Iranian Journal of Soil Research
Year:2007 | Volume:21 | Issue:2|Papers Count:17

In order to investigate the effect of plant density and nitrogen levels on leaf appearance rete of com, a split plot experiment based on randomized complete block design with three replications was conducted in Ardabil Agriculture Research Station in 2005. Factors were: nitrogen levels in main plots (0, 75 and 150 kg N ha-1) and plant densities in sub plots (7, 9 and 11 plants m-2) The results showed that the effect of plant density, nitrogen levels and the interaction of the studied factors were significant on phyllochron and leaf appearance rate. With increased nitrogen levels, the phyllochron was decreased but rate of leaf appearance was increased, the revers with increasing plant density, the phyllochron was increased but rate of leaf appearance was decreased. Maximum leaf appearance rate and minimun of phyllocron was obtained at density of 7 plants m-2 with 150 Kg N ha-1. The highest vegetative growth period and yield of com was obtained with increasing plant density and it was found maximum in density of 11 plants m-2 and 150 Kg N ha-1.Flowering coincidence period duration was decreased with increase in plant density but it wasn't effected by nitrogen levels. Flowering coincidence period was effected by plant density x nitrogen levels Interaction. Mean comparison showed that maximum flowering coincidence period was obtained in density of 7 plants m-2 with application 75 Kg N ha-1. Therefore, with increasing plant density and leves nitrogen, increased com yield, so it was suggested that in order to increasing leaf appearance rate and grain yield was respectively applied 7 and 11 plant density with 150 kg N ha-1.

The principle objective of this review article is to present to plant nutrition specialists some interesting aspects of the role of organic acids in improving the availability of nutrient elements in calcareous soils in order to promote more research in this area. The rhizosphere is the zone of soil immediately surrounding plant roots that is modified by root activity. In this critical zone, plants respond to their environment. As a consequence of normal growth and development, a large range of organic and inorganic substances are exchanged between the root and soil, which inevitably leads to changes in the biochemical and physical properties of the rhizosphere. Plants also modify their rhizosphere in response to certain environmental signals and stresses. Organic anions are commonly detected in this region, and their exudation form plant roots have now been associated with nutrient deficiencies and inorganic ion stresses. Organic acids such as citrate, oxalate and malate are active in many of the roots natural processes including nutrient absorption, reducing metal toxicity, mineral weathering and pathogens attraction. A full assessment of their role in these processes, however, cannot be determined unless the exact mechanisms of plant organic acid release and fate of these compounds in the soil are more fully understood. This review therefore, includes information on organic acid levels in plants, soil reactions (soil solution concentration, sorption) and microbial considerations (mineralization). In summary, the release of organic acids from roots can operate by multiple mechanisms in response to a number of well-defined environmental stresses (e.g., P and Fe stress). These responses, however, are high stress and plant-species specific. In addition, this review indicates that the sorption of organic acids to the mineral phase and mineralization by the soils microbial biomass are critical to determining the effectiveness of organic acids in most rhizophere processes.

The following experiments were conducted on two phases, on 2001-2003 arranged in randomized complete block design in order to study sulfur and Thiobacillus thioxidans L. on phosphorus availability of phosphate rock. The 1th phase of these experiments was performed on farm to study the main effects of treatments on com crop, and 2th phase was carried out on farm to study the residual effects of treatments on barley crop. Following parameters were determined after crop harvesting in each phase: crop yield (dry matter yield of com, straw yield, grain yield, harvesting index, and thousands grain weight of barley), dry matter percentage (DMP), crop growth rate (CGR), P and Zn content in leaf, relative agronomic efficiency (RAE), total phosphorus yield (TPY) and soil available phosphorus (Pava) measured for com crop. The following results have been obtained: Main effects of treatments on dry matter percentage (DMP) and relative agronomic efficiency (RAE), were statistically significant at 1% level and main effects of treatments on dry matter yield (DMY) and crop growth rate (CGR) were significant at 5% level, but the main effects of treatments on P and Zn content in leaf, total phosphorus yield (TPY) and P (ava.) were not significant. Residual effects of treatments on straw yield were statistically significant at 5% level but the residual effects of treatments on grain yield and thousands grain weight, harvesting index and relative agronomic efficiency were not statistically significant. The results of this research showed that phosphate rock with sulfur and Thiobacillus spp, increased and yield indices of com and barley crops, but for main and residual effects, treatments with sulfur and Thiobacillus spp had more effects than treatments with sulfur alone. Therefore, we can recommend treatments with sulfur and Thiobacillus spp for increasing main and residual effects on corn and barley crops.

