Institute for Soil Sciences

University of California 1 The senior author is indebted to R. H. Allee, Director of the International Institute of Agricultural Sciences at Turrialba, Costa Rica, for arranging the author's sojourn at the Institute, and to N. C. Ives and S. Bonilla for assistance in collecting soil samples and conducting experiments.

Abstract Soil, through its various functions, plays a vital role in the Earth's ecosystems and provides multiple ecosystem services to humanity. Pedotransfer functions (PTFs) are simple to complex knowledge rules that relate available soil information to soil properties and variables that are needed to parameterize soil processes. In this paper, we review the existing PTFs and document the new generation of PTFs developed in the different disciplines of Earth system science. To meet the methodological challenges for a successful application in Earth system modeling, we emphasize that PTF development has to go hand in hand with suitable extrapolation and upscaling techniques such that the PTFs correctly represent the spatial heterogeneity of soils. PTFs should encompass the variability of the estimated soil property or process, in such a way that the estimation of parameters allows for validation and can also confidently provide for extrapolation and upscaling purposes capturing the spatial variation in soils. Most actively pursued recent developments are related to parameterizations of solute transport, heat exchange, soil respiration, and organic carbon content, root density, and vegetation water uptake. Further challenges are to be addressed in parameterization of soil erosivity and land use change impacts at multiple scales. We argue that a comprehensive set of PTFs can be applied throughout a wide range of disciplines of Earth system science, with emphasis on land surface models. Novel sensing techniques provide a true breakthrough for this, yet further improvements are necessary for methods to deal with uncertainty and to validate applications at global scale.

Soil contamination is one of the greatest concerns among the threats to soil resources in Europe and globally. Despite of its importance there was only very course scale (1/5000km(2)) data available on soil heavy metal concentrations prior to the LUCAS topsoil survey, which had a sampling density of 200km(2). Based on the results of the LUCAS sampling and auxiliary information detailed and up-to-date maps of heavy metals (As, Cd, Cr, Cu, Hg, Pb, Zn, Sb, Co and Ni) in the topsoil of the European Union were produced. Using the maps of heavy metal concentration in topsoil we made a spatial prediction of areas where local assessment is suggested to monitor and eventually control the potential threat from heavy metals. Most of the examined elements remain under the corresponding threshold values in the majority of the land of the EU. However, one or more of the elements exceed the applied threshold concentration on 1.2Mkm(2), which is 28.3% of the total surface area of the EU. While natural backgrounds might be the reason for high concentrations on large proportion of the affected soils, historical and recent industrial and mining areas show elevated concentrations (predominantly of As, Cd, Pb and Hg) too, indicating the magnitude of anthropogenic effect on soil quality in Europe.

Abstract Indirect estimation of soil water retention from easily measurable data of soil surveys is needed to extend the applicability of hydrological models. Artificial neural networks (ANN) are becoming a common tool for modeling complex “input‐output” dependencies. The objective of this work was to compare the accuracy of ANN and statistical regressions for water retention estimation from texture and bulk density. We used data on water contents at eight matric potentials for 130 Haplustoll and 100 Aquic Ustoll soil samples. Although the differences were not always statistically significant, ANN predicted water contents at selected matric potentials better than regression. The performances of ANN and regressions were comparable when van Genuchten's equation was fitted to data for each sample, and parameters of this equation were estimated from texture and bulk density. The precision of parameter estimations was lower than the precision of estimating water contents at a given soil water potential with both ANN and regressions. Grouping samples by horizons improved the precision of the estimates, especially in subsoil. Because they can mimic natural “many inputs‐many outputs” relationships, ANN may be useful in the estimation of soil hydraulic properties from easily measurable soil data.

Abstract Cohesion increased for several months after disruption in moist soils. Rate at which cohesion increased was slower in airdry soil, but continued for years. Moduli of rupture of soils also increased with time. Effects of water content on the rate at which cohesion increases are compatible with an explanation of the bonding mechanism in terms of slightly soluble components diffusing to and cementing points of contact between particles. Cohesional forces due to water are estimated and found to be large enough to provide a major portion of the cohesion measured in soils. These estimates are supported by decreased cohesion of a silty soil when dried. However, cohesion of soils with larger amounts of clay generally increases when they are dried, indicating that other bonding mechanisms predominate.

