Iranian Journal of Soil and Water Research
Year:2012 | Volume:43 | Issue:3|Papers Count:9

Cadmium is one of the most toxic pollutants in the surface soil layer the accumulation of which in soils as well as in crops is of increasing concern. In addition, zinc is a micronutrient in rice nutrition which is in interaction with Cd. A pot experiment was carried out to study the effects of zinc and cadmium on rice growth and as well on concentrations of Zn, Cd, Fe and Mn in soil. A factorial experiment was conducted based upon a randomized complete block design of three replicates including two varieties of rice (Vandana and Hashemi), two water regimes (flooded vs. nonflooded), three levels of zinc and cadmium each (0, 5 and 10 mg kg-1). The results showed that flooded vs. nonflooded conditions' shoot weight and root weight as well as root volume in the two varieties and in flooded conditions were greater than those in the nonflooded conditions. Dry matter, root volume and number of leaves inVandana variety were greater than those in Hashemi. By increasing Zn, shoot and root weight, root volume, number of leaves and tillers, stem height and water use efficiency increased but concentrations of DTPA-extractable Cd were diminished. By using Cd, the above said parameters and concentrations of DTPA extractable Zn and Fe were initially, and then decreased. By incease in Cd level, concentrations of DTPA -extractable Cd and Mn were increased. The effects of Cd and Zn levels on concentrations of Zn extractable by DTPA in soil were nonsignificant. By utilization of Cd in any level of Zn, shoot weight and water use efficiency firstly increased but then decreased.

In order to study the effects of variety, water regime, zinc and cadmium levels on concentration, content and translocation of P, Cu, Fe and Mn on rice, a factorial experiment was conducted consisting of four factors including: two varieties of rice (Vandana and Hashemi), two water regimes (flooded and nonflooded), three levels of zinc, and three of cadmium (0, 5 and 10 mg kg-1). The experiment was carried out in a randomized complete block design of three replications. The results showed that from flooded to nonflooded conditions, concentration and content of P in root and shoot, content of Fe in shoot, concentration of Fe in root, concentration and content of Mn in shoot were decreased while concentration of Cu in shoot and root and translocation of Fe being increased. By increase in Zn levels, concentration of P in root and shoot, content of P in root and concentration of Fe in shoot were initially increased but then decreased. By use of Zn, concentrations of Mn and Cu in shoot decreased. Through an increase in Cd level, content of P, Fe and Mn in shoot and root, content of Cu in root were firstly increased, then decreased while concentrations of Fe and Cu in root, concentration of Mn in shoot as well as translocation factor of Mn decreased. The effects of Cd and Zn levels were significant meaning that by use of Cd in any level of Zn, concentration and content of P in root and shoot, content of Cu and P in root, content of Fe and Mn in shoot increased at the start.

Such petroleum hydrocarbons as ethylene oligomer are among soil and water pollutants. Physical and chemical methods employed in elimination of these pollutants, in addition to being inefficient, are damaging to the environment too. Throughout the present research, powerful decomposer isolates, namely: Lysinibacillus xylanilyticus (a bacterium isolate), and Aspergillus niger (a fungal isolate) were separated (through culture enrichment) from landfill soils). The capability of these isolates to degrade ethylene oligomer as the sole source of carbon was evaluated in liquid mineral media containing 1% ethylene oligomer followed by incubation on a rotary shaker at 30°C for 30 days. Based upon this issue, fungal biomass was assessed as 0.1370 g per 100 ml culture medium. Moreover, a 3.2-fold increase in culture concentration was observed in comparison with initial culture concentration of 1.5×108 CFU.ml-1 in the bacterium culture indicating the utilization of ethylene oligomer as the sole source of carbon. FTIR analysis confirmed ethylene oligomer oxidation and formation of carbonyl groups by the isolates during the oxidation process.