The (Atterberg) consistency limits of soil are important for soil mechanical properties the are used primarily in classifying cohesive soil materials for engineering purposes and are strongly correlated to other fundamental soil properties. They are also used for estimation of there useful indices for soil engineering interpretations, such as shear strength and bearing capacity, compressibility, swelling potential and specific surface. Whereas the direct measurement of there are time- consuming and require enough experiment, it is required that predict them indirectly by using some soil easily available properties with reasonable accuracy. The objective of this study was to predict soil liquid limit (LL), plastic limit (PL) and plasticity index (PI) indirectly from some easily available soil physical and chemical properties. In this research 37 loamy soil samples were randomly collected from karaj area 30 samples were used for model development and 7 samples were used for validation. Particle size distribution, bulk density, and cation exchange capacity were determined by the hydrometry, cold, and with ammonium acetate methods, respectively. Liquid limit were obtained using casagrande. The optimum combination of independent variables for estimation of LL, PL and PI were selected by using stepwise regression method. The regression equations were obtained using multiple linear regression method. The results indicated that there was a significant correlation between measured and predicted values. The correlation were significant at 0.1% for presented functions of liquid limit (R2adj=0.77), plastic limit (R2adj=0.72) and plasticity index (R2adj= 0.62). Statistical analysis for the evaluation of PTFs indicated that Geometric mean error ratio (GMER) values were close to 1 (0.99-1.06) and Geometric standard deviation of the error ratio (GSDER) values were small (1.03 - 1.32). The results indicated that presented functions were valid.

Saline soil and saline irrigation water presents potential hazards to Canola production. Germination is one of the most critical periods for a crop subjected to salinity, because plant establishment and survival are dependent on these phonologic stages. To investigate the effect of salinity on germination and seedling of Canola (Brassica napus L.) in a natural saline soil and to compare the germination process in natural and artificially made saline water (NaCl + CaCl2 solution), an experiment with three phases was conducted in completely randomized design with 12 saline treatment and 3 replicates in agricultural faculty of Tarbiat Modares University. Germination in the first two phases was in Petri dishes in an incubator and included a nonsaline water treatment (Tap water) and 12 saline water treatment of 3 to 25 dS/m from two sources; natural saline water and NaCl + CaCl2 solution as a charge base. Germination in phase 3 was carried out in a greenhouse inputs containing natural saline soil, which was equilibrated with saline water having the same salinities. The germinated seeds were counted at the desired time intervals and continued until 3 continuous counting were identical. The percent of germinated seeds and germination rate were calculated and analyzed. The result indicated that germinated seeds and germination rate are decreased with salinity increasing. But this decrease in natural saline water was more than the NaCl + CaCl2 solution. Comparison of seed germination in soil and in incubator showed that the seed could germinate in all salinity treatment in incubator (in spite the decrease in germinated seeds and germination rate), but seed germination in soil was continued up to 11 dS/m. with time, seedling growth decreased with increasing salinity and sometimes was fully stopped. The seed could not germinate and grow in soil salinity more than 7 dS/m. also germination was observed in all saline treatments in the incubator, but seems it can tolerant salinity in germination stage up to 5 dS/m.

Under conditions of water scarcity, using treated municipal wastewater for irrigation of agricultural crops is necessary. At the present time, several wastewater plants are being built in different cities of Iran. In this research, to assess the effects of wastewater usage on wheat, an experiment was performed near Shahinshahr Wastewater Treatment Plant and Rowshan wheat variety was grown during 2000-2002. For this purpose, four irrigation treatments were applied in a complete random block design, as: Irrigation with well water based on ET-HS model (T1), irrigation with treated wastewater based on ET-HS model (T2), irrigation with treated wastewater based on 10% more than ET-HS model (T3), irrigation with treated wastewater based on 20% more than ET-HS model (T4). The results showed that the treated-wastewater quality parameters such as salinity and SAR were better than well water. Irrigation with treated wastewater, as compared to well water, resulted in higher yields. No significant difference (p<0.05) was observed between T2, T3 and T4, but T2 had the highest water use efficiency. Application of wastewater didn't cause any increase in concentration of specific ions and heavy metals over the standard levels in different parts of wheat.

Soil contamination of heavy metal, is one of the main problem in the world today. Recently, hyperaccumulation plants are mostly used to clean the polluted soil. A field study in 3 sites with 3 concentrations of zinc (high, medium and low) was carried out in Bama mine, Irankoh region. Having analyzed the soil physical and chemical properties, 11 ranged-land plant species were selected among 7 families. The experiment was done in completely randomized design with 3 replicates. Soil rhizosphers, however, were analyzed in order to determine the zinc absorption forms by plants. Bioaccumulation, tolerance index and translocation factor of zinc were studied. According to the results Ebenus estellata and Astragalus glucanthus were the most appropriate selected plants with 293.3 and 195.1 mg/kg bioaccumulation in shoot and 5.72 and 6.46 translocation factor respectively.