The effect of parity (multiparous vs primiparous) and body condition score (BCS; <3.0 or > or =3.0, lean vs fat) at parturition on metabolic and endocrine profiles from 1 month before to 2 months after parturition were studied in 42 Holstein cows grazing on improved pastures. BCS and milk production were determined every 2 weeks. Non-esterified fatty acids (NEFA), beta-hydroxy-butyrate (BHB), insulin, IGF-I, leptin, thyroxine (T4) and 3,3',5-tri-iodothyroinine (T3) were determined in plasma every 10 days. Progesterone was determined three times per week after parturition. Primiparous cows had a lower BCS during the early postpartum period and produced less milk than multiparous animals. Primiparous cows had higher NEFA concentrations and they presented more samples with BHB concentrations of >1 mmol/l than multiparous cows. Multiparous cows had higher T3, T4 and IGF-I concentrations, while fat cows had higher leptin and IGF-I concentrations. All hormone concentrations were diminished in the first week postpartum. Primiparous cows and fat cows presented a steeper decay of IGF-I and leptin around parturition than multiparous cows and lean cows. While thyroid hormones and IGF-I showed increasing concentrations from approximately day 30, leptin concentrations remained low until the end of the experimental period. The initiation of ovarian cyclicity was delayed in primiparous cows and especially in primiparous lean cows, consistent with longer intervals from parturition to first service and to conception. The endocrine signals most likely to inform the reproductive axis regarding a negative energy balance were IGF-I and leptin.

Abstract The response of soil denitrification to increased soil moisture was compared in a non‐aggregated sandy loam soil and an aggregated clay loam soil using a soil core technique and the acetylene inhibition method. Elevated field denitrification rates were observed on 9 of 11 occasions on three sites following irrigation or rainfall of &gt; 1 cm water. The denitrification rate in the sandy loam soil increased immediately after water addition and reached a maximum rate within 3–5 h and returned to preirrigation levels within 12 h. A similar, but slower denitrification response occurred in the clay loam soil, requiring 8–12 h before a maximum rate was observed and 48 h before the original background rate was restored. Maximum denitrification rates of 209 and 383 ng N g −1 d −1 occurred following water inputs of 7 and 2 cm in the sandy loam and clay loam soils, respectively. These water additions resulted in air‐filled porosities of 0.37 m 3 m −3 in the two soils. Nitrogen losses from the clay loam soil were double that of the sandy loam although the sandy loam received almost twice the water input. This difference was apparently due to the longer duration of the enhanced denitrification rate in the clay loam soil following the increase in the soil moisture. In the two soils 38 and 55% of the total N loss in late spring occurred within 48 h after rainfalls greater than 1 cm. These studies confirm that significant denitrification losses can occur in bursts in response to rainfall, and illustrate that sampling schemes based on integration of denitrification rate measurements must include these episodes to obtain meaningful estimates of N loss. A denitrification response to rainfall was not always the case, however, suggesting that NO ‐ 3 or carbon may also limit nitrogen loss.

Abstract Adsorption isotherms were determined for sulfate adsorption on iron oxides under acid conditions. The product of the surface reaction between the iron oxides and sulfate ions was examined by infrared spectroscopy which showed four bands in the v S‐O stretching region. Thus a structural model could be obtained for the reaction. Two surface hydroxyl groups (or OH 2 + ions) are replaced by one sulfate ion, and two oxygen atoms of the sulfate ion are coordinated each to a different Fe 3+ ion, resulting in the binuclear bridging surface complex Fe‐O‐S(O 2 )‐O‐Fe. The complex is formed on the surfaces of goethite (α‐FeOOH), akaganéite (β‐FeOOH), lepidocrocite (γ‐FeOOH), hematite (α‐Fe 2 O 3 ) and amorphous ferric hydroxide.

Abstract A procedure developed for determining organic phosphorus in soils consisted of successive extractions with concentrated HCl and 0.5 N NaOH at room temperature, and 0.5 N NaOH at 90° C. The difference in content of inorganic and total phosphorus in the combined extracts was taken as total organic phosphorus in the soil. In a group of soils, values obtained by the proposed method were higher than those by other methods. Tests indicated that the higher values resulted from the greater accuracy of the proposed method.

