JOURNAL OF AGRICULTURAL SCIENCE AND SUSTAINABLE PRODUCTION
Year:2003 | Volume:13 | Issue:4|Papers Count:11

To evaluate the effect of heat stress and dual feeding system on the two strain of broiler performance, eight hundred one-day old chicks from two starin (Arian and Ross) were used in a factorial experiment. Treatments were two types of feeding system namely dual feeding program and control (standard) and two ambient temperatures (36°c and 24°c). Chicks were raised in normal condition up to 21 days of ages and then divided into two equal groups and reared either in heat stress or in normal ambient temperature. The main experimental period was four weeks. During the first week of study, in the stress group, the temperature was raised by 2°C daily and remained constant at 36°C. Broilers were exposed to stress from 10 AM until 17 PM every day. Control or stressed group was assigned to either standard diet or dual feeding system. High protein fraction of dual feeding system was offered daily from 19 PM to 10AM and low-protein fraction offered from 10 AM till 17 PM daily. During the first week of the study, due to gradual increase in temperature the effect of heat stress and broiler starin on animal performance were not significant (P>b.05). During second week of the study, weekly feed intake was significantly (P<0.05) higher in Ross than Arian (0.54 vs 0.52 kg, respectively). Dietary regime significantly influenced the weekly feed intake (l.03kg for control and 1.11 kg for dual feeding) during second week of study. There were significant effect of starin and feed regime (P<0.05) on broiler growth (0.54kg for Ross vs 0.52 kg for Arian and 0.52kg for control diet vs 0.54 kg for dual feeding) at the third week of study. Feed conversion ratio was statistically affected by dietary regime (P<0.01) in the first two weeks, but in the third week, only starin significantly affected the feed conversion ratio (l.95 for ross vs 2.07 for Arain). In general using dual feeding program had an advantage of decreasing the adverse effect of heat stress. The growth rate of Ross starin was lower than Arian in this study.    

Canopy structure of some Iranian wheat cultivars, developed for cold and temperate-cold climates within the last 50 years, were studied in two separate trials during 1998 and 1999 in the Research Station of College of Agriculture, Ferdowsi University of Mashhad. In both trials 6 wheat cultivars were investigated in a randomized complete block design with 3 replicates. In the first experiment all cultivars were sown at the same date and with the equal planting density and N fertilization. However, in the second experiment cultivars were sown under the recommended sowing date, plant density and N rate for maximum yield. Other management practices were identical in both years. New wheat cultivars had a greater light extinction coefficient (K) and positioned a higher proportion of their leaf area at the top canopy layers. Such a canopy structure led to better absorption of radiation at top canopy layer in new cultivars. A decreasing profile of specific leaf nitrogen (SLN), specific leaf area (SLA) and leaf nitrogen content (LNC) were observed from top to bottom of the canopy with a negative correlation between SLW and LNC.

To study the soybean (Glycine max L.) and sorghum (Sorghum bicolor L.) interference and influence of plant density and distance of one species on performance of other species, a field experiment at three different designs was conducted at the research station of Faculty of Agriculture, University of Tabriz at 2000.The experimental designs were performed as target experiment based on randomized complete block design with three replications. At the first experiment, the distance between target species( soybean) and competitor species (sorghum) was studied at 5,20,35,50 and 65 centimeters .At the second experiment sorghum was used as a target plant and soybean as competitor. The third design include 2,4,6 and 8 plants of sorghum (competitor) at the fixed distance from target plant (soybean). Soybean grain yield at distances below 50 cm was affected by negative competitive effects of sorghum. The inter-specific competition coefficient (ISCC) of sorghum on soybean linearly decreased as the distance of competitor plants increased and at 65 cm decreased to zero. The soybean had maximum competitive effects on sorghum at 5 cm distance, whereas, ISCC of soybean on sorghum at distances beyond of 20 cm was equal to zero. When the competitor plants (sorghum) density at constant distance from target plant (soybean) increased, the ISCC of sorghum on soybean increased. The number of 1eafandbranch per plant in soybean decreased at distances below 35 cm, significantly.    

