JOURNAL OF AGRICULTURAL SCIENCE AND SUSTAINABLE PRODUCTION
Year:2008 | Volume:17 | Issue:4|Papers Count:19

The Palmer Index reckons as a returning point in the evolution of the drought quantifying models, that in spite of passing four decades since the introduction, its special procedure and properties justifies its utilization. This index is usually addressed as a water budget accounting method for moisture anomaly estimation, yet its unique classified technique has been occasionally faced with brief indications and inaccurate deductions. Therefore, scrutinizing the analysis section of events intensity and duration throughout the drought severity index (PDSI) calculations (classified process) is essential for theoretical and operational purposes. This subject was taken into account in the present article for more practicality of the superior capabilities of the index. Accordingly, the results can be summarized at the following headings: 1) deriving the generalized structure of the classification equation, via introducing an innovated neutral intensity, 2) explaining its analytical extraction for both of the excess and lack of moisture, which is required to adjust the duration factors regionally, 3) identifying the effect of categorization on this factors and on the starting or ending event analysis, also providing an opportunity for new systematic suggestions about the classes, 4) describing the backtracking procedure that is fairly a complex part, as well as, making it applicable even for the other indices apart from the PDSI and 5) making preparation-to improve proper handling of the procedure, and expanding its development and modification or improvement potential.

Construction of stilling basins downstream of hydraulic structures is a common tool to dissipate the excess energy created by exit supercritical flows from the outlets. The length of the stilling basin and its construction costs are the factors which should closely be considered by designers to select the most economical structure. Saint Anthony Fall (SAF) stilling basin is one of the compact and short length pools which are utilized in downstream of high velocity exit flows. The efficiency of energy dissipation of this type of stilling basins would be too high despite to the short length of the pool which is the consequence of appurtenances encountered with this basin. Generally, to design this stilling pools the average flow characteristics (such as mean velocity, hydrostatic pressure ,...) are used which reflects some uncertainties due to presence of high turbulent and fluctuating flow in the reach which is to be considered for careful clarifications. In this research a stilling basin of SAF type has been constructed in a glass walled flume and electronic devices been used to take the precise measurements of actual pressure prevailed around the chute blocks of the basin. The results showed that the mean pressure is not in accordance with hydrostatic distribution and varies inversely with entering supercritical flow and directly with submergence ratio of hydraulic jump formed in the basin. It was also revealed that the variation of mean pressure at different faces of the chute blocks follows a different trend at each face.

Risk is an important and effective factor in farmers' decision making process and one of the most important factors in determining the diffusion rate of new technologies among farmers. So, recognizing the sources of farmer's risk and factors affecting them may be a proper guide in selecting and applying the prospective technologies in agriculture. In this study, farmer's risk perception from various sources was studied for a sample of citrus producers from Jahrom region. To investigate the factors affecting farmer's risk perception, an ordered probit model was estimated using maximum likelihood estimation (MLE) method. The results indicated that access to water and also crop freezing are the most important sources of farmer's risk. The results also showed that, acreage, investment credit and participation in the extension course have a negative effect on access water as a source of risk. On the other hand, adoptions of crop freezing insurance, receiving investment credit, and participation in extension course have a negative effect on freezing as the other source of risk. The negative signs of these sources of risk shows that increase in above variables will decrease the probability of access to water and crop freezing as sources of farmer's risk. According to the results, it is suggested that government play a key role in extenuation education and over facilities such as paying credit to farmer. On the other hand, since acreage has a negative effect on dependent variables, therefore, consolidation of farms will decrease this kind of risk.

