The effects of the herbicide tebuthiuron on seedlings of Mimosa pigra and native floodplain vegetation in northern Australia

An accurate description of soil water vapour sorption isotherms (WSIs) is significant for modelling numerous soil processes. Soil clay content predictions from WSIs can be cost effective and convenient, although the approach has only been investigated on non‐saline soils. To investigate relationships among the clay content, water vapour sorption characteristics and salinity of soils, the WSIs of 35 soil samples were measured at four salinity levels. The characterization of the isotherms indicated that the double log polynomial (DLP) model was optimal for fitting the WSIs of soils with various salinity levels. Moreover, existing clay content prediction models based on WSIs had poor applicability to saline soils, and soil salinity had a greater influence than the soil clay content on the shape of the WSIs. Therefore, multiple linear regression (MLR) models were established to explain the relationships among the soil clay content, salt content and geometrical characteristics of the WSIs. Specifically, a significant correlation was observed between the soil salt content and the sub‐area at the end interval of the WSIs (relative vapour pressure (RH) = 0.83 to 0.93, coefficient of determination (R2) > 0.9) and the hysteresis sub‐area in the middle of the WSIs (RH = 0.53 to 0.63, R2 > 0.8). Furthermore, a strong linear relationship existed between the clay content and the sub‐areas of desorption and hysteresis at the end interval of the WSIs (RH = 0.73 to 0.83, R2 > 0.9) in the non‐saline soils only. Based on the investigated samples, the geometrical characteristics of WSIs were affected predominantly by the soil clay content when the salt content was low (electrical conductivity (EC) < 4.5 dS m−1), whereas salinity was the main influencing factor for samples that have high salt content (EC ≥ 4.5 dS m−1). Moreover, the WSIs' geometric characteristics had the potential to predict soil salt content and clay content under certain limited conditions. Isotherm models that accurately describe water sorption isotherms of saline soils were identified. Soil clay content and salinity affect water sorption isotherms differently depending on soil salinity level. Robust relationships between the soil salinity, clay content and WSI shape properties were established.Highlights Isotherm models that accurately describe water sorption isotherms of saline soils were identified. Soil clay content and salinity affect water sorption isotherms differently depending on soil salinity level. Robust relationships between the soil salinity, clay content and WSI shape properties were established.

