Iranian Journal of Field Crops Research
Year:2008 | Volume:6 | Issue:2|Papers Count:35

It has been years that Azospirillum is known to promote plant growth. Phytohormone (especially Auxin) production has the most important role in increasing the yield of inoculated plants. According to this, 60 strains of this genus were isolated, identified, and purified. This ability was evaluated in both qualitative and quantitative assays using colorimetric method and the effects of superior isolate on sweet corn were measured. Results revealed that the abundance and probability of the bacteria isolation is low and 17%. About 31.2% and 100% of Azospirillum strains were capable of producing IAA in qualitative and quantitative methods respectively. In greenhouse experiment, bacteria treatments had significant effects on corn fresh weight, total dry weight, root dry weight and total nitrogen and phosphorus content of the plant. This was considered to be as the result of more lateral root formation which enhances nutrition uptake. In conclusion, the green house results in respect to in vitro achievements show that fortunately it can be claimed that bacteria of the genus Azospirillum can be used widely for not only strategic gramineous plants like: corn, wheat, barely etc. but also for other useful plants.

In order to evaluate effects of saffron residues on wheat, rye, vetch and bean, an experiment was conducted in Research Greenhouse of College of Agriculture, Frdowsi University of Mashhad, in 2005. The type of design was split factorial arrangement of treatment based on randomized complete block design with three replications. Main plots included of four crop species, wheat, rye, vetch and bean, and sub plots were saffron corm and foliage, and amount of saffron tissue added to the soil (4.25, 15, 30 and 75 g of grounded tissues in 1.5 kg soil). Results showed that source of saffron tissues and the amount of added tissue to soil, had a significant effect on some of the studied factors in four crops. With increasing the amount of saffron leaf tissue added to the soil, in compare with control, chlorophyll percentage, plant height, leaf surface area, shoot and root biomass were increased, but with increasing the amount of saffron corm tissue  compare with control, all studied traits were decreased. Summer crops (vetch and bean) were affected by saffron corm and foliage tissues less than winter crops (wheat and rye). In conclusion, saffron corm and foliage residue had a pronounce allelopathic and promotive effect on the studied crops.

Study of genetic diversity of rice is very important for rice breeders. In this study 64 genotypes for 14 agronomic traits were evaluated. Phenotypic variation coefficients of some of traits were high which showed essential variation in this traits. Principal component analysis detected 6 components which explained 74.66 percent of the total variations. The first component was related to generative traits such as number of spiklet per panicle, number of full grain per panicle, date of 50% flowering and length of panicle. In the third component, the date of complete maturity with -0.730 has negative effects on yield. Correlation analysis of morphological traits indicated a negative and significant relationship between early maturity and plant height, which showed early maturity cultivars, had higher plant type. Results of stepwise regression analysis for early maturity indicated that three traits such as date of 50% flowering, number of full grain per panicle and plant height showed higher variation and explained 54.3 percent of total early maturity variations. All traits were classified into 2 groups, by cluster analysis and traits belonged to early maturity classified as a sub-group. Genotypes were classified into 4 groups by using method of Wards minimum variance and squared Euclidean distance. Native cultivars from the view point of early maturity and yield components had useful information for rice breeding.

In order to evaluate growth and yield variations of safflower (Carthamus tinctorius L.) in different planting dates, a factorial experiment with four replications was conducted at University of Birjand, Iran. Three spring cultivars of safflower, including a local variety (Isfahan) with two foreign cultivars (Gilla and CU1) were sown at 4 and 19 Apr. and 4 May. Results showed except height of first branch, other morphological characteristics were affected by planting dates. The node number, height of first branch, and length of internodes varied considerably between cultivars, with a constant response of cultivars in different planting dates. The total and fertile capitula were not differing between cultivars, but Isfahan had the most kernels per capitulum with the lowest kernel weight and CU1 showed just the reverse response. Earlier planting date lead to more produced and fertile capitula, and formation of more kernels in secondary capitula, with the highest produced and fertile capitula for Gilla, the highest total kernel per capitula for Isfahan, and the highest kernel weight for CU1, especially in the first planting date. The stem height and diameter and branches numbers showed high correlation with seed yield; however, number of primary capitula showed the highest correlation with yield and was accounted for 90 percent of yield variation. According to these results, planting Isfahan variety at the first possible time, due to its nativeness and high adaptation to this arid climatic zone, provide an opportunity for producing higher yields in comparison with foreign cultivars.