An experiment was conducted to asses the effect of nutrient solution EC on growth, essential oil concentrationand composition in peppermint grown in hydroponics. Four levels of EC (0.7, 1.4, 2.8, 5.6 dS m-1) achieved by adding all macronutrients to the Hoagland's solution were used to the plants. The experiment was arranged in randomized complete block design with three replications. The result showed that vegetative characteristics in terms of fresh and dry weight were affected by solution EC, so that the highest fresh and dry weight was observed in EC 1.4 dS m-1. Increased solution EC (5.6 dS m-1) reduced the biomass production by 40%, as compared to 1.4 dS/m. The concentration of K and P was increased as the solution EC increased, however, no changes of N concentration were observed. The maximum and minimum oil content was obtained in 1.4 and both 0.7 and 5.6 dS m-1, respectively. Oil content was decreased by 35% as the solution EC increased from 1.4 to 5.6 dS m-1. The composition of essential oil was changed in various solution EC. It consisted of 23 compounds in which Menton, Menthol and Menthophoran constituted the main composition. Increasing the EC from 1.4 to 5.6 dS m-1 reduced the concentration of Menton, however, both Menthol and Polygon concentrations were increased. In addition, the concentration of Beta-Caryophyl in and Beta-Cobeben was increased as the solution EC raised. The results led to conclusion that EC manipulation can be used to change the composition of essential oil. Moreover, the EC of 1.4 dS m-1 according to Hoagland solution could be an optimum value for obtaining higher concentration of oil and proper growth of peppermint in soilless culture.

Salinity effects involve osmotic stress, ionic imibalance and ion toxicity. Increasing calcium in root medium could reduce Na+ uptake and through reducing Na+/K+ ratio in plant, would increase crop growth. In order to study these effects, an experiment with two genotypes G12 (salt tolerant) and G3 (salt sensitive), three levels of salinity (control, 100 and 200 mM NaCl) and three levels of calcium (0.5, 5 and 10mM CaCl2) was conducted at hydroponic culture media. Twenty three days after seed planting, salinity treatments were imposed, then experiment was continued until 3 weeks. At 0 and 21 days after treatments imposed, samples were taken from shoot. When salinity increased, shoot and root dry weight, leaf area index, K+ and Ca2+ concentration of root and shoot, K+ concentration of upper and lower leaves of main stem, water potential of flag leaf were decreased, but Na+ concentration and Na+/K+ ratio of root, shoot, upper and lower leaves, proline accumulation were increased. In terms of shoot Na+ concentration, no significant difference was observed between G12 and G3 at 0 day, but G3 at 21 days after treatment, significantly transmitted more Na+ to the shoot.Adding calcium to root media reduced salinity effects, thus salt tolerance was enhanced. For example, addition of 10 mM CaCl2 to 200 mM NaCl treatment decreased Na+/K+ ratio of root and shoot, upper and lower leaves of the maiIl stem, but increased Ca2+ concentration of shoot, water potential of flag leaf, proline accumulation, and shoot dry matter as compared with 200 mm NaCl alone. The tolerant genotype (G12), compared to the sensitive genotype (G3) , showed more salinity tolerance through translocating less Na+ to shoot, more Na+/K+ ratio, absorbing more Ca2+ and K+, producing more organic compounds and maintaing higher water relations.

A split-split-plot experiment with randomized complete block design in three replications was conducted in 2004 at the Research Station of the Faculty of Agriculture, University of Tabriz, Tabriz, Iran, to investigate the effects of water limitation on oil and protein accumulation in soybean seeds. Irrigation treatments (I1, I2, I3 and I4: irrigation after 6±3, 8±3, 100±3 and 120±3 mm, from class A pan, respectively) were assigned to main plot, two soybean cultivars (Zane and Huck) were allocated to the subplots and harvest stages with six day intervals were considered as the sub-subplots. The results indicated that percentages of oil and protein in the seeds were not significantly affected by water deficit at different harvests. However, both oil and protein output per unit area were significantly reduced, as water deficit increased. By increasing mean 100 seeds weight, percentage of oil content decreased, but percentage of protein content increased. In general, it was concluded that soybean oil and protein production per unit area under full and limited irrigation conditions could be improved by increasing seed yield via selection of high- yielding varieties.

