IRANIAN JOURNAL OF AGRICULTURAL SCIENCES (JOURNAL OF AGRICULTURE)
Year:2006 | Volume:37 | Issue:4|Papers Count:22

Employment of spot sprayers will lead to less herbicide consumption and less hazard. Because of high importance attached to weed control in agriculture and to its related expenses, plenty of research is being carried out in this field. In this study 300 digital images were taken and developed from different agricultural fields in natural outdoor conditions. Images possessed a resolution of 1200x1600 pixels in reference to a field of view of 70x60 cm2. Constitutional resolution as related to the composition of three main color components in plants as well as in 7 common weed species (in Fars sugar beet fields) were extracted using discriminate analysis. Based upon the obtained relations, a suitable algorithm has been proposed through which, one is able to discriminate weeds from sugar beet plants in any form of light condition regardless of whether they are in bright light or in the shadow of either other leaves or vehicle. Correct classification rate for each one of the seven weed plants has been evaluated and discussed. Minimum correct classification rate was related to Convolvulus arvensis L. in shadow (70.8%) while maximum related to Setaria veridis L. Beauv (95.2%). Correct classification rate in the final segmentation algorithm was found to be88.5% in sunlight and 81.8% in shadow.

Soil compaction is a significant problem in many areas in mid-South and Southeastern United States. Most sandy soils of the Southeastern Coastal Plain bear a compacted layer that requires alleviating through costly annual deep tillage operations. Site-specific variable-depth tillage which modifies soil physical properties to the specific depth of compacted layer is of the potential to reduce costs, labor, fuel, and energy requirements. Although technology for site-specific tillage is available, there is a very limited amount of information available on the fuel and energy requirements of variable-depth tillage in southeastern coastal plain soils. Tests were conducted on three types of different coastal plain soils to compare energy requirement of site-specific tillage as compared to uniform-depth conventional tillage operations. Also, the effects of tractor speed, soil texture, moisture content and electrical conductivity on energy requirement and fuel consumption were determined. Energy savings of 50% and fuel savings of 30% were achieved by variable-depth tillage as compared to uniform-depth tillage in loamy sand soil types. Draft force increased as the travel speed increased in all soil types. However, tillage depth exhibited a bigger effect on the draft and drawbar power than the tractor speed. The effect of soil moisture content on draft force and fuel consumption was not significant in either loamy sand or sandy loam soil types. However, draft force and on fuel consumption were in a negative correlation with soil moisture content. Soil EC was highly correlated to soil texture (R2=0.916) as well as draft force all across the field.

The level of bacterial contamination at slaughter stage was assessed on beef carcass. Twelve random beef carcasses were selected and followed through five process stages. The samples were taken from seven sites (5x5 cm2) using swabs. Counts were made for total bacteria and also search for the following pathogens: Escherichia coli and Salmonella. Results indicated that after skinning and removal of hide, bacteria were transferred from hide to the interior of carcass. Bacterial counts reflected a cleanliness level of "acceptable". Leg muscle bore the highest and brisket the lowest level of contamination. In all carcass sites, pathogens were identified. The cleanliness level of samples taken after evisceration from inside site (flank, rib set) was judged as "excellent", with no pathogens identified. A large increase in bacterial contamination was observed after evisceration on the brisket and shoulder sites. Also the count of Salmonella and Escherichia increased. But in other sites no change was observed. After primary washing, level of contamination was reduced on most carcass sites (about 0.2 logarithmic scale). Also, after final wash, level of contamination was reduced (about 0.2 logarithmic scale). But carcass washing didn't entirely eliminate E. coli and Salmonella. Results of water microbial load determination (total count, coliform) indicated that cleanliness level was acceptable. But tests done on knives and saw showed a high level of bacteria. Pathogens isolated from these tools indicated that the ongoing rinsing and washing didn't adequately affect cleanliness.

