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The objective of the study was to assess the effects of long-term application of liquid manure from pig production and digestate from manure fermentation installation for biogas production on chemical changes in the soil, i.e.: soil reaction, accumulation of available forms of phosphorus, potassium, and magnesium in the soil arable layer, as well as the phosphorus balance. The assessment was carried out in two highly productive farms specialising in pig production, located in the Zachodniopomorskie Province. The soils under the study were treated with slurry and digestate annually for subsequent 12 years. The assessment of changes in nutrient content and accumulation was performed twice: after 10 and 12 years of fertiliser treatments. The rate of changes in soil reaction due to slurry and digestate application varied depending on the analysed field. Irrespective of the analysed field, 12-year application of slurry caused a drop in soil pH by an average of half a unit. The direction of changes in the content of available nutrient forms in the soil varied depending on the element evaluated. Notwithstanding the analysed field and the type of slurry used, a decrease in the content of available forms of potassium in the soil was observed. Slurry fertilisation did not affect magnesium contents in the soil. In the study period, the content of magnesium remained unchanged. Among the evaluated nutrients, an increased nutrient content in the soil was only found in the case of phosphorus – as a result of application of liquid manure in combination with mineral fertilisation. In the analysed farms, in the case of fields fertilised with slurry and digestate, the phosphorus balance was positive, and ranged from 15 to 40 kg P·ha−1. The obtained values of the phosphorous balance strongly suggest that regardless of the type of liquid manure used on the farm, measures should be taken to introduce changes in the scope of fertilisation plans, with particular emphasis on the principles of balanced fertilisation.

The major indicator of soil fertility and productivity are humic acids (HAs) arising from decomposition of organic matter. The structure and properties of HAs depend, among others climate factors, on soil and anthropogenic factors, i.e., methods of soil management. The purpose of the research undertaken in this paper is to study humic acids resulting from the decomposition of crop residues of wheat ( Triticum aestivum L.) and plant material of thuja ( Thuja plicata D.Don.ex. Lamb) using electron paramagnetic resonance (EPR) spectroscopy. In the present paper, we report EPR studies carried out on two types of HAs extracted from forest soil and incubated samples of plant material (mixture of wheat straw and roots), both without soil and mixed with soil. EPR signals obtained from these samples were subjected to numerical analysis, which showed that the EPR spectra of each sample could be deconvoluted into Lorentzian and Gaussian components. It can be shown that the origin of HAs has a significant impact on the parameters of their EPR spectra. The parameters of EPR spectra of humic acids depend strongly on their origin. The HA samples isolated from forest soils are characterized by higher spin concentration and lower peak-to-peak width of EPR spectra in comparison to those of HAs incubated from plant material.

The fruit fly Drosophila melanogaster is a model species used for a wide range of studies. Contamination of Drosophila cultures with bacterial infection is common and is readily eradicated by antibiotics. Neomycin antibiotics can cause stress to D. melanogaster 's larvae and imagoes, which may affect the interpretation of the results of research using culture from neomycin-based medium. In the present study, fluctuating asymmetry (FA), one of the important bioindicators of stress, was measured. Larvae and imagoes of a wild-type D. melanogaster strain were exposed to various concentrations of neomycin. The size of anal papillae and selected wing veins were measured using scanning electron and light microscopy, respectively. Next, the FA was checked. The values obtained for larval anal papillae appeared to be concentration-dependant; the FA indices increased with the concentration of neomycin. The wing FA presented a large but variable correlation, depending on the measured vein. However, the mean length of veins was the highest for the control group, with neomycin-exposed groups showing lower values. The research showed that neomycin may cause sublethal stress in D. melanogaster , which manifests in increased FA indices. This suggests that neomycin can cause physiological and developmental stress in insects, which should be taken into account when interpreting the results of studies using these model organisms.