In order to study the cardinal temperatures of lambsquarter (Chenopodium album), purselane (Protulace oleracea), crab grass (Digitaria sanguinalis) and also predicting their emergence time within the fields an experiment was conducted in Weeds Research Labratory, Faculty of Agriculture, Ferdowsi University of Mashhad in 2005.The type of experiment was a completely randomized design with 9 treatment and three replications was used. Treatments consisted of 9 constant temperatures (5, 10, 15, 20, 25, 30, 35, 40 and 45oC) with 50 percent relative humidity and constant light radiation for 14 days. The germinated seeds were counted everyday and the rate of germination percentage, cumulative germination and cardinal temperatures were calculated. The cardinal temperatures including base temperature (Tb), optimum temperature (To) and cieling temperature (Tc) for lambsquarter was 4,29.5 and 43.3oC for purslane 11.8,35 and 49.3oC and for crab grass it were 14.16,25/6 and 41.3°C respectively.The results indicated that lambsquarter with lower Tb and To is able to germinate when it is cooler and thus it will be dominant early in the season, Gradually, when the weather is getting warmer, purselane and then crab grass will dominate and invade the fields. On the whole, due to differences in physiologic of aspects and rate of weed growth the germination peak differs within fields.

Pot marigold (Calendula officinalis L.) is a medicinal herb whose dried flower heads are used to heal wounds. In order to study the effects of sowing dates and plant density on grain and flower yield of pot marigold, an experiment was conducted at Agricultural Research Center of Islamic Azad University, Birjand Branch in 2005. Three sowing dates (30 March, 14 April and 30 April) and three plant densities (plant distances on row were 10, 20 and 30 centimeters) were compared in a split- plot experiment based on a randomized complete block design with 3 replications. Seed and flower yields were significantly different at planting dates and plant densities. Sowing date had significant effects on flower and seed harvest index. The latest sowing dates had the highest flower and seed harvest index. Plant density had not significant effect on flower harvest index, but the effect on seed harvest index, was significant. In total our result showed that the first sowing date with 25 plants/m2 had the highest grain and flower yield.

As a part of soil biodiversity, mycorrhiza has an important role on soil function. For assessment of agricultural practices on spore density and diversity of mycorrhiza, a study was conducted in winter wheat fields on Shirvan, Mashhad and Gonabad, three regions of Khorasan. In each region, high and low input fields of winter wheat and a natural system for comparison were selected. Use of agricultural inputs was criteria for selection of low and high input fields in each region. Soil sampling was done on fields and natural systems. Organic matter and spore density of mycorrhiza were measured in soil samples. Percent of soil organic matter in all systems was low, but in agroecosystems was greater than in natural system. Mean spore density of mycorrhiza in the soil of Shirvan, Mashhad and Gonabad was 118, 99 and 76 per gram dry soil, respectively and was affected by region and soil organic matter. Soil spore density in agroecosystems was greater than natural systems and was affected by soil organic matter and plant production. Species richness of mycorrhiza in high input and natural systems of Gonabad was 4 and in other systems were 5. Results showed that agroecosystems improved conditions for mycorrhiza and efficient use of these services.