Recent research has revealed the patterns of spatial and temporal variability of crop yields for the Polissia and the Forest-Steppe regions of Ukraine. In addition, the approaches to differentiating agroeconomic and agroecological components in the variability of the productive potential of the territories were developed. Approaches have been developed to quantify the spatial and temporal variability of soil erosion for individual areas of the region. The issue of assessing the impact of erosion processes on crop yields at the regional level remains unresolved. The diversity of landscapes and soil cover in Polissia and the Forest-Steppe of Ukraine was assessed in this article. The research covered 10 administrative regions of the north and northwest of Ukraine, which are located mainly within mixed forests (Polissia) and the eastern European forest steppe (Forest-Steppe). Part of the territory is tangential to the Carpathian mountain forests and the Pontic steppe. Within the study area, 30 WRB soils were identified. The largest area is occupied by Phaeozems Albic (21.7% of the total area of the region). These soils are located mainly in the southern and central parts of the region. In the north of the region, Phaeozems Albic form an almost continuous cover, and to the north, the areas of these soils become island-like. Phaeozems Luvic cover 12.1% of the region's territory. The Phaeozems group also includes Phaeozems Gleyic (0.93%), Phaeozems Haplic (0.13%), and Phaeozems Sodic (1.78%). Albeluvisols Umbric (17.1%) occupy a significant part of the region's territory. These soils occupy the north of the region and extend south along the Dnipro River floodplain. Spatially close to these soils are Albeluvisols Gleyic (12.8%). In the western part of the region, in Prykarpattia, there are Albeluvisols Stagnic (0.82%). The organic carbon content in the soils of the administrative districts of the region in the 0-5 cm layer was 5.2±3.3% and ranged 0.5% to 23.9%. In the layers of 5–15 and 15–30 cm, this figure decreased to 1.9 ± 1.1% and 1.9 ± 1.0%, respectively. In the 30–60 cm layer, the organic carbon content was 1.4 ± 0.8% and ranged 0.1% to 6.1%. The lowest organic carbon content was observed in the north central part of the region, and the highest content was observed in the north-east and north-west of the region. In the south of the region, there was found a strip of soils with moderate organic carbon content. The lowest content of organic carbon is characteristic of Albeluvisols and Podzols, which are located in the north of the region. In turn, the highest content of organic carbon is characteristic of organogenic Histosols, which, together with Albeluvisols and Podzols, form the basis of the soil cover structure of the territories in the northeast and northwest of the region. It should be noted that the agronomic role of these soils is insignificant, and their organic carbon content cannot be considered as a traditional indicator of fertility. Nevertheless, organic carbon is a reliable indicator of the anti-erosion properties of both natural and agricultural soils. The organic carbon content of Chernozems is quite high, which is a factor in the high fertility of these soils and their importance in agricultural production. The organic carbon content of Fluvisols and Gleysols is naturally high. The importance of these hydromorphic soils is due to their high productive potential, which ensures their use in agriculture. It is also worth noting their high seed protection potential. Phaeozems cover a large area of the region and contain a high level of organic carbon. These soils form the basis of agricultural production and forestry in the region. The silt content in the region's soils measured 45.6 ± 8.5%, ranging 19.1% to 57.6%. The north of the region is represented by soils with the lowest silt content (19–41%). In the center, in the west of the region, there is a zone with the highest silt content (53–58%). In other parts of the region, there are transitional levels of silt content in the soil. The clay content in the soils was 30.7 ± 13.8% and ranged 7.4% to 36.0%. The zone with the lowest clay content in soils has been formed in the north. The highest clay content in soils is typical for the southern part in the center of the region. The sand content in soils is highest in the northern part of the region, and the lowest in the southwestern and southern parts of the region.

We considered clay content in loose soil as the factor mostly influencing on hydraulic conductivity (filtration coefficient). We collected and analyzed some published experimental data about hydraulic conductivity relation with soil lithology and clay content in the form of grain size. Also we performed some theoretical modeling modifying well‐known formulas to include clay content in them. Experimental and calculated data showed quite good coincidence. Correlation between hydraulic conductivity and clay content seemed better, than correlation between hydraulic conductivity and resistivity. We created some approximation formulas relating filtration coefficient with clay content. Clay content in soil can be estimated on soil resistivity obtained from VES data interpretation and from groundwater salinity found from its resistivity. Then filtration coefficient is determined on clay content. Some examples of this method practical application at clean and oil contaminated areas are presented. We considered anomalies of decreasing filtration coefficient in contaminated zones not as a real effect, but as a good indicator of contamination, though in several publications there were some indications of hydro geological changes in soil properties due to oil contamination.

Carbamate systemic insecticides were applied to 5 soil mixtures under greenhouse conditions. They were Temik® (2-methyl-2-(methylthio) propionaldehyde O -(methylcar-bamoyl) oxime) and NIA 10242 (2,3-dihydro-2,2-dimethyl-7-.benzofuranyl methylcarbamate). Cotton plants growing in these soils took up the insecticides to varying extents as indicated by aphid bioassay. Of the variability in uptake, 99% was associated with soil clay content. Higher clay soils furnished the toxicant at a lower rate. During the period showing maximum mortality the effect of organic matter content became apparent. The rate at which bioassay mortalities declined increased with soil organic matter content. Temik was taken up more rapidly and persisted longer than NIA 10242. Phytotoxicity was severe in soils low in clay content, whereas, it was virtually nonexistent in those with high clay content. This fact indicated further the greater uptake of toxicant from soils low in clay content. More plant injury occurred with NIA 10242 than with Temik.

