Today, many different methods are applied for the correct use of foods and to prevent their deterioration. Ensuring healthy conditions for people in food consumption and consumption of healthy foods is very important for human welfare. In this study, food spoilage, the factors that cause food spoilage, its effects on a global basis, food transport systems (cold chain) and measures that prevent or delay food spoilage are discussed.

Soil microbial respiration (SMR) and microbial biomass C (MBC) are two important site quality indices that can be used to assess the health status and rate of carbon cycling in forest ecosystems during litter decomposition processes. The purpose of this study was to determine the relationship between SMR and MBC with soil organic matter (SOM) in mixed beech forests in a permanent plot in compartment 32 in Shastkolate Forest, Golestan province, northern Iran. Using systematic random sampling, tree characteristics were recorded and soil samples collected in 90 sample plots. SMR determined using Closed-Bottle method, MBC by fumigation-extraction method and SOM by Walkley-Black method. Linear regression analysis, ANOVA and Duncan test were conducted. In this study, four forest types including pure beech, beech-hornbeam, beech-maple and mixed beech were distinguished. ANOVA tests revealed significant differences (a=5%) between SMR and MBC in pure beech stands compared to other forest types. Linear regression showed positively significant relation between SMR and MBC with SOM. Regression R2 was about 0.89 indicating the importance of SOM in enhanced microbial richness and litter decomposition rate. Soil quality and health were shown to be highest in beech-hornbeam forest type, suggesting the importance of hornbeam intermixed with beech. Silviculturists should thus acknowledge the crucial role of hornbeam in silvicultural interventions.

The incidence of drought stress conditions in arid and semi-arid areas is considered as one of the most environmental constrains to soil microbial activity that can be limited by nutrient availability and microbial death increasing. The aim of this research was to study the effect of drought stress on soil microbial respiration and biomass in the presence of natural and synthetic superabsorbent polymers. Two natural superabsorbent (Coir-Dust “CO” and Saw-Dust “SD”) and two synthetic superabsorbent polymers (, A200 and A300 hydrogels) were added to soil under 30% and 70% of field capacity and soil microbial properties (respiration and soil microbial biomass carbon) were assayed. Results showed that by decrease of soil moisture from 70% FC (without moisture stress) to 30% FC (with drought stress), total microbial respiration declined for the control, CO and SD treatments (49-72%) and increased in synthetic superabsorbent-amended soils (188-221%). Microbial biomass C was lowered in all treatments with the exception of A300 hydrogel (10-59%) treatment. Finally, the results confirmed higher soil microbial activity with synthetic superabsorbent polymers than with other amendments under stressed conditions. Arid and semiarid areas, Drought stress, Microbial biomass, Soil microbiological respiration and Superabsorbent polymers and Synthetic materials.

Oil pollution is one of the most critical environmental contaminations that can affect soil's biological, physical, and chemical properties. To investigate the effects of long-term and natural oil pollution on soil microbial respiration, including basal respiration (BR) and substrate-induced respiration (SIR), and beta-glucosidase enzyme activity, 120 oil-contaminated soil samples were collected from 0-15 cm depth in the oil-rich region of Naft-Shahr in Kermanshah province with three pollution levels: high (H), moderate (M), and low (L). After measuring the physical and chemical properties of the soils, the total bacteria and oil-degrading bacteria were counted on NA and CFMM culture media, respectively. This finding showed a positive and significant correlation between microbial population and oil concentration. The average oil percentage measured by Soxhlet extraction was 4.03%, 9.95%, and 22.50% for L, M, and H levels, respectively. The results showed that with the increase in oil concentration in soil samples, BR and SIR increased, and the highest BR and SIR respiration rates were 0.053 and 0.234 (mgCO2.g-1.h-1) in H soils, respectively. The measured beta-glucosidase activity was also higher in the presence of oil pollutants, with the highest activity (24.78 µgPNP.g-1.h-1) in H soils and the lowest (6.09 µgPNP.g-1.h-1) in L soils. Finally, a Principal Component Analysis (PCA) was conducted, and the results showed that 72% of the variance among samples could be explained by the first two components (biochemical and physical components). Oil pollutants that are naturally present in the soil for an extended period lead to the adaptation of pollution-resistant microbial communities over time, increasing their abundance, microbial respiration, and the activity of enzymes such as beta-glucosidase.

