Showing 84 results for Spi
N. R. Jalali, M. Homaee, S. Kh. Mirnia,
Volume 12, Issue 44 (7-2008)
Abstract
Canola (Brassica napus L.) in response to salinity represents various resistances with respect to its phonologic stages. Most plants such as Canola are resistant at germination stage. However, at seedling or earlier growth stages, plants become more sensitive to salinity but their tolerance increases with age. Salt tolerance of various plants has been extensively studied however, the results have either been qualitative or expressed as average values over root zone salinity for the whole growth season. Thus, developing appropriate models for quantitative characterization of plant response to salinity at different growth stages is essential. Canola which is considered as high economic value plant was selected for this study. Two productive stages for canola are recognized as flowering and ripening. To determine the effect of salinity on canola at vegetative growth stages, a greenhouse experiment was conducted on a natural saline loamy sand soil, using salinity treatment including one non-saline water (tap water) and 8 saline waters of 3 to 17 dS.m-1. The canola plants were irrigated with tap water before the desired stage and then salinity treatments were imposed. The Maas and Hoffman (1977), van Genuchten and Hoffman (1984), Dirksen et al., (1993), and Homaee et al., (2002b) models were used to predict relative transpiration (Ta/Tp ) and relative yield ( Y/Ym) as a function of soil salinity. The maximum error (ME), root mean square error (RMSE), coefficient of determination (CD), modeling efficiency (EF) and coefficient of residual mass (CRM) statistics were calculated to compare the models and their efficiencies. The results indicated that the van Genuchten and Hoffman (1984) model provides best prediction at flowering stage. However the Homaee et al. (2002b) model offers better prediction at ripening growth stage.
H Faghih, M Kholghi, S Kochekzadeh,
Volume 12, Issue 46 (1-2009)
Abstract
Overtopping is one of the main factors responsible for dam failure. To avoid overtopping, dam is equipped with one or some spillways to release the water impounded in the reservoir. The number and size of these spillways are determined on the basis of design flood. Determination of design flood of dam spillway can be formulated as a multiobjective risk problem. This problem can be solved by Quantitative Risk Analysis Methods. Here, four economical design methods which are based on risk analysis including, United States National Research Council (NRC), US Civil Engineering, Unit Curve and Partitioned Multiobjective Risk (PMR) were studied. In order to compare these methods, Risk Analysis was performed for re-determining design flood of Pishin Dam Spillway. This Dam has been constructed on the Sarbaz River. Owing to the fact that the integrals of the expected damage relations in the two methods, i.e., Civil Engineering, and Partitioned Multiobjective Risk are analytically unsolvable, Romberg numerical integration technique and Excel software were utilized for the related calculations and drawing graphs. Also, in order to select suitable distribution, the flood analysis was done using Smada software. The findings of the study indicated that design flood determined by the three methods, i.e., Civil Engineering, National Research Council and Unit Curve was almost the same, and that the amount of flood was less than the 10,000-year-old flood while design flood determined by Partitioned Multiobjective Risk Method, was larger than the 10,000- year-old flood.
Z Maryanji, A Sabziparvar, F Tafazoli, H Zare Abianeh, H Banzhad, M Ghafouri, M Mousavi,
Volume 12, Issue 46 (1-2009)
Abstract
Under different climatic conditions of Iran, the evaluation of evapotranspiration (ETo) models sensitivity to meteorological parameters, prior to introducing the superior performance model, seems quite necessary. Using a 35-year (1971-2005) climatological observations in Hamedan, this study compares the sensitivity of different commonly used evapotranspiration models to different meteorological parameters within the IPCC recommended variability range of 10 to 20% during the growing season (April-October). The radiation and temperature-based ETo models include: Penman-Monteith -FAO56 [PMF56], Jensen-Haise [JH1,2], Humid Turc [TH], Arid (semi) arid Turc [TA], Makkink [MK], Hansen [HN], and Hargreaves-Samani [HS]. Results indicate that all the above-mentioned ETo models show the highest sensitivity to radiation and temperature parameters. This implies that special care is required when we apply model-generated radiation and albedo parameters in such ETo models. It is predicted that by 2050, as a result of global warming, the cold semi-arid climates of Iran will cause an average evapotranspiration rise of about 8.5% in crop reference during the growing season.
