جستجوی مقالات مرتبط با کلیدواژه "grass" در نشریات گروه "آب و خاک"

Crude oil is a complex combination of many hydrocarbon and non-hydrocarbon compounds, including heavy metals, which affect the physical and chemical properties of the soil, cause the soil particles to stick and connect and then cause the soil to become stiff and impenetrable. Contamination of soil with petroleum hydrocarbons is a significant environmental problem, which has received remarkable attention in recent decades. Petroleum hydrocarbons are resistant and hazardous pollutants. Some petroleum hydrocarbons such as benzene are mutagenic and carcinogenic materials for humans. There are many physical and chemical methods to remediate oil-contaminated soils. Phytoremediation is a relatively new technology for refining contaminated soils in which resistant plants are used to remove or reduce the concentration of inorganic, radioactive, and organic pollutants, especially petroleum compounds, from the environment.

Sufficient amounts of about 50 kg of soil contaminated with petroleum hydrocarbons were collected from regions (0-30 cm soil depth) adjacent to the oil wells west of Kermanshah province. Uncontaminated soil samples were also taken from sites at the lowest distance to the contaminated sites. The aim of this study was to compare the efficiency of different plants to remove total petroleum hydrocarbons from oilfield soils. In this study, after determining the total amount of petroleum hydrocarbons, the contaminated and uncontaminated soils were mixed in 4 treatments with different weight ratios (0, 10, 25, and 35%). This experiment was established as completely randomized design with 3 replications for 6 different plants (Barley, Grass, Alfalfa, Hemp, Camelina, and Vicia ervilia). One treatment without plant was considered to remove soil matrix effects on petroleum hydrocarbon concentrations. Plants were harvested at the end of their growing season (90-120 days). Soils and plant samples from the experimental pots were analyzed for their important properties (including some physiological characteristics of the plants, as well as the percentage of reduced petroleum hydrocarbons in the soils). The gravimetric method was used to determine the concentration of petroleum hydrocarbons in the soil. After measuring the properties of the soil and plant, the normality of the data was checked by the Anderson–Darling test, and the homogeneity of the variance of the treatments was checked by using Levene's test. Analysis of data variance was done using ANOVA and average data comparison was done using LSD test at 5 and 1 percent probability levels (SAS 9.4 and SPSS 26).

In general, the growth of most plants showed a decreasing trend in proportion to the increase in soil pollution levels. However, the growth decline rates of different plants were not similar. Camelina was very sensitive to oil pollution and the plant could not tolerate pollution even at 10% level. After camelina, alfalfa was highly sensitive to oil pollution. The highest dry weight of the aerial parts of the hemp plant in the soil without oil contamination was observed at the rate of 111.22 grams in the pot. The leaf area of all studied plants in contaminated soils decreased compared to the control treatment (without contamination) so with the increase in the percentage of contamination, the leaf area of the plants was significantly reduced. The highest amount of leaf surface was observed in unpolluted soil and in the hemp plant. Except for the Camelina plant, which was completely destroyed at different levels of pollution, the rest of the plants showed a noticeable decrease in growth. The total petroleum hydrocarbons in soil were measured again 120 days after the start of cultivation, and its difference with the total amount of petroleum hydrocarbons at the beginning of cultivation was determined as the reduction of petroleum hydrocarbons and reported as a percentage. According to the mean comparison results, the percentage of reduced petroleum hydrocarbons was not significantly different among cultivated and non-cultivated treatments, although, it was significantly affected by soil pollution levels. Since all the studied soils contained natural bacteria and were not sterilized, the eliminated part of petroleum hydrocarbons is probably decomposed and removed by native bacteria in the soils. Therefore, the strengthening of native bacteria in these soils may increase the decomposition and degradation of petroleum hydrocarbons.

The results of this research show that the presence of petroleum hydrocarbons in the soil caused a decrease in growth and other physiological characteristics in all studied plants. Although the Camelina was able to germinate in soils contaminated with petroleum hydrocarbons, the presence of these pollutants in the soil prevented the optimum growth of the plant, so its use in subsequent studies of phytoremediation of oil-contaminated soils, was not recommended. The results showed that there is no statistically significant difference between cultivated and non-cultivated treatments at different pollution levels, and the reduction of the total petroleum hydrocarbons in the soil was probably done by native microorganisms in the soil. It is recommended to take into consideration the efficiency of the plant species used, the type of polluting hydrocarbons, and the duration of contamination in future research to obtain better results.

