This study aims to investigate the effects of the combined treatment of biochar (BC) and arbuscular mycorrhizal fungi (AMF) on cotton plants, focusing on morphological and physiological characteristics, nutrient content, and soil enzyme activities. The study examined the effects of different biochar doses in mycorrhiza-inoculated (M +) and non-inoculated (M −) treatments (0% BC + 200 kg N ha⁻¹, 1.5% BC + 200 kg N ha⁻¹, 3% BC + 200 kg N ha⁻¹). The results showed that the highest SPAD value (34.66%) was observed in the M( +) + 3.0% BC treatments. NDVI values increased by 25.29% in M( +) + 3.0% BC treatments. M( +) treatment increased the N, NO₃ ⁻, and soil enzyme activity was higher in the M( +) treatment. However, enzyme activity decreased as BC dose increased in both M( +) and M( −) treatments, with the most significant decrease observed in the 3.0% BC treatments. Nitrate reductase enzyme activity (NRA) decreased in all treatments except the 3.0% biochar treatment. M( +) treatment increased soil urease content by 27.24% compared to the M( −) treatment. Additionally, plant height, root length, nodule count, and spore number increased with increasing biochar doses, with the highest increase observed in the M( +) + 3.0% BC treatments. Positive correlations were found between SPAD, NDVI, and nutrients such as Fe, Cu, Mn, and root attributes. Negative correlations were observed with Mg and CAT enzyme activity. Urease, DHG, and CAT enzyme activities decreased significantly with increasing BC doses, particularly in M( +) treatments. Biochar and AMF co-treatment enhanced growth, root parameters, spore count, NDVI, SPAD, and soil and plant enzyme activities in cotton plants. The combined treatment of biochar and AMF is beneficial for cotton production. The findings of this research have significant potential implications for sustainable cotton production and soil management practices, particularly in optimizing mycorrhiza and biochar to enhance soil fertility, improve water retention, and reduce the need for chemical fertilizers.

In semi-arid climates, the management of pig slurry is very important, since it may cause an environmental problem, but on the other hand it has positive impacts such as high labile and organic carbon content. Leaching experiments were carried out to establish the mechanism of soil C dynamics using the raw pig slurry with legislated doses (LD) (170 kg ha⁻¹year⁻¹) and the high doses (HD) (510 kg ha⁻¹year⁻¹). Organic carbon (OC) content of the soil ranged between 6.81 and 15.50 tons OC ha⁻¹ at the beginning, which ranged between 11.39 and 26.26 tons OC ha⁻¹ at the end of the experiment and significantly increased with the HD, especially in the subsurface zone. Carbon lost from the soil respiration was ∼0.01 ton C–CO₂ month⁻¹ha⁻¹ in control and varied between 0.01 and 2.30 ton C–CO₂ month⁻¹ha⁻¹ in LD, and 0.01 and 7.16 ton C–CO₂ month⁻¹ha⁻¹ in HD, respectively. The losses of OC by leaching from dissolved organic carbon (DOC) were 0.15, 0.07, and 16.30% with LD, HD, and the control (CT), respectively. Dissolved OC content in leachates was lower in LD treatment than in HD treatment. The changes of OC from the beginning were between +15.85, +24.65, and −0.8% (+1.97, +3.15, and −0.11 ton OC ha⁻¹) with LD, HD, and CT, respectively. Results suggest that the agronomic rate (LD) application could be considered as a fertilizer treatment in terms of soil C sequestration.

This study aimed to assess the effects of black cumin ( Nigella sativa ) residue and its biochar on soil microbial activity, carbon sequestration and nitrogen cycling in three soil types: Alfisol, Entisol and Mollisol. A 120‐day incubation experiment was conducted to evaluate changes in soluble carbon (SC), microbial biomass carbon (MBC), soluble nitrogen (SN), microbial biomass nitrogen (MBN), CO ₂ emissions, carbon use efficiency (CUE) and metabolic coefficient (qCO ₂ ), calculated to understand microbial functionality and carbon retention. The results revealed that biochar (BC) enhanced long‐term carbon stabilisation, while black cumin residue increased microbial activity and short‐term nutrient turnover. In the BC2 treatment, SC remained stable until day 120 (419.2 mg/kg), suggesting sustained carbon availability. The highest MBC (528 mg kg ⁻¹ ) and lowest CO ₂ emissions were also recorded under biochar treatments, reflecting improved microbial efficiency. Significant interactions ( p < 0.001) were observed between soil type, treatment and sampling time. These findings suggest that the combined use of biochar and plant residues can enhance both immediate microbial responses and long‐term soil health, offering a sustainable strategy for soil fertility improvement and carbon management across different soil systems.

Şanlıurfa province has 36% of the agricultural areas in Turkey and 64.1% of the agricultural areas in the GAP Region. With approximately 600 000 tons of chemical fertilizer consumption in 2021, it is the province with the most fertilizer consumption in Turkey. This causes some negative and high environmental risks such as salinization in the soil, heavy metal (HM) accumulation, deterioration of nutrient balance, damage to microorganism activity, and formation of eutrophication in the region. The objective of this study was to determine the HMs (Zn, Ni, Mn, Cu, Mo, Pb, Cd) concentrations of the soils and some commercial fertilizers overused, and evaluate their interactions with soil properties. The average values of HM concentration of the soil are as follows; 32.65 and 46.88 mg kg-1 Zn; 649.03 and 730.58 mg kg-1 Mn; 79.86 and 95.54 mg kg-1 Ni; 0.15 to 0.27 mg kg-1 Cd; 0.26 and 0.97 mg kg-1 Mo; 8.54 and 18.67 mg kg-1 Pb; 19.45-25.37 mg kg-1 Cu. HM contents of some fertilizers were found to be very high in this study. This causes an increase in the HM concentration in the soil. HMs concentrations of several soil samples exceeded the threshold level of Europe standards except for Ni, Mo, and Mn. Study results can help the authorities to develop effective fertilizer management strategies for the Harran Plain, which has once again revealed the necessity of applying agricultural activities such as fertilization with a fertilization program prepared under expert control according to the results of soil analysis.