Eight soils from the Gulf of Kalloni in Lesvos Island, Greece, most of which were of low clay and low organic matter content, were used in a series of leaching experiments. The aim was to investigate the role of sewage sludge on Zn leaching and determine the soil properties that affect it. It was found that sludge addition at a low application rate (10 t ha−1) decreased Zn leaching significantly by 30%. From a regression analysis it was found that eluted Zn was reduced with increasing Fe oxides content, probably due to Zn adsorption onto them, and that Zn transport increased with clay content. This indicates that Zn leaching was facilitated by the downward movement of clay particles, which was also suggested by the erratic Zn breakthrough observed in many soils. This was further confirmed by the fact that colloid concentrations increased with clay content in the soils (R = 0.85, P < 0.05). The results show that the addition of sewage sludge to low organic matter and clay content soils at moderate application rates enhances soil organic carbon and increases metal retention capacity.

We considered clay content in loose soil as the factor mostly influencing on hydraulic conductivity (filtration coefficient). We collected and analyzed some published experimental data about hydraulic conductivity relation with soil lithology and clay content in the form of grain size. Also we performed some theoretical modeling modifying well-known formulas to include clay content in them. Experimental and calculated data showed quite good coincidence. Correlation between hydraulic conductivity and clay content seemed better, than correlation between hydraulic conductivity and resistivity. We created some approximation formulas relating filtration coefficient with clay content. Clay content in soil can be estimated on soil resistivity obtained from VES data interpretation and from groundwater salinity found from its resistivity. Then filtration coefficient is determined on clay content. Some examples of this method practical application at clean and oil contaminated areas are presented. We considered anomalies of decreasing filtration coefficient in contaminated zones not as a real effect, but as a good indicator of contamination, though in several publications there were some indications of hydro geological changes in soil properties due to oil contamination.

Improved estimation of soil clay content by the fusion of remote hyperspectral and proximal geophysical sensing

Installing shallow mole drainage in the soil is infl uenced by various factors, namely; the physical properties of soil and tools which are used. One of the physical properties of soil that infl uences the formation of the mole drainage is the clay content of soil. This study aimed to explore the condition of the mole drainage formed in paddy soil with different clay contents. The study was conducted in a laboratory scale using a soil bin, a model of mole plough, and soil which was kept homogeneous in the boxes. The experiment was conducted at the Laboratory for Energy andAgricultural Engineering, Agricultural Engineering Department, Universitas Gadjah Mada, Yogyakarta. Mole drainage was installed in 3 paddy soils with different clay content, namely; 13.12% (soil A; loam soil), 41.17% (soil B; clay soil) and 53.36% (soil C; clay soil). The study was conducted by analyzing the geometry of the mole drainage and observingthe soil deformation which occurred due to the formation of the mole drainage. The study showed that perfect mole drainages were installed in all of those three types of soil. The mole drainages were quite good and stable with little cracks. Based on the soil crack and fi ssuring of soil, the largest soil deformation has occurred in soil with the highestclay content and the smallest one in soil with the lowest clay content. The characteristics of those three installed mole drainages were almost the same, but they had different effect on the rate of lowering soil moisture content. Here, the mole drainage installed in loam soil is different from which of installed in clay soil. The mole drainage installed in theloam soil did not infl uence the rate of lowering soil moisture content. Contrary, the mole drainage installed in clay soil has effected to increase the rate of lowering soil moisture content.Keywords: Mole drainage, soil moisture content, clay content

