Soil survey interpretation: Estimating use-potentials of a clay soil under various moisture regimes

Current Dutch soil survey interpretation emphasizes assessment factors which independently define key aspects of soil behavior under actual conditions. For grassland these are: moisture-supply capacity, bearing capacity and drainage status. Practical questions focus on how actual limitations can be overcome. Computer simulation techniques, to be focused on the individual assessment factors, are needed to answer these questions. Soil survey and morphology data were used in this context to: (1) select experimental sites; (2) modify physical monitoring procedures; (3) derive simulation models for swelling soils with macropores; (4) develop simple field methods for characterizing basic physical soil properties and their regional variability, and (5) use soil maps for extrapolating the obtained interpretations.Future soil survey reports should ideally contain basic physical data and the possible ranges for the different assessment factors, expressed by simulation as a function of water management. basic data include hydraulic conductivity, moisture retention, bearing capacity and drainage rate. The latter two were characterized in this study by new field methods. Possible ranges differ for the different assessment factors. For example, an inadequate moisture supply capacity in the growing season can be completely compensated by raising the water table, by sprinkler irrigation or by a combination of both methods. The presented simulation offers a quantitative analysis. The inadequate bearing capacity and drainage status can be compensated for only partly by lower water-table levels in winter and spring.     

Shrinkage of clay soils: A statistical correlation with other soil properties

The hypothesis that the shrinkage of soils is greater when expansible minerals are dominant was tested with 63 soils containing between 40 and 64% clay. Shrinkage between pF 2 and 4 (0.1 and 10 bar) correlated significantly with the expansible mineral content (measured by ethylene glycol retention) for remoulded but not for dried and rewetted specimens. Shrinkage between pF 4 and 6 (10 and 10³ bar) was strongly correlated with the expansible mineral content for both kinds of specimens. The physical significance of the results is discussed, and it is concluded that interlamellar shrinkage is not the principal component of bulk shrinkage.     

Fixed ammonium determination in some clay soils

Abstract

We have shown that the traditional Kjeldahl method applied to clay soils of the Duero Basin (Spain) is not effective; so, it is necessary to add HC1 + HF to free trapped ammonium. This fixed ammonium has been measured by two methods which give significantly different results. The level of fixed ammonium in cultivated clay soils is relatively high (it ranges from 180 to 490 ppm). Fixed ammonium is significantly correlated to clay content and total inorganic nitrogen of the soil. A proposed method of analysis for total N is given.     

Subsoiling in some heavy clay soils of Egypt

Four soil profiles were selected to represent the heavy clay soils of alluvial and lacustrine origin. The locations studied had been subsoiled at least once during the year before the investigation. Field observations and laboratory analyses were carried out to ascertain the subsoiling effect on the soil profile properties. For further confirmation, soil penetration tests were performed on material from all the sites studied. The data revealed that subsoiling is not to be recommended in the Vertisols or the heavy clay soils adjacent to the northern Delta lakes of Egypt because these soils develop abundant natural cracks of 3–5 cm in width and 50–70 cm in depth. There are no impervious layers in the top 60 cm of the soils in the study area, and there is no evidence of soil compaction throughout the top 70 cm in all the sites studied.     

A new method for studying clay soils using unaltered soil blocks

The purpose of this paper is to outline a procedure for soil block extraction, which is highly appropriate for clay soils. The method described here is rapid and cheap and has been used successfully by us in clay soils in southern Spain for the last six years. A wooden box is used to shape the soil block in situ and protect it during its transport from the field to the laboratory. Polyurethane foam was selected as the bonding agent, between the wooden framework and the soil block in order to avoid any possible alterations of the soil. This type of foam is used because it is strong, durable and non-toxic. The polyurethane foam is applied to the soil block as a permanent coating. This technique allows us to extract the clay soil solution in the laboratory.     

A case study on infiltration into dry clay soil I. Morphological observations

Infiltration patterns of water into four dry clay soils with different macrostructures were determined in the field as a function of application rate (i = 4?80 mm/h) and applied quantity (q = 2.5?40 mm), using methylene blue as a tracer. Stains on the walls of large vertical pores (dominantly planar voids) occurred as small vertical bands and were observed and counted to a depth of 1 m after excavation of the 0.5 m² plots. Deep infiltration through large pores, as demonstrated by occurrence of stained bands, could be manipulated by varying application rates and applied quantities. The number of stained bands was always very low, occupying at the most an estimated 2% of the available vertical surface area of large prisms, and (for each stained band) a horizontal cross-sectional area of 60 cm² or more. Infiltration was deeper, at comparable flow regimes, in two soils with strongly developed prisms, as compared with two soils with moderately developed prisms. Deep infiltration occurred along vertical prism faces where grass roots were also concentrated.     