Introduction Soils and landforms have a strong relationship and archive evidence of climatic and environmental changes. Alluvial fans are one of the most important landforms in arid and semi-arid regions of Iran. Climate changes in the Quaternary, especially in the late Pleistocene, had a significant effect on the evolutions of alluvial fans in arid and semi-arid regions. Alternate of sedimentation and soil formation in alluvial are the consequences of periodic climate change. Organisms are one of the main factors of soil formation. Biological crusts are part of organisms that are abundant in dry lands and especially in alluvial fans; however, their role in soil formation has been less studied. Biological soil crusts by providing the suitable biological activity, effect on trapping of aeoilian materials and hydrological processes affect the soil formation processes. The chemical properties of the soil affect the catabolic capacity of the soil and it is very different among the different layers of the soil. However, few studies have addressed the effect of processes on soil microbial respiration during change and evolution and pedogenic state. The objectives of this research were to 1) investigate the evolution of soils along the gradient from upstream to downstream of the alluvial fan and 2) investigate the changes in microbial respiration in different layers of soil and the factors affecting it.   Materials and Methods The studied area is an alluvial fan in Razavi Khorasan province, in the southern slopes of the Binaloud mountain range. The climate of the region is semi-arid and the soil moisture and temperature regimes are Aridic border on Xeric and mesic, respectively. Three soil profile in the upper, middle, and base part of the alluvial fan were described. Bulk and undisturbed soil samples were collected from various soil horizons for subsequent physical, chemical, and micromorphological analyses. In addition, the microbial soil respiration was measured in all horizons. The soils were classified according to Soil Taxonomy and World Reference Base ‎methods. ‎   Results and Discussion Sequences of sedimentation and soil formation were observed in the soil profiles. Vesicular (V), argillic (Bt), argillic-calcic (Btk), calcic (BCk) and cambic (Bw) horizons were the diagnostic soil horizons of the studied soils. Soil profiles of the middle and base were Xeric Calciargids in the subgroup category of Soil Taxonomy; while soil profile of the apex soil was Xeric Haplocambids. In the profiles, a thin vesicular horizon (V) was formed under the desert pavement. Below the vesicular horizon, evidence of clay illuviation, pedogenic carbonate nodules, and calcium oxalates in roots were observed in thin sections. This evidence shows the role of biological crusts in the formation of these features. In the lower horizons of the profiles, pedogenic carbonate nodules, carbonates pendants and clay coatings were observed. It seems that the upper soil (vesicular and underlying Bt horizons) were developed in the more humid periods of the Holocene, and biological crusts also played a key role in the processes of calcification and clay illuviation. The argillic horizons in the lower layers were formed during the stable periods of the late Pleistocene. The irregular microbial respiration mainly indicated difference in microbial activities labile organic matter content. The argillic horizons had the lowest microbial respiration, due to decomposition of organic materials during soil formation. In contrast, soil respiration was the highest in surface and calcic horizons. It seems that preservation of organic materials by carbonate complication. However, it is suggested to investigate the carbon fractions in relation to microbial biomass in the studied horizons.   Conclusion In this area, biological crusts and vegetation affected the formation of soil in the aeolian sediments of the Vk and AVk horizons and played a significant role in creating the Bt horizon in profiles 2 and 3. The study of landform profiles showed the formation of calcic and argillic horizons in the past climate, while the Bt horizon of the upper layers was formed in the current Holocene period. This form of the argillic horizon is slightly different from the soils of the Iranian region because these horizons have not been reported so far. It has been proven that there were humid periods in the Holocene, and it needs more studies at present. The study of soil microbial respiration in landform horizons showed that argillic horizons decreased the amount of microbial respiration, while it increased in classical horizons.

In order to identify and sustainable management of afforested tree stands, the effects ofAlnus subcordata, Acer insigne, Sequoia sempervirens and Acer insigne - Sequoia sempervirens stands on quality of litter and soil were investigated in Salmanshahr areas of Mazandaran Province. Samplings were done from the litter and 0-10cm depth of topsoil using randomly systematic method with 15 replicates for each stand. Organic carbon (C) and total nitrogen (N) content of litter, soil water content, pH, organic C, total N, nitrate and ammonium concentration, microbial respiration, microbial biomass of C and N were measured. Results showed that the highest values of soil water content, litter and soil N, nitrate and ammonium concentration, microbial respiration, microbial biomass of C and N belonged to Alnus subcordata compared with Acer insigne>Acer insigne - Sequoia sempervirens>Sequoia sempervirens pure and mixed stands. Whereas greater amounts of C/N of litter and soil organic C were found under Sequoia sempervirens stand. Generally, Acer insigne - Sequoia sempervirens mixed stand presented intermediate mode viewpoint of litter quality and soil fertility. According to our data, afforestation with broad-leaved species, especially N-fixing trees of Alnus subcordata, improved the litter and soil quality, whereas the Sequoia sempervirens species created the inappropriate condition.

Salinity is an important environmental stress causing a negative impact on the soil biological activity. Application of organic and inorganic amendment in saline soil can modify the adverse salinity effects on microbial activity and biochemical characteristics of rhizosphere. The objective of this study was to investigate the effect of irrigation water salinity and organic and inorganic amendments on microbial respiration and soil acidic and alkaline phosphates activity in second node and full bloom stages of soybean. A factorial experiment consisting of five salinity levels (i.e. S1=0.8 S2=1.6 S3=3.2 S4=4.8 and S5=6.4 dS m-1 from the sea water source) and five amendment treatments including T1 (control without amendment), T2 (20 t ha-1 gypsum), T3 (20 t ha-1 manure), T4 (10 t ha-1 gypsum+10 t ha-1 manure), T5 (15 t ha-1 gypsum+15 t ha-1 manure) arranged as randomized blocks design with three replications was conducted under greenhouse conditions in 2009. Results indicated that irrigation water salinity reduced soil microbial respiration and acidic and alkaline phosphates activity in the second node (V2) and full bloom (R2) stages of soybean. But application of soil amendments (organic and inorganic) were increased biological indicators. In the second node stage (V2), application of organic amendments (T3) at all salinity levels had most microbial respiration and enzyme activity in comparison to control treatment. Microbial respiration, acid phosphates and alkaline phosphates were increased by 55, 24 and 27 percent respectively. Soil microbial respiration and enzyme activity of acid and alkaline phosphates in the full bloom stage (R2) decreased with salt accumulation by saline irrigation water application. Using mineral and organic amendments together (15 t ha-1 gypsum+15 t ha-1 manure) had the greatest effect on microbial respiration and enzyme activity in different salinity levels in the full bloom stage (R2).

