Search Results

You are looking at 71 - 80 of 147 items for :

  • "concentration" x
  • Materials and Applied Sciences x
  • Earth and Environmental Sciences x
  • Refine by Access: All Content x
Clear All

Changes in the K, Ca and Mg contents of the soil solution were examined during the growing period to characterize the nutrient buffer capacity of sandy and clay loam soils in pot experiments set up with Italian ryegrass as indicator plant.  K, Ca and Mg concentrations in the soil solution decreased during the growth due to the nutrient uptake by plants. The normalized values of decrease (expressing the change in the concentration of the given element during unit time) were close to each other for Ca and Mg, while there was a significant difference between the sandy and clay loam soil in the case of K (0.65 and 0.11, respectively). We assumed that the normalized value was inversely proportional to the nutrient buffer capacity of soils.  For the comparison of experiments conducted under different conditions the UPI (uptake index) values were introduced. The UPI value shows to what extent the amount of the given ion calculated from concentration decrease in the soil solution accounts for the amount of element taken up by the plant. The amount of K depleted from the soil solution was 19% of the K amount taken up on the sandy soil, while on the clay loam this value was only 0.8%. Because the UPI values from experiments under different environments are comparable, they characterized the nutrient buffer capacity of soils better than the normalized values of decrease. 

Restricted access

The abundance of some culturable soil microorganisms (bacteria and fungi) was examined at two Hungarian salt-affected soils of the Hortobagy region. In addition to the so-called “helper bacteria” ( Pseudomonas sp., nitrogen fixers), which are mainly attached to the rhizoplane, the abundance of other microbial groups (total number of bacteria, micromycetes, Actinomycetes ) were also assessed. A modified, selective plate dilution assay was used with increasing salt (NaCl) concentrations (5-50 g l -1 media), for assessing the salt tolerant ratio of specific microbial groups.    The type of main salt-specific ions differed at the two sites, resulting more or less stressed pH conditions in the rhizosphere of the most typical halophytes. At Zám mainly the chloride, at Nyírőlapos, however mainly sulphate ions dominated in the samples (at an 80% level), which resulted in a more severe stress situation. Actinomycetes proved to be especially abundant in the salt affected soils examined. In almost all microbial groups, only the high in vitro concentration of salt (50 g l -1 ) reduced the abundance and the colony types of microorganisms. Nitrogen fixers, however were affected at lower salt concentrations and were found to be the most sensitive group at both sites. Variability of the existing colony types of micromycetes was reduced significantly by increasing levels of salinity. Soil- and rhizo-biological characteristics proved to be sensitive indicators of soil quality and environmental conditions. 

Restricted access
Agrokémia és Talajtan
Authors: Krisztina Végh, J. Csillag, A. Lukács, B Panwar, and Gy. Füleky

Potassium uptake is the result of numerous simultaneous processes influencing the potassium dynamics in the rhizosphere.The presented research has focused on plant-soil interactions in the potassium supply of soil in the root environment of maize. It was assumed that: 1. roots promote the mobilization of K by the acidification of the rhizosphere soil, 2. roots increase wetting-drying cycles in their environment, and 3. soil total K content affects K release and fixation in the bulk of soil and the root environment.The promoting effect of root activity was detected on K release from soil when feldspar was added as K source to the root environment. A 2-unit reduction of soil pH multiplied K concentration in the soil solution, depending on the feldspar rate. Feldspar application significantly increased the solubility and release of potassium into the soil solution.The effect of pH reduction on the K concentration of soil solution was several magnitudes higher than that of the wetting-drying cycles both in the untreated and feldspar treated soils.Potassium uptake by maize over two generations greatly exceeded the exchangeable pool in the growing media. As a consequence of the exhaustive K uptake K release slowed down to the soil solution, as reflected in the H2O extractable K and ExK contents.Significant K fixation was detected after the K removal of maize in feldspar treated soils. On the contrary, in the treatments without plants increasing feldspar rates increased both H2O extractable K and ExK contents.One-term Langmuir equation, corrected with the originally sorbed amount of K, was fitted to measured data. The maximum amount of potassium adsorption (Kmax, mg∙kg−1) and the equilibrium constant (k) were calculated. The potassium buffering capacity was estimated at zero equilibrium concentration. Both K buffering capacity and the energy of K fixation were high for the rhizosphere soil. In rhizosphere soil samples the energy of K fixation was one magnitude higher as compared to the bulk soil and decreased substantially with feldspar addition. In soils without plants the k equilibrium constant did not change as the result of drying-wetting process only in the case of the 50% soil/feldspar mixture.In the liquid phase of the soil without feldspar application potassium concentration decreased in the one-year drying-wetting cycle, presumably it got into more strongly bounded forms in the low K status soil. In 50% feldspar enriched soil samples potassium concentration in the soil solution increased, likely as a consequence of a slow dissolution of the K content of feldspar.

