Iran Agricultural Research
Year:2002 | Volume:21 | Issue:2|Papers Count:7

The modeling of water movement through soils typically requires the functional representation of soil hydraulic properties, such as the water retention curve. Among different water retention models, van Genuchten (VG) model is an appropriate one. The objectives of this study were to quantify relationships between the VG model parameters and soil physical properties and to select equations that are useful for prediction of VG model for soil water retention curve. Fifty four soil samples were used for soil water characteristics determination by ceramic plate extractor, soil particle size determination by hydrometer method, soil bulk density and soil organic matter. Multiple regressions were used to determine the relationships between m and hp (soil water suction at reflection point of the soil water retention curve) and the aforementioned soil physical properties. The results indicated that multiple regression models may be used to estimate, with acceptable accuracy, the water retention curve of VG type from soil sand content, bulk density and Organic matter percent. The proposed regression models were used for prediction of soil water retention curve for three different soils with an acceptable accuracy.

Six Holstein cows (120±20 d in milk) were used in a 3x3 replicated Latin square design to investigate the effect of different particle sizes of ground barley grain on digestibility, degradation rate and lactation performance. Geometric mean diameters of the barley particles were 0.94, 1.93 and 2.90 mm for treatments 1, 2 and 3, respectively. Diets were only different in barley particle size and all cows received diets containing 40% corn silage and 60% concentrate (DM basis) composed of 50% ground barley. The differences among dry matter intake (DMI), milk fat percentage, milk total solid percentage, daily fat yield, dry matter digestibility, urinary and ruminal pH, daily body weight change, and fecal particle size distribution were not significant. Treatment 3 caused a decrease (P<0.05) in milk protein percentage, daily milk yield and fecal pH compared to treatments 1 and 2; no other treatment differences were significant. With increasing barley particle size, fecal dry matter was increased but daily milk protein yield was decreased (P<0.05). Significant differences (P<0.05) in 4% FCM, 4% FCM/DMI daily, milk lactose yield, daily total solids yield and organic matter digestibility were observed between treatments 1 and 3. No other treatment effects were observed significant. The soluble fraction, the potential degradable fraction, ruminal degradation rate and the effective degradability of dry matter increased linearly for treatments 1, 2 and 3, respectively. It is concluded that fine grinding of barley (0.94 mm) which is commonly used on dairy farms improved OM digestibility, milk yield, milk protein percentage and production and would be recommended for feeding conditions similar to those of the present experiment.

In this paper, after theoretical extension of Veblen's theory of conspicuous consumption to production process, three methods were introduced for aggregating Veblen effects and multi-objective programming. They are: (1) using iterative weighting method to aggregate Veblen effects and multi-objective programming, (2) the social status coefficients are estimated subjectively and (3) a new objective is introduced as an index of social status. The third method was applied to a sample of Rafsanjan pistachio growers. The farmers yield was considered as the social status index. The results showed that farmers choose neither profit maximization goal nor yield maximization goal, but choose a compromise between these two objectives. Thus, trying to increase social status can be considered as one of the important objectives of the farmers. This objective influences both objective space and decision space. In the objective space a compromise between social status goal and other objectives is considered. This compromising would also change the decisions space.

Johnsongrass chlorotic stripe mosaic virus, a virus for which transmission has not been demonstrated before, was readily transmitted by injection of embryos in presoaked seeds. Transmission was achieved by inoculation of crude infected plant extracts, purified virus preparations and extracted RNA. The virus remained stable in purified preparations or plant tissues stored at -18oC with frequent thawing over many years, and in leaf extracts kept at room temperature for over 3 wk Maize, sorghum and wheat are reported as new experimental hosts of the virus. The virus was also detected in field samples of maize, Setaria sp. and Digitaria sp. by enzyme-linked immunosorbent assay (ELISA).

Due to sediment deposition, overall sediment Yield is usually less than soil loss from the soil surfaces of a watershed. The ratio of sediment yield at a watershed outlet to gross erosion within it is usually referred to as the sediment delivery ratio (SDR). Since the relationship between detachment and transport of the soil particles is not linear for each storm, simulation of SDR was performed on an individual storm basis using the ANSWERS model modified for prediction of the SDR in a small 'agricultural watershed (3.62 ha) located in south of Iran with an average slope of 2.6% and fallow conditions. Data from independent rainfall events during 1994 to 1997 were analyzed. Stepwise regression analysis showed that SDR was correlated with antecedent soil moisture content (ASM), maximum suspended solids concentration of runoff (Cmax), and mean rainfall intensity (Imean), (p= 0.001). Because it was expected that the total runoff volume would also make a significant contribution to soil erosion and SDR, the effect of the runoff volume of each storm was also tested. Further stepwise regression analysis showed not only a higher coefficient of determination (R2= 0.90) but also a higher significant level introducing other variables, Le. Runoff volume (a³0.53). In the case of introducing runoff volume as a new variable in the regression equation the model was an artificial one. However, the relationship between SDR and the watershed hydrological properties best represents the situation of soil erosion in our study area. For other watersheds of different sizes, soils, and slope characteristics, more research is necessary to investigate the relationship between SDR, watershed characteristics and climatological conditions. The overall average SDR for the watershed under study was 54.70%, which can be recommended for estimation of soil erosion an9 sedimentation from the watersheds.

Relationships between physiological blood parameters and postpartum (PP) fertility (days open, and the number of artificial inseminations required per conception, AIPC) were studied in 15 Holstein cows. Serum concentrations of total proteins, globulin, aspartate aminotransferase (AA T) and phosphorus varied significantly during the first 95 days postpartum. Number of days' open and AIPC were not significantly affected by the uterine health and parity, but younger animals tended to have shorter days open, and required fewer AIPC (P<0.08). Serum phosphorus levels were significantly higher in younger cows, and phosphorus concentration on d 35 PP showed a significant but negative correlation (r=-0.70) with day (open and AIPC. For the cows with endometritis (n=8), the correlation coefficients of days open with serum glucose (r=0.89 on d 5 PP), AAT (r=0.76 on d 20 PP) and phosphorus (r=-0.72 on d 35 PP) were significant. For normal cows, the correlation coefficients of days open with serum glucose (r=-0.80 on d 95 PP), AAT (r=-0.75 on d 35 PP), phosphorus (r=-0.81 on d 35 PP), and blood hemoglobin (r=0.80 on d 20 to 50 PP) were significant (P<0.05). The only parameter which was significantly correlated with .days open, regardless of the uterine health status, was serum phosphorus on d 35 PP. Regression equations of days open on physiological parameters were constructed. Although the number of animals in this experiment was small, but the regression equations were promising and it is suggested that more comprehensive studies should be undertaken for a better understanding of the relationship between PP fertility and physiological parameters.

In vitro storage of eight potato genotypes (four cultivars and four wild species) using either abscisic acid (ABA) (5 mg 1-1) or mannitol (3%) as growth retardant added to Murashige and Skoog (MS) medium was examined at two storage temperatures (8oC and 25oC). After 10 months, the cultures were evaluated. Compared with control, medium containing ABA or mannitol significantly retarded growth. Genotypes were significantly different for most characteristics - measured with cultivars 'Cosima' and 'Draga' superiority to others. The survival rate was significantly affected by culture medium and was the highest with mannitol treatment. Significant two-factor interactions for some characters and also different responses of cultivars and wild species for regeneration following transfer to normal condition may complicate the establishment of facilities for in vitro storage. However, MS medium supplemented with 3% mannitol showed to be superior for storing potato germplasm in vitro at room temperature.