Journal of Agricultural Sciences and Natural Resources
Year:2002 | Volume:8 | Issue:4|Papers Count:18

Daily estimates reference evapotranspiration were computed by FAO-Penman-Monteith (FP-M), Penman- Wright (P- W), and Hargreaves-Samani (H-S) methods from the climatological data recorded at Mehrabad Synoptic Weather Station between 1966 to 1998. The daily average ET0 of each month of the year was calculated as the average of the daily ET0 computations of that month. Due to the lake of lysimetric data, the estimates of FP-M were considered as actual values and the performance of the other two equations were compared with ET0 estimates of FP-M method. The daily ET0 and the monthly average ET0 by P-W method were overestimated 13% and 11% respectively. With the same order standard error of estimates were obtained 0.52 and 0.46 mm/day.Similar values for H-S method were underestimated 14% and 12% and SEE values were found 1.11and 0.75 mm/day. In order to increase the accuracy of ET0 estimates, they were compared with ,FP-M estimates using a linear regression equation of the form ET0(actual)=a+b ET0(estimated)and the values of the regression parameter (a and b) was found using the data of 1966-1978. Then, ET0 of the period 1982 to 1998 were adjusted according to the regresion equation with the values of a and b parameters as found. The resulting ET0 estimates were close to the FP-M estimates and the SEE of monthly ET0 estimates of P-W ans H-S methods reduced to 0.18 and 0.37 mm/day.It is concluded that in areas of similar climatic conditions with lake of extensive measured cIimatological parameters. H-S equation can be used for estimating monthly ET0 from long-period historical temperature data.

In this study the erosion and sediment rates of Aglagan-chia basin was estimated on the basis os FAO and MPSIAC methods. In FAO method the yearly erosion rate is 3.87 tons and the sediment yield rate is 167 ton in hector. Six environmental factors were studied; namely, surface geology, soil, topography, landcover and landuse. In MPSIAC method, however, the yearly erosion rate is 3.1 ton and sediment yield rate is 133 ton in hectar. Nine enviromental factors were studied in this method, including, geology, soil, climate, runoff, topography, landcover, landuse, surface erosion and river erosion. The estimated rates of sediment by FAO and MPSIAC were contrasted with those of Hydrometry station. The'results achieved indicate that using MPS lAC method is acceptable in estimating erosion and sediment.

This survey was carried out in order to evaluate the classic sprinkler irrigation systems that were executed in three different locations of GORGAN. Evaluation was done over two different fields with 3 irrigations and in one field with 2 irrigation over growing cycle of the plants. The results also revealed that there are a grat difference between application of sprinkler irrigation methoods and what they were to be in another words it is not justifiable due to factors such as: lack of constant control and management, after application; lack of compatible of design with operation; lack of user's knowledge and information of the systems; amount of applied water does not match requirement of the plants; greater influence of business and marketing with respect to high quality design. The mean values of DU,Cu and AELQ for field 1 equal to 59.6, 69.7 and 50.5 percent, and field 2 equal to 70.3, 82 and 50.2 percent, and field 3 equal to 69.8, 67.9 and 45.6 percent, respectively.

To study the effect of aerodynamic property on three agricultural products namely Barley, corn and Lentile, an experiment was conducted in Tehran Tarbiat Modarress University, Faculty of Agriculture during 1378/1999. This property is used for separating the unwanted materials during the harvesting period in the form of dynamics and also transfer materials in the form of pneumatic, therefore cleaning and sorting. In this study interaction between solid particles and moving fluids(air) also estimation of the forces to be used on particles, terminal velocity and necessary calculations for the above products were evaluted and results showed that corn terminal velocity is more than two other products. so it needs more drag force during transmission. The particles closer to sphere, have more accuracy in calculations and are comparable with numbers in tables and curves. The particle that is heavier (corn) has more terminal velocity than lighter particles (Barley and Ventile).

