مجله زیست شناسی خاک
سال سوم شماره 1 (تابستان 1394)

Rough Lemon rootstocks have a great yield، early production، fast growth and proper for sandy soils. A greenhouse experiment was conducted as a completely randomized design (CRD) with a factorial arrangement and three replications. The experimental factors were mycorrhizal treatments at two levels (inoculation with Claroideoglomus etunicatum and control) and salinity treatments at four levels (2، 4، 6، and 8 dS m-1 NaCl). The results showed that salt stresses decreased root colonization، shoot and root dry weights، leaf number، leaf area، plant height، stem diameter، chlorophyll index، shoot phosphorus and potassium uptake but they increased leaf temperature، electrolyte leakage and shoot sodium uptake. Under both non-stress and salt stress conditions، arbuscular mycorrhizal fungus increased root colonization، shoot and root dry weights، leaf number، leaf area، plant height، stem diameter، chlorophyll index، shoot potassium (except salinity level of 6 dS m-1) and phosphorus uptake، but leaf temperature and electrolyte leakage decreased in comparison with non mycorrhizal treatments. No significant difference observed for shoot sodium uptake.

The purpose of this study was to investigate the effects of Tribenuron-methyl (Granstar) and Bromoxynil (Pardnr) herbicides on dehydrogenase and urease activity and biological properties of a calcareous soil under wheat cultivation. An experiment was conducted in a completely randomized design (CRD) with factorial arrangement (18 treatments) and 3 replications in pots. Tribenuron-methyl concentrations of 30، 42، 56 (concentration recommended) and 84 milligrams per liter and Bromoxynil concentrations of 225، 450، 675 (concentration recommended) and 900 milligrams per liter were applied into the soil samples in the presence and absence of wheat plants. The activities of soil dehydrogenase and urease were measured at 3، 30 and 60 days after herbicide application. The results showed that dehydrogenase and urease activities were reduced with increasing herbicides concentrations in each of the sampling time compared to the control treatment. The most reduction of dehydrogenase and urease activities (61% and 51% respectively) was observed at concentration of 900 milligrams per liter treatment after 3 and 30 days of application. Dehydrogenase activity was increased after three days and it might be due to an increase in microbial populations with the capability of utilizing the herbicides as a carbon source. Also، a significantly decrease observed in enzymatic activities in treatments without plants compared to the plant treatments.

Plant growth promoting rhizobacteria (PGPR) have a positive effect on crop yield through increasing the availability of phosphorous and other nutrients. The aim of this study was to investigate the effect of simultaneous application of Pseudomonas fluorescens and phosphate fertilizers on yield and nutrient uptake of canola grain. Experiment was carried out in a greenhouseconditions in acompletely randomized design. The treatments were as control، PGPR، single super phosphate (SSP)، triple super phosphate (TSP)، ammonium phosphate (AP)، rock phosphate (RP)، single super phosphate+PGPR، triple super phosphate+PGPR، ammonium phosphate+PGPR and rock phosphate+PGPR. The results demonstrated that grain and shoot yield of canola inoculated with PGPR increased by 29. 80 and 30. 56 percent compared to control treatment، respectively. Simultaneousapplication ofPGPR and phosphate fertilizers was the most effective treatment on grain and shoot yield. The highest amount of grain and shoot yields were obtained from triple super phosphate+PGPR treatment، which were 10. 22 and 29. 99 g. pot-1، respectively. There was a significant difference among other treatments. When canola plant inoculated with PGPR Fe، Zn، Mn and Cu uptake increased in canola grain compared to non-inoculated treatments. The highest uptake of Fe، Zn، Mn and Cu were 63. 97، 0. 76، 0. 43 and 0. 03 mg pot-1، respectively. There was no significant difference between triple super phosphate+PGPR and ammonium phosphate+PGPR treatments in uptake of Fe، Zn، Mn and Cu. Overall، the combined use of PGPR and P-fertilizers had a positive and significant effect on yield and nutrients uptake of canola. According to the results، the use of PGPR can increase the availability and efficiency of P-fertilizers.

Study of soil enzymatic activities and biological properties gives us potentials of soil in supporting biochemical processes and maintaining soil fertility. Current study was conducted to investigate the effect of soil type and depth on some of soil biological properties and on soil enzymatic activity including the Urease، Invertase، Akaline phosphatase and Aryl sulphatase enzymes in two types of Histosols. In each region، sampling was carried out from 3 soil profiles (0-120 cm، at each 20 cm interval). Results showed that the influences of soil type، depth and their interaction on the activities of the studied enzymes were statistically significant (p < 1%). The activity of these enzymes was affected strongly under environmental conditions. Soil depth had a significant effect on soil enzymatic activity. In lower horizons، enzymatic activities were truncated compare to upper horizons of the studied soils. Investigating the relation between enzyme activities with soil organic carbon and microbial biomass carbon designated the positive role of organic carbon (r = 0. 86**) and microbial biomass carbon (r = 0. 87**) in two soil types. The results of soil respiration showed that microbial respiration increased over time and it seems that soil biological activity increased during the experimental time.

