JWSS - Journal of Water and Soil Science

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In 1998 and 1999, adult population density of pistachio psylla and its sex ratio were determined weekly in two orchards with yellow sticky board traps and limb jarring. Also egg and nymphal population was determined on the leaves. By studying the seasonal population fluctuaions, the efficiencies of the two methods were compared. Meanwhile, using yellow sticky boards, diurnal activity of adults was investigated. Adult pistachio psylla became active during flower and leaf bud opening. Adult capture with both methods showed a high correlation with egg and unwinged nymphal density counts, with at least five peaks (maximum six). Two peaks occurred during spring and densities were much lower in comparison with those of later generations. First adult capture was observed on yellow traps. Yellow traps were found to be a better method than the limb jarring method for the study of seasonal population from adult captures. Sex ratio was equal through out the growing season and during the warmer or cooler months of the year. However, more males were attracted to traps and more females were captured with limb jarring early in the season. Peak activites during day occurred through 9-16 p. m.

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Pistachio oyster shell scale is one of the important pests of pistachio in Iran whose females are reported to exist in two or three forms, each form developing on a specific part of the pistachio tree. In this study, abundance of the pest is investigated on leaves and branches for different ages, two heights and four cardinal directions of tree crown. Paralelly seasonal population fluctuations of three forms were studied on leaves, and one-and two-year-old branches separately. This insect overwintered as female mostly on one and two-year-old branches. It had two separable periods of activity, through the season. In the first period, eggs mostly hatched in April and crawlers mostly settled on leaves, fruits and newly grown twigs but rarely on older branches.These populations are male and female. In the second period, eggs mostly hatched in June, and crawlers settled mostly on leaves and one and two-year-old branches, but all individuals settled on leaves are males and those on branches are females. Population density is significantly higher on upper surface of leaves than on the lower surface. Analysis of variance showed that only significant differences existed in densities observed between trees in both generations, and also between two heights of tree crown for populations settled on wood. Two predatory species from Cybocephalidae and Coccinellidae, one ectoparasitoid from Aphelinidae and two endoparasitoids from Encyrtidae were collected as natural enemies of this pest in Isfahan.

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To determine the water application efficiency in furrow irrigation more accurately, consideration of seasonal and spatial variation of infiltration properties are needed. In addition, the effectiveness of different farm management on infiltration are significant. The main objective of this research was to simulate the seasonal variation (SV) of infiltration coefficients in Kostiakov-Louise equation (KLE) in a cracking soil under two traditional farm managements. Farm studies carried out in a clay-loam soil in Karaj. The two management treatments were soil without wheat residual and soil with wheat residual by a 5 ton/ha rate. There were 22 furrows with 0.75 m width in the farm. KLE infiltration coefficients were measured using inflow-outflow and two point’s methods in six furrows. The results of this study indicated that the SV of a and k coefficients were not significant, but variation of f0 was significant which was simulated with a logarithmic model. The effectiveness of SV on cumulative infiltration (Z) was also evaluated and indicated to be significant that were simulated with a logarithmic model too. Finally, dimensionless parameter such as Z* were developed to predicate Z parameter in different irrigation time, irrigation events and different residual management. Base on the result, although residue management causes a significant difference between value of f0 and Z in two treatments, but it doesn’t effect on trend of variation during the season. It means that the trend of variation is independent of residue in soil. It is probably done because of change in some of soil physical properties such as soil bulk density and aggregate stability.

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Seven species of aphids belonging to the family Aphididae in six genera were collected and identified in wheat and barely fields in Sistan region (Miankangi, Shahraki-Narooi, Shibab and Markazi) during1999-2000. Among them, Schizaphis graminum (Wheat green aphid) was the dominant species with an abundance of about 85.4% in the area. The seasonal population changes of Schizaphis graminum were studied simultaneously in the fields of Sistan region (Zahak research station and its surrounding fields). The research was conducted in half a hectar of each farm. Thirty leaves from each field at weekly interval were randomly picked up and the aphids were collected and identified at the species level. The Schizaphis graminum had a peak of activity in the second half of March to April at the temperature and R.H. ranges of between 22-28ºC and %45-65R.H. respectively. The control conditions study (Incubator with 25±2ºC and %75±5R.H.) indicated that the Schizaphis graminum had a life cycle of 5-7 days and adult female longevity was 20-31 days. Rearing study also revealed that this species had ability to reproduce up to 18-98 nymphs in the laboratory condition (Cultural room with 20-25 ºC and 55±5R.H.) and an apterous female gave birth to 22-93 nymphs in her life. Samplings for recognition of predators and parasitoids were also done at 3-day intervals. Natural enemies in the fields during the two years were identified as consisting of six coccinellid (Col:Coccinellidae), ten syrphid (Dip:Syrphidae) and two chrysopid species (Neu: Chrysopidae). Also in Hymenoptera, five parasitoids (Hym:Aphidiidae) were determined.

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  Aphids are known as important pests of plants specially almond trees. Seasonal population fluctuation of two aphid species, Brachycaudus amygdalinus (Schout.) and Hyalopterus amygdali (Blanch.) were studied in 1999-2000 on almond trees in Najafabad area. Characteristics such as times of egg hatch, appearance, outbreak, spring migration to alternative hosts, migration from alternative hosts in fall, oviposition, number of eggs laid, damage degree, alternative, other primary hosts and some natural enemies were investigated. In early spring damage signs of B. amygdalinus were expressed on almond twigs as serious leaf curling followed by retarded growth of twigs and shortened internodes. Shortly after that H. amygdali colonized other leaves. For both species egg hatching was coincided in late winter however colonization and population increase of H. amygdalei were observed two weeks later than what was observed for B. amygdalinus. With the onset of warm season, both species moved from almonds to alternative hosts for aestivation. Gynoparae shortly followed by males appeared on alternative hosts in late summer and migrated to almonds. Oviparae produced by gynoparae mated with males and laid their eggs near the buds.

