Journal of Water and Soil Science
Year:2007 | Volume:11 | Issue:41 (A)|Papers Count:23

A labyrinth spillway is an overflow spillway to regulate and control flow in canals, rivers and reservoirs. The main hypothesis for the development of such a spillway is to increase the discharge per unit width of structure for a given headwater. This type of structure is often an efficient alternative to a gated-spillway type where either the increase of the flood-passage capacity or the control of the water surface upstream is concerned. This study was aimed to investigate the hydraulic performance of labyrinth spillways of general trapezoidal plan form with simple curved apexes.In the experimental work, twelve spillway models with double cycles were considered using three different curved apexes (R/w=0.15, 0.2, 0.25), each with four different crest heights (w/P=1.5, 2, 3, 4). Based on the cited recommendations, the length magnification was set to a constant ratio of (l/w=3); the crest shape was to be of a semicircular form with simple radius (r=15 mm); and the spillway walls were vertical with the thickness of T=2r. An intensive experiment was carried out over a wide range of flows, providing 720 flow data ranging from free flow to submerged flow conditions. 1D flow equation was presented using combined mathematical and dimensional analysis. A coefficient of discharge, Cd, was introduced to represent the influence of the effective geometric and hydraulic parameters on the flow capacity over the spillway. Modular limit was also controlled to see whether the flow over the spillway would be submerged. The results of the study indicate that the modified curved plan form of the spillway apexes with consistent divergence in the downstream channel introduces a significant improvement in the flow efficiency over the labyrinth spillways. Spillways with narrower curved apexes (i.e. R/w4 0.2), and with the vertical aspect ratio of (24w/P<3) provide more stable and higher hydraulic performance than any other labyrinth plan forms over a wide range of flows (i.e. 0.1<H0/P<0.6). In terms of the flow capacity, the proposed spillway model is shown to be more efficient than other zigzag plan forms (i.e. triangular and trapezoidal shapes) with an identical crest length.

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 (Ecbatana 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.

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.

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).

To investigate the chemical behavior of zinc sulfate and the effect of organic matter and salinity on the distribution and concentration of zinc speciation, a randomized factorial design study was conducted in three levels of salinity, with two organic matter levels and two Zn levels in the form of ZnSO4 and in four soils with three replications. Samples were incubated up to six months at laboratory temperature and were analyzed for pH, EC, NO3-, PO4-3, K+, Na+, Ca+2, Mg+2, Zn+2 Cl-, HCO3- SO4-2 and Dissolved Organic Carbon (DOC) after two, and after six months. Chemical speciation in soil saturation extract was estimated using MINTEQA2 model. Increasing EC in saturation extract caused significant increase in saturation extract total concentration of zinc in all the soil treatments. Increasing salinity increased concentration of zinc cat ion in all the soil treatments. Also increasing salinity decreased Dissolved Organic Carbon (DOC). Manure application led to a significant increase in total soluble Zn. Moreover, addition of organic matter increased soil soluble Zn concentrations.

Soil particle size distribution and bulk density are used for estimating soil-moisture characteristic curve. In this model, soil particle size distribution curve is divided into a number of segments, each with a specific particle radius and cumulative percentage of the particles greater than that radius. Using these data, soil-moisture characteristic curve is estimated. In the model a scale factor, a, is used which may be considered as a constant, or obtained by logistic or linear procedures. For most conditions, soil particle size distribution curve is not available, but only the percentages of clay, silt and sand could be obtained using soil textural data. In this situation, at first a precise soil particle size distribution must be developed, based on which the soil-moisture characteristic curve can be predicted. According to the previous studies, using particle radius of 999 ¥m is more appropriate than radius 125 ¥m. Also, adjusted coefficients for estimating soil particle size distribution curve for radii 1 to 20 ¥m was obtained. In this study, using the soil textural data of 19 different soils from UNSODA database, soil-moisture characteristic curve of each was estimated with logistic and linear methods based on initial and adjusted soil particle size distribution estimation. The estimated values were compared with the measured data. The results indicated that for most soils, using the combination of logistic and adjusted particle size distribution estimation procedures is more appropriate than the previous methods.

