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.
Plant Nutrition, Soil Fertility and Fertilizers
Esmaeil Dordipour; Zeinab Bastamikojour; Mojtaba Baranimotlagh; Abdolreza Gharanjiki; Mohsen Olamaee
Abstract
Introduction The most important constraint in maize crop yield in developing contries worldwide, and especially among resource-poor farmers, is soil infertility. Therefore, maintaining soil quality can reduce the problems of land degradation that decreases soil fertility and rapidly declining production ...
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Introduction The most important constraint in maize crop yield in developing contries worldwide, and especially among resource-poor farmers, is soil infertility. Therefore, maintaining soil quality can reduce the problems of land degradation that decreases soil fertility and rapidly declining production levels that occur in large parts of the world which needing the basic principles of good farming practice. For optimum plant growth, nutrients must be available in sufficient and balanced quantities. After nitrogen, phosphorus is the most limiting nutrient for crop yields, and is essential for maize growth and development. Large quantities of chemical fertilizers are used to replenish soil N and P, resulting in high costs and severe environmental contamination. Maize quantity and quality are increased by utilization of fertilizers, which has become the most important objective of these products worldwide. Phosphorus, is the second most important macronutrient required by the plants, next to nitrogen, and is reported to be a critical factor of many crop production systems due to its limited availability in soluble forms in the soils. The low availability of P to plants is because the vast majority of soil P is found in insoluble forms, and plants can only absorb P in two soluble forms, the monobasic (H2PO4-) and the dibasic (HPO42-) ions. Crop plants can therefore utilize only a fraction of applied phosphorus, which ultimately results in poor crop performance. To rectify this and to maintain soil fertility status, frequent application of chemical fertilizers is needed, though it is found to be a costly affair and also environmentally undesirable. Moreover, phosphorus (P) is an essential nutrientionl element for plant growth. Calcareous soils are frequently characterized by the low availability of P for plant uptake due to the low solubility of P compounds present in soils at high pH and the formation of relatively insoluble complexes, e.g., Ca-P. Many soils in Iran have received large amounts of P fertilizer and consequently contained a high level of available P. On the other hand, the root exudation of organic acids has been suggested to increase P availability in calcareous soils. The most common low-molecularweight organic acids (LMWOAs) identified in soils include oxalic, succinic, tartaric, fumaric, malic, and citric acids and are derived from the decomposition of soil organic matter in the upper soil horizons, microbial metabolites, canopy drip, and root exudation. The concentrations of organic acids in the rhizosphere or in soil solutions vary greatly and range from 10-2μM to over 80 mM. The ability of organic acids to release inorganic anions, such as P, has been reported and has been attributed to desorption of inorganic anions and solubilization of phosphate compounds. LMWOAs and their corresponding anions play a very important role to increase P bioavailability. Many studies have been conducted about the role of organic acids in increasing P availability, but these studies focused on acid soils in which Fe- or Al-bound P is the main P fraction. For calcareous soils where Ca-bound P is the main P fraction, questions that whether organic acids can mobilize P or not still exist. Although, a number of results show that addition of organic acids, especially citric and oxalic acids to soils can solubilize significant quantities of fixed P and reduce the sorption of newly applied fertilizer P. However, there are few studies on the transformations of P fractions induced by organic acids or organic anions, which are important for understanding the mobilization mechanisms of P and for exploring better ways of using different forms of P in soils. The objective of this study is to examine the effects of some organic acids and anions on the solubilization and plant uptake of soil P in some calcareous soils of Golestan province, Iran. Material and Methods For this purpose, a factorial pot experiment in a completely randomized design with three replications was conducted on maize. The first factor was comprised of 6 soil types from various areas of the province and the second factor was consisted of a combination of phosphorus fertilizer and organic acids (1) control, (2) 50 mg P kg-1, (3 and 4) 50 mmol kg-1 of organic acids (oxalic and malic acids), (5) P + oxalic acid and, (6) tomato fruit residue (25% w). After 10 weeks, plants were harvested and the parameters such as plant height, fresh and dry weights, phosphorus concentration and its uptake were determined. Results and Discussion Results indicated that soil type effect was statistically significant on the plant fresh and dry weights (P≤ 0.05), height, concentration and uptake of P (P≤ 0.01), respectively. Results also showed that the tomato fruit residue treatment in comparison with P fertilizer and malic acid treatments results in a significant increase in P taken up, and fresh and dry weights (P≤ 0.05). There was a significant difference between P fertilizer + oxalic acid and oxalic acid alone treatments in only plant height (P≤ 0.05). Also, no significant differences in terms of measured plant parameters were observed between malic acid and blank treatments (P≤ 0.05). Conclusion Application of tomato fruit residue rather than P fertilizer can help to take up residual soil P, to grow plants and to decrease of environmental pollution, and to be also affordable economically.