The secure base and safe haven effects of the attachment figure are central features of the human attachment theory. Recently, conclusive evidence for human analogue attachment behaviours in dogs has been provided, however, the owner's security-providing role in danger has not been directly supported. We investigated the relationship between the behavioural and cardiac response in dogs (N= 30) while being approached by a threatening stranger in separation vs. in the presence of the owner, presented in a balanced order. Non-invasive telemetric measures of heart rate (HR) and heart rate variability (HRV) data during the threatening approaches was compared to periods before and after the encounters. Dogs that showed distress vocalisation during separation (N = 18) and that growled or barked at the stranger during the threatening approach (N = 17) were defined as behaviourally reactive in the given situation. While characteristic stress vocalisations were emitted during separations, the absence of the owner did not have an effect on dogs' mean HR, but significantly increased the HRV. The threatening approach increased dogs' mean HR, with a parallel decrease in the HRV, particularly in dogs that were behaviourally reactive to the encounter. Importantly, the HR increase was significantly less pronounced when dogs faced the stranger in the presence of the owner. Moreover, the test order, whether the dog encountered the stranger first with or without its owner, also proved important: HR increase associated with the encounter in separation seemed to be attenuated in dogs that faced the stranger first in the presence of their owner. We provided evidence for human analogue safe haven effect of the owner in a potentially dangerous situation. Similarly to parents of infants, owners can provide a buffer against stress in dogs, which can even reduce the effect of a subsequent encounter with the same threatening stimuli later when the owner is not present.

Abstract The exchangeable acidity determined by neutral 1 N NH 4 OAc was compared to that measured in a buffered solution on 348 soil samples from profiles of Red‐Yellow Podzolic soils in Alabama. The soil pH values ranged from 4.1 to 6.5 and cation‐exchange capacities from 0.8 to 13.0 me. per 100 g. The methods measured comparable amounts of acidity. An equation was calculated by the method of least squares for the relationship between soil pH and percent base unsaturation for all samples. The amount of CaCO 3 needed to bring soil pH to desired level was calculated by estimating percent base unsaturation from soil pH values in water and by measuring exchangeable acidity of soil by pH values in a buffered solution. The validity of this procedure was tested by incubating soils with increments of Ca(OH) 2 and measuring the change in soil pH.

Abstract Soil hydraulic properties are required in various modelling schemes. We propose a consistent spatial soil hydraulic database at 7 soil depths up to 2 m calculated for Europe based on SoilGrids250m and 1 km datasets and pedotransfer functions trained on the European Hydropedological Data Inventory. Saturated water content, water content at field capacity and wilting point, saturated hydraulic conductivity and Mualem‐van Genuchten parameters for the description of the moisture retention, and unsaturated hydraulic conductivity curves have been predicted. The derived 3D soil hydraulic layers (EU‐SoilHydroGrids ver1.0) can be used for environmental modelling purposes at catchment or continental scale in Europe. Currently, only EU‐SoilHydroGrids provides information on the most frequently required soil hydraulic properties with full European coverage up to 2 m depth at 250 m resolution.

Reflectance spectra of salt-affected surface soil samples have been measured at 10 nm spectral resolution between 495 nm and 2395 nm. The samples were collected in California (41) and in Hungary (49) to compare the effect of different salinization and alkalization processes on reflectance properties. The data set consisted of 272 spectra having 2–12 cases (repetitions) for each sample. Sixteen classes were defined based on chemical soil properties, accounting for changes in pH, electrical conductivity (EC), and exchangeable sodium percentage (ESP), of which 12 were represented in the sample. The reflectance data set was statistically analyzed using a modified stepwise principal component analysis (MSPCA) approach to select 1, 2, 3, … bands for classification of salinity status. Recognition of the above-described classification was tested by discriminant function analysis (DFA). Its results can be applied in further studies for weighing spectral bands according to their sensitivity to the chosen classification as well as in defining broad, but still potentially sufficient bands. Recognition accuracy of salinity status was 91%, 90%, and 88% with 10 nm, 20 nm, and 40 nm bands, respectively, for the entire data set. Comparison with PCA using all bands showed only slight differences. The California soil samples had more distinct spectral characteristics than the Hungarian ones. Key spectral ranges were identified in the visible (550–770 nm), near-infrared (900–1030 nm, 1270–1520 nm), and middle infrared (1940–2150 nm, 2150–2310 nm, 2330–2400 nm) portion of the spectrum at 20 nm, 40 nm, and 80 nm spectral resolution. Two of these (1270–1520 nm and 1940–2150 nm) cannot be used with satellite data due to water vapor absorption in the atmosphere. In addition, six broad bands in these ranges were identified, leading to considerably higher overall accuracy than currently available Landsat MSS, TM, and SPOT XS, in terms of spectral recognition of salinity status.

