AGRICULTURAL RESEARCH
Year:2008 | Volume:8 | Issue:3|Papers Count:13

The effects of silkworm larval feeding by leaves of two different mulberry varieties on some biological parameters and economical characters of silkworm were studied. Silkworm larvae hybrid 31×32 fed on Kokosa variety during first until 3th instars and Kokosa and Isfahan local varieties during 4 and 5 instars. The data of studied characters such as average weight of 5th instar larva (in 1, 3, 5 and 7 days), silk gland average weight of 5th instar larva (in during 2, 4 and 6 days), effective rearing rate percentage, male cocoon weight, male shell cocoon weight, male shell cocoon percentage, male pupae weight, female cocoon weight, female shell cocoon weight, female shell cocoon percentage, female pupa weight and no. egg laid by each moth were measured and analyzed. The results showed that silkworm larvae feeding on different mulberry varieties had not significant effect on cocoon and pupa parameters in two male and female groups (P>0.05). Average weight of 5th instar larva and no. egg laid by each moth in treatment that larvae fed by Kokosa mulberry was higher in comparison to Isfahan local mulberry (P<0.05). Effective rearing rate percentage in treatment fed by Isfahan local mulberry was higher in comparison to Kokosa mulberry (P<0.05).

To investigate the effects of different irrigation water use and methods (tape and furrow) on different parameters such as: water use efficiency, yield components and also different quality parameters of sugarbeet, an experiment was performed in the water resource engineering field in college of agriculture, Razi university in Kermanshah, west of Iran in year 2005 . The experiment was split plot in randomized complete blocks design with 3 levels of irrigation water requirement as main factor (50,75 and 100%) of cumulative evaporation from class A pan with tape irrigation method and 100% of the same condition but with surface(furrow) irrigation method each with 3 replicates. The sugerbeet variety of Rasool was used as crop material. The results showed that the effect of different levels of irrigation treatments on root and sugar yield were significant. The highest root and sugare yield with 120.73 and 20.65 ton/ha were achieved for treatment surface irrigation (100%). For treatment of 100% irrigation with tape method 119.18 and 18.44 ton/ha root and sugar yield were achieved respectively. The results showed a reduction of (24.05 and 37.28%) for root yield and (15.13 and 26.84%) on sugar yield for defecit irrigation 50 and 75% treatments, although, water use efficiencies for sugar production, 6.67 and 26.32% increased respectively. In furrow surface irrigation treatment (100%), the amount of water use was 1.55 times more than treatment tape surface irrigation (100%), while water use efficiency based on root and sugar yield, 34.61 and 40% decreased respectively. The results showed that the surface irrigation tape treatment (75%) in which irrigation water was applied at the rate of 75% can be used for sugarbeet grown in regions where irrigation water supplies are limited. Although in the proposed treatment the root production compare to full irrigation treatment was lower significantly, but from point view of sugar production were in the same level.

Drought is one of the most important natural hazards which usually happens in different regions of Iran. This study was conducted in order to determine meteorological droughts in Karkhe watershed according to precipitation data for 12 meteorological stations using SPI and Deciles indices. The data homogeneity was examined by run test performance. Then all the required data were prepared for 9, 12 and 24-month SPI's and annual deciles were computed. Drought intensity and percent of drought frequency were regionalized using Kriging method for both SPI and decide of 10 percent. The results showed that at first droughts happen in short time scales of SPI and if drought conditions continue, they will happen in longer time scales. Meteorological drought intensity and percent of drought frequency decrease from west to east of Karkhe watershed. Also, if the drought frequency percent (the ratio of drought periods to total record periods) increases, the drought intensity will increase.