Annual medics is a plant that is used for feeding domestic animals and as the green compost has an important role in strengthening lands and producing cattle feed.Medics' roots can stabilize nitrogen. This plant can planted alone or along with grains. If it is planted along with, it can be helpful in weed control. Because the production of annual medics'seed is difficult, design and construction of suitable,harvesting and threshing machines for seed production has top priority in research activity. In this study, physical properties of seven species of annual medics were determined. A series of tests were then conducted to determine the best threshing conditions. In these tests, effect of threshing clearance on germination, cleaning and separation efficiencies of seed were studied using a laboratory mill with plates of variable clearance. For this purpose, an experiment was conducted for two spicies of annual medics namely M.Scutellata and M.rigidula pods at three levels of threshing clearance and two levels of moisture content. The experiment followed a factorial design based on a completely randomizcd framework. It was found that the threshing clearance and seed moisture content affect the cleaning efficiency and seed separation. Surface in addition has a positive effect on germination percentage beacuse of stimulation of pods during thresing. Regarding cleaning efficiency, there is an interaction between threshing clearance and seed moisture content for M.rigidula. About the seeds' separation percentage from thresher, there was an interaction between threshing clearance and seed moisture content for M.Scutellata.Regarding germination, there was an interaction between threshing clearance and seed moisture content for M.Scutellata.The best threshing clearance is in the 3-3.5 mm range of M.Scutellata and 1.8-2 mm range for M.rigidula.This clearance is the same as seed width that was measured in the study of seed physical properties. The results of this research have an important role in design and construction of harvesting machinery and also on threshing of annual medics that is being conducted.

A field experiment was conducted at the Agricultural Research Station, Sari,Mazandaran Uni. to evaluate the effect of tillage, row spacing and weeding on soyben production and weed management. The experiment was a split plot in a randomized compelet block design with four replications. The main plots were tillage at three levels; Conventional tillage (CT) Reduced tillage (RT) and NO-tillage (NT). The sub plbts were factorial of row spacing at three levels: 60-, 50-,and 40 cm at two levels of weeding; weed-free check and weedy check. Three tillage systems in weed free check had no significant difference in height of soybean but in weedy check the maximum height was obtained in conventional tillage. In disk and no-tillage systems, dry weight of soybean (12 weeks afrer emergence) compared with conventional tillage was decreased 15.5% and 8.5%, respectively. Weed-free check produced 55,47, and 46 pod/plant in CT, RT and NT, respectively while weedy check plot produce 25,29, and 35 plot/plant. Tillage plot yielded 36,39, and 46 pod/pInt in 40-50, and 60-, cm of row spacing while reduced and no - tillage system yielded 34 and 37, 39 and 40, and 41 and 43 pods/plant in 40-, 50-, and 60-, cm of row spacing, respectively.Soyben yield production was 3559 , 2647, and 2532 kg/ ha for CT, RT, and NT in weed-free check and 1223, 1339, and 2198 kg/ha in Weedy check, respectively. In terms of weed infestation, no-tillage system had 77% less weed and produced 61% less weeds dry weight compard to CT. NO - tillage system could be recommended as a weed management practice to reduce weed pressure.

In order to understand more clearly differences between different varieties of tobacco in quality characteristics of leaf chemical characteristics, six fire-cured varieties of tobacco were examined, DRV1, DRV10, Madole, Kentucky 171,Toleza68 and Western for absorption and accumulation determination potash and nitrogen in different plant parts and quality characteristics. Plants were grown in a unheated greenhouse in March of 1999, and then seedling transplanted into the field in spring year 1999, and in a randomized block design was planted with four blocks. Results showed that there were significant differences between different cultivars in percentage of root potash, root nitrogen, leaf nitrogen, stem potash and percentage of sugar. But percentage of leaf potash, stem nitrogen, nicotine, total ash and burning time were not different between different varieties. Amount of potash and nitrogen in different plant parts varieties were different at different stages of growth. The maximum and minimum absorotion of potash and nitrogen were observed at early and late stages of growth (42-58 and 94-122 days after  planting),respectively.

Effect of water regims after anthesis (30, 60 and 80% depletion of available soil water) on days to maturity, plant dry weight, grains weight, water relation, water use efficiency (WUE) and re-translocation of three wheat cultivars (Taijan, Zagros and Khazar 1) were investigaled using a factoral arrangement of a randomized complete blocks with 3 replicates in a greenhouse. Results showed that with decreasing moisture regims after anthesis, days to physiological maturity is decreased, but the regims had no effect on total biomass or grain weight. Water limitation accelerated leaf senescence, decreased leaf area per plant and evapotranspiration, increased WUE and re-translocation to the grains. The highest re-translocation was observed in 80% depletion treatment. Among cultivars evaluated, Tajan had the greatest evapotranspirtion before and after anthesis and days to maturity.