Two methods of photoelasticity and finite element were employed to analyze contact stresses in bolted joints. Samples were made up of photoelastic materials. Photos were taken when samples were loaded with Polaris cope. Finite element models were analyzed using ANSYS 5.6 software. To verify the model, finite element results were compared with those of the experimental ones. The comparison led to an acceptable agreement between the two, with a correlation coefficient (R2) of 0.99. After a validation of the finite element model, the effect of number of engaged threads and different moduli of elasticity of bolt and nut were investigated, using ANSYS software. According to the results obtained, increasing the number of engaged threads in bolted joints resulted in a decrease of load concentration percentage in the first thread, and then smoother load distribution was observed to be accomplished. Of course, the behavior of load distribution in "bolt and nut" is not the same as in "body and stud" arrangement, but in either cases, when the number of engaged threads passed 20, this didn't affect stress distribution. For body and stud, the most uniform load is obtained when the Young's modulus ratio of body and stud is in the range of 0.5-1, while this value for nut and bolt is observed to be about 0.1.

The effects of freeze-drying on microstructural property of apple were studied. Osmotic subjection (60% w/v corn syrup solution) and blanching (80°C, 1 min) were employed as pretreatments. To investigate microstructure of dried products, SEM microscopy was applied. Investigations show no damage or collapse in structure of dried products. Osmotic pretreatment leads to production of a layer of solutes (sugars) on the surface of dried products, which in turn causes a decrease in diffusely of water molecules. It was found that blanching before osmotic pretreatment leads to beneficial effects on structural properties of dried apples.

In this research work the effect of a mixture of antioxidants and polyphosphate sodium on the shelflife of kilka in cold storage was studied. Five mixtures of BHA, and citric acid in 5 percent polyphosphate sodium were made. The concentrations of BHA and citric acid in polyphosphate were 1.5, 3.5, 0.02 and 1.5 and 3.5 percent respectively. The samples of fish were divided into two lots. The first lot was dipped in each mixture for 10 minutes and the second for 60 minutes. The reference samples were prepared without being dipped into any mixture. Then all the samples were frozen at-40°c by a plate freezer and stored in a cold store. According to a time schedule each month for six months the PV, TVN, total microbial count and organoleptic tests were carried out on each one of the samples. The Results of organoleptic tests showed that samples containing 1.5 and 3.5 percent of BHA were not acceptable according, to their tastes and flavour scores. The results of PV, TVN. total microbial count for refrence sample increased from 0.06 to 3.2 meq/1000gr, 9.8 to 16.8 mg/100 gr and total count of bacteria fell from 68x 102 to 50x 102 cfu/gr after four months. On the other hand PV, TVN for C1, C2, C1 and B"1 and B"2 samples increased from 0.06 to 2.15 meq/1000 gr, and 9.8 to 16.5 mg/100gr. But total count of bacteria fell from 17x102 to 3x101 cfu/gr. after six months in cold storage. The results of this study indicated that mixtures of 0.02 BHA in 5 percent polyphosphate give the best results for keeping frozen kilka in cold store for duration of six months.

Cold press method and supercritical fluid extraction (SFE) of bitter orange essential oil were studied using fresh bitter orange peel as raw material and CO2 as solvent. The influence of extraction method (cold press or SFE) on the Limonene extraction yield was found out. Moreover, the influence of different operation conditions was analysed in the pressure range from 100 to 300 atm and at temperatures 35, 45 and 55°C for a static time of 20 minutes. In these experiments, the duration of dynamic time was varied from 15 to 35 minutes and the concentration of co-solvent (methanol) was increased from 0 to 10% (V/V). Limonene was the principal component extracted, the optimum conditions for extraction being P=300 atm, T=45°C, td=15 min and Cco-solvent=10% (V/V). In these conditions, the yield of limonene extraction and the composition of extracted essential oil are different for cold press method and SFE. Comparing the two methods, SFE better resulted on the Limonene extraction yield.

