February 2012 issue
[3(1) 2012]
Impact of vegetation cover on urban and rural areas of arid climates

Abdul Rahman O. Alghannam, Mohammed Refadan Alhajhoj Al-Qahtnai

Abstract

Analysis of air temperature differences between rural and urban areas in Al-Hassa oasis in the eastern province of the Kingdom Saudi Arabia has proven the existence of an urban heat island (UHI) effect. This study was conducted to investigate the relationship between urban micro-climate and the density of the surrounding dates tree vegetation and also to estimate the cooling effect imposed by rural environment in Al-Hassa oasis. Results of temperature and relative humidity of the rural towns revealed a strong cooling tendency imposed by the thick vegetation cover. Results indicated a peak difference of the minimum temperatures of  9.8 C, maximum temperatures of 4C , and an average difference of 6.6C between the rural and urban areas. This outcome was evaluated through the calculation of UHI for the urban and rural areas. It is evident that the mean hourly UHI and relative humidity reference RH have a negative correlation (r= - 0.61) at significance level of P= 0.01. In total, rural areas with a higher humidity difference would exhibits lower UHI.

Pages 1-5 | Full Text PDF
Determination of wheel-soil rolling resistance of agricultural tire

Masoud Gharibkhani, Aref Mardani, Farshad Vesali

Abstract

So far many researchers have tried both theoretically and practically to define tire rolling resistance. In this research, two predicting models of tire rolling resistance were evaluated and compared. Bekker model and one of the Waterways Experimentation Station method models were selected as predicting models. Using a single wheel tester, some experimental tests on a controlled soil bin filled with clay loam soil, were performed to validate the selected models' rolling resistance accuracy. Decision tree was used to predict the effect of tire inflation pressure and vertical load on rolling resistance.  A towed tire was tested at different levels of inflation pressure (34.5 to 207 kPa) and normal load (0.981 to 4.905 kN). Effects of these factors on rolling resistant were analysed. The models related to WES-method, offers a great number of different models which are applicable for typical soil-tire systems. Wismer and Luth model (as a WES model) showed the better result for rolling resistance prediction. Bekker model (as a semi- analytical model) was unmeet for predicting the rolling resistance. The accuracy of decision tree was 97% for predicting these parameters' effect on rolling resistance. So, the decision tree appeared to be a good method for fast and accurate prediction of rolling resistance.

Pages 6-11 | Full Text PDF
Effect of explants source and different hormonal combinations on direct regeneration of basil plants (Ocimum basilicum L.)

Farhad Asghari, Bahman Hossieni, Abbas Hassani, habib shirzad

Abstract

Ocimum basilicum L. a herbaceous species belonging to the lamiaceae family is considered as a valuable plant for its pharmaceutical, aromatic and culinary properties. The major problem with the use of Lamiaceae species for pharmaceutical purposes is the plant to plant variability, mainly due to genetic and biochemical heterogeneity. In vitro shoot regeneration and multiplication is an impressive mean for precipitate propagation of species in which it is necessary to obtain a progeny with a high level of uniformity. In this research, two successive experiments were performed: first, the effects of explants source on MS medium supplemented with four different concentrations of BAP were studied in order to investigate the morphogenic responses; and second, the effects of different levels of two growth regulators (BAP and IAA) either individually or in combination on multiple shoot induction from nodal segments were evaluated. Maximum percent of regeneration (96.670.33) and average number of shoot (5.61.15) were observed on the medium containing 11 M BAP + 0 M IAA. Regenerated shoots were separated and rooted on the same half strength MS medium supplemented with 3.42 M IAA alone for two weeks. Similarly in the second experiment, increasing BAP concentration led to decreased rooting. Moreover, a positive correlation between increasing the BAP level in culture media and vitrification of regenerated shoots was observed. The lowest and the highest vitrification values were achieved in the media containing 0 and 33 m BAP, respectively.