Y Hosseini, M Homaee, N Karimian, S Saadat,
Volume 12, Issue 46 (1-2009)
Abstract
Modeling plant response to salinity and nitrogen deficiency is very important for estimating optimum yield in arid and semi-arid regions. For this purpose, the models of Leibig-Sprengel (LS) and Mitscherlich-Baule (MB) originally proposed to explain plant response to nutrients only were modified to evaluate plant yield response to combined nitrogen and salinity stress conditions. Afterwards, in order to model canola (Brassica napus L.) response to combined salinity and nitrogen stress, an experiment was designed with different nitrogen and salinity levels. The water salinity treatments consisted of non-saline water, 3, 6, 9 and 12 dS m-1. The nitrogen treatments were 0, 75, 150 and 300 mg kg soil-1 added as ammonium nitrate. The results indicated that both modified models can satisfactorily predict canola yield. However, the modified MB model (R2=0.94) provided better estimation than the modified LS model (R2=0.87). The calculated statistics including Maximum Error, Root Mean Square Error, Modeling Efficiency, Coefficient of Determination and Coefficient of Residual Mass for the modified models indicated that the estimated relative grain yield for soil nitrogen, salinity and each rate of soil nitrogen in salinity levels by modified MB model compared with those by modified LS model is closer to the measured relative yield. Therefore, the use of modified MB model for estimating canola relative grain yield in salinity and nitrogen stresses is recommended. Using modified LS model showed that the salinity threshold value changes with the applied nitrogen. In this case, by application of each 75 mgN kg-1 soil, the salinity threshold value decreased 4 dS m-1 in saline conditions. Application of nitrogen decreased chloride concentration in grains under saline conditions. Nitrogen uptake also augmented with increasing canola transpiration, because nitrogen was carried over from soil to the uptake sites mainly by mass flow.
M Mahbod, Alireza Sepaskhah, Marzih Monfared,
Volume 13, Issue 49 (10-2009)
Abstract
Optimum management of water use in agriculture results in higher cultivated areas or enhances the share of water for municipal and industrial uses leading to economic development of a country. One of the effective methods in optimum water management is irrigation scheduling by using models which simulate water content in soils. In this study, a previously prepared model for irrigation water scheduling was modified to calculate daily effective rain, soil water content and deficiency. The model was applied for winter wheat field in Bajgah area using 13 years of local meteorological data. Furthermore, the effect of water storage in the soil profile on the amount and frequency of irrigation was examined. This model was written in Visual Basic.Net programming software. The model was run under two assumptions: 1) the effective rain compensates water deficiency of soil down to daily root depth and the excess water is assumed as deep percolation (case I) 2) the effective rain compensates water deficiency of soil down to maximum root depth and the excess water is assumed as deep percolation (case II). The results show that the amount and the frequency of irrigation in case 2 is less than case 1. Average amount and number of irrigation events decreased from 706.8 (mm) and 8 in case I to 569.2 and 6.4 in case II. The average relative percentage of effective rain increased from 45.2 % in case I to 76.9% in case II. The effective rain is 108.9 mm and the amount and number of irrigation events is 9 and 757.7 mm, respectively in case I (at probability level of 80%). The effective rain is 236.7 mm and the amount and number of irrigation events is 636.9 mm and 7.2, respectively in case II (at probability level of 50%). The effective rain is 165.6 mm and the amount and number of irrigation events is 712.6 mm 8, respectively in case I. The effective rain is 292.1 mm and the amount and number of irrigation events is 545.1 and 6, respectively in case II.
