Showing 1096 results for Ro
M Sabuhi, F Rastgar,
Volume 13, Issue 48 (7-2009)
Abstract
In the present study, grey fuzzy programming model was used for determination of cropping pattern in central part of Quchan city. The needed data was collected from Almachigh Research Center for the year 2008. Result showed that, current cultivated area of irrigated wheat, irrigated barley and alfalfa is more than and rain-fed barley is less than the represented interval upper and lower limits, respectively. Rain-fed wheat and sugar beet was within the represented intervals. Furthermore, the grey degree of solution set from grey programming was decreased about 48 percent by applying grey fuzzy programming approach. According to the findings, it is recommended that cultivated area is decreased for irrigated wheat, irrigated barley and alfalfa and increased for the rain-fed barley.
Sh Mohammad Nejad Kiasari, M Safaee, Sh Nourozi, H Ahmadian, A Mataji,
Volume 13, Issue 48 (7-2009)
Abstract
Determination of suitable species is the most important factor in success of forestation in unfavorable conditions. One of the least costly and the shortest ways for introduction of adaptable species in an area is recognition of the plants that grow naturally. The objective in this study was to find out the effects of protection and water spreading operations on the quantitative improvement of Greek Juniper seedlings. In this study, the areas of water spreading station (Research station of Poshtkoh Water spreading) and an area in western section of water spreading station (an area as control) along the Poshtkoh watershed were chosen. The research was performed on counting of Greek Juniper (Juniper excelsa) in each of two areas. The ratio estimation method was used in a randomized systematic design in strips with the width of 50 meters and 200 meters apart for registration of qualitative parameters of Greek Juniper (Juniper excelsa). The total surface of areas was 600 ha and inventory with intensity of 16 percent has been done. This study showed that in spite of the less number of Greek juniper trees per ha in the station (0/104) in relation to the number of Greek juniper trees per hectare out of the station (0/666), the number of the Greek juniper seedlings in the station was eight times (8.34) more than the number of the Greek juniper seedlings out of the station. As to the effect of protection and water spreading operations on natural growth and increase of number of Greek Juniper seedlings in the station, forestation using this species in this area is recommended.
M Hemami, F Hazeri, S.j Khajedin,
Volume 13, Issue 48 (7-2009)
Abstract
Population of Persian gazelle has been declining in recent decades and as a result, this species was added to the IUCN list of threatened species in 2006. However, there is paucity of ecological data about this species within its range. Mooteh Wildlife Refuge is one of the best habitats of Persian gazelle in Iran where one of the biggest populations of this species live. Habitat selection by threatened Persian gazelle was studied in three seasons in Mouteh wildlife refuge. Habitat use was related to plant communities and plant vegetation variables using clearance transect pellet group counts carried out every 45th day. The effects of water resources and disturbance by man and livestock were controlled. Habitat selection was significantly different between seasons and plant communities. Salt bearing clay soils with a high diversity of holophyte plants were mostly used particularly over winter, while Artemisia- Zygophyllum community was avoided in all seasons. Minimal models resulting from multiple regression retained a number of vegetation variables in each season including a negative effect of Tamarix sp. and Alhaji camelorum and a positive effect of Halocnemum strobilaceum and Salsola dendroide in autumn and winter. It is concluded that selection of habitat by Persian gazelle changes by seasons and that salt-bearing soils and Artemisia-Salsola community are the most important habitats for gazelles in Mouteh Wildlife Refuge.