Pages 12-17 | Full Text PDF
Research Note

Response of hydroponically grown tomato and solution acidity to ammonium as a nutrient solution 

Amir Sadeghpour, Emad Jahanzad

Abstract

Impaired growth and yield restrictions have been reported as a result of using ammonium as sole or dominating N source of nitrogen. To study the effects of different ammonium supply on growth of tomato plants and changes in pH of the soilless solution, a greenhouse experiment was conducted in a Randomized Complete Block Design with seven ammonium concentrations (0, 6, 12, 25, 50, 75, 100%) replicated three times in 2011. Roots and shoots fresh weights as well as pH of the solutions were measured in this study. Visual observations were also recorded. The results of the experiment indicated that increasing the ammonium concentration in the soilless solution was detrimental to the tomato plants. The highest shoot and root fresh weights were obtained from the 0 and 6% ammonium concentration followed by normal pH changes in their concentrations showing that there was no destructive damage to tomato plants, unlike high amount of ammonium. These results were supported by the visual observation results recorded during the experiment. Results of this study suggests that to maintain a normal pH at the root zone and to prevent detrimental damages to the tomato plants, ammonium concentrations should be kept in a low level.

Pages 18-21 | Full Text PDF
Effects of puddling intensity on the in-situ engineering properties of paddy field soil

M. Rezaei, R. Tabatabaekoloor, S. R. Mousavi seyedi, N. Aghili Nategh

Abstract

Puddling may have an effect on the physical and mechanical properties of soil. Puddling intensity (the number of puddler passes) to a required level has always been a challenge for many farmers. Field experiments were conducted to determine the effect of puddling on the hydraulic conductivity, bulk density and penetration resistance at three depths (0-10, 10-20 and 20-30 cm). The treatments were puddling by one pass (P1) and three passes (P3) of a tractor-drawn rototiller and no-puddling (NP). The treatments were replicated three times and experiment was laid out in a randomized block design. Results showed that puddling caused a significant reduction (p<0.01) in soil hydraulic conductivity, bulk density and penetration resistance. Hydraulic conductivity decreased from 5.36 cm h-1 in NP to 1.12 and 0.78 cm h-1 in P1 and P3, respectively. The first level of puddling (one pass of puddler) decreased the penetration resistance of soil by about 53%, whereas puddling to higher levels decreased the penetration resistance by 15% corresponding to three passes of the puddler. The decrease in bulk density by one pass of puddler was about 6%, whereas subsequent puddling to three passes decreased the bulk density by 3%. Increasing in depth increased bulk density and penetration resistance but decreased hydraulic conductivity. Puddling only to the required level will deteriorate less the soil physical condition as compared to more intense puddling.

Pages 22-26 | Full Text PDF
Fuzzy clustering analysis for modeling of soil cation exchange capacity

Ali Keshavarzi, Fereydoon Sarmadian, Asghar Rahmani, Abbas Ahmadi, Reza Labbafi, Muhammad A. Iqbal

Abstract

The objective of this study was to investigate fuzzy clustering analysis based on subtractive clustering algorithm for modeling of Soil Cation Exchange Capacity (CEC). In this work, seventy soil samples were collected from different horizons of 15 soil profiles located in the Ziaran region, Qazvin province, Iran. The data set was divided into two subsets. One for calibration (80% data) and second for testing the models (20% data). The performance of the subtractive clustering algorithm was evaluated using an independent test data set. The vector options, i.e. (i) range of influence, (ii) squash factor, (iii) accept ratio and (iv) reject ratio were used for specifying clustering algorithm parameters to override the default values. The analyses considered 0.5, 1.25, 0.5 and 0.15 values for mentioned parameters, respectively. In order to evaluate the model, root mean square error (RMSE) and coefficient of determination (R2) were used. The corresponding values for fuzzy subtractive clustering algorithm were 0.1751 and 0.9931, respectively. Results showed that fuzzy subtractive clustering algorithm had high accuracy in predicting and modeling of soil cation exchange capacity.

Pages 27-33 | Full Text PDF


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February 2012 issue