to the sustainable development of society at large. [ABSTRACT FROM AUTHOR]

Dripping rainfall simulators (DRS) for soil research generate water drops with different types of drippers, but metal tubes are most commonly used, often in the form of hypodermic needles. However, scientific papers using dripping rainfall simulators are often incomplete in terms of data on hypodermic needle characteristics, as well as data on drops produced by hypodermic needles under different water pressures. This study determines which drop sizes and dripping speeds are generated by various hypodermic needles at different water pressures. For the purpose of this study, a dripping rainfall simulator was designed and constructed for laboratory use. Water drops were generated with 11 different needles, ranging in size from 16 G to 32 G (tube gauge number), at different water pressures. Measured water drop sizes ranged from 1.42 to 3.69 mm at a dripping speed between 10 and 360 drops per minute and water head from 14 to over 1970 mm. Measured drop sizes, supplemented with data from previous studies, provided information on the relation between drop sizes and the size of the hypodermic needles. Van Boxel's numerical model provided estimations of the fall velocity for different drop diameters and their kinetic energy for falling heights up to 11.5 m. The results of this research can be used to design dripping rainfall simulators for soil research. [ABSTRACT FROM AUTHOR]

Approximately 20 years ago (June 11th, 2004), a highly reputable scientific journal, on a front cover much celebrated by soil scientists, printed an eye-catching phrase: “Soils: The Final Frontier”. In the introduction to that special issue, it was mentioned that “in many ways the ground beneath our feet is as alien as a distant planet”, to then state that, owing to the booming interest in soil research at that time, together with the development of advanced techniques (e.g., next-generation sequencing), subterraneana would be made “seem far less of an alien experience”. In this perspective article, using as illustrations, by way of example only, two topics of great interest nowadays – soil carbon sequestration and soil biodiversity –, it is claimed that, despite all the efforts devoted in the last 20 years to the understanding of the soil ecosystem, the “final frontier” appears to have receded, as we are discovering increasing levels of complexity that are slowing down our trip to the far reaches of the edaphic universe. Due to, among other features, its high structural and functional complexity, biodiversity, heterogeneity, opacity, and processual and dynamic nature, the soil still remains a great unknown (“a black box”). The ultimate goal of this perspective article is to draw attention to the need for further long-term investment in research into this highly complex and fascinating ecosystem.

Purpose: Brazilian territory is divided into six biomes (Amazon, Atlantic Forest, Cerrado, Caatinga, Pantanal, and Pampa) that represent important global biodiversity hotspots. Research into soil science in these environments has increased in recent years, but a quantitative and qualitative mapping of research into the soils of Brazilian biomes has never been carried out. In this study, research on soil science in the Brazilian biomes were analyzed to map the evolution, scientific collaboration, current status, research trends and impact over the last 50 years (1972–2022). Methods: The database was obtained from the Core Collection of Web of Science. The data was quantitatively analyzed through descriptive statistics and linear regression using Microsoft Excel, and qualitatively using the bibliometric software VOSviewer. Results: A total of 11,231 papers were obtained. The results indicated a significant increase in soil science research across all biomes (polynomial growth), with greater emphasis for research in the Cerrado (R2 = 0.9361), Amazon (R2 = 0.9170) and Atlantic Forest (R2 = 0.9104) biomes. Soil science research in the Amazon accounted for 47.0% of the research conducted in all Brazilian biomes. While in the Amazon (38.8%), Atlantic Forest (34.8%), and Pantanal (36.7%), most of the research was related to environmental sciences and ecology, in the Cerrado (47.4%), Caatinga (58.2%), and Pampa biome (48.9%), research in the field of agriculture was more significant. For all biomes, except for the Caatinga (a dry climate biome), a significant participation of international researchers and institutions was evident in the overall publications. This demonstrates a lower global interest in soil science research in the Brazilian dry ecosystem. Conclusion: Soil science research in the Brazilian biomes is disproportionate, with greater interest in the soils of the larger forest biomes and less interest in the dry and flooded areas. The results of this study can be useful for the development of public policies, research and scientific collaboration aimed at soil conservation in Brazilian terrestrial biomes. [ABSTRACT FROM AUTHOR]

Karst landforms are widely distributed around the world, and karst rocky desertification has occurred on a large scale in many countries and regions, causing significant adverse impacts on local natural environments and societies. The improvement and rational use of karst soil is a key aspect of rocky desertification governance. Karst soil science studies are of great value in karst regions and are essential for controlling karst rocky desertification and ecological restoration. In order to understand the research hotspots and the development directions in the field of vulnerable karst soil environment, we undertook bibliometrics citation analysis on 1913 contributions to the literature written in the range from 2001 to 2019 based on the “Web of Science” core collection citation index database. Hopefully, this work will help to set up a scientific foundation for further studies. Using CiteSpace visualization software, we analyzed the distribution of disciplinary categories, reference co-citation clusters, and keyword clusters in the literature. The results show the basic characteristics and evolution of the literature related to karst pedology. We then recognized the main intellectual bases in the domain of karst soil science. This study also revealed the research hotspots and trends in this field. Through a bibliometrics citation analysis of research on karst vulnerable soil environment, the present study provides a quantitative and objective understanding of development directions that have emerged in this field over the past 19 years, offering a reference for future research.

