نشریه دانش کشاورزی و تولید پایدار
سال نوزدهم شماره 1 (پاییز 1388)

In order to evaluate the influence of nitrogen (N) rate and weed interference durations on grain yield, yield components and chlorophyll (SPAD) value of soybean, a set of experiments were conducted in the Research Station of the University of Tabriz, Iran, during 2005 and 2006. The experiments were carried out as split-plot, based on randomized complete block design with three replications. Nitrogen application rates (0, 20, 40 and 60 kg/ha) were included in the main plots and 10 weed interference periods (two sets) in subplots. Soybean was either kept free of weeds for Ve, V1, V4, R1 and R3 growth stages (GS) or weeds were allowed to grow for the corresponding periods, and subsequently kept weed free. Weed infested conditions for the entire growing season led to 14.68%, 17.33%, 21.42%, 49.52%, 54.55%, 13.01%, 18.05% and 48.42% reduction in SPAD value of V4, R1 and R3 GS of soybean, pods and grains weight and grain yield, respectively, as compared with full season weed-free control treatments. These traits were positively influenced by increasing N levels and consequently better vegetative growth was observed. However, SPAD value showed a decreasing trend with the progress of soybean GS for all levels of N. SPAD value gradually increased in response to increasing weed-free period compared with the weedy control and gradually decreased in response to increasing weed-infested period compared with the weed-free control. The results suggested that the adverse effect of weed competition on soybean is more apparent at low N levels and increasing the amont N provides a competitive advantage for soybean over to weeds thus high N rates are more beneficial to the crop than to the weeds.

Drought is one of the most important abiotic stresses affecting food production under dryland-rainfed conditions. In the present study, fluorescence parameters as non-destructive methods were used to assess drought tolerance in winter bread wheat. A population of 142 recombinant inbred lines in F8 generation, derived from a cross between Azar2 (Winter type) and 87Zhong291 (Facultative type), was used. Experiment was conducted using randomized complete block design with three replications under rainfed (drought stress) and supplementary irrigation during 2006-2007 seasons at Maragheh Experiment Station of the Dryland Agricultural Research Institute (DARI). The chlorophyll fluorescence characters including minimal fluorescence level from dark-adapted leaves (Fo), maximal fluorescence level from dark-adapted leaves (Fm), variable fluorescence level (Fv), maximum quantum efficiency of PSII photochemistry (Fv/Fm), non-photochemical quenching (NPQ), photochemical quenching (QUE), leaf water potential related to drought resistance (LWP), yield of photochemical energy conversion (YPEC), and performance index (PI) were measured. There were significant differences among genotypes with respect to chlorophyll fluorescence parameters under both conditions. Average grain yield under drought and irrigated conditions were 928 and 2547 Kg/ha, respectively. Under drought condition, grain yield ranged from 272 to 1935 Kg/ha. It varried from 3805.4 and 3804.9 Kg/ha under supplementary irrigation. Grouping of geneotypes based on grain yield revealed significant differences between high and low yielding groups with respect to chlorophyll fluorescence parameters only under drought condition. Based on regression analysis, significant and positive relationships were observed between grain yield and all chlorophyll fluorescence characters except QUE under droght condition. QUE had negative and significant association with grain yield. However, no significant linear relationships was found between grain yield and chlorophyll fluorescence parameters under irrigated condition. Correlation analysis indicated positive or negative significant correlation between chlorophyll fluorescence parameters. The results of present study indicated that chlorophyll fluorescence parameters along with morpho-physiological characters could be used as selection criteria in breeding wheat for drought tolerance.

Supporting agricultural products with some rates of comparative advantage is an important step for non-oil exports development of Iran. The purpose of this study is to identify the agricultural products of East Azarbaijan with comparative advantages by policy analysis matrix (PAM). The effects of exchange rates and global prices on the comparative advantage of the cases are examined. The dry farmed wheat (DFW), dry farmed barely (DFB), and irrigated barely did not show any rates of comparative advantages; while, cucumbers, and tomatoes exposed the highest rates of comparative advantages. The sensitivity analyses of comparative advantage indices with respect to the exchange rates(ER) demonstrate the positive correlation; where, DFW, and DFB had highest response rates; and the cucumbers had the lowest response for ER changes. Sensitivity analyses of comparative advantages with respect to global prices showed the deletion of comparative advantages with 25% declines in global prices of irrigated wheat, and locating the potatoes on breakeven point. Sensitivity analyses of tradable inputs costs confirmed that by increasing the ratio of incomes to tradable input costs decrease the response of domestic resource costs indices as compared with tradable input costs changes.