Restricted access

The aim of the presented study was to prepare the phosphate sorption isotherms of 20 European volcanic soil profiles and some other Hungarian and German volcanic soils (n = 114) used in the experiment and to establish the soil characteristics determining the phosphate sorption capacity of these soils. The Langmuir isotherm well describes the phosphate sorption of European volcanic soils at bright concentration interval 0–600 mg·dm -3 P. The calculated phosphate adsorption maximum (P max ) is an excellent soil property for characterizing the surface activity of soils developed on volcanic parent material. The calculated phosphate sorption maxima of soils included in the experiment ranged from 0 to 10.000 mg P·kg -1 . Some of the volcanic soils sorbed a high ratio of the added phosphate at low concentrations, while others sorbed somewhat less. The difference in the phosphate binding affinity of soils caused the differences in the shape of the Langmuir adsorption isotherms. P retention % is a WRB diagnostic requirement of andic soil horizon. It was supposed that the phosphate sorption maximum (P max ) gives a better characterization of the surface reactivity of volcanic soils. As it was predicted, oxalate soluble Al is the most important soil property, which dominantly (in 73%) explained the phosphate sorption ability of European volcanic soils.

Restricted access

In the hydrogeologically closed Carpathian Basin subsurface waters have particular importance in the salinization/alkalization processes. In the poorly-drained low-lying areas the capillary flow transports high amounts of water soluble salts from the shallow, „stagnant” groundwater with high salt concentration and unfavourable sodium-carbonate(bicarbonate) type ion composition to the overlying soil horizons. Due to the strongly alkaline soil solution, the Ca and Mg salts (mostly carbonates and bicarbonates) are not soluble and Na + became absolutely predominant in the migrating soil solution which leads to high ESP even at relatively low salt concentration. High Na + saturation of heavy-textured soils with high amount of expanding clay minerals results in unfavourable physical-hydrophysical properties and extreme moisture regime of these soils, which are their main ecological constrains and the limiting factors of their fertility, productivity and agricultural utility. The simultaneous hazard of waterlogging or overmoistening, and drought sensitivity in extensive lowland areas, sometimes in the same places within a short period, necessitates a precise, “double function” soil moisture control against their harmful ecological/economical/social consequences. Most of the environmental constrains (including salinity/alkalinity/sodicity) can be efficiently controlled: prevented, eliminated, or - at least - moderated. But this needs permanent care and proper actions: adequate soil and water conservation practices based on a comprehensive soil/land degradation assessment. It includes continuous registration of facts and changes (monitoring); exact and quantitative knowledge on the existing soil processes, their influencing factors and mechanisms.

Restricted access

., Szabados, I. & Marth, P., 1996. Cadmium content of plants as affected by soil cadmium concentration. In: Soil and Plant Analysis in Sustainable Agriculture and Environment. (Eds: Hood, T. M. & Jones, J. B.) 827--839. Marcel Dekker Inc., New York

Restricted access

To analyze the rhizosphere bacterial communities in wetlands, the total lipid content was extracted from a peat soil and 4 abundant wetland plant roots ( Typha angustifolia L., Salix cinerea L., Carex pseudocyperus L., Thelypteris palustris Salisb.). The separated phospholipid fraction was further fractionated and deriva­tized prior to gas chromatography-mass spectrometry (GC-MS) measurement. In the evaluation only the bacteria-specific fatty acids were used in order to neglect fatty acid information derived from plant root cells. Based on these analyses, a high level bacterial concentration was demonstrated in the rhizosphere, and the relative occurrence of aerobe and anaerobe, Gram positive and negative bacteria, methanotrophs, sulphate reducers and Actinobacteria was determined. Through the PLFA analysis the study of bacteria regardless of culturability was possible.