When deriving drained strength parameters for sandy soils, geotechnical engineers need to be cautious while applying the semi-empirical correlations that are mainly developed from the highly idealised uniform clean silica sands as often used in academia. Many studies have shown that changing fines content changes the f mechanical behaviour of sand, and that grading curve and particle angularity affect the strength-dilatancy characteristics. However, when various parameters of sands encountered in nature differ from the commercially sourced silica sands, the counteracting effects are difficult to quantify. In this study, a database of classification tests and Consolidated Isotropic Drained axisymmetric strength tests as well as some accompanying cone penetration tests (CPTs) are collected for siliceous sands from the North Sea. From this extensive database of natural sands, simple expressions are developed to help predicting drained strength parameters with improved reliability. Furthermore, a correction factor, for a commonly applied CPT friction angle [q.sub.c] - [[phi]'.sub.p,tx] correlation accounting for the grading curve, is developed. These expressions can help in reducing the number of costly advanced strength tests and to gain more information from a soil investigation. Key words: sands, site investigation, offshore, CPT, triaxial test, grading curve, 1. Introduction For various geotechnical applications, soils tend to be treated as either clay or 'clean' sand. However, the semi-empirical correlations developed to derive sand strength parameters are mostly developed [...]

Dripping rainfall simulators (DRS) for soil research generate water drops with different types of drippers, but metal tubes are most commonly used, often in the form of hypodermic needles. However, scientific papers using dripping rainfall simulators are often incomplete in terms of data on hypodermic needle characteristics, as well as data on drops produced by hypodermic needles under different water pressures. This study determines which drop sizes and dripping speeds are generated by various hypodermic needles at different water pressures. For the purpose of this study, a dripping rainfall simulator was designed and constructed for laboratory use. Water drops were generated with 11 different needles, ranging in size from 16 G to 32 G (tube gauge number), at different water pressures. Measured water drop sizes ranged from 1.42 to 3.69 mm at a dripping speed between 10 and 360 drops per minute and water head from 14 to over 1970 mm. Measured drop sizes, supplemented with data from previous studies, provided information on the relation between drop sizes and the size of the hypodermic needles. Van Boxel’s numerical model provided estimations of the fall velocity for different drop diameters and their kinetic energy for falling heights up to 11.5 m. The results of this research can be used to design dripping rainfall simulators for soil research.

Free fall penetrometers (FFP) can improve the efficiency of deepwater geotechnical site investigations. This study investigates the derivation of geotechnical properties from piezocone FFP measurements in the upper 4 m of the seabed at a clayey site with water depths of ~1500 m. Data analysis methods as commonly applied in cone penetration test (CPT) analysis were tested with strain rate normalization methods previously suggested for FFP analysis. The logarithmic, inverse hyperbolic sine, and power law approaches were applied for strain rate normalization. Strain rate effects appeared small for FFP cone resistance (with [mu] = 0.1 for the logarithmic and [beta] = 0.06 for the power law approach), but were apparent. Undrained shear strength derived from FFP data matched overall the CPT results, using an N factor [N.sub.kt] = 12. Undrained shear strength derived from excess pore pressure measured at the [u.sub.1] position also yielded favorable results using [N.sub.[DELTA]u_FFP] = 6. Two soil behavior type classifications showed acceptable agreement between strain rate normalized FFP and CPT results. Key words: free fall penetrometer, cone penetration test, deepwater, undrained shear strength, soil behavior type, strain rate Les penetrometres a chute libre (FFP) peuvent ameliorer l'efficacite des investigations geotechniques en eaux profondes. Cette etude examine la derivation des proprietes geotechniques a partir des mesures de la FFP du piezocone dans les 4 m superieurs du fond marin sur un site argileux avec des profondeurs d'eau de ~1500 m. Les methodes d'analyse des donnees telles qu'elles sont couramment appliquees dans l'analyse du test de penetration du cone (CPT) ont ete testees avec des methodes de normalisation de la vitesse de deformation suggerees precedemment pour l'analyse FFP. Les approches logarithmiques, sinus hyperboliques inverses et lois de puissance ont ete appliques pour la normalisation de la vitesse de deformation. Les effets de la vitesse de deformation semblent faibles pour la resistance du cone FFP (avec [mu] = 0.1 pour l'approche logarithmique et [beta] = 0.06 pour l'approche de la loi de puissance), mais etaient apparents. La resistance au cisaillement non drainee derivee des donnees FFP correspondait globalement aux resultats du CPT, en utilisant un facteur N, [N.sub.kt] = 12. La resistance au cisaillement non drainee derivee de l'exces de pression interstitielle mesure a l'endroit ou se trouve l'echantillon [u.sub.1] a egalement donne des resultats favorables en utilisant [N.sub.[DELTA]u_FFP] = 6. Deux classifications du type de comportement du sol (SBT) ont montre une concordance acceptable entre les resultats de la FFP et du CPT normalises par la vitesse de deformation. [Traduit par la Redaction] Mots-cles : penetrometre a chute libre, essai de penetration au cone, eau profonde, resistance au cisaillement non draine, type de comportement du sol, taux de deformation, 1. Introduction Marine site investigations are an important part of offshore engineering and construction activities (ISO 2014). Randolph et al. (2018) suggested the free fall penetrometer (FFP) as a cost-effective [...]

Mesofauna represents a major component of soil biological community and play a critical role in maintaining soil quality, as well as a range of ecosystem functions. A split-split plot design was performed with the aim of identifying the main predictors (phytogeographical criteria, cover type and environmental variables) of edaphic community structure under the effect of desertification. The study also aimed to examine the spatial and seasonal distribution of mesofauna community according to phytogeographical criteria (shrubland vs grassland) and cover type (bare vs covered soil) in the north-western Patagonian steppe of Argentina. The relationship between edaphic fauna, environmental variables and site location was investigated using redundancy analysis (RDA), while the main predictors of edaphic community were analysed using generalised linear mixed models (GLMMs). A total of 43 taxa of Oribatida were found in 168 samples. GLMM approaches selected cover type due to its higher effect on mesofauna community. In this sense, cover type was more important than phytogeographical criteria and environmental variables as predictor of mesofauna community. These findings contribute to a better understanding of how the distribution of mesofauna community respond in Patagonia steppe. Keywords: acari, covered soil, degradation, grassland, microarthropods, Oribatida, predictors, shrubland., Introduction Mesofauna community plays a critical role in maintaining soil quality, as well as a range of ecosystem functions (Barrios 2007). Soil invertebrates are responsible for numerous functions such as [...]

