Journal of Agricultural Sciences and Natural Resources
Year:2009 | Volume:16 | Issue:2|Papers Count:9

In this study, some biological characterictics of ova (including diameter, surface, volume, ratio of surface to volume) and hydrated eggs (including diameter surface, volume, ratio of surface to volume, yolk sphere, pervitelline space and the ratio of yolk sphere to pervitelline space) was investigated in 90 specimencs of a migratory population of wild common carp into Gorganrood in 6 year classes (2+, 3+, 4+, 5+, 6+ and 7+) in March-April 2007. The range of egg diameter and the ration of its surface to volume were 0.97mm to 3.18mm and 1.88mm to 6.18mm and of hydrated eggs were 1.24mm to 3.52 mm and 1.7mm to 4.93mm respectively, that were different significantly (P<0.05) among year classes, having a minimum value at 2+ and maximum value at 7+. Yolk sphere to perviteline space ratio of hydrated eggs in wild Common carp broodstock was estimated as 2.04, indicating yolk sphere was larger than pervitelin space. Effect of broodstock age on the ratio of yolk sphere to perviteline space was significant (P<0.05) and was higher in age 3. In conclusion, female carp broodstocks with 3 to 6 age olds is suitable for artificial propagation.

The release rate of nonexchangeable K (NEK) plays a significant role in supplying available K, particularly in soils containing K bearing minerals. Information about NEK release rate in soils of Iran is limited. The main objective of this research work was to investigate the kinetics of NEK release in 4 soil orders, Aridisols, Mollisols, Alfisols and Inceptisols of Golestan Province by successive extraction with 0.01 M CaCl2 over a period of 264 h. The results showed that the amount of NEK release after 264 h ranged from 1984 mgKg-1 in Alfisols to 915 mg Kg-1 in Inceptisols. High clay content, nonexchangeable K and cation exchange capacity and also presence of potassium bearing minerals (illite and Hydroxy Interlayer Vermiculite), in Alfisols, are the main reasons for the high nonexchangeable K release in these soils. In all soils, rate of potassium release was higher in the begining and decreased, afterwards. The kinetics of cumulative NEK release were evaluated by using the Elovich, zero order, parabulic diffusion law and first order equations. Du to the lowest coefficient of determination (r2) and highest standard error (SE), the Elovich and zero order equations could not describe the NEK release kinetics. In contrast, parabulic diffiusion law and first order equations fitted to the observed data satisfactorily, indicating that diffiusion mainly controlled the K exchange. Rate constants were very different in soil samples. Which is mainly attributed to difference in particle size distribution, clay content and the type of clay minerals.

Sturgeon is the most important species in Caspian Sea. About 93% of the world sturgeon population lives in the Caspian Sea. The aim of propagation and cultivation of these fishes is to generate and improve their stocks in Caspian Sea. The use of advanced techniques for larviculturing these fishes is one of the most important aims in the industry of sturgeon cultivation. The blend of probiotic bacillus (Bacillus licheniformisi , B. subtilis, B. polymyxa, B. laterosporus and B. circulans) under the commercial title of protexin aquatic, were used for bioencapsulation of Artemia urmiana nauplii (as a living feed for these fishes).The bioencapsulated Artemia nauplii was fed by sturgeon larvae (Acipenser persicus, Acipenser nudiventris and Huso huso) and the yeast of Saccharomyces cerevisiae as probiotic, used in feeding of Persian sturgeon (Acipenser persicus) larvae by bioencapsulation of Daphnia magna. However the gained body weight in experimental treatments of sturgeon larvae had significant difference in comparison with control treatment (P<0.05). In experimental treatments, Food Conversion Efficiency was increased while the Relative Food Intake significantly decreased (P<0.05). The probiotic bacillus and yeast had significant positive effects on the Specific Growth Rate, Survival rate, protein efficiency ratio and lipid efficiency ratio in comparison with control treatment (P<0.05). The experiments indicated that the probiotic bacillus and yeast of Saccharomyces cerevisiae have the highest ability to increase the growth parameters and feeding efficiency in cultivation system of sturgeon fish.