Eolian sediments are comprised of two groups of loess and eolian sands. They, in distances close to origin, are exposed as sand dunes and then become apparent in the form of loess. Loess sediments are usually yellow but grizzly and contain silt size materials. Iran loesses, have mostly been located in its northeast regions. The purpose of this research his to investigate their morphoscopical properties and also, to determine the continuity among the layers of studied sections in which the sedimentation conditions. Have probably been different The selections, are located in two types of climates of the Ghapan region (semiarid and humid) in southern Gorgan. The different stages of this research consist of field operations, chemical tests, brief identification of loess components in sand part (greater than 53 microns) and a morphoscopical study of Quartz grains. Investigation concerning the components of loesses in Ghapan region indicates that gypsy-clayey aggregates and the primary minerals are abundant, where as in the southern Gorgan regions, secondary calcareous-clayey aggregates are the dominant. Morphoscopy research concerning quartz mineral indicates that a high percentage of the samples (greater than 70 percent) fall in angular to semi angular class which indicates that these sediments have not been moved a far distance from their source regions. From the view point of surface texture, quartz grains are mainly (about 75 percent) aureole and partially (about 25 percent) blur. The form of their aureole (in a high part of the sediments) indicates that they have originated from ancient river beds and have not been transported so far a distance from their origins. Their blurring is generally caused by color blending by Sesquioxides and secondary calcareous effect. That indicates a relatively long time of sediment accumulation as well as the effect of varied climatic conditions, along with salts leaching from the upper horizons and their being deposited in lower horizons.

During two growing seasons in years 2000 and 2001, soybean leaf samples suspected of soybean mosaic virus were collected from various soybean fields in Mazandaran and Gorgan, Northeast Iran provinces. Soybean seed samples obtained, were sown in pots to investigate SMV infections under greenhouse conditions SMV infections in the field were quite varied and thus could not be used to demonstrate the rate of SMV infection. For propagation of the virus, several susceptible test plants such as different soybean cultivars were inoculated and employed in the greenhouse study. In addition, serological tests, using specific polyclonal antisera against SMV, were employed to detect the virus in the samples. SMV was purified applying two different methods. Electron microscopy showed the virus particles to be filamentous and rod shaped. The best serological agar media in double diffusion test included 0.8g agarose, 0.85 g NaCl, 0.25g SDS and 0.025g NaN3 in 100ml distilled water. During the course of the study, SMV was found to be the most predominant virus in the area, and mosaic was the most common symptom of SMV infection. The distribution of SMV was similar in either of the two provinces. In a few soybean fields in Gorgan (Hashemabad) and Mazandaran (Dashte Naze, Neka, Gaz, Jooibar and Badeleh) provinces, SMV infection was extremely serious. Only 10-15 percent of seeds sown gave rise to infected seedlings. Western immunoblot analysis revealed a single coat protein subunit of about 28 kDa in the purified viral protein as well as in SMV infected leaf samples.

Celluloses are enzymatic proteins which hydrolyze cellulose polymers to smaller oligosaccharides, cellobiose and glucose. The aim in this study was mainly to determine the parameters which affect cellulase activity in semiarid calcareous soils of Hamadan, northwestern Iran. The lands have been utilized as pastures; have been under deciduous and coniferous forests, and as well have been used as dry and irrigated farms for many decades. Some farmlands have been irrigated with river water whereas some with untreated municipal wastewater. Sampling was carried out at a depth of 0-30 cm in a completely randomized design with an unequal number of repetitions. Some physical, chemical and biological soil properties were assessed employing standard methods. The results revealed that cellulase activity in the differently utilized and managed soils was significantly different. It ranged from 0.170 mg glucose released, g-1 soil min-1, in dry farmlands to 0.384 mg released, g-1 soil min-1, in deciduous forests. Cellulose activity exhibited a significant and positive correlation with soil OC, TN, C/N ratio, substrate induced respiration, basal respiration, acid and alkaline phosphates, but a significant and negative correlation with soil pH. Among soil microbial populations analyzed, cellulase activity exhibited a very significant correlation (p<0.001) with soil fungal population. It may be concluded that cellulase activity in calcareous soils is mainly correlated with those soil factors that affect microbial activity.