Context. Labile soil carbon and nitrogen are important indicators for evaluating carbon sequestration and nutrient availability under forest management such as thinning. Aims. This study assessed the effects of thinning on labile soil carbon and nitrogen indices in a naturally regenerated oak forest. Methods. Un-thinned control, 15% thinning, and 30% thinning were set up, and labile soil carbon and nitrogen (microbial biomass, permanganate oxidisable carbon, dissolved carbon and nitrogen, and inorganic nitrogen) and C:N balance indices (C:N ratio and threshold element ratio) were measured after 6 years. Key results. Thinning generally increased labile soil carbon and nitrogen concentrations (P < 0.01); however, their fraction within the total soil carbon and nitrogen decreased under thinning. Redundancy analysis revealed that the remaining deadwood mass was the most influential factor affecting such differences in labile soil carbon and nitrogen indices across the three treatments (P < 0.01), although soil moisture had an effect as well (P < 0.05). Furthermore, the dissolved C:N ratio was higher than threshold element ratio only in 15% and 30% thinnings, indicating that thinning could shift the limiting factor for microbial growth from carbon to nitrogen by adding deadwoods, which provided carbon-rich substrates. Conclusions. Overall, results demonstrate that deadwood retention and soil microclimatic changes could be the significant factors affecting soil carbon and nitrogen storage and the associated microbial affinity in thinned forests. Implications. Therefore, sustainable forestry strategies for thinning residue management should be addressed to reinforce soil carbon and nitrogen conditions and the forest ecosystem functions. Keywords: carbon fraction, forest management, nitrogen availability, soil microbes, temperate oak forest, thinning intensity, thinning residue, threshold elemental ratio., Introduction In managing forests, thinning has an important impact on both wood production and environmental management. Traditionally, thinning is used to reinforce the growth and shape of crop tree stems [...]

Context. Soil-tool interaction modelling and optimisation reduce manufacturing costs and energy requirements for precision tillage equipment design. Diverse tillage tools have been designed to reduce draft requirements and desirable soil disturbance, but this is not fully understood. Aims. The current study investigated the effects of tool width, cone index, depth, and forward speed on draft with corresponding rupture width in order to develop response surface methodology (RSM) and artificial neural network (ANN) models and compared them to other models in order to predict draft and rupture width. Methods. Experiments were carried out in a soil bin with a vertisol, and rupture width was measured using an image processing technique. Key results. Using RSM, the optimum values for minimum draft with maximum rupture width within a range of independent variables were found to be l00 mm tool width, 600 kPa cone index, 141.63 mm tillage depth, and 3 km/h forward speed. For predicting the draft, the coefficients of determination ([R.sup.2]) for ANN and RSM models were 0.997 and 0.987, respectively; for rupture width prediction, [R.sup.2] were 0.921 and 0.976. Conclusions. Developed ANN and RSM models of draft and rupture width were better than other analytical or numerical models, and both models' predictions were in good agreement with experiment values within the range of [+ or -] 5% uncertainty. Implications. The developed models can be used to predict the draft and soil disturbance requirements of tillage tools and design precision tillage tools. Keywords: artificial neural network, cone index, draft, image processing, modelling, response surface methodology, rupture width, vertisols., Introduction Tillage operations are an unavoidable step in agricultural production systems, and consume energy and time. For a proper tillage operation, extensive knowledge of soil characteristics before, during, and after [...]

Context. High inputs of plant litters and slow decomposition of soil organic carbon (SOC) influence the biogeochemical cycling of soil carbon in flooded wetlands. Aims. To investigate the effects of different quality litter inputs on SOC stability and storage in flooded wetlands. Methods. A 180-day microcosmic experiment to investigated the decomposition of litters of two dominant plants (Carex cinerascens Kukenth., CC; Cyperaceae family) and Triarrhena lutarioriparia L. Liu, TL; Poaceae family), in Poyang Lake Wetlands. Key results. CC litters (high-quality, low lignin/N mass ratio) reduced gross content of SOC, but increased labile carbon and labile index (LI) of soils. In contrast, inputs of TL litters (low-quality, high lignin/N mass ratio) increased SOC gross content and recalcitrant carbon fractions of soils, but reduced soil labile carbons and LI. Significant effects of litters on SOC were not observed until ~30 days indicating that the effects of litter inputs on soil carbon pools in flooded wetlands need time to be activated. CC and TL litters both increased the soil microbial biomass carbon (MBC) content. Soil MBC in CC treatments was significantly affected by the litter ash-free dry mass, while that in TL treatments was significantly affected by mass loss. Conclusions. Litter quality may regulate the growth of soil MBC via different microbial growth strategies. Implications. Our results suggest that inputs of high-quality litters can yield a high amount of labile carbon through stimulated microbial decomposition, leading to an overall loss of carbon. In contrast, inputs of low-quality litters can promote the microbial production of more recalcitrant carbons and increase soil carbon stability and carbon sequestration. Keywords: Carex cinerascens Kukenth, flooded wetlands, litter quality, microbial biomass carbon, soil carbon stability, soil labile carbon, soil organic carbon, Triarrhena lutarioriparia L. Liu., Introduction Wetlands store about 20%-30% of the terrestrial soil organic carbon (SOC), even though they cover only 6% of the land surface (Gumbricht et al. 2017). Plant litter and its [...]

