Iranian Journal of Field Crops Research
Year:2006 | Volume:3 | Issue:2|Papers Count:17

Effects of different periods of weed control in paddy rice (Oryza sativa L.) were studied in Veysian region of Lorestan province in 2004. The experiment was conducted in a randomized complete block design with four replications and 10 treatments of hand weeding in two series included weed free and weed infested plot up to 14, 28, 42 and 56 days after transplanting, plus weed free and weed infested control. Based on 5 and 10% acceptable yield loses, the critical periods were between 11 to 40 and 14 to 30 days after transplantation, respectively.Weed competition before and/or after these critical periods had negligible effects on grain yield of rice. This period, based on growing degree days (GDD) was 198-768 GDD for 5% acceptable yield loss. Increasing periods of weed interference in the early stage of the crop resulted in a steady decline in grain yield. Yield losses equivalent to 47 kg/ha of grain resulted for each day that weed control was delayed between 14 and 28 days after transplanting.

In recent years, weed scientist have paid more attention towards integrated weed management and application of reduced rate of herbicides to prevent environmental pollution. To examine the effect of reduced metribuzin on potato, a field experiment was conducted on a strip split plots based on complete randomized blocks. Design horizontal factor was two tillage systems (conservation, conventional) and vertical factor consisted of 6 weed control treatments (1-full rate herbicide, 2-reduced rate herbicide, 3-hand hoeing, 4-cultivator, 5-combination of 1 and 3, 6- combination of 2 and 4). Results showed that the highest weed number and weed biomass was in cultivator treatment and the lowest grasses was observed in cultivator+ reduced herbicide treatment both in conventional and conservation tillage; in this treatment potato had the highest vegetative growth and performance. Weed biomass of broad leafes and grasses was relatively lowest in reduced herbicide than full rate herbicide. Leaf area, height and branching pattern of potato was negative correlated with weed number and biomass. Generally, integration of cultivator + reduced rate herbicide was most successful practices in weed management of potato production.

In recent years, weed scientists have paid more attention towards integrated weeds management to prevent weed resistance to herbicides. To examine the effect of different weed management systems in potato, a field experiment was conducted on a strip split plots based on 3 complete randomized blocks design. Horizontal factor was two tillage systems (conservation, conventional) and vertical factor was 6 weeds control treatments (1-herbicide, 2-reduced herbicide, 3 weeding, 4-cultivator, 5-combination of 1 and 3 treatments, 6- combination of 2 and 4 treatments). Results showed that the highest yield was obtain in the weeding and cultivator treatments both in conventional and conservation tillage systems. Potato yield was not different in integrated treatments (reduced herbicide+ weeding or cultivator) compared to single treatments (full herbicide dose and reduced herbicide dose) in conventional treatment. Integrated treatment had the highest yield and the lowest weeds number and biomass. Generally, integration of mechanical weeds management with reduced herbicide dose in conservation tillage was the most successful management practice for potato weeds.

In order to study the germination response of three medicinal plants’ seeds, Ajowan (Trachyspermum ammi), Fennel (Foeniculum vulgare) and Dill (Anethum graveolens) to osmotic potential of sodium chloride and polyethylene glycol 6000 under different temperature regimes, two separate experiments were carried out in a factorial arrangement based on completely randomized design with three replications. Levels of temperatures were 5, 10, 15, 20, 25, 30 and 35oC and osmotic potential with four levels of (0, -5, -10 and -15 bars). Results indicated that the effects of species, temperature and osmotic potential and also interactions of species and temperature with stress were significant. Germination rate and percentage and also length of radicle and plumule were decreased as stress intensity increased. Optimum temperature for germination percentage was 15oC and for germination rate, length of radicle and plumule was 20oC. Ajowan and dill seeds showed the highest and lowest resistance to temperature change and osmotic potential. Water deficit had more inhibitory effects on germination rate and percentage and -15 bar caused complete failure in germination. Effect of salinity was more pronounced on length of radicle and plumule compared with the effects of water deficit. In both drought and salinity percentage reduction for plumule length was higher which indicate the higher sensitivity of this trait to stress in comparison with radicle length.

With respect to water shortage in arid and semi- arid regions, the study about drought stress effects on crop plants and selection of resistance cultivars, are among the most important goals in the agricultural researches.In order to examine drought stress effects on millet, an experiment was conducted in Birjand and Sarbisheh, simultaneously. In this experiment, five irrigation treatments (well-watered, drought stress in vegetative stage, in ear emergence stage, in seed filling stage and in vegetative and seed filling stage) and five proso millet genotypes (Native, K-C-M.2, K-C-M.4, K-C-M.6 and K-C-M.9) were compared in a split plot design along with three replications. Drought stress increased grain protein content, leaf rolling index and soluble sugars concentration and decreased seed germination and leaf RWC. Although seed protein content and germination percentage of genotypes were not significantly different, there were some differences among leaf rolling index, RWC and soluble sugar content of these genotypes. The results of this study indicated that leaf sugar content, RWC and leaf rolling index cannot be considered as the only parameters for selection of high yield genotypes. Therefore, it is recommended that some other factors should also be used apart from the above mentioned ones.

In order to study the effects of plant density on yield, yield components protein in four grain sorghum varieties an experiment was conducted as factorial based on completely randomized block design with three replications in Research Field of Birjand Azad University at year 2003. In this study four varieties including “Sepideh, Saravan local, Payam and Kimia, and 3 plant densities 100000, 180000 and 260000 plant / ha were investigated. The results indicated that varieties were significantly different for grain yield, protein yield, biological yield, number of seeds per panicle, 1000 kernel weight, harvest index and protein percentage. The highest grain yield, protein yield, biological yield, number of seeds per panicle and 1000 kernel weight were observed in Saravan local and the highest harvest index was belong to Sepideh and the highest protein percentage was in Kimia. Characteristics such as grain yield, protein yield, biological yield and number of seeds per panicle were affected by density. By increasing of plant density grian yield, protein yield, biological yield increased but seed number per panicle decreased 1000 kernel weight, harvest index and protein percentage did not affect by density. Also interaction between variety and density was significant on seed number per panicle.According to the results of this experiment, Saravan in 260000 plant / ha density is recommended for maximum grain yield and protein yield.

