Fulltext search in archive

Dynamics of the plant-available potassium (K) has been studied in polyfactorial long-term fertilization experiments since 1980. The fertilization scheme includes 10 combinations of K muriate and farmyard manure application rates (annually 0-230 kg K/ha). At medium treatment (annually 153 kg K/ha), the K balance within an 8-year crop rotation reflected crop specific K application rates with positive annual balances in years of growing silage maize and sugar beet (high K input), and negative in two years of growing alfalfa. Available K clearly corresponded to the dynamics of the K balance, with statistically significant fluctuations from 88 to 149 mg K/kg within one crop rotation cycle. Periodic fluctuations of available K induced by crop rotation were observed also in non-fertilized treatments. The variability of available K contents was influenced primarily by crop plants and experimental unexplained factors; interannual weather fluctuations and field differences were of low significance. In the paper, the importance of interannual K dynamics for the construction of correct long-term time trends is shown and discussed.

The experiments were conducted to study the effects of arsenic-contaminated irrigation water, zinc and organic matter on the mobilization of arsenic in an Aeric Endoaquept in relation to rice (cv. IET 4786). The results show that the amount of extractable arsenic increased with the progress of submergence decreased with zinc application. The magnitude of such decrease varied with the Zn amount, being greater (0.70 to 1.08 mg/kg) in the treatment where zinc was applied at the rate of 20 mg/kg. With regards to organic matter application, the arsenic content in soil markedly decreased, especially with farmyard manure application. The results of the greenhouse experiment with exposure of graded doses of arsenic to rice suggest that the upper toxic limit of arsenic in soil was 10 mg/kg for rice. The results of the field experiment show that the grain yield of continuous flooding (4.84 t/ha) and intermittent flooding up to 40 days after transplanting followed by continuous flooding (4.83 t/ha) with the application of ZnSO₄ at the rate of 25 kg/ha did not vary significantly. The lowest grain yield (3.65 t/ha) was recorded in the treatment where the intermittent flooding was maintained throughout the growth period without the application of zinc. The amount of arsenic was, however, much lower in the treatment where intermittent flooding was maintained throughout the growing period combined with zinc sulphate application.

Actual yields of maize harvested by farmers are at level much below attainable yield potential of currently cultivated varieties. Among many growth factors zinc was recognized as one of main limiting factors of maize crop growth and yielding. This hypothesis has been verified within a three-year field study, where zinc fertilizer was applied to maize plants at the 5^th leaf stage. Maize crop responded significantly to zinc foliar application in two of three years of study. The optimal rate of zinc foliar spray for achieving significant grain yield response was in the range from 1.0 to 1.5 kg Zn/ha. Grain yield increase was circa 18% (mean of three years) as compared to the treatment fertilized only with NPK. Plants fertilized with 1.0 kg Zn/ha significantly increased both total N uptake and grain yield. Yield forming effect of zinc fertilizer revealed via improvement of yield structure elements. The number of kernels per plant showed the highest response (+17.8% as compared to the NPK plot) and simultaneously the highest dependence on N uptake (R² = 0.79). For this particular zinc treatment, however, the length of cob can also be applied as a component of yield structure significantly shaping the final grain yield.

In the present study, the effects of fungicide Aliette WG 800 [80% fosetyl-Al (aluminium tris-o-ethyl phosphonate)], widely used against Phytophtora infestans on tomatoes grown in greenhouse in Turkey, were studied on the morphology and viability of tomato (Lycopersicon esculentum Mill.) pollens. The fungicide was applied to tomatoes grown in greenhouse at recommended dosage (200 g/100 l water) and at double the recommended dosage (400 g/100 l water). The fungicide caused changes in the morphological structures of tomato pollens. Some pollen morphological structures that are not observed in the control group were encountered in the pollens in equatorial view and in polar view at 200 g/100 l treated groups. On the other hand, pollen viability level decreased as the dosage increased. Especially, non-viable pollen types such as wrinkled pollen or pollen with abnormal shape were encountered in the fungicide groups. It was expected that the pollen fertility as well as yield would decrease in future.

