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In the present study, we examined fine root production and soil available nutrients (N, P and K) across different soil depths in rubber monoculture and rubber–Flemingia macrophylla agroforestry of different stand ages. We used the ingrowth cores method and sampled 360 soil cores over four growth intervals, representing one year of growth for the present study. The results showed that root production and macronutrient concentrations generally decreased with increasing soil depth. Total fine root production was comparatively high in the youngest stand age (12 years) rubber monoculture; a similar trend was observed for the soil available P and K, but available N was greater in older than younger stand ages. Root growth and soil available P and K were all lower in the agroforestry system than the monoculture. Significant differences in fine root production with stand ages, management system and seasons suggest that fine root responses to the soil available nutrients are vital to understanding the precise response of above- and belowground biomass to environmental changes.

The study is aimed at identifying patterns in distribution of pollutants in the elementary landscape-geochemical systems (ELGS) of the temperate zone. The study used 137Cs as a tracer, which allows a highly detailed analysis of the nature of the heterogeneity of secondary migration in the toposequence: summit—slope—closing depression, treated as the elementary landscape-geochemical system. The study site was located in the Bryansk region in the Chernobyl abandoned area with an initial level of 137Cs contamination exceeding 1480 kBq/m2 (40 Ci/km2). An original technique of repeated 137Cs measurements along cross-sections accompanied by topographic survey and soil cores sampling has been applied. The obtained results showed a complete absence of constant increase of 137Cs concentration downslope but revealed a steady regular variability of 137Cs activity of a cyclical type. Given uniformity of the initial 137Cs fallout within a small-sized plot, variation of 137Cs due to its secondary distribution in ELGS was 2–2.7-fold according to field gamma-spectrometry data which corresponded to the radionuclide contamination density of the top 20-cm layer of the soil containing 96–99% of the total radionuclide amount (correlation between the parameters equaled to r0.01 = 0.782, n = 20). A specifically regular structure obviously formed under the set of radionuclide water migration processes seems to be inherent in all systems of the studied type. The results obtained are believed to be of both theoretical and practical importance, since they can contribute to making decisions on the precise monitoring of zones of technogenic accumulation, as well as solving fundamental problems of soil formation and its restoration after technogenic pollution.

A total of 344 soil cores were taken in annually cropped fields of Alberta, Saskatchewan, Manitoba, and Ontario from 2011 to 2013 in areas where the field shapes, or obstacles within fields, required the driving pattern of farm operations to overlap. Soil nitrate-N concentrations in overlapping areas were 60% greater, soil Olsen-P concentrations were 23% greater, and pH was 0.5 units greater at 0–15 cm depth compared with non-overlapping areas, suggesting smaller nutrient use efficiency and potential for greater nutrient loss.

Controlled‐release fertilizers (CRFs) have the potential to deliver crop production and environmental benefits through better control of applied nitrogen (N) in cropping systems. Whereas N release from CRFs can be impacted by several factors, there has been a widely held view that soil water has little effect on N release from polymer‐coated CRFs. Past research has often studied the soil water effect as a function of soil water content. This limits the transferability of results. In this study we measured N release from a polymer‐coated urea (PCU) and a polymer‐sulfur–coated urea (PSCU) using undisturbed soil cores at set matric potentials. Soil matric potential had a significant effect on N release from PCU. Release at −1,000 kPa was delayed by up to 30 d compared with −10 kPa. Optical stereo microscopy clarified that this was linked to differences in the rate of water absorption. Theoretical considerations demonstrate that these relatively large differences could not be explained by the effect of soil matric potential on vapor flow. It is possible that soil matric potential interacted with the properties of the coating to change its permeability or the involvement of liquid flow. The effect of soil water on N release from PSCU was less clear. The magnitude of the soil water effect is, therefore, product‐specific and dependent on coating properties. The soil matric potential provided a consistent description of release patterns between soils with contrasting soil water retention characteristics. Soil water effects should hence be studied as a function of soil matric potential.