Application of biofertilizers, especially plant growth promoting rhizobacteria (PGPR) and mycorrhiza fungus is one of the most important strategies for plant nutrition compared to chemical fertilizers, especially in sustainable management of agroecosystems. In order to investigate the effect of Azotobacter and Azospirillum bacteria and Mycorrhiza fungus on the growth indices of black cumin (Nigella sativa L.), a field experiment was conducted at the Agricultural Research Station of Ferdowsi University of Mashhad during growing season of 2007. A randomized complete block design with three replications was used. Treatments included: (A) Azotobacter paspali, (B) Azospirillum brasilense, (C) the fungus of Glomus intraradaices, C+A, C+B, A+B, A+B+C, and control without using bio-fertilizers. The Azotobacter and Azospirillum inoculations were applied as liquid and the Mycorrhiza inoculation was applied in solid form on the treated seeds with Arabic resin immediately before planting. The Arabic resin was applied to increase the adherence of Mycorrhiza to seeds. In all treatments except control, the amounts of 15 mg of each bio-fertilizer were applied for 110 g of seeds. The results indicated that the inoculation of black cumin with biological fertilizers significantly increased plant height, leaf area index, dry matter accumulation and crop growth rate compared with control. The maximum plant height was observed in Azospirillum+Mycorrhiza at 89 days after emerging. The highest and lowest leaf area index was observed in B+C (0.37) and control (0.22) treatments, respectively. The fast period of vegetative growth and dry matter accumulation were observed at 40-89 days after emerging with a small decline afterwards until physiological maturity. The maximum and minimum amounts of dry matter accumulation were recorded in the B+C treatment with 66.0 gm-2, and control with 38.3 gm-2, respectively. Crop growth rate reached to its peak in 82 days after emergence followed by a decreasing trend afterwards, its highest and lowest were observed in the B+C treatment with 14.5 gm-2d-1 and control with 5.8 gm-2d-1, respectively. Also, net assimilation rate reached to its peak in 61 days after emerging followed by a decreasing trend afterwards until the end of growth and its maximum and minimum were recorded in B+C treatment (47.2 gm-2d-1) and control (39.7 gm-2d-1), respectively. Further, investigations on quantity and quality of medicinal plants including black cumin in association with biological fertilizers effects will provide additional information. 

Nickel as a heavy metal is considered a fatal and toxic element for humans, animals and plants. However, some plants are known as hyper accumulator for nickel and sometimes seem to be useful for plant growth. Thus, investigation on the effect of nickel on plants' growth is an issue of importance. In this paper, we have studied the effect of different nickel concentrations on parsley growth and morph-physiological characteristics and its effect on absorption of some macro elements in this plant. Seeds of parsley were germinated in germinator and seedlings were transferred to hydroponics culture. The seedlings were grown in Hogland solution with different nickel concentrations (in form of nickel nitrate) of: 0, 0.25, 0.5, 0.75, 1, 1.5, 2 and 4ppm. A completely randomized design with 8 treatments and 7 replications per treatment was used. Twelve weeks after treatments, morph-physiological characteristics including SPAD number, plant biomass, length of shoot and root, leaf area, leaf number and stomatal resistance were measured. The amount of absorbed nickel in plant foliages and roots of different treatments were also measured. The results revealed that the application of different nickel concentrations were decreased SPAD number, plant biomass, leaf area and leaf number, but the stomatal resistance were increased. Increase of nickel concentration resulted increasing Ni concentrations of plant foliages and roots. Nickel with 0.75ppm concentration or higher imposed a toxic effect on parsley as general wilting and significant reduction in most morph-physiological characteristics.

In order to study the effects of sowing dates and  different fertilizers on yield, yield components, and oil percentage of castor bean, an experiment was conducted at Experimental station, College of Agriculture, Ferdowsi University of Mashhad, Iran in years 2004-2005. The experimental treatments comprised all combinations of four sowing dates (11 April, 25 April, 8 May and 22 May) and three different fertilizers (cow manure (30 tons/ha), compost (30 tons/ha), chemical fertilizers (100 kg/ha N and 250 kg/ha of super phosphate) and no fertilizer as control. Different characteristics such as plant height, main inflorescence height, number of inflorescence per plant, number of secondary stems per plant, number of capsules per plant, number of grain per plant, grain weight per plant, 100 seed weight, grain yield, oil percentage and oil yield were recorded. A factorial arrangement based on a randomized complete block design with three replications was used. The results showed by delaying sowing date grain yield, seed oil percentage and oil yield were decreased, but there was no significant differences between 25 April, 8 May and 22 May sowing dates. Harvest index and 100 seed weight did not affect by neither sowing dates nor fertilizer treatments. The highest number of branches per plant, number of fertile inflorescences per plant, number of fertile capsules per plant, number of grain per plant, grain weight per plant and biological yield were obtained at 8 May sowing date on chemical fertilizer. Percentage of seed oil, grain yield and oil yield was higher at the first sowing date (11 April) in compost and chemical fertilizer treatments.