M Alimohamady, A Rezaee, A.m Mirmohamady Meybodi,
Volume 13, Issue 48 (7-2009)
Abstract
This study was conducted in Research Farm of Isfahan University of Technology to evaluate some of the agronomic and physiological traits and grain yield potentials of ten bread wheat cultivars using a split plot design with three replications. Main and sub plot consisted of optimum and stress moisture treatments (irrigation after 70±3 and 130±3 mm evaporation from class A pan) and wheat cultivars, respectively. The results of analysis of variance revealed significant effect of moisture treatments on all traits except 1000-grain weight, harvest index, specific leaf weight, assimilate redistribution and difference of peduncle weights at heading. Significant differences were found among genotypes in the stress condition except for chlorophyll b and chlorophyll a to b ratio. Significant differences were detected among genotypes in optimum moisture condition for all characters, except for chlorophyll b, chlorophyll a to b ratio, harvest index and assimilate redistribution. Grain yields in two moisture conditions had significant positive phenotypic and genetic correlations with harvest index, number of grain/spike, RWC, chlorophyll a and sum of chlorophylls a and b and had significant negative correlation with RWL. Significant positive correlation was observed between peduncle weight at heading stage and difference of peduncle weights at stages heading and maturity with grain yield and RWC in moisture stress condition. The results of path analysis for phenotypic correlation coefficients between grain yield and their corresponding traits in the regression model showed that in stress condition harvest index had the highest direct and positive effect on grain yield and in non stress condition chlorophyll a had the highest direct and positive effect on grain yield. Results of stepwise regression analysis in non stress condition revealed that chlorophyll a, plant height and harvest index explained more than 90% of grain yield variability. Based on stepwise regression analysis in non stress condition, RWL, harvest index and RWC explained 95% of grain yield variability.
M Modares Sanavi, M Amini Dehagh, M Gholamhoseni, M Panj Tan Dost,
Volume 13, Issue 48 (7-2009)
Abstract
In order to study the effect of air and root-zone temperature on yield, yield components, nodulation and nitrogen fixation of three annual medics, an experiment was conducted in controlled environment (growth chamber) at the Faculty of Agriculture, Tarbiat Modares University in 2006. The experiment was performed as a spilt split plot with the layout of completely randomized design with three replications. Air temperature at three levels including 15/10, 20/15 and 25/20ºC day/night, four levels of root-zone temperatures including 5, 10, 15 and 20ºC and three annual medics (Medicago polymorpha, M. radiata and M. rigidula) were randomized to main plot, sub plot and sub sub plot units, respectively. The results showed that there were significant differences among annual medics for dry matter production, yield components and nitrogen fixation. M. rigidula produced more leaves, stems and root dry matter, leaf and stem to root ratio, leaf number and area and forage yield than other annual medics. Also, three annual medics at 25/20ºC day/night air temperature (the highest one) produced more nodulation dry matter (8.85 mg/pot) and nitrogen fixation (7.7 mg/g dry matter) than other temperatures. Plants at the former temperature produced 8 and 2 times more nodulation and nitrogen fixation than 15/10ºC day/night air temperature (the lowest one), respectively. Low root-zone temperature up to 5ºC had severely negative effect on yield and nitrogen fixation in the three studied annual medics. Interaction among annual medics, air and root-zone temperatures showed that M. rigidula was better than other annual medics for yield, nodulation and nitrogen fixation at 25ºC air temperature and 15ºC root-zone temperature . The result showed that M. rigidula had normal growth and development compared with other annual medics at low root-zone temperatures. Thus, M. rigidula may be a better annual medic for cultivation in cold and moderate regions. Therefore, in the zones where soil temperature is lower than 5ºC during the season, cultivation of annual medics is not successful, but in the zones where soil temperature is greater than 10ºC, annual medics have normal growth and produce average yield due to better nitrogen fixation.
Z Taraz, B Dastar,
Volume 13, Issue 48 (7-2009)
Abstract
This experiment was conducted to compare the effects of Roxarsone (Rox) and Bacitracin methylen disalicylat (BMD) on the performance of broiler chicks. A control corn-soybean meal diet without growth promoter was formulated according to NRC (1994) recommendation for starter (0-21d) and grower (22-42d) periods. The control diet was also supplemented with Rox (50 mg/kg diet ) BMD (55 mg/kg diet) as well as the combination of Rox (50 mg/kg diet ) and BMD (55 mg/kg diet) in order to prepare 4 dietary treatments. Five replicate groups of 15 Ross 308 broiler chicks were assigned to each dietary treatment. Data was analyzed in a completely randomized design. Results of experiment indicated that individual supplementing of diet with Rox as well as BMD led to improved body weight gain and feed conversion ratio compared to the basal diet. However, those birds fed diet containing the combination of these two compounds had significantly higher body weight gain and lower feed conversion than other groups ( P<0.05 ). Neither Rox nor BMD had any significant effect on feed intake. Birds fed diets supplemented with Rox or BMD had better carcass composition than those fed Basal diet. Based on the present results, supplementing broilers diets with Rox leads to improved body weight gain and feed conversion ratio in broilers. However, supplementing broiler diets with combination of Rox and BMD has a more positive effect on the performance and carcass composition in broiler chicks.