Sugarcane (Saccharum officinarum L.) and rotational crops have been cultivated without potassium fertilizers for many years in southwestern Iran. Although potassium was removed from this soil, no response has been reported to K fertilizers by crops. This study was conducted to evaluate the effects of wetting and drying, and cultivation systems on potassium fixation in some Khouzestan soils. The results showed that expandable clay mineral was observed in cultivated soils but not in the non-cultivated soils. This may be related to irrigation, and cultivation practices in this soils. By adding K and sequential wetting and drying the amount of K-available increased in sugarcane, rotational cropping and uncultivated soils from 132.6, 226.2 and, 171.6 mgkg-1 to 266, 447 and 628, respectively. These results showed that more K can be fixed after cultivating soils, especially by sugarcane, but available K increased by adding K. All surface soils had higher K fixation capacity than subsurface ones. Also, by application K to these soils, the amount of K fixation decreased with increasing wetting and drying times. The K fixation increased by the increase of cation exchangeable capacity. Significant difference was observed between cultivation system and depth of sampling in 1% levels. High K fixation can be attributed to illite minerals depleted from K. Mica-like minerals formed after adding K, and wetting and drying cycles. Amount of K fixation by clay particle samples was more than the same soil samples but in both the same trend was observed for K fixation. Also, drying and wetting decreased K fixation in the last periods. It may be due to trapping K in the interlayer positions.

The increased potential for soil erosion and compaction due to continuous row crop production and intensive tillage is causing some concern and has led to the consideration of reduced tillage techniques as part of the solution. The objective of this study was to investigate the short-term (one-year) influences of different management practices on the physical properties of a sandy loam soil under corn crop. Treatments were the combinations of three tillage systems (notill, NT; chisel plow, CP; and moldboard plow, MP) and three composted cattle manure rates [0, 30 and 60 ton (dry weight) ha-1]. The experiment was carried out in a split-plot design. Three replicates of the treatments were applied in a randomized block design. Saturated hydraulic conductivity (Ks), total porosity (TP), macro-porosity (Macro-P), micro porosity (Micro-P) of soil and mean weight diameter (MWD) of aggregates, were measured to a depth of 22.5 cm when 100 percent of the tassels appeared. Tillage and manure combination had significant effects on Log [Ks], TP, Macro-P and Micro-P. The MP system increased pore space and continuity due to complete inversion and loosening, and as a result Ks, TP, Macro-P and Micro-P were higher than NT system. Higher Macro-P observed for CP might have caused higher Ks versus MP. Reduced tillage systems increased MWD and the increment of manure caused an increase in MWD over all tillage treatments. The results indicate short-term positive effects of manure application on soil pore size characteristics and aggregate stability under moldboard and chisel plowings in the region.

The effect of overgrazing on vegetation changes in central Zagros has been studied by a few scientists, but there is no detailed information on the impact of such practices on soil properties. The objective of this study was to assess the effect of climate and grazing management on selected soil biochemical properties. Fourteen experimental range sites protected against grazing as well as their adjacent overgrazed sites in Chadegan, Pishkuh and Poshtkuh were selected. In each site, samples were collected from the depths 0-5 and 5-15 cm. Soil organic C (OC), microbial biomass C (MBC), total nitrogen (TN), organic C to total N ratio (C/N), microbial biomass C to organic C ratio (Cmic/Coc) and metabolic quotient (qCO2) were measured and/or calculated. The results showed that the lowest SOC, MBC, TN and Cmic/Coc occur in Chadegan due to low fresh materials input. The above parameters in Pishkuh and Poshtkuh regions are 2.5 to 3 times greater than those in Chadegan area. Grazing intensity in Pishkuh is less than that in Poshtkuh region and there is no significant difference between grazed and protected sites in Pishkuh. But, there is a significant difference between grazed and protected plots in Poshtkuh due to a higher grazing intensity. Higher Cmic/Coc and lower qCO2 suggest that the quality of organic matter is better in Poshtkuh and Pishkuh. In conclusion, highly degraded rangelands in Pishkuh and Poshtkuh seem to be able to recover very quickly with proper management, while Chadegan region needs a much longer period of time to restore.

