Intensive research has been conducted for many years to develop environmentally friendly techniques for plant cultivation that optimize the fertilization process. One of the most promising areas within the fertilizer industry is using microbiologically enriched fertilizers, which incorporate beneficial bacteria or fungi. Biofertilizers are the focus of studies on both their production technologies and their effects on crop growth and yield, presenting a potential alternative to conventional mineral fertilizers. The prolonged and improper use of mineral fertilizers, along with inadequate plant protection, a lack of organic fertilization, and poor crop rotation practices, negatively impact soil health, disrupting microbial populations and ultimately diminishing yield quality and quantity. Microorganisms, particularly specific groups known as plant growth -promoting rhizobacteria (PGPR) and beneficial fungi, are estimated to make up 85% of the total soil biomass and play a crucial role in soil fertility by mineralizing organic matter, suppressing pests and pathogens, forming humus, and maintaining proper soil structure. They also provide optimal conditions for plant growth. Soil microorganisms can be categorized as either autochthonous, naturally present in the soil, or zymogenic, which develop when easily assimilable organic matter is added. Key microorganisms such as Micrococcus, Bacillus, Azotobacter, and nitrogen-fixing bacteria like Rhizobium and Bradyrhizobium significantly contribute to soil health and plant growth. Microbially enhanced fertilizers not only supply essential macro- and micronutrients but also improve soil quality, enhance nutrient use efficiency, protect plants against pathogens, and restore natural soil fertility, fostering a balanced biological environment for sustainable agriculture.

The article presents the behavior of phenoxy acids in water, the levels in aquatic ecosystems, and their transformations in the water environment. Phenoxy acids are highly soluble in water and weakly absorbed in soil. These highly mobile compounds are readily transported to surface and groundwater. Monitoring studies conducted in Europe and in other parts of the world indicate that the predominant phenoxy acids in the aquatic environment are mecoprop, 4-chloro-2-methylphenoxyacetic acid (MCPA), dichlorprop, 2,4-dichlorophenoxyacetic acid (2,4-D), and their metabolites which are chlorophenol derivatives. In water, the concentrations of phenoxy acids are effectively lowered by hydrolysis, biodegradation, and photodegradation, and a key role is played by microbial decomposition. This process is determined by the qualitative and quantitative composition of microorganisms, oxygen levels in water, and the properties and concentrations of phenoxy acids. In shallow and highly insolated waters, phenoxy acids can be decomposed mainly by photodegradation whose efficiency is determined by the form of the degraded compound. Numerous studies are underway on the use of advanced oxidation processes (AOPs) to remove phenoxy acids. The efficiency of phenoxy acid degradation using AOPs varies depending on the choice of oxidizing system and the conditions optimizing the oxidation process. Most often, methods combining UV radiation with other reagents are used to oxidize phenoxy acids. It has been found that this solution is more effective compared with the oxidation process carried out using only UV.

The aim of the study was to determine the effect of increasing potassium fertilization (0, 140, 190, and 240 mg K₂O/kg of soil) in the interaction with nitrogen fertilization (130 and 170 mg N/kg of soil) on the trace elements content in the typical, non-contaminated agricultural soil. The trace elements content in the soil depended on nitrogen and potassium fertilization. Potassium fertilization had a more significant effect on trace elements content in the soil fertilized at the same time with a lower nitrogen dose (130 mg N/kg soil). Increasing potassium fertilization increased the content of cadmium by 83% and lead by 32% and reduced the amounts of chromium by 10% and iron by 3% in the soil, particularly in the series with a lower nitrogen dose (130 mg N/kg soil). The effect of potassium fertilization on the content of other trace elements was less unambiguous since, for most of trace elements, lower doses of this fertilizer contributed to growth of trace element, while higher doses lead to a decrease in their accumulation in the soil. Nitrogen fertilization increased the contents of zinc and iron—3%, copper—9%, manganese—12%, chromium—15%, and cobalt—59%, while reducing the contents of cadmium and nickel—24% and lead—45%. Permissible standards for trace elements content in the soil have not been exceeded.

Due to the growing world population, the challenge for the agriculture industry is to produce the right amount of food. This is not possible without the use of fertilizers. Unfortunately, apart from having a positive effect on the yield parameters, they can also adversely affect the natural environment. The use of fertilizers in excess or in a poorly digestible form causes the migration of fertilizer components beyond the reach of the plant root system. In this way, nutrients enter the groundwater, surface water and the atmosphere, contaminating them. The consequence of such actions is further climate warming and the deterioration of water status and air quality. Suspension fertilizers are an interesting proposition that meets the requirements of modern agriculture. They combine the advantages of liquid and solid fertilizers. The liquid form ensures better digestibility of the nutrients, especially in periods of drought, and the concentration of the ingredients is comparable to that of solid fertilizers. At the same time, production costs are lower, which is related to the simplification of the technological process and the possibility of using cheaper raw materials. A valuable advantage of fertilizer suspension is the possibility of using hydrated waste substances in their production.

This study has been carried out in order to determine the effect of increasingly intensive fertilization with potassium, applied in combination with nitrogen, on the content of trace elements in soil after the harvest of maize (Zea mays L.). The soil content of trace elements depended on the fertilization with potassium and nitrogen. Potassium fertilization had a stronger effect on the content of trace elements in the pots fertilized with the lower nitrogen dose (130 mg N kg⁻¹ of soil). The increasing doses of potassium led to a higher soil content of zinc (Zn), and especially of nickel (Ni). The impact of potassium fertilization on the content of the remaining trace elements in the soil was less unambiguous, and depended on the dose of potassium and nitrogen fertilization. Nitrogen fertilization resulted in a higher soil content of manganese (Mn), chromium (Cr), nickel (Ni) and cadmium (Cd), as well as a decreased soil content of lead (Pb). It needs to be underlined that changes in the soil content of Ni, Cd, and Pb, effected by nitrogen fertilization, were larger than in the cases of the other trace elements. The influence of potassium and nitrogen fertilization did not result in exceeding the current threshold amounts of trace elements set for agriculturally used soil. An increase in the contents of some trace elements in soil is beneficial from an agricultural point of view. Some of these elements are necessary for the correct growth and development of arable plants.