Residual energy intake, defined as the difference between actual energy intake and that predicted on the basis of requirements for maintenance, milk production and body weight change, is a measure of feed efficiency. Genetic parameters of residual energy intake, and its correlations with feed intake and yield traits were investigated, using 3503 monthly records of 906 Holstein lactating cows in three herds. Different requirements of energy were estimated using models from NRC. Genetic parameters were estimated through multivariate analysis by derivative free approach of restricted maximum likelihood algorithm, fitting an animal model with fixed effects of herd-year-season, parity number and stage of lactation, as well as random effects of animal additive genetic, permanent environment and residuals. The estimated heritability of residual energy intake was 0.21±0.02. Results indicated that selection against residual energy intake might moderately improve feed efficiency. Moreover, residual energy intake could be combined with other traits in a selection index for improving both yield and feed efficiency.

Land leveling is one of the basic and costly phases in design and construction of irrigation and drainage projects. Nevertheless, methods, which have been proposed and used so far for land leveling, in addition to being time consuming, they do not provide the designer with the required accuracy. Accordingly, relatively high uncertainties arise in estimating the earthwork, which might adversely affect the project assessment. In this paper a new approach, based on employing triangular mesh was developed for land leveling in which the Newton-Raphson method was applied for determining the optimized planning level. The results of the proposed method were compared with those of the traditional methods, using two cases for which the analytical solutions exist. It was revealed that the proposed method drastically increased the accuracy of the planing level, area, and earthwork volume assessment. This would have close impact on the project cost as well as on the irrigation efficiencies.

This study was conducted to evaluate the ability of a total of 158 bacteria isolates collected from soybean rhizosphere against soybean damping-off disease caused by Phytophthora sojae, using the dual culture method. Sixty-six strains were identified as Gram positive, 80 isolates as fluorescent pseudomonads and 12 isolates as Gram negative. Among these bacteria, a total of 100 strains that caused growth inhibition zone of 3 mm or more against P. Sojae were chosen for greenhouse studies to control damping-off. Each experiment was conducted in a factorial trial with two factors representing soil and seed treatments. Results revealed that isolates B3, B80, B12, B43, B51, B63, and B64, using either application method, displayed effects similar to or higher than Ridomil fungicide in reducing the disease percentage. In soil treatment method, isolates B3, and B43, caused 70.84% reduction in damping-off whereas B63, and B51, 54.34%. Isolates B12, B80, and BM exhibited 66.67, 54.17, and 50% decline in disease development, respectively. In seed treatment method, isolates B43, B51, and B63 reduced damping-off by 50%; whereas B3, B12, B80, and B64 caused 62.5, 58.34, 45.84, and 37.5% decrease in disease occurrence, respectively. Application method had different effects on disease suppression.B3 and B12 isolates applied as soil treatment had a significantly higher disease control effect as compared to seed treatment. B43, B63, B51, B80, and B64 strains produced similar effects in reducing damping-off, regardless of the application method employed. Regression analysis showed a high degree of correlation between soybean root colonization ability by antagonists and disease control in the two application methods used. Bacteriological tests identified B3, B12, and B80 as Bacillus spp., whereas B43, B51, B63, and B64 were fluorescent Pseudomonas spp. In determining the effects of volatile metabolites produced by antagonistic bacteria on fungal growth, it was found that all three Bacillus strains inhibited mycelial growth of Phytophthora sojae in vitro. The culture media, PDA and NA containing 2% (w/v) glucose, influenced the inhibitory activities of Bacillus strains. Culture filtrate of individual Bacillus isolates inhibited mycelial growth of P. sojae in Petri dishes. All four fluorescent pseudomonades generated antibiotic compounds as well as volatile metabolites that caused a significant inhibition of mycelial growth of P. sojae. B43 and B63 isolates produced siderophore activity on King's B medium. In studying hydrogen cyanide production by antagonists, only Pseudomonas strains were positive producers. Non of the Bacillus isolates produced any HCN. The bacterial colonization experiment showed that B3, B12, B63, B43, B51, B80, and B64 isolates increased their populations on soybean root system by 814, 771, 703, 700, 694, 655 and 541 folds, respectively.

