Cotton plant has two physiological development periods which are vegetative and generative periods. The activities of urease, dehydrogenase, glucosidase and alkaline phosphatase enzymes in the soil continue during the growth of plants. In this study, three different fertilizer sources (diammonium phosphate (DAP), vermicompost and manure) and two cotton varieties (Candia and Lima) were used in non-saline and saline soil conditions. The experimental layout was randomized plots with 3 replications. Total chlorophyll content of Candia and Lima cotton (Gossypium hirsutum L.) cultivars and urease, dehydrogenase, glucosidase and alkaline phosphate enzyme activities of the soil were determined. The chlorophyll content of cotton plants was significantly (p < 0.01) different in fertilizer treatments applied in non-saline and saline soils. The lowest chlorophyll value (17.83) in non-saline soil was obtained in the control, while the highest chlorophyll value (32.64) was recorded in the DAP fertilizer treatments. The lowest chlorophyll value (20.33) in saline soil was obtained from DAP fertilizer, while the highest chlorophyll value (24.11) was obtained in the vermicompost application. The fertilizer treatment significantly affected the urease activity in non-saline (p < 0.01) and saline (p < 0.05) soils. The highest mean urease enzyme activity in non-saline (102.74 µg N g⁻¹dry soil h⁻¹) and saline (120.23 µg N g⁻¹dry soil h⁻¹) soils was obtained in the DAP treatments. The highest mean dehydrogenase enzyme activity in non-saline (35.99 µg TPF g⁻¹dry soil 24 h⁻¹) and saline (48.63 µg TPF g⁻¹dry soil 24 h⁻¹) soils was obtained in cattle manure application. The difference between fertilizer applications was significant at p < 0.01 level in both soils.

Biochar production from organic waste offers an important alternative for waste management, also improves soil properties (bio-physico-chemical) and reduces heavy metal pollution risk caused by the excessive use of chemical fertilizers applied directly to the soils. Biochar is also proposed as an important management strategy to mitigate the negative impacts of greenhouse gases, which are among the most important causes of global climate change. This study aimed to investigate the effects of biochars produced from six different plant wastes on soil enzyme activity, CO₂–C emission, total nitrogen (Nt), and nitrate (NO₃–N) concentrations. Almond shell (AS), tobacco waste (TW), pomegranate peel (PP), cotton waste (CW), orange peel (OP), and wheat straw (WS) biochars were applied to the soil at the rates of 0.5, 1.0, and 1.5%, and the biochar amended soils were incubated in the laboratory environment (25 ± 2) for 37 weeks. The highest CO₂ ̶ C emission was recorded in OP biochar treatment, while the lowest emission was measured in PP treatment, indicating that OP biochar addition tended to decrease C mineralization in the soil. The addition of AS biochar significantly increased the dehydrogenase and urease enzyme activities, while urease activity did not show a significant increase. The results can be attributed to the differences in composition and properties (C: N ratio, pH) of the biochars applied as well as the nature of the feedstocks used in biochar production. Biochar applications increased the Nt and NO₃–N concentrations of the soils, and the highest increase was obtained in the WS treatment. The results of the study revealed that PP biochar can be recommended to reduce CO₂–C emission from soils, AS biochar has a significant effect on urease and dehydrogenase enzyme activities, and the effect of WS biochar on Nt and NO₃–N concentrations of soils were higher than the other five biochar types.

This study was carried out to examine the interaction of enzyme activities, microbial biomass carbon, and CO₂ respiration with heavy metals under different land uses in terms of quality and sustainability of the soil. There is a statistically significant positive correlation between dehydrogenase enzyme activity and Mn, Pb, Cd, and Co, while it was negative between Cr. There was a positive correlation between catalase enzyme activity and Mn and Pb and between urease and Co. The higher interaction of dehydrogenase activity with heavy metals, which is included in the endo enzyme group, has been explained as a much stronger effect of heavy metals on living microorganisms and endoenzymes than extracellular enzymes stabilized on clay minerals and organic matter. The high clay content of the soil is thought to reduce some of the negative effects of heavy metals on enzymes. The results of this study may be good indicators of enzyme activities, especially dehydrogenase, catalase, and urease, for soil health and quality, chemical degradation and restoration processes, and ecosystem functioning in soils contaminated or to be contaminated with heavy metals. It shows that the activities of these enzymes are very sensitive and can decrease rapidly in case of high concentrations of heavy metals.

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.

This study aimed to evaluate the effects of molybdenum (Mo) and arbuscular mycorrhizal fungi (AMF) on soybean (Glycine max L. (Merr.) growth parameters, soil enzyme activities, AMF colonization, and spore densities under saline and non-saline soil conditions. The experiment included a control treatment along with three Mo doses (0%, 0.3%, and 0.6%) in both saline and non-saline soils. Additionally, AMF species from the Glomus genus (G. intraradices, G. constrictum, and G. microcarpum) were applied. The results showed that co-application of Mo (0.6%) and AMF increased plant growth parameters, including plant height (65.91%), stomatal conductanc (67.01%), SPAD value (18.45%), root lengt (48.67%), root fresh weight (2.58%), and root dry weight (22.15%) (p < 0.01). Soil biochemical parameters, such as catalase (CAT:85.17%), urease (53.19%), and dehydrogenase (DHG:56.21%) activities, were also increased at 0.6% Mo + AMF application (p < 0.01). The application of 0.6% Mo + AMF resulted in significant improvements (p < 0.01) in soil and root mycorrhizal traits, particularly spore density (spores/g soil; 84.85%) and root mycorrhizal colonization intensity (M%; 27.63%). Overall, Mo + AMF applications substantially affected both plant and soil parameters. Among the treatments, 0.6% Mo + AMF showed the greatest synergistic effects, enhancing mycorrhizal colonization, enzyme activities, spore production, and overall plant growth. This studydoes not involveany human participants and is therefore not a clinicaltrial. Trial registration