B Bakhtiari, A.m Liaghat, A Khalili, M.j Kjanjani,
Volume 13, Issue 50 (1-2010)
Abstract
In this study, the Penman-Monteith methods proposed by the Food and Agriculture Organization (FAO-56) and American Society of Civil Engineers (ASCE) were used for hourly ETo estimation under the semiarid climate of Kerman, Iran. Hourly ETo estimations obtained from the proposed methods were compared with measured ETo values by using a large weighing electronic lysimeter during April to September 2005 (totally 3352 hourly ETo data cases). Simple linear regression and statistical factors such as root mean square error and index of agreement were used for estimated and observed value comparison. The average of measured and estimated hourly ETo values using these methods for integrated data were 0.28 and 0.23 mm hr-1, respectively, which means that average estimated ETo values were approximately 21 percent less than the measured ETo values. This analysis was also performed for hourly data of each month during the study period. The results showed that FAO-56 Penman-Monteith underestimated ETo values by 18.4, 19.3, 26.3, 20.4, 21.4 and 22.1 percent for April to September, respectively, when compared with the measured values. Similarly, the ASCE Penman-Monteith underestimated ETo values by 17, 19.6, 18.4, 18.2, 19.7 and 20.9 percent for the same period, respectively, when compared with the lysimetric data. Finally, a set of regression equation for transformation of the estimated hourly data into the measured hourly ETo values has been presented for each month.
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.
A.a. Besalatpour , M.a. Hajabbasi, V. Dorostkar , Gh. Torabi,
Volume 14, Issue 53 (10-2010)
Abstract
Presence of petroleum contaminants in soil may be toxic to human and organisms and act as a source of ground water contamination hence, remediation of these compounds from environment is vital. In this study, first the feasibility of remediation of two petroleum-contaminated soil samples around Tehran Oil Refinery (oil refinery landfill and agricultural soils) was assessed using landfarming technique during a four month experimental period. The elimination of total petroleum hydrocarbons (TPHs) from soils treated through landfarming technique was then investigated in the rhizosphere of agropyron and fescue. The results showed that microbial respiration increased due to landfarming processes in both soils. Urease activity in the landfarming treatment for agricultural soil was 21, 45, 26, and 23% higher than the control at the end of first to the 4th months of experiment, respectively. However, no significant differences were observed between the landfarming and control treatments for landfill soil at the end of experiment. Furthermore, about 50 and 57% reduction in TPH-concentration was observed in the landfarming treatment for landfill and agricultural soils at the end of experiment, respectively. In the phytoremediation study, presence of TPHs in both landfarming and control treatments reduced dry matter yield of the studied plants. Urease activity in the rhizosphere of fescue and agropyron was higher than in the unplanted soil. Degradation of petroleum-compounds in the landfill soil under landfarming treatment was more than 20 and 40% in the presence of fescue and agropyron, respectively. The influence of agropyron on TPH-removal from agricultural soil under the landfarming treatment was also higher than fescue.
E. Shayegh, S. Soltani ,
Volume 15, Issue 57 (10-2011)
Abstract
In this research, 5 percent of normal Precipitation Index (PNPI),Deciles of Precipitation(DPI),Rainfall Anomaly Index (RAI), Bahlme & Mooley Drought Index (BMDI) and standardized Precipitation Index (SPI) were used in order to investigate drought in Yazd synoptic station and 31 non synoptic stations all around this province. For this purpose, the present statistical errors were reconstructed via correlation between the stations, after raining data collection from the considered stations. Then, calculation of PNPI, DPI, RAI, BMDI and SPI indexes were calculated on monthly and annual scales. Situation of drought was determined based on the obtained values from calculation of each index according to tables related to the considered indexes in different classes of drought during the statistical period. Then indexes were compared to each other, considering drought given situation for each station. The difference and similarity of each index with other 4 indexes were calculated and investigated. Also after determination of drought situation in each station, given percentage of drought different situations via each Index was determined on annual scales, in 33 study stations. After passing the above mentioned stages, it was found that there was the highest percentage value of similarity between the two indexes RAI & DPI, as both indexes indicated similar situation of hard drought in the stations. These two indexes are considered most efficient to investigate aerology drought. But considering that static indexes are faced with problem on monthly scales and in stations located in drought regions, it is recommended to use SPI & BMDI dynamic indexes whose similarity percentages are acceptable.
