Christos Karamoutis

Improving environmental sustainability while maintaining economic viability is a major challenge for Mediterranean cereal production, where conventional systems are associated with high input use, elevated greenhouse gas emissions, and strong cost pressures. Although Conservation Agriculture (CA) and Precision Agriculture (PA) are widely promoted as promising solutions, evidence on their combined environmental and economic performance under real farming conditions remains limited. This study evaluated CA, PA, and their combined application (CPA) in winter cereal systems in Greece, using three years of farmer-managed field data from four representative sites. Agronomic and environmental performance and economic outcomes were assessed under actual farm sizes and a scaled 300 ha scenario. Across sites and years, no systematic yield differences were observed among CA, PA, and CPA, indicating that alternative systems can maintain yield stability under real farmer-managed conditions. Environmental performance was driven primarily by tillage intensity: CA reduced CO₂eq emissions by 212–238 kg ha⁻¹ relative to conventional tillage, while CPA achieved the largest reductions (262–332 kg ha⁻¹), accompanied by surface-layer SOM increases of 0.30–0.56% over three years. PA applied within conventional tillage resulted in only modest emission reductions (41–82 kg ha⁻¹), but consistently improved NUE, with variable-rate fertilization increasing NUE by approximately 5–7% relative to uniform application. Despite these environmental benefits, economic performance remained constrained due to high fixed machinery costs, high input prices, and low grain values resulting in negative net profits across all systems. CA reduced total costs by 3.8–11.8%, PA delivered only marginal improvements, while CPA achieved the largest cost reductions (5.0–12.6%) delivering also the most stable net profit mitigation. Carbon credit revenues increased profitability by only 2–3%. Scaling to 300 ha improved competitiveness through fixed-cost dilution, but profitability remained unattainable. Overall, integrated CA–PA systems offer substantial environmental benefits but require targeted policy support, cooperative machinery use, and service-based solutions to enable economically viable adoption in Mediterranean cereal systems.

Soil tillage significantly affects yield, grain quality, and the environmental footprint of cereals under Mediterranean rainfed conditions. This two-year field study evaluated five contrasting tillage systems: conventional tillage (CT), disc harrow (DH), chisel plough (CP), and two no-tillage systems, including long-term (NT1, 30 years) and recently established (NT2, 3–4 years), for their effects on yield and quality traits, and greenhouse gas (GHG) emissions of malting barley grown in Central Greece. Conventional tillage achieved the highest aboveground biomass (up to 12.1 t ha⁻¹) and yield (up to 6.3 t ha⁻¹), but resulted in lower thousand-grain weight (TGW) and reduced grain plumpness. In contrast, no-tillage systems produced slightly lower yields (4.3–5.2 t ha⁻¹), significantly higher TGW (up to 58.3 g), and improved grain-size distribution, while maintaining grain protein concentration within acceptable malting thresholds (10.4–11.0%). Environmental assessment indicated substantially lower GHG emissions under no-tillage, with NT2 achieving the lowest carbon footprint (0.19–0.22 kg CO₂ eq kg⁻¹). Carbon footprint estimates revealed that carbon accounting tools prioritize short-term management transitions over long-term no-tillage systems. Year effects reflected differences in rainfall distribution and temperature during critical growth stages. Overall, no-tillage systems provided the most balanced agronomic, qualitative, and environmental performance for malting barley under Mediterranean conditions.

Conservation tillage practices, such as reduced tillage and no-tillage, have recently garnered significant attention as core elements of the regenerative agriculture and carbon farming concepts. By minimizing mechanical soil disturbance, these practices preserve soil carbon and facilitate CO₂ fixation in the soil. Despite the widely acknowledged benefits, many farmers still approach no-tillage with skepticism. Their primary concerns are weed management and soil compaction. While weeds can be effectively controlled with the deployment of integrated weed management strategies, urgent soil compaction problems can be rapidly resolved only with mechanical interventions. That is why many no-till farmers resort to occasional heavy tillage, in a scheme characterized as rotational tillage, inadvertently sacrificing their regenerative assets in soil carbon. This is also a pivotal issue within carbon farming: the fate of soil carbon at the end of a compliant scheme focused on carbon fixation. The present study explores data of soil organic matter (SOM), soil penetration resistance (PR), and dry bulk density (DBD) from the initial, six-year period of a long-term tillage experiment in Greece. During that period, modifications to the experimental design allowed diverse combinations of five tillage methods (conventional tillage, 3 reduced tillage methods, and no-tillage). The findings indeed underscore the farmers’ concerns about soil compaction. High levels of PR and DBD were observed even at the topsoil layer of the no-tillage (NT). Conventional, moldboard plowing (MP) or reduced, chisel plowing (CP) applied after four years of uninterrupted no-tillage ameliorated most of the soil compaction; however, at the same time, this induced unfavorable consequences for SOM. In contrast, NT applied permanently for six years resulted in a substantial enhancement in SOM that reached 2.24%, for a sampling depth 0–0.30 m compared to 1.54% for permanent MP. When no-tillage was rotated with plowing in the fifth year, almost 50% of the sequestered carbon was lost and the SOM dropped to 1.87%. Nevertheless, the amount of SOM observed at the deeper 0.15–0.30 m layer was greater compared to permanent NT. This suggests that while plowing induced some loss of SOM, it also facilitated the uniform distribution into the soil profile, in contrast with the accumulation in the topsoil at prolonged NT. The permanent CP method and the NT/CP rotation provided comparative outcomes in terms of both soil compaction and soil carbon sequestration with the rotational NT/MP scheme, while all the other tillage combinations were inferior.