Malihe Keykhee, M Heydarpor, Farhad Mosavi,
Volume 13, Issue 49 (10-2009)
Abstract
Ripraps are placed around bridge piers to prevent scour and secure the piers from failure. Proper riprap cover is essential to be economical. The present study examines using of riprap for reduction of local scour in piers group and the results are compared with data from riprap on a single pier. The models consist of two and three circular-shaped piers in line with the flow, with the diameter of 0.02 m and pier spacing of twice and four times the pier diameter. Four uniform riprap sizes with the diameters of 2.86, 3.67, 4.38 and 5.18 mm were used to cover the piers. The results showed that the effect of wake vortices formed at the downstream side of piers group was decreased as compared with single pier. The reinforcing and sheltering effects caused 31% decrease in front pier and 60% increase in back pier, respectively, for the length of cover riprap. The reinforcing and sheltering effects were decreased by increasing pier spacing, but the riprap pattern was not affected. In triple piers group, scour depth in the second pier was less than the first pier and in the third pier was less than the first and second piers. In double and triple piers group, the sheltering effect reduced the scour depth (46% and 54%, respectively) in the back pier with respect to the single pier. Reduction of dimensions in scour hole of back pier in triple piers group was 67% with respect to double piers group, which is the result of sheltering effect of first and second piers. The best shape for the riprap was semi-oval. The riprap length in double and triple piers group was reduced by 31% and 37.5%, respectively, as compared with the single pier.
S Mahbob Sharemi, A Forghani, H Ramezanpor,
Volume 13, Issue 49 (10-2009)
Abstract
Surface charge of soils is measured using two different approaches: ion adsorption and potentiometric titration. Most models of surface charge chemistry of soils have been derived from the data obtained by potentiometric titration. The Uehara and Gillmanُs model was used to estimate the surface charges at some soil pH range in three forest soils of Lahidjan region. The selected soils (Typic Udorthent, Typic Hapludalf, Ultic Hapludalf) were formed on three different types of parent rocks. So, the effect of parent rocks on surface charge characteristics was investigated. Soil samples were characterized through their organic carbon, clay percentage, pH in water and 1 M KCl, cation exchange capacity (CEC), point of zero charge of variable charge components (pH0), zero point of net charge(ZPNC) and charge variation. All soils had a significant amount of negative charge at soil pH. A Typic Hapludalf contained the lowest value of pH0 and the largest amount of negative charge at soil pH. The pH0 values were less in the surface than in the subsurface horizons. The ZPNC values were not obtained by the interpretation of charge variation curves and estimated lower than 2.5, which refers to high amount of negative charge in these soils. Differences in negative charge development in a pH range from 3 to 6 were largest for horizons rich in organic carbon and least for those with significant amounts of layer silicate minerals. Data obtained from charge variation curves of the studied soils also showed that the values of AEC were low and below 1 cmol/kg soil.
A Vaezi, H Bahrami, H Sadeghi, M Mahdian,
Volume 13, Issue 49 (10-2009)
Abstract
Proper evaluation of soil erodibility factor is very important in assessment of soil erosion. In this study, soil erodibility factor (K) was assessed in a zone, 900 km2 in area in Hashtrood, located in a semi-arid region in north west of Iran. Soil erodibility factor was measured at the unit plots under natural rainfall events in 36 different lands in the study area from March 2005 to March 2007. Results indicated that the measured soil erodibility factor K is on average 8.77 times lower than the nomograph-based values in the study area. To achieve a new nomograph, correlation between measured soil erodibility and soil physicochemical properties was studied. Based on the results, soil erodibility factor negatively correlated with coarse sand, clay, organic matter, lime, aggregate stability and permeability, while its correlation with very fine sand and silt was positive. Results of principal component analysis of soil properties and multi-regression analysis showed that the soil erodibility factor is significantly (R2 = 0.92, P < 0.001) related to soil permeability, aggregate stability, lime and coarse sand. A new nomograph with a R2 of 92% was developed based on these properties to easily estimate soil erodibility factor in the study area. The soil erodibility factor can be reliably estimated using the nomograph in all regions with the soil and rain properties similar to those in the study area.