T. Rahimi, A. Ronaghi,
Volume 16, Issue 59 (4-2012)
Abstract
Contamination of agricultural soils by heavy metals is a serious threat from both agricultural and environmental standpoints. Among heavy metals, cadmium (Cd) toxicity for humans and plants is of great concern due to its high mobility and phytoavailability in soil even at low concentrations. Opposite to Cd, Phosphorus (P) is an essential nutrient for plant growth. A greenhouse experiment was carried out in a completely randomized design to examine the influence of Cd, P and their interaction on the growth and chemical composition of spinach grown on a calcareous soil. Treatments consisted of four Cd levels (5, 10, 20 and 40 mg/kg soil as cadmium sulfate) and four P levels (0, 20, 40 and 80 mg/kg soil as mono-calcium phosphate) in three replicates. The results indicated that 40 mg Cd significantly decreased spinach dry weight by 47% but P application decreased detrimental effect of Cd on spinach dry weight. Also, phosphorus application significantly decreased Cd concentration in spinach aerial parts by 78%. Increasing Cd levels increased concentration of this element in spinach shoots. Addition of 40 mg Cd decreased P concentration by 21.5% in aerial parts. Zinc (Zn), manganese (Mn), calcium (Ca), and nitrogen (N) concentration significantly decreased with P application but increased concentration of sodium (Na). Cadmium application decreased Zn concentration but increased Ca, Na and N concentrations in spinach. Our tentative conclusion is that P application in P-deficient soils is probably effective in decreasing Cd concentration and the detrimental effect of Cd on spinach growth, indicating a negative interaction between these elements. Prior to any fertilizer recommendation, the results of this experiment should be verified under field conditions
H. Dehghan-Menshadi, M. A. Bahmanyar, S. Salek Gilani, A. Lakzian,
Volume 16, Issue 60 (7-2012)
Abstract
Biological indicators are considered soil quality elements, due to their dependence on soil organisms. In order to investigate The effect of compost and vermicompost enriched by chemical fertilizers and manure on soil organic carbon, microbial respiration, and enzymes activity in basil plant's rhizosphere, a field experiment was conducted as a split-plot design with randomized complete blocks and three replications in 2006. The main plot involved six levels of fertilizer including: 20 and 40 tons of compost enriched, 20 and 40 tons of vermicompost enriched per hectare, chemical fertilizer and control without fertilizer and sub-plot, and period of application (two, three and four years). The results showed that application of compost and vermicompost at all levels increased soil organic carbon (OC) and soil microbial respiration, microbial biomass and urease activity compared to the controls (p<0.05), but increasing trend among the treatments was not similar. The maximum amounts of OC, soil microbial respiration and enzyme activity were observed in 40 tons of vermicompost enriched with chemical fertilizer ha-1 with four years of application. In high levels of compost application, the urease activity was decreased.
M. A. Moradi, A. Rahimikhoob,
Volume 16, Issue 62 (3-2013)
Abstract
Reference evapotranspiration (ET0) is a necessary parameter for calculating crop water requirements and irrigation scheduling. In this study, a method was presented as ET0 is estimated with NOAA satellite imagery in the irrigation network. In this method, a pixel from a set of pixels within the irrigation network was chosen with the highest vegetation index, and its surface temperature (Ts) with extraterrestrial radiation parameter (Ra) was used as inputs of the model. The M5 model tree for converting Ta and Ra to ET0 was used as input variables. In this research, Gazvin irrigated area was selected as a case study. A total of 231 images of NOAA satellite related to irrigation season of the study area were used. The results obtained by the M5 model were compared with the Penman–Monteith results, and error values were found within acceptable limits. The coefficient of determination (R2), percentage root mean square error (PRMSE) and the percentage mean bias error (PMBE) were found to be 0.81, 8.5% and 2.5%, respectively, for the testing data set.