Context. Organic fertilisation may increase soil phosphorus (P) availability and increase risk of P loss to groundwater. Aims. To understand the effect of continuously applying organic fertilisers on formation of P fractions. Methods. A field experiment was conducted to investigate the effect of different fertilisation (CF, chemical fertiliser; COF, cow dung compost with chemical fertiliser; POF, pig manure compost with chemical fertiliser) on different soil P fractions for five growing seasons. Key results. Compared with CF, the COF and POF treatments had significantly higher total P and available P contents in each season. The COF treatment showed the highest concentration of NaOH-[P.sub.i]; however, POF showed the highest concentration of HCl-[P.sub.i] in all seasons. There were significant positive correlations between concentrations of total P (r = 0.863, P = 0.001), available P (r = 0.590, P = 0.006), each P fraction (r = 0.447 to 0.862, P = 0.048 to 0.001) and organic carbon concentration. Concentrations of total P (r = -0.473, P = 0.035), available P (r = -0.589, P = 0.006) and each P fraction (except HCl-[P.sub.i]) (r = -0.71 1 to -0.476, P = 0.001 to 0.034) showed significant negative correlations with soil pH. Available P concentration showed the highest correlation with concentrations of residual P (r = 0.665, P = 0.007), HCl-[P.sub.i] (r = 0.413, P = 0.126) and NaOH-[P.sub.i] (r = 0.282, P = 0.309) in CF, COF and POF treatments, respectively. Conclusions. Continuous application of organic fertiliser can significantly improve P availability through impacting distribution of P fractions. Implications. Further studies are needed to establish the release risk of each P fraction in soils. Keywords: correlation, field experiment, five growing seasons, organic fertiliser, P availability, P transformation, soil P fraction, soil pH and organic C., Introduction Phosphorus (P) is a key macronutrient for the growth of plants. An increasing amount of P fertilisers is being applied to soil to help provide enough food for the [...]

Context. Understanding the dynamics of soil organic matter (SOM) requires that it be divided into fractions with contrasting behaviour. Aim. Using soils from a field trial with a diverse set of treatments (pasture to arable conversion, ex-pasture soil maintained fallow for 13 years and arable cropping with contrasting tillage treatments), we evaluated two approaches to characterise SOM: particle-size fractionation and hot water extraction. Methods. Soils were separated into four size fractions, including the >50 [micro]m fraction (particulate organic matter, considered the most labile fraction) and the 50%) of the C lost under cropping and bare fallow was derived from the clay fraction, which was also the source of 59-77% of HWC. Conclusions and Implications. Our results indicate that hot water is specific for the labile component of SOM while SOM in size fractions is a composite of labile and stable components, the proportions of which may vary depending on land use and other factors. Ideally, data on quantity of SOM in size fractions should be complemented by information on its lability. Keywords: hot water extraction, labile C, land use effects, long-term fallow, particle size fractionation, pasture, soil organic matter, tillage., Introduction Soil organic matter (SOM) is vital to the health and functioning of soils. It also plays a central role in the global cycles of C and nutrients, including nitrogen [...]

Context. Many regions in the world have undergone rapid land use change and intensification of agricultural land, such as through irrigation expansion, upgrading irrigation systems, and changing grassland, stock, and nutrient management practices. With more intensive land use, changes to soil properties can occur, such as soil compaction and changes in soil water storage. The effects of modern sprinkler-irrigated pastoral farming on soil physical properties are not well quantified internationally, particularly for temperate climates. Aims. This regional study evaluates the effect of irrigation on soil physical properties in topsoil and subsoil, under modern pastoral grazing and sprinkler irrigation, across Canterbury, New Zealand. Methods. Paired sites were sampled, consisting of a spray-irrigated paddock (field) and an adjoined part of the same paddock that was dryland (unirrigated), with other management the same for each pair. Key results. Under irrigation there was a shift towards a greater abundance of smaller pores. This was reflected in macroporosity and readily available water capacity being significantly lower under irrigation, while semi-available water capacity and unavailable water held below permanent wilting point both increased. Conclusions. These differences reflect increased compaction under irrigated grazed pasture, particularly under dairy grazing, consistent with findings in similar studies. This study quantified changes in both the topsoil and subsoil but showed that most differences were confined to the topsoil (30 cm depth). Implications. For irrigation management, our study indicates the lower readily available water capacity on irrigated pasture is significant, with farmers potentially having to irrigate more frequently. Adopting deficit irrigation could minimise impacts of compaction. Keywords: available water capacity, compaction, crop lower limit, land use change, macroporosity, readily available water capacity, soil health, soil quality., Introduction Global population growth is increasing the demand for food and agricultural products. Land use change is occurring to support this demand on agricultural food production, with expansion and intensification [...]

