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Showing 46 results for S. A.

A. Dehdari, A. Rezai, S. A. M. Maibody,
Volume 11, Issue 40 (summer 2007)
Abstract

Inheritance of physiologicaly related salt tolerance traits including Na+ and K+ contents, K+/Na+ ratio of young leaves and biological yield (BY) in six basic generations (P1, P2, F1, F2, Bc1 and Bc2) and their reciprocal crosses derived from crosses between Kharchia × Niknejad and Shorawaki × Niknejad were studied in sand culture under high salinity treatment (EC = 22.5 dS m-1). Generation means analysis indicated that a simple genetic model (including additive and dominance effects) is sufficient for Na+ and BY in Kharchia × Niknejad cross and for Na+, K+/Na+ ratio and BY in Shorawaki × Niknejad cross but, for other traits digenic interactions (additive × additive and dominance × dominance) were important parameters in the expression of salt tolerance of the various generations. Dominance genetic effects were predominant genetic components in most of the models. Weighted generation variances analysis suggested that dominance variance component was more important for Na+ and K+ content in both crosses. This result was confirmed by significant differences between back cross generations. Results also showed negligible dominance for K+/Na+ ratio in both crosses, multidirectional dominance for BY in Kharchia × Niknejad cross and absence of dominance gene action in Shorawaki × Niknejad. Kharchia × Niknejad cross showed, in general, more genetic variation, broad-and narrow sense heritabilities than Shorawaki × Niknejad cross, indicating the important role of primary differences between parents. These results revealed that recurrent selection followed by pedigree breeding or a selective diallel mating system may prove useful in improving salinity tolerance of wheat plants. The involvement of dominance × dominance interactions for some traits indicates that it is necessary to postpone selection for salt tolerance of wheat to advanced generations, when sufficient epistatic interactions have become fixed.
N. Hedaiat, Y. Rouzbehan, S. A. M. Modares Sanavi,
Volume 11, Issue 41 (fall 2007)
Abstract

The nutritive value of the annual alfalfa (Medicago rigidulla, Medicago polymorpha and Medicago scutellata) species harvested at flowering stage was assessed by chemical composition, in vitro dry matter and nitrogen digestibility, in sacco dry matter and nitrogen degradation (0, 8, 12, 24, 48 and 72 h) and palatability (short-term intake rate, STIR) methods. Mean values of the chemical analysis results (%) for M. rigidulla, M. polymorpha and M. scutellata respectively were as follows: OM 85.1, 86.1 and 86.9 CP 25.1, 23.8 and 15.6 NDF 23.2, 24.8 and 30.0 ADF 18.3, 19.9 and 24.0 ADIN 0.36, 0.11 and 0.22 calcium 1.4, 1.3 and 1.2 phosphorus 0.23, 0.28 and 0.24 potassium 1.5, 1.5 and 1.4. The digestibilities of the DM and OM for M. rigidulla were 0.82 and 0.79 M. polymorpha 0.83.5 and 0.80 M. scutellata 0.75 and 0.69, respectively. The degradabilities of DM and CP at outflow rate of 0.05 for M. rigidulla were 0.72 and 0.55 M. polymorpha 0.71 and 0.57 M. scutellata 0.63 and 0.58, respectively. Finally, the palatabilities (using short-term intake rate method) for M. rigidulla, M. polymorpha and M. scutellata species were 13.6, 12.8 and 11.3 (g DM/min) respectively. According to the methods used, the descending ranking order (high to low) of these species on the basis of their nutritional value was M.rigidulla, M.polymorpha and M.scutellata.
S.h. Lack, A. Naderi, S. A. Saidat, A. Ayenehband, G.h. Nour – Mohammadi, S.h. Moosavi,
Volume 11, Issue 42 (winter 2008)
Abstract