M. Toozandehjani, M. Kashefipour,
Volume 16, Issue 62 (3-2013)
Abstract
One of the usual ways to dissipate excess energy in the dam's downstream is hydraulic jump. Hydraulic jump is a rapidly varied flow, in which the flow conditions change from supercritical to sub-critical with a large amount of energy loss. In this research, a combination of two water jets in the form of overflow dam and underflow through a slot on the body of an ogee dam with the USBR standard was established in order to decrease the length and sequent depth in a hydraulic jump. In these experiments, the underflow from the slot was designed with three out passages of 0, 45, and 90 degrees in respect horizontal line. Six different discharge ratios were used for each slot and the effect of each experiment conditions on decreasing of the length and sequent depth of hydraulic jump was investigated. The results showed that the confluence of two jets with 45 degrees from the slot had the maximum effect on the reducing of the length of hydraulic jump and sequent depth, and when 26 percent of the total discharge passed through the slot as underflow, it caused the length of hydraulic jump to be reduced by 50 percent in comparison with the classic jump. This slot not only decreases the length and sequent depth of hydraulic jump but also the sediment behind the dam can be evacuated through it. Moreover, it increases the discharge coefficient.
S. Rahimi Alashti, M. A. Bahmanyar, Z. Ahmad Abadi,
Volume 17, Issue 63 (6-2013)
Abstract
In order to investigate the effects of municipal solid waste enriched with mineral fertilizers on some soil physical properties and lead (Pb) and chromium (Cr) concentration in plant organs of spinach, a field experiment was carried out in a factorial arrangement based on the randomized complete block design with three replications in 2008. The main plot included four levels of fertilizer, control without fertilizer, 20 tons of multiple solid waste + 50% chemical fertilizers and 40 tons of multiple solid waste + 50% chemical fertilizers per hectare and sub-plot consisted of a period of application in 3 levels of time (one, two and three years). The results showed that application of enriched municipal compost increased field capacity, soil porosity and moisture holding capacity, but particle and bulk density of soil decreased compared to the control. Also, the physical parameters in the two levels of emriched waste compost were higher than chemical fertilizer treatment. On the other hand, using for three-years the urban waste compost enriched fertilizer at all levels increased significantly (p 0.05) lead and chromium concentrations in spinach. The Pb and Cr accumulated in roots and shoots of spinach in urban using 40 tons of waste compost per hectare with 50 percent of chemical fertilizer for a period of three years and showed a significant increase. The amounts of fertilizer in all three levels were higher than the root element shoot.
L. Divband, S. Boroomand Nasab, M. Behzad, J. Abedi Koupai,
Volume 17, Issue 65 (12-2013)
Abstract
Heavy metals in water resources are one of the most important environmental problems in most of countries. Up to now, various methods for removing these metals including using low price materials have been used. In this study, two new absorbents (zizyphus spinachristi leaf and its fly ash) were studied for adsorption of cadmium from aqueous solutions using batch experiments. The effect of contact time, pH, and amount of adsorbent on adsorption efficiency was evaluated and the best kinetic and isotherm model was determined. Results showed that optimal absorption of pH was 5 and 6 for zizyphus spinachristi leaf and its fly ash, respectively. The equilibrium time was 45 min for zizyphus spinachristi leaf and 30 min for ash. Adsorption efficiency was increased by increasing the adsorbent dose. By comparing the parameters of isotherm models, it was observed that the cadmium adsorption capacity of fly ash (4.27 mg/gr) was higher than that of zizyphus spinachristi (3.91 mg/gr).