In order to evaluatecorn-pumpkinseed (Cucurbitapepo var styriaca) intercropping,field experimentswere carried out in Kermanshah, Iran, in two years (2003-2004). The experiments were accomplished as factorial based on randomized complete block design with three replications anchored in additive series. Factors were as corn density (5, 6, and 7 plant m-2) and pumpkinseed density (zero, one, two, and three plants m-2).Although there was a significant increase in grain yield in both years, when corn density was increased in sole cropping, but the trends were not similar. In intercropped plots, increase in pumpkinseed density, had no significant effect on grain yield of corn, for one and two pumpkinseed plants m-2, but at the three plants. m-2 the grain yield of corn decreased significantly. Intercropping had no significant effect on 1000-kernel weight of corn. Number of seeds per ear was affected by intercropping with pumpkinseed more than other yield components and decreased when corn plant density was increased, similar to sole cropping. There was no significant difference between sole and intercropped treatments for ear, stem, leaf and biomass weight as well as HI.

In order to evaluate the effects of sowing date and plant density on the yield of soybean lines, a research was conducted at Miandoab Agricultural Research Station. The experimental design was factorial with three replications and repeated for two years (2001-3). The sowing date included three dates (April 21, May 15 and May 20) and sowing density included three levels of 30, 40 and 50 plants per m2 with two advanced soybean lines from the crosses of Williamsx Chippewa and Williams x Collombus. During the growth period all agronomical characters were measured.Combined analysis of varianes indicated that the effects of plant density, sowing date, line, year x sowing date, plant density x line and sowing date x line x year on grain yield were significant. At 50 plants per m2, the line Williams x Chippewa produced highest grain yield (2866 kg/ha). The highest grain yield (3667 kg/ha) was obtaind in the second sowing date of the second year for the line originated from the Williams x Chippewa. It was concluded that the line from the Williams x Chippewa cross was high yielding than the other line. This line also produced the highest yield in the sowing date of May 15at the density of 50 plants per m2.

Grain yield and most of the traits that have economic importance in plants and animals, are inherited quantitatively and using direct selection methods don’t result in larger gains. One of the effective indirect selections methods for improving grain yield and its components is the selection index. In this study, 109 F2 plants that was produced from a cross between Hashemy and Kadous rice varieties were evaluated to determine suitable selection indices. Studied traits were number of days to maturity, plant height, panicle length, flag leaf length, flag leaf width, panicle per plant, grains per panicle, spikelet’s per panicle, 100-grainweight, grain yield per plant, biomass, harvest index, grain length and grain width. Results revealed that biomass and flag leaf width had highest and lowest, broad sense heritability, respectively. Grain yield had significant positive genetic correlations with grains per panicle, biomass, harvest index, spikelet per panicle, "Nnicle per plant, flag leaf length, panicle length and grain width. Result of path analysis revealed that biomass, harvest index, spikelet per panicle and flag leaf width had positive direct effects on the grain yield while number of days to maturity showed negative direct effect on grain yield. Ten different selection indices based on optimum and base indices were investigated for improving grain yield and yield components. The direct genetic effects (genetic path coefficients) of biomass and harvest index were high. Therefore, an index based on these characters using their genetic path coefficients as economic values, will be useful to select for grain yield. Also for the traits that have higher heritability than grain yield, the use their genetic correlation coefficients with the grain yield as economic values would be a better index for the population improvement. Furthermore, the genetic gain from optimum and base indices were almost similar. However, the base index is recommended due to the easinessof computations and interpretation of results.

Common bean is a dicotyledonous and diploid (2n=22) plant. The archaeologies history showed that its origin is Latin& South America. In order to study genetic diversity in four color beans (White, Red, Chiti & Black) by morphological traits a balanced group block design with three replications was conducted in 2004 at the research station of Tehran University, Karaj. Stepwise regression and path analysis of five traits, related to pod characteristics, showed that, pod weight and days to 50% poding were the most effective traits on grain yield (R2=0.896 and 0.022, with direct effect of 1.917, and -1.621 and correlation coefficient of 0.909 and 0.667, respectively). Factor analysis showed six latent factors that affected about 80% variation of the yield. Cluster analysis by the Ward method divided the genotypes into three separate groups. Red and white colors were in one group, because they had the closest relationship. This group was more related to the chiti but less related to the black color cultivars.