In a considerable proportion of the worlds' arid and semiarid regions, as with the conditions that prevail in our country, wheat is produced under rainfed cultivation. In such area the plant depends on the natural precipitations as the source of its moisture supply and may suffer water stress and drought at any time. During drought periods, it is mostly the interuption in the absorption of nutrient particularly the less mobile elements such as phosphours, iron, zinc and copper that decrease the wheat yields. Arbuscular mycorrhizal fungi (AMF) are the obligate symbiotic organisms that exist in the root systems of more than 80 percent of plant families. These fungi are of great values to the initial establishment and improve plant growth by providing water and nutrients especially under the conditions in which the hosts are stressed by environmental limitations. A greenhouse experiment was conducted in a factorial test arranged as a complete randomized design with four fungal treatments namely, Glomus mosseae from Canada, G mosseae and G. etunicatum obtained from Tabriz University and the non-fungal treatment (control). Three soil moisture levels of 22, 14 and 8% (w.v) with two soil types (sterilized and non-sterilized) and six replicates were used in the experiment to asses the mycorrhiza interactive effects on wheat nutrient uptake under drought conditions. The results indicated that the rate of nutrient uptake was significantly increased by increasing soil moisture contents (P<0.01). The fungal treatments on the sterilized soil resulted in a significant increase in the rate of phosphorus and zinc uptake (P<0.01) and increase of dry matter, yield and uptake of copper (P<0.05). Dry matter, yield and absorption of phosphorus and zinc also was increased in the non-sterilized soil (P<0.05), but the increase in the rate of copper absorption was not statistically significant. Similarly, the rates of nitrogen, potassium, iron and manganese uptake did not significantly increase in either the sterilized or non-sterilized soils.

The performed researches during last decade have proved new perspective of rhizobacterial application. These researches show that rhizobia can cause growth and plant yield increase in different ways in spite of their main role in N2 fixation. So rhizobacteria are considered as plant growth-promoting rhizobacteria (PGPR) now. These bacteria can make nutrition improvement or plants health level increase in direct (plant growth hormones production, organic and inorganic insoluble phosphate solubilizing, ...) and indirect (siderophore, HCN,...production) way, altogether they can cause products yield increase. One of the PGPR factors is HCN production ability to Proteobacteria and in many cases in Psudomonas. Certain rhizobia strains are recently introduced as Hydrogen Cyainde production bacteria too, several researching tasks have been performed on indigenous rhizobia but cyanogens ability has studied in none of them, so this research with the aim of HCN production effects on growth charactacterisitcs of some plants was planned and carried out for the first time in two laboratory and green-house stages as follow: At first, biochemical and microscpis tests were performed on 454 selected rhizobial isolates among different rhizobial genus. Suspension with the same population of 5*108 cfu.ml-1 were prepared from all pure and fresh rhizobial culture. HCN production ability determination was performed by Lock (1948), which was corrected by alstrom (1987), so rhizobial strains were grouped in cyanogenecy different levels from 1 to 4, as the least, almost low, almost high, the most in HCN production. Cyanogens super strains inoculants application effect and alfafa, wheat and corn yields in green house test were evaluated too. The results first prove rhizobacteria as cyanogens.33 isolates (7.26%) from 454 rhizobial isolates had the ability of HCN production. Secondly, this ability is not the same in different strains. Abundance of the strains among different HCN production potential levels (1-4) were 10, 6, 11 and 6 (2.2, 1.32, 2.42 and 1.32% the most abundance among cyanogens rhizobia belonges to both Rlv and S.m group (almost 80%) in return any of slow growing (Brady) rhizobia (Clycin Max and Peanut) was not able to produce HCN. The results of different plant growth promoting rhizobacteria inoculants application on legumes (alfalfa) and nonlegume plant (wheat and corn) also proves that inoculation of these plants with HCN productive rhizobial strain didn't cause significant difference in any of measured items such as biological yield and plant yield in comparison with control treatment without fertilizer (Negative Control).

One of the most important symbioses in plants is Vesicular Arbuscular Mycorrhiza (VAM) fungus that has widespread distribution. Many plants that have special properties such as root morphologic properties have different symbiosis with VAM fungi. This symbiosis has different effects on each plant. The role of these fungi in absorption of non-mobile elements such as phosphate is more important. In a glasshouse experiment on two cultivar of clover, Trifolium alexanderinum and Trifolium subterraneum, the effects of soil applications of phosphorus fertilizer and inoculum of Glomus interraradice on the mycorrhizal colonization of roots, mycorrhizal dependency, crop yield and nutrient uptake were studied in autoclaved sterilized soil. Root length in the two cultivars was different. The applied P increased plants dry matter significantly but suppressed mycorrhizal infection. Mycorrhizal dependency and percentage of root colonization in T.alexanderium were more than those of T.subterraneum. There was a negative correlation between mycorrhizal dependency and percentage root colonization on one hand and applied phosphorus on the other. The highest root colonization occurred in zero level of phosphorus and the lowest in 25 mgkg-1 phosphorus amounting to 55% and 8% respectively. With root colonization and increasing phosphorus concentration, shoot and root dry weight were increased. However at higher phosphorus concentration (25 mgkg-1), the increase was not significant. In control (without mycorrhiza and 0 mgPkg-1 soil), dry root weight in T.subterraneum was more than T.alexanderinum. The correlation between mycorrhizal colonization and phosphorus concentration on one hand and K content in plant tissues was negative.

