Soil Physical Parameters Research Articles

Terahertz Spectroscopy for Proximal Soil Sensing: An Approach to Particle Size Analysis.

Spatially resolved soil parameters are some of the most important pieces of information for precision agriculture. These parameters, especially the particle size distribution (texture), are costly to measure by conventional laboratory methods, and thus, in situ assessment has become the focus of a new discipline called proximal soil sensing. Terahertz (THz) radiation is a promising method for nondestructive in situ measurements. The THz frequency range from 258 gigahertz (GHz) to 350 GHz provides a good compromise between soil penetration and the interaction of the electromagnetic waves with soil compounds. In particular, soil physical parameters influence THz measurements. This paper presents investigations of the spectral transmission signals from samples of different particle size fractions relevant for soil characterization. The sample thickness ranged from 5 to 17 mm. The transmission of THz waves was affected by the main mineral particle fractions, sand, silt and clay. The resulting signal changes systematically according to particle sizes larger than half the wavelength. It can be concluded that THz spectroscopic measurements provide information about soil texture and penetrate samples with thicknesses in the cm range.

Relación de parámetros edáficos sobre la diversidad y distribución espacial de nematodos de vida libre

Se realizó un estudio sobre la diversidad, riqueza, dominancia y equidad de la nematofauna y la relación de estos organismos con algunos parámetros físicos y químicos del suelo en 15 sitios de tres localidades de la Subregión Sabana departamento de Sucre, Colombia. Utilizando la metodología de Jenkins (1964), se extrajeron un total de 4.683 individuos, identificados utilizando claves taxonómicas, en 22 géneros y uno no determinado (c.f Dorylaiminae). Los parámetros edáficos se realizaron utilizando las metodologías del IGAC (2006) y la diversidad se estimó haciendo uso de índices de diversidad; relacionando estos dos factores se observó mayor abundancia de nematodos en suelos de textura franco arenosa, principalmente de los géneros Criconemella, c.f. Dorylaiminae y Helycotilenchus. La humedad, porosidad, materia orgánica y pH, no presentan relación en cuanto a diversidad de los nematodos identificados. Contrario con la textura del suelo que si influyen en la abundancia y la fracción limo en diversidad. Sin embargo la presencia de los géneros Criconemella y c.f Dorylaiminae no están determinada por estos parámetros edáficos.

Tillage management impacts on soil compaction, erosion and crop yield in Stagnosols (Croatia)

The sustainability of agroecosystems is closely related to successful soil conservation. Sustainable land use practices are crucial to reduce the impacts of agriculture on land degradation and maintain long-term soil productivity. In this context, is important to avoid practices that deteriorate the soil (e.g. soil erosion), and find the most suitable to maintain soil and crops productivity. The objective of this work is to compare the impact of different tillage systems on soil compaction, erosion and crop production on clay loam Stagnosols in Croatia. Three tillage treatments were studied: conventional tillage (CT), no-tillage (NT) and deep tillage (DT). Soil water content, bulk density and penetration resistance were determined in the 0–10, 10–20, 20–30 and 30–40cm soil depths. Soil erosion was measured during rainfall events. The results showed that tillage treatments influenced the soil physical parameters, soil loss and crop yields. During first four years of study NT increased (p<0.05) bulk density in the 0–10cm depth by an average of 8% and 7% in relation to CT and DT. Conventional tillage treatment increased (p<0.05) bulk density in the 30–40cm depth by an average of 6% and 5% in relation to NT and DT. No-tillage treatment had a significantly higher penetration resistance (PR) comparing to CT and DT in 2012 and 2014. During the flowering time of 2013, PR was significantly higher in NT at 20–30cm depth than in the other treatments. This was observed also in 2014 at 20–30 and 30–40cm depth. Average annual soil loss under NT (0.53tha−1year−1) and DT (3.11tha−1year−1) were significantly lower than that under CT (13.11tha−1year−1). No-tillage had lower crop grain yields compared to CT and DT, but higher yields in dry years, as consequence of the high capacity for water retention. We recommended DT treatment for investigation at the field scale to assess its suitability for wider application on clay loam soils on sloped areas.