In order to study the effect of different sowing dates and different irrigation regimes on morphological characteristics and grain yield of chickpea (cultivar 3279 ILC) (Cicer arietinum L.), an experiment was conducted at Agricultural Research-Education Station of Shahid Rejaee, Neyshaboor during 2001-2002. Four irrigation regimes (without irrigation, one time irrigation (at early flowering), two times irrigation (at early flowering  and 50% flowering) and control (irrigation every 10 days)) and  Four sowing dates early planting (autumn, Entezari), and late planting (spring and delayed) were compared in a spilt plot layout based on randomized complete block design with four replications per treatment. The results showed that all chickpea plants with delayed sowing date on combination of without irrigation, one time irrigation (at early flowering) and two times irrigation (at early flowering and 50% flowering) were dead. By delaying sowing date, duration between the time of starting flowering and maturity became shorter. Plant height, distance of the first pod from earth surface, distance between nods, number of nods per plant, number of stems per plant, number of pods per plant, number of pods with one, two and with no seed per plant, number of seeds per plant, seed weight per plant, 100 seed weight and grain yield were increased when the number of irrigation increased. By increasing the growing season, plant height, distance  of the first pod from earth surface, number of nods per plant, number of stems per plant, number of pods per plant, number of pods with two and without seeds per plant, number of seeds per plant and seed weight per plant were increased. The autumn sowing date had the highest and the spring date had the lowest grain yield. The highest plant height, number of nods per plant, number of stems per plant, number of pods per plant, number of pods with one and with no seed  per plant, number of seeds per plant and grain yield were obtained at autumn sowing date with control treatment (every 10 days irrigation). Plants of spring sowing date with no irrigation treatment because of decreasing growth period and declining water availability had the lowest plant height, number of nods per plant, number of pods per plant, number of pods with one seeds per plant, seed weight per plant, 100 seed weight and grain yield.

This study was conducted to assess the sources of genetic and phenotypic variability of peanut varieties. 15 morphological and agronomic traits were measured on 39 peanut varieties. These traits include oil yield, 100 grain weight, 100 pod weight, grain length, grain width, pod length, pod width, grains in pod, grain: pod weight ratio, grain: pod volume ratio, oil%, pods per plant, leaflet length, leaflet width and leaflet length: width ratio. The multivariate data set was analyzed by Canonical Discriminant Analysis (CDA) in combination with a clustering procedure. In this analysis, the first two canonical variates were significant and canonical variates indicated that 100 grain weight, oil yield, 100 pod weights, grain: pod volume ratio and pods per plant are the most differentiating traits among the varieties. The canonical variates were used to cluster the varieties into three subgroups. Canonical Discriminant Analysis was useful in identifying the genetic variation and the traits that better describe the variation among Peanut varieties. Cluster analysis was successful in differentiating the varieties into similar subgroups on the basis of the measured traits.

AField experiment was conducted at Research Farms of Center of Excellence for Special Crops, Ferdowsi University of Mashhad, Mashhad, Iran, in 2006 to evaluate the effect of planting density on forage and grain yield of kochia (Kochia scoparia). Experimental design was a randomized complete block with split-plot arrangement of treatments, with three replications,  where different planting densities (10, 20, 30 and 40 plant m-2) were assigned to main plots and number of cutting (including a single cutting, two cutting and no cutting i.e. allowing the crop to grow until maturity) allocated to sub-plots. At each harvest date (cutting) the biological yield, leaf and stem dry weight, plant height, number of branches and the individual plant biomass were measured. Grain yield and thousand seed weight were also determined at the end of growing season. Result showed the highest biological yield and leaf and stem dry weights for kochia obtaind at 30 plant m-2. The total biomass, leaf and stem dry weights, plant height, numbers of branches were greater for the first cutting as compared to the second cutting. Planting density and cutting number interacted to affect the leaf dry weight. At physiological maturity stage there were no significant differences among planting densities for plant height and number of branches. The best planting density, in terms of biomass production and leaf and stem dry weight, was found as 30 plant m-2, while for grain production a planting density of 20 plant m-2 could be recommended.

