This data descriptor presents a dataset comprising crop and soil parameters measured in winter wheat fields near the town of Knezha, Bulgaria. The data were collected as part of a project evaluating the potential of vegetation indices derived from Sentinel-2 satellite imagery to predict biophysical and biochemical crop parameters. The core dataset consists of measurements obtained from 20 m × 20 m field plots and includes a broad range of parameters: leaf area index, fraction of absorbed photosynthetically active radiation, vegetation cover fraction, chlorophyll content, above-ground biomass, plant nitrogen content, biological yield, surface soil moisture, spectral reflectance, plant density, crop height, visual assessments of disease or pest damage, and data on weed occurrence. The dataset is complemented by unmanned aerial vehicle imagery, crop calendars, and field management information. The main soil types in the study area were characterized through soil profiles, while meteorological data were obtained from an automated weather station. The data were collected during the 2016–2017 and 2017–2018 agricultural seasons. The dataset is freely available for download and serves as a valuable resource for researchers in remote sensing—particularly for validating satellite-derived products—as well as for specialists involved in winter wheat monitoring, modeling, and agronomic studies.

Soil contamination with heavy metals (HM) poses a risk to human health and can impact different soil functions. This study aimed to determine the influence of heavy metal pollution on the physical and physicochemical characteristics of the two profiles of alluvial–deluvial soil under grassland located at different distances from the Aurubis-Pirdop Copper smelter in Bulgaria. Data for soil particle-size distribution, soil bulk and particle densities, mineralogical composition, soil organic carbon contents, cation exchange properties, surface charge, soil water retention curves, pore size distribution—obtained by mercury intrusion porosimetry (MIP)—and thermal properties were obtained. The contents of Pb, Cu, As, Zn, and Cd were above the maximum permissible level in the humic horizon and decreased with depth and distance from the Copper smelter. Depending on HM speciation, the correlations are established with SOC and most physicochemical parameters. It can be concluded that the HMs impact the clay content, specific surface area, distribution of pores, and the water stability of soil aggregate fraction 1–3 mm to varying degrees.

In drought-prone regions without irrigation systems, effective agrotechnologies such as subsoiling are crucial for enhancing soil infiltration and water retention. However, the effects of subsoiling can vary depending on crop type and environmental conditions. Despite previous research, there is limited understanding of the contrasting responses of C3 (sunflower) and C4 (maize) crops to subsoiling under drought stress. This study addresses this knowledge gap by assessing the effectiveness of subsoiling as a drought mitigation practice on Haplic Chernozem in Northern Bulgaria, integrating ground-based and remote sensing data. Soil physical parameters, leaf area index (LAI), canopy temperature, crop water stress index (CWSI), soil moisture, and yield were evaluated under both conventional tillage and subsoiling for the two crops. A variety of optical and radar descriptive remote sensing products derived from Sentinel-1 and Sentinel-2 satellite data were calculated for different crop types. Consequently, the use of machine learning, utilizing all the processed remote sensing products, enabled the reasonable prediction of LAI, achieving a coefficient of determination (R²) after a cross-validation greater than 0.42 and demonstrating good agreement with in situ observations. Results revealed differing responses: subsoiling had a positive effect on sunflower, improving LAI, water status, and slightly increasing yield, while it had no positive effect on maize. These findings highlight the importance of crop-specific responses in evaluating subsoiling practices and demonstrate the added value of integrating unmanned aerial systems (UAS) and satellite-based remote sensing data into agricultural drought monitoring.

Water erosion is the most important degradation process affecting Epicalcic Chernozems quality. Many technologies and tillage systems are used to control water erosion in agricultural areas and to preserve soil fertility. Cover crops are considered an agricultural practice that contributes to carbon sequestration, improved infiltration, erosion control, and improved microbiological processes. The aim of the present study was to determine how the continuous application of a cover crop, in a wheat-maize rotation on sloped arable land, would alter the soil organic carbon, greenhouse gas fluxes and the soil microbial community, as the most significant regulator of soil carbon dynamics and biogeochemical cycles. An experiment with wheat and maize, in rotation, with the application of up-and-down slope culture (T0), traditional contour tillage (T1) and crop specific erosion control contour tillage (T2) was performed for four years in the experimental field Trastenik, Ruse. The T2 variant includes minimum tillage, direct sowing and cover crop after wheat harvest and before maize sowing. The content of total organic carbon, labile organic matter, the number of main groups of soil microorganisms, as well as CO2 and N2O soil emissions were monitored. In comparison to T0 and T1 treatments, an increasing number of ammonifying, cellulose decomposers, actinomycetes, and nitrogen-fixing bacteria were determined in the T2 variant under maize. In the spring and summer, there were higher number actinomycetes and cellulose decomposers in wheat variants. The enhanced total organic carbon was determined in T2 treatments. Soil CO2 emissions (29.8 kg ha-1 day-1) were reduced in the minimum tilled wheat variant, followed by the T0 (30.0 kg ha-1 day-1) and T1 (30.8 kg ha-1 day-1). The soil crust formation due to more intensive erosion process explains the lower average emissions under maize at the T0 variant, grown conventionally up and down the slope in comparison with T1 and T2. N2O emissions were generally lowest in the T2 treatments for both crops in four years. The minimum tillage for maize and wheat growing on slope lands with the inclusion of cover crop in the rotation, have a positive effect on soil organic matter, microflora and GHG emissions.

The approach developed by us adheres to the limitation methods recommended by the FAO, and more precisely to those that take into account the number and degree of existing limitations for a certain set of soil characteristics, and is tailored to the specifics of agricultural production at the farm level. The research enables dynamic monitoring of changes in soil quality in accordance with measures taken to improve its health. This study presents a methodology that combines a limited set of soil characteristics specific to each farm. The aim is to make it easier for farmers to provide the necessary information and to make data-driven decisions, taking into consideration soil health and ensuring sustainable farm management. The suggested methodology will be used as a backbone of software that will be developed for profit optimization at the farm level. The soil features selected for work are grouped into four large groups, complying with the rule to work with the smallest possible number of characteristics that describe as fully as possible the agroecological conditions in relation to the requirements of the plants, while at the same time not allowing double and triple evaluation of the same characteristic.The degrees of restrictions (from L0 to L4) are determined for each soil feature separately using the developed scales, and based on this, the suitability for agricultural use of the farm is assessed. A comprehensive assessment and classification of farms by suitability for agriculture is carried out.