Iranian Journal of Soil and Water Research
Year:2012 | Volume:43 | Issue:1|Papers Count:10

Drought tolerances of 55 indigenous strains of Pseudomonas fluorescens were evaluated. To assess the tolerance rate of the strains to various levels of water deficit, their growth rate in NB medium containing concentrations of 40.587, 438.838 and 548.838 g of polyethylene glycol 6000 per liter of medium were utilized. Water potentials of aforesaid levels were estimated as 0, - 10, - 20 and -30 bar, respectively. A Number of 39 strains could grow under water stress conditions for which the production of ACC-deaminase enzyme as well as Indole-3- Acetic Acid (IAA) hormone was studied. Among them, some Pseudomonas fluorescens strains were selected as superior ones for greenhouse experiments. The experiments were performed through factorial arrangement in a Randomized Complete Block Design of three replications. The results revealed that 25.64 vs. 23.07 percent of the tolerant strains were able to produce high levels of ACC- deaminase enzyme vs. Indole-3- Acetic Acid (IAA) hormone, respectively. The greenhouse results indicated that inoculation of plants with superior strains (IAA&ACC-deaminase) significantly increased growth indices as well as yield as compared with control under any of the water stress or normal conditions.

Continuous soil quality evaluation in is necessary agricultural regions to sustainable soil management and profitable agricultural production. The objectives of this study were comprised of an evaluation of soil quality utilizing Integrated Quality Index (IQI) along with its spatial distribution in Qazvin province. IQI was calculated and its spatial changes analyzed using different interpolation methods via GIS software. Precision criteria MAE and RMSE, bias criteria MBE and correlation between measured vs. predicted values (r) were employed to determine a suitable interpolation method. The results indicated an IQI index of strong spatial correlation (Nugget/Sill=0.38) with an effective range of 19.18 kilometers. The IQI spatial distribution is well fitted by the exponential model. Completely Regularized Spline was selected as a suitable interpolation method using evaluation criteria as well as existing trend in area. IQI model revealed the soil areas with moderate quality (grade III) as dominant.

The effects of waterlogging, sewage sludge and animal manure on the concentrations of DTPA extractable copper, iron, manganese and zinc were investigated in two different types of soil. A factorial experiment based upon a completely randomized design of two replications containing duration of waterlogging at six levels (0, 1, 3, 7, 15, 30 days), source of organic fertilizer at three levels (control, animal manure, sewage sludge) and soil type at two levels (one alkaline loamy sand soil and one acidic clay soil) was carried out under laboratory conditions. Equal quantities of animal manure and sewage sludge, at a rate of 30 grams per kilogram of soil, were added. During waterlogging period, the water level was maintained 3 cm above the soil surface. The results showed that by increase in the duration of soil waterlogging, the DTPA extractable Fe and Mn in both soils and for all treatments increased significantly with the degree of increase in acidic clay soil being more than that in alkaline loamy sand soil. Following waterlogging, manganese reduction rate was more than iron in acid clay soil for all treatments except control. By increasing the duration of soil waterlogging, the DTPA extractable Cu and Zn for both soils and in all treatments decreased significantly with the level of decrease in acidic clay soil being higher than that in the alkaline loamy sand soil. By application of sewage sludge and animal manure, the DTPA extractable Cu, Fe, Mn, and Zn in both soils increased significantly with the level of increase being dependent on the duration of soil waterlogging. There existed significant regression equations between the duration of soil waterlogging and concentrations of DTPA extractable Cu, Fe, Mn, and Zn in both soils and for all treatments. Following waterlogging, the pH in an alkaline soil increased for all the treatments. The pH in an alkaline soil increased following the application of animal manure while being decreased following application of sewage sludge.

The present study was conducted with the objective of investigating the feasibility of using drainage water mixed with water to irrigate sugarcane (Saccharum officinarum) in Khuzestan province. The investigation was conducted in Research Center of Sugarcane in farming seasons of years 2008-2009. Four salinity levels of irrigation water were selected (S1, S2, S3 and S4 respectively with salinites of: (river water, 3, 4.5, and 6 dS/m), as major treatments and three varieties (CP48-103, CP57-614 and IRC99-01), as minor treatments in four replications and in the form of a randomized complete plan. Following the initial and developmental stages from March to October 2008, sugarcane was irrigated with the four levels of water salinity. In other words, elementary growth and developmental processes were completed without imposing any water stresses. Salinity treatments of irrigation water were applied starting with March-April 2008. Finally, in January 2009 the crop was harvested with yield), height and juice quality parameters evaluated. Results revealed that with increase in salinity of irrigation water, yield, cane, height, Pol, Brix, purity, yellow sugar and sucrose got decreased. Variety IRC99-01 was found to have maximum crop yield at different salinity levels while varieties CP57-614 and CP48-103 were rated, respectively. For all the varieties, juice quality ratio and electrical conductivity of juice increased with increase in salinity of irrigation water. Levels of calcium, magnesium, sodium, potassium and chlorine were different in sugarcane juice of the three study varieties, a phenomenon related to the physiology of the plant.

An important part of carbon cycling is carried out in the soil making land use changes, including changes in forestlands, affect SOC storage and consequently CO2 flux into the atmosphere.The aims followed in this investigation were to study the impacts of conversion of deciduous forests to coniferous ones and deforested land to rangelands, on some of the soil physicochemical properties, organic carbon (OC) storage, and soil respiration in two sites 1 and 2 (two different sets of properties), in south of Kelardasht area. Soil pH and EC are not substantially affected by land use change, but bulk densities have been on the increase through deforestation and have decreased at reforestation. By reforestation, SOC storage increased about 17.6 and 49.5 % (P<0.05) in sites 1 and 2. However, deforestation has caused SOC storage to diminish about 14.5 (P<0.05) and 4.7% (P>0.05). CO2 emission indicated significant and positive correlation with the mean air temperature in all sources of land use. In General, the coniferous forests proved to be more efficient in organic carbon storage, and therefore could be benefited from in the reduction of soil CO2 emission.