For studying effect of natural compounds on strawberry (Fragaria ananassa L.) shelf life, after purchased from a local market, the cactus-mucilage edible coating (Opuntia ficus L.) and thymus essential oil were used. Thymus was added to Mucilage as 20 percent of total weight (w/w), to understand the interaction effects. Fruit shelf-life traits were measured on different periods of storage duration including; 0, 3, 6, and 9 days. Results indicated, fruit decay decreased as essential oil or in mixture with mucilage was applied. Further, total soluble solid and firmness in those fruits treated with thymus essential oil maintained, as the shelf-life duration extended. Application of mallow mucilage led to better fruit water conservation in comparison with control. This treatment or in mixture with essential oil cause more firmness and decrease of total soluble solid and maintaine fruit texture. Non of treatment could not affect titrable acidity and pH. Application of thymus essential oil as an antioxidant caused less fruit color disappearance and strengthened the fruit flavor. Industrail application of these treatments needs to more experiment achievements to understand effective concentration and applied procedures which in turn is a response to the consumer pressure to reduce or eliminate chemically synthesized additives in fruits.

In this experiment, the effect of Thymus vulgari, Dianthus caryophyllus and Rosmarinus officinalis essential oils in reduction of the peroxidase enzyme in some vegetables was evaluated. Pure concentration, 0.2, 0.1, 0.075, and 0.05ml/100ml of each essential oil were applied. The extracts of Lactuca sativa var.longifolia cv. Romain, Brassica oleraceae var.capitata f.alba, Brassica oleraceae var.capitata f.rabra, Solanum tuberosum and Cucurbita pepo l.zucchini were the sources of peroxidase enzyme. The results showed that the antioxidant activity of each essential oil was different with the enzyme source. The highest antioxidant activity in all concentrations is for the D. caryophyllus essential oil (P<0.01). In low concentrations, the essential oils of T. vulgari and especially R. officinalis increased the enzyme activity in C. pepo l.zucchini and L. sativa var.longifolia cv. Romain (P<0.01).

Integrated Pest Management (IPM) is a dynamic, integrated approach involving a number of control techniques to manage pest populations in an ecologically sound fashion. IPM, as one of sustainable agricultural development components, is based on synergy of empowering farmers, environmental friendly technology and integrated farm management. Effective IPM extension needs identification and analysis of related principal components with aim to policy making and planning by farmers’ participation. Along with this comment, this research was done based on survey strategy with aim to studying farmer’s practices related to rice integrated pest management. Validity of questionnaire as data gathering instrument, confirmed by selected experts and Coronbach Alpha coefficient (equal to 79%-87% range for parts of questionnaire) used to confirm its reliability. The population of this research included all rice growers in Droudzan District of Marvdasht county and a representative sample selected (n=90) by Cochran formula. According to findings of factor analyzing of farmer’s practices related to rice IPM, three components were extracted. The first factor called the farming improvement practices factor explained 26% of the total variance. The second factor called the biological practices factor explained 15% of the variances. The third factor called physicalmechanical practices factor explained 9% of the variances. These factors, totally explained 50% variances of farmer’s practices related to rice IPM.

A 42-day rearing trial was conducted to examine the enrichment of Artemia urmiana nauplii with vitamins C (Ascorbyl-6-Palmitate) in combination with unsaturated fatty acids (EPA 18% and DHA 12%) on growth, survival and stress resistance of Beluga, Huso huso larvae. Beluga larvae were distributed into five treatments at the first feeding stage and three tanks were assigned to each diet. The test treatments were as follows: Artemia urmiana enriched with HUFA+10%, 20% and 30% vitamin C (C1, C2 and C3 groups, respectively), Artemia enriched with HUFA without vitamin C (HUFA group) and non-enriched Artemia (control). All treatments were fed with non-enriched Artemia for the initial 5 days after the first feeding and then fed with enriched Artemia for 7 days. After the period of enrichment, larvae were fed with daphnia from the 13th to the 40th day. At day 40, submersion in salt water (12 ppt) was performed to evaluate larvae resistance to salinity stress. Blood samples were obtained after 24 and 48 hours salinity stress in order to evaluation of hematocrit index. Growth factors showed comparable differences between groups. The highest and the lowest growth was observed in C3 and control treatments, respectively (P<0.05). Survival rate was not significantly different between groups during experimental period (P>0.05). Mortality rate was statistically different in salinity stress after 2 days and mortalities were lower in enriched groups than non-enriched (P<0.05). There was no comparable difference in hematocrit index under stress conditions (P>0.05). These results indicated that the enrichment of Artemia with essential fatty acids and vitamin C can improve some growth and stress tolerance factors in great sturgeon (Huso huso) larvae.