Showing 388 results for Water
F. Abbasi, F. Tajik,
Volume 11, Issue 1 (4-2007)
Abstract
Estimation of unsaturated soil hydraulic and solute transport properties by Inverse modeling has thus far been limited mostly to analyses of one-dimensional experiments in the laboratory, often assuming steady-state conditions. This is partly because of the high cost and difficulties in accurately measuring and collecting adequate field-scale data sets, and partly because of difficulties in describing spatial and temporal variability in the soil hydraulic properties. In this study we estimated soil hydraulic and solute transport parameters from several two-dimensional furrow irrigation experiments under transient conditions. Three blocked-end furrow irrigation experiments were carried out, each of the same duration but with different amounts of infiltrating water and solutes resulting from water depths of 6, 10, and 14 cm in the furrows. Two more experiments were carried out with the same amounts of applied water and solute, and hence for different durations, on furrows with water depths of 6 and 10 cm. The saturated hydraulic conductivity (Ks) and solute transport parameters in the physical equilibrium convection-dispersion (CDE) and physical nonequilibrium mobile/ immobile (MIM) transport models were inversely estimated using the Levenberg-Marquardt optimization algorithm in combination with the HYDRUS-2D numerical code. Estimated Ks-values ranged from 0.0389 to 0.0996 cm min-1, with a coefficient of variation of 48%. Estimated immobile water contents (θim) were more or less constant at a relatively low average value of 0.025 cm3 cm-3, whereas the first-order exchange coefficient (ω) varied between 0.10 and 19.52 min-1. The longitudinal dispersivity (DL) ranged from 2.6 to 32.8 cm, and the transverse dispersivity (DT) from 0.03 to 2.20 cm. DL showed some dependency on water level and irrigation/solute application time in the furrows, but no obvious effect was found on Ks and other transport parameters. Agreement between measured and predicted infiltration rates was satisfactory, whereas soil water contents were somewhat overestimated and solute concentrations underestimated. Differences between predicted solute distributions obtained with the CDE and MIM transport models were relatively small. This finding and the value of optimized parameters indicate that observed data were sufficiently well described using the simpler CDE model, and that immobile water did not play a major role in the transport process.
M.j. Seghatoleslami, M. Kafi, I. Majidi, G. Nour-Mohammadi, F. Darvish,
Volume 11, Issue 1 (4-2007)
Abstract
In order to examine the responses of proso millet (Panicum miliaceum) to drought stress at different growth stages, four breeded genotypes and a local one of proso millet were selected and planted in a split-plot design with five irrigation treatments and three replications.This experiment was conducted in two locations, Birjand and Sarbisheh. Irrigation treatments included well - watered, drought stress at vegetative stage, ear emergence stage, seed filling stage and vegetative and seed filling stages which were considered as main- plots. The first five mentioned genotypes were considered as sub-plots. Drought stress. caused a great reduction in grain yield and WUE at ear emergence stage. This reduction represented itself in the number of seed per ear and the weight of seeds, but it didn’t have any effects on the number of ear. At ear emergence stage, the drought stress increased the floret death and loss of weight of seeds which resulted in the reduction in the harvest index of both ear per plant and seed per plant. Comparison of genotypes indicated that since K-C-M.4 had a greater number of ears and K-C-M.9 had heavier seeds that had higher grain yield. These two genotypes had the highest WUE and their harvest indices were relatively higher. Due to the salinity of water and infertility of soil in Birjand, the grain yield was lower compared with Sarbisheh. In summary, it can be said that genotype K-C-M.4 proved to be more suitable for both areas.
M. Sabohi, Gh. Soltani, M. Zibaie,
Volume 11, Issue 1 (4-2007)
Abstract
The objective of this study was to evaluate the strategies for groundwater resources management, including competition groundwater pumping, optimal control in groundwater pumping, groundwater use and tax policy, water users' participation in groundwater pumping control, and cooperation among government and water user associations in Narimany plain located in Khorasan Province. Irrigation water demand of sugar beet growers was estimated for empirical assessment of the strategies. The results indicated that among the strategies, groundwater use and tax policy may lead growers to sustainable use of groundwater resources. Furthermore, the results showed a desirable strategy is affected by cultural, social, and economic characteristics of growers and general prevalent conditions of society. Moreover, each strategy calls for its obligations, for instance, it is necessary to have an efficient taxation system for the proposed strategy. Hence, by internalizing the external cost of groundwater overdraft (that is taxing water users) government can force them to consider the adverse effects of their decisions on other producers.