Simple balance of Cd input by different treatments and removal by agricultural crops was investigated in an ongoing precise long-term field experiment with application of sewage sludge (SS), farmyard manure (FYM), and mineral fertilizers (NPK). Potatoes, wheat and barley were grown in a rotation at 4 experimental sites of the Czech Republic with the aim to assess the risk of Cd accumulation in soil and plants under different soil and climate conditions. The results showed significant differences in Cd content of the input materials used, and in Cd inputs to soils under different fertilization managements. Three applications of sewage sludge during 1996-2005 resulted in total addition of 110 g Cd/ha into soil, which was by one order of magnitude higher than Cd addition in FYM or NPK treatments. From the total amount of sludge-borne Cd, only small portion was removed by harvests of crops (approximately 3.5%). Soil conditions significantly affected Cd input-removal balance. The highest Cd removals were obtained on soils with the lowest pH. The highest Cd removal was achieved by potato tubers followed by wheat and barley plants. The results showed that the risk of Cd accumulation in soils is high, especially with repeated sludge applications.

Net N mineralization rate (NMR), net N consumption rate (NCR), microbial biomass carbon (MBC) and nitrogen (MBN), potentially mineralizable N (PMN) and mineral N (N-NH⁺₄ and N-NO^-₃) were measured in paddy soil at five growth stages of rice to determine the effect of long-term fertilization in subtropical China. The studied long-term treatments included CK (no fertilization), N, NP, NPK and NPK + OM (NPK plus organic manure). The NPK + OM treatment gave the highest values of the measured variables among all treatments. There was no significant difference in other treatments except for mineral N and PMN at early growth stages. All these variables were generally highest at transplanting stage as two thirds of fertilization was applied as basal fertilizers and the rice uptake was low. Then they decreased or leveled off with the rice growth stages except for MN in all treatments. Stepwise regression revealed that NMR was significantly correlated with MBC and N-NH⁺₄ (R² = 0.954, P < 0.01) at all rice growth stages. So, mineral plus manure fertilizer application and more mineral fertilizer as topdressing were recommended in subtropical paddy soil.

Soils were sampled from the plots with four variants of fertilisation: Nil - without fertilisation, NPK - mineral fertilisation, FYM - farmyard manure, FYM + NPK - farmyard manure with mineral fertilisation, and two variants of crop rotation: field IV - classical 9-year crop rotation, field B - 2-year rotation of alternative growing. Determination of urease, CFU of Azotobacter spp. and potential nitrogenase activity was conducted during the period 1999-2004. The urease activity was positively affected by manure fertilisation (FYM) and by the combination of FYM + NPK. The statistically significantly highest counts of Azotobacter spp. and the highest nitrogenase activity were determined on field B in variants FYM and FYM + NPK. The results show that there was a higher amount of accessible nitrogen present on field IV than on field B. This might explain the lower counts of Azotobacter spp. and therefore the lower nitrogenase activity. According to our results, activity of urease, CFU of Azotobacter spp. and potential nitrogenase activity are very closely connected with N inputs.

The objective of this study was to evaluate the influence of organic (cattle manure) and inorganic fertilizers [composite NPK (15:15:15)] and natural zeolites on soil properties, vegetative growth and yield of apple plants grown on vertisol under Cacak conditions (Western Serbia). The results showed that the combined fertilization induced a decrease in acidity, an increase in humus content, a partial increase in total nitrogen (NTOT), and, primarily, a rise in available phosphorus (P) and potassium (K) levels. A highly significant (P < 0.01) interactive effect of the apple cultivars and nutrients on one-year-old shoot length and trunk cross-sectional area (TCSA) and a significant effect (P < 0.05) on yield per tree and yield per hectare were determined.

Sustainable land management requires that water and matter (nutrients and base cations) are efficiently recycled within ecosystems so that irreversible losses of matter from topsoils are minimised. Matter losses are connected to water flow. The division of water into evapotranspiration that is loss-free, and seepage to groundwater or surface water flow that both carry material losses, is decisive in determining total losses of dissolved matter in a given catchment. Investigations of areal matter losses confirmed the instrumental role of vegetation cover. Areal matter losses measured in agricultural catchments in Germany were on average between 1-1.5 tons of dissolved matter per ha per year, i.e. some 50 to 100 times higher than those from unmanaged land in a virgin forest. Such high losses continuously reduce soil fertility and can hardly be compensated by fertilisation. Some suggestions on how to achieve sustainable management of agricultural land and maintain high soil fertility are presented - the priority is to close water and matter cycles through the incorporation of more natural vegetation cover into our landscapes and to restore the energy-dissipative properties of ecosystems.