Soybean development as a function of traffic of tractor with radial tires

ABSTRACT This study aimed to evaluate the development of soybean as a function of traffic levels of an agricultural tractor equipped with radial tires in two collection areas. The experiment was conducted in an area located at the State University of Maringá, Campus of Umuarama-PR, Brazil, in a soil classified as Red Oxisol with sandy texture. The experiment was set in a 5 x 2 factorial arrangement, with five levels of traffic on the same track (T1 = 1, T2 = 6, T3 = 11, T4 = 16 and T5 = 21 tractor passes), two collection areas (A1 = on the track and A2 = off the track) and four replicates. Soil physical parameters and characteristics of the soybean plants were evaluated. Soybean yield on the track did not show significant difference up to 6 passes. It was concluded that the traffic levels and soil resistance to penetration interfere with soybean yield for both collection areas.

Organic amendment type and application frequency affect crop yields, soil fertility and microbiome composition

Vegetable cultivation under plastic tunnels provides high-quality crop yields but negatively affects soil fertility, especially when conventional agricultural system (e.g., use of synthetic mineral fertilizer and agrochemicals) was adopted. In this regard, the use of organic amendments has been proposed as a reliable and effective approach for soil fertility recovery. The aim of this study was to assess the effects of different organic amendments and application frequency on crop yield, soil fertility and soil microbial communities. A 1-year long mesocosm experiment was performed by conditioning a soil with different organic amendment types and frequency of application, compared with the ordinary soil management based on mineral fertilizers and fumigation. Soil fertility was assessed by determining physical and chemical soil parameters, whereas microbial community functioning and structure were assessed by high-throughput sequencing of bacterial and eukaryotic rRNA gene markers and BIOLOG EcoPlates™. Compared to the organic amendment, the use of synthetic fertilizer had a higher crop production but negatively affected pH, soil organic carbon content and soil aggregation. Diversity and richness of bacteria and eukaryotic were lower in the synthetic than in the organic amendments. The addition of organic amendments promoted the growth of Acidobacteria and Gemmatimonadetes bacteria. On the contrary, members of Actinobacteria and Proteobacteria were more abundant in the soil treated with synthetic fertilizer. This study increases our current knowledge on the effect of the synthetic and organic amendment applications on crop yield, soil fertility and soil microbial community functionality.

Methane oxidation in lead-contaminated mineral soils under different moisture levels

Methane (CH4) oxidation in soil reduces the concentration of this greenhouse gas due to the activity of methanotrophic bacteria. This process is influenced by chemical and physical parameters of soil. We tested the methanotrophic activity of selected mineral soils (Mollic Gleysol, Haplic Podzol, Eutric Cambisol) contaminated with lead (Pb) under different soil water potentials (pF 0; 2.2; 3.2). The heavy metal was added as PbCl2 in two doses. Together with the initial content of Pb in soils, the final contents of heavy metal in different soils were 11.6 and 30.8 mg kg−1 in Eutric Cambisol, 7.1 and 26.3 mg kg−1 in Haplic Podzol, and 12.2 and 31.4 mg kg−1 in Mollic Gleysol (dry mass of the soil is specified in all cases). The results showed relatively low sensitivity of methane oxidation to the addition of the heavy metal. The major factor controlling this process was soil water content, which in most cases turned out to be the most optimal at pF = 2.2.

High Temporal and Spatial Variability of Atmospheric-Methane Oxidation in Alpine Glacier Forefield Soils.