Tentative assessment of soil survey approaches to the characterization and interpretation of air-water properties of soils

Procedures used by soil survey organizations in characterizing and interpreting the air—water regimes of soils in France, Germany, The Netherlands, England and Wales, the United States and Canada are summarized and compared. The strengths and weaknesses of the systems are discussed, and research is suggested to resolve problems and to improve the basis of interpretations. The importance of sound field estimates supported regularly by reliable measurements is emphasized. Field estimates are essential in view of the dynamic nature and the spatial variability of some soil physical properties related to the air—water regimes. Research needs include continued development of improved methods of measuring air—water properties of soils, development of improved guidelines for estimating these properties from soil morphology, and identification of the relevant soil properties that can be estimated reliably. Interdisciplinary research is required to integrate expertise in hydrology, soil physics, agronomy and pedology with a view to improving the characterization and interpretation of air—water properties of soils.     

Effect of tillage treatments on soil thermal conductivity for some Jordanian clay loam and loam soils

Soil thermal conductivity determines how a soil warms or cools with exchange of energy by conduction, convection, and radiation. The ability to monitor soil thermal conductivity is an important tool in managing the soil temperature regime to affect seed germination and crop growth. In this study, the temperature-by-time data was obtained using a single probe device to determine the soil thermal conductivity. The device was used in the field in some Jordanian clay loam and loam soils to estimate their thermal conductivities under three different tillage treatments to a depth of 20 cm. Tillage treatments were: no-tillage, rotary tillage, and chisel tillage. For the same soil type, the results showed that rotary tillage decreased soil thermal conductivity more than chisel tillage, compared to no-tillage plots. For the clay loam, thermal conductivity ranged from 0.33 to 0.72 W m⁻¹ K⁻¹ in chisel plowed treatments, from 0.30 to 0.48 W m⁻¹ K⁻¹ in rotary plowed treatments, and from 0.45 to 0.78 W m⁻¹ K⁻¹ in no-till treatments. For the loam, thermal conductivity ranged from 0.40 to 0.75 W m⁻¹ K⁻¹ in chisel plowed treatments, from 0.34 to 0.57 W m⁻¹ K⁻¹ in rotary plowed treatments, and from 0.50 to 0.79 W m⁻¹ K⁻¹ in no-till treatments. The clay loam generally had lower thermal conductivity than loam in all similar tillage treatments. The thermal conductivity measured in this study for each tillage system, in each soil type, was compared with independent estimates based on standard procedures where soil properties are used to model thermal conductivity. The results of this study showed that thermal conductivity varied with soil texture and tillage treatment used and that differences between the modeled and measured thermal conductivities were very small.     

Evaluation of soil test methods for estimation of available phosphorus in some Portuguese soils: A greenhouse study

Abstract

The Egnér‐Riehm method for estimating plant‐available soil phosphorus (P) has been used as the standard soil testing method in Portugal for making fertilizer recommendations. However, this method does not accurately reflect the available P status for wheat in some representative soils from the South Region of the country. Therefore, a pot experiment was established with four Luvisols (LVx, LVv, and two different LVh soils) from the South Region of Portugal in order to evaluate the Egnér‐Riehm, Bray I, Bray II, Olsen, and Anion Exchange Resin (AER) methods for their ability to estimate available P in those soils. Wheat (Triticum aestivum L., cv. Panda) was used as test the crop. The experiment was arranged into a randomized complete block design with three replications and five rates (0, 50, 100,150, and 200 mg kg^‐1) of P added to each soil. Critical soil P levels for LVx were established in case for Bray I (27.9 mg kg^‐1), Bray II (33.5 mg kg^‐1), Egnér‐Riehm (25.4 mg kg^‐1), and AER (14.7 mg kg^‐1) soil test procedures. Regarding the other soils, the critical soil P levels could not be estimated. The obtained results confirm that the development of an universal soil test P exti action is of great importance, and that further research should be conducted in order to evaluate routine soil fertility tests in different pedoclimatic environments.     

Shapes of aggregates from tilled layers of some Dutch and Australian soils

Five different methods were used to study the shapes of soil aggregates oriented in their planes of maximum projection. A measure of roundness was found to be relatively insensitive to shape features. The shortest aspect ratio (the ratio of the shortest to the longest diameters through the centroid) was found to be most sensitive of the “single value” shape measures. More comprehensive shape information was given by values of the radius spectra and the curvature spectra. The curvature spectra method seems to be slightly more sensitive than the radius spectra method and can also be applied to reentrant particles.Generally it was found that aggregates are less round with increasing clay content and decreasing organic matter content. There was also a hint that aggregates of the Dutch soils may become less round with increasing age since their reclamation. The Australian soil aggregates were slightly rounder than the Dutch aggregates.     