Plant root and shoot dry weight, leaf relative water content (LRWC) and chlorophyll content were reduced by 30%, 21%, 15%, 34%, respectively, at 40mM NaCl as compared to non-salt stress conditions. However, membrane permeability (MP) of plant increased (85.0%) with increasing salinity. Foliar nutrient application (FNA) alleviated deleterious effects of salinity stress on growth and this effect was statistically significant. The highest alleviation effect of FNA at 40mM salinity stress was observed in the case of 10mM foliar KNO₃ and Ca(NO₃)₂ application, resulting in increase in plant root dry weight (50%), shoot dry weight (50%), LRWC (8.2%) and MP decrease (27.4%) at 40mM NaCl. Phosphorus, Fe and Zn contents in shoots and roots of plants also increased with FNA treatments, but they were still much lower than those of non-salt stress treatment. Sulphur, P, Fe and Zn contents of shoots reached similar values as in non-salt stress treatment when KNO₃ was applied, whereas Fe, Mn, Zn, and Cu contents of roots reached the values of non-salt stress treatment when Ca(NO₃)₂ was applied.

The effects of different concentrations of copper (0-800 μmol) on growth, protein contents, peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL) in Jatropha curcas L. seedlings were assessed by means of pot experiments. Results suggested that increased copper concentrations lead to decreased shoot elongation and seedling biomass. Protein content in the leaves and roots reached their highest levels at the copper concentrations of 400 μmol, while the highest protein content in the stem was observed at 800 μmol copper. POD activity in leaves and stems was unaffected at low copper concentrations, but showed a considerable variation at high copper concentrations. In roots, the highest POD activity was observed at 200 μmol copper. Under copper stress, SOD activity in leaves increased concomitantly with increasing copper up to 400 μmol, and SOD activity in stems and roots showed a slight increase. Catalase activity significantly elevated in leaves and roots but showed no significant changes in stems of the seedlings exposed to copper. A gradual increase of PAL activity in leaves and roots at the copper concentration of 400 and 200 μmol was observed, while PAL activity remained unchanged in stems.

The CULTAN (Controlled Uptake Long Term Ammonium Nutrition) system is based on one-time injection of the whole dose of nitrogen required for the vegetation period. The effect of this method on yield and grain quality of winter wheat was observed in a 2-year small-plot trial at 4 different experimental sites in the Czech Republic. The experiment comprised two treatments with the total amount of nitrogen applied during fertilization of 150 kg N/ha. At the CULTAN treatment the whole dose was applied all at once using the GFI 3A injection machine (Maschinen und Antriebstechnik GmbH Güstrow), whereas at the control treatment, the dose was divided into three applications. The average grain yield of winter wheat in 2007 was 9.56 t/ha (control) and 8.78 t/ha (CULTAN); in 2008 it was 9.91 t/ha (control) and 9.63 t/ha (CULTAN). The differences in 2008 were not statistically significant. The contents of nitrogen and gluten were significantly lower at CULTAN treatment in both years. The values of falling number, Zeleny test and bulk density were generally similar at both treatments.

Ecobiological study of medicinal plants includes the analysis of particular soil features and the ecological indexes of plant species as site indicators. Two experimental serpentine areas in northwest and central Serbia were selected to identify the potential limiting factors for medicinal plant harvesting. Soil analysis is done according to ICP methodology - ICP Forest Manual, Part III, Soil Sampling and Analysis (1998). Floristic and phytocoenological investigations were carried out by Wasthoff-van der Maarel (1973). The assessment of soil quality is based on the calculation of indicator values of available nitrogen (N), heavy metals, and the sensitivity to acidification. According to our results, N (12.1-17.5), acidification (7-12), and indicator values for some heavy metals (0.3-46.5) show a low biological availability. Medicinal plant species at the investigated areas have low values of ecological indexes: N (2.41-2.82), moisture (2.45-2.70) and soil acidity (3.35-3.70). Hydrothermic conditions indicate the predominant presence of sub-xerophytes, semi-sciophytes and mesothermic species. These types of plant species are recommended for exploitation.