An experiment was conducted to evaluate the effect of arbuscular mycorrhizal fungi (AMF) and vermicompost on biological yield، stem height، spike length، and concentration and uptake of zinc (Zn)، iron (Fe)، manganese (Mn) and copper (Cu) in straw of two wheat cultivars as a factorial experiment arranged in a completely randomized design (CRD) with three replications under greenhouse conditions. Treatments included two levels of AMF (with and without AMF)، two levels of vermicompost (0 and 1%، w/w)، and two wheat cultivars (Shiraz and Bahar). Results showed that maximum biological yield، stem height and spike length obtained by application of vermicompost (without AMF) in Bahar cultivar. Biological yield، spike length، Zn and Mn concentrations، and total uptake of Zn، Fe، Mn and Cu significantly affected by vermicompost application. Maximum concentration and uptake of Zn observed in AMF treatments (without vermicompost) in Bahar cultivar. Mn uptake was increased when vermicompost and AMF were applied to soil samples but it was decreased when AMF was not applied. Biological yield، stem height، concentration and uptake of Zn and Mn were higher in Bahar cultivar compared to Shiraz cultivar. It might be concluded that biological fertilizers increased the wheat yield which is a strategic product. Yield and micronutrients uptake in Bahar cultivar were higher than Shiraz ones.

Plant growth promoting rhizobacteria (PGPR) encourage the plant growth by different mechanisms including synthesizing growth promoting hormones، phosphates solubilization، sydrophore production and nitrogen fixation. In this study، the effects of single and coinoculation of Flavobacterium، Herbaspirillum، Pseudomonas and Azotobacteron growth indices of tomato were evaluated with and without chemical fertilizer. The experiment was conducted as completely randomized design (CRD) with four replications under greenhouse conditions. The results showed that there is a significant differences between the fertilized and unfertilized soil samples. The highest mean of shoot and root dry weight observed when soil samples inoculated with Flavobacterium but the highest mean of the two above mentioned indices detected when unfertilized soil samples coinoculated with mixed strains. The highest mean of plant height، number of flowering and leaf chlorophyll content was obtained in the unfertilized soil samples that were inoculated with the mixed strains. The highest number of flowering and leaf chlorophyll content were also obtained by inoculation of fertilized soil samples with foreign Pseudomonas strain. It was concluded that inoculation of PGPR had a profound effect on the growth of tomato plant grown in unfertilized soil samples، but not in fertilized soil samples

Most of the agricultural lands of Iran are calcareous soils and sulfur deficiency in soils is a very common occurrence in Iran. Poor availability of micronutrients is one of the major factor of plant nutrient deficiency in calcareous soils. In this Study the effects of sulfur، Thiobacillusand organic matter application on some micronutrients availability such a Zn، Fe and Mn in the soil samples and canola seeds investigated in a calcareous soil. An experiment was conducted in a completely randomized design (CRD) with factorial arrangement (18 treatments) and 3 replications under greenhouse condition. Experimental factors include three levels of sulfur (0، 400 and 800 kg/ha)، three levels of Thiobacillus (0، 2 and 4 kg/ha) and two level of organic matter (0 and 20 tons/ha). The results showed that sulfur، Thiobacillus،organic matter and their interactions had a significant effect (p<0. 01) on all evaluated indices. The highest concentration of Mn، Zn and Fe were 23. 50، 3. 73 and 3. 13 mg/kg soil respectively in the treatment which had been received organic matter + 800 kg sulfur + 4 kg Thiobacillus. The maximum uptake Mn، Zn and Fe were 48. 93، 41. 40 and 97. 93mg/kg in canola seeds in the same treatment.

Rhizobium leguminosarum bv. viciae has a symbiotic relationship with faba bean and have ability to fix nitrogen biologically. A field experiment was conducted to evaluate the effectiveness of seven different strains of Rhizobium leguminosarum bv. Viciae on growth and yield of faba bean. The inoculums were prepared as powdery forms and they were used for seed inoculation. The field experiment was carried out on the basis of randomized complete block design (RCD) in four replications as following: 7 inoculants (different strains of R. leguminosarum bv. Viciae)، 100 and 200 kg. h-1 of nitrogen and control. The field experiments were conducted for two years in research center of Khuzestan، Lorestan، Mazandaran and Golestan provinces. In addition، the selected strains were evaluated in farmers’ fields in third years. The results showed that the faba bean yield increased maximum by 69 and average by 20 percent over control due to the inoculation. Application of inoculums in the farmers’ fields increased seed yield and nitrogen uptake of shoot by 30% and 65% respectively. Finally، two isolates were recommended as Rhizobium inoculum for fields under cultivation of faba bean in Iran.