  In order to study the effects of different levels of irrigation, nitrogen and plant population on yield, yield components and reserved dry matter remobilization of seed corn (SC. 704 hybrid) a research was conducted at the experimental field in Khuzestan Natural Resources and Agricultural Science University in summer, 2004. This research was made based on three split-plot field experiments, RCBD. Each of the irrigation treatments implemented separately in each experiment have been as follows: Optimum irrigation, Moderate stress and Severe stress (irrigation after drainage 50%, 75% and 100% of available water based on 70%, 60% and 50% of field capacity, respectively). In each experiment three nitrogen levels consisting of 140(N 1 ), 180 (N 2 ) and 220(N 3 ) Kg N ha-1 were applied in main plots and subplots which consisted of three plant populations (D 1 =6, D 2= 7.5 and D 3= 9 plant m-2). There were three replications for each experiment. The results of the combined analysis of variance indicated that the effect of water deficiency stress, nitrogen and plant population on grain and biological yield was significant. With increasing severity of drought stress, the grain and biological yield decreased. The maximum grain yield was estimated to be 1017.04 gm -2 which was related to optimum irrigation treatment. Grain yield reduction was mainly due to reduction of grain per ear and 1000 seed weight. The increase of nitrogen consumption caused an increase in grain yield. The positive effect of nitrogen application on grain yield considerably decreased as a result of the increased water deficiency in soil. The response of grain yield to plant population was positive. The contrary to interaction effects of irrigation and nitrogen, and irrigation, nitrogen and plant population, the interaction effects of irrigation and plant population and also nitrogen and plant population on grain yield were significant. The results indicated that the difference between different levels of irrigation in the case of dry matter remobilization rate was significant. The least and the highest remobilization rate of reserved dry matter was related to optimum irrigation and drought moderate stress treatment, respectively. The efficiency and contribution of remobilization in grain yield increased in response to increasing severity of drought stress, but these traits significantly reduced as a result of nitrogen consumption. Remobilization rate and contribution of reserved materials to grain yield in the highest density (D3) were significantly more than other densities. According to the results of this study, under drought stress conditions, the decrease of inputs consumption, in addition to the decrease of costs, will be followed by the increasing efficiency use of the resources.


M. R. Kalbassi, S. A. Johari,
Volume 12, Issue 44 (summer 2008)
Abstract

In order to reduce the adverse effects of sexual maturation on growth and survival of rainbow trout, production possibility of all-female triploid was investigated by means of early heat shock on eggs fertilized by masculinized male’s sperm. Fish ploidy level was determined by erythrocyte size measurement and confirmed by gill nucleolus (NORs) counting as well as chromosome number. Sexual ratios and gonad development were determined by histological studies. Final results showed that progenies produced by mating sex-reversed (masculinized) males and normal females were totally female (100 %). Also, applying early heat shocks (26.5° C lasting 20 min, 20 min after egg fertilization) induced about 80 % triploidy in fishes. All-female triploid, all-female diploid and mixed-sex diploid fishes did not show any significant difference in incubation stages (eyed-stage egg rate, hatching, survival from hatching to active feeding), (P>0.05). Eyed-stage eggs rate, and hatching rate of eyed eggs in mixed-sex triploids were significantly lower than in other treatments (P<0.05). Testes development in diploid males was similar to that of triploid and was in early stages of spermatogenesis in 8 month old fish. Also, diploid ovaries were packed with oocytes at previtellogenic or perinucleolus stages. Although they showed distinct lamellar structure of an ovary, triploid ovaries contained no oocytes
K. Samei, A. Arzani, S. A. M. Mirmohammadi Maibody,
Volume 12, Issue 45 (fall 2008)
Abstract

