JOURNAL OF AGRICULTURAL SCIENCE AND SUSTAINABLE PRODUCTION
Year:2003 | Volume:13 | Issue:2|Papers Count:8

Artificial drying of rough rice products is one of the most common methods of preservation. Rapid drying can increase brittleness and induce internal cracks which predispose the product to breakage during subsequent activities. The drying process must be designed and controlled so that design guidelines which reduce or minimize drying damage to rough rice products can be established and improved. This requires an accurate description of the drying mechanism. A finite element formulation and solution of a set of linear and nonlinear coupled conductive heat and diffusive moisture transfer equations to improve grain drying simulation of axisymmetric bodies is presented. Axisymmetric linear triangular elements with two degree of freedom per node are used to discretize the rice grain in both models. One medium grain, 'Cepidrod', was used. During the thin layer drying, temperature was measured every five second. Relative deviations of predicted values for linear and nonlinear models from measured data were calculated. The deviation obtained for nonlinear model was less than the linear model. Nonlinear model was improved by changing coefficient of latent heat of evaporation specific heat equation. The simulated temperature profile and gradient are directly usable for stress cracking analyses of rough rice. The results of the finite element analysis can be used for rough rice quality evaluation and drying simulation studies.      

Antagonistic effect of Trichoderma harzianum ( J1 and J2 ) and Trichoderma harzianum ( J3, J4 and J5 ) isolated from the soil of sunflower field of Urmia and Khoy, respectively, and T. virens, T. harzianum (J6), T. viride (E1) and T. viride (E2) isolated from edible fungi (Agaricus bisporus) on the causal agent of crown and root rot of sunflower ( Sclerotinia minor) were studied in vitro. In order to do so, mycoparasitism mechanisms, competitive saprophytic ability, colonization ability, inhibition ability of volatile antibiotic and non- volatile (Culture filtrate) of the given isolateson S. minor were studied. The study indicated that all the isolates disintegrated hyphae of S. minor through antibiosis mechanism. In competitive saprophytic ability test (by means of dual culture method), T. virens showed better effect than the other isolates. After 4 days it covered the whole colony surface and prevented from forming sclerotium. In colonization ability test, T. virens and T. harzianum (J1) on 3-day and 14-day colonies of the pathogen, respectively, performed better than the rest. T. virens coverd the whole colony surface after 4 days and prevented from forming sclerotium of S. minor and T. harzianum (J1) covered the whole sclerotia after 5 days and destroyed them after 10 days. In volatile antibiotic test (by means of superposal petri-dishes method), T. harzianum (J1) was more effective to inhibit the mycelial growth of S. minor by 90.42%. In nonvolatile antibiotic (Culture filtrate) effect test on inhibition of mycelial growth and myceliogenic germination of sclerotia, T. harzianum (J6) was more effective to inhibit the mycelial growth by 86.47%. It was delayed the myceliogenic germination of sclerotia of S. minor better than the other isolates.      

Fifteen populations of the sweetpotato whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) from Ahwas, Esfahan, Ilam, Bushehr, Tabriz, Tehran, Ramsar, Rasht, Semnan, Shiraz, Kashmar, Kerman, Gorgan, Macko, and Yazd were morphologically studied using Scanning Electron Microscope. The morphological characteristics of fourth nymphal instars were studied considering the presence or absence of anterior submarginal setae, length and width of anterior and posterior wax margins, length of dorsal setae, presence or absence of posterior submarginal setae, length of caudal setae, and width of thoracic tracheal folds. The studied characteristics on adult males were the number and diameter of dorsal (discoidal) disks. Except for the diameter of dorsal disks, significant differences were observed between populations for other morphological characteristics. Morphological comparisons indicated that, it is possible to identify the different biotypes of B. tabaci through morphological characteristics. Therefore, biotype B (Bemisia argentifolii Bellows & Perring) exists in the Southern regions of Iran including, Ahwaz, Esfahan, Shiraz, Kerman, Yazd, and Bushehr as the dominant biotype, but this biotype does not present in other regions. The studied differential morphological features of various populations was  resented in tables and microscopic photographs.      