Cold tolerance of 14 wheat cultivars under field conditions was investigated. Cultivars including Anza, Bezostaja, Pishtaz, Tous, Zagros, Zarrin, Shahryar, Falat, Ghuds, Glenson, Maroon, Navid, Niknejad and MV-17 were planted in a complete randomized block design with 3 replications in the experimental station of college of agriculture, Ferdowsi University of Mashhad in autumn of 2004-2005. Growth stage of plants and chlorophyll content were measured before cold and winter survival, plant height, yield components and seed yield were measured at the end of growing season. Results showed that despite of a relatively extreme cold (-9.2oC), most of the cultivars tolerated winter and only Zagros and Maroon with 93.3 and 73.3%  winter survival, respectively, suffering winter damage. Toos cultivar had the highest seed yield and Maroon and Zagros cultivar had the lowest yield. Seed yield had the positive correlations with spikelet number per spike (r=0.85***), and 1000-seed weight (r=0.85***). Results of this experiment suggested that Glenson had the most level of cold tolerance and Maroon was the coldest sensitive cultivar.

In order to evaluate resistance of Phalaris minor biotypes, sampled from wheat fields of Fars and Golestan provinces, to ACCase inhibiting herbicides, a dose-response study was conducted under controlled conditions in greenhouse of Ferdwosi University of Mashhad. The results indicated that AR, SR3, MR4, FR2, FR4, and FR8 populations of Fars and GR2-1 biotype from Golestan have been resistant to diclofop-methlyl. Different levels of resistance maybe are because of involving different mechanisms in studied populations. AR, SR3, and MR4 showed a cross-resistance to the applied herbicides. These biotypes indicated a 5- to 11-fold and a 7- to 8-fold increase in resistance to diclofop-methlyl and clodinafop-propargyl, respectively compared with the susceptible biotype. Among these biotypes, SR3 showed the highest resistance to both herbicides.

In order to evaluate heritability and gene action for resistance to Bean common mosaic virus (BCMV) four crosses were established among bean genotypes with various resistances to BCMV. All four crosses were extended by other generations-F1, F2, backcrosses- to establish four families. Four separate experiments were conducted in RCB design with 3 replications in greenhouse conditions. Inoculation was accomplished 2 weeks after sowing and sampling for ELISA test were performed 3 weeks after inoculation. Studies on the inheritance of resistance to BCMV using generation mean analysis and generation variance analysis indicated that additive components and epistasis ([i], [l]) play a major role in these crosses. Also, average broadsense and narrowsense heritabilities were 0.77 and 0.64 respectively. These data were showed importance of additive components for this trait. Therefore, selection for high resistance in breeding projects about this trait could be effective.

The effect of defoliation on root yield and quality of sugarbeet (Beta vulgaris L.) was examined in a field study in Research Station of Faculty of Agriculture, Ferdowsi University of Mashhd during 2005 growing season. The experiment was conducted as a split plot on the basis of randomized complete block design with three replications. Time of Defoliation (May 16th, May 31th, June 18th, July 9th, July 31th, and August 20th) were allocated to main plots and defoliation severity (0, 30, 60, and 100%) were assigned to subplots. Results showed that root yield, shoot and root dry weight and sugar yield were influenced by defoliation time. However, defoliation time had no significant effects on sugar white content and white sugar yield. Effects of defoliation on plant growth was more pronounced in mid season when about 1500 degree days was accumulated, compared to early or late season. Defoliation intensity resulted in a significant decrease in root yield, shoot fresh weight, root and shoot dry weight, sugar and white sugar content, and white sugar yield compared with undefoliated control, but molass sugar was increased in all defoliation intensities. Sugar and white sugar percent were significantly affected by defoliation time x intensity interaction. Complete defoliation (100%) on July 30th and Auguat 19th led to 18 and 21% reduction in sugar and 29 and 28% in white suagar, respectively. However, 100% defoliation in July 8th resulted in 6 and 8% increase in sugar and white sugar, respectively.