Event Abstract Back to Event A spatial analysis of risk factors for sarcocystosis in South Australian sheep flocks, 2007-2017 Patrick L. Taggart1, Mark Stevenson2*, Simon Firestone2, Milton McAllister1 and Charle Caraguel1 1 School of Animal and Veterinary Sciences, Faculty of Sciences, University of Adelaide, Australia 2 Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Australia Cat-borne parasites and their associated diseases have substantial impacts on human, livestock, and wildlife health worldwide. Despite this, large and detailed data sets that allow researchers to study broad-scale trends in the ecology of cat-borne diseases are either difficult to obtain or non-existent. In sheep (Ovis aries), one cat-borne parasite that is easily detected at slaughter is macroscopic sarcocystosis. This was an analysis of factors influencing the geographic distribution of sarcocystosis among sheep farms in South Australia. Data were obtained from two slaughterhouses which processed 3,865,608 sheep from 4,204 farms across 385,468 km2 of South Australia’s land mass for the period 2007 to 2017. A Poisson point process model was developed to quantify environmental characteristics associated with higher densities of sarcocystosis-positive farms. Sarcocystosis-positive farms were concentrated on Kangaroo Island (located a short distance from the South Australian mainland) and the density of sarcocystosis-positive farms increased in areas with acid soils and soils with relatively high clay content. Unit increases in soil pH decreased the intensity of sarcocystosis-positive farms by a factor of 0.86 (95% CI 0.78 to 0.95). Where soil clay content was ≥16.5% sarcocystosis-positive farm density was increased by a factor of 1.45 (95% CI 1.10 to 1.92) compared with farms in areas where soil clay content was <14.5%. The density of sarcocystosis-positive farms on Kangaroo Island was 15.2 (95% CI 8.04 to 28.9) times greater than the density of sarcocystosis-positive farms located in the Adelaide Hills/Fleurieu Peninsula. Our analyses show a marked heterogeneous distribution of macroscopic ovine sarcocystosis across South Australia with a clear hotspot on Kangaroo Island. Since the density of feral cats on Kangaroo Island is relatively high we hypothesize that region in this analysis was confounded by, and acted as a proxy for, cat density. Whilst management of soil pH and/or soil clay content provide some opportunity to reduce the risk of sarcocystosis in South Australian sheep, we propose that control of feral cat populations is the most feasible and sustainable approach to sarcocystosis control. Acknowledgements Primary Industries and Regions, South Australia Biosecurity, Elise Matthews, Celia Dickason, Adrian Baddeley, Rolf Turner, and Tilman Davies. References Taggart, P., Stevenson, M., Firestone, S., McAllister, M., Caraguel, C., 2019. Spatial analysis of a cat-borne disease reveals that soil ph and clay content are risk factors for sarcocystosis in sheep. Frontiers in Veterinary Science. DOI: 10.3389/fvets.2019.00127. Keywords: Poisson point process modelling, Feral cats, surveillance, Spatial Epidemiology, Sarcocystosis Conference: GeoVet 2019. Novel spatio-temporal approaches in the era of Big Data, Davis, United States, 8 Oct - 10 Oct, 2019. Presentation Type: Regular oral presentation Topic: Spatial methods for environmental & exposure epidemiology and climate change Citation: Taggart PL, Stevenson M, Firestone S, McAllister M and Caraguel C (2019). A spatial analysis of risk factors for sarcocystosis in South Australian sheep flocks, 2007-2017. Front. Vet. Sci. Conference Abstract: GeoVet 2019. Novel spatio-temporal approaches in the era of Big Data. doi: 10.3389/conf.fvets.2019.05.00060 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 01 Jun 2019; Published Online: 27 Sep 2019. * Correspondence: Prof. Mark Stevenson, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria, VIC 3010, Australia, mark.stevenson1@unimelb.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Patrick L Taggart Mark Stevenson Simon Firestone Milton McAllister Charle Caraguel Google Patrick L Taggart Mark Stevenson Simon Firestone Milton McAllister Charle Caraguel Google Scholar Patrick L Taggart Mark Stevenson Simon Firestone Milton McAllister Charle Caraguel PubMed Patrick L Taggart Mark Stevenson Simon Firestone Milton McAllister Charle Caraguel Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Quantitative study of the spatial distribution of soil clay content is crucial to soil microecological research, soil physical and chemical properties, and agricultural and environmental management. In this article, the distribution of clay content within a 1-m soil body was selected as the study object. The soil clay content was measured with a laser grain-size analyzer and classified into indicator data. The spatial variability of the data was then analyzed by indicator variogram and transiogram. The results of the indicator variogram showed that the spatial distribution of clay content in a horizontal direction is highly random. However, the results of the transiogram of clay content exhibited obvious spatial juxtapositional tendencies both vertically and horizontally. Subsequently, sequential indicator simulation (SIS) and transition probability indicator simulation (TPROGS) were applied to create conditional realizations of the 1-m soil body. Finally, the realizations were validated by reproduction of a histogram, connectivity, as well as mean absolute error of prediction. The results indicated that the major textural classes were overestimated, whereas the minor classes were underestimated in the SIS-generated histogram, whereas all classes were well reproduced in the TPROGS. In addition, compared with the measured data, the connectivity of SIS realizations was significantly reduced, whereas the connectivity of TPROGS was coherent with measured data, which indicated that the crucial spatial characteristics, which were neglected by SIS, can be captured by TPROGS, even if the accuracy of prediction is similar. Therefore, the TPROGS method is a suitable method for characterizing the distribution of clay content in soil. The results may provide useful information for soil research. © 2009 Lippincott Williams & Wilkins.