The 15N gas-flux method allows for the quantification of N2 flux and tracing soil N transformations. An important requirement for this method is a homogeneous distribution of the 15N tracer added to soil. This is usually achieved through soil homogenization and admixture of the 15N tracer solution or multipoint injection of tracer solution to intact soil. Both methods may create artefacts. We aimed at comparing the N2 flux determined by the gas-flux method using both tracer distribution approaches. Soil incubation experiments with silt loam soil using (i) intact soil cores injected with 15N label solution, (ii) homogenized soil with injected label solution, and (iii) homogenized soil with admixture of label solution were performed. Intact soil cores with injected 15N tracer solution show a larger variability of the results. Homogenized soil shows better agreement between repetitions, but significant differences in 15N enrichment measured in soil nitrate and in emitted gases were observed. For intact soil, the larger variability of measured values results rather from natural diversity of non-homogenized soil cores than from inhomogeneous label distribution. Generally, comparison of the results of intact cores and homogenized soil did not reveal statistically significant differences in N2 flux determination. In both cases, a pronounced dominance of N2 flux over N2O flux was noted. It can be concluded that both methods showed close agreement, and homogenized soil is not necessarily characterized by more homogenous 15N label distribution.

Poly- and perfluoroalkyl substances (PFASs) derived from aqueous film-forming foam (AFFF) are increasingly recognized as groundwater contaminants, though the composition and distribution of AFFF-derived PFASs associated with soils and subsurface sediments remain largely unknown. This is particularly true for zwitterionic and cationic PFASs, which may be incompletely extracted from subsurface solids by analytical methods developed for anionic PFASs. Therefore, a method involving sequential basic and acidic methanol extractions was developed and evaluated for recovery of anionic, cationic, and zwitterionic PFASs from field-collected, AFFF-impacted soils. The method was validated by spike-recovery experiments with equilibrated soil-water-AFFF and analytical standards. To determine the relative importance of PFASs lacking commercially available analytical standards, their concentrations were estimated by a novel semiquantitation approach. Total PFAS concentrations determined by semiquantitation were compared with concentrations determined by the total oxidizable precursor assay. Finally, the described method was applied to two soil cores from former fire-training areas in which cations and zwitterions were found to contribute up to 97% of the total PFAS mass. This result demonstrates the need for extraction and analysis methods, such as the ones presented here, that are capable of quantifying cationic and zwitterionic PFASs in AFFF-impacted source zone soils.

No information exists on the susceptibility of arbuscular mycorrhizal fungal (AMF) communities in Canadian prairie agriculture soils to climate change. An experiment was initiated in mid-May 2011 in which replicated soil cores were transplanted reciprocally from four cultivated prairie sites in Saskatchewan, Canada, representing different regional climatic zones ranging from semiarid to subhumid regional climates, such that replicated (n = 4) soil cores from each site were present at all sites. Field pea was grown in all cores and at harvest in early-September 2011; soil samples were collected to analyze the changes of AMF communities over the cropping season. A total of 82 operational taxonomic units belonging to eight AMF genera were identified using 18S rRNA gene pyrosequencing. When soils were transplanted to new environments, the relative abundance of AMF changed considerably. Typically, Shannon diversity declined when soil cores were transplanted to new environments. We present evidence that with the altered climatic conditions following transplantation of soil cores, the relative abundance of AMF was significantly altered, and some taxa were enhanced, suppressed, or disappeared in the home-away soils compared with home-site soils. This study implies that the future climate change effects on AMF may impact specific phylogenetic taxa differently, such that rare species or those with low abundance may increase or decrease with unknown consequences. Understanding the potential responses of AMF communities to soil–climate interactions is important when considering the impacts of climate change on soil microbial communities.