Because of the importance of medicinal plants for producing natural based drugs, this study was conducted to evaluate the ecophysiological effects of irrigation and sowing date on Anise, which is used in drug and food industries. Five irrigation treatments: I1 (irrigation was omitted during stem elongation), I2 (irrigation was omitted during stem elongation and grain filling stages), I3 (irrigation was omitted during umbel appearance), I4 (irrigation was omitted during grain filling period), and I5 (irrigation in all growing stages, as a control), were studied on three sowing dates (April 4, 16 and 29). The results showed that leaf area index (LAI), specific leaf area (SLA), plant height and biomass were decreased significantly in the third sowing date. Also these characteristics were decreased significantly by irrigation disruption in I1, and I2 levels. Stomatal frequency was reduced when sowing date was delayed. However, water stress in h and specially in I1 and I2 levels .increased stomatal frequency. The results also showed that the stomatal length was decreased due to water stress in stem elongation and umbel appearance stages, but it was not affected by sowing dates. Grain yield ranged from 893.4 to 457.2 kg. ha-1, for D1I5 and D3I2 treatments, respectively. The mean number of umbels in plant, umbelets in umbel, grains in umbelet and 1000 grain weight were significantly decreased when sowing date was delayed and plants were exposed to water stress. The results indicated that for successful grain production, Anise must have been sown early in spring (April 4) in Tabriz and water stress during grain filling period had no effect on yield of this plant.    

One of the important factors in all stages of mechanization from crop production to processing is Mechanized planting and in case a precision planting machine is used to place the seeds without scattering, at regular intervals along the row and in suitable condition, the excess consumption of inputs namely, seed, water, fertilizer and spray could be avoided. Also, cultivation and harvesting operations can be performed, easily, mechanically in less time and better quality and fewer cost. Regarding the growing trend towards canola production in the country, a precision drilling machine with precision metering and depth adjustment systems was constructed to be able to distribute single seeds evenly, along the row. The workshop tests were conducted upon the metering system of the designed precision drilling machine as well as locally available drilling machines constructed in Iran at four different travel speeds. The results indicated that precision drilling machine operated independent of speed and vibration didn't have any effect on the performance of metering system. Field tests were conducted for two planter (precision drilling machine and conventional drills) and two types of seedbed (mould board plow + disc + land leveler, mould board plow + rotivator ) using factorial experiment on the basis of randomized complete block design. Two types of planters were significantly different in terms of emergence number indices. Field test evaluation indicated that equidistant distribution of seeds was achieved and seed scattering in precision drilling machine was satisfactory.      

Dynamometers are equipment for measuring force. In this study a drawbar dynamometer was designed, constructed and evaluated after calibration in the workshop. This dynamometer can be used for measuring of draught force in most of agricultural implements as well as drawbar pull in category I and II tractors. The mechanical parts of the dynamometer include main bodies, metallic parts of bodies, elastic element, spherical roller bearings and other attachments. Electronical parts include strain gauges, bridge circuit and microvoltmeter. The source of power supply can be provided from tractor battery. Results of tests showed that there was a linear relationships between compressive force exerted on the dynamometer and of the output voltage, and the correlation factor (r) was as higher as 0.99.      

Recently researches showed that precise hill dropping was better than drill planting for several crops such as rice, bean and corn. This study was carried out to design and evaluate a roller type-metering device suitable for hill dropping. Two planting units consisting of seed tank, metering device, brush, drive shaft and bearings were designed and constructed. A completely randomized factorial design with five replications was used. The factors were the roller diameter (60 and 70 mm) and three tractor forward speeds (3, 4 and 5 km/hr). The dependant variables were SDR (Scattering Distance Ratio) index, seed damage rate and the amount of seeds planted per hectare. Analyses of data indicated that SDR index was significantly different between the treatments and that of obtained from the conventional fluted feed metering device. The effects of the two factors also were significant on the SDR index. There was significant difference among the treatments and control on seed damage rate. The effects of levels of the forward speed on seed damage rate were significantly different. The seeding rate was significantly different among the treatments and control. According to the results and the fact that the roller type metering devices are structurally simple and regarding their easier production, they are advisable for precision hill dropping. It is worth noting that this type of planters with suitable brush and lower forward speeds will provide better results.      