Field crop landraces are valuable genetic sources. Twenty populations of Persian clover (Trifolium resupinatum L.) collected from different areas of Iran were used in this study. DNA extractions were carried out using minipreparation method with equal amount of leaves from 30 plants of each population. DNA samples from 20 clover populations were evaluated using semi-random (ISJ) markers. Ten primers out of 30 which used IT (intron-targeting) and ET (exon-targeting) primers produced repeatable bands. Cluster analysis was conducted using NTSYS software and UPGMA method based on Jaccard's similarity matrix. Primers totally produced 111 bands, of which 93 bands (%93) were polymorphic among clover genotypes. The greatest and least amplification fragments belonged to IT15-31 and ET18-4 primers, respectively. Average band number per primer was estimated 11.1 bands. Furthermore, IT primers produced more polymorphic DNA fragments with higher resolution. Based on cluster analysis and cutting dendrogram in 0.8 similarity coefficients, clover populations were divided into five groups in which Kazerun and Kermanshahi (1) individually formed a separate cluster. According to similarity matrix, the least similarity (%42) belonged to Alvijan and Kazerun and the highest similarity belonged to Chegeni and Haftchin Hamedan. Clustering based on semi-specific PCR method almost substantiated the grouping based on geographical origin. Considering the results, it is concluded that PCR-based semi-random marker technique can be used for genetic diversity study of Persian clover as well as discrimination of its cultivars.
H. R. Balouchi, S. A. M. Modarres Sanavy, Y. Emam, M. Barzegar,
Volume 12, Issue 45 (fall 2008)
Abstract

Water deficit, ultraviolet radiation and CO2 concentration enhancement are three environmental stresses that affect nutrition of human in future. This research was conducted in the Research Greenhouse of Faculty of Agriculture, Tarbiat Modares University in 2006, in order to study leaf qualitative traits of durum wheat under different levels of carbon dioxide (400 and 900 ppm), ultraviolet radiation (UV A, B and C) and water deficit (up to %60 of field capacity). Ultraviolet radiation enhancement increased anthocyanin, flavenoids and carotenoids of durum wheat leaf. There was no significant interaction effect between carbon dioxide and water deficit on anthocyanin and carbohydrates. Also, the interaction effects among the three factors were not significant on anthocyanin, carotenoids, chlorophyll a and a+b. Water deficit decreased leaf proteins. Increasing intensity of ultraviolet radiation and carbon dioxide enrichment decreased soluble leaf protein in durum wheat under water deficit conditions. The results showed that three main environmental stresses which reduce leaf pigment and plant protection due to negative effects of these stresses along with soluble leaf protein reduction decrease qualitative and quantitative yield of the wheat variety.
S. A. Kazemeini, H. Ghadiri, N. Karimian, A. A. Kamgar Haghighi, M. Kheradnam,
Volume 12, Issue 45 (fall 2008)
Abstract

In order to evaluate the interaction effects of nitrogen and organic matter on growth and yield of dryland wheat, an experiment was conducted at the research station of the College of Agriculture, Shiraz University at Bajgah in 2005 and 2006. The experimental design was split plot in which three levels of nitrogen (0, 40, and 80 kg N ha -1) were main factors and additive organic matters including liquorice root residue at 15 and 30 Mg ha -1, municipal waste compost at 10 and 20 Mg ha -1, and wheat residues at 750 and 1500 kg ha -1 (all rates equivalent to 50 and 100%) were sub factors. A check treatment (no additive materials) was also included in the experiment. Results indicated that with increasing nitrogen level from zero to 40 and 40 to 80 kg ha-1, wheat yield increased significantly. Among yield components, number of seeds per spike increased significantly with zero to 40 and 40 to 80 kg nitrogen ha-1, but number of spikes m-2 increased significantly only when nitrogen level was increased from zero to 80 kg ha-1. Compared to check (no additive materials), maximum wheat grain yield (32%) was obtained from 100% compost application. Results of nitrogen and organic matters interaction effects indicated that 100% compost application and increasing nitrogen level from 40 to 80 kg ha -1 had no significant effect on dryland wheat yield. This showed the positive impact of compost application on the reduction of nitrogen fertilizer. Thus, it appears that 50% of the required nitrogen fertilizer could be replaced by compost. Applying organic matter increased soil water in both years, however, among organic matters, compost had a more pronounced effect on increasing soil water.
M. Bahreini Touhan, E. Dordipour, S. A. Movahedi Naeini,
Volume 14, Issue 53 (fall 2010)
Abstract