Chickpea seeds (cv. ILC482) were soaked in distilled water at 17.3C for 8 (P2), 16 (P3) and 24 (P4) hours and subsequently dried back to about 30% moisture content. Germination percentage, germination rate and seedling dry weight for different treatments were determined in laboratory. The field experiment was conducted under different irrigation regimes (I1, I2 and I3: Irrigation after 80, 120 and 160 mm evaporation from class A pan, respectively) in 2006. In laboratory, seed germination rate was increased with increasing hydropriming duration. Maximum germination rate was obtained for P4 treatment, but it was not significantly different from the P3 treatment. Seedling dry weight of hydroprimed seeds was significantly higher than that of control (P1). In the field, rate and percentage of seedling emergence, grains per unit area and grain yield were significantly affected by hydropriming. Rate and percentage of seedling emergence and consequently seedling establishment were improved as a result of hydropriming. Grains per unit area and grain yield were decreased, as water deficit severed. The lowest 1000 grains weight and grain yield per unit area were obtained under I3. However, these traits were not significantly different between I1 and I2. Mean number of grains per unit area and grain yield of plants from primed seeds were significantly higher as compared to non-primed seeds, but the effect of hydropriming period on these traits was not found significant.

The aim of this research was to determine the effect of terminal water stress (arranged in main plots) on nine cultivars and promising lines (arranged in sub plots) regarding grain yield and morphologic attributes in Miyaneh, Iran. A split plot experiment was conducted based on randomized complete blocks with four replicates. Results showed that there were significant differences among genotypes for grain yield in both conditions. Drought affected adversely tiller number, panicle number, grain and 1000 grain weight and grain yield. No significant genotype*drought interaction was observed for the traits under study. Stepwise regression showed that panicle number and grain number per panicle were significantly related to grain yield. Hashemi and Local 1 had greater plant height than the mean but produced the lowest grain yield in both conditions. On the other hand, Saleh and 830 which had lower plant height were high yielding. Hassansarayi, 830, 841, Saleh and Local 2 produced higher grain per panicle and grain weight per plant, but Hashemi and Local 1 showed lower grain per panicle, grain weight per plant and consequently lowest grain yield. Saleh and 830 were found to be the most tolerant genotypes in this study.

This research was conducted in order to determine a relationship between accumulated hours and R&M costs, for 27 conventional tractors in the Misagh Sabz Agri-Industrial. Company that were divided into two models including Massy Ferguson 285 and Universal 650. Required data including the R&M costs and hours of annual usage over the fifteen year period from 1991 to 2005 was collected. By performing regression analysis of the data, mathematical prediction models were estimated for both models of tractors separately and these estimations were performed again for all of the tractors. In the first period of life (about 2000 hours) power model as y = 0.024x1.600 and for the rest of its life quadratic model in the form of y = 0.005x2 – 0220x + 5.659 showed the best fitted models. Results revealed that accumulated R&M costs in percent of purchase price were higher in Universal 650 than the Massy Ferguson 285. To verify the results obtained from this study, a comparison was made between the model presented in the current study and some other national and international studies. Finally, it was shown that accumulated R&M costs as a percent of purchase price were nearly less than that of other previous studies. The reasons are discussed in this paper.

In order to study the effects of different nutrition systems (organic, chemical, integrated) and biofertilizer (PGPR) on grain yield and its component in Sunflower (Helianthus annuus L.) an experiment was conducted using Alestar cultivar at the Research Farm of College of Agriculture, Tarbiat Modares University in 2007. Five levels of nutrition systems including F1 (100% organic), F2 (75% organic+25% chemical), F3 (50% organic+50% chemical), F4 (25% organic+75% chemicaL), F5 (100% chemical) in main plot and two levels of biofertilizer I1 (inoculation) and I00 (control) as subplot were used in a split plot arranged as a randomized complete block design with three replications. Results showed that different nutrition systems and biofertilizer significantly affected grain yield, oil percent and yield, protein percent, 1000 grain weight, number of grains per head and head diameter. The results revealed that the highest 1000 seed weight, number of grains per head and head diameter occur in integrated system F3 (50% organic+ 50% chemical). The grain yield in integrated system was more than organic and chemical systems. Seed inoculants with PGPR (I1) showed an increase in grain yield and yield components as campered to the control (without PGPR). The result reveals that yield and yield components produce better results during the combination of PGPR and integrated system than using either method alone. The highest yield (2890Kg/ha-1) was obtained using combination of PGPR with 50% organic + 50% chemical treatment (F3 I1).