In order to compare different weed management methods in sugar beet, two experiments were conducted at mashhad for two years in 2005-2006 and 2006-2007. Each experiment designed as a Complete Randomized Block with three replication. The treatments include: Metamitron (Goltix) plus Phenmedipham (Betanal) (Gol+Bet), Goltix plus Cultivation (Gol+Cu), Disk plus Betanal (Di+Bet), Disk plus Cultivation (Di+Cu), Cover Crop plus Betanal (Co+Bet), Cover Crop plus Cultivation (Co+Cu), Weeding (W) and Betanal plus Weeding (Bet+W). Samplings were taken at three stages early season, after imposing the treatments and late season. Results showed that at early season in two experiments, density of weeds was lower in cover crop and disk treatment compared with other treats and the second sampling in first experiment, weeding and disk plus cultivation of treatments with 21.5 and 26.6 respectively plants per m2 and in second experiment year, weeding and application betanal plus weeding treatments, with 14 and 17.8 respectively plant in m2 showed the lowest. In the second experiment year, minimum and maximum sugar beet yield were obtained with cover crop plus betanal and weeding with 43 and 104 ton per hectare respectively. The lowest yield was obtained in check plots with 3.5ton per hectare. Maximum sugar contain (19.35%) was obtained in betanal herbicide plus cultivation treatment and minimum (14.88%) was obtained with hand weeding treatment. However maximum sugar beet yield was obtained with betanal plus weeding (17.85 ton per hectare) and the minimum with cover crop plus betanal (7.5 ton per hectare).

In order to evaluate agroecological criteria for possible domestication under cropping conditions, a primary survey was made in natural habitat of Tandureh national park in North Khorasan. In this case, biological criteria of plants including plant density, height, biomass and crown diameter was measured. Also in 2 separate field trials, agronomic criteria of this species were studied for two years (2006 and 2007) in experimental field of Institute of Plant Sciences of Ferdowsi University of Mashhad. In the first experiment, treatments were including  dates of seed direct planting and 3 density (13, 17 and 25 plant per m2) and the second experiment plant density (13, 17 and 25 plant per m2) and date of transplanting (17 October and 5 May) in  randomized complete block design with three replication was evaluated. Transplants were transferred in rows with 20 cm apart and the proper densities were arranged on the rows with 20, 30 and 40 cm between each plant. In another trial in 2007, the effect of different levels of manure (10, 20 and 30 ton per hectare) and irrigation intervals (14, 21 and 28 days) on agronomic criteria of this species was investigated. In the natural habitat, this plant grows in altitude 1000-1100 m, on poor loamy soil with average density of 4 plants per m2, height of 17 cm, crown diameter 15 cm and dry matter yield of 11 g.m2. Field experiment indicated that direct seeding is not successful and autumn transplanting was superior to spring transplanting and plant performed much better in the second year compared with the first year. Also performance of species in terms of yield, height and crown diameter was better under field condition compared to natural habitat. However essential oil content in the first year was 50 percent lower under field condition compared with nature. Different levels of manure and irrigation intervals did not affect agronomic criteria of Teucrium polium L.

The influence of late-season drought stress on grain yield, its components and some other morpho-physiological traits was evaluated using 151 F3 families obtained from crossing a drought tolerant genotype with a drought susceptible genotype at Research Farm of Isfahan University of Technology in 2003-2004. Two separate randomized complete block designs each of which having two replications allocated to each of moisture stress and irrigated (non-stress) environments. Drought stress significantly affected grain yield, its components, harvest index and relative water content (RWC) traits. Analysis of variance of combined data revealed significant differences among the environments for the traits that related to reproductive stage. The genetic and phenotypic correlation coefficients between grain yield and most of traits such as RWC and excised leaf water retention (ELWR) were significant. Based on stepwise regression analysis, biological yield and harvest index were the most efficient traits in explaining the grain yield variation under normal and stress environments, respectively, Factor analysis of data from the two environments indicated that components were related to phenologic characters, potentional of plant production, harvest index and yield components, plant height and physiological traits. The amount of variation explained by these components varied for two environmental conditions where yield components, plant height and physiological traits had a high impact under stress environment. Cluster analysis of families based on all of traits for two environments defined desirable clusters. This cluster divided families into five groups each of which desirable for a particular trait such as high or low grain yield in stress environments, early maturity, late maturity, high RWC and high ELWR.