Wild mustard (Sinapis arvensis L.) and milk thistle (Silybum marianum (L.) Gaertn.) are two competitive broad-leaved weeds commonly found in cereals in Europe, while several weed species have developed resistance to the main herbicides that are applied on these crops. Thus, the implementation of integrated weed management (IWM) programs is of great importance. Field experiments were conducted based on a split-plot design with two factors (sowing date and herbicides). Our results showed that the density of wild mustard and milk thistle was higher in the early sowing compared to the late sowing, while the total weed density was up to 75% higher in early sowing. Moreover, the herbicides florasulam + 2.4-D and bromoxynil + 2.4-D exhibited high efficacy (>98%) against milk thistle and wild mustard, while tribenuron-methyl and florasulam + clopyralid provided greater efficacy in the late sowing compared to the early sowing. Among the four herbicides, the lowest dry biomass and grain yield of wheat were observed in tribenuron-methyl and florasulam + clopyralid, while in the weed-infested treatment, the highest values of both parameters were recorded in late sowing. Finally, the results showed that the sowing date is a cultural weed control method that should be implemented in IWM programs, since it can affect both weed density and herbicide efficacy.

Castor is a crop with an evergreen habit so artificially-induced ripening is an essential precondition for mechanical harvesting of new dwarf annual hybrids. Plants’ moisture imposes a determinant effect both on pre-harvest and post-harvest seed loss, so frequent monitoring of crop ripening is crucial for identifying the optimum moisture for harvest. Remote sensing information from Unmanned Aerial Systems (UASs) along with field measurements were utilized in the present study in order to evaluate three harvest aid chemicals, herbicides glyphosate (GLY) and diquat (DIQ) and the defoliant Spotlight^® (DEF) for terminating the castor crop and identifying opportunities for using remote sensing as a tool for monitoring crop ripening. The results showed that glyphosate required more than two weeks to dry out the crop while diquat and spotlight^® presented a rapid action within two to four days. Nineteen vegetation indexes (VIs) were derived from a multispectral and an RGB camera mounted on two UAS and were plotted against field measurements. NDVI presented a higher accuracy (R² = 0.67) for predicting the castor stems’ and leaves’ moisture content while OSAVI and SIPI2 were more powerful in predicting moisture of capsules (R² > 0.76). High efficiency was also obtained with VARI_green, an index estimated from the common bands of a conventional RGB camera. The best performing VIs were further utilized in multiple linear regression models also incorporating the date of spraying as information. The VI models further improved the predicting power with an R² of up to 0.73 for stems and leaves and 0.81 for capsules.

The contribution of castor oil for reaching the targets set by RED1 and RED2 in Europe can be tangible if the problem related to the mechanical harvesting is overcome. Dwarf hybrids suitable for mechanical harvesting are already available on the market but the residual moisture of plants and capsules has to be lowered in order to allow mechanization. In the present case of study, three common terminating products (Glyphosate GLY, Diquat DIQ and Spotlight DEF) were tested on Kaiima C1012 hybrid in a complete randomized block design to assess the effectiveness of using chemical products to decrease residual moisture in castor plants. Plants were harvested via combine harvester equipped with cereal header to evaluate seed loss (due to dehiscence, impact and cleaning shoe) and the dehulling capacity of the combine harvester’s cleaning shoe. DIQ decreased significantly moisture content of capsules (7.32%) in comparison to the other treatments, while the lowest plant moisture was recorded in DIQ (62.38%) and GLY (59.12%). The use of DIQ triggered the highest impact seed loss (61.75%) in comparison with GLY (46.50%) and DEF (29.02%). Control plants could not be harvested mechanically due to the high residual moisture content and high density of weeds. The present case of study provides highlights regarding the need to further investigate the best practice to terminate castor plants and to develop a specific combine header to reduce seed loss from impact.