Agricultural soils have tremendous potential to sequester soil organic carbon (SOC) and mitigate global climate change. However, agricultural land use has a profound impact on SOC dynamics, and few studies have explored how agricultural land use combined with soil conditions affect SOC changes throughout the soil profile. Based on a paired soil resampling campaign in the 1980s and 2010s, this study investigated the SOC changes of the soil profile caused by agricultural land use and the correlations with parent material and topography across the Chengdu Plain of China. The results showed that the SOC content increased by 3.78gC/kg in the topsoil (0-20cm), but decreased in the 20-40cm and 40-60cm soil layers by 0.90 and 1.26gC/kg respectively. SOC increases in topsoil were observed for all types of agricultural land. Afforestation on former agricultural land also caused SOC decreases in the 20-60cm soil layers, while SOC decreases only occurred in the 40-60cm soil layer for agricultural land using a traditional crop rotation (i.e. traditional rice-wheat/rapeseed rotation) and with rice-vegetable rotations converted from the traditional rotations. For each agricultural land use, SOC decreases in deep soils only occurred in high relief areas and in soils formed from Q4 (Quaternary Holocene) grey-brown alluvium and Q4 grey alluvium that had a relatively low soil bulk density and clay content. The results indicated that SOC change caused by agricultural land use was depth dependent and that the effects of agricultural land use on soil profile SOC dynamics varied with soil characteristics and topography. Subsoil SOC decreases were more likely to occur in high relief areas and in soils with low soil bulk density and low clay content.

Water availability is one of the determinants of productivity of rainfed lowland rice (Oryza sativa L.). Quantifying water losses from a paddy field, such as deep percolation and lateral seepage, assists estimation of water availability to the rice crop and development of appropriate water management in the lowlands. The main objective of this study was to evaluate paddy water availability and productivity across various soils in Northeast Thailand. The daily rate of downward water flow from standing water in the field (D) varied between 0 and 3 mm day-1 from clayey to sandy soils when the standing water was connected to groundwater table. However, when the standing water was separated from groundwater table, D increased up to 5 mm day-1 on soils with very low clay content in the topsoil. Daily net lateral water flow from the field (L) averaged over the season varied between 5 and 24 mm day-1 for the outflow and between 3 and 16 mm day-1 for the inflow. Both the inflow and outflow tended to be associated negatively with the soil clay content. The seasonal water loss through D plus L during the growing season in the lowlands was also negatively related to the soil clay content. The yield of a major rainfed lowland rice cultivar in Northeast Thailand (KDML105) varied from 2 to 4 t ha-1 across the region, and the water productivity (the ratio of grain yield to cumulative rainfall from transplanting/seedling establishment to maturity) ranged from 3 to 9 kg ha-1 mm-1. High clay soils could provide good standing water until late in the growing season, so the high production efficiency was measured on such soils.