Glacier forefield soils can provide a substantial sink for atmospheric CH4, facilitated by aerobic methane-oxidizing bacteria (MOB). However, MOB activity, abundance, and community structure may be affected by soil age, MOB location in different forefield landforms, and temporal fluctuations in soil physical parameters. We assessed the spatial and temporal variability of atmospheric-CH4 oxidation in an Alpine glacier forefield during the snow-free season of 2013. We quantified CH4 flux in soils of increasing age and in different landforms (sandhill, terrace, and floodplain forms) by using soil gas profile and static flux chamber methods. To determine MOB abundance and community structure, we employed pmoA gene-based quantitative PCR and targeted amplicon sequencing. Uptake of CH4 increased in magnitude and decreased in variability with increasing soil age. Sandhill soils exhibited CH4 uptake rates ranging from -3.7 to -0.03 mg CH4 m-2 day-1 Floodplain and terrace soils exhibited lower uptake rates and even intermittent CH4 emissions. Linear mixed-effects models indicated that soil age and landform were the dominating factors shaping CH4 flux, followed by cumulative rainfall (weighted sum ≤4 days prior to sampling). Of 31 MOB operational taxonomic units retrieved, ∼30% were potentially novel, and ∼50% were affiliated with upland soil clusters gamma and alpha. The MOB community structures in floodplain and terrace soils were nearly identical but differed significantly from the highly variable sandhill soil communities. We concluded that soil age and landform modulate the soil CH4 sink strength in glacier forefields and that recent rainfall affects its short-term variability. This should be taken into account when including this environment in future CH4 inventories.IMPORTANCE Oxidation of methane (CH4) in well-drained, "upland" soils is an important mechanism for the removal of this potent greenhouse gas from the atmosphere. It is largely mediated by aerobic, methane-oxidizing bacteria (MOB). Whereas there is abundant information on atmospheric-CH4 oxidation in mature upland soils, little is known about this important function in young, developing soils, such as those found in glacier forefields, where new sediments are continuously exposed to the atmosphere as a result of glacial retreat. In this field-based study, we investigated the spatial and temporal variability of atmospheric-CH4 oxidation and associated MOB communities in Alpine glacier forefield soils, aiming at better understanding the factors that shape the sink for atmospheric CH4 in this young soil ecosystem. This study contributes to the knowledge on the dynamics of atmospheric-CH4 oxidation in developing upland soils and represents a further step toward the inclusion of Alpine glacier forefield soils in global CH4 inventories.

Mechanical Characteristics of Stabilized Clay under the Influence of both Acidic and Alkalic Additives

To study the influence of the coexistence condition of acidic and alkalic additives on the mechanical performance of stabilized clay based on the processes for obtaining the basic physical parameters of soil and analyzing the stabilization mechanism of ionic and alkalic soil stabilizers, an experiment on the mechanical behavior characteristics of stabilized clay was performed using different types of ionic and alkalic stabilizers through a series of laboratory tests. The following results are obtained. (1) Typical soil is low liquid limit clay, and the ionic stabilizer with an optimal content of 0.014% mass ratio to dry soil exhibits strong acidity. (2) As a result of its unique molecular structure, the double electric-combined water film becomes thin rapidly during compaction molding, in which the compactness of clay particle structure increases. (3) The 7-day unconfined compressive strength can be improved with different contents of the ionic stabilizer. (4) Except for the high lime soil mixture, the compaction degree of soil exerts a pronounced effect on the stabilization performance of an ionic stabilizer and the least compaction degree should be over 96%. (5) The unconfined compressive strength, indirect tensile strength, and freeze-thaw performance of the acid-alkali-stabilized soil demonstrate a gradually increasing tendency with an increase in curing time, however, the evolution characteristic of strength exhibits an advantageous superposition threshold value when compared to the alkali-stabilized clay. The neutralization reaction and oil membrane of soil particles will inhibit the later reaction processes of carbonation, pozzolanic, and hydration of lime-|cement-stabilized soil.

