مجله زیست شناسی خاک
سال پنجم شماره 2 (زمستان 1396)

Plant inoculation with effective plant growth promoting and heavy metal resistant rhizobacteria is an efficient method to improve the phytoremediation efficiency and extraction of heavy metals from contaminated soils. With respect to this reason, astudy was conducted to isolate, identify and evaluate the growth stimulating traits of copper-resistant bacteria from a Cu-contaminated soil. Six rhizospheric soil samples of indigenous plants were collected in Sarcheshmeh Khatoonabad, Kerman province. After screening, six strains were selected. Phenotypic, biochemical and genetic identification data showed that five and one isolates were belong to Pseudomonas and Bacillus genera respectively. Then, the minimum inhibitory concentration of copper, siderophore production, auxin and hydrogen cyanide production, the ability to solubilize mineral phosphate in solid and liquid medium, the ability to solubilize Zn low soluble compounds in solid and liquid medium and production of ACC-deaminase were investigated. The results indicated that all of the isolates were resistant to various concentrations of copper. The maximum resistance to inhibitory concentration of copper was related to K4 and K5 strains at a concentration of 400 mg L-1 of copper. All of the strains were able to produce siderophore in CAS medium except for K6 strains and strain K5 was also the superior in siderophore production. Among the strains, K4 and K6 were not able to produce auxin. There was also a significant difference between auxin productions by isolates K1 with the other isolates, with the highest auxin production (2.07 mg L-1). The results also demonstrated that among the strains, only K4 strain was capable of producing hydrogen cyanide (degree: four=relatively high) and the other isolates were reported as non-production of hydrogen cyanide (degree: one). The results of Three Calcium Phosphate (TCP) solubilizing by isolates in PKV broth medium showed that K1, K2, and K3 strains had the most phosphorus solubility (706, 661 and 588 mg L-1) respectively and there wasn’t significant difference between them. The results demonstrated that K4 and K5 isolates with 0.910 and 0.850 halos to colony diameter had a significant difference with other isolates in solid medium containing ZnCO3 and the rest of the strains, K1, K2, K3 and K6 did not show the ability to solubilize the zinc carbonate as well. The solubilizing of solid zinc oxide in solid medium by K4 strain (halo:colony, 2.11) was the highest solubility of zinc oxide and K1, K2, K3 and K6 strains were not able to dissolve the zinc oxide in the solid medium. They did not show the ability to dissolve the low soluble zinc oxide nor the zinc carbonate compounds. K4 strain had the highest zinc carbonate solubility in the broth (12.5 mg L-1) and the highest solubility of zinc oxide in the broth was attributed to K4 strain (9.76 mg L-1). According to the results, these isolates can be used for enhancing phytoremediation efficiency of this element in contaminated soils.

One of the major problems in calcareous soils is low efficiency of phosphorous (P) fertilizers due to rapid precipitation. Lowering soil pH is mentioned as a solution for solubility of precipitated P. In order to investigate the effect of sulfur (S) and thiobacillus sp. bacteria and P fertilizer on canola (Brasica napus L. cv. Hayola-401) yield and nutrient concentrations in soil and plant, an experiment was carried out during cropping season 2012-13, in a calcareous soil which was generally poor in P content. The experimental factors were designed in a complete randomized blocks with factorial arrangement in three replicates. The first factor consisted of S, in 4 levels (0, 500, 1000 and 2000 kg.ha-1) as pastille form as elemental sulfur with sulfur oxidizing bacteria (in 2% rate of sulfur weight) and the second factor including 3 P levels (0, 72 and 110) kg.ha-1)as triple superphosphate. There was a positive and significant interaction between S and P levels on seed and aerial part yield and yield component (p

The activities of earthworms and mycorrhiza affect on water and nutrient uptake and crop yield. The aim of this study was to evaluate the effect of earthworm (Eisenia fetida) and arbuscular mycorrhiza fungi (AMF, Funneliformis mosseae) on root colonization, shoot dry weight, phosphorus and nitrogen uptake, organic carbon and soil microbial biomass C. In this regard, a greenhouse experiment was conducted in a completely randomized design (CRD) with three replications in Agricultural Research Station of Ferdowsi University of Mashhad. The experimental treatments consisted of control, single and integrated treatments of earthworm and mycorrhiza. The results showed that inoculated treatments with arbuscular mycorrhizal fungi significantly increased the amount of root colonization. The same trend was observed in combined treatments with mycorrhizal fungi and earthworm. The results also revealed that the integrated application of earthworm and mycorrhiza treatment increased the concentration of P and N in shoot by 105% and 79% ,respectively, compared to control treatment (p

Todaysoil pollution with heavy metals, especially cadmium due to its abundance in agricultural land has gained much more attention.In the present research, the effects of 0, 2 and 5 mg Cd kgˉ¹ soil were studied on soil respiration, mineralization of organic matter, urease activity and nitrification in a sandy clay loamsoil containing 2% vermicompost. Cadmium concentrations were examined in a factorial layout with a completely randomized design (CRD) with three replications under laboratory conditions during 3, 7, 31, 62 and 93 days. Before starting the experiment, the soil incubated for two weeks with vermicompost to achieve consistency in biological conditions. The results showed that cadmium had significant effect on the soil respiration and soil organic matter content but it did not have any effect on the specific activity of urease and soil nitrate concentration. On the other hand, the results revealed that incubation time had a significant influence on all determined parameters including specific activity of urease, soil respiration, the organic matter content and the nitrate concentration (P 0.01). The correlation coefficient between cadmium and examined parameters showed that cadmium treatment had no effect on urease activity and nitrification process and probably other soil properties affect the nitrification and urease activity in soil sample. Our results demonstratedthat among investigated factors soil respiration and organic carbon percentage are the most sensitive ones in treated cadmium concentrations.