Abstract Aluminum‐sensitive ‘Monon’ wheat ( Triticum aestivum , spp vulgare (Vill. Host) Mac Key and ‘Kearney barley ( Hordeum vulgare ) (L. emend. Lam) varieties had higher root cation exchange capacities and induced lower pH levels in nutrient solutions than did Al‐tolerant ‘Atlas 66’ wheat and ‘Dayton’ barley varieties. Sensitive varieties contained higher concentrations of Al (and usually P) in their roots and lower concentrations of Ca in their tops than tolerant varieties, when grown in solutions containing Al. Furthermore, roots of Al‐sensitive varieties made less growth and contained higher concentrations of Al than those of tolerant varieties, even when the two were grown in the same container of vigorously aerated nutrient solution. This suggests either that zones of differential pH still exist around the roots of different varieties or that sensitive varieties absorb more Al at the same pH or both. Whether the lower Al tolerance of certain varieties is simply the result of greater accumulation of Al by roots, greater sensitivity to the same concentration of Al already absorbed, or both, cannot be determined from the present study. Differential Al tolerance of varieties was not closely related to differences in the Al or P contents of plant tops.

Abstract Within the United Nations Framework Convention on Climate Change, articles 3.3 and 3.4 stipulate that some voluntary activities leading to an additional carbon (C) sequestration in soils could be accounted as C sinks in national greenhouse gas inventories. These additional C stocks should be verifiable. In this work, we assess the feasibility of verifying the effects of changes in land use or management practice on soil organic carbon (SOC), by comparing minimum detectable changes in SOC concentration for existing European networks suitable for soil monitoring. Among the tested scenarios, the minimum detectable changes differed considerably among the soil‐monitoring networks (SMNs). Considerable effort would be necessary for some member states to reach acceptable levels of minimum detectable change for C sequestration accounting. For SOC, a time interval of about 10 years would enable the detection of some simulated large changes in most European countries. In almost all cases, the minimum detectable change in SOC stocks remains greater than annual greenhouse gases emissions. Therefore, it is unlikely that SMNs could be used for annual national C accounting. However, the importance of organic C in soil functions, and as an indicator of soil condition and trends, underlines the importance of establishing effective national SMNs.

Abstract The water content‐pressure head relationship for a small, well‐confined, rectangular sample of fine sand was obtained under different water flow conditions. Water contents were measured by a gamma system and pressure heads were measured by a tensiometer‐pressure transducer combination. During drying, more water was retained in the sand at a given pressure head in the unsteady flow case than in the static equilibrium and steady‐state cases, which agreed with each other.

Legacy soil data have been produced over 70 years in nearly all countries of the world. Unfortunately, data, information and knowledge are still currently fragmented and at risk of getting lost if they remain in a paper format. To process this legacy data into consistent, spatially explicit and continuous global soil information, data are being rescued and compiled into databases. Thousands of soil survey reports and maps have been scanned and made available online. The soil profile data reported by these data sources have been captured and compiled into databases. The total number of soil profiles rescued in the selected countries is about 800,000. Currently, data for 117, 000 profiles are compiled and harmonized according to GlobalSoilMap specifications in a world level database (WoSIS). The results presented at the country level are likely to be an underestimate. The majority of soil data is still not rescued and this effort should be pursued. The data have been used to produce soil property maps. We discuss the pro and cons of top-down and bottom-up approaches to produce such maps and we stress their complementarity. We give examples of success stories. The first global soil property maps using rescued data were produced by a top-down approach and were released at a limited resolution of 1km in 2014, followed by an update at a resolution of 250m in 2017. By the end of 2020, we aim to deliver the first worldwide product that fully meets the GlobalSoilMap specifications.

