The aim of the paper was to study N₂O emission from Eutric Histosol irrigated with municipal wastewater. The measurements were performed for three years during the vegetative season on experimental fields. N₂O emission was measured using three kinds of fields, which had been planted with different plants: 1 -Populus alba, Populus nigra; 2 - Salix americana, Salix viminalis and 3 - a mix of grasses:Alopecurus pratensis, Phalaris arundinacea, Festuca pratensis as dominating species. The emission of gases from the soil surface was measured with a chamber technique. Experiments all treatments included irrigation of soil with single (B-600 mm) and double doses (C-1200 mm) of wastewater and studies of soil without wastewater irrigation as a control (A) supplied with water by precipitation and ground water as well as A₁ and A₂ control irrigated with dose of deionised water adequate to doses of wastewater, respectively. Irrigation caused an evolution of nitrous oxide in soil environment that depended on the dose of municipal wastewater. The highest level of N₂O emission was measured for a short period of time after irrigation for every treatment. The maximal daily N₂O emission reached 61.7 mg m⁻² h⁻¹ from soil with grass vegetation on the third day after irrigation with a double dose of wastewater, 54.57 mg m⁻² h⁻¹ from Populus cultivation and smallest on the level 21.01 mg m⁻² h⁻¹ fromSalixvegetation. On the basis of obtained dates the EF - Emission Factor (kg N-N₂O/kg N-NO₃) was calculated in the range 23-12% for Populus, 14.7- 2.4%for mix grasses and 7.8-3.7% for Salix fields.
Flooded organic soils are potentially important sources of greenhouse gases. The effect of soil temperature and moisture on the concentration of N2O and CO2 at two depths of organic soil flooded with two doses of purified wastewater was studied. Nitrous oxide concentrations at the 10-30 cm depth range were generally increased with an increase in soil moisture, showing dependence on the aeration status of soil. The maximum values of N2O concentrations were higher at the 50-100 than 10-30 cm depth range, but a similar pattern of increasing maximum values of N2O concentration with an increasing input of nitrogen in treatments at both depth ranges was observed. The maximum concentrations of carbon dioxide within the 50-100 cm depth range remained at a similar level in all treatments reaching 7.1-7.7%, which indicated weak relations with the input of water and nitrogen at this depth range. We conclude that the N2O and CO2 concentrations at 10-30 cm depths in the examined organic soil flooded with 600mm year-1 of purified wastewater exhibited a similar level as the concentrations in soil watered only by precipitation.
The atmospheric concentration of methane, a potential greenhouse gas, is determined by global balance between sources and sinks. The aim of the paper was to review the recent studies on the natural and anthropogenic sources that are responsible for the increase in the concentration of methane in the atmosphere, focusing on processes of methane formation and oxidation and factors influencing them. Methanotrophic and methanogenic metabolisms are an important part of these researches from the viewpoint of environmental protection. Great variability of soil properties and their interactions affecting the production, consumption and transport of CH4 makes our understanding of these processes still insufficient. Although most research to date has focused on sources of methane emissions, CH4 absorption by oxygenated soil is an important process that significantly reduces emission. The paper describes many soil-related factors affecting methanotrophic activity: particle size distribution, humidity, temperature, pH, oxygen concentration, use of nitrogen fertilisers. Land use has a significant effect on CH4 oxidation in soils, the greatest methnotrophic potential being that of forest soils as compared to meadows, pastures and arable land.
Wheat Triticum aestivum L. cv. ‘‘Banti’’ seeds were treated with magnetic fields (+MF) 30 mT, 50 Hz, 30 s to estimate the influence on seed germination, growth rate of seedlings, and plant tolerance under soil flooding (Fl). MF 30 mT, 50 Hz, 30 s did not stimulate growth processes under optimal soil watering, but flooding suppressed the growth of both (-MF; +Fl) and the (+MF;+Fl)-plants. The content of the thiobarbituric acids reactive substances, reflecting the intensity of oxidative processes, was lower in leaves of (+MF) than in (-MF)-plants. Soil flooding intensified oxidative processes in leaves and roots of the (-MF; +Fl) and (+MF; +Fl)-plants; however, this effect was less pronounced in the latter. Ascorbate peroxidase (APX) activity in leaves and roots of (+MF)-plants was higher than in (-MF)-plants during the first days of the experiment. Flooding increased APX activity in all variants; however, in (+MF; +Fl)-plants it was the highest. Guaiacol peroxidase (GPX) activity in leaves of (+MF)-seedlings was significantly higher than in (-MF)-plants at some periods of plant growth. Thus, seed treatment with MF 30 mT, 50 Hz, 30 s did not stimulate seed germination and growth processes in the seedlings, but resulted in an increase of plant antioxidant potential under soil flooding.
The actual denitrification to N 2 O and denitri- fication capacity to N 2 O after flooding of different soil samples stored for over 25 years in air-dry conditions and fresh, air dried samples were compared in our study. Zero N 2 O release was ob- served from the stored soils but the fresh soil samples had very low actual denitrification to N 2 O. NO 3 - addition significantly increased the amount of N 2 O (denitrification capacity to N 2 O) released after flooding, which depended on the length of storage and type of soils and was much higher in stored soils. Prolonged exposure of the soils to drought conditions caused a greater decrease in the Eh value compared with the fresh soil. The total cumulative release of N 2 O from the stored and fresh soils was correlated with the reduced NO 3 - and organic C content in soils enriched with NO 3 - . Some soils showed the capability of N 2 O consumption. CO 2 release depended on the length of storage and type of soils under flooding after pro- longed drought. On average, CO 2 release was higher from the stored rather than fresh soils. The organic C content in the stored soils was generally lower than in the fresh soils, probably due to the storage effect. The cumulative CO 2 release from the stored soils was well correlated with the organic C while no correlation was observed for the fresh soil samples.
Barley (Hordeum vulgare L. cv. “Rudzik”) seeds were soaked in aqueous 10⁻⁶ М 4-hydroxyphenethyl alcohol (4-HPEA) to estimate its influence on seed germination, growth of seedlings, and their adaptive potential under soil flooding conditions. The adaptive potential of the plants was estimated by the concentration of thiobarbituric acid reactive substances (TBARs) and the activity of guaiacol-dependent peroxidase (GPX). It was shown that the 4-HPEA had a stimulatory action on seed germination, shoot and root growth, and biomass production, expressed to a greater extent in the early stage of plant development. Pre-sowing soaking of barley seeds in aqueous 4-HPEA solution increased plant tolerance to the effect of soil flooding, too.