Evaluation of Diversity of Soil Invertebrate Communities Near Forests of Gohagoda and Udawattakele in Kandy, Sri Lanka

Soil faunal activity is essential for the functioning of all terrestrial ecosystems. Soil fauna are important in the physical and chemical transformation of litter, the maintenance of soil fertility and sustained productivity. By products of human activities affect the proper functioning of the soil fauna with a concomitant decrease in long term soil productivity. The fauna could be used as early indicators of changes brought about in soil properties by pollutants. In Sri Lanka studies of this nature are lacking and even baseline data against which changes could be measured are not yet available. Evaluation of possible indicator organisms coupled with soil chemical analysis to examine soil pollution is crucial. A field experiment was set up in Kandy in two forest areas near the Gohagoda dumping site and the Udawattakele forest reserve area to investigate the soil and leaf litter invertebrates. The soil invertebrate fauna were extracted in both sampling sites by using NaCl floatation method and Baermann funnel. The leaf litter invertebrates were extracted using the Tullgren funnel. Soil physical and chemical parameters were analysed. The catchment forest near Gohagoda had high nitrate (0.71%), phosphate (0.38%) and sulphate (0.07%) concentrations compared to that of in Udawattekele (0.036%, 0.07% and 0.03%, respectively) which revealed high pollution rate in Gohagoda. This data coincided with the invertebrate diversity in the two areas, Fifteen different invertebrate phyla were excavated and amongst them Collembola, Acarina and Nematoda were the dominant phyla in both forests. Collembolans were significantly high in Udawattakele. The Udawattakele forest area had the highest taxon and individual numbers of invertebrates. The results revealed that according to the Tullgren funnel Bearmaan funnel and NaCl floatation method Udawattekele forest showed high species diversity by Brillouin, Menhinick, Margalef, Berger-Parker, Shannon and Simpson indices and is significantly high in Udawattakele (<0.001). Overall Udawattekele has a high diversity and evenness than that of Gohagoda area. This comprehensive analysis of invertebrate diversity shows that it may be used as possible indicator of soil quality. Thus it can be assumed that collembolans can be easily assessed and used as probable indicators of pollution. Therefore incorporating the chemical and biological data gives very promising and reliable conclusions about the degree of soil pollution. Soil invertebrates should also be considered as a resource that needs to be properly managed to enhance ecosystem services. Keywords: Soil invertebrates, Diversity, Gohagoda, Udawattakele

The river harbour of Ostia Antica - stratigraphy, extent and harbour infrastructure from combined geophysical measurements and drillings

We performed a combined geophysical and geoarchaeological survey of the harbour of ancient Ostia, Italy, to investigate the extent of the former harbour basin, the sedimentary infill and possible building remains around the harbour. Besides geoarchaeological results the paper highlights the advantage of combining vibracore drilling with different geophysical prospection methods, which are sensitive to different physical soil parameters. Geophysical methods applied were electrical resistivity tomography (ERT), ground penetrating radar (GPR) and seismics with shear and compressional waves. The extent and shape of the harbour basin were determined by ERT profiling. The ERT profiles were compiled into a 3D-model showing that the early lagoonal harbour basin was at least 100 m × 50 m wide. Its southern border was confirmed by GPR measurements clearly imaging the former land-water transition and the onset of ancient onshore building construction. At its eastern border a consolidated horizon could be mapped in 2–3 m depth by compressional wave tomography. This horizon most likely represents a cemented ramp, a small part of which had been excavated in a previous study. The sedimentary fill of the former harbour basin was investigated by a combination of vibracoring, ERT and seismics. The ERT profiles serve for inter- and extrapolating the vibracore stratigraphy from the coring locations over the whole harbour area. It turned out that one sedimentary unit, which is important for the harbour development, could not be resolved by ERT but clearly shows up in seismic velocity-depth profiles instead. It is a thin coarse-grained high-energy layer in 1–2 m depth, which was caused by a tsunami according to a previous study. This layer separates two harbour phases: an older lagoonal harbour phase underneath and a younger fluvial harbour phase above it. The high-energy layer represents a thin band of 100% increased shear wave velocity compared to the more fine-grained layers, in which it is embedded. This study is the first to show that tsunami-type sedimentary layers may be mapped by shear wave profiling.