Kinetical study on non-exchangeable potassium (NEK) release is necessary for management, optimum use of soil resources, availability and supplying power of potassium. Information about NEK release rate in Golestan soils is limited. The aim of this study was to investigate the NEK release of saturated soil sample by calcium using acid citric and CaCl2 extractants from 2 to 1844 h duration in 12 dominant soil series in Golestan province. Different soils indicated various responses to continuous extraction. The rate of K released in different soils was lower in CaCl2 than that of Citric acid. Potassium release was faster in earlier periods of the extraction in all soils followed by a lower release rate. Due to high coefficient of determination and low value of the standard error of the estimate, the NEK release kinetic by citric acid and CaCl2 were well described by Elovich and Parabolic diffusion equations and Power, First order and Elovich equations, respectively. Therefore, NEK release rate was controlled by K diffusion from weathered surface of soil minerals.
J. Abedi- Koupai , S. S. Eslamian1, S. A. Gohari , S.a Gohari , R. Khodadadi ,
Volume 14, Issue 54 (winter 2011)
Abstract

Channel lining is essential to increase resistance against scour, reducing water losses and as a result increase water conveyance efficiency. Since the canal lining has significant costs, selection of type of lining must be made with great care and with considering engineering properties. One of the conventional lining for water conveyance cannel is concrete lining. Because of advantages of concrete lining including durability (about 40 years) and low maintenance costs, this type of lining is the best option in many regions, however the construction expenses is high. So far many researches have been published about the types and the durability of concretes containing synthetic pozzolans. Due to high production of wheat in our country, nano particles of wheat ash sheath (NPWAS) were used. In this study the mechanical properties of concrete (compressive strength, tensile strength and durability) incorporating nano-particles of wheat ash sheath were investigated. The results showed that the compressive and tensile strength of samples incorporating 20 percent of NPWAS has not statistically significant difference (P<0.05) with the values of tensile and compressive strength of control samples. Therefore, the optimum replacement percentage of NPWAS was 20 percent by weight of cement. Moreover, results of durability of concrete samples showed that concrete containing 20 percent NPWAS were more durable than control samples in the magnesium sulfate solution. NPWAS with having 90.56 percent of silicon dioxide, high pozzolanic activity and ability to perform substantial chemical reaction with calcium hydroxide would decrease porosity and increase resistance of concrete.
F. Salehi, M. J. Bahrani, S. A. Kazemaini, H. Pakniyat, N. A. Karimian,
Volume 15, Issue 55 (spring 2011)
Abstract

Crop residues are beneficial substances that can bring about important changes in soil biological, chemical and physical properties and can also increase or stabilize crops yield. A field experiment was carried out at Research Station of College of Agriculture, Shiraz University, Shiraz, Iran, to determine the effects of wheat (Triticum aestivum L.) residue rates in combination with N levels on some soil properties in common bean (Phaseolus vulgaris L.) cultivation for two years (2008-2009). The experiment was conducted as split split-plot arranged in a completely randomized blocks design with three replications. Treatments were two red bean cultivars as main plots, N levels (0, 34.5, 69, and 103.5 kg ha-1) as sub-plots and residue rates (0, 25, 50 and 75%) as sub sub-plots. The results showed that application of crop residues significantly increased soil organic carbon, N, K, and P contents. Heavy crop residue (75%) application had no effects on these soil properties. Thus, retaining 50% crop residue was optimum for proper soil quality. Increased N application increased soil N, decreased P and K contents, and had no effects on organic carbon.
S. Dodangeh, J. Abedi Koupai, S. A. Gohari,
Volume 16, Issue 59 (spring 2012)
Abstract