Soil electrical conductivity (ECa) is a soil quality indicator associated to attributes interesting to site-specific soil management such as soil moisture and texture. Soil ECa provides information that helps guide soil management decisions, so we performed spatial evaluation of soil moisture in two experimental fields in two consecutive years and modeled its influence on soil ECa. Soil ECa, moisture and clay content were evaluated by statistical, geostatistical and regression analyses. Semivariogram models, adjusted for soil moisture, had strong spatial dependence, but the relationship between soil moisture and soil ECa was obtained only in one of the experimental fields, where soil moisture and clay content range was higher. In this same field, coefficients of determinations between soil moisture and clay content were above 0.70. In the second field, the low soil moisture and clay content range explain the absence of a relationship between soil ECa and soil moisture. Data repetition over the years, suggested that ECa is a qualitative indicator in areas with high spatial variability in soil texture.

Understanding the association between soil organic carbon (SOC) and texture under different climatic conditions is important for assessing the effects of future climate changes on SOC stocks. In this study, we conducted a climatic gradient experiment covering three climate types (humid, sub-humid, and semi-arid) with a steep rainfall ranging from 345 to 910 mm, and specifically determined SOC dynamics, clay content, and vegetation and soil characteristics. The results showed that, from semi-arid to humid regions, SOC stocks, SOC, and clay content increased synchronously and were closely related in layers of depths of both 0–10 and 10–20 cm. In contrast, under similar climatic conditions, SOC dynamics were mainly affected by vegetation and soil characteristics, especially total nitrogen and total phosphorus dynamics, but not the soil clay content. Therefore, these results suggest that the relationship between SOC stocks and clay content depended on scale sizes. Specifically, on a larger scale with different climatic gradients, the climate may partly determine the changes in SOC and clay dynamics, whereas, at a smaller scale where climate type does not vary considerably, the changes in SOC stocks and clay content may be related to vegetation diversity and soil nutrient dynamics. These results may contribute to future model development and the projection of changes in soil carbon storage.

Visible and near‐infrared reflectance (Vis‐NIR) spectroscopy is considered a promising tool for the estimation of soil properties. Soil clay content and soil organic matter (SOM) are main components affecting soil spectra. Accurate assessment of clay content and SOM is essential before achieving accurate prediction for other soil properties. Selecting the proper spectral transformation technique and optimal calibration method are important processes to improve model performance. In this study, a total of 240 soil samples were collected from the main area of winter wheat (Triticum aestivum L.) fields in the Southwest region of Shanxi province, northern China. Six spectral pre‐treatments and three multivariate methods were utilized to realize the estimation of clay content and SOM. Finally, the important spectral wavelengths were identified as 440, 762, 1,150, 1,410, 1,460, 1,860, 1,900, 2,250, 2,400 nm for clay content and 410, 450, 550, 625, 780, 850, 1,410, 1,670, 1,730, 1,860, 1,910, 1,960, 2,250 nm for SOM. Specifically, the wavelengths around 440 (450), 1,900 (1,910) nm and wavebands of 1,410, 1,860, and 2,250 nm were highly related to both clay content and SOM. The optimal prediction was obtained when multiple linear regression (MLR) was combined with standard normal variate (SNV) pre‐processing (R2 = .714, RMSE = 3.982, RPD = 1.584) for clay content and multiplicative scatter correction (MSC) pre‐processing (R2 = .856, RMSE = 2.994, RPD = 2.443) for SOM. This study implied that spectral transformation had an evident effect on spectral curves shape, correlation, and model performance. The choice of pre‐processing transformation should depend on the multivariate technique which has a determined ability to improve the model accuracy.