Explore the vast range of titles available.

Although it has been recognized that the adsorption of organics to clay and silt particles is an important determinant of the stability of organic matter in soils, no attempts have been made to quantify the amounts of C and N that can be preserved in this way in different soils. Our hypothesis is that the amounts of C and N that can be associated with clay and silt particles is limited. This study quantifies the relationships between soil texture and the maximum amounts of C and N that can be preserved in the soil by their association with clay and silt particles. To estimate the maximum amounts of C and N that can be associated with clay and silt particles we compared the amounts of clay-and silt-associated C and N in Dutch grassland soils with corresponding Dutch arable soils. Secondly, we compared the amounts of clay-and silt-associated C and N in the Dutch soils with clay and silt-associated C and N in uncultivated soils of temperate and tropical regions. We observed that although the Dutch arable soils contained less C and N than the corresponding grassland soils, the amounts of C and N associated with clay and silt particles was the same indicating that the amounts of C and N that can become associated with this fraction had reached a maximum. We also observed close positive relationships between the proportion of primary particles < 20 µm in a soil and the amounts of C and N that were associated with this fraction in the top 10 cm of soils from both temperate and tropical regions. The observed relationships were assumed to estimate the capacity of a soil to preserve C and N by their association with clay and silt particles. The observed relationships did not seem to be affected by the dominant type of clay mineral. The only exception were Australian soils, which had on average more than two times lower amounts of C and N associated with clay and silt particles than other soils. This was probably due to the combination of low precipitation and high temperature leading to low inputs of organic C and N. The amount of C and N in the fraction > 20 µm was not correlated with soil texture. Cultivation decreased the amount of C and N in the fraction > 20 µm to a greater extent than in the fraction < 20 µm, indicating that C and N associated with the fraction < 20 µm is better protected against decomposition. The finding of a given soil having a maximum capacity to preserve organic C and N will improve our estimations of the amounts of C and N that can become stabilized in soils. It has important consequences for the contribution of different soils to serve as a sink or source for C and N in the long term.

Zeolite and vermicompost applications to soil may improve K fertility of soils. For this purpose, these materials were added to five representative calcareous soils collected from southern Iran. The treatments included (1) control, (2) 20 g/kg zeolite, (3) 20 g/kg vermicompost, and (4) 20 g/kg vermicompost + zeolite (1:1). The samples were incubated for 90 days, and the concentrations of soluble, exchangeable, and non-exchangeable K and K release rate to 0.01M CaCl2 during 240 min (16 successive 15 min extractions of soil samples with CaCl2 solution) were determined. Results indicated that zeolite application increased significantly the concentration of soluble and exchangeable K. Vermicompost application had a positive effect on all forms of K. Cumulative K release was also affected by vermicompost application. Comparison of experimental data to different kinetic models indicated that Elovich, power function, and parabolic diffusion models described well kinetics of K release from all soil samples to 0.01M CaCl2. The b values of Elovich equation had significant relationships with NH4OAc- and HNO3-extractable K. It is recommended that for K fertility management of calcareous soils, organic and inorganic amendments application to soils should be taken into consideration.

One of the most important binding agents for forming stable aggregates is a soil organic matter (SOM), which can be retained in various size fractions of aggregates. If aggregates are water-resistant, they retain more carbon. Therefore, the aim of this study was to evaluate the stability of aggregates and their ability of carbon sequestration in different soil types and soil management systems in Slovakian vineyards. The highest content of water-stable macro-aggregates (WSAma) was determined in Cambisols, and the lowest in Fluvisols. The highest content of WSAma (size fraction 0.5–3 mm) was determined in Chernozems, decreasing within the following sequence: Fluvisols > Leptosols > Cambisols > Luvisols. The soil type had a statistically significant influence on the re-distribution of soil organic matter in size fractions of water-stable aggregates. The highest content of SOM in water-stable aggregates of the vineyards was determined in grassy strips in-between the vineyard rows in comparison to intensively cultivated rows of vineyard. The highest values of carbon sequestration capacity (CSC) in WSAma were found in Cambisols > Leptosols and the lowest values of CSC were in Fluvisols. The micro-aggregates represented a significant carbon reservoir for the intensively cultivated soils (rows of vineyard). On the other hand, increasing of macro-aggregates (size fraction 0.5–3 mm) was characteristic for grassland soils (between the rows of vineyard).

Amounts of potassium (K) fixed in soil fractions of 10 calcareous soils of southern Iran were measured to evaluate the contributions of different soil size fractions to K fixation. Soil particles were fractionated after dispersion of the soils with an ultrasonic probe. Potassium fixation analysis was done by addition of 1000 mg K/kg samples. Mineralogy of the size fractions was determined by X-ray diffraction. The clay fractions were dominated by smectite, chlorite, mica, and palygorskite. Potassium fixation capacities ranged from 104 to 148 mg/kg for clay, from 102 to 155 mg/kg for silt, and from 96 to 187 mg/kg for sand fractions. A positive and significant relationship (P < 0.05) was obtained between K fixation capacity and smectite content for the clay fractions. High amounts of K fixed in the sand fraction may be explained by a larger diffusion path of fixed K out of the frayed edges of micaceous and smectitic minerals into the extracting solution, low cation exchange capacity (CEC) of the coarse fraction and thereby the high concentration gradient along solution and interlayers, physical entrapment of K ions in coarse aggregates cemented by carbonates, and by the presence of clay particles in coarse fractions due to incomplete dispersion of coarse aggregates.