Modelling soil organic matter dynamics on a bare fallow Chernozem soil in Central Germany

Soil organic matter (SOM) can be characterised by soil organic carbon (SOC) and/or total nitrogen (TN). The observed dynamics of SOC and TN in the topsoil of a 28-year-old fallow experiment on Haplic Chernozem was modelled using the Candy Carbon Balance (CCB) model. This study selected two treatments from this experiment where the soil was kept bare with mechanical or chemical (herbicides) treatments. The CCB model was improved to include the SOC related change of soil physical parameters and dynamic handling of the physically stabilised SOM pool. Over 28years of bare fallow the top soil lost about 10t/ha of SOC and >1t/ha of TN. The results from observation and modelling reflected the increased SOM turnover due to soil tillage. The modelled size of the physically stabilised SOC pool was about 55% of total SOC and only reduced slowly during the almost three decades, but the implementation of this effect improved simulation results and reduced the relative RMSD (unitless) from 0.051 to 0.044 for SOC and from 0.053 to 0.049 for TN error level. From these results we conclude that the larger the SOM change the more important is the integration of the turnover of physically stabilised SOM within the modelling approach.

Native communities of arbuscular mycorrhizal fungi associated with Capsicum annuum L. respond to soil properties and agronomic management under field conditions

Abstract We examined the effects of agronomic management (low, moderate, and high inputs) and soil properties on arbuscular mycorrhizal fungi (AMF) community structure collected from the rhizosphere of Capsicum annuum cultivated in six agroecosystems in Mexico. Chemical and physical soil parameters differed among agroecosystems. Native communities of AMF-morphospecies differed between agroecosystems depending on intensity of agronomic practice. In total 33 AMF-morphospecies were identified (11genera, and seven families). Soil P availability and pH negatively affected the distribution and abundance of the AMF species. High input management resulted in significant modifications in the composition and structure of the AMF communities. Agroecosystems with high or moderate input management showed 35% less AMF-morphospecies when compared to low input management systems. The most diverse AMF community was observed from agroecosystems with either moderate or low input management. Funneliformis geosporum, Claroideoglomus claroideum and C. luteum were the predominant species observed in this study. High similarity (>75%) in the structure of AMF communities among agroecosystems was found, which suggest that the observed differences between AMF communities from agroecosystems with high input management compared to that from low and moderate input management, may be due to changes in species composition.

Nature based solutions to mitigate soil sealing in urban areas: Results from a 4-year study comparing permeable, porous, and impermeable pavements

Soil sealing is one of the most pervasive forms of soil degradation that follows urbanization and, despite innovative pavements (i.e. pervious) are being installed in urban areas to mitigate it, there is little research on the effects of pervious pavements on soil water and carbon cycle and on the physiology of urban trees. The aim of this 4-year experiment was to assess the effects of three pavements, differing in permeability to water and gases, on some soil physical parameters, and on growth and physiology of newly planted Celtis australis and Fraxinus ornus. Treatments were: 1) impermeable pavement (asphalt on concrete sub-base); 2) permeable pavement (pavers on crushed rock sub-base); 3) porous design (porous pavement on crushed rock sub-base); 4) control (unpaved soil, kept free of weed by chemical control). Soil (temperature, moisture, oxygen content and CO2 efflux) and plant (above- and below-ground growth, leaf gas exchange, chlorophyll fluorescence, water relations) parameters were measured.All types of pavements altered the water cycle compared to unpaved soil plots, but this disturbance was less intense in porous pavements than in other soil cover types. Porous pavements allowed both higher infiltration and evaporation of water than both pavers and asphalt. Reduction of evaporative cooling from soil paved with permeable and impermeable pavements contributed to significant soil warming: at 20cm depth, soils under concrete pavers and asphalt were 4 and 5°C warmer than soil covered by porous pavements and unpaved soils, respectively. Thus, enhancing evaporation from paved soil by the use of porous pavements may contribute to mitigating urban heat islands. CO2 greatly accumulated under impermeable and permeable pavements, but not under porous pavements, which showed CO2 efflux rates similar to control. Soil oxygen slightly decreased only beneath asphalt.Growth of newly planted C. australis and F. ornus was little affected by pavement type. Tree transpiration rapidly depleted soil moisture compared to the not-planted scenario, but soil moisture did not fall below wilting point (particularly in the deeper soil layers, i.e. 40–50cm) in any treatment. While C. australis showed similar leaf gas exchange and water relations in all treatments, F. ornus showed a depression in CO2 assimilation and slight signs of stress of the photosynthetic apparatus when planted in soil covered with impermeable pavement.The effects of soil cover with different materials on tree growth and physiology were little, because newly planted trees have most of their roots still confined in the unpaved planting pit. Still, the reduction of soil sealing around the planting pit triggered the establishment of sensitive species such as ash. Further research is needed to assess the effects of different pavement types on established, larger trees.