In order to identify the fungi associated with sugar beet cyst nematode, Heterodera schachtii, in W. Azarbaijan province, northwest Iran, a number of 400 fungi isolates were recovered and studied from different stages of the nematode life cycle during 2002-2004. In this paper, 12 identified species belonging to 11 genera are presented as Alternaria alternate, Alternaria malorum, Arthrinium phaeospermum, Arthrobotrys oligospora, Botryotrichum piluliferum, Chaetomium spiralotrichum, Cladosporium oxysporum, Cylindrocarpon destructans, Embellisia chlamydospora, Geomyces pannorum, Stemphylium botryosum and Ulocladium atrum. Among them, two species viz. Botryotrichum piluliferum and Geomyces pannorum are as new records for the mycoflora of Iran. Four species viz. Alternaria malorum, Arthrinium phaeospermum, Botryotrichum piluliferum and Geomyces pannorum are reported from naturally infected sugar beet cyst nematodes for the first time. With dentification of these fungi, they will be considered as biological control candidates of sugar beet cyst nematode.

Salinity is recently regarded as the major abiotic stress for plant and new studies show that Si plays an important role in plant resistance to environmental stresses such as salinity. An experiment was conducted to study the effect of Si and NaCl salinity on the growth, yield and fruit quality of strawberry (Fragaria × ananassa Duch) cvs “Selva” grown hydroponically in the controlled glasshouse. Three levels of NaCl (0, 20, 40 mM) and three levels of Si (0, 1, 2 mM) was factorially combined in a completely randomized design with four replicates. The photosynthesis rate was measured in the flowering stage. At the end of the experiment, the plants were totally removed and biochemical properties such as nutrient concentration, proline content and electrolyte leakage were measured. The results showed that increasing the NaCl Levels, increased the proline content and electrolyte leakage, but reduced the photosynthesis rate. Silicon treatments improved photosynthesis rate and reduced the proline content and electrolyte leakage. In the saline conditions, concentration of N, NO-3, K and K/Na ratio were reduced, however, concentration of Na and Cl- increased. Increasing the silicon in the saline condition, reduced concentration of Na and Cl- in the leaf tissue. Concentration of N, NO-3, K and K/Na were increased by silicon application. Concentration of P was not affected by the treatments. The results showed that, the concentration of Si in plant was increased by Si addition into the nutrient solution, but was reduced in the saline condition. Based on the results of this study the application of Si in a concentration of 1mM could be recommended for salinity stress conditions.

Sunn Pest, Eurygaster integriceps Put. is the most important pest of wheat and barley in Borujerd, north of Lorestan province, Iran. The most commonly employed methods of sampling for this pest are the use of quadrate (absolute estimate) and sweep net (relative estimate). Sweeping is the most convenient sampling method for many arthropods. In this research, spatial distribution and Green’s sequential sampling plan were investigated using a standard sweep net to estimate of population density of sunn pest in rainfed fields of wheat in Borujerd during 2004-2005. Results show that, Taylor's Power Law regression model, provided a more adequate description of variance-mean relationships for sweep net. Taylor's was significantly >1, indicating that nymph stages and new generation adult sunn pest population were aggregated in rainfed fields of wheat. Green's fixed-precision sequential sampling plans were designed for estimating 3rd, 4th nymph instars and 5th nymph instar + new generation adult at three fixed precision levels (0.1, 0.15 and 0.25). These models were validated using 11-13 independent data sets ranging in density 0.4-6.92, 0.91-30 and 0.34-24.21 individual per sample, respectively. To achieve a precision of 0.25 which is generally accepted in IPM programs, it is necessary to take an average sample number (ASN) of 23, 22 and 35, respectively. As the precision level was increased to 0.10, ASN increased to 166, 127 and 190 in above mentioned stages, respectively. Therefore, Green’s fixed precision sequential sampling plan using sweep net, was the most preferred and convenient method to monitoring of nymph instars and new generation adults of E. integriceps in rainfed fields of wheat.