Refining soil survey information for a Dutch soil series using land use history

Abstract. Differences in land-use history within soil series, although not influencing soil classification, lead to variability of non-diagnostic soil properties in soil databases. Regional studies that use soil databases are confronted with this considerable variability. This has, for example, been reported in regional studies focused on nitrate leaching from agricultural land. Such findings have a direct impact on regional assessments of nitrate leaching from dairy farms on sandy soils, a major environmental issue in the Netherlands. There is thus a need to deal with this variability in soil properties.
We were able to relate soil organic nitrogen, soil organic carbon and its dynamics to land use history for a Dutch sandy soil series. Within one soil series, three different land use histories were identified: old grassland, reseeded grassland and grassland converted from continuous cropping with silage maize. The addition of landscape characteristics significantly improved the regression models based on land-use only. Once established for any given soil series, such relationships can significantly improve soil survey input into dynamic models of soil behaviour such as regional nitrate leaching studies.     

Lability of soil organic carbon in tropical soils with different clay minerals

Soil organic carbon (SOC) storage and turnover is influenced by interactions between organic matter and the mineral soil fraction. However, the influence of clay content and type on SOC turnover rates remains unclear, particularly in tropical soils under natural vegetation. We examined the lability of SOC in tropical soils with contrasting clay mineralogy (kaolinite, smectite, allophane and Al-rich chlorite). Soil was sampled from A horizons at six sites in humid tropical areas of Ghana, Malaysian Borneo and the Solomon Islands and separated into fractions above and below 250 μm by wet sieving. Basal soil respiration rates were determined from bulk soils and soil fractions. Substrate induced respiration rates were determined from soil fractions. SOC lability was significantly influenced by clay mineralogy, but not by clay content when compared across contrasting clay minerals. The lability of SOC was lowest in the allophanic and chloritic soil, higher in the kaolinitic soils and highest in the smectitic soil. Our results contrast with conventional concepts of the greater capacity of smectite than of kaolinite to stabilize SOC. Contents of dithionite-citrate-bicarbonate extractable Fe and Al were inversely related to SOC lability when compared across soil types. A stronger inverse correlation between content of ammonium-oxalate extractable Fe and SOC lability was found when considering the kaolinitic soils only and we conclude that the content of active Fe (hydr-) oxides controls SOC stabilization in the kaolinitic soils. Our results suggest that the validity of predictive models of SOC turnover in tropical soils would be improved by the inclusion of soil types and contents of Fe and Al (hydr-) oxides.     

13C NMR studies of organic matter in whole soils: H. A case study of some Rothamsted soils

Nuclear magnetic resonance (NMR) spectra were obtained for solid samples of whole soils from three long–term field sites at Rothamsted Experimental Station, UK. In all sites, soil organic matter content was either increasing or decreasing due to contrasted long–continued treatments. Two soils were from Highfield, one from under old grassland (47 g organic C kg^?1) and one from an area kept as bare fallow following ploughing of grass 21 years previously (14 g organic C kg^?1). Three soils were taken from Broadbalk, two from plots within the Broadbalk Continuous Wheat Experiment which had received no fertilizer or animal manure annually for 148 years (7 and 27 g organic C kg^?1, respectively) and one from Broadbalk Wilderness, wooded section (38 g organic C kg^?1). Broadbalk Wilderness was arable until 1881 and has reverted to deciduous woodland in the subsequent 110 years. Two soils were from Geescroft, one from an arable field (9 g organic C kg^?1) and one from Geescroft Wilderness (35 g organic C kg^?1) which began reversion to deciduous woodland at the same time as Broadbalk Wilderness but is now acid (pH = 4.2) in contrast to Broadbalk which is calcareous (pH = 7.3). Solid–state ¹³C NMR spectra were obtained on a 300–MHz instrument using cross polarization (CP) and magic angle spinning (MAS). All samples exhibited peaks in the following spectral regions: 0–45 ppm (alkyl), 45–60 ppm (methoxyl, carbohydrate and derivatives), 60–110 ppm (carbohydrates and derivatives, C–α of peptides), 110–160 ppm (aromatics) and 160–185 ppm (carboxyl groups and derivatives). Within the spectrum of a specific sample it was not possible to determine the relative proportions of soil organic carbon in the different forms identified because a range of factors can potentially alter the relative areas of peaks in different regions of the spectrum. However, from a comparison of relative peak areas within a set of soils from a given site, differing only in organic matter content, information can be deduced regarding the forms of C that are more or less subject to change in response to land use or management. At all sites carbohydrate C appears to be the form that is most subject to change, suggesting that it is an ‘active’ fraction compared with the other forms. It was greatest where organic matter inputs were greatest (due to inputs of farmyard manure or reversion to woodland) and declined relative to other forms following ploughing of old grassland. Alkyl C increased as total C accumulated but did not decline relative to other forms following ploughing of grass. One reason for the non–quantitative nature of the soil ¹³C CPMAS spectra was a short (approximately 1 ms) component of the rotating–frame T_I relaxation time for H nuclei (T_1pH). This problem was not overcome by acquiring data at – 60°C. In principle, solid–state spectra of soils obtained by direct polarization (i.e. without CP) might produce quantitative results, but the low C content of most mineral soils (10–50 g C kg^?1) precludes this, given current instrumentation.     