Anise is one of the most important medicinal plants which is used in drug and food industries. In this study anise was cultivated for the first time in Tabriz and the effects of five irrigation treatments: I1 = irrigation was omitted during stem elongation, I2 = irrigation was omitted during the stem elongation and grain filling stages, I3= irrigation was omitted during umbel appearance, I4= irrigation was omitted during grain filling period, and I5=irrigation in all growing stages (control), were studied on three sowing dates (April 4, 16 and 29) in a factorial experiment. The experimental design was RCBD with three replications. The results showed that essential oil percentage of seeds was affected significantly by sowing dates and irrigation treatments. So the seeds was obtained from third sowing date had lower essential oil than from the other two dates. However, irrigation disruption in different growth stages increased the essential oil percent. The analysis of the HPLC chromatograms of essential oils showed that anethole content which was 85.81 percent in first sowing date, was reduced significantly to 64.27 percent in the third sowing date. In different irrigation regimes the I1 and I2 levels had the highest anethole content, while I4 and I5 levels contains the lowest anethole percent. Mean essential oil production ranged from 10.12 to 23.74 lit. ha-1for D3 I2 and D1 I5 treatments, respectively. The essential oil and anethole contents in seeds harvested at the waxy stage (physiological maturity), were higher as compared to earlier (in the milky stage) or later (in the ripening stage) harvestings.      

In order to study the planting date and growth habit of bread wheat (spring, facultative and winter types) and increasing crop production by recommending proper growth habit for cold dry lands, this experiment was carried out in split plot based on RCBD design with 3 replications for 3 years in Maragheh and 2 years in Sanandaj regions. The main plots (Factor A) were planting dates and the subplots were bread wheat cultivars (9 cultivars and four lines) with different growth habits. The effects of location, planting date and wheat cultivar and also planting date × cultivar interaction on grain yield were highly significant (α=%1). The highest mean yield for two years was obtained for Maragheh (1.835 t/ha), first planting date (1.702 t/ha), and Sardari cultivar (1.891 t/ha). Regarding the interaction of cultivar by planting date, Sabalan produced highest grain yield of 2.103 t/ha at the first planting date. Results of Orthoghonal comparisons of mean grain yields for two years and two locations showed that the yield of winter types was 1.648 t/ha, that was significantly different from facultative (1.517 t/ha) and spring (1.246 t/ha) types.      

The present research was carried on to investigate the effects of five various methods of irrigation timing on alfalfa (Medicago sativa L.) hay production at farm research station of Univ. of Tabriz in Karkadj. Irrigation timing methods as irrigation treatments were: irrigation at 50% available soil water depletion in root zone (T1), irrigation at 50 kPa soil suction in 30 to 35cm depth (T2), irrigation at 1500 kPa midday leaf water potential (T3), irrigation when foliage and air temperature difference approached to a particular predicted value (T4), and irrigation when cumulative daily crop evapotranspiration, as predicted from a class A pan evaporation, approached to 50% and 70% of root zone soil available water (T5 and T6).The difference in hay production (wet and dry matter) was statistically significant at 1% level among the treatments. T1 treatment produced maximum yield of 3.90 and 4.20 tons.ha-1 in the second and third cuttings, respectively.T6 had lowest yield of 3.11 and 3.55 tons.ha-1 respectively. Apparently delaying irrigation up to 70% soil water depletion resulted in water deficit and lower yield. Water consumption reached to its maximum level also in T1 treatment, 3645.5 m3/ha for the second and 4638.7 m3.ha-1 for the third cuttings; the corresponding figures were 2209.2 and 3468 m3.ha-1, respectively for T6. The difference between treatments for water use efficiency (dry matter produced per m3 of irrigation water) was statistically significant at 5% level of probability only for the second cutting. Maximum and minimum values were 1.5 and 1.1 kg.m3 in T6 and both T1 and T3 treatments respectively. Considering only yield production, irrigation at 50% soil water depletion (T6) may be regarded as the best one among the other treatments. From water consumption and water use efficiency aspects T6 treatment would be preferred.

A study for the identification of seed alfalfa pests and their life cycle was carried out in 1996-1999 in Hamadan Province. The results showed that, the most important and destructive species were Lygus rugulipennis Popp., L. pratensis L., L. gemellatus H. S., L. punctatus Zett, Adelphocoris lineolatus Goeze (Miridae), Apion aestivum Germer (Curculionidae) and Bruchophagus ruddi Gassakovsky (Eurytomidae). The population density of the tarnished plant bugs including L. pratensis, L. rugulipennis and alfalfa tarnished plant bug, A. lineolatus were high. Their feeding on flowering stage caused flower shattering to an extent that only, the axes of flowers were left. All of Lygus species overwintered as adult under tree bark, dead plants or in marginal weeds of alfalfa fields, whereas A. lineolatus overwintered in alfalfa stems as eggs. In early spring ,with the enviromental temperature rising up to 9.5°C, the overwintering Lygus species appeared and upon slightly feeding and copulation, laid eggs in stem of host plants, while A. lineolatus appeared at 20°C. These species were abundant at flowering stage of alfalfa plants at the second cut and thus caused the highest damage in this stage. The study revealed that the species had two complete generations in Hamadan Province.