Due to soils from arid regions with high lime and low organic matter content, farmers receive low yields along with high costs of agricultural inputs, which causes them to look for a solution. In this context, Arbuscular mycorrhizal fungi (AMF) have great potential to reduce fertilizer use by mediating soil nutrient cycles. However, little is known about studies of AMF inoculum on microbial biomass carbon (C), nitrogen (N), and phosphorus (P) cycling during vetch plant vegetation in calcareous areas. In this study, changes in soil biogeochemical properties related to soil C, N, and P cycling were investigated with five different AMF inoculations under vetch (common Vetch (CV; Vicia sativa L.) and Narbonne Vetch (NV; Vicia narbonensis L.) growing conditions. For the field study, a total of five different mycorrhizae were used in the experiment with the random plots design. AMF inoculation decreased the lime content of the soil, and the highest decrease was observed in NV with Glomus (G.) intraradices + G. constrictum + G. microcarpum inoculation (24.41 %). The highest MBC content was recorded in CV vetch G. intraradices (1176.3 mg C kg^-1) and the highest MBN content in NV vetch G. intraradices + G. constrictum + G. microcarpum (1356.9 mg C kg^-1). CAT activity of soils was highest in CV vetch G. intraradices (31.43 %) and lowest in NV vetch G. intraradices + G. constrictum + G. microcarpum (72.88 %), urease enzyme activity decreased in all treatments except G. constrictum + Gigaspora sp. and G. mosseae inoculations in CV. The highest DHG activity was detected in GF (15.72 %) AMFs in CV and GI (21.99 %) in NV. APA activity was highest in Glomus constrictum + Gigaspora sp. (23.33 %) in CV and Glomus fasciculatum (10.08 %) in NV. In CV plots, G. intraradices + G. constrictum + G. microcarpum (91.67 %) isolates had the highest and G. intraradices community had the lowest RC% (97.33 %) in mixed mycorrhiza species, while in NV plots G. fasciculatum inoculum had the highest and G. intraradices community had the lowest RC%. This study has important implications for the application of AMF for sustainable agriculture. When the results of the study were evaluated, the most effective AMF isolates in terms of C, N, and P cycles were G. constrictum + G. fasciculatum + Gigaspora sp. in Common vetch variety, and G. intraradices in Narbonne vetch variety.

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.