In a greenhouse experiment, changes in inorganic phosphorus fractions as well as their availability in the rhizosphere of rice (Oryza sativa c.v. Khazar) crop, following an application of 40 mg P (as monocalcium phosphate per kg of soil) were investigated in paddy soils north of Iran. The study was performed as a 14×2 factorial in a completely randomized design of two factors namely: soil at 14 levels (10 calcareous vs. 4 non-calcareous) and cultivation at two levels (cultivated vs. uncultivated). Each level of soil and cultivation were performed in examined two replicates. Following a period of three months, specially designed soil tubes, buried in soil at the beginning of the experiment, were simultaneously drawn out of the cultivated and of the uncultivated pots and then immediately analyzed for P fractionation. The method of Jiang and Gu (1989) was employed for determinations in calcareous soils, of Kuo (1996) for non-calcareous soils) while the available-P was determined through Olsen method. The results indicated that in all the 14 soils, the available soil P (Olsen-P) in the rhizosphere of rice was significantly lower than that in the non-rhizosphere (uncultivated soil). But, following the plant P uptake and its addition to the extractable-P (Olsen-P) in the rhizosphere soil, the total available-P in the rhizosphere soil was higher than that in the non-rhizosphere one. In calcareous soils, dicalcium-phosphates, octacalcium-phosphates, and Al-phosphates (Al-P) in the rhizosphere of the rice crop were significantly lower than those in the non-rhizosphere soil; whereas iron oxides occluded-phosphates and Fe-phosphates (Fe-P) in the rhizosphere of rice did not significantly differ from those in the non-rhizosphere (uncultivated) soil. Only in two calcareous soils, the apatite-P in the rhizosphere of rice was significantly lower than that in the non-rhizosphere soil. In non-calcareous and acidic soils, readily soluble-P, Fe-P, and Al-P in the rhizosphere of the rice crop were significantly lower than those in the non-rhizosphere soil. Apatite-P and Fe oxide occluded-P did not significantly differ from those in the non-rhizosphere soil. The results of the research finally revealed that the Olsen extractant may underestimate the availability of P under laboratory (air dry) conditions.

Leaf Wetness Duration (LWD) is a key parameter in agricultural meteorology. Because of difficulties involved in LWD being readily measured, several methods have been developed to estimate it from weather data. Among the employed to estimate LWD, those that use physical principles of dew formation plus dew and/or rain evaporation have shown to be especially transmittable and of sufficiently accurate results, but their complexity is a disadvantage for operational use. Alternatively, empirical models have been utilized despite their limitations. The simplest empirical models use only relative humidity data. The objective of this study was to evaluate the performance of an RH-based empirical model and a Penman-Monteith physical model to estimate LWD in Sarvestan automatic station located in Fars province. The results indicated that both models during warm seasons underestimate LWD, while during cold seasons, the physical and empirical models show overestimation and underestimation, respectively. The Mean Absolute Error (MAE) in empirical model was recorded to be less than that in physical model's estimations. An adjusted optimum threshold value of relative humidity was suggested for the study which improved the estimations. Using an RH-based empirical model led to more accurate LWD estimations with less errors as compared with the previous published data. Hourly comparisons also showed that the optimum threshold model was of a more acceptable performance as compared with the other models.

Leaf Wetness Duration (LWD) is a key parameter in agricultural meteorology. Because of difficulties involved in LWD being readily measured, several methods have been developed to estimate it from weather data. Among the employed to estimate LWD, those that use physical principles of dew formation plus dew and/or rain evaporation have shown to be especially transmittable and of sufficiently accurate results, but their complexity is a disadvantage for operational use. Alternatively, empirical models have been utilized despite their limitations. The simplest empirical models use only relative humidity data. The objective of this study was to evaluate the performance of an RH-based empirical model and a Penman-Monteith physical model to estimate LWD in Sarvestan automatic station located in Fars province. The results indicated that both models during warm seasons underestimate LWD, while during cold seasons, the physical and empirical models show overestimation and underestimation, respectively. The Mean Absolute Error (MAE) in empirical model was recorded to be less than that in physical model's estimations. An adjusted optimum threshold value of relative humidity was suggested for the study which improved the estimations. Using an RH-based empirical model led to more accurate LWD estimations with less errors as compared with the previous published data. Hourly comparisons also showed that the optimum threshold model was of a more acceptable performance as compared with the other models.