The emitter clogging by crop roots is a main problem for using subsurface drip irrigation system in an arid area under water stress condition. The goals of this study were to investigate the effect of treflan injection for preventing of emitter clogging by grass roots in subsurface drip irrigation (SDI) and the effect of these treflan on the visual quality of two grass species. The experiment was conducted in a factorial experiment according to completely randomized block design with three replications from 2012 to 2013. The experiment included three levels of treflan contain 0 (C0), 100 (C1) and 300 (C2) mg net Treflan per emitter per year, and two grass species of Festuca (F) and Brmudagrass ( B). The results showed that the injection of Treflan into SDI system decreased roots around the emitter outlet and consequently no emitter clogging was observed. Root penetrate and severe clogging problem was more for Brmudagrass in compared to Festuca. The results showed after two growing seasons there was no emitters clogging in high Treflan level injection. Also, increasing the concentration of treflan up to 300 mg per year per emitter had not effect on the visual quality of grass species. Due to the importance of environmental protection, it is recommended to use a high-tech emitter and dripline for subsurface drip irrigation with no or lower herbicides injection to prevent clogging of the emitter.

Applying proper irrigation management can reduce the yield loss caused by salinity. Growth responses of Seashore Paspalum, in terms of shoot and root lengths, fresh and dry weights, and the general quality of the grasses were studied hydroponically in a greenhouse under rotational levels of salinity stress. The experiment was arranged as a split plot based on randomized complete block design with four replications. Treatments include of five constant salinity levels as 5, 10, 20, and 30 gr/lit (named as Ctrl, C10, C20 and C30, respectively) as well as four more rotational salinity treatments (named as A10, A20 and A30). The results showed the maximum length of root and shoot (16.67 and 6.91 cm, respectively) was observed in Ctrl. At each salinity level, dry weight and fresh weight of shoot significantly increased in grasses grown under rotational salinity/control condition compared to their corresponding treatments under constant salinity stress condition. The percent of relative water content was higher in Ctrl, C10, A10 and A20. Also, C20 and C30 have the lower relative water content. Maximum water use efficiency observed at the Ctrl and then in A20 and A30. It concludes that rotational use of saline water causes improvement of WUE in grass.

amount of water that use by evapotranspiration. Estimation of evapotranspiration (crop water requirement) is also one the most significant stages for designing different irrigation systems, programming and correction of the water resources management. Determining crop coefficient is a necessary part of estimating evapotranspiration. Crop coefficients (Kc) are properties of plants which vary in different growth stages. Potential evapotranspiration occurs if a field of the crop had an ideal unlimited water supply. The effect of both crop transpiration and soil evaporation are integrated into a single crop coefficient. The Kc coefficient incorporates crop characteristics and averaged effects of evaporation from the soil; while in dual crop coefficient two sub-coefficients (basic crop and evaporation coefficient) are considered separately. Therefore, the dual crop coefficient approach is more complicated and computationally intensive than the single approach. Due to the importance of accurate determining of crop water requirement many researches have been done for measuring single and dual crop coefficient. The aim of this research is to determine the actual evapotranspiration and single and dual crop coefficients of linseed by lysimeter, during various stages of growth in the Shahrekord area. This research was conducted in Shahrekord University. Shahrekord is located 97 kilometers southwest of Isfahan with the geographical coordinates from 32°18'22'' to 32°21'50'' N and 50°49'22'' to 50°53'44'' E. It is topographically situated in the north of the Zagros Mountains. The annual average temperature and precipitation in Shahrekord is 11.5°C and 320 mm, respectively. This study was done in the crop year of 2014-2015. Four lysimeters were used with the length, width and depth of 190, 65 and 140 cm. respectively. After filling lysimeters with soil and before planting, samples were taken for determining the soil characteristics, in depth of 0-30 cm. One of the lysimeters was allocated to grass, for measuring the reference evapotranspiration, and three other lysimeters to the linseed. After each irrigating the drainage water was collected and then its quality and quantity was measured. The crop evapotranspiration (ETc) and crop reference evapotranspiration (ETo) were calculated by using of water balance equation. Single crop coefficient was calculated from ratio of the measured crop evapotranspiration (ETc) and measured reference evapotranspiration (ETo) and dual crop coefficient was determined using the FAO 56 method. The results showed that the initial, development, middle, late and total growing periods of linseed are 20, 14, 22, 24 and 80 days. The total values of growing degree days (GDD) for these stages are 226.5, 226.7, 379.1, 420.7and 1253, respectively. The average value of the single crop coefficient in the initial stage is equal to 0.74, in the middle stage is 1.23 and at the end of the final stage is 0.61. The single crop coefficient was also calculated using the FAO 56 method. The results indicated that the difference of single crop coefficients in these two methods was very little in the initial and middle stages, but it increased in the final stage. The basal crop coefficient, soil evaporation coefficient and dual crop coefficients were calculated using the FAO56 method. The basal crop coefficient for linseed at different growth stages of initial growth stage, middle and end final are 0.15, 1.15 and 0.2, respectively. During the initial stage, because of low green cover, the soil evaporations is the highest and it became decrease by increasing the green cover in the next growth stages. The actual evapotranspiration value of linseed that obtained from three lysimeters was equal to 444 mm during the growing season. The evapotranspiration value of linseed that calculated by dual crop coefficient (using FAO56 method) was 445.5 mm, while this value was equal to about 391 mm for the single crop coefficient (using FAO56 method). The comparison of these values clearly indicated that the dual crop coefficient can estimate the evapotranspiration more accurate than the single crop coefficient. The results showed that evapotranspiration of linseed and grass are 444 and 429 mm, respectively and it daily variations for linseed are 1 to 10 mm and for the grass are 4.3 to 8.5 mm. The main conclusion that can be extracting from this research is that the calculating of dual crop coefficient is necessary for estimating the accurate crop water requirements.