The results of three-year trials (1999 to 2001) conducted with six winter wheat varieties in which was investigated the effect of sites, years and varieties on the final grain yield and technological quality showed statistically significant differences (LSD, 95%) among sites in grain yield and these parameters of quality: test volume mass, wet gluten content, sedimentation test, protein content, falling number and flour water absorption capacity. As to the quality, the Žatec site showed itself as generally most suitable, and the Jaroměřice site as the least suitable one. Climate conditions showed a statistically significant effect (LSD, 95%) on grain yield and all quality parameters, beside the percentage of complete grains and swelling capacity of gluten and falling number, which were insignificant. The most favourable weather conditions, a lot of precipitation and high temperature in the course of ripening from three years were proved in the year 2000. Among the varieties were statistically significant differences (LSD, 95%) in grain yield and these parameters of quality: test volume mass, thousand grain weight, ash content, percentage of complete grains, sedimentation test, protein content, reologic properties of dough and baking tests. From the six varieties the best profits were shown from variety Sulamit (loaf volume 595 ml/100 g of flour), the worst was Semper (loaf volume 543 ml/100 g of flour) and Vlasta (loaf volume 532 ml/100 g of flour). The best grain yield was in 2001 (average of sites 8.84 t/ha) and the variety Semper had the highest grain yield of 9.17 t/ha, that is higher at 13.41% compared with Sulamit (7.94 t/ha).

The paper deals with the possibilities of arsenic analysis in the soil. The aim is the selection and verification of the methods for analysis of As in the soil, which seem to be suitable for risk evaluation based on the increased As soil load. Economical and analytical availability of the methods is an important criterion. A sample set of 6 heavily contaminated soils was used to compare application potential of prevalent as well as less common procedures for determination of arsenic forms in soils. The results showed that substitution of analytically more demanding As total content analysis and sequential analysis for simple extraction using one-off agents seemed to be promising in many cases. The comparison and evaluation of statistical correlation of used methods of As analysis in the soil was realised. The results suggested that using the combination of simple 1M NH₄NO₃ extraction and determination procedure for amorphous Fe forms in the soil (the Tamm method) was suitable for the risk assessment stemming from the As contamination without necessity of the application of more complicated sequential extraction procedures.

The apparent uptake of mineral nitrogen (N_min) from top- and subsoil layers during the growth of winter wheat (Triticum aestivum L.) was studied in Prague-Ruzyne on clay loam Chernozem soil in years 1996-2003. Two (N0, N1) and three treatments, unfertilized (N0), fertilized with 100 kg (N1) and 200 kg (N2) nitrogen per hectare were observed in years 1996-2000 and 2001-2003, respectively. The apparent uptake of nitrogen from soil layers was calculated from the changes of N_min content between sampling terms. Most of available mineral N in the soil down to 90 cm was almost fully depleted between tillering and anthesis in treatment N0. The uptake from subsoil layers was delayed and it continued during the period of grain filling in fertilized treatments. Nitrogen fertilization reduced utilization of N from subsoil. The apparent uptake of N from the zone 50-120 cm ranged from 21 to 62 kg N/ha in N0 and from 15 to 60 kg N/ha in N1 in years 1996-2000. In years 2001-2003 the corresponding values (50-130 cm) were 24-104 kg, 43-130 kg and 29-94 kg N/ha in treatments N0, N1 and N2, respectively. The uptake from 120 (130)-150 cm was around zero in a half of experimental years, and it reached at maximum 12 kg/ha in N0 in 1997. There was a strong linear relation between the amount of N_min in spring and the depletion of nitrogen from the zone 50-120 (130) cm, R² = 0.94, 0.91 and 0.99 in N0, N1 and N2, respectively.

Several fusarioid microorganisms were isolated as potential pathogens of hop (Humulus lupulus L.) but their virulence was not proved in inoculation trials in field conditions. Molecular search for other possible pathogens was then performed. Using terminal restriction fragment length polymorphism (TRFLP), Gibberella pulicaris (anamorph: Fusarium sambucinum) was identified as a probable cause of the hop wilting. The primary cause of the disease is wounding of hop crowns by feeding of rosy rustic moth (Hydraecia micacea) caterpillars or by defect pruning and other unfavourable circumstances. The specific primer HLf1 was designed that can be used to detect the pathogen in soil and in damaged plant tissues.