Rodents are one of the most important pest of agricultural crops in the world. Rats cause loss directly yeild in sugarcane fields with cutting stalk of cane. In this study, fluctuations of population and chemical control of Nesokia indica Gray in sugarcane fields were investigated in Salman Farsi and Hakim Farabi agro-industries in Khuzestan/Iran. After harvesting of crop (early December) active nests were counted in three hectares and sampling was continued until ratooning operations weekly. Sampling in April until Julay was conducted with counting of damaged and dried tillers or observing of nest. Final sampling was at harvesting time based on pecentage of damaged stalks. Evaluation of chemical control was conducted as completely randomized design including: plots with and without bait with three replications. Baits of Kelerat (Brodifacom 0.005%) and Zinc phosphide 5% with grains of wheat were used in agro-industries Salman-Farsi and Hakim Farabi respectively. Baits were used two or three times after harvesting with interval one week. Number of active nests were counted and then percentage of nest reduction was calculated. All captured rats from sugarcane fields were Nesokia indica Gray. Investigation of fluctuations of pest population showed that peak of pest population was after harvesting time that it was over 100 active nests per hectare. The population reduced gratualy (rats leave the fields) after that with ratooning operations and then irrigation of fields. Rats return into sugarcane fields with stopping of irrigation at late of plant growth stage, and start their activity. Damaged stalks was over 20%. Kelerat bait (three times) reduced pest population over 90%, but using of zinc phosphide (two times) was not reduced significantly it. It is better that chemical control of pest counduct after harvesting of crop and before ratooning operations. also, It is recommend.

For drip irrigation systems, to obtain improved water use efficiency, distance between emitters and emitter flow rates must be matched to the soil wetting characteristics, and timing of water to be supplied to the crop. The information on depths and widths of wetted zone of soil plays the great significance in design and management of these systems. The depth and the width of  wetted zone is related to soil properties, water application rate, total amount of water in the soil and initial moisture content. In this investigation, an empirical model was developed to simulate dimensions of soil wetted zone under drip source. For this purpose, the field experimental data which was measured in Pardis agricultural farm of Karaj, was used to evaluate semi-empirical model of Zur-Schwartzman and empirical model of Amin-Ekhmaj. The coefficient of these equations determined with both nonlinear regression approach and optimization with least square approach. Predicts of equations obtained from nonlinear regression and optimization approach, predicts of Zur model and predicts of Amin model compared with the observed data. The evaluation of models based on comparison of statistical parameters of simulated data with that observed data. The parameters used were Mean Error (ME), Root Mean Square Error (RMSE) and model efficiency (EF). Very good agreement between theoretical and experimental results improves the validity of these equations. To evaluate above mentioned models also two available published experimental data by Risse et al. (1989) and Li et al. (2004) was used. The results show that suggested equations can be used for wider range of discharge rate and other soil types.

The experiments were conducted to determine amino acids digestibility of soybean meal, using two bioassays as collecting ileum content and collecting fecal in male broiler chickens. The experiments were conducted (with 100 birds) at 21 and 42 days of age, using metabolical cages, as a CRD with 4 replications (2 birds per each replicated). Amino acid digestibility was determined using titanium oxide as a marker. The birds were killed on day 42 and the contents of the ileum were collected to determine amino acid digestibility. The results of experiments indicated that industrial procedure had effects on the soybean meal digestibility. Mean values of apparent and true digestibility of soybean meal for fecal assay were 78.57 and 79.57 percent and for ileum bioassay 71.39 and 72.28 percent respectively. The results have shown that amino acid digestibility of soybean meal was approximately 10.08 percent higher for excreta collection bioassay compared to ileum assay. The result of data confirms that systeine, aspartic acid and glutamic acid digestibility were higher than other amino acids such as isoleucine and valine of soybean meals for two ages (21 and 42 days) or both bioassays respectively.

Salinity analysis in tidal rivers is generally more complex than normal rivers. The reason of this complexity is tides that occur in sea which in this term affect rivers connected to sea or ocean. Salinity front moves toward the river at high tide duration and vise versa at low tide duration. This is the main reason of mixing of saline and fresh water along the river.In this paper the differential equation of salinity mass transfer and saint-venant equations are solved for tidal conditions using the finite difference control volume method. To demonstrate the ability of the developed model a real case conditions Karun-Bahmanshir and Hafar branches was modeled and salinity of this branches was predicted. Results indicate that salinity in Bahmanshir can be reduced by increasing discharge of fresh water in the artificial channel connecting Karun and Bahmanshir.