Restricted access

The first grown deep-rooting crop, maize in 1991 and sunflower in 1998 did not reveal any yield loss on the contaminated soil. The crops responding most sensitively to As were peas, winter wheat and winter barley. In the 4 th year of the trial the peas practically died out on the highest As level.  The “total” As (digested with cc. HNO 3 + cc. H 2 O 2 ) amounted to 70-80% of the As added to the ploughed layer 4 years earlier. The NH 4 -acetate + EDTA soluble As fractions revealed great fluctuations during the sampling time. In the first 4 years the ratio of As detectable in the ploughed layer in this form ranged between 12 and 30%, while in 2000 between 10 and 13%. On the basis of deep profile sampling, it was established that As displayed no significant vertical movement after 10 years, using the HN 4 -acetate + EDTA method (Lakenen & Erviö, 1974). The concentration of As, as a rule of thumb, declined in the direction from root-shoot-leaves-straw-grain in grain crops. The mobility of As is limited within the soil-plant system at this site. Even on the heavily loaded soil, the amount of As in the whole above-ground biomass remained negligible, usually below 5-10 mg As/kg dry matter. Under such conditions, the remediation of soil contaminated with higher loads would theoretically take thousands of years in the case of As via plant uptake. The transfer coefficient, expressing the total straw/soil As concentration by barley, had a value of 0.02. As does not seem to be a very dangerous contaminant either to soil, plants or groundwater. Extreme loads, however, caused phytotoxicity in some crops and resulted in products unfit for animal or human consumption. Soil life was also damaged. Higher As loads decreased nodule formation by green peas, and the endomycorrhizal symbiosis was hindered as well. 

Restricted access

The composition of precipitation and element loads originating from rainwater were examined monthly between 2005 and 2008 at two experimental stations (Őrbottyán in the Danube–Tisza Interfluve region and Nagyhörcsök in the Mezőföld region of Hungary) of the Research Institute for Soil Science and Agricultural Chemistry (RISSAC) of the Hungarian Academy of Sciences. Twenty-five characteristics were analysed: pH, EC, NO 3 -N, NH 4 -N, and concentrations of the main macro- and microelements. The observation represents the dry and wet deposition together. Measurements were carried out by ICP-OES device, with the exception of carbonate, chloride, ammonia and nitrate. The main results can be summarized as follows: – Generally, the lower amounts of monthly precipitation resulted in higher EC, pH; NH 4 -N, Ca, Na and K concentrations. The highest element yields, however, were typical of the wet months. Acidic precipitation (below pH 5) was rich in nitric acid forming NO 3 -N, but poor in NH 4 -N at the Őrbottyán Experimental Station. Emission of the nearby cement works in February and March 2006 caused an order of magnitude higher increase in Ca, Mg, Na and Sr elements as compared to other months, and there was a considerable rise in the NH 4 -N, S, Zn, As, Cr and Pb concentrations of the precipitation (Table 5, 1st half of the year). The pH reached 7.0 at this site. – Depositions were small at the Nagyhörcsök Experimental Station in winter. During the warmer months (May, June and July) the NH 4 -N concentration was 10–20 times higher than the NO 3 -N concentration. The neighbouring fertile and humus rich soils, fertilization, as well as the nearby animal husbandry farm make notable NH 3 emission. In this period the concentration of NH 4 -N and the alkalizing cations Ca and K raised the precipitation’s pH, and the pH increased from January to June. – Aerial deposition varied greatly at both sites, representing the following values in kg·ha -1 ·year -1 unit: NO 3 -N 5–20; NH 4 -N 10–31; total N 30–48; Ca 6–60; K 6–16; S 2–21; Na 4–13; Mg 2–16; P 2–6. The deposition of Zn, Mn, Fe, Cu and B elements at these sites were similar to previous Hungarian and Austrian data. Pb, Ni, Cd and Co depositions, however, were an order of magnitude lower, which demonstrates the positive result of the successful control of heavy metal pollution in Europe since 1990. – Aerial deposition has considerable agronomical and environmental significance. According to the present study, aerial deposition could satisfy 10% K, 15% Mg, 20% P, 30% Ca and N, 40% S element demand of an average 5 t·ha -1 grain and 5 t·ha -1 straw yield of cereals on the chernozem soil of the Nagyhörcsök Station. When using combine harvesting, the straw remains on the site and only the grain is removed, so 25% P, 45% K, 100–300% S and Ca, and several fold of Na-requirement could be covered by the aerial deposition. – Atmospheric deposition may more or less compensate the amount of Mo, Ni and Se built in by grain, while the Zn requirement might be exceeded by about 60%. The deposition of B, Ba, Cu and Sr is several times higher than the amount built in by the grain yield. Aerial fertilization with Cu, Mo, Se and Zn seems to be advantageous, as the site is poor in Zn and Cu, or not satisfactorily supplied with Mo and Se elements. Cd, Hg and Pb loads, however, are environmentally disadvan-tageous, especially on the long-term. The latter harmful heavy metals can also get into waters, on the surface of crops and can cause direct damage to the food chain. – The following minimal – maximal depositions were measured on the two experimental sites: Zn 112–1391; Sr 30–202; Cu 21–153; Fe 42–119; Ba 40–79; Mn 33–62; B 0–33; Pb 2–4; Ni, Cr and Mo 0–6; As 0–4; Hg 0–1.5; Co 0.4–0.7; Cd 0–0.3 g·ha -1 ·year -1 . The pH varied between 4.2 and 7.0 while electrical conductivity ranged between 25 and 1996 μS·cm -1 .