Mythimna genus moths are some of the most important pests of gramineous plants' especially cereals, that can substantially reduce crop yields by feeding on leaves and on ears. The larvae, called "armyworm" with gregarious feeding at different larval instars and in favorable conditions can destroy a rice field within a short time. Their damages are seen periodically and in some years in the west of Mazandaran are such that can cause irreparable damage to rice fields. In comprehensive studies on population dynamics of Mythimna species during 1999 -2001, three species namely, Mythimna unipuncta (Haworth), Mythimna pudorina (Denis & Schiffermuller) and Mythimna vile/lina (Hubner) were collected and identified. Among them, M unipuncta as the dominant species can cause the main damage. Larval and adult population fluctuations showed that M unipuncta bears three generations per year with the maximum larval activity occurring in July, August and September. The second generation larval activity was the highest which can cause the greatest damage. Developmental period under insectariums conditions was 48.27, 37.48, and 44.44 days for first to the third generations, respectively. Head capsule size measurements indicated that each generation has six larval instars. Cumulative survival is gradually reduced from first larval instar, so that only a few number of larvae can reach adult stage. Obtained data from Robinson light trap showed that 3 flight peaks, in early July, middle of August and September, can be seen that respectively belong to the first, second and third generations of pest.

Stress cracking susceptibility during drying process of two varieties of Khazar (Long-grain), and Hashemi (longer-grain) rice was investigated. Thin-layer drying tests were conducted with air drying temperatures of 35°C, 45°C, 55°C and 65°C. Stress-cracking development reactions in the endosperm of rice kernels was investigated during drying with various temperatures of drying air and in passing from moisture contents of 18%, 15% and 12%(w.b.). Stress-cracking index (SCI) was applied to quantify stress cracking susceptibility (severity of damage to endosperm) induced to kernels by drying. The drying air temperature and the removal of moisture content have important effects on the development of stress cracking. For Hashemi variety, from 45°C on, and for Khazar variety a moment lower than that (by increase in temperature), SCI increased intensively. To attain the moisture content of 15%(w.b.), either of the varieties could be dried with higher temperatures without inducing any high SCI. Air drying temperatures of 55°C for Hashemi variety and a moment higher than 45°C for Khazar variety were recommended, Then the drying process should continue with the lowest possible temperature. Khazar (long-grain) variety was more susceptible to fissuring than Hashemi (longer-grain).

Four hundred isolates of Pseudomonas were isolated from rhizosphere of wheat, their antagonistic activities against teliospore germination of Tilletia laevis race L10 being determined. Seventeen representative isolates were selected for further investigation. Production of antifungal metabolites, volatile compounds and sidrophore by bacterial isolates were the investigated isolates. Selected bacterial isolates based on the biochemical, physiological, nutritional characteristics and also based on a comparison of electrophoretic profiles of cell protein, were identified. Using phenotypic features determination and protein electrophoretic pattern was compared cell free. Metabolites of Pseudomonas fluorescens bioI B9, Piluorescens bioIII C21, P.fluorescens bioV D23, and volatile compounds of Piluorescens bioIII D22, Piluorescens bioI B9, decreased teliospore germination. Sidrophore of Pputida bioA El6 and Piluorescens on king's B medium inhibited growth of Geotrichum candidum. In greenhouse experiments, Piluorescens bioIII D22 reduced common bunt significantly (P<0.05). In all cases skimmed milk formulations were more effective than application of bacterial cell devoid of this additive.

The effect of two treatments: Time of taking cuttings and two plant growth regulators IBA and NAA (0, 2000, 4000, 5000 & 8000 ppm) along with two application methods: Talc and quick dip, on three species of old spruce trees (Picea glauca 'Albertiana Conica', P. pungens 'Koster' and P. abies 'Ohlendorfii') were investigated. A factorial in CRD (Complete Randomized Design) base with three replications was employed. The effect of time on rooting, callusing percentage, and root length was accompanied by significant differences. The highest rooting percentage (24.4%) was obtained at 8000 ppm IBA. The highest root length mean was obtained at 5000 ppm IBA with no significant difference observed with 8000 ppm. The highest number of adventitious roots was obtained by applying 5000 ppm IBA with no significant difference observed with 4000, 8000, and 0.5% in IBA Talc. Applying 2000 ppm IBA caused the highest percentage of callused cuttings in "glauca" in mid February.