Continued reliance on chemical methods for controlling annual bluegrass has resulted in many populations evolving resistance to PRE and POST herbicides, particularly in warm-season turfgrass species such as zoysiagrass. Soil seedbank management is critically important when managing herbicide-resistant weeds. Fraise mowing (also spelled fraze, frase, and fraize) is a new turfgrass cultivation practice designed to remove aboveground biomass while allowing turf to regrow vegetatively. We hypothesized that this process would remove annual bluegrass seed and therefore be a mechanical means of controlling annual bluegrass in turfgrass. Zoysiagrass field plots were fraise-mowed in June 2015 only, June 2016 only, June 2015 and June 2016, or left untreated. The fraise mower was configured to remove the uppermost 25 mm of plot surface (i.e., 15-mm verdure and 10-mm soil). Annual bluegrass infestation was quantified in April following fraise mowing via grid count. Soil cores (10.8 cm diameter) were extracted from each plot after grid count data were collected to assess effects of fraise mowing on the soil seedbank. Moreover, replicated subsamples (7.6 L) of debris generated during fraise mowing were collected to better understand weed seed content removed during the fraise mowing process. Fraise mowing in June offered a slight reduction (24%) in annual bluegrass cover the following April. Whereas 28% of the seed in fraise-mowing debris consisted of annual bluegrass, there was no difference in the quantity of annual bluegrass seed remaining in the soil seedbank among fraise-mowed and non–fraise-mowed plots. Although fraise mowing may help to temporarily reduce existing annual bluegrass infestations via mechanical removal, the frequency and depth we studied did not effectively reduce the seedbank. Fraise mowing is a useful tool for providing mechanical suppression of annual bluegrass but it is not a replacement for properly timed herbicide applications.Nomenclature: Annual bluegrass (Poa annua L.); zoysiagrass (Zoysia japonica Steud.)

Soil bulk density and moisture content are dynamic properties that vary with changes in soil and field conditions and have many agricultural, hydrological and environmental implications. The main objective of this study was to compare between a soil core sampling method (core) and the CPN MC-3 EliteTM nuclear gauge method (radiation) for measuring bulk density (ρB) and volumetric moisture content (θv) in a clay loam soil. Soil ρB and θv measurements were determined using the core and radiation methods at 0 - 10 and 10 - 20 cm soil depths. The mean values of soil ρB obtained using the core method (1.454, 1.492 g·cm−3) were greater than those obtained using the radiation method (1.343, 1.476 g·cm−3) at the 0 - 10 and 10 - 20 cm depths, respectively. Mean ρB and θv values averaged across both depths (referred to as the 0 - 20 cm depth) measured by the core method were 4.47% and 22.74% greater, respectively, than those obtained by the radiation method. The coefficients of variation (CV) of soil ρB values measured by the core method were lower than the CV values of those measured by the radiation method at both depths; however, the CV’s of ρB values for both methods were larger at the 0 - 10 cm depth than those measured at the 10 - 20 cm depth. Similarly, the CV values of soil θv values measured by the core method were lower than the CV values of those measured by the radiation method at both depths. There were significant differences between two methods in terms of ρB and θv, with the core method generating greater values than the radiation method at the 0 - 20 cm depth. These discrepancies between the two methods could have resulted from soil compaction and soil disturbance caused by the core and radiation techniques, respectively, as well as by other sources of error. Nevertheless, the core sampling method is considered the most common one for measuring ρB for many agricultural, hydrological and environmental studies in most soils.

Abiotic reduction of contaminants in iron-based laboratory model systems has been studied extensively, but the resulting understanding is not sufficient to allow prediction of reaction rates under ...

Our analyses revealed the spatial variability of the vertical distribution of fallout radiocesium measured in small cylindrical soil cores taken in a non-disturbed paddy field contaminated by the F...

Agricultural grass cultivars bred for increased forage yield commonly have extensive root systems. As roots are an important input of organic matter into the soil, it follows that such cultivars could lead to important increases in soil organic carbon (SOC), but this, and the mechanisms involved, are poorly understood with little empirical field evidence. We assessed the effect of two cultivars, Lolium perenne L. cv. ‘AberMagic’ and L. perenne L. × Festuca pratensis Huds. cv. ‘Prior’, in comparison with mixed-species permanent pasture (‘Pasture’) in a field experiment on temperate alluvial soil in the southwest UK. Root and SOC stocks, and specific plant-derived lipids as mechanistic biomarkers for shoot and root inputs of C, were measured on intact 1-m volumetric soil cores collected on four dates in 2013-2015. Total grass yields were greater for both grass cultivars (40-43 Mg ha–1) than Pasture (39 Mg ha–1), and by 2015 root stocks in the upper 0.1 m were significantly greater by more than 4.7 Mg ha–1. At 0.1-0.3 m depth, SOC stocks (per 0.1-m depth) were significantly greater under the two grass cultivars (24-50 Mg ha–1) compared to Pasture (18-32 Mg ha–1). In the full 1-m profile, mean SOC stocks were 137, 133 and 110 Mg ha–1 for AberMagic, Prior and Pasture, respectively, matching root biomass distribution. Odd-chain n-alkane concentrations were significantly greater for shoots than roots (274 vs. 64 mg kg–1, respectively), and roots had significantly greater concentrations than shoots of even-chain hydroxy fatty acids (1829 vs. 305 mg kg–1, respectively) and diacids (317 vs. 93 mg kg–1, respectively). This confirmed lipids as candidate biomarkers for distinguishing shoot and root inputs into the soil, with the latter being the dominant source of SOC. Based on the observations of increased forage yield and SOC stock, high-yielding forage grass cultivars can contribute to future strategies for climate-smart agriculture in grassland-dominated temperate regions.

