مجله زیست شناسی خاک
سال نهم شماره 1 (بهار و تابستان 1400)

Plant growth promoting rhizobacteria with ACC deaminase activity can be applied for stimulating plant growth under tension situations. In the present study, bacterial isolates were isolated from wheat rhizosphere in three provinces of Zanjan, Kurdistan and Hamedan and then screened for ACC deaminase production and salinity tolerance. Six isolates out of 167 isolates were able to degrade ACC to alpha-keto-butyrate and ammonia and the K78 isolate was selected as superior isolate. A completely randomized design with factorial arrangement was carried out on wheat plant in a greenhouse experiment. Experimental factors include: five salinity levels (1.3, 8, 12, 14, and 16 dS.m-1), three bacterial inoculation levels (no inoculation (B0), inoculation with salinity-resistant isolate and ACC deaminase production capacity (B1), inoculation with salinity-resistant isolate without ACC deaminase production capacity (B2). The results showed that salinity had a significant and negative effects on growth and nutrient uptake and decreased shoot length. The K78 isolate increased shoot length (21.5 %) and potassium uptake (15 %) significantly compare to B0 treatment but had no significant effect on sodium uptake. Overall, it can be concluded that inoculation of K78 isolate can reduce the negative effects of salinity on growth indices and the nutritional conditions of wheat.

Vegetation type changes some soil properties such as bulk density, nutrient absorption and soil organic carbon. Nutrition management of lawn plant is an important factor which affects soil properties in lower layers. The application of biofertilizers enhance the quality of soil and enhance the growth of lawn plant and in addition they are ecofriendly. The purpose of this study was to investigate the effect of urea and biofertilizer containing nitrogen-fixing bacteria (Pantoea agglomerans) on some quality characteristics of soil under lawn plant cultivation. This experiment was conducted in a completely randomized design in a greenhouse condition with three replications. Treatments include: 1-Control (Br), 2- lawn plant cultivation (Speedy Green) by conventional method (Gr), 3- lawn plant + urea (GrU), 4- lawn plant + bio-fertilizer containing Pantoea agglomerans (GrPA), and 5- lawn plant + Pantoea agglomerans + growth promoting bacteria (GrPP). The fresh weight of lawn plant was measured along with some soil properties. The results showed that lawn plant and application of biofertilizer containing Pantoea agglomerans shaped larger soil aggregates than control but they had no significant effect on aggregate stability. Biofertilizers and urea increased the growth of lawn plant. Cultivation of lawn plant increased soil organic carbon, total nitrogen, phosphorus and potassium uptake, but the effect of biofertilizers was not significant. The highest amount of total nitrogen and soil organic carbon observed in urea fertilizer treatment. In general, the use of biofertilizers in lawn plant cultivation is recommended.

In order to investigate the diversity and population fluctuations of soil mesofauna (Acari and Collembola) of conifers (cypress and pine trees) at Ilam province, Iran, soil samples monthly (0–5 and 5–10 cm) were collected during September 2018 to September 2019. The soil mesofauna were extracted using a Berlese funnel and they were counted and identified. The number of arthropods was compared in different soil layers and in different seasons of the year. The analysis of variance of data showed that soil layers and seasons had significant effect on the population densities of soil mesofauna in both cypress and pine trees (P≤0.01), but their interaction did not vary significantly. Based on the means comparisons, the highest and the lowest values of population density of soil mesofauna were ​​belonged to cypress trees with values of 26.5±8.22 (at autumn) and 0.74±0.15 (at summer). In addition, based on the mean comparison, the highest and the lowest amount of population density of soil mesofauna in pine trees were 4.31±1.26 (at autumn) and 0.63±0.14 (at spring). Diversity of arthropods was calculated by using biodiversity indices. The results showed that the most diversity of species based on Shannon-Wiener and Simpson indices observed in seasons and sampling area (cypress and pine trees) with values of 3.77 and 0.97 for pine and summer time and the least diversity detected with 2.44 and 0.83 for cypress and spring time, respectively. Also, the highest amount of species richness of Margalef (11.68) related to the soil of pine trees in autumn season and lowest amount (7.89) related to the soil of cypress trees in spring season. The highest values ​​of Pielou evenness index (0.97) related to soil of pine trees in summer time and lowest value (0.64) related to the soil of cypress trees in spring time. Generally, the calculated biodiversity indices in the soil of pine trees were higher than in the soil of cypress trees, which could be more widely used in the forestry system