Cadmium is one of the heavy metals with a considerable importance for its potential toxic effects on soil microbial activities and composition. Although, the toxic effect of cadmium on soil microbial activities is somewhat well-known, but the extent to which Cd affects soil biota depends largely on soil properties and conditions, particularly soil organic matter contents. Thus, the aim of this research was to study the effect of increasing cadmium levels on soil microbial biomass and activities, and to examine the role of compost materials in the alleviation of Cd effects. A 2×5 factorial experiment consisting of two levels of compost (0 and 2.5 t ha-1) and five levels of cadmium (0, 50, 100, 150 and 200 mg Cd kg-1) arranged in a completely randomized design with three replicates was carried out under laboratory conditions. The responses of soil microbiological properties consisting of C mineralization, microbial biomass C; and acid and alkaline phosphatase activities to cadmium and compost additions were evaluated during 10 weeks of laboratory soil incubation. Results show that cadmium additions had a significant, negative effect on all the measured microbiological properties. The accumulated C mineralization reduced with increasing cadmium concentrations. Nonetheless, compost addition lowered the detrimental and inhibiting effect of cadmium on soil microbial activities. Results demonstrate that in spite of a significant correlation (r=0.96) between the two Cd fractions, the added Cd at the beginning of soil incubation was not reflected totally in the total Cd concentrations determined at the end of soil incubation. Data also indicated that the fraction of available Cd had a stronger negative (cor) relation with soil microbial activities than the other fractions had. In summary, the results of the current study illustrate that even a lower concentration of Cd (50 mg kg-1) may inhibit soil microbial activities due to it toxicity in the studied soil, and that the addition of organic materials could be effective in reducing the toxicity of cadmium via lessening its bioavailability to soil biota.

Unfavorable fertility and microbial activity are two limitations of saline sodic soils. This study focused on variation of nitrogen, phosphorous and potassium macronutrients and microbial respiration in ameliorating process of calcareous saline sodic soil. The experiment was factorial based on CRD using 6 soil treatments consist of control, cattle manure, pistachio residue, gypsum, and their combination; 2 water treatments (with and without sulfuric acid) and 3 replicates, which was conducted in laboratory conditions by soil column. Four intermittent irrigation steps with one month intervals and one pore volume were applied. Microbial respiration was measured during leaching operations, while at the end of experiments, macronutrients concentrations of nitrogen, phosphorous and potassium were determined at different depths. The results showed that both organic matters similarly added higher amounts of nitrogen to the soil compared to control and gypsum treatments. At the end of reclamation experiments, absorbable phosphorous decreased with depth for all of the treatments except to gypsum. The results also indicated that control and gypsum had the least while pistachio treatment showed the highest efficiency in improving availability of three study macronutrients. Additionally, in comparison to the untreated irrigation water, application of sulfuric acid in conjunction with irrigation water, led to an increase in absorbable phosphorous and potassium content. Investigation of microbial respiration showed that respiration rate was lower for control while, cattle manure found to have the highest rate. The findings of this research reveal that among different amendments, pistachio residue have the highest efficiency in increasing availability of macronutrients.

In order to investigate the effect of nickel (Ni) and cadmium (Cd) resulting from sewage sludge (SS) and municipal solid waste (MSW) contamination on the amount of microbial respiration and acid and alkaline phosphatase enzymes activity, a field experiment was conducted as randomized complete block design in split-plot arrangement with three replications in 2008. The main plot was SS and MSW at three levels (0, 20 and 40 ton/ha) and sub-plot, period of application (2006, 2006 and 2007, 2006-2008) was considered. The results showed that application of SS and MSW in the different treatments was significant on amount of heavy metals and biological factors. Application of 40 ha-1 ton sewage sludge, for three continuous years, increased the accumulation of Ni and Cd (total and available) in soil and decreased the acid and alkaline phosphates enzymes activity, but the accumulation of Ni and Cd did not have any negative impact on microbial respiration in all treatments. The total amount of Ni and Cd showed positive correlation (P<0.05) with the amount of microbial respiration and negative correlation (P<0.05) with acid and alkaline phosphates enzymes activity, respectively. Therefore, long-term application of SS and MSW, in addition to accumulation of heavy metals, can decrease enzyme activity and increase soil microbial respiration.