In this work, the effects of double, triple and quadruple combinations of gibberellic acid, kinetin, 24-epibrassinolide and polyamines (cadaverine, putrescine, spermidine, spermine) on the stomata movements in the leaves of barley seedlings grown under saline conditions were studied. In the control seedlings, the stomata number, stomata index and stomata length increased in the upper surfaces of leaves in comparison with their lower surfaces. In addition, the epidermis cell number in the leaves of control plants were fewer in the upper surface than that in the lower surface, but the stomata were statistically in the equal width in both surfaces. As for the applyings, they generally decreased stomata number, stomata index, stomata length and epidermis cell number, while they increased the stomata width in the upper and especially in the lower surface according to the control. The growth regulators used may have served to adaptation of barley seedlings to saline conditions by causing a decrease in most of the mentioned parameters.

he study was undertaken to determine a possible role of polyamines (putrescine, spermidine, spermine) as antioxidants in salt tolerance of Chamomilla recutita and Origanum majorana. Salinity generally induced variable changes in growth, contents of oil and flavonoids of both plants; foliar application of any polyamines counterbalanced the effects of salinity. In general, the degree of stimulation differed according to the type and concentration of the used additive and the type of the plant.

Microbial activities and counts of microorganisms were monitored as a part of research projects at 11 localities on arable land of different soil types during the years 2002-2006. The counts of microorganisms (total bacteria count, actinomycetes, micromycetes, Azotobacter, oligotrophic and spore-forming bacteria) and microbial activities (respiration, ammonification and nitrification tests) were evaluated using summary statistics, analysis of variance and correlation coefficients. The average counts of microorganisms corresponded with usual counts of microbes in arable soils. There were only some differences among localities in Azotobacter counts. Soil respiration is very often used as an indicator of soil microflora activity. Average values of basal respiration were slightly lower (0.45 mg CO₂ /h per 100 g dry soil) than usual values, potential respiration with glucose (G) or with ammonium and G (NG) responded to usual values (average G 4.27, NG 9.53 mg CO₂ /h per 100 g dry soil). All activities (except actual ammonification) were higher in spring season, but the differences were not significant. There were significant differences in correlation coefficients among the selected criteria; 66% from the total number of correlation coefficients were non-significant, 34% were significant (13% of them was at the significance level 0.05, 10% P < 0.01, and 11% P < 0.001).

The effect of nitrogen fertilization on root length (RL) distribution of winter wheat (Triticum aestivum L.) was investigated. The study was conducted in Prague-Ruzyne on clay loam Chernozemic soil in the years 1996-2003. Two (N0, N1) and three (N0, N1, N2) treatments, unfertilized (N0), fertilized with 100 kg (N1) and 200 kg N/ha (N2) were studied in 1996-2000 and 2001-2003, respectively. Nitrogen rate 100 kg/ha had no effect on RL in soil layers (P > 0.1) in years 1996-2000 and 2002-2003 and there was not significant interaction between N treatment and soil layer except for year 1998 (P < 0.01). Nitrogen fertilization affected RL distribution significantly (P = 0.013) only in 2001 due to reduction of root growth in subsoil layers in treatment N2 (200 kg N/ha) in comparison with N0 and N1. The effect of N fertilization on total RL in rooted soil volume was insignificant. There was a significant effect of year on total RL (P < 0.01) but not of interaction of year and N treatment. Roots reached, with the exception of two years, the depth between 100 and 130 cm. Nitrogen fertilization (N1) had no effect (P = 0.59) on rooting depth (RD) in years 1996-2000 but there was a significant effect of interaction between year and N fertilization on RD (P < 0.01). In the second experimental series (2001-2003) N fertilization rate 200 kg N/ha significantly reduced maximum RD (P < 0.01) in comparison with N0 and N1. The year had highly significant effect on RD.

