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The aim of this study was to narrow the research gap of ambiguity in which machine learning algorithms should be selected for evaluation in digital soil organic carbon (SOC) mapping. This was performed by providing a comprehensive assessment of prediction accuracy for 15 frequently used machine learning algorithms in digital SOC mapping based on studies indexed in the Web of Science Core Collection (WoSCC), providing a basis for algorithm selection in future studies. Two study areas, including mainland France and the Czech Republic, were used in the study based on 2514 and 400 soil samples from the LUCAS 2018 dataset. Random Forest was first ranked for France (mainland) and then ranked for the Czech Republic regarding prediction accuracy; the coefficients of determination were 0.411 and 0.249, respectively, which was in accordance with its dominant appearance in previous studies indexed in the WoSCC. Additionally, the K-Nearest Neighbors and Gradient Boosting Machine regression algorithms indicated, relative to their frequency in studies indexed in the WoSCC, that they are underrated and should be more frequently considered in future digital SOC studies. Future studies should consider study areas not strictly related to human-made administrative borders, as well as more interpretable machine learning and ensemble machine learning approaches.

The aim of this review was to collect current results on the effect of different plants grown as winter and summer cover crops (CC) on the physical, chemical, and biological properties of soil and on the yield of cereal crops grown in a site with CC, using conservation soil tillage. The analyzed studies indicate that CC usually have a positive impact on the physical and biological properties of the soil. Regardless of the plant species used as CC, we can expect an increase in the number of soil microorganisms and an improvement in the activity of soil enzymes. This effect is particularly beneficial in the case of reduced tillage systems. Mixing CC biomass with the topsoil loosens compacted soils and, in the case of light, sandy soils, increasing the capacity of the sorption complex. The size and composition of CC biomass and weather conditions during the vegetation period and during the covering of the soil with plant biomass are of great importance for improving the chemical properties of the soil. A beneficial effect of CC, especially legumes, on the content of the mineral nitrogen in the topsoil is usually observed. Sometimes, an increase in the content of available forms of potassium (K) and/or phosphorus (P) is also achieved. The effect of CC on the content of soil organic carbon (C), total nitrogen (N), or soil pH is less common. CC used in reduced tillage systems can significantly improve the yield and quality of cereal grain, especially when legumes are used as CC in low-fertility soil conditions and at low fertilization levels. However, non-legumes can also play a very positive role in shaping soil properties and improving cereal yield.

As conservation tillage becomes one of the foundations of sustainable crop production, important questions arise about its value, which needs to be defined and evaluated. One of the most important indicators of soil compaction is penetration resistance (PR), which comes as a short-term response to the state of soil physics. The objective of this work is to compare different tillage treatments (TT) on soil compaction on silty clay loam Stagnosol and silt Gleysol in the continental part of Croatia. The research included three tillage treatments: ST—conventional tillage, CTD—deep conservation tillage, and CTS—shallow conservation tillage. PR was determined on each soil depth of 5 cm up to 80 cm, and measuring was provided on two measuring dates. The obtained results showed a higher influence of the year factor than TT. In the upper layers (up to 35 cm), PR values between TT were with significant differences, but in most cases below root-limiting critical values, while in deeper soil layers (35–80 cm), we found that penetration values on each tillage treatment begin to stabilize and smooth out in most cases, with similar dynamics on both soil types and measurement dates. In most of the cases, the highest PR was measured for conservation treatments in wetter soil conditions.