A. Zahmatkesh, J. Poorreza, A. Abedian, F. Shariatmadari, A. Valipoor, K. Karimzadeh,
Volume 11, Issue 40 (7-2007)
Abstract
The study was conducted to compare the efficiency of diets containing various levels of calcium(0, 1, 2, 3 and 4 percentage) in feeding freshwater crayfish, Astacus leptoductylus. 150 cray fish (10 individuals per tank) with mean weight of about 8-9 gram were stocked in each of 15 tanks, containing 100 L of water. In this research, The results showed that the mean values of some parameters such as weight gain (WG), weight increment rate (WIR), length increment rate (LIR), specific growth rate (SGR), biomass increment (BI), food efficiency rate (FER) and survival rate (SR) of animal fed on different diets were 0.75-1.46gr, 9.8-24.54%, 6.57-15.33% and 0.12-0.29% respectively. However, the diet with high levels of calcium (3-4%) showed the good weight and length increment, but there were no significants difference among these indices using different trial diets. The biomass of crayfish increased with increasing of calcium concentration. So, the highest biomass (11.65gr) of crayfish was observed in the diet containing calcium about 4%. Optimal calcium requirement in the freshwter crayfish was estimated about 3.4% with broken-line regression analysis. The lowest survival rate (30%) was obtained in the diet containing 2% calcium level. There were significant differences among survival rates in various experimental diets (p<0.05). These results indicate that the dietary calcium supplement is nesessary for crayfish. The diets with high levels of calcium had a good efficiency in freshwater crayfish feeding. So it is recommended to use 3-3.5% of calcium in formulated diets for freshwater crayfish
A.m. Mohammadi, S.j. Khajeddin, S.a. Khatoonabadi,
Volume 11, Issue 40 (7-2007)
Abstract
Northern watershed of Kouhrang River with the area of 68437 hectares is located in northwestern Chahar Mahal and Bakhtiary province within 49ْ 54ً to 50ْ 9ً E longitude and 32ْ 83ً to 32ْ 36ً N latitude.Making a balance and equilibrium between the number of ranchers, the rangeland production potential and appropriate flock size in each utilization unit is a necessary task. It is a matter of importance to determine suitable ranch size based on pastoral household but suitable household livelihood as well. The main goal of this study is to determine utilization unit size based on ecologic and socioeconomic factors for each household. Along with detecting the ranch allotments, the range capacity and its productivity potential were studied. Then, based on expenses and the revenues resulting from herdship,(on ranges), the suitable flock size for fulfillment of the household expenses regarding the range utilization periods, the suitable range size per household was determined. 10 vegetation types with 0.91 AUM per hectares grazing capacity were detected in studied area. There are 46 range allotments and some parts of other 6 range allotments in studied area with average area at 1510 hectares. Average pastoral household is 36.8 per unit range allotments. Pastoral households share at rangelands is 41 hectares now. The minimum and suitable ranch area for each pastoral household which can provide annual needs and costs is 520 hectares and 142 animal unit at a mix flock at 3 to 2 ratio of sheep to goat for a 100 – dayes grazing season. The result of this study showed that production potential at each range unit is influenced by flock size, household share on farming lands, and the household numbers on each ranch unit. Ranch unit and the livelihood level, have significant influence at 5% level on suitable ranch size per household.
S. Akhavan, S. F. Mousavi, B. Mostafazadeh-Fard, A. Ghadami Firoz Abadi,
Volume 11, Issue 41 (10-2007)
Abstract
To investigate yield and water use efficiency (WUE) of potato with tape and furrow irrigations, an experiment was performed at Hamadan Agricultural and Natural Resources Research Center (Ekbatan station) in 2004. The experiment was arranged in a split-plot experimental design based on completely randomized block with 3 replications of irrigation water amount as the main factor (75%, 100%, 125% of cumulative evaporation from class A pan) and sub-factor of irrigation method [including tapes in the middle of furrow ridge on soil surface (TD0), tapes in the middle of furrow ridge at the depth of 5 cm (TD5), tapes on the sides of furrow ridge on soil surface (TS0), and furrow irrigation (F)]. The results indicated that yield of potato increased with increasing water use. Regardless of irrigation method, maximum (32.51 ton/ha) and minimum (19.33 ton/ha) yield of potatoes was achieved with 125% and 75% irrigation water treatments, respectively. The lowest yield (21.35 ton/ha) was obtained in furrow irrigation and the highest yield (28.91 ton/ha) belonged to tape irrigation (TD5 treatment). The highest WUE (4.68 kg/m3) belonged to tape irrigation (TD5 treatment) and the lowest WUE (3.32 kg/m3) belonged to furrow irrigation (F). The difference in WUE between 75% and 100% irrigation water treatments was not significant. The highest WUE (4.49 kg/m3) was achieved in treatment 125%. Also, it is more economical to use irrigation water treatment of 125%, as compared with other irrigation water treatments.