Due to the important role of climatic parameters such as radiation, temperature, precipitation and evaporation rate in water resources management, this study employed time series modeling to forecast climatic parameters. After normality test of the parameters, nonparametric Mann-Kendall test was used in order to do trend analysis of data at P-value<0.05. Relative humidity and evaporation (with significant trend, -0.348 and -0.42 cm, respectively), as well as air temperature, wind speed, and sunshine were selected for time series modeling. Considering the Autocorrelation function (ACF) and Partial Autocorrelation function (PACF) and trend of data, appropriate models were fitted. The significance of the parameters of the selected models was examined by SE and t statistics, and both stationarity and invertibility conditions of Autoregressive (AR) and Moving average (MA) were also tested. Then, model calibration was carried out using Kolmogorov-Smirnov, Anderson- Darling and Rayan-Joiner. The selected ARIMA models are ARIMA(0,0,11)*(0,0,1), ARIMA(2,0,4)*(1,1,0), ARIMA(4,0,0)*(0,1,1), ARIMA (1,0,1)*(0,1,1), ARIMA (1,0,0)*(0,1,1) for relative humidity, evaporation, air temperature, wind speed and sunshine, respectively. The fitted models were then used to forecast the parameters. Finally, trend analysis of forecasted data was done in order to investigate the climate change. This study emphasizes efficiency of time series modeling in water resources studies in order to forecast climatic parameters.
S. A. Ghasemi , Sh. Danesh,
Volume 16, Issue 61 (fall 2012)
Abstract

In this research, the quality of the effluent from the City of Mashhad wastewater treatment plants was evaluated based on Ayers and Westcot irrigation water quality guideline, and the potential impacts of these effluents on soil and plants were assessed. For this purpose, the effluent from each of the three existing wastewater treatment plants was sampled on a regular basis, for a period of one year, and their parameters of importance in regard to the agricultural use such as pH, electrical conductivity (EC), concentrations of Sodium, Calcium, Magnesium, Chloride, Boron, Nitrate (NO3-N), bicarbonate and heavy metals were measured. Based on the obtained results, the agricultural use of the effluents from the wastewater treatment plants has severe restriction in regard to the bicarbonate concentrations (8-12.1 meq/L). Also, in view points of parameters such as EC (1250-1874 µS/cm), Sodium (5.8-8.7 as SAR), Chloride (3.2-6.5 meq/L) and adj RNa (7.8-11.7), the effluents were categorized in the class of waters with low to moderate restrictions. However, the measured values of pH (7.3-8), Boron (0.2-0.8 mg/L), Nitrate Nitrogen (0.5-4.2 mg/L) and heavy metals did not indicate any restrictions for agricultural use. From the results of this research, it can be concluded that the use of effluent as irrigation water requires careful planning, monitoring and management strategies.
M. Liaghat, F. Khormali, S. A. Movahedynaeini, E. Dordipour,
Volume 16, Issue 61 (fall 2012)
Abstract

Studies on the soils of western Golestan province show that regardless of increased rain and presence of clay minerals with high cation exchange capacity, potassium extractable with ammonium acetate is low. In order to find the reason for this low amount of available K, clay minerals and micromorphology of the soil porosity were studied. Twenty disturbed and undisturbed samples from each horizon were taken for physicochemical properties, mineralogy and micromorphological studies. Four selected profiles included Gypsic Aquisalids, Typic Endoaquepts, Typic Calcixerolls and Typic Hapludalfs. The results showed that in addition to the clay content and type of clay minerals in soils that can affect soil available K (Kava.), it seems soil porosity can also affect Kava. mainly through their effects on extension of roots, water and nutrients transmission. Favorable content of clay and dominance of smectites in Mollisols and also higher porosity and dominance of channel porosities caused the presence of higher Kava, in these soils. presence of HIS. poor soil drainage, reduction of Fe3+ in smectite crystal lattice in Inceptisols, and also less amount of porosities caused the presence of higher potassium fixation and reduction of Kava. in these soils.
S. Jafari, Z. Iranshahi , Gh. Fathi, S. A. Syadat,
Volume 16, Issue 61 (fall 2012)
Abstract

