The aim of this study to assess interdependence between urban soil pH and its accumulation of heavy metals. The article meant to be a contribution to a better knowledge of peculiarities and diagnostics of urban soil and its anthropogenic transformation. The hypothesis assumes that relationship between urban soil pH and its accumulation of heavy metals may be determined by the origin and age of parent material as well as the nature and degree of the anthropogenic impact. The spatial variability of topsoil pH level was performed in 100 points in eldership of Šnipiškės of the city Vilnius. Laboratory analysis was based on ISO 10390:2005. Samples were collected from 20 cm topsoil layer in the same sampling points where have been analysed concentrations of topsoil chemical elements using optical atomic emission spectrophotometry. The contamination of urban soils exhibits somewhat different compared to agricultural soils. In contradiction to earlier studies in Lithuanian agricultural soils where strong correlation between soil pH and Cr, Cd, Pb, Ni, Cu and Zd found, the conducted analysis shows a statistically reliable, but very weak (<0.3) correlation between the soil pH and concentration of contaminants. The proof to this correlation is provided by an existing relationship between pH and the concentration of copper (r = 0.20), mercury (r = 0.15), strontium (r = –0.12) and the overall contamination index (r = 0.12). The applied statistical analysis, however, failed to reveal the nature of interdependence between the soil pH and its contamination with studied heavy metals there concentration of contaminant chemical elements depends on the pH range of the soil and, conversely, the chemical reactivity of the soil changes affect on the concentration of studied chemical elements.
Conversion of arable soils into other land uses can stabilize and increase accumulation of soil organic carbon (SOC) and in addition prevent deterioration in its properties. The data has shown changes in SOC sequestration in Ap horizon after arable land conversion (1995–2015) into managed grassland, abandoned and pine afforested. SOC in Arenosol topsoil was positively affected by long term fallow and conversion into grassland. Abandoned land and fertilised managed grassland accumulated significantly more SOC, 48% and 38% respectively compared with arable land. In unfertilised managed grassland SOC stocks decreased 2.3% during 21 years, but losses were lower than in fertilised arable land. Pine afforestation of loamy sand helped to reduce the intensity of SOM mineralization compared to arable land. The Ap horizon thickness in pine forest soil increased from 28 to 31 cm during 21 years period. However, SOC stock decreased by 1% due to reduction in carbon concentration.
Ex-arable land-use change is a global issue with significant implications for climate change and impact for phytocenosis productivity and soil quality. In temperate humid grassland, we examined the impact of climate variability and changes of soil properties on 23 years of grass productivity after conversion of ex-arable soil to abandoned land (AL), unfertilized, and fertilized managed grassland (MGunfert and MGfert, respectively). This study aimed to investigate the changes between phytocenosis dry matter (DM) yield and rainfall amount in May–June and changes of organic carbon (Corg) stocks in soil. It was found that from 1995 to 2019, rainfall in May–June tended to decrease. The more resistant to rainfall variation were plants recovered in AL. The average DM yield of MGfert was 3.0 times higher compared to that in the AL. The DM yields of AL and MG were also influenced by the long-term change of soil properties. Our results showed that Corg sequestration in AL was faster (0.455 Mg ha−1 year−1) than that in MGfert (0.321 Mg ha−1 year−1). These studies will be important in Arenosol for selecting the method for transforming low-productivity arable land into MG.
Legumes have a wide range of positive effects on soil properties, including nitrogen and carbon storage, soil structure and the phytosanitary condition of crops. From an agronomic point of view, legumes are most valued for their ability to take up atmospheric nitrogen in symbiosis with nitrogen-fixing bacteria. The aim of this research was to determine the effect of legume residues (peas, fodder beans, narrow-leaved lupins) on the N (Ntotal) and organic carbon (Corg) accumulation in soil and N leaching under temperate climate conditions. The experiment was carried out in lysimetric equipment in 2016–2023. The effect of legumes on Corg and Ntotal accumulation in soil and N leaching were studied in a Fabaceae–Cereals sequence. Three species of legumes—peas, fodder beans and narrow-leaved lupines—were tested; spring barley (Hordeum vulgare L.) was grown as a control treatment. The lysimeter surface area was 1.75 m2 and the experimental soil layer was 0.60 m (sand loam Haplic Luvisol). It was found that after harvesting, more residues were incorporated into the soil with lupines (p < 0.05), which, compared to pea and bean residues, increased Ntotal and Corg concentrations in the soil. There was a strong correlation (r = 0.95) between the Ntotal concentration in the soil and the N amount incorporated with residues. Mineral N released during residue decomposition was leached from the humic horizon under conditions of excess moisture in the autumn–winter period and increased the nitrate concentration in the lysimeter water. The increase in concentration was recorded within 5 to 6 months after the application of the residues. As a result, the N leaching losses increased on average by 24.7–33.2% (p < 0.05) during the year of legume cultivation. In the following year, after legume residue incorporation, the effect of residues on nitrate concentration and N leaching decreased and did not differ significantly from that of barley residues.
This study aims to determine the differences in the organic carbon, humic acid (HA), and fulvic acid (FA) concentrations in the A and AB horizons, depending on land use, in order to determine the influence of the land use on the soil organic carbon (SOC) sequestration rate in the A horizon, and to assess the impact of the land use on the quality of the humic substances (HS) (the humification rate (HR) and the HA/FA ratio). On the basis of the data of 1995–2018, it would be expedient to convert cropland (CL) areas to fertilized managed grassland (MGfert) in order to increase the SOC accumulation (28%) in the Arenosol. In the unfertilized managed grassland (MGunfer) areas, the SOC accumulation in the A horizon was similar to that in the MGfert (p > 0.05); however, significantly less (−45.0%) HAs were formed, the HR decreased 2.8%, and the HA/FA ratio was 1.12%. This means that less stable humic substances were formed in the MGunfer soil. In the Arenosol, the fastest SOC sequestration took place in the AL and PP areas, the annual SOC stocks increased by 393 and 504 kg ha−1 year−1, respectively, and the HR increased to 19.1–21.3% (CLfert: 11.9%). However, these types of land use produce more FAs (14.5 and 32.5% more, respectively, compared to the MGfert, and 36.3 and 57.7% more, respectively, compared to the CLfert), which can lead to soil acidification and can accelerate eluvial processes. Because of the faster leaching of the FAs from the upper layers of the A horizon to the AB horizon, the humus type changes from humate–fulvate in the A horizon, to fulvate–humate in the AB horizon.
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