A. Majnooni-Heris, Sh. Zand - Parsa, A. R. Sepaskhah, A. A. Kamgar-Haghighi,
Volume 11, Issue 41 (10-2007)
Abstract
Optimal crop water requirement is needed for precise irrigation scheduling. Prediction of crop water requirements is a basic factor to achieve this goal. In this study, maize potential evapotranspiration (ETp) was prediced by maize simulation model (MSM). Then, it was evaluated and validated using experimental field data obtained in Agricultural Research Station of Shiraz University (Bajghah, Fars province) during 2003 and 2004. Comparison of measured volumetric soil water content with predicted values by MSM model in 2003 and 2004 indicated that this subroutine (prediction of maize evapotranspiration) did not need modification. Also, daily potential evapotranspiration of maize was estimated by using Penman-Monteith equation considering single and dual crop coefficients. Comparison between the results of predicted ETp by MSM model, calculated ETp by Penman-Monteith, and measured irrigation water and soil water content indicated that the prediction of ETp by MSM model was satisfactory. Model prediction of seasonal ETp, potential transpiration (Tp) and soil evaporation (E) were 831, 536 and 329 mm, respectively, in 2003, and 832, 518 and 314 mm, respectively, in 2004. The values of ETp, Tp and E calculated by Penman-Monteith method using dual crop coefficients were 693, 489 and 205 mm, respectively, in 2003, and 700, 487 and 213, respectively in 2004. Maximum rate of predicted potential ETp, Tp and E were 11.1, 8.2 and 5.1 mm d-1, respectively in 2003 and 13.0, 9.0 and 4.0 mm d-1, respectively in 2004. The values of calculated seasonal ETp by Penman-Monteith method using single crop coefficient were 615 and 632 mm in 2003, and 2004, respectively. Comparison between the results of predicted ETp by MSM model, calculated ETp by Penman-Monteith equation with single and dual crop coefficients (FAO-56) and measured values of irrigation water and soil water contents of root depth indicated that FAO-56 methods underestimated the ETp.
N. Mirghaffari, H. Shariatmadari,
Volume 11, Issue 41 (10-2007)
Abstract
Concentration of soluble fluoride in groundwater, soil, and some crops in Isfahan region was determined by Ion Selective Electrode (ISE) method. The mean fluoride concentration of water samples in the study area was 0.3 and 0.05 mg L-1 in the spring and summer, respectively. These values are in an acceptable limit for irrigation, whereas for drinking water, they are in deficiency range. The average and maximum concentrations of soluble fluoride in soil samples were 1.0 and 3.2 mg kg-1, respectively. In general, the spatial distribution of fluoride in soils showed that fluoride content around major industrial centers such as Isfahan Steel Factory, Mobarakeh Steel Co., and Isfahan oil refinery was higher than other sites. The minimum and maximum fluoride contents of crops were observed in alfalfa as 0.2 and in corn as 4.2 mg kg-1, respectively. Tomato had the highest mean concentration of fluoride as 3.6 mg kg-1. The fluoride concentration in plants positively correlated with the fluoride concentration in irrigation water and soil (P < 0.01) and negatively correlated with cation exchange capacity of soil (P < 0.05).
E. Dehghan, A. Naderi,
Volume 11, Issue 41 (10-2007)
Abstract
This study included two experiments conducted in 2000-2001 for surveying the effects of saline water irrigation on yield and yield components in corn varieties. Experiments were conducted in a silty-clay soil in Ahwaz Agricultural Research Center. First experiment was conducted as a split plots and randomized complete blocks design in three replications. Main plots included salinity levels 2, 4, 6 and 8dS/m and subplots included three single cross hybrids of corn 704, 711 and 647. In the other experiment the effects of saline water 8dS/m at different growth stages including the stage of planting to plant establishment. (G1), flowering and pollination (G2) and grain filling (G3), were evaluated. The results of the first expriment showed that there was very significant difference among water salinity levels for yield, thousand kernel weight, percentage of corn fertility and percentage of plants containing corn. The highest and lowest grain yield were obtained for salinity levels 2 and 8dS/m treatments respectively. Differences among varieties and interaction of treatments were significant for grain yield, and highest grain yeild was obtained for 704 and 711 varieties on saline water 2dS/m. The results of the other expriment showed that highest and lowest tolerance to irrigation with saline water on corn were G3 and G1 growth stages respectively. Consequently, hybrids 704 and 711 were more sensitive than the 647, but the obtained yield, suggests that 704 and 711 hybrids can be cultivated under these conditions.