A Sheinidashtegol, H.a Kashkouli, A.a Naseri, S Boromandnasab,
Volume 13, Issue 49 (10-2009)
Abstract
Sugarcane has been cultivated in an extensive area in Khuzestan and irrigated by hydro-flume or siphon and furrow. In a field experiment during 2005-6 at Amir Kabir Agro-Industry, Khuzestan, the effect of every other-furrow irrigation method was studied on sugarcane in regard to irrigation water volume, water use efficiency and quality and quantity of sugarcane. The experiment was conducted in a completely randomized design with three irrigation treatments, including conventional method (blank), variable every other furrow(alternative furrow) and fixed every other furrow. This experiment was conducted by cv. Cp69-1062 sugarcane. The results showed that water use efficiency rates were 0.41, 0.58 and 0.7 kg/m3 for conventional, fixing furrow and alternative, respectively. However, water use efficiency rates were not significantly different in treatments. It had minimum amount of water use efficiency in every other furrow treatments. Maximum water use efficiency, quality and quantity of sugarcane were obtained every other irrigation. Maximum irrigation water was used in conventional treatment and resulted in minimum irrigation, quality sugarcane and water use efficiency. It produced 14.5 ton/ha sugar for 20604 m3/ha application of irrigation. Sugarcane quality and quantity characteristics in variable treatments, except for length number per hectare, were not significant.
N Nourmahnad, M Emamzadei, B Ghorbani, A.r Mohamdkhani,
Volume 13, Issue 50 (1-2010)
Abstract
Water scarcity causes production losses in arid and semi arid regions. In this condition, deficit irrigation is one of the most important methods to minimize effects of water shortage. This research was conducted to evaluate the effects of two kinds of irrigation management (deficit irrigation and partial rootzone drying technique) on some of physiological and phenological characteristics and water use efficiency of tomato. The experiment was carried out in a completely randomized design with five treatments and four replications. The treatments consisted of DI75 and DI50 (supplying 75% and 50% water requirement) applied to the whole root system, PRD75 and PRD50 (supplying 75% and 50% water requirement) which was applied to one side of the root system, and alternated in every irrigation, and FI treatment, which supplied 100% water requirement, and was considered as control. The results showed that the highest water use efficiency was observed in PRD75 (6.28 kg/m3) and the lowest in DI50 (1.98 kg/m3). Water use efficiency was reduced 67% in DI50 and increased 4.6% in PRD75, as compared with full irrigation. Furthermore, plant water state showed that relative water content was higher in PRD treatments than DI treatments. The analysis of variance indicated that there was a significant difference in leaf diameter stomata among treatments at 5% level .The higher level of water increased stomata diameter. The opening of stomata in FI and DI treatments was higher than PRD treatments. FI had the highest numbers of stomata per unit of leaf area and PRD50 had the lowest (10509.04 and 6904.4, respectively). There was no difference among treatments in phenological characteristics in terms of growing degree-day to fruit yield and growing-degree day to harvesting.
H Tabari, S Marofi, H Zare Abiane, R Amiri Chayjan, M Sharifi, A.m Akhondali,
Volume 13, Issue 50 (1-2010)
Abstract
In mountainous basins, snow water equivalent is usually used to evaluate water resources related to snow. In this research, based on the observed data, the snow depth and its water equivalent was studied through application of non-linear regression, artificial neural network as well as optimization of network's parameters with genetic algorithm. To this end, the estimated values by artificial neural network, neural network-genetic algorithm combined method and regression method were compared with the observed data. The field measurement were carried out in the Samsami basin in February 2006. Correlation coefficient (r) mean square error (MSE) and mean absolute error (MAE) were used to evaluate efficiency of the various models of artificial neural networks and nonlinear regression models. The results showed that artificial neural network and genetic algorithm combined methods were suitable to estimate snow water equivalent. In general, among the methods used, neural network-genetic algorithm combined method presented the best result (r= 0.84, MSE= 0.041 and MAE= 0.051). Of the parameters considered, elevation from sea level is the most important and effective to estimate snow water equivalent.
