Fatemeh Hassani; Ataallah Khademalrasoul; Hosein Shekofteh
Abstract
IntroductionSoil is the upper layer of earth in which plants grow and is consequently very important for organisms and human nutrition. The protection of the soil against degrading processes, such as soil salinization and alkalization, is one of the main challenges in sustainable land management. Soil ...
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IntroductionSoil is the upper layer of earth in which plants grow and is consequently very important for organisms and human nutrition. The protection of the soil against degrading processes, such as soil salinization and alkalization, is one of the main challenges in sustainable land management. Soil salinization and alkalization are two major environmental concerns leading to soil degradation especially in arid and semi-arid regions across the world. The balance of organic carbon in the soil is important for soil sustainability. Intensive cultivation enhance soil organic carbon (SOC) depletion. In order to alleviate the detrimental effects of SOC depletion, carbon-rich organic amendments such as biochar or compost are often applied to the soil. Therefore application of organic amendments to soil is an effective strategy to improve soil properties and to mitigate the negative impacts of inappropriate management strategies. Biochar is a carbon-rich compound produced by the pyrolysis of biomass in oxygen-limited conditions. Its use as an organic amendment to soil with specific inherent characteristics has been recognized. In this regard recent studies have shown that application of biochar to soil as an organic amendment can improve soil physical properties and help to keep the carbon balance in the soil. Moreover, compost as an organic amendment is capable to improve soil properties and increase the soil productivity. Methods and MaterialsThe soil sampling was carried out near Kabutar Khan in Rafsanjan, Iran (56°22′N, 30°18′E), on a saline-sodic soil with Silty Clay soil texture (42% silt, 50% clay and 8% sand). The biochar was obtained from three different feedstocks consist of Conocarpus erectus, bagasse of Sugarcane and hard shell of Pistacia Vera. The obtained feedstocks were pyrolyzed at 400°C for 2 h with increasing rate of 7 °C/min in a sealed reactor to prevent O2 input (Muffle Furnace, SEF-101 Model). Afterwards the produced biochar was cooled slowly to the room temperature, then the EC, pH, specific surface area and CHNS of biochars were measured using the standard methods. The required amounts of soils and biochars were weighed by a total 5000 g dry weight of sample and mixed in the dry state. The soil samples were received three doses of biochar (0, 2, 4 % biochar, w/w). The mixtures of soil and biochar were packed into pots and controlled a bulk density of about 1.5 g cm-3 by artificial compaction. Treatments were replicated three times. The soil without any biochar was used as the control. The mixtures were wetted at three soil moisture contents (25, 50 and 75% field capacity) during incubation time (120 days). The treatments were kept at a temperature-controlled glasshouse. After 120 days of incubation, the untreated soils and biochar-amended soils were taken for physical and chemical analyses.Particle size distribution was measured by hydrometer method and soil organic carbon by oxidation method with potassium dichromate. The consistency limits (liquid limit and plastic limit) of soils were determined according to the ASTMD4318 procedure. The field capacity was measured using the pressure plates with the standard rings in the lab. Mechanical strength is a sensitive indicator of the soil physical condition and has been commonly used to evaluate soil water erosion, structural stability, tillage performance, and root penetration. Higher strength found in saline-sodic soil often impedes seedling emergence and root penetration. Results and discussionOur results revealed that application of organic matter in the form of biochars and compost was effective on soil aggregation. The formation and stability of the soil aggregates play an important role in the crop production and soil degradation prevention. Moreover, the biochar application showed two main effects including direct and indirect effects. Our results confirm the addition of biochar to soil can cause a substantial and significant change in the soil physical characteristics of the strongly acidic Ultisol, namely a significant increase in LL and PI, higher water-holding capacity, and reduction in mechanical strength. These changes are undoubtedly associated with the particular properties of biochar and in particular with its high porosity and low bulk density. The beneficial effect of biochars on soil physical properties is mainly due to the dilution effect of biochar with higher porosity and lower density. When the biomass is heated, volatile matters may release out of the biomass to create micropores on the surface, and meanwhile those trapped inside the biomass are evaporated to expand the microstructure. Thus, the resulting biochar has much higher surface area and porosity. These properties are particularly useful for soil application of biochar especially for enhancing soil water-holding capacity, reducing mechanical strength, and increasing soil aggregation. The dilution effect can be attributed to the increased volume of pores as well as the decreased particle density in soil amended with biochar. The effectiveness of different biochars in improving the soil physical properties can be explained by their porosity and bulk density.ConclusionOur results depicted that application of biochars and compost as an organic amendments improved mechanical quality of the saline and sodic studied soil. Indeed all organic treatments decreased bulk density and enhanced soil aggregate stability while the biochar of Conocarpus illustrated the greatest effectiveness on soil physical and mechanical properties. Therefore it is a possibility to apply this biochar to the soil in the field scale but regarding the accessibility of biochar of Pistachio skin in the study area therefor we have another alternative to utilize in the soil. This research was conducted in the small scale and in a short time. Therefore, it is suggested that supplementary studies are carry out on farm scale for a longer periods.