Comparison of soil amendments for reforestation with a native multipurpose tree under semiarid climate: Root and root tuber response of Spondias tuberosa

The Caatinga biome, characterized by a species-rich seasonally dry tropical forest, but highly disturbed covers most of Brazil's Northeast. Endemic to this biome is the multipurpose tree Spondias tuberosa Arr., which forms numerous root tubers to resist drought stress. In order to develop improved soil management for reforestation with S. tuberosa the response of its root system to different soil amendments was studied with 52 seedlings, using goat manure, clay substrate, biochar as soil amendments, and mineral fertilizer. The default root architecture of three-year-old S. tuberosa and the relation between soil physical parameters and fine root dry matter (≤2mm), root length density, root tuber volume, root tuber fresh weight, and shoot-root ratio were analyzed.Seedlings still formed a tap root with a maximum rooting depth of 63cm and a maximum horizontal extent of 35cm, developing 2–4 root tubers per seedling. Fine root dry matter in 3000cm3 soil samples differed significantly, ranging from 0.23g in the control to 0.03g in the treatment combining manure with biochar and mineral fertilizer. According to the orthogonal contrast, manure was the pivotal soil amendment affecting fine root dry matter negatively. Simultaneously, manure application led to increased soil water content compared to treatments without . The shoot-root ratio increased by 32% compared to the control, when S. tuberosa was grown in wet soils. Root tuber growth was significantly enhanced by manure addition. This effect is attributed to a reduction of soil bulk density as root tuber volume exhibited a negative correlation with soil bulk density. There was no statistical relationship between root tuber volume and seedling survival during the field experiment. Compared with the control, neither clay, biochar nor solely mineral fertilization significantly affected root growth.Soil management focused on improving water availability is suspected of hampering fine root growth of S. tuberosa seedlings, whereas reducing soil bulk density enables better root tuber development and could, therefore, be a promising measure to increase S. tuberosa drought resistance in the long term for more successful reforestation. Disregarding its negative impact on fine root growth, we assume manure is the most promising amendment among the tested treatments, due to its positive effect on root tuber growth.

Long-term Effect of Manure Application in a Certified Organic Production System on Soil Physical and Chemical Parameters and Vegetable Yields