This research was funded by the Ministry of Business, Innovation and Employment's Endeavour Fund, through the Manaaki Whenua-led `Next Generation S-map' research programme, C09 x1612. We would like to thank from Manaaki Whenua - Landcare Research John Dando for the laboratory physical determinations, Veronica Penny for collecting soil cores and samples, and John Drewry for reviewing the manuscript. Mathieu Sellier from Civil Mechanical of the University of Canterbury (New Zealand) is also thanks for reviewing the manuscript., Hydraulic parameters define the water retention, theta( psi), and the unsaturated hydraulic conductivity, K(theta), functions. These functions are usually obtained by fitting experimental data using inverse modelling. The drawback of inverting the hydraulic parameters is that they suffer from non-uniqueness and the optimal hydraulic parameters may not be physical. To reduce the non-uniqueness, it is necessary to invert the hydraulic parameters simultaneously from observations of theta( psi) and K(theta), and ensure the measurements cover the full range of theta from saturated to oven dry. The challenge of using bimodal theta(psi) and K(theta) compared to unimodal functions is that it requires double the number of parameters, one set for the matrix and another set for the macropore domain. The objective of this paper is to address this shortcoming by deriving a procedure to reduce the number of parameters to be optimized to obtain a unique physical set of bimodal soil Kosugi hydraulic parameters from inverse modelling. To achieve this, we (1) derive residual volumetric soil water content from the Kosugi standard deviation parameter of the soil matrix, (2) derive macropore hydraulic parameters from the water pressure head threshold between macropore and matrix flow, and (3) dynamically constrain the Kosugi hydraulic parameters of the soil matrix. The procedure successfully reduces the number of optimized hydraulic parameters and dynamically constrains the hydraulic parameters without compromising the fit of the theta(psi) and K(theta) functions, and the derived hydraulic parameters are more physical. The robustness of the methodology is demonstrated by deriving the hydraulic parameters exclusively from theta(psi) and Ks data, enabling satisfactory prediction of K(theta) even when no additional K(theta) data are available., Ministry of Business, Innovation and Employment's Endeavour Fund C09 x1612

A long-term experiment was conducted in soils across a decreasing pH gradient (7.0, 6.3, 5.7, 4.9 and 4.3). Intact soil cores across the pH gradient were sampled and incubation experiments were use...

The vertical distribution and migration behavior of 239+240Pu in a soil core in northern Loess Plateau in Shaanxi Province was investigated. The results showed that the 239+240Pu activity concentration was in the range of 0.02–0.75 mBq/g. The measured atom ratios of 240Pu/239Pu in the soil profile varied from 0.179 to 0.201 and were consistent with the typical global fallout. The inventory of 239+240Pu was 66 Bq/m2 in the sampling site and the proportion of Pu in the first 10 cm top layer accounted for around 75%. The apparent convection velocity and effective dispersion coefficient were 0.19 cm/year and 0.12 cm2/year by the convection dispersion equation model, respectively. Further investigation is still highly required to clarify the dominant factors that control Pu migration.

Autoclaved-citrate extractable (ACE) soil protein is included in some soil health assessments as a biological indicator. Furthermore, soil protein contents may be related to the ability of a soil to make nitrogen (N) available for plants by mineralization. The main objective of this study was to evaluate the correlation between ACE protein and potential net N mineralization in undisturbed soil cores from 57 fields in California under annual crops. Total N in the soils ranged from 0.65 to 12.5 g kg⁻¹, and the sites represented eight Soil Taxonomy orders. Soil ACE protein concentrations ranged from 1.0 to 45.2 g kg⁻¹ soil. Although the correlation between ACE protein and potential net N mineralization was positive, ACE protein explained only 21% of the variability in potential net N mineralization across all sites, which was less than total N. Under the assumption that proteins contain 16% N, ACE protein-N accounted for 28% of total N across all sites. However, in some soils with a high total N content, ACE protein accounted for up to 67% of total N. Because autoclaving is expected to denature some proteins, these values seem very high and are likely caused by the interference of coextracted humic substances. Our results do not suggest that ACE protein is a better predictor of potential net N mineralization than total soil N, which may be at least partly due to an apparent interference of coextracted humic substances with the protein assay.