The effect of 24-epibrassinolide and 28-homobrassinolide on seed germination and seedling growth of radish (Raphanus sativus L.) was studied under cadmium toxicity. The impact of brassinosteroids (BRs) on free proline levels and the activity of antioxidant enzymes catalase (CAT; EC 1.11.1.6), peroxidase (POD; EC 1.11.1.7), superoxide dismutase (SOD; EC 1.15.1.1), ascorbic peroxidase (APOX; EC 1.11.1.11) and guaiacol peroxidase (GPX; EC 1.11.1.7) in radish seedlings under Cd toxicity was evaluated. The effect of BRs on the activity of ascorbic acid oxidase (AAO; EC 1.10.3.3) and lipid peroxidation in radish seedlings challenged with Cd stress was also investigated. BRs supplementation alleviated the toxic effect of the heavy metal and increased the percentage of seed germination and seedling growth. Out of the two substances, HBL was found to be more effective than EBL in stress alleviation. HBL (3µM) alleviated the toxic effect of the heavy metal and increased the percentage of seed germination by 57% over Cd and 20% over unstressed control. Similarly supplementation of HBL (3µM) caused an increase of 156%, 78% and 91% in length, fresh weight and dry weight of seedling, respectively, over Cd treatment alone. The amelioration of seedling growth by BRs under metal toxicity was associated with enhanced levels of free proline. The activities of antioxidant enzymes CAT, SOD, APOX and GPX were increased in the seedlings from treatments with Cd along with BRs. Brassinosteroid treatment reduced the activity of POD and AAO in heavy metal stressed seedlings. Lipid peroxidation induced by Cd was found reduced with the supplementation of BRs. The results obtained in the study clearly indicated the ameliorative influence of brassinosteroids on the inhibitory effect of Cd toxicity.

Formerly arable luvic chernozem set aside for ten years (1997-2006) with different herbaceous cover (grass, legumes and their mixtures) and agronomical practices (mulching and cut/harvesting) was studied. The experimental plot was maintained as black, spontaneous and controlled fallows from 1997 until July 2003 (BD period). In July 2003 the plots were desiccated by glyphosate herbicide and were run as a black fallow until August 2004 (AD). The last period (AG) was characterized by monoculture of Italian ryegrass cut/harvested twice a year until October 2006. The experimental soils were characterized with 18 parameters. Mulched plots in all periods (BD, AD and AG) were evaluated as highly microbial active plots. The black fallow (BD) permanently maintained by glyphosate herbicide was the lowest in biological parameters. The desiccation caused a highly significant increase (P < 0.01) of nitrates in topsoil, but in following period (AG) their significant decrease was detected. Desiccation enhanced carbon immobilization into microbial cells especially on mulched and cut/harvested sites (BD, AD). Due to mulching accumulation of soil organic matter highly significantly increased (P < 0.01). This induced a highly significant (P < 0.01) increase in the basal respiration (AD, AG) as the soil organic matter accumulated in the period BD was intensively mineralized.

Seeds are the primary sinks for photosynthates during reproductive growth. Variation in light intercepted during and after seed initiation has been found a major environmental determinant of soybean [Glycine max(L.) Merrill] seed size. We investigated the influence of light enrichment and shading on seed growth rate, effective filling, cotyledon cell number, cell volume and endogenousABA concentrations of cotyledons/testas during seed filling of soybean. Evans, an indeterminate Group 0 soybean, was subjected to light reduction and enrichment treatments from the beginning of pod formation until final harvest for two years inMassachusetts. Higher rates of seed growth, greater seed dry weight, and higher cotyledon cell number were all observed with light enrichment. There was a reduction in seed growth rate and cotyledon cell number, along with a significant lowering of endogenousABA levels in testa and cotyledon with shade. The level ofABAin cotyledon during seed development was significantly correlated with seed growth rates only under shade treatments. Both the growth rates and seed filling duration were influenced by variation in light interception by the soybean canopy. The effects of varying light treatment on seed size, within one genotype, were most likely due to the differences in seed growth rate and cotyledon cell number.

The effect of three seedling treatments: T₀, normal germination; T₁, cotyledons removed; T₂, cotyledons removed 5 days earlier than in T₁; and two phosphorus levels (P₀ and P₃₀) on nodulation and nodule function in soybean [Glycine max (L.) Merr.] were investigated in nutrient solution culture. The number of nodules formed at P₀ was in the order T₂ > T₀ > T₁, but it was T₀ > T₂ > T₁ at P₃₀. Nodule dry weight per plant had the same tendency as the nodule number. Nodule size (dry weight per nodule) in seedlings ranged from 0.601 to 1.089 mg in the order T₀ > T₁ > T₂, regardless of P level. For example, nodule size in T₀ was larger by 86% and 52% than T₂ at P₀ and P₃₀, respectively. Furthermore, regardless of P level, a specific acetylene reduction activity (ARA, µM C₂H₄/h/g nodule) increased with P content in seedlings, but no significant difference was found (P < 0.05). Leghemoglobin (Lb) content was not significantly affected by P level; however, seedlings (T₀ and T₁) significantly affected the Lb content per unit plant biomass (P < 0.05). All these results suggest that seedling P content plays a key role in nodulation and nodule function of soybean.

