Browse

51 - 60 of 3,880 items :

  • Geosciences, other x
  • Geosciences x
Clear All

Abstract

To implement the Mehlich 3 method in Polish agro-chemical laboratories, limit values for deficiency of B, Cu, Fe, Mn and Zn in soil for wheat were developed. The values were developed on the basis of 1921 fields with wheat, evenly distributed throughout Poland. Soil samples were collected from these fields in 2016, together with the plants growing on them, at the stage of stem elongation (BBCH 30/31). The concentration of micronutrients was determined in all soil and plant samples. In addition, pH, texture, and the content of organic carbon and available phosphorus were determined in soil samples. Moreover, grain yield after wheat harvest was estimated for all fields. Limit values were developed by two independent methods: 1) the regression equation method and 2) the so-called high yield method. In the first case, the limit microelement concentration in soil was calculated from the equation describing the relationship between the bioaccumulation factor (R/G) and a specific soil feature (n=1921). The bioaccumulation factor is the quotient of the concentration of a micronutrient in a plant (R) and its concentration in the soil (G) determined by the Mehlich 3 method. The equations were constructed using the Stagraphics program. For each micronutrient, 8 models were tested in search for the equation with the highest determination coefficient r2. Limit values were calculated after substituting the critical value of microelements in the plant (R) to the selected model and transforming the equation accordingly. The basis of the second method was to separate the “high yield group” ≥7.0 t ha−1 (n=578) from the entire data set. In this group, lower quintiles for the Mehlich 3-concentration of individual microelements in soil were calculated. The lower quintiles (QU1) were taken as limit values. It was assumed that QU1 is a good indicator of the lowest micronutrient concentration in the soil at which a yield of 7.0 t ha−1 or higher can be obtained. The comparison of the values calculated with the regression equations method and the high yield method showed their similarity, which confirmed the reliability of these values. The proposed values define the limit for low microelements concentration in soil determined with the Mehlich 3 method, below which wheat fertilization with these nutrients is recommended.

Abstract

The aim of the study was to develop limit values for low microelement concentration in the soil, determined with the use of Mehlich 3 extractant for assessing their deficits in rapeseed crops. The values were prepared on the basis of 1944 fields with rapeseed, covering the whole Poland. In 2017, the samplers of Polish agro-chemical laboratories took soil samples and corresponding plant samples at the BBCH 30/31 stage. In the plant samples, the concentration of microelements was determined, and in the soil samples, apart from microelements, also pH, texture and the concentration of organic carbon and available phosphorus, were determined. Moreover, for each field, data on rapeseed yield were collected. Limit values were determined by two independent methods: 1) the method of regression equations and 2) the so-called high yield method. In the first case, the limit microelement concentration in the soil was calculated from the equation describing the relationship between the R/G bioaccumulation coefficient and a specific soil feature (n=1944). The bioaccumulation coefficient is a quotient of the concentration of a microelement in a plant (R) and its concentration in the soil determined by the Mehlich 3 (G) method. Limit values were calculated after substituting the critical concentration of microelements in the plant (R) to the equation, and subsequently, an appropriate conversion of the equation. The second method was based on the separation of a group of high yields ≥4.0 t ha−1 (n=755) from the whole data set. Then in this group, the lower quintiles (QU1) were calculated for the concentration of individual microelements in the soil determined in Mehlich 3 extract and adopted as limit values. It was found that QU1 is a good indicator of the lowest microelement concentration in the soil at which a yield of at least 4.0 t ha−1 can be obtained. The final limit values were worked out by averaging the values calculated by the equations and high yield method and their appropriate correction. In the combined soil sample collections for wheat and rapeseed (n=3865), the values were checked by evaluating the percentage of soils with microelement shortage separately for rape and wheat. The results of this evaluation were compared with the evaluation using the old system based on the 1 M HCl, which did not take into account the plant species.

Abstract

Using the morphology of fin-winged fruits and accompanying foliage, the author characterizes a new fossil species, Dioscorea manchesteri Kvaček, sp. nov. (Dioscoreaceae), recovered from early Miocene deposits of the Most Basin (North Bohemia, Czech Republic). Dioscorea manchesteri matches the extant Dioscorea polystachya Turcz. in its fruit and foliage morphology. This perennial climbing vine native to China now grows throughout East Asia (Japan, Korea, Kuril Islands, Vietnam) in warm temperate to subtropical climate. The record of Dioscorea manchesteri is the first record of this genus in the European Neogene.