The present research was intended to alleviate the problems and costs of deep tilling in sugarcane production in Mian-Ab sugarcane farms located in Khuzestan province, Iran. The main objective was to investigate the feasibility of subs oiling operations with bent leg subs oiler (BLS) equipped with shallow tines a combination expected to increase the critical depth resulting in less power consumption and improved soil physical conditions. Six treatments arranged in a completely randomized block design were used to measure the draft force (except for the bulldozer mounted rippers), disturbed soil cross-sectional area and penetration resistance. The treatments included (1) subs oiling with rippers mounted on bulldozer, (2) BLS without attachment, (3), and (4) BLS equipped with single tine at working depths of 1/2 and 1/3 of target depth, (5) and (6) BLS equipped with two tines at 1/2 and 1/3 target depth. The experiment was replicated three times. The results indicated that BLS without attachment had the highest draft requirement as compared with other BLS treatments with shallow tines. In general, tine attachment resulted in less draft mainly due to displacement of critical depth to lower soil zones. Increasing the number and depth of shallow tines resulted in less draft force. The BLS equipped with two tines working at 1/2 target depth exhibited minimum drawbar power. The inclusion of shallow tines resulted in 21% reduction in drawbar power requirement as compared to BLS without tine attachment. The cross sectional area of the soil tilled by ripper was minimum Furthermore, the tilled area was not uniform and subsequent sub soiling operations were needed. The average soil cross-sectional area per unit width was improved by BLS treatments by a factor of 2.3 as compared with that of ripper. The highest cone index was obtained in plots tilled by ripper; the BLS reduced this index in a significant manner. The soil worked with subs oiler equipped with tines exhibited the least resistance. The range of wheel slippage for BLS treatments was 12-16% which lies in the upper end of the recommended range for optimum traction efficiency. The proposed idea proved prominent in subsoil in g fine textured compact soils.

This research was conducted in order to select male genotypes of pistachio with good performance. The study was performed on 10 genotypes in regard to their flowering time, pollen quantity and quality. The results indicated that flowering times of P1, P2 genotypes were simultaneous with Kallehghochi; P3, P4, P5 genotypes with Ahmad Aghaii; P6 and P7 genotypes with Ohadi and P8, P9, P10 genotypes with Akbari. Inflorescence weight showed big differences between them, ranging from 4.5gr for P6 to 1.66gr for P8. The amount of pollen per inflorescence also showed big difference, ranging from 71mg for P2 and 267mg for P5. In order to determine the percentage of pollen germination, a medium consisting of sucrose, agar and boric acid was used. The percentage of pollen germination also showed big difference, ranging from 30%for P3 and P4 and 85% for P10. Stored pollen at 4oC temperature showed 30% germination after one month and 0% germination after three months. The results also indicated that the percentage of pollen germination in culture medium without boric acid was lower, compared with other treatments. The viability of pollens collected from cutting inflorescences kept in water bottle was higher than that obtained from dried inflorescences maintained in room condition.

To investigate genetic variation, and identification of tolerant genotypes according to quantitative indices of drought tolerance, 8 sesame genotypes were tested in a randomized complete block design with three replications under optimum and limited irrigation at the Research Station of College of Agriculture, Shiraz University. Based on the potential yield and yield under stress, quantitative indices of drought tolerance such as mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HM), stress tolerance index (STI), stress susceptibility index (SSI) and tolerance index (TOL) were determined. The result of analysis of variance exhibited highly significant differences among the genotypes for all the indices measured, and yield under optimum and limited irrigation, indicating the existence of genetic variation among genotypes, and thus the possibility of selecting drought tolerant genotypes. Mean comparison displayed that the highest potential yield, stress yield, MP, GMP, HM and STI were related to the genotype number 5. Correlation analysis between indices, mean potential and stress yields indicated that every four indices are suitable for screening the genotypes. Based on these indices and higher yields under optimum and limited irrigation the best drought tolerant genotypes were identified to be genotypes number 4 and 5. Multivariate biplot indicated that the genotypes number 4 and 5 were located next to the vectors of drought tolerance indices, including MP, GMP, HM and STI. Cluster analysis showed genetic distance among genotypes. As a result, genotypes number 4 and 5 were identified as drought tolerant and genotypes number 1, 2 and 3 as susceptible to drought.