For increasing the effectiveness of weed management and more understanding of weed population dynamics, spatial distribution needs to more attentions. Infestation levels and spatial distributions of Amaranthus blitoides, Chenopodium album and Solanum nigrum were studied in four 10x30 m corn fields. N-fertilizer was applied in two method of whole application at the time of corn planting (T1 and T2) and equal split application at the time of corn planting and at six-leaf stage (T3 and T4). One of either fields with the same method of N-fertilizer application, received herbicide too (T1 and T3). Weeds Samples were taken four times at the intersection of 2.5m square grids with 23days interval. The first sample was taken June 24, before top-dressing and herbicide application in related plots. For studying weed spatial distribution, the parameters of appropriate semivariogram model were calculated and weed contour maps were constructed by using kriging. The weed semivariograms fitted spherical and exponential models, over four sampling times and fields and spatial autocorrelation during growing season, was moderate to strong. In early growing season, Amaranthus blitoides was the dominant weed species in all fields, but lower density was recorded for Chenopodium album and Solanum nigrum. At the first sampling time, mean density of A. blitoides and S. nigrum in fields with split application of N-fertilizer was respectively more- and less than fields with whole application of N-fertilizer. In the case of C. album an evident difference wasn’t observed. Herbicide application in related plots considerably reduced the density of three mentioned species; however density never became zero. In the majority of cases the lack of herbicide application causes to increase in population density at the second sampling time. Spatial structure was observed in all three species and study on contour maps confirmed the existence of patches that the density was high in their center, but decreasing gradually toward edges. In general, despite of some displacement, structure and location of patches were kept and possibly these places were the locations for weed emergence in next year. So site-specific herbicide application and exploitation of its advantages may be possible; however, more researches are necessary.

In order to evaluate the effects of time (20, 40, 60 and 100 days after sowing) and intensity of defoliation (0, 33, 66 and 100%) on a corn cultivar (three way cross 647), a complete randomized block design with split plot arrangement and three replications was conducted in Experimental Field of Faculty of Agriculture Ferdowsi University of Mashhad. The main plots were consisted of defoliation time and the sub plots were consisted of defoliation intensity. For this purpose leaves were defoliated at 33, 66, and 100% and at the end of experiment, different morphologic and physiologic criteria such as number of leaves per plent, total dry matter and plant components dry matter, seed yield and yield components and also harvest index were evaluated. Results indicated that defoliation at the early stage of crop growth (20 and 40 days) and at the end of crop growth (100 days) showed no effects on most of criteria measured. However at the middle of growth period, defoliation reduced these parameters. Intensity of defoliatin up to 66% had no effects, but 100% reduced all those parameters. Therefore, it appears that by defoliation up to more the 50% of plant leaves, plants could recover and appears as a normal plant, but with 100% defoliation this was not happened. Defoliation at early stages had no negative effects, because regrowth of leaves could have compensated for this type of damage. At the end of growing season, plant cycle was completed and so defoliation had no negative effects on growth and development, while at the middle stage (60 and 80 days) the negative effect was due to the fact that plants could not recover completely from defoliation.