Context. The rhizosphere is an environment created by interactions between root exudates and microorganisms. Interactions are beneficial due to certain components having a plant growth promoting rhizobacteria (PGPR) effect. Aims. This study consists of the isolation, screening of PGPR from the rhizosphere of Olea europaea L. of a Mediterranean climatic region in Algeria and the study of their effects on growth of two agronomic vegetables Phaseolus vulgaris L. and Cucurbita pepo L. Methods. Based on their ability to produce the PGPR molecules indole-3acetic acid (IAA), phosphatase and siderophores, three rhizobacteria (S25, S75, and S79) were chosen for in vivo tests and capacity to produce the cell wall degrading enzymes chitinase, lipase, protease, glucanase, cellulase, and and phospholipase. They were also examined using scanning electron microscopy (SEM) and analysed using matrix-assisted laser desorption/ionisation time of flight mass spectrometry (MALDI-TOF MS) for identification. Key results. Bacterial strains identified as Bacillus cereus and Bacillus thuringiensis were able to enhance significantly germination of the two vegetables at P < 0.001. Vegetative parameters of C. pepo were significantly affected by the bacterial inoculation. We noted increases in stem length (P < 0.05), number of flowers (P < 0.01), and root length (P < 0.001). Conclusion. The bacterial isolates of this study provide biological options in treatments originating from alternate hosts. Implications. They provide hope for companion/intercrop planting schemes, leading to optimisation of agricultural yields in agroecological blends. Keywords: Bacillus, cell wall degrading enzymes, indole-3-acetic acid, matrix-assisted laser desorption/ionisation time of flight mass spectrometry, phosphatase, plant growth promoting rhizobacteria, siderophores., Introduction The principle imperative facing us today is the feeding of a human population, which may reach in excess of 8.9 billion by 2050, with major global increased demand for [...]

Context. An appropriate use of the fertiliser technology may lead to a more efficient N absorption and to the reduction of economic and environmental costs. Aims. This study sought to quantify [N.sub.2]O emissions generated from soil and the residual nitrate (N[O.sub.3.sup.-]) up to 2m depth in field conditions in a maize crop under supplementary irrigation and fertilised with two nitrogen (N) sources (UAN and urea) at increasing N rates (0, 80, 160 and 250 kg N [ha.sup.-1]) in the Semi-arid Argentine Pampas. Methods. Throughout the crop cycle, emissions were monitored daily with static chambers during the first week after fertilisation; then sampling frequency was gradually reduced until the end of the experiment. Key results. There were no yield responses to the use of different sources and N rates. Crop N uptake saturated at 80 kg N [ha.sup.-1], reaching 300-310 kg N [ha.sup.-1]. Residual N[O.sub.3.sup.-] increased significantly with the highest rates of N fertiliser. Total [N.sub.2]O emissions differed significantly only among fertiliser rates. The [N.sub.2]O emissions were lower at 80 than at 160 and 250 kg N [ha.sup.-1]. Conclusions. The [N.sub.2]O emissions measured were lower than those calculated by the IPCC, even when only direct emissions were considered. No grain yield increase was observed due to N fertilisation, with a non-limiting supply of N-N[O.sub.3.sup.-] at the beginning of the crop cycle and of N from mineralisation. Implications. This excess of N can generate negative environmental effects due to higher emissions of [N.sub.2]O and residual N-N[O.sub.3.sup.-] that can be leached. Keywords: Argentinean Pampas, environmental effects, greenhouse gases, irrigation, maize yield, nitrate leaching, UAN, urea., Introduction About 80% of cereal and oilseed production in Argentina comes from the Pampean region, mostly soybean, maize and wheat crops (Klein and Vidal Luna 2021). In 2019, maize production [...]

Context. Cover crops are used to improve soil fertility and environmental sustainability. Decomposition of cover crop residues can affect belowground microbial communities and activity, which is important for soil functions (e.g. nutrient cycling, organic matter decomposition). Aims. We investiagated the effect of plant residues from a range of cover crop species on soil microbial activity, diversity and microbial community composition. Methods. A mixture of four cover crop residues (buckwheat, clover, sunflower, radish) or an equal mass of the residues of each of the individual species were assessed for their effect on soil respiration and soil microbial community structure. Key results. Cover crop residue incorporation significantly (P < 0.001) increased soil respiration during 84 days incubation and this response caused a significant change in microbial community composition by increasing the proportion of fungi and Gram-positive bacteria at the cost of decreasing Gram-negative bacteria. The mixture of cover crop residues had a significantly (P < 0.05) greater soil respiration rate, by 57.61 [micro]g C [g.sup.-1] [h.sup.-1], than the average of the four individual residues, but did not have a significantly different soil microbial biomass or microbial community structure. Conclusions. Greater diversity of organic resources increased the number biochemical niches, and activated dormant microbial communities to increase activity without affecting biomass or community composition. Greater respiration from similar microbial biomasses suggests that microbial activity might be more efficient following more diverse substrate input. Implications. The positive impact of cover crop residues on soil microbial activity suggests that mixtures of cover crop residues may enhance soil functions beyond the sum of individual cover crop residues. Keywords: agroecology, cover crops, litter, microbial biomass, mixture, residue diversity, respiration, soil function., Introduction Integrating cover crops, non-cash crops grown primarily for the purpose of protecting or improving soil health between cash-crops in an arable crop rotation, is a popular tool to increase [...]

Rainfall simulators represent often-used equipment for soil research. Depending on their performance, they could be appropriate for some soil research or not. The aim of this research is to provide insight into the capabilities of existing dripping rainfall simulators (DRS) to mimic natural rainfall and the frequency of simulated rainfalls of certain characteristics, facilitate the selection of rain simulators that would best meet the needs of soil research and to reach a step closer to the standardization of rainfall simulators. DRS performance was analyzed integrally, for simulators with more than one dripper (DRS>1) and with one dripper (DRS=1). A statistical analysis was performed for the performance of the DRS, wetted area, drop size, rainfall intensity, duration and kinetic energy. The analysis showed that DRS can provide rainfall that corresponds to natural rainfall, except in terms of the drop size distribution and wetted area. However, usually there are more factors that do not correspond to natural rainfall, such as the median drop size, volume and kinetic energy. Metal and plastic tubes (MT and PT) as the most present dripper types showed a strong relation between the outer diameter (OD) and drop size, while the inner diameter (ID) relation was moderate-to-weak. However, when increasing the range of MT drippers, for diameter size, the relation significance becomes very strong for bouts ID and OD. With the increase in the ID of PT, the relation deviates from the logarithmic curve that represents all drippers together. The sizes of the drops generated by the drippers are mostly in the range between 2 and 6 mm, while the number of drops smaller than 2 mm is relatively small. The intensity and duration of the simulated rain can be successfully produced to match natural values, with the most frequently simulated short-term rainfall of a high intensity. Most simulations were conducted at a fall height of up to 2 m, and then their number gradually decreases as the height gets closer to 5 m. Most simulations (58.6%) occur in the range between 20-90% KE, then 33.0% in a range of 90-100%, with only 8.4% lower than 20% KE. [ABSTRACT FROM AUTHOR]