Restricted access
Agrokémia és Talajtan
Authors: György Heltai, Attila Anton, Sándor Hoffmann, Tibor Szili-Kovács, Katalin Berecz, Györgyi Kampfl, Krisztina Kristóf, Erik Molnár, Márk Horváth, and Ágnes Bálint

A Keszthelyen 1963-ban beállított „Szerves- és műtrágyák hatását összehasonlító tartamkísérlet” kiválasztott kezeléseiből vett talajokkal beállított tenyészedénykísérletben és ezzel párhuzamosan a szegélyparcellákból kiemelt bolygatatlan talajoszlopokban vizsgáltuk az ásványi- és istállótrágyák, valamint a talajba bedolgozott növényi szerves anyag hatását a talajlevegőben a tenyészidő folyamán felhalmozódó CO2 és N2O gázok képződésének dinamikájára.A CO2-koncentráció a tenyészidő folyamán a kezdeti stagnálás után egy, vagy több maximum elérése után a kezdeti szintre csökkent mindkét kísérleti rendszerben, s a változás jó korrelációt mutatott a napi középhőmérséklet változásával.A N2O képződésének időbeli változása a talajoszlopokban nem mutatott egyértelmű tendenciát, míg a tenyészedényekben csak a vetést követő 6. napig mértünk koncentrációnövekedést.A bolygatatlan talajoszlopokban a felszíntől 40 cm mélységig a CO2-koncentráció szignifikánsan növekedett, 40–60 cm között már nem változott számottevően. Ugyanez a tendencia mutatkozott a N2O-koncentráció mélység szerinti változásában, de a nagyobb mérési bizonytalanság miatt kevésbé egyértelműen. A tenyészedényekben a 20 cm mélyen elhelyezett csapdákban mért CO2-koncentráció értékek nagyságrendileg megegyeztek a talajoszlopban 20 cm mélyen mért értékekkel. A trágyázatlan kezelésekben a növények jelenléte mind a talajoszlopban, mind a tenyészedényekben növelte a CO2- és a N2O-produkciót. A trágyázási kezelések hatására a talajoszlopokban csökkent mindkét gáz produkciója. Szerves trágya alkalmazásakor növény jelenlétében ez a csökkenés kisebb mértékű volt, mint ásványi trágya esetében. A trágyázási kezelések hatására a tenyészedényekben növények jelenlétében növekedett a talajban a CO2 és N2O produkciója. A növekedés a trágyakezelések termésnövelő hatása sorrendjében istállótrágya < ásványi trágya < (istállótrágya+ásványi trágya) fokozódott.Összegezve megállapítható, hogy a CO2 és N2O gázképződés és a talajból történő kilépés feltételei a bolygatatlan és a művelt talajban eltérnek, s e folyamatra jelentős hatással van a növények jelenléte és anyagcseréje. Kísérleteink eredményeként létrehoztunk egy olyan adatbázist, amelyre alapozva megfelelő matematikai modellek alkalmazásával reálisan becsülhető a mezőgazdasági talajok CO2 és N2O emissziója különböző tápanyagellátási és művelési módok esetén.

Restricted access