S.h. Lack, A. Naderi, S. A. Saidat, A. Ayenehband, G.h. Nour – Mohammadi, S.h. Moosavi,
Volume 11, Issue 42 (1-2008)
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.
A.a. Shahroudi , M. Chizari,
Volume 11, Issue 42 (1-2008)
Abstract
The purpose of this study was to investigate and analyze the factors affecting farmers’ attitudinal dimensions toward participation in Water Users’ Association (WUA) by comparing two groups of farmers in irrigation networks with WUA and without it. The methodological approach was a descriptive-correlational and causal-comparative study of the survey type. The target population in the study consisted of 2551 farmers of irrigation networks in Khorasan-e-Razavi Province, Iran. Using stratified random sampling technique, 335 participants were chosen. Data were collected through a questionnaire, and analyzed using SPSS, V.13. Content and face validity of the instrument were obtained by the faculty members of Agricultural Extension and Education, Agronomy and Irrigation Departments at Tarbiat Modarres University and also specialists board of Agricultural Jihad Organization and Regional Water Joint-stock Company in Khorasan-e-Razavi Province. The reliability analysis was conducted and cronbach’s alpha values for the various sections of instrument were estimated between 0.73 and 0.86. The descriptive findings of the study showed that the majority of farmers’ overall attitude with respect to participation in WUA was at a good level. The results obtained from Pearson correlation analysis indicated that there are significant and positive relationships between such variables as education level, size of irrigated cultivated landholding, annual income, extension contacts, social capital components, water users’ perceptions regarding irrigation networks status and farmers’ participation status concerning irrigation networks management with the farmers’ overall attitude toward participation in WUA. The result of stepwise multivariate regression analysis indicated that 61.1% (R2 = 0.611) of the variance in farmers’ attitudes with respect to participation in WUA could be explained by farmers’ behaviour regarding optimum farm water management, social participation, social confidence, water users’ perceptions regarding irrigation networks status, farmers’ participation status concerning irrigation networks management. Also, significant differences were found between the two respondent groups in irrigation networks with WUA and without it in relation to farmers’ attitudinal dimensions.
M. Vafakhah, G.h. Shojaei,
Volume 11, Issue 42 (1-2008)
Abstract
Continuous measurement of river discharge is a hard and expensive task in hydrology. To overcome this problem, the stage readings at hydrometric gauges are permanently taken and the discharge of any time at which the actual discharge is unavailable will be estimated through a relationship between discharge and stage. To study the stage-discharge relations and the capability of long-term data in establishing a permanent stage-discharge relationship, and also to determine the best time to measure the discharge of rivers, a study was conducted at the hydrometric station of the Zayandehrud regulatory dam using data from 1990 to 2003. The data were analyzed using simple regression analysis, the percentage of relative error and factor analysis. The results indicated that the best model to show the stage-discharge relation at the studied station is a power function model. Moreover, the model used for every year can only be used for that year. The results also showed that the most suitable times for the measurement of discharge are July, December and March.
S.a.a. Hashemi, M. Arab Khedri,
Volume 11, Issue 42 (1-2008)
Abstract
In order to quantitatively evaluate the sediment yield in ungauged basins, it is necessary to use empirical models. The EPM model, as a model which is using in Iran, has sometimes been evaluated. Most evaluations have often been conducted by using river's sediment information and direct measurements of dam reservoir sedimentation have been less used, while the sediment measurement method on reservoir is more carefully. 9 small watersheds from Semnan province (Iran) were selected in this research. There is a small earth dam which have been built on the outlet of each watershed in the past years that them age is 10 years. These dams have not been weirs since they have been building to now. Therefore total of sediment yield volumes of each watershed are entrapped in the dam reservoirs. The volume of sediments deposited in reservoir were calculated by surveying. Sediment's apparent specific weights were measured in each reservoir and the volume of sediments transformed into sediments weight. By EPM model the volume and weight of sediment yield were estimated. Values of sediment yield measured in reservoirs were compared with estimated values by t-test. The results showed that at level 5%, there was not any significant difference between sediment yield values estimated in reservoirs by EPM model in comparison with values of volume and weight which were measured. But determination of performance and relative root mean square error showed that EPM model has low efficiency for estimation of sediment yield in the case study of watersheds.