The research deals with the selection of various agrotechnical measures in the studyexperimental farm of Akaki Tsereteli State University in Senaki (Nosiri), on the alluvial, low-fertility soils of the hazelnut plantation, and the influence of soil fertility on the yield. The plantation was built within the framework of the scientific grant financed by the National Science Foundation of Shota Rustaveli, on the basis of the Agrarian Faculty of Akaki Tsereteli State University. The purpose of the research is to select the best options for the existing industrial hazelnut plantation, adapted to the specific soil and climatic conditions, and the best scientifically justified options for soil conditioning. The paper presents the results of the soil research in the hazelnut plantation and the results of planning and implementation of the measures selected for increasing the soil fertility and yield of the hazelnut culture based on it. [ABSTRACT FROM AUTHOR]

Soil surface sealing and crusting are formed through the processes of raindrop impact, drying, and clogging of pores. This creates a mechanically hard top layer that shows high stiffness, mechanical strength, seismic velocity, and reduced infiltration rate. The existence of surface seals and crusts affects soil erodibility and run-off. In this study, a non-invasive seismic surface wave method was employed to evaluate surface crust and the profile below. The method was based on the multi-channel analysis of surface wave method (MASW). Unlike the conventional MASW methods used in geotechnical and civil engineering applications for exploring subsurface soil from several meters to tens of meters below the surface, the present method aimed at very thin layer (several centimeters) by increasing frequency up to kHz. A self-adaptive high-frequency MASW method with a variable sensor spacing configuration was employed for the task. After signal processing and inversion, a shear wave velocity soil profile was determined from which the top hard layer was evaluated. In this study, the MASW tests were conducted on a naturally formed sealed/crusted soil and on a non-sealed/non-crusted soil as a control test. Soil cores, shear vane and penetration tests were conducted to compare with the observations from the MASW method. The results from both the MASW method and invasive tools are in good agreement, demonstrating that the MASW method can be used to evaluate and assess soil sealing and crusting layer in situ and to explore the soil profile in the vadose zone. Key words: multichannel analysis of surface wave, Rayleigh waves, dispersion curve, shear wave velocity, surface sealing and crusting. Abbreviations: MASW, multichannel analysis of surface wave; FFT fast Fourier transform; S, shear; HVL, high velocity layer; LVL, low velocity layer., INTRODUCTION Soil sealing and crusting plays a critical role in the hydrology and productivity of agricultural and natural landscapes. In a recent review of soil sealing and crusting, Nciizah and [...]

Biochar application to a structurally poor tropical soil could potentially alter the soil's aggregate strength and hydraulic properties. However, very few field studies have investigated the impact of biochar on the aggregate strength and hydraulic properties of tropical soils. A field experiment was therefore conducted to investigate the short-term effects of rice straw biochar on soil hydraulic properties and aggregate stability of an Acrisol in Ghana. The biochar was broadcast at rates of 10 t [ha.sup.-1] and 20 t [ha.sup.-1] as single applications that were incorporated into the top 20 cm of the soil using a spade and then the soil was levelled using a rake. Field saturated hydraulic conductivity and laboratory-measured soil water retention, aggregate stability and water-repellency were determined 10 months after the biochar application. Biochar increased aggregate stability against fast wetting by up to 33% compared to the control. This implies that biochar might improve the stability of aggregate of an Acrisol against slaking and erosivity of heavy rainfall. However, aggregate stability against slow wetting and mechanical breakdown after pre-wetting were unaffected by the biochar. Biochar did not affect field saturated hydraulic conductivity, water retention characteristics and water-repellency. Further field studies on weathered tropical soils with low native soil organic matter is recommended to elucidate the effect of repeated biochar addition on soil hydraulic and aggregate characteristics. Keywords: aggregate stability, biochar, carbon sequestration, hydraulic conductivity, hydrophobicity, organic amendment, pyrolysis, soil water retention, tropical soils, water repellency., Introduction Biochar, a carbon-rich by-product from pyrolysis of biomass, has gained wide research interest due to its potential to promote agricultural productivity, carbon sequestration and soil remediation by absorbing organic [...]