Cadmium is a toxic element in plant nutrition and is considered as a contaminant of food and feed. A greenhouse experiment was carried out to examine the effects of combined application of cadmium and zinc on responses of wheat on a clay loam soil texture. This experiment was designed in a factorial experiment with randomized complete block design (RCBD) and four replicates per treatment. Three levels of cadmium (Cd 0, Cd 50 and Cd 100 mg kg-1) and three levels of zinc (Zn 0, Zn 50 and Zn 100 mg kg-1) were added to the pot in factorial(9 treatments), and then Chamran seed variety of wheat (triticum aestivum L.) was planted in each pot. The statistical analyses showed that Cd application significantly (P0.01) decreased grain, straw, and total yield, but Zn application increased these parameters significantly (P0.01). Application of Cd separately decreased the grain yield by 61.5 while application of Zn separately increased the grain yield by 36.9. Cd application increased the Cd concentration and uptake by grain and straw as well as total uptake but by increasing Zn application, Cd uptake was decreased by wheat. Cd concentration was higher in straw than that grain, but Zn showed a different trend. Decreasing Zn applications decreased total uptake of Cd from 42.9 in Zn0 to 7.8 mg kg-1 in Zn100 treatment. Although this soil was very calcareous, this characteristic did not control Cd absorbtion.
S. A. Mohseni Movahed, M. Akbari, P. Salehi Moghadam,
Volume 17, Issue 66 (winter 2014)
Abstract

As pressurized irrigation is not possible for all circumstances, the use of modern techniques in surface irrigation is essential. In this paper, BISEDOM, a new mathematical model for evaluation, design and optimization of border irrigation is introduced. The effects of weighting coefficients of indicators are investigated based on the potential to improve and the most appropriate weighting scheme in optimization process is presented. In this model, volume balance equations for hydrodynamic simulation and SA method for optimization steps are used. Due to the nature of the SA, its parameters are determined by the method of sensitivity analysis. In this model, evaluation of different combinations of decision variables (inlet flow, length, width and slope of the strip) and consequently the performance of irrigation efficiencies reagent strip in an objective function is possible. Finally, the results indicate that the proposed method for weighted indicators has significant effects on improving performance of border irrigation. Model validation results in three parts of design, evaluation and optimization in comparison with SIRMOD and asymptote method showed that the results are very close to each other. The results also indicate that the proposed model has a good efficiency in comparison with other existing models especially for optimization purposes.
S. A. A. Hashemi,
Volume 17, Issue 66 (winter 2014)
Abstract

Check dams are considered as main measures for flood and sediment control in watersheds, and their uses have been rapidly increased from 1990 onward in Iran. This research is done in Darjazin watershed in north of semnan city. The check dams have been constructed from 15 years ago in two sub basins of the watershed for flood control in Mahdishar. More than 650 check dams were evaluated for effects on flood. The collected data in the field was fed to ArcGIS software. The effects of these structures on flood reduction were evaluated by HEC-GeoHMS extension and HEC-HMS model. Because of homogeneity of watershed management projects in the basin due to building more check-dams in different watercourses, any flood discharge is related to check dams. Evaluating the effects of check dams on flood by t-test showed significant differences between flood discharge before and after construction of check dams at 5 percent level. So, check dams have been able to reduce flood discharge by 16.7 percent on average.
H. Kashi, H. Ghorbani, S. Emamgholizadeh, S. A. A. Hashemi,
Volume 18, Issue 67 (Spring 2014)
Abstract

Change in land use and tillage practices has great influence on soil physical and chemical properties. The present study has focused on the effects of converting undisturbed soil to agricultural lands. Chemical and physical soil properties, infiltration, cation exchange capacity (CEC), electrical conductivity, pH, bulk density, porosity, sodium, potassium, total Ca + Mg, organic matter percentage, sodium adsorption ratio (SAR) and lime percentage were measured using standard frequently used methods. Fifty soil samples from agriculture land and other 50 soil samples from undisturbed land were collected from 0 – 30 cm depth and different statistical analysis were performed. Agriculture land is Cultivated for more than 20 years. The results showed that change in land use from undisturbed to disturbed soil did not significantly changed soil organic matter content. Also, soil electrical conductivity showed a huge increase whereas pH showed non-significant changes due to land use change. Unlike pH, SAR, organic matter percentage and lime percentage, some other soil parameters showed significant decrease in quality through land use change. Correlation coefficients of the effective factors were calculated to explain the main reason for lowering soil quality. The results showed that sodium in EC bulk density in porosity and CEC sodium and Ca+Mg in SAR EC in soil infiltration and Ca+Mg in organic matter showed the most correlation.
M. Hosseini, S. A. Movahedi-Neeni, M. Zeraat Pishe,
Volume 18, Issue 68 (summer 2014)
Abstract

