Microplastic pollution threatens soil health by disrupting chemical and microbial balances and impairing nutrient cycling, with effects that vary depending on soil properties. The objective of this study is to determine the effects of contamination with three types of microplastics (<5 mm)—polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET)—on the microbiological and chemical parameters of four soil types in Bulgaria: Calcic Chernozem, Vertisol, Luvisol, and Fluvisol. A controlled 180-day laboratory incubation experiment was performed, where each soil type was contaminated with microplastics at three concentrations to monitor changes in key microbiological and chemical properties. It was established that microplastics contamination suppressed abundance of key microbial groups and limited nutrient availability, inducing a state of biological and chemical imbalance in the soil. PET exerted the strongest impact on soil chemical properties, with the agrochemical properties of Fluvisol being the most sensitive to MP contamination. PE and PET had the greatest influence on microbial communities, with Vertisol and Luvisol being the most affected in this regard. PP contamination altered key metabolic processes, with the specific impact being highly dependent on soil type and most pronounced in Chernozem. Furthermore, the concentration influenced the measured parameters, with the effects varying depending on the soil type and the microplastic type. Among the factors influencing soil responses to microplastic contamination, soil type appears to be the most decisive, followed by the type of microplastic.

The key objectives of contemporary agriculture are restoring biodiversity, preserving ecosystem health, reducing the effects of climate change, and producing safe and healthy foods. Maintaining high soil fertility while reducing greenhouse gas emissions requires a precise assessment of how fertilization and crop rotation affect carbon and nutrient cycles in agroecosystems. Fertilization affects soil conditions, which alters the environment for soil microbial development and influences the number and composition of soil microbial communities, leading to changes in nutrient and carbon cycling. There is a lack of long-term experimental data on the impact of fertilizer treatments on soil CO₂ emissions, soil microbial communities, and their interactions. The novelty of this study is that it identified the fertilization effects on soil carbon sequestration, soil properties, and microbial communities in the context of a long-term fertilizer experiment in Luvic Chernozem. The fertilization treatments that were continuously pplied for 64 years under a four-crop (wheat, barley, corn, and bean) rotation were nitrogen (N), phosphorus (P), potassium (K), NP, NK, PK, NPK, and control. The chemical and microbiological soil properties and soil CO₂ emissions were monitored. The highest organic carbon content was observed under the NPK (1.42%) and NP (1.43%) treatments. N fertilizer application most significantly affected soil properties, including pH, electrical conductivity, and soil organic carbon content, altering the environment for soil microbial development and influencing the number and composition of soil microbial communities. On average, the field-measured soil C-CO₂ emissions were the most intensive under NP (2.76 kg ha⁻¹ h⁻¹), NPK (2.83 kg ha⁻¹ h⁻¹), and PK (2.51 kg ha⁻¹ day⁻¹) treatments.

A key objective of contemporary agriculture is to restore biodiversity, preserve ecosystem health, reduce the effects of climate change, and produce safe and healthy foods. Maintaining high soil fertility while reducing greenhouse gas emissions requires a precise assessment of how fertilization and crop rotation affect the carbon and nitrogen cycles in agroecosystems. In the context of a long-term fertilizer experiment on Luvic Chernozem, a monitoring of chemical and microbiological soil properties and CO2 emission was carried out. The fertilization treatments that have been continuously applied for 64 years under four-crop (wheat, barley, corn, and beans) rotation are N, P, K, NP, NK, PK, NPK, and 0. The highest organic carbon content was observed in the treatments NPK (1.42%) and NP (1.43%), and the lowest in the control (1.05%). The constant application of nitrogen as single fertilizer led to lower SOC values (1.22%). On average, CO2 emissions were the most intensive in NP (66.34 kg ha-1 day-1), NPK (67.82 kg ha-1 day-1) and PK (60.16 kg ha-1 day-1) treatments. The nitrogen fertilizer application most significantly alters soil properties including pH, EC, and SOC, which alters the environment for soil microbial development and influences the number and composition of soil microbial communities.