Ponding of unsaturated soils and the final resulted redox conditions, cause different chemical and electrochemical changes. Redox potential is one of the most effective factors in determination of chemical properties of ponded soils; as by influencing dissolution and sedimentation of minerals and the activity and uptake of soil nutrients. The study site with an extension area of area about 10 ha is located in the Rice Research Station (West of Tonekabon County). Considerable Test Results were developed in morphological, physical and chemical characteristics of the studied pedons. For this purpose, Eh, such different forms of iron such as soluble, crystalline, amorphous and total iron along with mineralogy of the redoximorphic features in 7 pedons were studied. The Eh values decrease by increase in soil organic matter under similar anaerobic conditions. Relatively higher organic matter contents (0.35-11.57 %) of the studied soils play an important role in strong complexification of iron and the level of its different forms [Fe-DTPA (8.45-206.64 ppm), Fe-o (0.37-1.3 %), Fe-cd (0.5-5.78 %), Fe-t (3.06-8.19 %)]. Comparison of EDS elemental analyses data revealed that Fe contents were rather higher in redoximorphic features than those in the soil matrix. Mineralogical composition of redoximorphic features showed that lepidochrosite is the dominant form of Fe in both reduced paddy as well as in nonpaddy soils.

Some soil physical and chemical characteristics were analyzed in order to reveal the relationship between forest soils and regeneration patches. Gorazbon district of Kheyrud was selected as a case study for the research area. All regeneration patches were recorded using GPS device. To assess the spatial structure and to quantify the metrics of regeneration patches, analyzing of landscape metrics in combination with gradient analysis in GIS and FRAGSTATS being utilized. The spatial analysis results indicated that the physical and chemical properties of forest soils in relation with regeneration patches are the most effective factors which were showed the regeneration distribution. Medium soil texture (Loam-Clay Sand), suitable drainage, sufficient moisture, phosphorus, nitrogen, pH, organic matter and soil structure are the most important variables which were determined the regeneration interval patches in the study area, Thus, the results showed that the soil texture was the effective factor in relation to forest stands distribution.

Carbon (C) and organic nitrogen (N) mineralization processes play key roles in supplying nutrient elements essential for plant growth. On the other hand, since the low organic matter content of agricultural soils of arid and semi-arid areas, microbial activities are often limited by carbon in these types of soils. Enhancement of microbial activities and populations could be achieved by returning plant residues to soil. Application of such acid-producing materials as sulfur may eliminate low uptake of some nutrients and slow decomposition of plant residue in calcareous soils, respectively in short and long-term in these soils. Therefore, the purpose of this study was to evaluate the interactive effects of plant residue and sulfur additions on microbial activities including C and N mineralization as well as their mineralization rates in a calcareous soil from Iran. This study was performed using a factorial experiment arranged in a Completely Randomized Design (CRD) with three replications under laboratory incubation conditions. Treatments included were different plant residues (i.e., wheat, alfalfa, corn, rice, almond, walnut as well as grape) and sulfur levels (i.e. 0, 5 and 10 t ha-1). We evaluated effects of plant residue and sulfur applications on C and N mineralization to over 97 days of incubation period. Results show that plant residue application had a positive and significant effect on carbon and nitrogen mineralization and their mineralization rates, and led to C mineralization enhancement up to two fold. The effect of plant residue on N mineralization depends on the chemical quality and C/N ratio of the residue. The effect of sulfur additions on C mineralization and its mineralization rate was highly significant, as it caused an increase in microbial respiration during incubation time but its addition didn’t have significant effect on N mineralization and its mineralization rate. The interactive effects of plant residue and sulfur utilization on C and N mineralization primarily depend on chemical quality of plant residues and the level of applied sulfur. Briefly, the residues with more recalcitrant compounds such as lignin, showed less microbial activities.

In order to improve the performance of irrigation networks, provide higher flexibility levels and improve water delivery methods, application of automatic control systems is suggested. In the coarse of the present study, a mathematical model of automatic pivot weir as based on PID control logic in combination with ICSS hydrodynamic model is developed. The developed model was tested under high flow variations on standard canal number two ASCE. The slope of the canal is mild; it is 28 KM long, provided with 8 reaches each reach equipped with an orifice off take along with a regulating structure at the end. Water level variation and performance indexes MAE and IAE were analyzed. The results indicated that maximum error in the worst conditions amounted to 4% which is appropriate within practical terms. Water deviation was corrected within a few minutes. Therefore, it could be concluded that the developed model for automatic pivot weir is able to properly control the water level in irrigation canals.

Recent decline in the Urmia Lake (LU) level makes it crucial to consider thE issue more than any time before. For this, a comparison of the lake level with the Van Lake water level that is close enough to the LU and benefits from relatively similar climatic conditions can be an effective approach. This topic forms the objective of this research work, in which the trend, regime shift and coherency analyses are implemented. The results indicated a negative trend in the Urmia Lake level, while the vice versa occurred in case of the lake Van. Coherency analysis indicated similarities in annual and inter-annual frequencies of the two lake levels to be 1.3 to 12 years. However, in the case of short term periods, namely less than 4 months, the relations are associated with laggings behind and transpositions.