A Rahimi Khob, M Behbahani, M Jamshidi,
Volume 13, Issue 50 (1-2010)
Abstract
Daily solar radiation intercepted at the earth’s surface is an input required for water resources, environmental and agricultural studies. However, the measurement of this parameter can only be done in a few places. This has led researchers to develop a number of methods for estimating solar radiation based on frequently available meteorological records such as hours of sunshine or air temperature. In this study two empirical Angestrom and Hargreaves- Samani models, which are respectively based on air temperature and sunshine duration were calibrated and evaluated for estimating solar radiation in southeast of Tehran, Iran. Also, two neural networks models were presented using similar inputs and above-mentioned empirical models. The results showed that the both empirical and neural network models provided closer agreement with the measured values, but the models based on sunshine hours gave better estimates than the models based on air temperature. The neural network model based on sunshine hours with a R2 of 0.97 and a RMSE of 1.34 MJ m-2 d-1 provided the best results
A.h Khoshgoftarmanesh , A Sanaei Ostovar ,
Volume 13, Issue 50 (1-2010)
Abstract
The objective of this study was to evaluate the possibility of using treated industrial by-products as a zinc (Zn) source and compare their Zn availability and efficiency to ZnSO4. A greenhouse factorial experiment in a completely randomized block design was conducted with corn (Zea mays L.) in triplicates. Treatments included three Zn sources (ZnSO4, IUT-UT in size of < 1 mm and IUT-UT in size of 2-3 mm) at three rates (0, 20 and 40 kg ha-1). The results showed that Zn application both in the form of ZnSO4 and treated industrial by-products significantly (P < 0.05) increased the growth and shoot dry matter yield of corn. Shoot dry matter weight of corn in pots that had received IUTUT was higher compared to those that had received ZnSO4. The highest shoot dry matter weight was produced at the IUT-UT treatment in size of < 1 mm. Increased fertilizer rate significantly (P < 0.05) enhanced shoot and root Zn concentration. However, this increase was higher in ZnSO4 treatment as compared to the IUT-UT treatments. Application of the IUT-UT caused a significant increase in shoot Fe concentration of corn. Shoot and root Cd concentration in all experimental treatments was less than 0.02 mg kg-1. The results showed that IUT-UT can be used as a slow-release Zn fertilizer with low impurity.
B Atarodi , M Naderi Khorasgani,
Volume 13, Issue 50 (1-2010)
Abstract
Sorghum (Sorghum bicolor L. Var. Speedfeed) is a major forage crop in Birjand Region, and phosphorus (P) plays an important role in its nutritional value. During a field campaign, eighty soil samples from the region were collected and analyzed. Among them, 24 samples varying in physico-chemical properties and available P were selected. Five extractants were used for measuring sorghum available P as follows: 1) 0.5 M NaHCO3, pH=8.5, shaken for 30 minutes (Olsen's method), 2) 0.5 M NaHCO3, pH=8.5, shaken for 16 hours (Colwel's method), 3) 0.0025 M Na2-EDTA, pH=7 (EDTA method), 4) 1 M NH4HCO3, 0.005 N DTPA (Soltanpour and Schwab's method), and 5) Water (Paauw's method). A greenhouse experiment using a completely randomized design was carried out with 24 soil samples, two treatments of 0 and 90 mg P/kg soil and three replicates. Results indicated that all five extractants are suitable for prediction of sorghum available phosphorus, but Olson and Paauw's methods are preferable. The results also show ed that the critical levels of soil phosphorus for sorghum by Olsen, Colwel, EDTA, Soltanpour and Schwab and Paauw methods are 17, 24, 14, 7 and 2.5 mg P/kg soil, respectively. Statistical analysis indicated that soil pH, clay percentage and organic carbon significantly affected sorghum available phosphorus.