Soil Biology, Biochemistry and Biotechnology
Maryam Talebi Atouei; mohsen olamaee; REZA GHORBANI NASRABADI; seyed alireza movahedi Naeini
Abstract
Introduction Salinity is the most important challenge in arid and semi-arid regions. Salt stress, ionic and osmotic components, like other abiotic stresses, lead to oxidative stress that damage cellular membranes, nucleic acids, oxidizing proteins, and causing lipid peroxidation through overproduction ...
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Introduction Salinity is the most important challenge in arid and semi-arid regions. Salt stress, ionic and osmotic components, like other abiotic stresses, lead to oxidative stress that damage cellular membranes, nucleic acids, oxidizing proteins, and causing lipid peroxidation through overproduction of reactive oxygen species (ROS). Antioxidant capacities and osmolytes play a vital role in protecting plants from salinity that causes oxidative damages. Applying biological methods such as using of halotolerant plant growth promoting rhizobacteria (PGPR) is very important to reducing the harmful effects of salinity on plants. Also exopolysaccharide production by plant growth-promoting strains helps in binding cations, including Na+, and thus decreases the content of Na+ available for plant uptake. This is especially useful for alleviating saline stress in plants. Biochar can also alleviate the negative impacts of salt stress in crops. Biochar can enhance plant growth either by its direct or indirect mechanisms of actions. The direct growth promotion relates to supplying mineral nutrients, such as Ca, Mg, P, K and S etc., to the plant, whereas, indirect mechanisms involve improving soil physical, chemical and biological characteristics. Materials and Methods In this research, the effect of halotolerant plant growth promoting bacteria, biochar and gypsum was investigated on enzymatic and non-enzymatic defense mechanisms of barley such as Catalase, Superoxide Dismutase, Proline and Membrane stability under salinity stress. The experiments were carried out as a factoria with a completely randomize design in greenhouse conditions for 2016-2017. The factors included: bacteria (without inoculation (T0), bacterial isolate T5 (megaterium Bacillus), bacterial isolate T17 (licheniformis Bacillus ), biochar (0 and 5percent w/w), gypsum ( 0and 50 percent gypsum requirement ) and soil leaching (without and leaching with) with three replications. The activity of catalase (CAT) was determined by changes in absorbance at 240 nm (IUg−1FW) (Aeby, 1984). Superoxide dismutase (SOD) activity was determined by nitroblue tetrazolium (NBT) reduction, according to Minami and Yoshikawa (1979) and the enzyme activity was expressed as (IUg−1FW). Proline content was estimated according to Bates et al., (1973) and expressed as µ mol g−1 fresh weight (FW). Membrane stability was estimated according to Sairam and. Saxena (2001). All statistical analyses were performed using SAS software. The means of different treatments were compared using LSD (P ≤0.05) test. Results and Discussion The results showed that using halotolerant bacteria and biochar reduced the activity of antioxidant enzymes in barley plants. This reduction was higher in the treatment containing bacteria T17 (Bacillus licheniformis) biochar and with leaching. Also, inoculated plants with both bacteria had the highest concentration of proline, which was significantly higher in the treatment containing bacteria T17 (Bacillus licheniformis) biochar and gypsum. Also, application of halotolerant bacteria, biochar and gypsum improved the membrane stability of plant. This increase has been remarkable in inoculated treatments with T17 bacteria (Bacillus licheniformi) in saline soil with leaching associated with 50 percent gypsum requirement Conclusion Generally, results showed that halotolerant bacteria, biochar and gypsum can be used as a tool for reducing adverse effects of salt stress. Inoculation of soil with these bacteria has helped in alleviating saline stress by changing several physiological, enzymatic, and biochemical agents in plant. Bio-remediation of salt affected soils is one of the cheap and eco-friendly approaches for remediation of salt affected lands as the traditional physical and chemical techniques are becoming costly. The plant growth promoting halotolerant bacteria helps in Bio-remediation of salt affected soils and thereby improving the agricultural crop yields. Incorporation of biochar into salt-affected soil could diminish salinity stress by decreasing soil bulk density, increasing in soil cation exchange capacity, potassium and calcium concentrations, water holding capacity and nutrient and water availability in soil. Also, bichar due to high organic matter content can play a dramatic role in salt affected soil with organic compound defficiency. According to these amended features of biochar in soil, we suggest, more experiments conducted by biochar with different material and ratios under saline - sodic soils.