Germplasm collection is the base of plant breeding. Iran is one of the most important centers of genetic diversity due to different climates and the old civilization.In this study we decided to collect melon accessions. The north and center of Iran were selected for this purpose. Fifteen qualitative and six quantitative traits were measured on thirty eight accessions. The cluster analysis by the use of UPGMA method and Jaccard coefficient helped separate the horticultural groups of Cucumis melo L. (Cantaloupen sis, Inodorus, Flexousous, Reticulatus). The relationship between 30 of these accessions was assessed using 10 RAPD primers. The polymorphism was determined to be19%. The cluster analysis could not separate the horticultural groups of Cucumis melo L., showing that these groups are closely related. However, VB84 primer separated the tow Snake melon.

This study was performed in two barley fields, in Experimental Station, Agricultural College of Ferdowsi University of Mashhad in 2003. Sampling was done by systematic method in which samples were taken from the corners of 7m*7m grids using 0.5m x 0.5m size quadrates in three stages (pre herbicide, post herbicide and pre harvesting stages). The results indicated that the density of annual weed seedlings in sugar beet- barley rotation was more than fallow- barley rotation, and the density of perennial weed seedlings in fallow-barley rotation was more than sugar beet- barley rotation. Map of species distribution and density confirmed patchiness distribution of the weeds. The shape and size of patches differed based on the field and weed species, but spatial distribution did not change considerably before and after the application of herbicide. Percentage of free weeds area was 11.5% and 1.5% in fallow-barley rotation and 0.6% and 0% in sugar beet barley rotation in the first and second sampling stages, respectively. These results indicate beside emphasis on weed infestation. The result also indicates inefficacy of sugar beet - barley rotation compared to follow-barley rotation.Apparently, the evaluation of management and paying special attention to weed dispersal within the field assist in the implementation of appropriate management strategy, which includes high eft1cacy,and profit for farmers as well as least damage to crops.

Fescues (Festuca spp) are widely distributed in the temperate regions and are used for turf, forage and soil conservation.Though seed traits are important measures of the effects of endophytic fungi on their host, little information is available in this respect for Festuca. In this study, endophyte - infected (E+) and endophyte - free (E-) clones of the six fescue genotypes were used to investigate the effects of endophyte on seed production. The relationships between seed traits plus direct and indirect effects of components on seed yield were also studied, Endophyte infection resulted in 38.1% to 249% more seed yields in some genotypes, though some were not affected b) this symbiotic relationship, Correlations between traits and also results of stepwise regression were influenced by the presence of the symbiotic fungi. Path analysis showed that endophytic fungi changed direct and indirect effects of components on seed yield. In endophyte containing clones, panicle fertility had the most direct effects and number of panicle per plant and seed per panicle the most indirect effects on seed yield. In E- clones, panicle fertility had the highest indirect effects and other components had direct effects on seed yield. The results suggested that breeding strategies for increasing seed yield in fescue should consider the presence or absence of endophyte in germplasm.

In order to study the effects of salinity on germination, vegetative growth and some physiological characteristics of canola cultivars, two experiments were conducted at Research Station of Agricultural College of University of Kerman in 2004. The experimental design was a Completely Randomized Block with four replications. Treatments comprised all combinations of different levels of three factors including variety (Kobra x Regent, Ceres and Okapi), salt type (NaCl, CaCl2) and electrical conductivity of saline solution (0, 4, 8, 12 dS/m). Results of variance analysis showed that salinity has a very significant effect on germination percentage, germination homogeneity, germination rate, wotlet and polomul length at the end of the germination stage. Shoot length, dry weight, diameter and number of nodes per shoot were significantly affected also by salinity at vegetative growth. Regarding the two types of salt, none of the measured traits were significantly different. All the mentioned traits decreased with increasing salinity; the highest and the lowest values were recorded at control and at 12 dS/m salinity levels. Membrane ion leakage was the only trait which increased significantly. Comparison of means showed germination percentage and germination homogeneity at germination stage and the number of nodes at vegetative growth stage were affected less than other traits by salinity, and they only decreased significantly with increasing salinity to 12 dS/m. The effect of cultivar on these traits was also significant (P<0.001). In both growth stages, cultivars response to salinity was different. At germination stage, Ceres and Kobra* Regent cultivars were the most sensitive and tolerant ones in terms of all traits and there was no significant difference between Okapi and Kobra *Regent. At vegetative growth stage, however, Okapi showed less growth than Kobra * Regent and their difference was significant. It seems that evaluation of traits response at germination stage can not be effective to determine salt tolerance of canola cultivars.