Application of arbuscular mycorrhizal fungi (AMF) and vermicompost in agriculture as promoting factors to improve the soil quality and plant nutrition, plant growth and yield, is considered as an important and valuable findings in soil fertility and plant nutrition. In order to study the effect of vermicompost and Rhizophagus irregularis fungi on some growth and nutritional responses of two wheat cultivars, a factorial experiment was conducted in completely randomized design (CRD) in greenhouse conditions. Treatments were included: two levels of Rhizophagus irregularis fungi (with and without fungi), two levels of vermicompost (with and without) and two wheat cultivars (Bahar and Shiraz). The results showed that the application of vermicompost increased the mean grain and straw yields of wheat cultivars by 57.8% and 65.6%, respectively, compared to the control. So that, grain and straw yields, total uptake of P, concentration and total uptake of N, total uptake of K and the percentage of root colonization in Bahar cultivar were significantly higher than Shiraz cultivar. The same results obtained in Rhizophagus irregularis fungi treatment. Remarkable increase was observed in the concentration and total uptake of P and N in straw for Bahar cultivar compared to the control. Whereas there is no significant effect on Shiraz cultivar. Rhizophagus irregularis fungi also induced higher root colonization for Bahar cultivar (35.48% increase) compared to Shiraz cultivar. In general, Bahar cultivar was superior to Shiraz cultivar both in term of shoot yield and response to vermicompost and fungi application.

Nutrient status in some soils shows that in some high-nutrient soils, nutrient availability is not enough for optimum growth and development of plants because of high soil pH. For that reason, in arid and semi-arid regions, organic matter and acid compounds is added to reduce the soil pH. Elemental sulfur (S) is the most important compound used to acidify soil. In the suitable conditions of humidity, temperature, ventilation, elemental sulfur is being converted to sulfuric acid by microorganisms. This study was carried out to investigate the effects of sulfur on nutrient availability by wheat in a randomized completely block design with five levels of sulfur (no, 500, 750, 1500 and 3000 Kgha-1 (as elemental sulfur)) in three replications for two years under farm conditions. First and second year results showed that the different treatment had significant effects (p

Phosphorus availability in soils is largely depended on acidic and alkaline phosphatase activities. Soil organic matter content is one of the most important factors influencing the activity of those f enzymes. The present experiment was carried out in a randomized complete block design with three replications on corn planting time in four provinces of Khuzestan, Khorasan, Fars and Mazandaran. Treatments included chemical phosphorus fertilizer (P 100%), caw manure (P0 M2) 20 tons per hectare, organic fertilizer (P0 M4) 20 tons per hectare, the first treatment plus second treatment (P100% M2), the first treatment plus third treatment (P100% M4) and without any chemical phosphorus fertilizer and manure (P0 M0) as control. In all provinces cow manure was used but organic fertilizers were different in each province. In Mazandaran, compost of wood and paper industries; In Khorasan, compost of municipal waste; In Khuzestan, sugar cane bagasse compost and in Fars, municipal homemade was used as organic fertilizer. From each province 36 samples (before and after planting) were collected and a total of 144 samples were analyzed. The results of different treatments showed the positive effect of the simultaneous use of vegetation and organic fertilizers on acidic and alkaline phosphatase in soil samples. In all Provinces, the mean activity of alkaline phosphatase before and after corn planting period, was higher than acidic phosphatase.

This study was conducted in order to investigate the changes of nutrient status during vermicomposting process from various organic residues. Organic materials included cow manure wheat bran (CB), cow manure wheat straw (CS), cow manure sycamore and maple litter (CL), cow manure apple and grape pruning waste (CP), cow manure lemon balm extract wastes (CE) along with cow manure as control (C). These organic residues were treated in the presence of Eisenia fetida. Some properties of vermicompost and changes in nutrient contents were evaluated at 0, 60, 120 and 180 days. The results showed that EC and pH significantly increased over time in all examined organic wastes and ranged from 1.9 to 3.8 dSm-1 for EC and from 6.5 to 7.4 for pH. Cation exchange capacity (CEC) also increased noticeably, so that the highest CEC amount was observed at 180 days in CS treatment by 364 cmol()kg-1. Furthermore, P and K contents in decomposed organic wastes increased significantly and the highest amounts were obtained in CP and CS treatments by 1.01 and 2.31 %, respectively. The same uptrend happened for N content in CP, CE and CL treatments by 2.51, 1.97 and 1.91 fold compared to initial amounts. On the other hand, Organic carbon significantly decreased during decomposition and the highest decrement in organic carbon content was observed in CE and C treatments by 0.54 and 0.53 fold compared to initial values. C/N ratio in all examined treatments significantly decreased where the highest C/N ratio and the lowest decrease obtained in CP and C treatments by 0.22 and 0.47 fold compared to initial values. NO3- and NH4 significantly increased during vermicomposting process as nitrate content was more than ammonium content in all treatments. Increasing the nutrients amount due to organic matter mineralization, is the effective factor in maturity level of vermicompost.