Abstract

The aim of the present study is to monitor changes in the location of the groundwater table in the catchment area of the River Gwda within the Quaternary and Neogene water-bearing level over a 35-year period, between 1981 and 2015. In addition, on account of very diverse total annual precipitation levels in particular parts of the catchment, attempts were made to determine the influence of precipitation on the location of the groundwater table. By correlating groundwater level and meteorological parameters (precipitation), it was discovered that precipitation in the previous year made the largest impact on the groundwater table. Moreover, low precipitation totals in the southern part of the catchment are not discernible in groundwater table fluctuations, which is linked to the location of the observation well within the drainage zone as well as to water ascension from deeper aquifers.

Abstract

Fossil bats are described from the karstic deposits of the Erkertshofen 1, Erkertshofen 2 and Petersbuch 2 sites in eastern Bavaria, southern Germany (MN 4). Fossils are discussed with regard to taxonomic, stratigraphic and palaeoecologic significance. The rich fossil material represents at least 12 different bat species belonging to Megadermatidae, Rhinolophidae and Vespertilionidae. The syntopic appearance of four different rhinolophids is demonstrated for the first time for the Neogene bat assemblages of Europe. The remains of Rhinolophidae and Vespertilionidae are the most numerous, of which the proportion of typically early Miocene species Rhinolophus aff. lemanensis, R. dehmi, Hanakia agadjaniani and Miostrellus cf. petersbuchensis are significant. However, there are also remains of R. cf. delphinensis, M. cf. noctuloides, Plecotus cf. atavus and H. aff. antiquus, which are characteristic of the younger middle Miocene faunas of Central Europe. Analysis of the composition of the bat fauna has allowed biostratigraphic correlation of the studied faunas to be estimated at a number of other early Miocene localities in Europe.

Abstract

Fragility curves are useful tools for evaluating the probability of structural damage due to earthquakes as a function of ground motion indices. The force reduction factor (R) is one of the seismic design parameters that determine the nonlinear performance of building structures during strong earthquakes. R factor itself is mostly a function of displacement ductility (µ), natural period of a structure, and soil conditions. A statistical method (Path Analysis) is proposed for the first time to determine the effect of R, µ and T on the column fragility curve parameters of typical box girder, two spans reinforced concrete highway bridge class. An analytical approach was adopted to develop the fragility curves based on numerical simulation. The R, µ and fundamental period T have been used to characterize different bridge configurations. The total, direct, and indirect effects of the variables as having significant effect on fragility curve parameters were identified.

Abstract

Mortar is widely used in the construction industry for different purposes. Its compressive strength is the main parameter which is brought under focus. Compressive strength of mortars depends upon many factors such as water-cement ratio, fine aggregates size, and different curing conditions. This experimental study was undertaken to investigate the effect of GGBFS on compressive strength of mortars under different curing regimes using GGBFS as a partial replacement of cement. A total of 60 cubes of standard size of 2 x 2 x 2 inches were casted in laboratory, out of which 12 cubes each were prepared with 0%, 5%, 10%, 15% and 20% GGBFS replacement for cement. Cubes were cured for 3, 7, 14 and 28 days. Bases on obtained results it is observed that the maximum compressive strength was achieved by sample with 5% GGBFS, although 10% GGBFS samples achieved higher compressive strength than the control sample with 0% GGBFS. Further replacement beyond this value causes reduction in strength.

OPEN ACCESS

Abstract

An assemblage of the early Miocene Sayimys giganteus (Ctenodactylinae, Rodentia) from its type locality Keseköy, and smaller assemblages of Yapıntı and Horlak (Anatolia, Turkey) are described. Almost all Sayimys species are known from small collections of isolated cheek teeth. The very large assemblage from Keseköy is of special interest, because it allows the study of the intra-specific variation of dental morphology: size, the morphological changes through wear and the criteria for recognition of the tooth position of molars. The results have been used to review the formally named Sayimys species and to evaluate the dental features used to define the species. The review of the early and middle Miocene succession of Sayimys in the Siwaliks (Pakistan) resulted in the resurrection of S. minor; S. baskini is considered to be a junior synonym of S. minor. S. sivalensis and S. obliquidens are nomina dubia, and restricted to their holotypes, S. hintoni n. sp. is established for mediumsized Sayimys from the Kamlial, lower Chinji and Manchar Formations and S. chinjiensis is resurrected for Sayimys from the upper Chinji and Nagri Formations. It is suggested that the middle Miocene species Sayimys intermedius and S. assarrarensis from Saudi Arabia are synonymous.