In order to study the genotype x environment interaction, replicated yield trials were performed using 19 barley genotypes in a randomized complete block design with four replications, at eight agricultural research stations of temperate regions for three years. Mean grain yield and two environmental variables, mean air temperature and mean soil pH were used for Redundancy Analysts. In this method, two variables RA1 and RA2 were constructed. Each one was the linear combination of environmental variables mentioned above. The genotypes 3 and 15 in relation to RA1 and the genotypes 1, 11, 12, 13, 14 and 19 in relation to RA2 had large percentage sum of squares per genotype (R2) These values for genotypes 3 and 15 were 87 and 81, and for next six cultivates mentioned above were 22, 20, 38, 29, 18 and 36, respectively. Thus in comparison with other genotypes, the interactions among these cultivars and the locations under study were determined mainly by air temperature and soil pH, and these genotypes were more sensitive to the temperature and pH. The R2 for RA1 and RA2 models were small for the genotypes 2, 4, 5, 7 and 16. Therefore, these cultivars were considered to be adapted and insensitive to the environmental factors. The genotypes 5 and 7 had the high grain yield, too. The replacement of residuals obtained from the regressions of local indices and the environmental variables in Redundancy Analysis model, and doing Partial Redundancy Analysis, showed that in addition to the air temperature and soil pH, the other environmental variables were more or less effective in forming the genotype by location interactions. Cultivars 5, 17 and 18 showed smaller interactions as compared to others. To construct the LISREL model, the means of air temperature, soil pH, date of maturity, date of heading and plant height as the environment and phonologic variables, and the mean grain yield and 1000 grain weight as the variables related to the genotype × environment interaction, were entered in the model. Results indicated the further importance of air temperature and grain yield variables. Also combination of LISREL and Redundancy Analysis models indicated that because of large coefficients of grain yield and air temperature in the LISREL model, study of genotype× environment interaction using these variables by Redundancy Analysis model was worthwhile.      

Blackleg disease of rapeseed, which is caused by Leptosphaeria maculans (Phoma lingam), is considered as one of the destructive diseases of crucifera family and has resulted in total yield loss in some locations. It appears as an endemic disease in many areas of the world, especially in rapeseed fields. In this study, the response of six winter cultivars of rapeseed to the two isolates of the fungus (Aliabad and Bandar Torkman) was evaluated. Plants were inoculated in different growth stages: cotyledon, and stages, 2.3-2.4, 2.1, and 3.2, using spore suspension under 23±1°C on the basis of established procedures for a successful infection. Inoculated plants were kept under plastic covers for 48 hours in order to provide a 100% relative humidity. After inoculation period, disease severity was assessed in cotyledon stage by the method of William and Delwich, in stage 3.2 by McNabb and Rimmer, and in stage 5 on the basis of Newman and Bailey, and also Mc Nabb and Rimmer. It was revealed that responses of Okapi and SLM046 to disease were homogenous in all stages. Okapi was recognized more susceptible and SLM046 more resistant than other cultivars under study. Talaych, Regent × Cobra, Fomax and Ceres which showed different reaction during different stages of inoculation, indicated the heterogenicity of response to blackleg disease in these cultivars.          

Genetic control of infection type of stripe rust was studied in a half-diallel design using six wheat varieties, Tiritea (a susceptible control), Tancred, Kotare, Otane, Karama, and Briscard. These varieties and their 15 F1 diallel hybrids were evaluated by three stripe rust pathotypes, 7E18A-, 38E0A+, and 134E134A+. For each pathotype a randomized complete block design was conducted with 21 treatments. Data for infection type were analyzed on the basis of Morley Jones, Waiter and Morton, Griffing, and Hayman's graphical methods. Positive and negative degrees of dominance were observed for every pathotype, indicating the host-pathogen interaction. Analyses of variance showed the importance of both additive and dominance genetic effects in controlling the infection type of stripe rust. However, the role of additive effects was more important than non-additive effects. Average of broad-sense and narrow-sense heritability estimates was 0.92 and 0.89, respectively. In the graphical analysis of Hayman, degree of dominance ranged from partial dominance to overdominance depending on the pathotype. Briscard, in all pathotypes, Karama in 7E18A- and 38E0A+and Kotare in 134E134A+, had mainly recessive genes. Significant negative geperal combining abilities(more resistance)were also obtained for Kotare in 7E18A-, for Briscard in 38E0A+,and for Briscard, Karama, and Kotare in 134E134A+.In conclusion, regarding the high heritability of infection type, it is possible to use the above mentioned varieties in breeding programs in order to reduce the infection type of stripe rust in wheat