The plot is a fundamental experimental unit in field experiments, and it uses as the vehicle for evaluating the response of the experimental materials to treatment.Therfore, selecting of plot size is important. In order to select of optimum plot size,present research was conducted in the research farm of Aghgala in Golestan province in cropping year of 1999-2000. Sixteen genotypes of barley (Hordeum vulgare L.) were evaluated in 3 different plot size (2,4 and 6 square meter) by using of randomized complete blocks design (RCBD) with 3 replications. The experiment was conducted in saline soil conditions (with electerical conductivity= 10-12 ds/m).During the growing season, common agronomic practices were done. After harvesting analysis of variance was conducted for each plot size, separately. The results showed, significant difference (P < 0.05) between genotypes in plot size of with 2.4 and 6 square meter. The means were compared with Duncan,s Multiple Test. The same results were obtained with the 3 different plot sizes. Therefore, it can be concluded that using smaller plots do not influence final experimental results.

In this research the total of resistant bacteria to heavy metals communities were studied in agricultural soils.The effect of four heavy metals of Lead (2mM), Copper (5mM), Cadmium (0.5 mM) and Arsenic (5mM) on microbial population of ten agricultural soils with irrigation from Zayandehrood river were studied and then the Minimum Inhibitory Concentration (MIC) for 38 bacteria isolates were determined.The dry cellular weight, the amount of metals sorption inside the bacteria and the multi-resistance to few metals for the isolate resistant the bacteria were determined. A great proportion of the isolates were resistant %45, %8 %50 and %40 to lead,copper, cadmium and arsenic respectively. Also the MIC arsenic was the highest amount but the lowest percent absorption was determined for arsenic. The majority of the tested strains (%92.1) were multiple metal resistant, with tri-metal resistance at the major pattern (%36.8). The highest patterns resistance existed between lead,copper and arsenic (%15.7).

In recent years heavy metals have received widespread attention because of their release into the environment, and toxicity to a wide variety of organisms. Cadmium has not known biological function and is extremely toxic even at low concentrations.Cadmium can enter the environment from various sources, such as mineral and industrial wastewater and coal combustion, and can transfer from microorganisms through food chains to higher organisms. Some microorganisms have biotechnological applications for metal removal and/or recovery. Yeasts may be better suited for this purpose than other microbial groups because of their often great tolerance toward metals and other adverse external conditions such as low pH,and their high wall binding capacity and often high intracellular uptake values. In the present study, several yeast strains from industrial wastewaters were isolated and their tolerance to cadmium was determined. For isolation of yeasts, samples of industrial wastewaters were taken to the laboratory, and using yeast extract chloramphenicol agar (YECA), 18 yeast strains were isolated and then pure cultured on potato dextrose agar (PDA). A strain of laboratory Saccharmoyces cerevisiae was used as control. The effect of different concentrations of cadmium on growth rate of control strain was examined and the concentration of cadmium which reduced its growth rate to 50% (EC50) was calculated. The tolerance of all yeast strains to cadmium was determined using growth of each strain in medium containing 15 µgmL-1 cadmium. According to these results, the most tolerant strain, isolated from industrial waste water showed 34.9% viability, while the viability of S. cerevisia (countrol) was 3.3% .

Cutworms (Agroti sspp.) are the most important pests of field crops.In shahrood region following species were identified: A.segetum (Denis & Schif), A.ipsilon (Hufnagel), A.exclamationis (L.), A.spinifera (Hubner) and A.sp.near herzogi.Collection of adult insect and samples collected from pheremon traps indicated that A.segtum was the dominat species. This pest has three generation in a year and highest damage is caused by its first generation in May. Overwintering takes place in depth of 10-15 cm. of soil by 3rd and 4th larval stages. Moths activity was observed during March to November. Natural enemies were collected from larvae and were identified as:two species of parasitoid,Meteorus sp.(Hym.,Braconidae ),one species of Chalcididae and a parasitic mite,Pygmophorus sp.(Acari,Pygmophoridae). Chemical control was conducted in a randomized complete block desing with six treatments:Carbaryl 85% wetable powder,Padan 4% granul,Diple 2x (bait),Chloropyriphos 48% (spray and bait) and treatment of without insecticide in four replication at the College of Agriculture reaserch farm in Shahrood. In this study Chloropyriphus 48% (bait) was found to the most effective against this pest followed by Carbaril 85%(bait),Padan 4% (Granul),Dipel 2x (bait)and Chloropyriphus 48% (spray). The efficacy percantage using Henderson- Tilton formula following larval mortallities, Chloropyriphus (bait) 66.27% Carbaryl 64.45%,Padan 61.75,Dipel 2x 61.54% and Chloropyriphus (spray)42.27%.

