Both the international ISO standard and modern soil classifi cations and databases require soil pH measurement at a 1:5 soil:solution ratio, while the ratio 1:2.5 is still the most commonly used in Poland and other European countries. The transformation of laboratory practices is necessary, but it is also necessary to establish and validate a reliable procedure for converting soil pH at soil:solution ratios of 1:5 and 1:2.5. Based on 200 soil samples representing typical soil types and soil properties of southwest Poland (including arable and forested areas, both in the lowlands and mountains), a general conclusion was derived that pH values measured at soil:solution ratios 1:2.5 and 1:5 in distilled water and KCl solution, respectively, have nearly identical values and do not require conversion in most practical applications. If precise conversion of pH1:2.5 to pH_1:5 is necessary, e.g., for soil database construction or long-term soil quality monitoring, the following equations are suggested: pH_{H2O 1:5} = 0.14 + 0.99*pH_{H2O 1:2.5} and pH_{KCl 1:5} = 0.09 + 1.00*pH_{KCl 1:2.5}, respectively. When the direct conversion of pH_{KCl 1:2.5} to pH_{H2O 1:5} is required, a simple logarithmic model offer precise and reliable transformation: pH_{H2O 1:5} = -1.95 + 11.58*log₁₀(pH_{KCl 1:2.5}). This model makes the archival records still useful, both for international soil classifi cations, background data in the long-term measurement series, and as input data for modern international soil databases.

Europe's largest copper ore tailings impoundment has been considered a potential source of risk for human health, thus leading to the elimination of agricultural production in the surrounding area and its subsequent afforestation. The aim of this study was to analyse the level, spatial distribution and temporal changes in soil and edible plant contamination with trace elements around the impoundment, taking into account the local soil properties. The mean concentrations of Zn, Pb and As (31.5, 19.3 and 3.9 mg kg-1, respectively) were found to be higher than median values in soils of Poland, but they do not indicate soil pollution or enrichment when assessed using the relative geochemical index (Igeo) and enrichment factor (EF). The Cu concentration (mean 25.6 mg kg-1) was significantly higher than the median value for Polish soils, indicating moderate to high pollution/enrichment. A relationship between Cu concentration in topsoil and distance to the impoundment, in particular in its eastern forefield, indicates that this landfill site may be considered the source of soil contamination with Cu. However, both the mean and maximum concentrations of all elements under study, including Cu, were below the legal intervention levels. Long-term topsoil monitoring, although high data variability on permanent plots, has documented stable concentration or slow decrease of element concentration over a period 1995-2016. Cu and Zn concentrations in vegetables from home gardens do not differ from typical values in commercially available products, whereas higher than typical concentrations of Pb and As may result from other local sources of contamination. Low level and stable soil and plant contamination with trace metals justifies continuation of crop production and no need for the further conversion of arable lands into forests. The relatively little negative impact of the tailings impoundment, despite its large dimensions, results probably from implemented effective anti-emission measures.

The aims of the study were to analyse the concentration of nitrate and ammonium ions in soil solutions obtained using MacroRhizon miniaturized composite suction cups under field conditions and to determine potential nitrogen leaching from soil fertilized with three types of fertilizers (standard urea, slow-release urea, and ammonium nitrate) at the doses of 90 and 180 kg ha⁻¹, applied once or divided into two rates. During a 3-year growing experiment with sugar sorghum, the concentration of nitrate and ammonium ions in soil solutions was the highest with standard urea fertilization and the lowest in variants fertilized with slow-release urea for most of the months of the growing season. Higher concentrations of both nitrogen forms were noted at the fertilizer dose of 180 kg ha⁻¹. One-time fertilization, at both doses, resulted in higher nitrate concentrations in June and July, while dividing the dose into two rates resulted in higher nitrate concentrations between August and November. The highest potential for nitrate leaching during the growing season was in July. The tests confirmed that the miniaturized suction cups MacroRhizon are highly useful for routine monitoring the concentration of nitrate and ammonium ions in soil solutions under field conditions.