Allelopathic effect of weeds is one of the important limiting factors that affects the growth and yield of medicinal plants. In this study, the effects of aqueous extracts of different organs of Lambsquarters (Chenopodium album L.) and Common cocklebur (Xantium strumarium L.) (shoot, root and whole plant) (2%W/V) were investigated on emergence percentage, growth and development and essential oil content and yield of summer savory (Satureja hortensis L.). A greenhouse experiment was carried out in randomized complete block design with five replications. Results showed that the aqueous extracts of lambsquarters shoot and common cocklebur whole plant reduced emergence percentage of summer savory. Aqueous extract of different organs of both weeds had significant effect on morphological traits as well. In this regard, results indicated that the aqueous extract reduced summer savory bush height, number of leaves per plant and dry weight of shoot and root. Despite of increase in essential oil content of summer savory, essential oil yield of summer savory was reduced by different organs aqueous extracts of both weeds.

According to increasing the demand for irrigation water in Iran and limitation upon its supply, planners and utilizers should consider optimal water resourse utilization. One way is determination of real value of irrigartion water in several agriculture products. In this study using the data for the year 2006-2007 and Translog production functions, production function of wheat and barley were estimated in North Khorasan, Razavi Khorasan and South Khorasan provinces for determination of irrigation real water price in wheat and barley production. It was found that irrigation water price in North Khorasan, Razavi Khorasan and South Khorasan for wheat were 122.14, 2882.24 and 456.30 Irls/m3, respectively and for barley were 703.01, 1343.67 and 112.67 Irls/m3, respectively. Also, step by step adjustment of water price, can lead to optimal use of water in cultivation of the crops and increasing of productivity and efficiency of water as compared with current price.

In any production system, if operations such as sowing and harvesting are not accomplished on time, reductions on yields and/or product quality can be expected. Alfalfa mechanization projects similar to other production systems need precise scheduling, planning and management. The basic approach of all scheduling techniques is to form a network of activity and event relationships that graphically portrays the sequential relations between the tasks in a project. Such a network is a powerful tool for planning and controlling a project. It is a consistent framework for planning, scheduling, monitoring, and controlling the project. In this research, GERT Networks were used, because GERT is a powerful tool for the system analyst since it has all the advantages associated with networks and provides an exact evaluation of certain types of networks. With GERT Networks, mechanization project of alfalfa production was simulated and modeled the network before analyzing. Results showed that the network model was able to answer any statistic al the questions concerning the project. Networks model, particularly GERT networks are increasingly be coming a powerful tool for modeling, scheduling, planning, controlling and analyzing of agricultural mechanization projects

Torbat-e-Jam is one of the main agricultural producer cities in Khorasan-e-Razavi province. More than 80 percent of cultivated areas are irrigated and about 90 percent of that area is irrigated by groundwater, which would result in lowering groundwater table about 1.44 m annually, that wasn’t renewed by rainfalls. These conditions would appear in negative water balance. Then continuity of present crop pattern in long run is not possible. In this study a crop pattern introduced by using AHP model and knowing farmer's mental priorities and decision-making indices in order to stabilize their income and also reduce groundwater depletion. Results indicated that mental priorities of farmers are respectively: net income (profit), amount of water use, production costs and labor employment. In the proposed crop pattern, water use would decrease by 8.84%, gross income would increase to 1.06%, production costs would increase to 11.7% and employment level was unchanged. Also governmental protection policies like input subsidies in short run and increasing productivity of irrigation system in long run is suggested to encourage farmers accepting this crop pattern.

The variable nitrogen fertilization in the field is an important aspect of precision management of crop production to increase fertilizer efficiency and to reduce the rick of environment pollution. This technology, however, requires online determination of plant nutrient status in the field. In this study for the first time in sugar beet, a color image analysis was performed to estimate plant nitrogen status. The experiment was carried out in a phytotron and nitrogen was applied at six levels (0, 100, 200, 300, 400 and 500 kg/ha) to the sugar beet grown in pots sized 22cm diameter. Chlorophyll index of the leaves was measured by a chlorophyll meter (SPAD). Two color and one gray level models were developed to estimate sugar beet leaf SPAD values based on the color images captured from sugar beet leaves using with a digital camera. The gray level model indicated a reasonable relationship (R2=0.79) to estimate the sugar beet leaf chlorophyll with a lower analysis time (half of the color models), however the 2R-B model (R2=0.93) was considered more reliable approach for estimating the chlorophyll level of sugar beet