Three soil core samples were collected from a forest located about 1.1 km south of the Fukushima Daiichi Nuclear Power Plant (FDNPP) boundary in 2017, and the vertical profiles of 129I from the FDNPP accident were determined by the combination of TMAH (tetramethyl ammonium hydroxide) extraction and ICP-MS/MS analysis. The humus layer above the soil layer was heavily contaminated with 134Cs (1983–5985 Bq g−1) and 137Cs (1947–5902 Bq g−1) (decay-corrected to March 11, 2011). The 129I activity concentrations decreased sharply with the soil depth, from 1894 to 34.1, from 9384 to 78.9, and from 2536 to 51.3 mBq kg−1, for the three sites. Downward migration of 129I was slightly faster than the one of 134Cs. In addition, the cumulative 129I inventories were observed to be 43.4 ± 1.0, 71.7 ± 1.8, and 56.5 ± 1.8 Bq m−2, respectively. Subsequently, the cumulative 131I inventories were estimated to be 1.76 ± 0.06, 2.90 ± 0.11, and 2.28 ± 0.10 GBq m−2 (decay-corrected to March 11, 2011), respectively. Finally, the total atmospheric deposition of 129I on the land of Japan due to the FDNPP accident was estimated to be around 1.09–1.71 kg (7.11–11.2 GBq).

espanolLa region de Yalahau al norte de Quintana Roo, Mexico, contiene abundantes humedales de agua dulce y una historia de ocupacion Maya que abarca casi 3000 anos. Los mayores niveles de poblacion regional ocurrieron durante el periodo Preclasico tardio, del 100 AC al 350/450 DC. Los Mayas construyeron alineamientos rocosos cruzando los pantanos, y se ha hipotetizado que estas caracteristicas funcionaron para atrapar suelos y agua para la produccion de alimento y para el uso de recursos biologicos como el perifiton. Los estudios paleoambientales de un humedal de la porcion oriental de la region sugieren que la ocupacion de la region de Yalahau y la manipulacion de los humedales, corresponden con un periodo cuando el manto freatico fue menor que en tiempos modernos, creando ecosistemas de humedal que eran mas productivos para el cultivo. Este trabajo presenta resultados que aplican este modelo a escala regional (en humedales en otras partes de la region). Treinta pequenos nucleos de suelo fueron colectados de 12 humedales a lo largo de la region. Para este Proyecto, 5 nucleos de 4 humedales fueron seleccionados para los analisis que incluyen micromorfologia y fechamiento por radiocarbono. Las laminas delgadas, estudiadas bajo el microscopio petrografico, fueron usadas para identificar los varios tipos de caracteristicas presentes en los nucleos, incluyendo carbonatos, materia organica, conchas, pirita, yeso y espacio poroso. En cada nucleo, distinguimos una unidad superior dominada por carbonato micritico biogenico y una unidad inferior caracterizada por una variedad de caracteristicas de suelo unicas, como cristales espariticos de calcita, pirita, yeso y propiedades gleycas. Basado en esto, se sugiere que mientras que los procesos formadores del suelo moderno son claramente uniformes a lo largo de la region y controlados por la inundacion anual regular (~7 meses de >1 m de profundidad de inundacion cada ano), en el pasado (periodo Preclasico), la inundacion era menos regular y los ambientes de humedal fueron mas pantanosos y variados. Ademas, se sugiere que las depresiones del Preclasico encontradas por los Mayas, fueron un recurso agricola de calidad que permitio el florecimiento de la region durante el Preclasico tardio. Sin embargo, como la inundacion se volvio mas regular al final del periodo Preclasico, la region fue abandonada, solo para ser re-ocupada en el Postclasico tardio, cuando los humedales fueron explotados para recursos acuaticos, mas que para la agricultura. EnglishThe Yalahau region of northern Quintana Roo, Mexico, contains abundant freshwater wetlands and a history of Maya occupation that spans nearly 3000 years. The highest regional population levels occurred during the Late Preclassic period, from ca. 100 BC to AD 350/450. The Maya constructed rock alignments crossing wetland swales, and these have been hypothesized as features used to trap soil and water for production of food and useful biological resources such as periphyton. Paleoenvironmental studies from a wetland in the eastern part of the region suggested that occupation of the Yalahau region, and manipulation of the wetlands, corresponded to a period when the water table was lower than in modern times, creating wetland ecosystems that were most productive for cultivation. This paper presents results that apply this model at the regional scale (in wetlands in other parts of the region). Thirty short soil cores were collected from 12 wetlands across the region. For this project, 5 cores from 4 wetlands were selected for analyses including micromorphology and radiocarbon dating. Thin sections studied under petrographic microscope were used to identify the various types of features present in the core sequences including carbonates, organic matter, shell, pyrite, gypsum, and pore space. In each core, it was possible to distinguish an upper unit dominated by biogenic-micritic carbonate and a lower unit characterized by a variety of unique soil features such as sparitic calcite crystals, pyrite, gypsum, and gleyic properties. Based on this, it is suggested that while modern soil forming processes are fairly uniform across the region and controlled by regular annual flooding (~7 months of >1m deep flooding each year), in the past (Preclassic period), flooding was less regular and wetland environments were more swampy and varied. Furthermore, it is suggested that the Preclassic depressions encountered by the Maya were a prime agricultural resource that allowed the region to flourish during the Late Preclassic period. However, as flooding became more regular at the end of the Preclassic period, the region was abandoned, only to be reoccupied in the Late Postclassic when wetlands were exploited for aquatic resources rather than for agriculture.