M. Karimi Kakhaki , A. Sepehri,
Volume 13, Issue 50 (1-2010)
Abstract
In order to study the effect of deficit irrigation at reproductive growth stages on water use efficiency and drought tolerance of four sunflower cultivars, including Azargol, Allstar, Alison and Euroflor, an experiment was conducted during 2007 growing season at experimental field of Agricultural Faculty of Bu-Ali Sina University, Hamadan, Iran. The experiment was a split plot based on randomized complete block design with three replications. The irrigation levels included full irrigation, deficit irrigation at heading, deficit irrigation at flowering, deficit irrigation at seed filling, deficit irrigation at heading and seed filling and deficit irrigation at flowering and seed filling stages. The biological and economic yield (BY and EY), harvest index (HI), water used, water use efficiency (WUE) and water stress indexes were measured. The results indicated that the highest BY (11681.7 kg.ha-1), EY (4854.0 kg.ha-1) and HI (42%) were obtained from full irrigation treatment. The lowest negative effects in cultivars belonged to deficit irrigation at seed filling stage. Euroflor obtained the highest of these parameters with 10127.1 Kg.ha-1, 4081.5 Kg.ha-1 and 40% respectively. Highest WUE was related to twice cutoff of irrigation in flowering and seed formation stages and then without irrigation in seed formation stage by 1.09 and 0.96 Kg.m-3. Allstar and then Euroflor had highest WUE among sunflower cultivars by 1.01 and 0.94 Kg.m-3 respectively. Results also indicated that Euroflor was a tolerant cultivar and STI (Stress Tolerant Index) and GMP (Geometric Mean Productivity) were acceptable indexes for selection. Finally, deficit irrigation at seed formation stage had the lowest negative effect on yield and HI with suitable WUE. In addition, Euroflor showed the highest yield, drought tolerance and HI with suitable WUE.
H.a Alizadeh , F Abbasi , A Liaghat ,
Volume 14, Issue 51 (4-2010)
Abstract
The application of N fertilizers with surface irrigation stream (surface N fertigation( is a key approach for fertilizer management. The main objective of this study was to investigate furrow fertigation management effects on distribution uniformity and runoff losses of nitrate in field scale. A field corn experiment was carried out with a complete randomized block design having 12 experiments. The field experiments were carried out in free draining furrows having 165 m length and 0.006 m/m slope in Karaj. Required urea fertilizer was applied in four stages: before planting, in seven leaves stage, shooting stage and earring stage. The first stage was accomplished by traditional method and other stages were applied with irrigation water (fertigation). Fertigation timing was respectively 60, 35, and 20 min in the three fertigation stages. Results showed that distribution uniformity of water and fertilizer of low half (DULH) provided high values for all experiments. DULH ranged between 88.0 to 99.0% and 89.7 to 96.0%, respectively for water and fertilizer. Also, distribution uniformity of low quarter (DULQ) ranged between 86.0 to 98.2% and 85.7 to 91.5%, respectively for water and fertilizer. Nitrate losses through surface runoff ranged between 5.7 to 42.0%. Duncan test results for comparison between different experiments showed that there was significant difference (p=0.95) between fertilizer losses at the level of fertilizer injection time of 60 and 35 minutes, but there was no significant difference between levels of 35 and 20 minutes.
