Agronomy

The increasing generation of sewage sludge (SS) and the accumulation of agricultural residues such as vine pruning residues (VPR) represent significant environmental challenges, including pollution risks and resource underutilization. Composting offers a sustainable strategy to transform these wastes into high-quality compost, facilitating resource recovery within a circular framework. This study aimed to evaluate the feasibility of co-composting SS with VPR as a strategy for organic waste valorization. Two mixtures were prepared using cattle slurry solid fraction (CS) as inoculum, M1 (50% SS + 30% VPR + 20% CS) and M2 (30% SS + 50% VPR + 20% CS). The results showed that both mixtures exhibited typical composting temperature profiles, with the thermophilic phase effectively eliminating Salmonella and E. coli, confirming adequate hygienization. Macronutrient concentrations were consistently higher in M1 (N: 43.44, P: 12.41, and K: 25.27 g kg⁻¹ DW) than in M2 (N: 32.14, P: 8.57, and K: 23.66 g kg⁻¹ DW). All potentially toxic elements remained below the regulatory thresholds established by Ordinance No. 185/2022. Compost maturity was confirmed in both treatments by final C/N ratios below 20, holocellulose/lignin ratios below 1.8, N-NH₄⁺ concentration below 300 mg kg⁻¹ FW (only M2 satisfied this criterion), and N-NH₄⁺/N-NO₃⁻ below 3. However, M2 achieved a very stable respiration rate of 1.95 mg CO₂ g⁻¹ OM d⁻¹ and a germination index of 90.22%, while M1 recorded a respiration rate of 2.38 mg CO₂ g⁻¹ OM d⁻¹ and a lower germination index of 74%. The findings suggest that while M1 is a superior source of macronutrients, M2 provides a more stable and less phytotoxic organic amendment, with both being safe for agricultural soil application.

Climate change has intensified plant water stress due to rising temperatures and irregular rainfall, which often fails to meet crop water requirements. Consequently, irrigation has become essential for optimizing the yield of drought-sensitive crops such as maize. Drought-tolerant (DT) maize hybrids represent a promising strategy to increase resilience under water-limited conditions. This study evaluated the qualitative, morpho-physiological traits, and yield of six maize hybrids, comprising one drought-tolerant (DT) and one conventional (Conv) hybrid for each of three maturity classes (FAO 300, 400, and 500), in Veneto, northeastern Italy. Hybrids were grown under rainfed and fully irrigated conditions. Irrigated plots received 51.7% more water than the rainfed ones. Irrigation increased plant height by 20.4%. At full development, irrigation raised the plant dry weight by 19.7% and ear weight by 24.7%, relative to rainfed management. At harvest time, the grain yield was 48.7% higher under irrigation than under rainfed conditions. No significant effect of drought tolerance was observed on grain yield. Rainfed maize produced grain with higher protein content. Grain from the DT hybrids had lower protein but higher oil content than grain from the Conv hybrids. Therefore, in environments characterized by high temperatures and irregular but not extremely limiting rainfall, management strategies that secure adequate water supply during the reproductive stages remain more effective for sustaining maize productivity than the sole adoption of DT hybrids. These findings should be confirmed through multi-year, multi-site experiments covering a wider range of water availability conditions.

Flooded rice paddies emit large quantities of greenhouse gases, and biochar amendment serves as a promising strategy to conserve water, sequester carbon, mitigate emissions and stabilize crop yields. Nevertheless, the DNDC (DeNitrification-DeComposition) model has no specific biochar module and fails to precisely quantify coupled water–carbon–nitrogen cycles in biochar-amended paddies. Using two-season field observations from the Jianghan Plain, this study constructs the Biochar-DNDC model by introducing biochar pH and substrate adsorption parameters into the original organic fertilizer module and coupling a double-tank exponential decay model. Five biochar application rates (0, 1.5, 3, 4.5, and 6 kg∙m⁻²; CK, BC1.5, BC3, BC4.5, BC6) were set. Combined with the 40-year historical precipitation series of the study area, five hydrological year types were classified to carry out multi-scenario simulations. The results indicated that, compared with DNDC, Biochar-DNDC improved the simulation accuracy by an average of 28.4%. In terms of RRMSE, Biochar-DNDC improved the simulation accuracy of yield, SOC, CH₄, and N₂O by 37.0%, 28.7%, 28.6%, and 42.1%, respectively. Environmental temperature, precipitation, soil bulk density, optimal rice yield, and the proportion of straw returned to the field were key sensitive factors regulating water–carbon–nitrogen fluxes. Biochar reduced irrigation water use by 6.3~28.5% while promoting the accumulation of soil carbon stocks, optimizing nitrogen-use efficiency, and suppressing greenhouse gas emissions. There was a significant interaction between rainfall regime and biochar: DOC and NH₄⁺-N were higher in wet years, while NO₃⁻-N tended to accumulate in arid conditions. Biochar weakened the positive driving effect of precipitation on net primary productivity (NPP). Rice yield, NPP, and net ecosystem exchange (NEE) first increased and then decreased with increasing biochar dosage. Overall, the optimal dosage of biochar for water conservation, carbon sequestration, yield increases, and emission reductions in paddy fields on the Jianghan Plain was 4.5 kg∙m⁻². This study develops a modeling tool for the carbon and nitrogen cycles in biochar-amended paddy fields, which can provide quantitative support for low-carbon water and fertilizer management in the rice-growing regions of the middle Yangtze River Basin.