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In a study of aphids and their parasitoids in wheat fields of Shiraz region, the species composition, distribution and seasonal dynamics of the dominant species were monitored during 2004-5.Collections were made from 1-3 hectare fields in 10 locations within 50 Km radius around Shiraz city. Species density was estimated by counting individuals present on 40 winter wheat tillers taken at random along 2 transects 5 m apart in the fields. Eight aphid and 3 parasitoid species were identified through this survey. Rhopalosiphum padi (L.) and Metopolophium dirhodum (Wlk.) with relative abundances of 33.94 and 31.33%, Aphidius rhopalosipi De Stefani-Perez and Praon volucre (Hal.) with relative abundances of 55.53 and 39.90%, were the dominant species of aphids and parasitoids, respectively. Seasonal dynamics of the above species were also studied in Badjgah, located 15 Km north of Shiraz city. Peak populations of the dominant aphids occurred between late May and first of June 2004-5, and those of parasitoids were seen 1-3 weeks later. A comparison between seasonal parasitism of the dominant parasitoids showed significant preferences of A. rhopalosiphi on R. padi, and P. volucre on M. dirhodum. Since the total parasitism of both wasps was nearly 30% of the two aphid hosts, attention should be paid to chemical control programs of wheat pests (such as Sunn pest) so that it does not disturb the efficiency of the aphid parasitoids.

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Dates of start and end of frost based on minimum shelter temperature equal to or less than 0°C were studied in Zanjan, Ghazvin and Tehran during 1961-2000. The cause of these frosts was determined by weather parameter values at observation hours and the aid of synoptic maps. Frost series based upon last spring or first fall advection are defined and found to be random and normally distributed. The "potential growing season", defined as the interval between spring last and first fall advection frosts, is found to be 29 days in Zanjan, 23 days in Ghazvin and 10 days in Tehran longer than the "growing season" defined by the interval from last spring to first fall occurrences of minimum shelter temperature of 0°C or less. The numbers of radiation frosts in the interval between first radiation frosts in fall or last radiation frost in spring and related advection frost were counted and found that this parameter is greater in Zanjan. Frostless days between the first two fall frosts and last two spring frosts show that the lengthening of spring season with one night protection is possible for 4 days in Zanjan, 6 in Gazvin and 4 in Tehran, providing that first fall and spring last frost is radiation. Results of this study permit estimating the practicality of frost protection for specialized crops in the area of study.

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Low flow estimation and its characteristics play an important role in hydrologic studies. However, some low flow events are ignored compared with the lowest annual low flow that may have high risk. These events are taken into consideration by the use of partial duration or peak over threshold models. In this study, a 7-day low flow was applied for frequency distribution and threshold, and the lower events were considered as the number of low flow event ( ) to study seasonal variation of low flows together with two graphical methods. The results showed two major low flow seasons, and for other times of the year, the low flow events are negligible. At last, the region was divided into homogeneous groups based on seasonal variation of low flows.

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Sweet tasting glycyrrhizic acid is considered to be the most important chemical compound in licorice root. However, environmental factors affect chemical composition of licorice root including glycyrrhizic acid content. In this study, the effects of the harvesting time and location on licorice root composition were studied. Chemical composition of the licorice roots (Glycyrrhizia glabra) collected in summer and fall seasons from three locations in Fars province (Eghlid, Beiza and Doshman-Ziary) and one location from each of Kerman (Baft) and Kermanshah (Islam-Abad) provinces was determined. Glycyrrizhic acid, ash and sugar content before and after hydrolysis were measured in all samples after extraction. A combined analysis of variances was performed on data based on a randomized complete block design in six replications. The results showed that effects of harvesting season on sugar content, and the effects of location and its interaction with harvesting season on ash, sugar and glycyrrhizic acid content were significant (p<0.01). It was also found that the lowest ash content were obtained from roots harvested from Islam-Abad in summer the highest sugar content before hydrolysis belonged to roots harvested from both Baft and Islam-Abad in fall. Highest amount of sugar after hydrolysis was reported in the roots collected from Islam-Abad in Fall. Roots harvested from Beiza in Fars province in fall had the maximum glycyrrizhic acid content.

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Climate situation changes over a year cause changes in some soil characteristics and soil sensitivity to erosion. Investigation of these changes and how they impact on erosion can be of particular importance. This study investigated changes in Sediment Productivity and soil factors affecting these changes in Tiregan rangeland located in Daregaz city in Khorasan Razavi province. In this study, using the position of the upper and lower hillside of eastern and western aspects, the sampling with rain simulator was performed. Characteristic features of sediment yield including runoff threshold, runoff volume, sediment and turbidity were measured. Soil samples were taken from each sample rain simulation and features of the initial moisture content, bulk density, electrical conductivity, pH and organic matter were measured. Sample was collected with the same intensity and duration of the instrument with fixed locations, and was repeated in four seasons. In order to obtain the position and orientation of each of the parameters in the data obtained at different seasons, the combined analysis of variance test was used. The effect of each of these parameters and the difference between them were evaluated using the Tukey test, and the graphs in 2007 Excel software were plotted. The results showed that all the parameters of sediment yield during the year have significantly changed. The maximum amount of sediment production rates occurred in autumn and was gradually reduced. Its decreasing in both winter and spring can be attributed to vegetation in the area.

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