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Plant demand for molybdenum is small, but it is a micronutrient of great significance for the proper development and functioning of organisms. Its deficiencies may disturb the absorption and influence of other elements on living organisms. The availability of molybdenum for plants depends on many factors, including the fertilization used. The aim of the study was to determine the effect of liming and differentiated NPK mineral fertilization against the background of a constant level of Mg fertilization on the molybdenum content in potato tubers and in the green mass of fodder sunflower grown on loess soil in four and three rotations, respectively. The research was carried out as a long-term experiment on a field owned by the University of Rzeszow in Krasne near Rzeszow (Rzeszow Foothills). The soil on which the research was carried out was a Haplic Luvisols formed from loess. The experiment was set up in a random sub-block design with four replicates. The first variable factor was liming (A2 ) or its lack (A1 ), while the second one consisted of different doses of mineral fertilization (14 fertilizer objects) with constant magnesium nutrition. Triple superphosphate contained significant amounts of molybdenum: from traces to 18 mg Mo kg-1. Plant samples were collected after potato and sunflower harvest from four rotations. Molybdenum in dry plant material was determined colorimetrically with the thiocyanate method. The molybdenum content in potato tubers ranged from 0.147 to 0.573 mg kg-1, being much higher in the green mass of fodder sunflower, where it ranged from 0.467 to 2.280 mg kg-1. Liming increased the molybdenum content in the green mass of fodder sunflower. This treatment caused significant changes in the content of this element in potato tubers. The mineral fertilization of NPK (regardless of liming) increased the molybdenum content in the green mass of fodder sunflower and in potato tubers compared to the object without mineral fertilization. [ABSTRACT FROM AUTHOR]

High sorption capacities of soils in respect to potassium enable the application of the latter in high doses to meet the nutritional requirements of all plants in crop rotation. However, overstepping a certain level and braking off buffering capacity of soil may appear unfavorable for both the plants and soil environment. Tests were performed on brown soil in profiles reconstructed in plastic tubes 7 cm in diameter and one meter high. Potassium (in KCl form) was introduced down to the level of ploughed humus of the soils in the equivalent quantities of: 0, 25, 50, 75, 100, 125, and 150% of sorption capacities at Ap level and water was poured to simulate 420 mm of precipitation. The applied doses of potassium had an unequal effect on the dynamics of chemical processes. Potassium in high doses strongly extracted magnesium and calcium cations from the surface layers to deeper levels and to the filtrates. It had no effect on hydrogen desorption or on the dynamics of bioavailable forms of phosphorus. The elements Mg>Ca>Na>K, in this order, were most washed out of the profile, whereas K>Mg>Na>Ca, in this order, exhibited the highest dynamics under the effect of fertilization. [ABSTRACT FROM AUTHOR]

Soil acidification in top layers (measured as its intensity and range in soil profile) is related to the value of acid rainfall and causes particular changes in chemical and physicochemical features. The model research presents reaction of degraded chernozem to acidification. Determining the level of soil acidification, in which strong chemical degradation occurs, was an aim of our investigation. A model study upon the degraded chernozem reaction toward the acidifying action of simulated acid rain was performed in columns of 1 m height and 7 cm diameter. The acid rain was divided into 20 doses of 80 ml per each column and was applied daily in six doses equivalent to 25%, up to 150% of the sorption capacity of Ap horizon. The surface application of hydrogen ions within Ap horizon of reconstructed chernozem profile invokes the decrease of pH value of the soil solution and hydrolytic acidity till the complete saturation of the sorption complex with hydrogen cations at concentration equivalent to 150% of sorption capacity of Ap horizon (level VI), proportional to the acid concentration. Reaction toward acidifying gradually weakens in deeper layers. The basic cations eliminated out of the surface horizons at low amounts were removed along with filtrates out of the soil profile in the following sequence: Ca>Na>Mg>K; they were retained mainly in deeper horizons. Acid rain application in a dose equivalent to 50% of the sorption capacity of Ap horizon of degraded chernozem provokes substantial deterioration of chemical and physicochemical features, while in deeper layers it is less visible. Strengthening the acid rain (over 50% of the sorption capacity of Ap horizon) increases the negative effect and enlarges its range in soil profile. [ABSTRACT FROM AUTHOR]