Measuring the soil water content (SWC) is a fundamental component of the sustainable management of water resources, soil preservation, and high irrigation efficiency. Non-destructive SWC measurements using soil moisture sensors (SMSs) enables timely irrigation and reduces overirrigation and water stress. Within this context, the performance of four commercial single-point soil moisture sensors (Watermark and tensiometer (Irrometer Company, Inc., Riverside, CA, USA), SM150 (Delta-T Devices, Cambridge, UK)), FieldScout TDR300 (Spectrum Technologies, Aurora, IL, USA) and one soil profile PR2 probe (Delta-T Devices, Cambridge, UK) were tested under anthropogenic eutric cambisol with a silty clay loamy texture (20, 30, and 40 cm) to evaluate accuracy and sensitivity to changes in the SWC in an irrigated apple orchard. The Watermark and tensiometer were additionally tested in the laboratory to convert soil water tension (kPa) to the volumetric soil water content (%vol.). In general, all tested SMSs responded to changes in the SWC, with sensor-to-sensor differences. The Watermark and tensiometer underestimated the SWC, while the TDR overestimated the SWC. The SM150 and PR2 showed high accuracy, i.e., SM150—RMSE-2.24 (20 cm), 2.18 (30 cm) and 2.34 (40 cm), MSE—5.02 (20 cm), 2.93 (30 cm) and 1.89 (40 cm), and PR2—RMSE-1.8 (20 cm), 1.3 (30 cm) and 1.55 (40 cm), MSE-3.23 (20 cm), 1.7 (30 cm) and 2.39 (40 cm) at all observed soil depths.

Conservation tillage (CT) is an effective tool for maintaining crop productivity under adverse climate conditions, while its adoption is conditioned by the possible negative response of crop weed. Research with CT and liming (L) was conducted at different experimental sites on acid soils (ES 1 and ES 2) to determine the maize weediness and yield. The tillage treatments used were ST (conventional tillage), CTD (deep loosening), CTS (shallow loosening), and liming; Ly (CaO) and Ln (no CaO). The weediness assessment was conducted at the V7 and R5 maize growth stages. Weed density (WD), biomass (WB), weed coverage (WC), and species density (WSN) were determined. The highest WD was recorded on ES 2 in V7, and WB, WC, and WSN were significantly higher at CTS in R5 compared to ST. Liming affected the decrease of WD and WC in V7 and WB, WC, and WSN in R5. The average maize yield on ES 2 was 36% higher compared to ES 1. CTS resulted with the highest yield at ES 1, while at ES 2, it was similar to ST. Liming application significantly increased the maize yield. The given results indicated the positive impact of CT and L on crop productivity in different agroecological conditions, despite the increased weediness.

Biochar, a carbon-rich material, is highlighted to improve soil fertility, simultaneously mitigating climate change by carbon sequestration. Combined with mineral fertilizer, it can increase weediness, the major source of yield loss in agricultural production. Research with biochar was conducted in Eastern Croatia in 2016, with the aim to investigate the influence of biochar and mineral fertilizer on weed infestation and winter wheat yield. Field experiments were set up as a split-plot where biochar (B) was the main factor and fertilization was the sub factor. The main treatments were: B0 (control without biochar), B1-5 t ha−1, B2-10 t ha−1 and B3-15 t ha−1. Fertilization sublevels were F0) without fertilizer and F1) optimal dose of fertilizer. Weediness was determined by counting and measuring aboveground biomass. The treatments with the greatest effect on weediness were B3 and F1 in the winter wheat tillering stage. In the winter wheat ripening stage, treatment B3 obtained the highest weediness and F1 significantly reduced weed density. Biochar treatment B3 increased winter wheat yield by 77% in relation to the control. The application of biochar combined with fertilization affected the level of weediness depending on agroecological conditions, but with a significant increase in yield.

Effects of soil tillage (CTconventional, SS-subsoiling, CH-chiselling, DH-disk-harrowing and NT-no-till) and nitrogen rate (reduced N1, optimal N2 and luxury N3) on yield and yield components of maize and winter wheat in two different agricultural subregions of Croatia (Magadenovac and Cacinci site), were studied in the years 2013–2014 as part of a long-term experiment. Maize yield and yield components were influenced by site properties, tillage and nitrogen treatments. The highest yields and yield components were recorded at the Magadenovac site with N2 and N3. The lowest values of the yield and yield components of maize were recorded on NT and were significantly lower than CT, SS, CH and DH, among which no significant differences were recorded. Winter wheat yield and yield components were affected by site properties and nitrogen rates while soil tillage treatments only had an influence on grain and straw yield and plant height. Winter wheat achieved maximum yield and yield components on a N3 and N2 and at the Magadenovac site. Winter wheat grain yield decreased in the following order: SS > DH > CH > NT > CT. The obtained results indicate the importance of optimal nitrogen fertilization and the possibility of the implementation of conservation tillage for maize and winter wheat production in different agroecological conditions.