Nitrogen (N) is widely distributed in the lithosphere, hydrosphere, atmosphere and biosphere. It is a basic component of every plant cell as well as microorganisms, as a component of proteins, nucleic acids and chlorophyll. It enters soil with organic and mineral fertilizers, plant and animal residues and biological nitrogen fixation. There are various forms of nitrogen in soil, and this element is usually transformed by microorganisms. The transformation of nitrogen compounds (ammonification, nitrification and immobilization) is significantly influenced by climatic conditions and the physicochemical properties of soil. Microbial mineralization of nitrogen organic matter results in the enrichment of soil with this element, which is necessary to generate a yield. The amount of nitrogen entering soil through the mineralization of crop residues ranges from 15 to 45 kg N/ha in cereal residues and from 80 to 144 kg N/ha in winter rape residues. Biological nitrogen fixation can increase the nitrogen content in soil by 30–50 kg/ha/year. In recent decades, the mismanagement of mineral fertilizers has drastically changed the natural balance of the nitrogen cycle. Every year huge amounts of nitrogen compounds enter the aquatic ecosystems and cause their eutrophication. That is why it is important to have adequate knowledge of sustainable fertilization so as to practice integrated crop management.

The aim of this article is to present the issues related to the significance of microorganisms in the mineralization of crop residues and the influence of environmental factors on the rate of this process. Crop residues play a very important role in agriculture because they can be used both as an environment-friendly waste management strategy and as a means of improving soil organic matter. The inclusion of crop residues in the soil requires appropriate management strategies that support crop production and protect the quality of surface water and groundwater. Crops need nutrients for high yields; however, they can only absorb ionic forms of elements. At this point, the microorganisms that convert organically bound nitrogen, phosphorus, and sulfur into soluble NH₄⁺, NO₃⁻, H₂PO₄⁻, HPO₄²⁻, and SO₄²⁻ ions are helpful. Mineralization is the transformation of organic compounds into inorganic ones, which is a biological process that depends on temperature, rainfall, soil properties, the chemical composition of crop residues, the structure and composition of microbial communities, and the C:N ratio in soil after the application of plant matter. An adjustment of the values of these factors enables us to determine the rate and direction of the mineralization of crop residues in soil.

Meeting the nutritional needs of a dynamically developing global society is a major challenge. Despite the modernisation of agriculture, huge losses in the quality and quantity of crops occur each year, mainly due to weed species, which are the most important biotic limitation to agricultural production. Globally, approximately 1800 weed species cause a 31.5% reduction in plant production, which translates to USD 32 billion per year in economic losses. However, when the same herbicides are frequently applied, plants develop segetal immune mechanisms. There are currently around 380 herbicide-resistant weed biotypes worldwide. Due to the negative influence of herbicides on ecosystems and the legal regulations that limit the use of chemical crop protection products, it is necessary to develop a new method of weed control. Bioherbicides, based on living organisms or their secondary metabolites, seem to be an ideal solution. The biocontrol market is worth around EUR 550 million in Europe and EUR 1.6 billion worldwide, with an estimated 15% growth expected by 2025. Despite numerous studies that have demonstrated the effectiveness of microbial bioherbicides, only 25 mould-based bioherbicides are currently available to growers. Due to the high specificity and selectivity of biological crop protection products, as well as their low production costs and non-toxicity to the environment and human health, they would appear to be a safe alternative to chemical pesticides.

The negative impact of chemical pesticides on the environment and human health has contributed to the introduction of legal regulations that ensure the reduction in the use of agrochemicals in favor of biological products. The existing review of the literature, including our research, clearly shows that the ideal biocontrol agents are Trichoderma fungi. The production of antibiotics, lytic enzymes degrading the cell walls of plant pathogens, or inducing a defense response in plants are just some of the features supporting the wide use of these microorganisms in sustainable agriculture. It is estimated that currently about 60% of biofungicides used to eliminate fungal pathogens are produced based on Trichoderma sp. strains.

In recent years, growing environmental awareness, the need to reduce greenhouse gas emissions, and the energy crisis have led many countries to seek alternative energy sources. One of the most promising solutions is biogas production via anaerobic digestion (AD), whose substrate can be organic-rich and easily biodegradable food waste (FW). This waste is a significant part of the global waste problem, and its use for energy production is beneficial to both the environment and the economy. This paper presents important issues concerning the monitoring of the AD process, as well as standard and innovative, for the implementation of this process, technological solutions. The aim of the measures taken to optimise the process is to increase AD efficiency and obtain the highest possible methane content in biogas. Two approaches—pretreatment and anaerobic co-digestion (AcoD)—have been integral to the implementation of AD of food waste for years. They are presented in this paper based on a review of recent research developments. Pretreatment methods are discussed with particular emphasis on mechanical, chemical and biological methods. The AcoD of FW with different organic substrates has been extensively reviewed, as confirmed by numerous studies, where higher buffer capacity and optimum nutrient balance enhance the biogas/methane yields. Attention was also paid to the parameters, operating mode and configurations of anaerobic digesters, with a thorough analysis of the advantages and disadvantages of each solution. The article concludes with a brief presentation of the development perspectives for the discussed FW management method and recommendations.

The soil tillage system and the distribution of stubble catch crops increase the content of organic carbon, thus increasing the biochemical activity of soil. The aim of the study was to assess the impact of leguminous cover crops and different tillage soil systems before spring wheat sowing on the count of soil microorganisms, biochemical activity, microbiological diversity and the physiological state of the plants in correlation with yield. The study compared and analysed the following systems: (1) conventional tillage (CT) to a depth of 22 cm, followed by spring wheat sowing using four simplified cultivation technologies called conservation tillage. The following simplified tillage systems were evaluated: (2) skimming before sowing the cover crop and spring wheat sowing after ploughing tillage (CT), (3) skimming before sowing of the cover crop (sowing wheat with no-till technology (NT)), (4) direct sowing of ground cover plants (NT) and spring wheat sowing after ploughing cultivation (CT) and (5) direct sowing of cover crop (NT) and sowing wheat directly into cover crop (NT). The results showed that applying the cover crop and soil tillage method before sowing wheat improved all tested parameters. The highest values of the analysed parameters were observed in the treatment with soil skimming before sowing of the cover plant, and then with sowing the wheat directly into the mulch. The activity of dehydrogenase was 90% higher, while the activity of phosphatase was 32% higher, in comparison to the control group. Both the activity of catalase and the biological index of fertility were 200% higher, in comparison to the control group. Metagenomic analysis showed that soil bacterial communities collected during treatment ‘zero’ and after different cultivations differed in the structure and percentage of individual taxa at the phylum level.