Two separate experiments were carried out to examine the effect of increasing availability of protein sources to honey bee workers on their hygienic behaviors. The 1st experiment was conducted on 10 honey bee colonies in 2 groups using test. First group colonies were fed with pollen substitute cake for three times but the other group was kept as control. The second investigation was conducted as completely randomized design with four different storage pollen levels (3000, 1500, 750 and 750 cm2 with pollen trap) and four replications. In both experiments, grooming behavior was measured by gathering and counting the number of fallen mites on the bottom of the hives and brood removal rate by freeze-killing broods and counting the number of broods that removed by workers at different periods. Data analysis of the 1st experiment showed that feeding or not with pollen substitute cake had not significant effect on appearance rate of both measured honey bee hygienic behaviors (grooming and removing). In the second experiment also the rate of grooming behavior was not affected by levels of storage pollen. But from the view point of removing killed broods there was a significant difference between treatments in the 1st counting period (p<0.01). Mean comparison of treatments at this period showed that mean removal rate of colonies containing the highest (3000 cm2) pollen storage was 36.13% in contrast to the lowest (750 with trap) rate (27.30 %).

Performance of 12 new hybrids of silkworm including Xinhangl xKomingl, Xinhangl xKoming2, XinhanglxV, Xinhang2xKomingl, Xinhang2xKoming2, Xinhang2xy, Xinhang3xKomingl, Xinhang3x Koming2, Xinhang3xy, IOl433xKomingl, IOl433xKoming2, 101433xY, and also three commercial hybrids including 31 x32, 103xI04, 107x 110 were investigated at three rearing periods of two spring and autumn -seasons. Total hatch and rearing steps of hybrids were conducted in the same standard conditions. Also, other activities and traits were recorded under standard conditions. 31x31 commercial hybrid had the highest performance. Season effect on all economical characters, except cocoon shell percentage, was significant (P<0.0001). Also, effect of hybrid type on all characters was significant. Sex had significant effect on cocoon weight, cocoon shell weight and cocoon shell percentage (P<0.0001). Season by hybrid interaction was significant on all characters, except for cocoon shell percentage. In. total rearing period, cocoon weigh of 10000 larvae for 31x32 (20133.6 g) was the highest and for Xihang2 x Koming2 (16421.3 g) was the lowest. In conclusion, the hybrid 31x32 had the best economical performance which can be recommended to rear by farmers under northern conditions of Iran.

To study the effects of plucking time and fermentation of green leaf on quality parameters of black tea an experiment was conducted at Tea Research Foundation of Lahijan in 2004 using two different varieties. Two varieties (Var. No. 100 and Chinese Natural Hybrid) with different time of plucking and five different time of fermentation, i.e. 30, 60, 90, 120 and 150 minutes, were considered in the experiment. Percentage of the aflavins, the arubigins, total color, brightness, and tannins was measured as quality parameters. The results showed that in spite of difference between varieties, changing climates at different plucking time and fermentation time, also affected the amounts of the flavones, the arubigins, total color, brightness, tannins and caffeine. Interaction of var x plucking time x fermentation time was significant with respect to black tea. Therefore, each variety in specific time of plucking and fermentation, will provide a best quality of black tea.

Host preference of rice weevil, (Silophilus oryzae L.), was studied on five native and commercial Iranian rice cultivars as Gerdeh, Beenam, Taarom, Neda and Fajr, at two constant temperatures of 25 and 30±1°C, 75±5%RH, and absolute darkness .Adult attraction to kernels, female fecundity in a 10 day interval of reproductive period, and developmental time were compared among cultivars and temperatures. Adult attraction to kernels was studied by exposing 50 newly emerged adults to rice seeds for one week. The data indicated that Gerdeh and Beenam were the most attractive cultivars as on the average, 12.07 and 11.72 insects from overall 50 insects/dish/day (class A) were counted on them, respectively. On the other hand, Fajr attracted only 6.56 insects/dish/day (class C). The most fecund females were reared on Gerdeh (class A), Taarom (class B), Neda (class BC), Fajr and Beenam (both class C) with an average fecundity of 18.73, 13.1, 9.9, 6.47 and 6.23 off spring/female, respectively. Both parental age and temperature influenced the number of male off springs significantly, while females were affected only by the former. In all cultivars the sex ratio (% females) at 25°C was higher compared with 30°C. Developmental time was significantly (a=0.01) shorter at 30°C than 25°C. It ranged from 35.53 - 40.22 days at 30°C compared with 40.39 - 43.3 days at 25°C in different cultivars. It seems that Fajr and Neda show a relative resistance to rice weevil whereas Gerdeh and Taarom are relatively susceptible cultivars. Beenam showed different effects on the pest in the two temperatures.