In this research, twenty-five isolates of fluorescent pseudomonads were isolated from forty soil samples of wheat rhizosphere and their ability for promoting plant growth were determined. Results of the study revealed that all the isolates were able to produce auxin (ranging from 1.3-4.5 mg/ml) with an average of 2.44. The range of inorganic P solubilization was 129.9-386.1 mg/ml and the average was 287.5. Nine isolates were capable of utilizing ACC as carbon and or nitrogen sources, whereas all of them produced siderophore on both CAS agar and CASAD plates. The range of siderophore production was 0.072-0.459 mM of deferoxamine mesylate salt with an average of 0.21 none of the isolates were capable of chitinase production. Salicylic acid production by the isolates ranged from 0-10.91 mg/ml (average of 2.48). Bacterial ability for production of hydrogen cyanide had a great variation and based on this ability they were qualitatively classified in to very high, high, intermediate and low. Results of this study showed that fluorescent pseudomonads are native to soils of Iran have the potential to be used as plant growth promoters. There is also a need to study their effects on different agricultural crops.

Saliferous and gypsiferous aridisols constitute a major part of soils in arid and semi-arid regions of Iran. However limited information regarding their formations and crystalline forms is available. To investigate the formation of saliferous and gypsiferous soils of Eshtehard region in Karaj and to classify them, physicochemical, micromorphological, and SEM studies were carried out. An assessment of the soil physical and chemical properties, including soil texture, electrical conductivity (saturated extract), soil reaction, organic carbon percentage, equivalent calcium carbonate, gypsum content (percentage), soluble cations and anions was made on samples taken from pedological structure (pedons). Standard procedures were employed all throughout the study. In a study of thin sections, pedogenic gypsum was observed as oriented crystals, infilling voids. It was lenticular shape when within soil matrix. SEM analysis revealated the presence of gypsum lenticular crystals accompanied by halite crystals of cubic forms. These were verified through EDS curves. Based upon physico-chemical, micromorphological and SEM studies, it is finally concluded that soils of lowland type have been formed as per ascendum mode, while those of gravelly colluvial forms have been formed as per descendum mode.

Owing to many drawbacks associated with traditional methodss for identifying sediment sources, fingerprinting techniques, based on physical, chemical and organic properties of sediment and source materials, are increasingly being used as an effective alternative approach to assembling such information. In this method, a suitable composite (set) of diagnostic properties and a multivariate mixing model were employed to estimate the relative contribution of sediment sources to sediments transported to basin outlet. In this study, using suitable composites of geochemical elements, radionuclides, organic Carbon, Nitrogen and Phosphorous, capable of discriminating differerent land uses of the study basin, and a multivariate mixing model was used to determine the contributions of these land uses to sediment yield. The suitable composite fingerprints (elements) were obtained using discriminant analysis. The study basin is the main subbasin of Pouldasht water spreading station basin, Margan, located in Makoo township, Western Azarbaijan province, Iran. The suitable composite fingerprints having capability to distinguish land uses consisted of 137Cs, OC, Pb, Be, Sn, P, Ti and Cu. Mean contributions from the three main land uses were in the order: rangelands with gully, channel and river bank erosions (65.85%), rangelands with sheet and rill erosions (13.81%), agricultural lands (20.34%). Low mean absolute errors (less than 22%) show high degree of correspondence between measured and predicted properties. High model efficiencies (greater than 0.999) confirm the goodness of fit of the mixing models. Also it is argued that fingerprinting estimates for sediment sources are consistent with field observations.

Knowledge of the soil infiltration parameters and infiltration variation is necessary for efficient furrow irrigation. This experiment was conducted in the experimental farm of Tehran University at Karaj in 2002. The method used for determination of the basic infiltration rate was Inflow-Outflow. The basic infiltration rate and cumulative infiltration were determined on twelve irrigation events. The beds were planted with maize and divided into 3 plots each consisting of the three neighboring furrows. The outer furrows in each plot were used as guard rows and all measurements were taken on the center furrow. Results showed that the basic infiltration rate decreased during the season. At the end of season, the soil basic infiltration rate decreased about 34% as compared to the beginning. Also application efficiency decreased during the period. At the end of season, the application efficiency (AE) decreased about 10% as compared to the beginning of period. For achieving proper management with considering seasonal decrease of infiltration, time of irrigation must be increased.