Heavy metal (Cu, Zn, Cd, Pb and Fe) concentrations in salt marsh sediments of the Karnafully River coast were investigated in this study. Sediment samples of four different sites were analysed for selected heavy metals by AAS (atomic absorption spectrophotometry). The mean values of heavy metals were 45.79 µg/g for Cu, 105.0 µg/g for Zn, 0.43 µg/g for Cd, 26.70 µg/g for Pb and 3297.38 µg/g for Fe in this study. It is observed that Pb and Cu have positive correlations (r = 0.370, P < 0.05) and Fe and Zn have negative correlations (r = -0.729, P < 0.05) in the correlation matrix. Except Fe, all the metals were found at contamination levels which may indicate a recent and continuous contamination from domestic and industrial discharges. The results of sediment samples showed that the Karnafully River coast is facing heavy metal pollution.

The database of soil hydrophysical properties in the Czech Republic (HYPRESCZ) which contains the data needed for derivation of pedotransfer functions for soil water retention curves was used for the estimation of field capacity and wilting point of agricultural land resource on a countrywide scale. The results were combined with the existing Soil Texture Map of the Czech Republic to create four new maps, namely the Map of Field Capacity and the Map of Wilting Point for the topsoil and subsoil separately. From the total number of 1048 relevant database entries, only about a half included reliable wilting point data. The k-Nearest computer code employing the k-Nearest neighbour technique was used for estimation of the missing wilting points, which made it possible to use all entries. The estimation uncertainty was assessed in terms of standard deviations and the root mean square error. Finally, two sets of class pedotransfer functions were derived and found sufficiently comparable: (i) the functions estimating the soil water retention curve in the whole range, derived solely from the database entries containing the measured wilting points, and (ii) the functions estimating the field capacity and wilting point only, derived from all database entries, including the k-Nearest neighbour estimated data.

Determination of the sorption-desorption of herbicides within soil profile is one of the first steps in predicting their leaching potential. Batch experiments were performed to evaluate the influence of soil properties on acetochlor retention. Soil samples were taken from horizons A, B, and C of three soil types representative of the Žitný ostrov area. The sorption and desorption isotherms were fitted to the Freundlich equation. The Freundlich sorption coefficient (Kfs) values ranged from 0.71 to 6.58 mg(1–1/n).l(1/n)/kg and were correlated positively with soil organic carbon, humic and fulvic acid carbons, amorphous aluminum oxides, and negatively with soil pH. The Freundlich desorption coefficient (Kfd) values were greater than those for sorption, showing that not all acetochlor sorbed was desorbed after four washing steps. The percentage of acetochlor desorbed ranged from 7.80 to 54.5% with decreased desorption from soil horizons B and C. The higher sorption capacity of surficial soil horizons in the three soils may be a limiting factor for penetration of acetochlor through soil profiles into groundwater.

Flooding caused by intensive precipitation has been in the centre of attention of both general public and scientists. From the flood risk management perspective, an integrated approach to catchment management is necessary, in particular with regards to water retention capacity. Our research has been focused on the high intensity rainfall, its short duration, and an adequate infiltration capacity into the soil profile in the upper parts of the catchment, the same as on the impact of soil characteristics such as moisture content and suction pressure, in particular. The five-year research period in two sub-catchments – Červík A and B – in the Beskydy Mts. enabled monitoring of about 300 events, and seventy of them with higher rainfall intensity were selected for further analysis. The analysis showed that the retention of an intensive precipitation was positively dependent on the instantaneous soil moisture and suction pressure. A continuous monitoring of these properties made it possible to quantify the potential runoff and the tendency to cause flooding. The analysis also showed an inverse situation in terms of the relationship between retention (and consequently runoff), suction pressure, and soil moisture content. It was therefore necessary to eliminate these by proposing suitable preventive bio-technical measures.

We tested the performance of a formalized digital soil mapping (DSM) approach comprising fuzzy k-means (FKM) classification and regression-kriging to produce soil type maps from a fine-scale soil observation network in Rišňovce, Slovakia. We examine whether the soil profile descriptions collected merely by field methods fit into the statistical DSM tools and if they provide pedologically meaningful results for an erosion-affected area. Soil texture, colour, carbonates, stoniness and genetic qualifiers were estimated for a total of 111 soil profiles using conventional field methods. The data were digitized along semi-quantitative scales in 10-cm depth intervals to express the relative differences, and afterwards classified by the FKM method into four classes A–D: (i) Luvic Phaeozems (Anthric), (ii) Haplic Phaeozems (Anthric, Calcaric, Pachic), (iii) Calcic Cutanic Luvisols, and (iv) Haplic Regosols (Calcaric). To parameterize regression-kriging, membership values (MVs) to the above A–D class centroids were regressed against PCA-transformed terrain variables using the multiple linear regression method (MLR). MLR yielded significant relationships with R2 ranging from 23% to 47% (P < 0.001) for classes A, B and D, but only marginally significant for Luvisols of class C (R2 = 14%, P < 0.05). Given the results, Luvisols were then mapped by ordinary kriging and the rest by regression-kriging. A “leave-one-out” cross-validation was calculated for the output maps yielding R2 of 33%, 56%, 22% and 42% for Luvic Phaeozems, Haplic Phaeozems, Luvisols and also Regosols, respectively (all P < 0.001). Additionally, the pixel-mixture visualization technique was used to draw a synthetic digital soil map. We conclude that the DSM model represents a fully formalized alternative to classical soil mapping at very fine scales, even when soil profile descriptions were collected merely by field estimation methods. Additionally to conventional soil maps it allows to address the diffuse character in soil cover, both in taxonomic and geographical interpretations.