M. Naderi Khorasgani, A. Karimi,
Volume 11, Issue 42 (1-2008)
Abstract
This research was carried out to study the impacts of geomorphologic characteristics of claypan on land use and land degradation. Databank of the study area was constructed and digital terrain model of claypan was prepared. By using GIS techniques spatial distributions of the subsurface drainage network, sediment transportation index and wetness index were calculated. The results indicate that the depth to the claypan is between 0 (where the pan is exposed at the surface) to 605 cm. There are several depressions in the claypan which are filled by new sediments. Each depression has a catchment which is charged by the drainage water of its attributed lands. While a depression drains naturally or synthetically, the attributed soils over the depression are in non saline or moderate salinity condition otherwise, a marshland, a waterlogging area or a salt crust zone develops over there. The results also indicated that soil surface salinity is a function of depth to claypan and drainage condition of area. The trends of salinity extension are different for closed and open catchments and the depth to the claypan could be estimated using electrical conductivity. The results also show that analysis of microtopography of soil surface and soil stratification should be considered for designing irrigation and drainage networks.
S.a.a. Hedayati, V. Yavari, M. Bahmani, M. Alizadeh, R. Kazemi, A. Hallajian,
Volume 11, Issue 42 (1-2008)
Abstract
Great sturgeon is one of the most economically important species. However, in recent years overfishing, illegal fishing, etc., have resulted in severe declines in the stocks of this species. For conservation, stock of this species, determination of gonadal situation and its gonadal growth exchanges is very important. This paper is a histological approach to gonadal staging in 74 Huso huso in the 4 – and - 5 - year old classes. The fishes were reared in brackish water concert tanks under controlled conditions. A small section of the gonads of each fish was removed by biopsy. The gonadal tissue was fixed in buoin solution. They were dehydrated in different diluted solutions of alcohol and chloroform until they were clear. Then they were embedded in paraffin and sectioned at 7 µm and stained by hematoxylin and eosin method. Of the four-year old fish, %56 and %44 were males and females, respectively. %6 of males were at stage I %11 stage I-II %61 stage II %13 stage II-III %11 stage III-IV and %8 were at stage IV-V. %3 of the females were at unknown stage %3 stage I %11 stage I-II %60 stage II %14 stage II-III and 9% stage III. Of the 5 year old fish, %12.5 of males were at stage II % 25 stages II-III %50 stages III and %12.5 were at stage IV. %62.5 of females were at stage II and %37.5 were at stage II-III. Results of this study Compared with those obtained from fishes of the same age class studied in natural habitats as well as the results obtained for the farmed sturgeons from freshwater medium indicate that there is no similarly in the stage of gonadal development in different conditions. Longest stage in tow sexes was stage II that is longer in females, and passing of stage II in males is faster. Males showed more sexual maturity than females. Gonadic growth in culture medium is faster than wild condition, and it is faster in brackish water than fresh water. So, we can state that brackish water is a suitable medium for gonadic growth of Great sturgeon.
A. Mohammadi Mohammadabadi, S.j. Hosseinifard, N. Sedaghati,
Volume 12, Issue 43 (4-2008)
Abstract
Effect of change from the conventional (flooding) to subsurface irrigation system was studied on mature pistachio trees (Cultivar Ohadi) in Kerman pistachio research station for four years. This experiment was carried out in a randomized complete block design including 7 treatments and 3 replications. The experiment also used two irrigation intervals (7&14 days) and three water rates according to pan coefficient (20%, 40%& 60% evaporation from surface of class A pan) for subsurface irrigation system with 6 treatments the conventional (flooding) irrigation system was tested as control. The pipes of subsurface irrigation system were installed at 90cm distance from trees trunk at each side of trees, and 50cm from soil surface. Mean of pressure and discharge in the pipes was 0.8 to 1 atmosphere and 5.4 Lh-1m-1, respectively. Different factors of quantity and quality pistachio yield, current vegetative growth, water use efficiency and soil electrical conductivity were measured. The results showed that change of conventional (flooding) to subsurface irrigation system is possible and the best treatment can have water rate of 7174 m3ha-1y-1 with 14 days irrigation interval. In comparison with other treatments, this treatment has better quantity and quality pistachio yield. Water use efficiency (WUE) of this treatment was 164g dry yield per cubic meter. Nevertheless, application of water rate of 4783 m3ha-1y-1 can result in the deficiency of irrigation water. At this water rate, WUE was 177g dry yield per cubic meter. However, it was found that the application of lower water rate (<4783 m3ha-1y-1) produced severe effects on the treated pistachio trees, e.g. decreasing the growth rate, yield and increasing the early splitting in pistachio fruits. Finally, it is concluded that 14-day interval irrigation is the preferred treatment for pistachio trees. Also, soil salinity showed considerable change in subsurface irrigation treatments after irrigation system was changed, especially in the first year.