M. Boyerahmadi, F. Raiesi , J. Mohammadi,
Volume 14, Issue 51 (4-2010)
Abstract
Similar to plants, soil salinity may reduce microbial growth and activities in different ways. The aim of this study was to determine the effects of different levels of salinity on some microbial indices in the presence and absence of plant's living roots. In this study, five levels of salinity using NaCl, CaCl2, MgCl2 and KCl and three soil media (soil with no plant, soil cultivated with wheat and clover) replicated three times consisted our factorial experiment arranged in a completely randomized design. Results show that salinity caused a significant reduction in accumulated microbial respiration, microbial biomass carbon, substrate-induced respiration, and carbon availability index in uncultivated soil and in the soils planted with clover and wheat. Results also show that salinity caused a significant increase in metabolic quotient (qCO2) in uncultivated soil, and soils planted with clover and wheat. Microbial activity of cultivated soils at high salinity levels was almost similar to that of the uncultivated soils. We observed a small difference in soil microbial activity among the three media at high salinity levels, indicating the role of indirect effects of salinity might be less important with increasing salinity levels. We also found out that at low salinity levels, the available carbon was not a limiting factor for soil microflora, while at high salinity levels the activity of soil microbes might be carbon-limited. The lower values of qCO2 in cultivated soils compared with the uncultivated soil support the positive influence of root and its exudates on soil microbial activity in saline soils. The existence of plants in saline environments may help in alleviating the detrimental influence of low to medium salinity on most soil microbial activities, likely via the added root exudates and root turnover.
Sh. Kiani, Gh. Zadeh Dabagh, M.j Malakouti, A. Alizadeh ,
Volume 14, Issue 51 (4-2010)
Abstract
Gray mold, caused by Botrytis cinerea, is a serious disease of cut rose flowers (Rosa hybrida L.) in Iran. In order to elucidate the effects of different potassium and calcium levels in nutrient solution on susceptibility of cut rose flowers to gray mold, this experiment was carried out as factorial design in a randomized complete block with four replications at Safi Abad Agricultural Research center in 2008 for one year. In this experiment, rose plants were grown and subjected to three levels of potassium (1.0, 5.0 and 10.0 mM) in combination with two levels of calcium (1.6 and 4.8 mM) under hydroponic condition. Rose flowers from two consecutive harvesting periods were sprayed with the conidial suspension (104 spore/ml) of B. cinerea isolate. At the end of experiment the disease severity was recorded and analyzed. The results indicated that application of 10.0 mM K in the nutrient solution led to increasing rose disease severity to gray mold (30.4 % day-1) compared to 1.0 mM (24.8 % day-1) and 5.0 mM (26.2 % day-1) of K levels (P< 0.01). The increased susceptibility was associated with a decreased concentration of Ca in the rose petals. Correlation analysis revealed that susceptibility of rose flowers to gray mold significantly increased with K to sum cations ratio in the nutrient solution (r = 0.94*). The increase of Ca supply from 1.6 to 4.8 mM resulted in decline of disease severity from 29.6 to 24.6 % day-1 (P< 0.01). Therefore, balanced application of potassium and calcium (5.0 and 4.8 mM, respectively) is recommendable for preventing antagonistic effects between them and reducing of rose gray mold intensity under hydroponic conditions.
Afkhami, Dastorani, Malekinejad , Mobin,
Volume 14, Issue 51 (4-2010)
Abstract
Drought is a natural feature of the climate condition, and its recurrence is inevitable. The main purpose of this research is to evaluate the effects of climatic factors on prediction of drought in different areas of Yazd based on artificial neural networks technique. In most of the meteorological stations located in Yazd area, precipitation is the only measured factor while generally in synoptic meteorological stations in addition to precipitation some other variables including maximum and mean temperature, relative humidity, wind speed, dominant wind direction and the amount of evaporation are also available. In this research it was tried to evaluate the role of the type and number of meteorological factor (as inputs of ANN model) on accuracy of ANN based drought prediction. Research area is a part of Yazd province containing only one synoptic and 13 non-synoptic meteorological stations. Three-year moving average of monthly precipitation was the main input of the models in all stations. The type of ANN used in this study was time lag recurrent network (TLRN), a dynamic architecture which was selected by evaluation of different types of ANN in this research. What was predicted is the three-year moving average of monthly precipitation of the next year, which is the main factor to evaluate drought condition one year before it occurs. For the Yazd synoptic meteorological station, several combinations of input variables was evaluated and tested to find the most relevant type of input variables for prediction of drought. However, for other 13 stations precipitation data was the only variable to use in ANN models for this purpose. Results in all stations were satisfactory, even where only one input (precipitation) was used to the models, although the level prediction accuracy was different from station to station. Result taken from this research, indicates high flexibility of ANN to cope with poor data condition where it is difficult to get acceptable results by most of the methods.