Cement soil mixing piles are an effective treatment method for marine soft clay. To investigate the static and dynamic characteristics of the composite soil with cemented soil core, a serie...

Root zone soil moisture is an important component in water cycling through the soil-plant-atmosphere continuum. However, its measurement in the field remains a challenge, especially non-invasively and repeatedly. Here, we developed a new method that uses ground-penetrating radar (GPR) to quantify root zone soil moisture. Coarse roots were chosen as reflectors to collect GPR radargrams. An automatic hyperbola detection algorithm identified coarse root reflections in GPR radargrams and determined the velocity of GPR wave, which then was used to calculate the average soil water content of a soil profile (ASWC) and soil water content in a depth interval (ISWC). In total, GPR reflection data of 55 root samples from three computer simulation scenarios and two field experiments in sandy shrubland, one burying roots at known depths and the other under the undisturbed condition, were used to evaluate the proposed method. Both the simulated and the field collected data demonstrated the effectiveness of the proposed method for measuring root zone soil moisture with high accuracy. Even in the two field experiments, the root-mean-square errors of the estimated ASWC and ISWC relative to measurements from soil cores were as low as 0.003 and 0.012 m3·m−3, respectively. The proposed method offers a new way of quantifying root zone soil moisture non-invasively that allows repeated measurements. This study expands the application of GPR in root and soil study and enhances our ability to monitor plant-soil-water interactions.

Implementation of winter cover crops (CC) is a conservation practice aimed at improving soil health and increasing water infiltration. Reduced tillage (e.g., no-till), another, more common conservation practice, shares these aims. While the literature concerning the main effects of CC and reduced tillage is rich, the additive effects of CC and reduced tillage are unclear and understudied—specifically, the adoption of reduced tillage long before (20+ years) CC implementation, which is common in the last half-century. This study assessed two of the potential short-term effects of CC when added in a long-term no-till system: reduction of soil compaction (SC) and addition of soil total carbon (STC). Four field plots in northeast Mississippi were planted with CC while two were utilized as controls having no CC. All plots were under no-till for the last 20+ years. Soil penetration resistance measurements (SC) and soil cores were collected in April of 2017, following two years of CC implementation, from 20 semirandomly selected locations in each plot. Model comparisons were used to explore variation in SC and STC between CC and control plots, and the contributions of covariates to the observed variation. Results of the selected models (model with highest Akaike9s weight) indicated there was no difference in SC between CC and control plots; however, slight variation in STC did exist between the two treatment levels (d ± 95% CI = 0.46 ± 0.39, p