M. Sabouhi, G.h. Soltani,
Volume 12, Issue 43 (4-2008)
Abstract
The objective of this study is to introduce an approach for determination of comparative advantage of Basins in the production of crops, enhancing water use efficiency and directing cropping patterns to maximize net virtual water import. A model was constructed and applied assuming five different risks in available water and three levels of irrigation efficiencies (35, 45, and 65). The findings showed that, it is possible to direct optimal cropping pattern at basin level to maximize social profit, water use efficiency and net virtual water import simultaneously. However, in order to derive a definite conclusion, more data are needed about the quantity water embedded in each crop exported from and imported to each country. Moreover, it is necessary to design a suitable export-import plan to be used as a target for directing cropping patterns toward it. The approach used in this study can be viewed as a first step in this direction.
K. Majd Salimi, S. M Mir Latif,
Volume 12, Issue 44 (7-2008)
Abstract
In tea plantation regions of northern part of the country, application of supplemental irrigation during dry periods (lacking rainfalls) in conjuction with proper nitrogen fertilizer application can significantly improve tea yield per unit of plantation area. In order to quantify the effectiveness of proper irrigation and nitrogen management on tea, the response of tea to various levels of irrigation and nitrogen applications was studied in Fouman suburb of Guilan province. Tea crop production function and its crop coefficient (KC) were determined. A line source sprinkler irrigation was used for creatiating a variable irrigation application and a split-split-plot statistical design was used. Irrigation treatments consisted of full irrigation (I4), deficit irrigation (I3, I2 and I1) and no irrigation(I0). Nitrogen application treatments were N1, N2 and N3 (100, 180 and 360 kg/ha) in three replications randomly arranged as main plots, while irrigation treatments as sub plots were not randomized. During the growing period, soil moisture up to the depth of 90 cm was determined gravimetrically and actual crop water use was calculated from mass balance equation weekly. Reference evapotranspiration (ETo) was estimated by Penman-Montieth equation and was used to estimate tea crop coefficient. During growing period, the actual tea water use of I4 and I0 were computed to be 457 and 256 mm. Tea crop coefficient during dry period (June, July and Augest) ranged from 0.8 to 0.9. Crop resistance factor (Ky) for tea was found to be 1.37. Results indicated that optimum rate of nitrogen (180 kg/ha) along with supplemental irrigation, increased yield and water use efficiency (WUE). Futhermore, supplemental irrigation increased yield and WUE more than nitrogen application. In I0 and I1 treatments, application of 100 kg/ha nitrogen resulted the highest yield and WUE.
J. Torkmani, Sh. Shajari,
Volume 12, Issue 44 (7-2008)
Abstract
The main objective of this paper is to study the differential impacts of various irrigation water pricing policies. The methodology used is based upon Multi-Attribute Utility Theory (MAUT) mathematical programming models and also simulation. Two kinds of data needed to feed the models were obtained from official records and surveying. The analysis of water pricing policy indicates that the most important relative savings take place in the more conservative farmers due to their risk-aversion behavior. Also it can be seen that in the elastic segments of the demand curves the increase in the price of water encourages great saving in consumption due to changes in mixed crops, crops production by deficit irrigation methods and production of rain-fed crops. Results clearly demonstrate that each homogenous group of farmers displays different behavior patterns related to this natural resource. Therefore, this shows the usefulness of differential analysis in evaluating the impact of water pricing policy.
H. R. Balouchi, S. A. M. Modarres Sanavy, Y. Emam, M. Barzegar,
Volume 12, Issue 45 (10-2008)
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.