Evapotranspiration (ET), as a major component of the hydrologic cycle, is important in water resources management and irrigation scheduling. Nowadays, due to the lack of the lysimetric data in weather stations, the ET values calculated by the standard FAO Penman-Monteith model ( ) are used for grass reference crop. Also, the Penman- Kimberly model is widely applied for computing the alfalfa-reference crop ET (ETr). In the present study, the meteorological data from 6 weather stations located in the East Azarbayjan Province covering a period of 10 years were used to calculate the and ETr values. Then, the ETr to ratios were computed for all six stations during the study period. Finally, the contributions of the energy balance and aerodynamic components on the final ET values were determined using the Penman- Kimberly model, which showed the important influence of the both components on the ET process. Consequently, the use of radiation-based models e.g. Priestly- Taylor model in these stations should be carried out by special care.

Maximum Allowable Depletion (MAD) by affecting on number of irrigation in growing season and irrigation use reduction can be used as a managerial tool to save water. The purpose of this study was to investigate the effect of MAD in irrigation interval, applied irrigation water, top and root growth of grass under subsurface drip irrigation system. Three irrigation treatments which were MAD equal to 40%(W1), 60%(W2), and 80%(W3) arranged in a randomized complete blocks statistical design with three replications in 2012 and 2013 in Isfahan University of Technology. The soil moisture was measured daily using Moisture Meter GMK-770S in the root zone depth of grass to manage irrigation. The apparent parameters and root parameters of grass were collected periodically. These parameters were analyzed by Duncan's multiple range test and the results showed that the irrigation treatments had no significant effect on the root growth parameters and top weight. In the depth of 0-13 cm the maximum root volumetric density and fresh and dry root weighted density were occurred in W1, W2 and W3 treatments, respectively. On the average, 80.14% of the mentioned parameters were in of 0-5 cm depth and 19.86% of them were in of 5-13 cm depth. The maximum (3.93g/day) and minimum (3.21/day) dry biomass were observed in W1 and W3 treatments, respectively. Overall, the results indicated that although the increment of MAD to 80% in a clay-loam soil slightly decreased the shoot and root growth of mix sport grass under a subsurface drip irrigation system, it is a reasonable management solution with the aim of conserving water in the water shortage condition which had the least negative effect on apparent parameters of grass.

Reducing water consumption in greenhouses is one of the main concerns for growers. This study was conducted in order to compare actual grass reference evapotranspiration that measured with a micro-lysimeter with estimated values of the calculation methods. The site of the study is a greenhouse that located in five kilometers from city of Mahan (south of Kerman province) with altitude 1880 meters above sea level. Meteorological data have been measured in the greenhouse environment from 13 November 2011 to 22 March 2012. The reference evapotranspiration was measured by two micro-lysimeters. In this study, 12 Computational models have been considered. In order to use these methods, meteorological data, including wet and dry temperatures, mean daily temperature, relative humidity, solar radiation and sunshine duration were measured in the greenhouse. In addition, the amount of pan evaporation was measured by a reduced pan. The results showed that FAO-24 Radiation method having the best overall performance (r=0.65, RMSE=0.81, d=0.8, MAE=0.65) and Mc-Claude method did show significant differences under all conditions evaluated (r=0.11, RMSE=3.32, d=0.32, MAE=3.16) in this climate under greenhouse condition.

It is necessary that ETr (Alfalfa-reference evapotranspiration) values be converted to ETo (Grass-reference evapotranspiration) or vice versa. The main objective of this study was to develop ETr to ETo ratios (Kr values) for a growing season in Shahrekord plain، Shahrekord، Iran. Mean monthly and total (growing season) values of Kr were calculated based on 185 daily ET data set in Chaharthakhteh Agricultural Resaerch Station of Shahrekord. The ETr and ETo values were calculated using six models for developing Kr values. The models included the Standardized American Society of civil Engineers Penman-Monteith (ASCE-stPM)، American Society of Civil Engineers Penman-Monteith (ASCE-PM)، 1982 Kimberly-Penman (KP)، and modified Jensen-Haise (JH). Kr values as a function of some of the climatic variables in FAO56 Irrigation and Drainage Paper were compared with lysimeter ETr values. For the growing season، Kr values based on lysimeter study was 1. 12، which was comparable to 1. 12، and 1. 16 for ASCE-PM، and JH، respectively، but was far from 1. 27 for 1982 KP models. ETr values in each method compared to ASCE-stPM-ETo were not comparable to 1. 40 derived from Kr value based on FAO56 method.