Urbanization has drastically changed soil properties, and an assessment of these changes is essential for soil management and soil health. The activities of urease, acid phosphatase, invertase and catalase, soil organic matter, pH, electrical conductivity (EC) and clay (< 0.01 mm) content of urban soils under two land-uses in the central built-up area of the Shenzhen city were investigated, and multivariate analysis was used to study the relationship between soil enzymes and soil physical-chemical properties. The results showed that invertase activity in roadside soil was significantly higher than that in urban park soil, whereas catalase activity was significantly higher in urban park soil. Soil organic matter had significant positive correlation with activities of invertase, urease and acid phosphatase but not with catalase. Soil pH had a significant negative direct effect on urease and acid phosphatase activity, but the effect was counteracted by positive indirect effect of soil organic matter. Soil EC had a positive direct effect on activities of catalase and there was a significant correlation between soil EC and soil catalase activities. Soil organic matter, soil pH and EC were the major factors influencing activities of soil enzymes.

By reference to the Eternal Rye trial in Halle, Germany, as an example, it is demonstrated that long-term trials provide indispensable information for contemporary and future land use research. These trials serve as tools for the examination of cultivation measures or the effects of climate on nutrient dynamics and mobilization, microbial biodiversity, mineral composition or soil formation processes. They are therefore essential for the evaluation of land-use strategies or climatic change and, because of that, can provide more accuracy in related political considerations.

This paper presents the results of a three-year research on the effect of perforated polyethylene foil and polypropylene fibre covering at various lengths of plant cover period (2 and 3 weeks after plant emergence) on the assimilation leaf area of early potato cultivars. In the case of plant covering for 2 weeks after emergence the assimilation leaf area and leaf area index (LAI) at the moment of cover removal were on average 2 times higher than in the cultivation without covering; at the 3-week period of plant covering they were almost 1.7 times higher. A higher favourable effect of covering was obtained in the year with the lowest air temperature in May. The use of the covers at that time increased the assimilation leaf area and LAI 2.5 times and 3 times, respectively. The research showed no significant effect of the type of cover used on the assimilation leaf area and LAI; however, the specific leaf area (SLA) was higher with the use of polypropylene fibre.

This study aims to investigate the changes in isotope ratios in foliage and soils of the two spruce forests [Picea abies (L.) Karst.] differing greatly in their atmospheric N deposition and climatic conditions. As expected, both N concentrations and ¹⁵N values in both needles and litter were found to be significantly higher in the Solling stand (N-saturated) compared to the Hyytialä stand (N-poor). For the N-limited site (Hyytialä plot), a typical vertical gradient of the soil ¹⁵N-enrichment (both in organic and mineral soil) was observed. The N-saturated site (Solling) differs from the N-limited site (Hyytialä) with respect to the ¹⁵N abundance trend in organic layer. In the upper organic layer up to O-f horizon, i.e. mor layer (0-3.5 cm depth) of Solling plot, there is almost a trend of slight soil ¹⁵N-depletion with increasing depth, and then there is a ¹⁵N-enrichment from O-h horizon (humus layer) of organic layer to mineral soil horizons. This is explained by the presence of prominent NO₃^- leaching at this plot

The effect of osmotic stress on oxidative injury, compatible solutes content and water relations was investigated in two maize cultivars (Zea mays L. cv. Ankora - drought-sensitive and cv. Nova - drought-tolerant). Relative water content in leaves of both cultivars decreased after drought treatment, leaf water loss of sensitive cv. Ankora was higher than that of cv. Nova. The 24 h water stress induced by 0.3M sorbitol (-1.4 MPa) resulted in a damage of cell membranes. Lipid peroxidation rose in all studied organs of cv. Ankora and electrolyte leakage in roots of cv. Ankora was much higher than in cv. Nova. Similarly, proline content increased significantly in all studied organs of cv. Ankora. Content of soluble sugars increased in all studied organs of both cultivars, but the mesocotyl of cv. Nova accumulated the highest amount of sugars. The electrolyte leakage was the highest in the roots of both cultivars. Osmotic stress had deep influence predominantly on the roots of both cultivars. It is apparent that stress impact on the drought-sensitive cv. Ankora was deeper than on the drought-tolerant cv. Nova.