Transportation of chemicals from soil surface toward aquifers is influenced by soil properties, tillage management, leaching and the rate of transportation processes. Models substantially are useful for studying and applying management and it is possible to use them in planning special experiments on water and solute transport. The study was performed in two consecutive years. Different tillage treatments including disk harrowing + two disk harrowing as reduced tillage (15 cm plowing depth) (T1) and moldboard plowing + two disk harrowing as conventional tillage system (30 cm plowing depth) (T2) were used. The above mentioned treatments were done in a randomized complete block design with 3 replications and under corn cultivation for two years. To study bromide transport through the soil, potassium bromide with concentration of 16.67 g/l was sprayed uniformly on the soil surface. Then, bromide transport was predicted by solute transport models. The results showed that with increase of leaching, bromide mass center was moved to deeper layers and this kind of movement can be observed in T2 with more intensity. Comparison between the distributions of bromide concentration by deterministic convection-dispersion equation (DCDE) with measured data revealed that DCDE is more careful in prediction than stochastic CDE (SCDE). In T1, with increase of bromide leaching, CDE models fitted measured data poorly as well. On the opposite side, in T2, CDE models could present appropriate fitting of measured data (after 10 irrigations or 630 mm water). After second and fifth irrigation (126 and 315 mm water), the fitting of CDE models on bromide leaching in the soil under T1 was better than T2. Two-region mobile and immobile model (MIM) and stochastic regional model (SRM) did not present ideal fitting on the bromide transport in soil.

Some economists believe that low price of agricultural inputs and governments supportive  payments to agriculture sector as important factors cause low efficiency of agricultural inputs in the most of developing countries. Although governments supportive payments to agricultural activities is fulfilled for the purpose of increasing of social benefits, but it will cause some economic and environmental externalities. The objective of the study is to analyse the impacts of energy subsidies adjustment as policy scenarios on aquifer conservation of Hamedan-Bahar plain in Hamedan province, by considering the dynamic relations between aquifer groundwater balance and the agriculture sector. For this purpose the combined use of simulation and optimization (S/O) techniques is considered in a dynamic framework. Analysing of the results indicate that adjustment and reduction of energy subsidies in agricultural sector of Hamedan-Bahar plain, will reduce total exploitation of aquifer groundwater and increase the economic life of Hamedan- Bahar plain aquifer.

Phytoseiid mites are the most important and studied natural enemies of pest mites. Phytoseiulus plumifer (Acari:Phytoseiidae) is one of the most important natural enemies of spider mites in Iran. This investigation was carried out to examine the effects of the prey species and their different densities on functional response of P. plumifer. Adults of the predatory mite after collection from botanic garden (Karaj) reared on Ficus leaves. The 24-h leaf disc experiments conducted at laboratory condition (27±1oC, 50±10% RH, 16:8 L:D photoperiod) on apple leaves as host plant. The larvae of  Tetranychus urticae and Amphitetranychus viennensis (Acari: Tetranychidae) were offered as prey at the following densities 2, 4, 6, 8, 16, 25 , 35 and 2, 4, 6, 8, 16, 25 , 35, 45 and 50 for T. urticae and A. viennensis respectively. The results indicated that the predatory mite exhibited type III and II functional response against the T. urticae and A. viennensis (Acari: Tetranychidae) respectively. After determining the type of functional response parameters must be estimated. The attack coefficient (a) and the handling time (Th) for A. viennensis were 0.0638 ± 0.0164 and 0.9841±0.1494 h, respectively. For T. urticae, b was 0.0021±0.0003 and 0.9696±0.1185h, respectively. Maximum predation on T. urticae and A. viennensis were estimated 24.75 and 24.39 larvae per day.