In 1999, West Virginia University (WVU) established an organic farming systems project with a market garden section consisting of 32 plots measuring 16 × 25 ft arranged in a completely randomized design. Sixteen of these plots were managed as high-input and 16 as low-input plots. High-input plots received 10 tons/acre per year of dairy manure and a rye-vetch (Secale cereale and Vicia villosa) cover crop during each winter season since the inception of the experiment in 1999. Fertility in low-input plots was managed solely with an annual rye-vetch cover crop while both treatments also received 5 tons/acre of mixed species hay used as mulch in 2 of every 4 years. A 4-year rotation of crops, green bean (Phaseolus vulgaris), zucchini (Cucurbita pepo), tomato (Solanum lycopersicum), green pepper (Capsicum annuum), and lettuce (Lactuca sativa) in the Fabaceae, Cucurbitaceae, Solanaceae, and Asteraceae families, was established in 1999 and has been maintained ever since. Soil organic matter (SOM) in the upper 6 inches of the soil profile (4.4% in 1999) has remained unchanged in low-input plots at 5.2% in 2004 and 5.4% in 2014, the year following transition and most recent data collection, respectively. During this same time period, significant increases in SOM from 6.4% in 2004 to 8.7% in 2014 were observed in high-input plots. Bulk density was lower in high-input plots than low-input plots in 2014. Despite these improvements in soil quality, high-input plots showed very high levels of phosphorus and potassium. Over the duration of the experiment, yearly manure application increased yields by 22% in all crops combined; however, individual crops responded quite differently. The yield was 9%, 25%, 24%, and 24% higher in high-input plots than in low-input plots for tomato, pepper, zucchini, and green bean, respectively. Manure application in addition to green manures and hay mulch incorporation was found to result in significant economic returns.

Variation in bioactive compounds and antiradical activity of Moringa oleifera leaves: influence of climatic factors, tree age, and soil parameters

Moringa oleifera Lam. (Moringa) leaves are a significant source of phytochemicals with different bioactivities carrying human health benefits. This study was undertaken to investigate the effects of the tree age, soil physical and chemical parameters, and climatic factors, on the content of gallic acid, total phenolics, total carotenoids, and ascorbic acid and on the antiradical activity (DPPH and ABTS assays) of ethanolic extracts obtained from Moringa freeze-dried leaves. Multivariate data analysis showed that the bioactive compounds measured as reference and the antiradical activity from Moringa leaves presented correlation with climatic factors (precipitation, humidity, and radiation) and with soil nutrients, principally with the K and P contents. Tree age was positively correlated with the total carotenoids contents, and inversely correlated with the ascorbic acid contents. This information offers an understanding on variations in bioactive compounds and antiradical activity in Moringa leaves influenced by climatic factors, soil, and tree age, which may help in the estimation of the antioxidant potential present in the plants during different harvest times.

Estimation of terrestrial radionuclide concentration and effect of soil parameters on exhalation and emanation rate of radon

The soil samples collected from the different locations of the Jaipur and Ajmer districts of Rajasthan have been analysed for 232Th, 226Ra and 40K content using gamma spectrometry. The average concentration of the 232Th, 226Ra and 40K in soil samples comes out to be 69, 55 and 884Bqkg−1. The Emanation and Exhalation rate of the 222Rn, 220Rn from the collected soil samples have been measured. As the 222Rn and 220Rn originates from the solid grains of the medium and migrate through its pore space, it is expected to get affected by various soil parameters. An attempt has been made to see the effect of physical soil parameters on the Exhalation and Emanation rate of the 222Rn and 220Rn. The results of the present study show the dominance of the soil parameters on the 222Rn, 220Rn emanation and migration through the medium.

Eleven Years' Effect of Conservation Practices for Temperate Sandy Loams: I. Soil Physical Properties and Topsoil Carbon Content

Core Ideas Moldboard plowing decreased VESS score and soil penetration resistance. Reduced tillage combined with residue retention enhanced soil structural stability. Residue retention alleviated unfavorable soil structure effects of reduced tillage. Clay and SOC were confirmed as key factors affecting soil structure. Combining minimal soil disturbance and residue retention improved soil structure. Conservation agriculture (CA) has been suggested as a means of making intensification of agriculture sustainable. The purpose of this study was to understand and quantify long‐term individual and combined effects of key conservation practices on soil physical properties and topsoil C content. Field experiments were conducted in 11‐ to 12‐yr‐old experiments on two Danish sandy loams at Foulum and Flakkebjerg. Three crop rotations/residue management treatments were compared and tillage was included as a split‐plot factor. The tillage systems were moldboard plowing to a depth of 20 cm (MP), direct drilling (D) and harrowing to a depth of 8 to 10 cm (H). Soil sampling and in‐field measurements were performed in autumn 2013 and spring 2014. In the field, soil structure was visually evaluated and penetration resistance (PR) measured. Soil C, wet stability (clay dispersion and wet aggregate stability), and soil strength were determined in the laboratory. The MP soil had a uniform soil organic carbon (SOC) content in the 0‐ to 20‐cm depth of topsoil, whereas H and D resulted in SOC accumulation near the soil surface. Plowing resulted in the best visually assessed topsoil structure and had the lowest PR. However, H and D in combination with residue retention gave the best structural stability. Residue retention alleviated negative effects of reduced tillage on PR and improved wet stability in the MP treatment at the Foulum site. Clay and SOC correlated well with soil physical parameters, confirming their important role in soil structure formation and stabilization. Our study showed benefits of combining key CA elements, although longer‐term studies are most likely needed to reveal the full potential.