In order to evaluate relationship between Different traits in lentils (lens culinaris Medik), a field study was conducted as an RCBD based design with 3 replications on Zanjan University Research Farm during spring of the year 2004.ANOVA analysis revealed significant differences for all characters except for the number of primary branches.Correlation analysis indicated positive and significant correlation between seed yield and harvest index, number of primary branches, pods/plant and biological yield, and grain yield. The result of the factor analysis also showed that the second factor including number of primary branches, pods/plant, grain yield, canopy width and seeds/plant was an important trait involved in the grain yield in lentil. In addition, cluster analysis helped divide the genotypes into four distance groups of large, medium, semi medium and low yields.

Flora identification of each region plays an important role in the maintenance of natural resources of each country and it is a prerequisite to supplementary phylogenetics and genetic diversity studies. During February 1994 to August 1995, in a two-week interval, vineyards in two districts of Isfahan province, namely Zarinshahr and Tiran & Karvan were visited and weed samples were collected in flowering stages. All collected specimens were identified using specimens present in Herbarium of colleges of agriculture and natural resources of Isfahan University of Technology and other available references. The analysis revealed that in Tiran and Karvan, 84 species belonged to 71 genera and 26 families and in Zarinshahr 62 species belonged to 51 genera and 23 families. Species dominance in both districts belonged to Asteraceae and Gramineae families. Analysis of plant life forms using Raunkiaar method showed that Therophytes with 79.5% and Geophytes with 8.3% were the most frequent life forms in both Zarinshahr and Tiran & Karvan regions.

Thirty soybean cultivars from different maturity groups were evaluated in a randomized complete block design with four replications in Research Station of College of Agriculture at Tehran University in Karaj in 2004. The purpose was to determine genetic relationship of some important agronomic traits related to seed yield. Analysis of variance showed that there were significant differences among varieties for the traits under study, indicating the existence of genetic variation among varieties. Number of pods/plant, number of seeds/plant and 100-seed weight, all of which are considered yield components, had the highest genotypic correlation with seed yield. Using stepwise regression analysis, 85.6 % of seed yield variation was attributed to four traits, including harvest index, biological yield, protein percent and number of seeds /plant. Harvest index was more important for predicting seed yield compared to other traits based on standardized I3s. Results of path analysis showed that the harvest index and protein percentage had the highest and lowest direct and positive effect (p=0.536), (p=0.008), respectively. Therefore, harvest index may be considered as selection criteria to improve seed yield in breeding programs. Results of factor analysis showed five independent factors accounted for 80.2 % of total variations in data. The first principle determined 28.2 % of total variation and was designated as phonologic factor.

To evaluate the effect of plant density and detopping on grain yield, protein content biological yield harvest index, growth indices, number of cob in each plant, No. of row per ear, No. of grain in each row, thousand seed weight of corn (Zea mays L. ar. se 704), an experiment was conducted at the experimental statues of Research Center of Uremia Agricultural College in 2004. The Treatment design was split plot in randomized complete block design with four replications. The main plots included plant density at three levels (53000, 66000, and 88000 Plants/ha) and the subplots comprised three levels: (1) no detopping (control); (2) removing canopy only; and (3) removing canopy and three leaves above the node. Analysis of Variance of data showed that both detopping treatment and plant density influenced the number of kernel per ear, 1000 grain weight, ear weight, total dry weight of biomass, seed yield and harvest index.Canopy detopping led to a marked increase in photo assimilateion import grains. The highest plant density evaluated, 88000 plants per hectare with detopping of three above leaves had the highest number of cobs per square meter. In plant density of 53000 plants per hectare and canopy detopping treatment, the number of grain per ear was greater than other densities. The efficiency of harvest index increased under corn detopping compared with control, and this increase with an increase in photosynthesis contributed to grain yield. It was concluded that major increase in grain yield under high plants density and tassel detopping was due to improvement of physiological indices.