S. Besharat, V. Rezaverdinejad, H. Ahmadi, H. Abghari,
Volume 17, Issue 65 (12-2013)
Abstract
Different root water uptake models have recently been used. In this article, we use evapotranspiration data and soil water content data obtained from lysimeter measurements and root distribution in soil data obtained from olive tree to evaluate the accuracy of root water uptake models in predicting the soil water content profiles. Depth of lysimeter was 120 cm which was filled with clay-loam. Lysimeter recorded values of input and output of water and accurate value of evapotranspiration was also calculated. Soil water content distribution was measured using a TDR probe in lysimeter during the experiment. Feddes model with the root length density was used to account for the role of root distribution in soil. The flow equations were solved numerically with the measured evapotranspiration data as input, and the predicted soil water content profiles were compared with the measured profiles to evaluate the validity of the root water uptake models. The comparison showed that the average of relative error index for Feddes model was 10 %. Based on the results, about 90% of root uptake in olive tree happened at the depth of 40 centimeter
F. Heydari, A. Rasoulzadeh, A. R. Sepaskhah, A. Asghari, A. Ghavidel,
Volume 17, Issue 65 (12-2013)
Abstract
The objective of this study was to evaluate the effects of crop residues management on soil physical and biological properties. The impacts of residue management on yield of forage corn and barley and soil micro-organisms population were also studied. The results showed that application of crop residues increased soil organic matter (22.2 %), saturated hydraulic conductivity (51.9 %), porosity (3.7 %), mean weight diameter (MWD) of the aggregates (5.4 %), and field capacity (5.8 %) and decreased bulk density (3.7 %) Whereas crop residues burring decreased soil organic matter (31.8 %), saturated hydraulic conductivity (36.6 %), porosity (0.5 %), mean weight diameter (MWD) of the aggregates (5.1 %), and field capacity (4.1 %) and increased soil bulk density (1 %). Soil water characteristic curves showed that the observed differences in soil water retention of application and burning residues treatments were higher at low matric suctions than those at high water matric suction. The results demonstrated that micro-organisms population significantly (P<0.05) decreased in residues burning treatment compared with the residues application treatment. Therefore, based on the results of this study residues' burning is not recommended in Ardabil.
A. Morshedi, M. Naderi, S. H. Tabatabaei, J. Mohammadi,
Volume 17, Issue 66 (2-2014)
Abstract
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.
H. Modabberi, M. Mirlatifi, M. A. Gholami,
Volume 18, Issue 67 (6-2014)
Abstract
Since more than 75% of the rice fields in Iran are located in the Northern provinces i.e. Mazandaran, Guilan, and
Golestan identifying the crop water requirement of rice fields is essential for water resources planning in the Northern
provinces. The objective of this research was to ascertain the crop water requirement of two rice cultivars namely
Hashemi and Khazar in Guilan province during 1389 growing season. Four iron barrels with diameter of 56 cm were
used as lysimeters to grow the cultivars mentioned. According to a simple volume balance approach the crop water use
of the four lysimeters were determined during the growing season. The elements of volume balance approach such as
the depths of drainage, precipitation, and irrigation were recorded daily and the average of 5-day and 10-day periods
were reported. The daily rice crop water use during the growing season was found to range from 2.4 to 6.3 mm/day with
a seasonal crop water use ranging from 430 to 470 mm for Hashemi and Khazar cultivars, respectively. Daily reference
evapotranspiration was computed by the FAO-Penman-Montith equation and accordingly rice crop coefficients were
computed. The crop coefficient of Hashemi variety was found to be 1.1, 1.3, and 1.1 during the initial, mid, and end
growth stages, respectively. In addition, the aforementioned parameters for Khazar variety were 1.2, 1.3, and 1.1.
M. Kiani, M. Gheysari, B. Mostafazadeh-Fard, M. M. Majidi and E. Landi, , , , ,
Volume 18, Issue 67 (6-2014)
Abstract
The purpose of this study was to measure daily and seasonal evapotranspiration and daily crop coefficient of two common varieties of sunflower (Sirna and Euroflor) via drip-tape irrigation system. For this purpose, the sunflower water use was determined by daily monitoring of soil moisture at the depths of 10, 20, 30, 40 and 60 cm, and the crop evapotranspiration (ETC) was measured using volume balance method. According to the equation recommended by FAO, the obtained value of KC for Euroflor and Sirna varieties at the initial stage was 0.32. According to volume balance method, the Euroflor KC value for development, middle, and late stages were found to be 0.75, 1.18 and 0.9 and for Sirna were found to be 0.72, 1.15 and 0.84 respectively. Seasonal amount of evapotranspiration for Euroflor and Sirna varieties was equal to 601 and 575 mm, which was 26 and 30 percent less than seasonal ET0 in Isfahan. The average value of during the sunflower growing season was 0.77, which was greater than that offered by Doorenbose and Pruitt (0.55). As the crop coefficients of two varieties were different during the growing season and they were also different from FAO KC, measuring the actual amount of KC as a function of growing degree days can increase the accuracy of the estimated ETc and help develop the crop models in order to improve the irrigation management.