Increased conventional tillage intensity causes soil degradation in agrosystems. In this field experiment, we evaluate the sensitivity of soil physical, chemical, and biological properties under varying soil tillage intensities. The treatments were: T[I.sub.0] (tillage intensity zero); T[I.sub.2] (tillage intensity two); T[I.sub.4] (tillage intensity four); T[I.sub.6] (tillage intensity six); and T[I.sub.8] (tillage intensity eight). These treatments corresponded to two tillage seasons (dry and rainy conditions) with four tillage intensities of conventional tillage (ploughing + harrowing) performed monthly. The restorative role of crop growth and rotations in soil properties was not considered in this study, and the interval between soil tillage was short. After the second tillage season, we determined 31 soil physical, chemical and biological properties. Biological properties were more affected by conventional tillage intensity than physical and chemical properties. The most sensitive soil properties to the increasing tillage intensities were aggregate weighted mean diameter (WMD), percentage of aggregates (PA), bulk density (Bd), total porosity (TP), macroporosity (Mac), microporosity (Mic), soil pH, cation exchange capacity (CEC), soil organic matter (SOM), total microbial activity (FDA), arylsulfatase (Ary), acid phosphatase (Phos), and xylanase activity (Xyl). A minimum data set including WMD, Mac, SOM, and Xyl was suggested. The highest intensity of conventional tillage reduced WMD, Xyl and Mac by 28%, 51 %, and 63%, respectively, and increased SOM by 14% relative to the control. This work may guide managers on the best soil properties for monitoring the impacts of soil tillage on soil quality in agricultural areas that routinely use conventional tillage as a management practice. Keywords: minimum data set, soil aggregation, soil biological properties, soil chemical properties, soil degradation, soil enzyme activity, soil physical properties, soil quality., Introduction Soil degradation is a global problem in the 21st century, being more severe in tropical and subtropical regions (Lai 2015). Conventional tillage and the intensive soil use associated with [...]

The van Genuchten-Mualem (VGM) model is used largely to represent the relative soil hydraulic conductivity and soil water retention functions [[K.sub.r]([THETA]) and [THETA](h)]. Alternative equations proposed by Groenevelt and Grant (GRT) present advantages regarding mathematical versatility. Considering the VGM model cannot be analytically converted into the GRT model, this study empirically related parameters n and a (VGM) to parameters p and k (GRT). We used 90 value combinations of n and a and minimised the sum of squared differences between VGM and GRT models. Linear equations were fitted and validated using soil samples from the UNSODA database. A singular equation of p as a function of n was fitted, while a two-step procedure was required to correlate k and a. All fits resulted in very high precision (r [greater than or equal to] 0.999) and accuracy (RMSD [less than or equal to] 0.025 [m.sup.3] [m.sup.-3]) for the water retention function and very high precision (r [greater than or equal to] 0.994) for the hydraulic conductivity function. The accuracy for the [K.sub.r]([THETA]) function was high (RMSD [less than or equal to] 0.50) for 34 of the 40 tested soils. The derived empirical equations can be used to convert the equation parameters for [THETA](h) regardless of soil type, and for [K.sub.r]([THETA]) with some restrictions upon parameter combinations. Keywords: hydraulic conductivity, incomplete beta function, incomplete gamma function, mathematical models, modelling, soil hydraulic properties, soil physics, soil water retention., Introduction Water retention (WR) and hydraulic conductivity (HC) are imperative soil hydraulic functions used to describe water flow in the vadose zone. Relations between the variables volumetric soil water content [...]

Mesofauna represents a major component of soil biological community and play a critical role in maintaining soil quality, as well as a range of ecosystem functions. A split-split plot design was performed with the aim of identifying the main predictors (phytogeographical criteria, cover type and environmental variables) of edaphic community structure under the effect of desertification. The study also aimed to examine the spatial and seasonal distribution of mesofauna community according to phytogeographical criteria (shrubland vs grassland) and cover type (bare vs covered soil) in the north-western Patagonian steppe of Argentina. The relationship between edaphic fauna, environmental variables and site location was investigated using redundancy analysis (RDA), while the main predictors of edaphic community were analysed using generalised linear mixed models (GLMMs). A total of 43 taxa of Oribatida were found in 168 samples. GLMM approaches selected cover type due to its higher effect on mesofauna community. In this sense, cover type was more important than phytogeographical criteria and environmental variables as predictor of mesofauna community. These findings contribute to a better understanding of how the distribution of mesofauna community respond in Patagonia steppe. Keywords: acari, covered soil, degradation, grassland, microarthropods, Oribatida, predictors, shrubland., Introduction Mesofauna community plays a critical role in maintaining soil quality, as well as a range of ecosystem functions (Barrios 2007). Soil invertebrates are responsible for numerous functions such as [...]

The adoption of conservationist systems can improve the protection of soil organic matter (SOM) and mitigate greenhouse gas emissions. Thus, we aimed to quantify the soil carbon (C) and nitrogen (N) stocks, C content in the SOM fractions and microbial C ([C.sub.mic]) in the topsoil of an Acrisol under traditional and agrisilvicultural systems in the Southeast of Brazil. The evaluated treatments were native vegetation of Cerrado (NV), pasture of Urochloa brizantha (PAST), monoculture of pigeon pea (MCP), and agrisilvicultural system (Eucalyptus + pigeon pea; AGS). Soil samples were collected at depths of 0-5, 5-10, and 10-20 cm to determine the soil C and N contents and stocks, C associated with granulometric and humic fractions of SOM, and soil [C.sub.mic]. The C contents in AGS and MCP systems were similar to NV at 5-10 and 10-20 cm, and soil C stocks in AGS were similar to NV and higher than in PAST system at 0-20 cm. We found a higher percentage of protected C in the silt + clay fraction, and the AGS system contributed to an increase in this organomineral fraction at 10-20 cm soil depth. The C contents in the free light fraction (0-5 cm) and humin (5-10 and 10-20 cm) were also similar between AGS and NV, giving greater protection of SOM in both systems. For [C.sub.mic] and microbial quotient values we found no differences among the evaluated systems. The results indicated that after conversion of NV to different land uses, the AGS system more effectively increased the C stocks in the topsoil and protected the SOM. Keywords: agroforestry, carbon storage in soil, humic fractions, land use effects on soil, microbial quotient, organomineral fraction, pigeon pea, soil organic matter., Introduction Currently, the sustainability of native and agroecosystems is a topic of great relevance. Land use change and the intensive use of soil for agricultural production has accelerated the degradation [...]