Abstract A theoretical approach, based upon the assumption of predominance of solvophobic interactions, was formulated to quantitatively describe the sorption and transport of hydrophohic organic chemicals (HOC) from aqueous and aqueous‐organic‐solvent mixtures. In the theoretical approach, solvent‐sorbate interactions (solubility) are specifically considered in order to predict sorbate‐sorbent interactions (sorption). For HOC sorption from a single solvent, the HOC sorption coefficient was shown to increase loglinearly with the hydrocarbonaceous surface area (HSA) of the sorbate. For HOC sorption from aqueous‐organic binary solvent mixtures, the sorption coefficient is predicted to decrease exponentially as the fraction of organic cosolvent increases. This is a direct consequence of increased HOC solubility in the binary solvent. Because sorption and mobility of HOC are inversely related, a decrease in sorption coefficient leads to an enhanced HOC mobility as the fraction of organic cosolvent is increased. A preliminary verification of the theory was performed by an analysis of published data for (i) HOC sorption by soils and sediments from water, (ii) HOC retention by reversed‐phase chromatographic sorbents during isocratic elution with methanol‐water binary solvent mixture, and (iii) HOC mobility on soil‐TLC plates eluted with ethanol‐water mixtures.

Abstract Pure‐solution and soil‐solution experiments were conducted in which the solubility products of synthetic basaluminite and alunite in pure solutions were compared with the ion‐activity products of Al 4 (OH) 10 SO 4 and KAl 3 (OH) 6 (SO 4 ) 2 in soil solutions of sulfate‐treated soil. Solution experiments were conducted in which 0.05 M Al 2 (SO 4 ) 3 was titrated with NaOH, KOH, or Ca(OH) 2 to an OH/AI mole ratio of 2.0. The initial precipitate was amorphous, with the chemical composition of basaluminite, Al 4 (OH) 10 SO 4 ·5H 2 O. Aging the amorphous precipitates under different conditions transformed them to compounds of different composition and crystallinity: amorphous precipitate remained unchanged when aged in their mother solutions at 25°C; crystalline basaluminite formed in Ca mother solutions when aged at 50°C; crystalline alunite formed in Na and K mother solutions when aged at 50°C; crystalline alunite formed in K mother solutions that had been seeded with alunite or bentonite when aged at 25°C. The solubilities of the amorphous and crystalline precipitates were determined in dilute NaClO 4 solutions and gave the following average calculated pK sp values: 116.0 for amorphous basaluminite; 117.7 for crystalline basaluminite; 79.7 for Na‐alunite; and 85.4 for K‐alunite. Similar K sp values for basaluminite were found for soil solutions from a sandy loam soil that had been treated with different rates of K 2 SO 4 . However, the soil solutions were supersaturated with respect to alunite. When the SO 4 ‐treated soil was subsequently treated with a high rate of KH 2 PO 4 , the soil solution remained supersaturated with respect to alunite, but became undersaturated with respect to basaluminite. It is proposed that sulfate retention by acid soils is a consequence of the solubility of basaluminite and/or alunite.

Abstract. In this paper, we present and analyze a novel global database of soil infiltration measurements, the Soil Water Infiltration Global (SWIG) database. In total, 5023 infiltration curves were collected across all continents in the SWIG database. These data were either provided and quality checked by the scientists who performed the experiments or they were digitized from published articles. Data from 54 different countries were included in the database with major contributions from Iran, China, and the USA. In addition to its extensive geographical coverage, the collected infiltration curves cover research from 1976 to late 2017. Basic information on measurement location and method, soil properties, and land use was gathered along with the infiltration data, making the database valuable for the development of pedotransfer functions (PTFs) for estimating soil hydraulic properties, for the evaluation of infiltration measurement methods, and for developing and validating infiltration models. Soil textural information (clay, silt, and sand content) is available for 3842 out of 5023 infiltration measurements (∼ 76%) covering nearly all soil USDA textural classes except for the sandy clay and silt classes. Information on land use is available for 76 % of the experimental sites with agricultural land use as the dominant type (∼ 40%). We are convinced that the SWIG database will allow for a better parameterization of the infiltration process in land surface models and for testing infiltration models. All collected data and related soil characteristics are provided online in *.xlsx and *.csv formats for reference, and we add a disclaimer that the database is for public domain use only and can be copied freely by referencing it. Supplementary data are available at https://doi.org/10.1594/PANGAEA.885492 (Rahmati et al., 2018). Data quality assessment is strongly advised prior to any use of this database. Finally, we would like to encourage scientists to extend and update the SWIG database by uploading new data to it.