Spurge hawkmoth Hyles euphorbiae L. is known as a monophgous agent living on Herbaceous species of Euphorbia spp. A biological study of this moth in western parts of Orumieh Lake, Iran was conductedduring 2002-2004 in field, as well as in laboratory conditions. Field observations showed that spurge hawkmoth feeds on the leaves, buds and soft stems of Euphorbia macroclada Boiss. and E. denticulate Lam., although in no-choice host specifity tests in laboratory conditions, the larvae were successfully reared on E. seguieriana Nrck. & Spach., E. heteradena Jaub as well as E. boissiriana Prokh. Spurge hawkmoth lives two generations in western parts of Orumieh Lake. The first generation was observed to last from late April to mid July, the second one from mid August through late October. Maximum number of eggs in a cluster was 62, the average being counted as 19 eggs per cluster. Females, on average, laid 162 eggs per individual, but potential fecundity was evaluated as 191 per individual. Laboratory and field studies revealed that incubation period of eggs at constant temperature of 18±0.5°C (in laboratory) was 9±0.5 days and in daily mean temperature of 14.7 and 24.3 (in field) 12±1 and 7±1 days, respectively. This moth bears 5 larval stages. Larval development period in daily mean temperature of 19.4 and 24.1°C were 23±2 and 19±2 days, respectively. Studies on parasitoids of H. euphorbia showed that the larvae were parasitized by two species of thachinid flies including Exorista grandis (Zetterstedt) and Masicera sphingivora (Robineau-Desviody).

Genetic parameters and genetic trend of productive life (PL) in Iranian Holsteins have been estimated using survival analysis techniques. A Weibull mixed sire-maternal grandsire survival model was used to estimate genetic parameters and genetic evaluation of sires for productive life of their daughters. Data from 423578 lactation and 172551 productive life of cows with first calving from 1987 to 2004 were used for the analysis. 44.54% of data was right censored. Length of productive life was defined as the number of days from first calving until culling or censoring. Estimated heritability were 0.063 and 0.180 on log and original scale for functional and 0.059 and 0.164 for true productive life, respectively. Herd-year-season, milk production, lactation and stage of lactation, Holstein Friesian gene percentage and age at first calving had very significant effect on PL (p<0.01). Relative risk of culling increased as age at first calving increased. The most important change in log likelihood was observed for milk production. Risk of culling for low producing cows (milk production below 1.5 standard deviation of herd-year average) were four times greater than that for high yielding cows. Predicted transmitting ability for functional productive life, expressed as relative risk ratios and ranging from 0.45 to 1.74, indicates that the risk of culling for daughters of the worst sires was four times greater than that for the best sires and nearly 80% greater than that for the average sires. A large variation was observed among sires for their daughter's longevity, thus selection of sires might result in suitable genetic gain. Estimated genetic trend was 0.06 (genetic standard deviation) per year.

This study was conducted to determine the most effective biological stage of root knot nematode (Meloidogyne javanica) that can intensify disease severity of Fusarium oxysporum f.sp. lycopersici, the vascular wilt pathogen on tomato roots, as well as to investigate changes in total phenol content along with its relation to disease resistance. Total phenol content was evaluated in tomato plants (cv. Roma VF) inoculated with the fungus and nematode separately and in combination during an II day- period after inoculation and then compared with the noninoculated plants (control). Tomato cv. Roma VF is resistant to F.o.f. sp.lycopersici whereas it is susceptible to M.javanica. The results of the study indicated that fungal inoculation of tomato roots induced phenol production significantly. Phenol content increased at three days-post inoculation (dpi), and reached a maximum level at ninth day. Nematode induced phenol production in tomato roots occurred rather slowly as compared to the fungus induced. Phenol content reached a maximum level at SiXth dpi during the nematode infection. When changes in phenol content were compared during the various biological stages of nematode, 15 days post penetration of nematode was found to be the most effective time for reducing induction (suppression) or synthesis of total phenol against the fungal infection. Other time intervals at which such changes were compared included 4 and 21 days post penetration of nematode and simultaneous inoculation of fungus and nematode. Therefore it can be suggested that nematode parasitism and nutrient uptake somehow suppresses phenol synthesis, induced by the fungus, in tomato roots.