In order to study seasonal fligh activity of cydia pomonella and to determine spraying time, an experiment was conducted for two years at two different orchards in Shirvan region in 1998-1999. The seasonal flight of activity cydia pomonella was investigated by using pheromone traps and collecting samples from eggs, larva and pupa stages of the pest. The results showed that Laspeyresia pomonella has three generations in the region. The adult insects after production by the second and third generation is low. The apples fruit can be mainly damaged by the first generation of cydia pomonella that will happen about ten days after the adult emergency. With regarding to the results, spraying should be done during three weeks from 9th cydia pomonella for the next year.

Mistletoe is known as a semi-parasite on fruit and forest tress in all of the world. This plant absorbs water and mineral nutrient of host and kill it gradually. In this study, many samples were collected from the fruit orchands and then distribution,precentage of damage and spesies of mistletoe were studied. The results showed. That infaction in the intermoutains areas, intercropping and lowerdensity orchard was more than others. The most contamination was on almond (Prunus amygdalus),apricot (Prunus armenica), pear (Pyrus communis) and very little in plum (Prunus domestica).This serui-parasiteplant causes dieback, loss in yeild and reduction in growth. The most loss of yeilds was in dryland farming almond (%59) and at least in plum (9%). The species of mistletoe in all of the hosts were Loranthus grewingkii Spach. The leaves of the species are thick, firm and in opposite pairs. The calor of the flowers is yellowish white and the kind of the fruit is berry. This species is reported for the first time from Iran.

A survey has been done on Cystoopsis acipenseris of sturgeon during 1997-1999. 218 adult and 236 Juvenile samples were caught and examined. Parasites contained in males and females were in cysts from and lie between the scales in skin of sturgeons. Frequency of this parasite in juvenile Acipenser persicus and Acipenser guldenstaedti were 5.83% and 6.42% respectively. Cysts diameter in A.persicus were in the order of 3.45 ±0. 75 mm to 3±91.42 mm and in A. guldenstaedti were 2.28±0.48 mm to 2.75±0.61 mm as well. A sample of adult sturgeon A.stellatus with 129 cm total length had 6 cystoopsis acipenseris cysts and the cysts diameter were in the order of 1.6 cm to 2.4 cm. Lymphocytic infilteration between epithelial cells around the nematod, showed the major pathological responses which indicates choronic inflamation. Epithelical cells showed necrotic changes with karyotic pyknosis too.Frequency of this parasite in juvenile sturgeon and occurance in adult sturgeon is being reported for the first time in Iran.

Two hundered fourty specimens of juvenile sturgeons were caught by beach seine during 1997-1999. The samples were preserved in 10% formalin. Measurement of morphometric charactristics were made using fishery measuring board with an accuracy of 1 mm and sliding calipers with an accuracy of 0.1 mm on samples following standard methods for sturgeons. In this study eighteen morphometric and ten meristic characters were used. Substantial variation was found in Acipenser guldenstaedti and A.persicus populations with respect to the average values in the individual size classes for morphometric characters by using the T-test and was showed the relative values of a number of characters vary with the growth of the fish. In principal components method, samples of Acipenser guldenstaedt and A.persicus is completely isolated and confirmed significant phenetic diversity of sturgeons of two groups and determined importance characters for distinguished of two groups. Mean values of meristic characters of sturgeons in relation to the average values in the wide size series of specimens and diversity index methods differ in most cases significantly in samples by using T-test and V-test respectively.In Pc method, determined the distinguishing characters between two group which had more importance.