A soil core sampler for paddy soils and some physical properties of the soils under waterlogged condition

Introduction

Recent investigations in soil science have shown that physical properties of paddy soils are of great importance to rice-production. There is extensive literature on the chemical property of paddy soils, but little information on the physical property of paddy soils, especially under waterlogged condition. For studying the physical property of flooded paddy soils, it is necessary to collect the soil cores under an undisturbed condition.     

A study of argillic horizons in some soils in Morocco

Whether some soils observed in Morocco prior to the 1966 conference on Mediterranean soils held in Madrid had argillic horizons was the subject of active discussions. Textural differences between A- and B-horizons were obvious. Consequently, individual horizons of a number of profiles were sampled for micromorphological study. No clay films were observed in thin sections representing the B-horizons free in carbonate. Peds had pressure faces and internal striations in the matrix. Microchurning and swelling and shrinking are believed to have obliterated evidence of clay illuviation in the B-horizons, but clay coatings were observed at greater depth in well-developed B_ca-horizons.     

Fractionation of soil cadmium from some new zealand soils

Abstract

The concentrations and forms of soil cadmium (Cd) in 12 different New Zealand topsoils were investigated using a sequential fractionation procedure. Total soil Cd concentrations were low and ranged between 0.03 μg g^‐1 to 1.34 μg g^‐1 and were highly correlated with total soil phosphorus (r²=0.85, P<0.01). Results indicated that there was a wide range in the concentrations of Cd associated with individual soil fractions and large variations between soils. On average for all soils, the smallest proportion of Cd was in exchangeable forms, i.e., 3%, with 12% in the crystalline oxide fraction, 13% in the amorphous oxide fraction and the greatest proportion of Cd associated with the organic 34% and residual 38% fractions. There was evidence to show that a soil extractant which is commonly used to predict plant uptake of Cd from soils, i.e., 0.04 M ethylene diamine terra acetic acid (EDTA), extracts Cd from both exchangeable and organic forms of soil Cd.     

Rainfall erosion of some Alberta soils A laboratory simulation study

This laboratory rainfall simulation study investigates the effects of soil properties, slope steepness, and cover density on rainfall erosion potential of 153 soil samples collected in Southern Alberta, Canada. Simulated rainfall amount was held constant for these tests Of all the factors examined, simulated vegetative cover was found to be most significant. When cover was held constant, soil aggregate stability is the best predictor of variations of soil erodibility. Organic carbon content, texture and runoff amount (infiltration capacity) are other significant variables Slope was found to be significantly related to wash loss but not splash loss Two factors were proposed to explain the lack of relationship between splash loss and slope: (a) the proportion of splashed particles collected outside the sample plan may vary with the size of the pan; (b) soil transportability by splash increases only slightly with slope angle and therefore splash loss is only marginally related to slope steepness     

Mapping soil clay contents in Dutch marine districts using gamma‐ray spectrometry

Conventional soil sampling methods to obtain high‐resolution soil data are labour intensive and costly. Recently, gamma ray spectrometry has emerged as a promising technique to overcome these obstacles. The objective of our study was to investigate the prediction of soil clay contents using gamma‐ray spectrometry in three marine clay districts in the Netherlands: the southwestern marine district (SMD), the IJsselmeerpolder district (IJPD) and the northern marine district (NMD). The performance of linear regression models was investigated at field (<1 km²), regional (1–1000 km²) and district (>1000 km²) scales and for all the Dutch marine districts together. For this study, a database was available with 1371 gamma‐ray spectra measured on arable fields in marine clay districts during the period 2005–2008 and these were all linked to laboratory analyses of clay contents. At the field scale, linear regression models based on ⁴⁰K, ²³²Th, or a combination of these revealed much smaller root mean squared error (RMSE) values (2–3%) compared with a model based on the field mean (8–10%). At the district scale, the regression models for the SMD and IJPD, which have comparable sediments, performed better than for the NMD. This indicates that the prediction of clay contents in late Holocene marine sediments may be made with gamma‐ray spectrometry provided that the origin of the parent material results in a unique fingerprint. Because of the heterogeneous parent material of all marine districts taken together, our study shows that no unique and precise fingerprint exists, and the RMSE of 6% between clay contents and gamma‐ray spectra is not much different from the RMSE of 7% when using the overall mean as a predictor.