Effects of five various tillage systems on soil porosity, volumetric water content, diurnal and nocturnal soil temperatures, plant water uptake and dry matter yield was investigated using a completely randomized design with five treatments and four replications in Gorgan University of Agricultural Sciences and Natural Resources research farm located in Seyed-Miran during 2009-2010 growing season. Tillage systems were: moldboard plough followed by one discing (20-25 cm) rototiller (12-17 cm) double disc (8-10 cm) Chisel plow (25-30 cm) No-tillage. Results show that during all stages of wheat growth, the highest and the lowest soil porosities at 0-8 cm depth were obtained by moldboard plough and No-tillage treatments respectively. For all stages except before tillering and harvest, the highest soil porosity obtained by moldboard treatment at 8-16 cm depth. Increasing tillage intensity increased those porosity that keep water in potentials greater than -5 and those in potentials less than -15 bar. No-tillage and moldboard induced the highest and the lowest soil temperatures respectively before earring stage. Tillage intensification, increased soil porosity and root density. More roots reduced soil water content in response to increased water uptake by wheat, resulting greater dry matter accumulation.
S. A. Banimahd, D. Khalili, A. A. Kamgar-Haghighi, Sh. Zand-Parsa,
Volume 18, Issue 70 (winter 2015)
Abstract

In the present research, the performances of six empirical models, i.e., simple threshold exceedance, fixed proportion exceedance, quadratic function of storage, power function of storage, cubic function of storage, and exponential function of storage were investigated for estimation of groundwater potential recharge in a semi-arid region. First, the FAO Dual Crop procedure was used to calibrate evaporation from bare soil during the occurrence of potential recharge period. Then, the empirical models were calibrated utilizing soil moisture and potential recharge data. For validation of empirical models, soil moisture and potential recharge were simultaneously estimated for an independent event. Results indicated that 5 of the six models (except for the simple threshold exceedance model) were able to estimate potential recharge with a reasonable accuracy, showing the maximum computed value of NRMSE (Normalized Root Mean Square Errors) of 24.4 percent. According to validation results, exponential, cubic, and power function models provided better estimation of potential recharge in comparison with the linear models. Also, all of the applied empirical models were able to simulate soil moisture during the recharge period with an acceptable accuracy. Finally, the exponential model with minimum NRMSE value for soil water simulation and also acceptable performance of potential recharge estimation was recommended for estimation of potential recharge in the study area.


S. Shakeri, S. A. Abtahi, N. A. Karimian, M. Baghernejad, H. Owliaie,
Volume 19, Issue 73 (fall 2015)
Abstract

The aim of this study was to assess the kinetics of nonexcheangable potassium release in surface and subsurface soil horizons, using organic and inorganic extractions, in Kohgilouye-va-Boyerahmad Province. Kinetics of K+ release was studied by successive extractions of K from 64 selective surface and subsurface soil samples, using 0.01 M CaCl2 and 0.01 M oxalic acid, for 1948 h, with two replicates. Nonexchangeable K+ release was fitted by Elovich, Pseudo-first order, Power function and Parabolic equations. Result showed that the average nonexchangeable K+ released (extracted by 1M HNO3) was 356 mg/kg, while those extracted by CaCl2 and oxalic acid after 1948 h were only 58% and 52% of the total amount of nonexchangeable K+ of the soils, respectively. In all soil samples, nonexchangeable K+ released by oxalic acid was less than that released by CaCl2, due to the high buffering capacity resulting from high carbonates in the soils. Potassium release rate in Elovich and Parabolic equations were significantly correlated with non-exchangeable potassium and some physical and chemical characteristics.  Based on high Coefficients of determination (r2) and low Standard errors (SE), Elovich, Power function, First order and Parabolic equations were selected as the best equations for prediction of K+ release from the soils.



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