Nitrogen turnover, crop use efficiency and soil fertility in a long-term field experiment amended with different qualities of urban and agricultural waste

Organic wastes contain significant amounts of organic matter and nutrients and their recycling into agriculture can potentially contribute to closing the natural ecological cycle. The aim of this study was to evaluate the improvement in overall soil fertility and soil nitrogen (N) supply capacity in a long-term field experiment with repeated application of different urban and agricultural organic waste amendments. Soils from the CRUCIAL field experiment in Denmark, in which diverse types of urban (human urine, sewage sludge, composted household waste) and agricultural wastes (cattle slurry, farmyard manure and deep litter) have been applied annually for 11 years (at normal and accelerated rates), were used to estimate the effects of the different qualities of organic wastes on soil fertility, N turnover and crop N availability. Soil physical fertility parameters, such as water retention and total carbon, improved with the application of organic wastes. Cattle manure, sewage sludge and composted household waste in single or accelerated rates of application increased soil total N by 13–131% compared to the mineral fertiliser NPK treatment. The highest net N mineralisation capacity was observed for the accelerated rate of composted household waste, followed by all the other organic waste amendments and with the lowest net N mineralisation in the NPK-only and the unfertilised treatments. In soils amended for 11 years with NPK, human urine, cattle slurry, sewage sludge, cattle farmyard manure, cattle deep litter and composted household waste, the apparent crop N-use efficiencies (NUE, compared to unfertilised control) were 88, 73, 55, 51, 21, 16 and 11%, respectively. The continuous application of organic wastes generally increased NUE in the last year in comparison with the first year, except for composted household waste where N-use efficiency declined from 27 to 11%. The corresponding long-term mineral fertiliser N-equivalent (MFE) value ranged between 82% (human urine) and 13% (compost). Overall, continuous application of organic wastes improved soil fertility, with low C:N waste improving soil N availability, crop uptake and NUE the most, while the most C-rich and high C:N organic wastes (cattle deep litter and household waste compost) had a negative effect on crop NUE over time.

Modeling soil cation exchange capacity using soil parameters: Assessing the heuristic models

Accurate knowledge about soil cation exchange capacity (CEC) is very important in land drainage and reclamation, groundwater pollution studies and modeling chemical characteristics of the agricultural lands. The present study aims at developing heuristic models, e.g. gene expression programming (GEP), neuro-fuzzy (NF), neural network (NN), and support vector machine (SVM) for modeling soil CEC using soil parameters. Soil characteristic data including soil physical parameters (e.g. silt, clay and sand content), organic carbon, and pH from two different sites in Iran were utilized to feed the applied heuristic models. The models were assessed through a k-fold test data set scanning procedures, so a complete scan of the possible train and test patterns was carried out at each site. Comparison of the models showed that the NF outperforms the other applied models in both studied sites. The obtained results revealed that the performance of the applied models fluctuated throughout the test stages and between two sites, so a reliable assessment of the model should consider a complete scan of the utilized data set, which will be a good option for preventing partially valid conclusions obtained from assessing the models based on a simple data set assignment.