Global warming has brought about changes in meteorological variable time series. These changes, accompanied with serious human intervention in nature, has resulted in hydrological changes. So the effects can be tracked down by the trend of the time series. The purpose of this study is to analyze and compare the monthly and annual trends of temperature, precipitation as well as stream flow time series of the Urmia Lake basin, using nonparametric methods. Four non-parametric statistical tests, namely: Mann-Kendall, Theil-Sen, Spearman Rho, and Sen's T tests are investigated throughout the present study. The records of 11 temperature gauging stations, 35 rain gauge stations and 35 hydrometery stations showed significant increasing trends in the basin temperature. In the case of precipitation recordings, it was different, in a way that 8% of the rain stations indicated increasing trend, while the trend being decreased in 14% of the stations. Finally for stream flows, 60% of the hydrometery stations revealed a decreasing trend. A comparison of the methods revealed (at a monthly scale), that Mann-Kendall and Theil-Sen's performance were similar. Furthermore, Sen's T and Spearman Rho methods were detected to be the ones showing the number of stations to undergo minimum and maximum significant trends, respectively. As for annual time scale, Sen's T showed to represent the maximum number of stations to be suspicious of being of non-stationary as regards the trend.

Water conveyance through pumping takes a lot of energy and cost and therefore, its application should be accompanied by exact design of pumping station as well as correct positions of pumps and their subsidiary apparatus. Sumps are designed for many pumping stations and often face the problems of vortex and irregular flows. Therefore an investigation of the general flow pattern in sumps in different hydraulic and geometric conditions and a study of the negative pressure at the bottom of the sump could help the appropriate operation of pumping project as well as reduction in the costs. These parameters could be related to energy consumption for pumping a definite discharge or volume of water, as the results reveal increase in the energy consumption due to improper design parameters and due to growing vortex formation. In this study, based upon the 3D velocity measurements in pump sump and recording of the observations, the differences of flow patterns by change of two parameters, namely: the submergence of the suction pipe and the distance between suction pipe and sump bottom at different discharge levels were investigated. The results reveal the obvious effects of these parameters on vortex formation and the negative pressure exerted at sump bottom. They also necessitate more research on the suggested relationships to augment and adjust them to varying situations.

Iran is ranked fourth for saline-sodic soils in Asia following China, India and Pakistan. Therefore, if coupled with waterlogging, drainage would be an inevitable and indispensable activity agriculture in most irrigated parts of Iran. Drain installation depth is one of the main economic as well as environmental challenges in design and construction of drainage systems. Deep pipe drain installation cause the effective control waterlogging, but damage the drain water quality. Deeper drain installation leaching more of salts from partly a deeper soil profile, throughout the current study. Extracting salts from beneath root zone. A laboratory test was carried out in which a 2×1×0.5 m3 sand tank filled with three 30 cm layers of clay-loam being employed to investigate the influence of drain installation depth on the drained water quality. Drain pipes were installed at 0.25, 0.5 and 0.85 m depths. Initial electrical conductivity of soil extracts (ECe) was estimated as 12.7, 31.2 and 67.5 dS/m, for the three layers, respectively. The results indicated that the maximum drain water EC (ECdw) increased by depth, being recorded as 43.1, 55.6 and 131.8 dS/m for 0.25, 0.5 and 0.85 m depths, respectively. Drain water depths for the tests were recorded as 22.5, 25.5 and 27 mm. The results showed that decrease in drain installation depth improved drain water quality, decreasing the drain water volume and while leading to an improvement in the environmental impacts of drainage.