Annual medics seed have woody spiral pods that need to be threshed before planting. This can be done during harvesting. In order to design the harvester system, pod cutting force has to be determined. The required force for cutting the pods of two species of annual medics (M scutellata, M rigidula) was determined by conducting an experimental design. In dependent variables were pods moisture, cutting speed and cutting direction of pod. In order to support the samples in tension-compression testing machine head, a special clamp was designed and developed. Results of statistical analysis of the data indicated that in most of the conditions, cutting force for M scutellata increases with increasing moisture content. Cutting force had a significant relation with the direction of application and was lower when applied perpendicular to the pod axis as compared with the parallel condition. Increasing the cutting speed from 0.16 mm/s to higher speeds (10 or 100 mm/s) decreased the cutting force for the M scutellata species. Cutting energy determined based on the area under the force- deformation curve, was used in calculation of power requirement for the threshing system of the annual medics seed combine harvester.

In this study, physical attributes of five common potato varieties, Marfona, Agria, Kosima, Granola and Maradona grown in Charmahal and Bakhtiary province, were determined. The physical attributes were mass, volume, physical dimensions, geometric mean diameter, specific weight, sphericity and surface area. Results showed that Marfona has higher weight, geometric mean diameter, volume and surface area, so it is good for export. Standard deviation of specific weight of Marfona was small, indicating that it is more uniform. The aforementioned variables were obtained from individual varieties of potato as well as a mixture of these varieties. The geometric shape of the varieties was ellipsoidal. Correlation coefficient and coefficient of determination of mass with diameters, volume and mass with geometric mean, mass with volume and also mass and volume with surface area was high (more than 0.9). So the relationships among these physical attributes were determined with the regression analysis. To determine mechanical properties of Marfona, Agria and Kosima tubers, triaxial and uniaxial test was selected to derive deformation energy and tangent initial modulus of elasticity. Two way t-test showed that only tangent initial modulus of elasticity of Agria was significantly different than Kosima in the same strain (20% of initial) at various lateral stresses.Therefore, we can conclude that Agria tubers are stiffer than Kosima.

Improvement and optimization of the processing machines, including blade-type whitener, is one of the factors that could decrease the losses in rough rice milling process. In this study, a rotor equipped with screw conveyor was used. The effect of rotor speed (in four levels: 600, 700, 800 and 900 rpm) and output rate (in three levels: 400, 500 and 600 kg/h) on losses of the Sazandegi rice variety were examined by using a factorial experiment based on randomized complete block design (RCBD) with three replications. In each test, the breakage percentage and degree of milling were measured. The results showed that the main and interaction effects of rotor speed and output rate on the breakage percentage were significant at the 1% level and the main effect of output rate and interaction of rotor speed and output rate on degree of milling were significant at the I% level. Based on results, the highest of breakage percentage (38.25%) occurred at the rotor speed of 800 rpm with an output rate of 600 kg/h and the lowest of breakage percentage (20.79%) occurred at rotor speed of 700 rpm with an output rate of 400 kg/h (on the average of four rotor speeds). In addition, the highest degree of milling (6.45%) occurred at the rotor speed of 900 rpm with an output rate of 400 kg/h and the lowest degree of milling (2.15%) took place at rotor speed of 600 rpm with an output rate of 600 kg/h. However, in practice the rotor speed of700 rpm with 400 kg/h output rate was recommended to be an optimum setting.