Land clearing for cropping and grazing has increased runoff and sediment yield in Central Queensland. The Brigalow Catchment Study (BCS), was established to determine the effect of land clearing on water balance, soils, and productivity, and consisted of three catchments: brigalow forest, cropping, and grazing. Factors responsible for changes in and models for predicting sediment yield have not been assessed. Objectives of this study are to identify climatic, hydrological, and ground cover factors responsible for the increased sediment yield and to assess suitable models for sediment yield prediction. Runoff and sediment yield data from 1988 to 2018 were used to assess the Revised Universal Soil Loss Equation (RUSLE) and the Modified USLE (MUSLE) to predict the sediment yield in brigalow catchments. Common events among the three catchments and events for all catchment pairs were assessed. The sediment yield was approximately 44% higher for cropping and 4% higher for grazing than that from the forested catchment. The runoff amount (Q) and peak runoff rate ([Q.sub.p]) were major variables that could explain most of the increased sediment yield over time. A comparison for each catchment pair showed that sediment yield was 801 kg [ha.sup.-1] or 37% higher for cropping and 28 kg [ha.sup.-1] or 2% higher for grazing than for the forested catchment. Regression analysis for three different treatments (seven common events) and for different storm events (15 for forested, 40 for cropping, and 20 for grazing) showed that Q and [Q.sub.p] were best correlated with sediment yield in comparison with variations in ground cover. The high coefficient of determination ([R.sup.2] > 0.60) provided support for using the MUSLE model, based on both Q and [Q.sub.p], instead of the RUSLE, and Q and [Q.sub.p] were the most important factors for improving sediment yield predictions from BCS catchments. Keywords: brigalow clearing, ground cover treatment, peak runoff rate, RUSLE and MUSLE, runoff, sediment yield, small dry catchments, storm events., Introduction Broad-scale clearing of native vegetation for agricultural systems, including grazing, has strongly affected hydrological processes and sediment yield in Australia and around the world (Siriwardena et al. 2006; Thornton [...]

The disaggregation of conventional soil maps is an active research line inside the Digital Soil Mapping framework that aims to generate new cartographies by disclosing the non-explicit soil distribution pattern within the polytaxic or multi-component cartographic units. This article shows a comprehensive review of methodologies found after a bibliographic search in the Web of Science and Scopus databases. They are analysed regarding common factors such as the conventional soil map, environmental data sources and covariates, classification methods, and evaluation; likewise, those specific to the leveraging of conventional maps as the main source of soil information such as sampling scheme and assignment of soil categories for the classification. The applications were frequently carried out in small and medium areas with intensive and extensive conventional soil maps and featuring supervised classification methods. The definition of the training sets is a critical task that has a strong influence on their performance. The comparative analysis noted the potential of the reviewed disaggregation methodologies that adopted two-stage strategies: first, areas potentially associated with soil categories are delimited; and second, supervised models are built on them. Ultimately, the development of new disaggregation methodologies is possible by combining those strategies within each factor that yielded the best results in terms of accuracy. Keywords: agronomy, covariate importance, digital soil mapping, geostatistics, landform classification, soil-landscape modeling, soil mapping, soil map units, soil survey, spatial disaggregation., Introduction Soils fulfil essential environmental functions to sustain human life and, for this reason, access to information on their vertical variability (soil typology) and horizontal distribution (soil geography) across the [...]

Earthworms contribute to a wide range of process that underpin soil function and ecosystem services and are an important component of a soil's natural capital stocks. With increasing interest in soil health, it is important to better understand the type of earthworm community required to enhance soil functions. This is of particular interest in New Zealand where pasture systems are dominated by exotic earthworm species and low ecological diversity. Two separate mesocosm experiments were established to explore the interaction between earthworm abundance and ecological diversity as it influences soil functions. Experimental increases in earthworm abundance increased soil macroporosity and water infiltration, increased plant nitrogen (N) and plant growth. Although some benefits were observed at the lowest earthworm abundances, the greatest benefits were seen at the higher abundances. Earthworm ecological diversity is also critical to ensure soil functions are optimised. For example, the single species of Aporrectodea caliginosa alone was not able to improve water infiltration or pasture production. However, when this species was found in combination with Aporrectodea longa, there was positive influence on soil functions despite the abundance of A. longa itself not increasing. This study highlights the importance of including a measure of ecological diversity alongside a measure of abundance to assess soil biological health. Keywords: biological indicator, earthworm abundance, earthworm ecological groups, ecosystem services, mesocosms, plant growth, soil health, water infiltration., Introduction Earthworms are ecosystem engineers, significantly altering the ecosystem they live in (Jones et al. 1994). Earthworms feed on organic matter, ensuring its decomposition and incorporation, increasing plant available nutrients, [...]

Dripping rainfall simulators are important instruments in soil research. However, a large number of non-standardized simulators have been developed, making it difficult to combine and compare the results of different studies in which they were used. To overcome this problem, it is necessary to become familiar with the design and performances of the current rainfall simulators. A search has been conducted for scientific papers describing dripping rainfall simulators (DRS) and papers that are thematically related to the soil research using DRS. Simulator design analysis was performed integrally, for simulators with more than one dripper (DRS>1) and with one dripper (DRS=1). Descriptive and numerical data were extracted from the papers and sorted by proposed categories, according to which the types and subtypes of used simulators are determined. The six groups of elements that simulators could consist of have been determined, as well their characteristics, representation and statistical analyses of the available numerical parameters. The characteristics of simulators are analyzed and presented, facilitating the selection of simulators for future research. Description of future simulators in accordance to the basic groups of simulator elements should provide all data necessary for their easier replication and provide a step closer to the reduction of design diversification and standardization of rainfall simulators intended for soil research. [ABSTRACT FROM AUTHOR]