A field experiment was conducted to investigate different weed management methods for reduce herbicide use in sugar beet at Arak Agriculture & Natural Research Center in 2005.Trial was designed in split-plot and consisted of 18 treatments with four replication. Each plot contains four 50 cm. rows. distance in inter row and 25cm. between plants on row. Main factor was inter row (with & without) cultivation. Sub factors were herbicide dosages in two application methods (band & spread application). Herbicides were Desmedipham (Betanal A. M.) plus Chloridazon (pyramin) that used as tank mix application. Inter row cultivation done with tender wheal tractor and spraying by stable pressure charging sprayer with drop raining nozzle. The result showed no significance difference between main plots in crop characteristics evaluated. Highest root yield, plant total weight and more reduce weed biomass and control was obtained with 100 and 75 percent of the recommended dosages of the herbicide in spread application and 75 percent recommended dosages in band application. Therefore, in order to decreasing herbicide use toward environmental safety aspects and increasing economical profit for farmers, it is recommended to use 75 percent herbicide dosage in spread and band application in integrated with cultivation instead of complete dose alone in sugar beet.

Chickpea is a traditional pulse in arid and semi-arid regions. Germination and stand establishment are important factors for determining final density of plant in dry regions. This research was conducted using a randomized complete design with factorial arrangement of four drought levels and control level (including: 0, -4, -8, -12, -16 bar) and twelve chickpea genotypes, with 3 replication. This experiment was conducted to study the impact of drought stress on chickpea germination, in a Physiology laboratory of Ferdowsi University of Mashhad in 1384. Drought levels imposed a significant reduction on all measurement parameters including, percent and rate germination; dry weight, radicle and plumule length, radicle to plumule ratio, endosperm consuming. Among the levels of water potentials tested, -4 and -8bar because of the best variety between measurements parameters were best treatments for evaluating drought stress of chickpea genotypes. Radicle and plumule did not form in heavy drought stress. Among genotypes tested, JAM, KARAJ12-60-31, ILC482 and MCC101 were the best genotypes under simulated drought condition. We can say these genotypes are suitable for drought situation that another growth stages are tested in field experiments.

In order to prediction competitive effects of redroot pigweed on yield and yield components of grain sorghum by observation of relative leaf area an additive series experiment (response model) with factorial in randomized completely block design (RCBD) were conducted in 2005 growing season at farm research of khorasan Agriculture and Natural Resources Research Center (Torogh Research Station). Two factors were involved in the experiment, redroot pigweed density in four levels (0, 2, 8 and 16 plant/m2) and sorghum density in three levels (10, 15 and 30 plant/m2). kropff three parameter model was used for data analysis and predicting of competition and relative yield loss coefficient (q). Result of this study indicated that sorghum is sensitive in competition and has sever damage. The economical yield reducing at 10, 15 and 30 plant/m2 density due to red root pigweed competition was 0.11, 0.38 and 0.22 kg/m2 respectively, where as the biological yield loss was 0.6, 1.27 and 1 kg/m2 .Prediction of model from relative yield loss coefficient (q) indicated high competitiveness of pigweed and also faster leaf area spreading. Result showed that this model is very suitable to describe competition effects and to determine relative yield loss coefficient (q) by observation of relative leaf area.

To study weed species diversity and community structure in wheat fields of Khorasan province, a four-year field trial was conducted from 2003-2006 in Khorasan province, Iran. during jointing stage to heading stage of wheat. Density, frequency and homogeneity of weed species in 5-10 randomly dropped 0.5×0.5 quadrates in 259 fields of 21 cities were determined. Data were analyzed by principal component analysis and clustered by hierarchical complete linkage method. The results showed that weeds of wheat fields were belong to 26 families and 120 species. The majority of weed species were of Asteraceae (20 species) and Poaceae (25 species) amongst dicotyledonous and monocotyledonous, respectively. Nishabour and Nehbandan had the most and the least diversity by 52 and 4 species respectively. Mashhad and Quochan showed the highest similarity index (70%) for weed diversity. Esfarayen had the highest shanon-weiner (2.93) and simpson (1) indices between the cities. however, Nehbandan had the lowest shanon-weiner (0.57) and simpson (0.71) indices. Biplot of the first two principal components (covered 61.4%, and 24.8% of variances, respectively) showed that weed homogeneity and frequency had more correlation with each other than weed density. By considering 75% similarity, cities were grouped in two clusters for weed density, homogeneity and frequency in wheat fields. Nehbandan was located in one cluster and the rest of the cities were placed in another. Nehbandan had low weed density compare to the other cities because of the warm and dry climatic conditions.