To study the response of Plantago ovata Forsk to organic and inorganic fertilizers a green house experiment was conducted in a completely randomized design with three replications. Organic fertilizers were cow manure (4 and 8 tons/ha) and municipal waste compost (4 and 8 tons/ha) and inorganic fertilizers were N30P10, N30P20, N60P10 and N60P20 kg/ha respectively. The results indicated that yield and yield components of Plantago ovata in organic fertilizers were higher than inorganic fertilizers. Plant height, spike length, grains weight per spike, grains weight per plant, straw weight per plant and grain and straw yields per box were highest in 8 tons/ha municipal waste compost. However percentage of mucilage was highest in plants fertilizerd with cow manure.

Cumin (Cuminum cyminum) is one of the most important medicinal plants in Iran’s dry region. Animal manure in soil prepares essential elements, enhance moisture capacity on soil and increase plant yield. To study the effects of irrigation times and animal manure on yield and yield components of cumin, an experiment was conducted at the Agricultural Research Station of Zahak, Zabol, during years 2003 - 2004 based on a randomized complete block design in factorial with four replications.Factors including irrigation times (I1: two times irrigation, I2: three times irrigation and I3: four times irrigation) and animal manure (F1: without animal manure, F2: with 20 tons/ha animal manure). By using animal manure, biological yield and seed yield were increased. I2F2 had the highest number of umbers per plant, seed yield, biological yield and the lowest 1000 seeds weight and number of seeds per umber. Differences between I1F2, I2F1 and I3F1 were not significant. The result showed that animal manure decreased irrigation times. Among treatments, I1F1 had the lowest yield and its components.Seed yield and biological yield had positive correlation with number of umber per plant and number of seeds per plant. It showed that numbers of umber per plant is the most important factor on cumin yield.

Glycyrrhiza is an industrial/medicinal plant however, in Iran is known as a weedy species in dry lands and orchards. Germination of Glycyrrhiza seeds collected from Kermanshah and Fars (Zarghan) were studied in a range of temperatures (0, 3, 10, 15, 20, 25, 30, 35 and 40oC). The highest germination percentage for both Kermanshah and Fars populations were obtained at 20 and 25oC while maximum germination percentage of Fars seeds was higher than Kermanshah. At 40oC maximum germination of 27 and 43% was observed for Kermanshah and Fars seeds, respectively. The same trend was observed for germination rate. Time period for 10, 50 and 90% germination was lowest between 20-30oC for both seed populations. Base, optimum and ceiling temperatures were obtained respectively, 2.2, 29.1, and 45.3oC for Kermanshah and 2.4, 29,2 and 44oC for Fars populations.

This research was conducted in a research greenhouse at the College of Agriculture in Ferdowsi University of Mashhad to investigate the impact of five drought levels (-0.3, -3, -6, -9 and -12 bar) on physiological and morphological characteristics of nine chickpea genotypes including MCC101, MCC174, MCC276, MCC477, MCC327, MCC476, JAM, Karaj12-60-31and ILC482. The experiment used 5×9 factorial laid out in randomized complete design with 4 replications. The genotypes were exposed to drought stress 10 days after emergence. Some traits were measured during growth season (including plant height, leaf number, flower and pod number, length and number of lateral branch) that all of them shown significant differences in the first stage of stress between genotypes and then the effects of drought were appeared. In majority of genotypes reduction in the flowering and podding time were observed. Flower number is a favor parameter in the assessment of drought tolerance genotypes. Most measured traits imposed significant differences in all levels of drought stress, genotypes and interaction of them at the end of growth season. The highest amount of all measured parameters were observed in the field capacity (-0.3 bar). Among the levels of water potential tested -3 and -6 bar were the best treatment for evaluating drought stress of chickpea genotypes. Pod and seed weight did not form in heavy drought stress. Among genotypes tested ILC482, MCC276 and MCC 477 were the best genotypes in terms of responsing to drought stress.

Despite the importance of all climatic parameters for crop growth and productivity, temperature and rainfall are more crucial compared to others and almost all climatic and agroclimatic indices are based on these two variables. Climate change will lead to variation in agroclimatic indices and evaluation of this variation is a key to study crop response to future climatic conditions. Length of growing period (LGP) and rainfall deficit index could be used as indictors for assessment of potential impact of climate change of rainfed systems. To study this impact long-term weather data of main rainfed wheat production areas of Iran were collected. UKMO general circulation model was used for perdiction of climatic parameters of selected stations for years 2025 and 2050 based on pre defined scenarios of IPCC for this target years. LGP, length of dry season and rainfall deficit index were calculated from present data and the generated data for target years. The results showed that LGP based on temperature would be increased in all rainfed areas of country. However, including the water availability in the calculation was led to a lowered LGP. Reduction of LGP for the studied stations was in the range of 8-36 and 19-55 days for years 2025 and 2050, respectively. Rainfall deficit index for 2025 and 2050 was varied, respectively at 8.3-17.7 and 21.1-32.3 mm. It was estimated that under climatic condition of years 2025 and 2050 the cultivated areas in the main rainfed production regions of the country would be reduced by 16-25 and 23-33%, respectively.

In order to investigate the effect of different irrigation intervals and plant density on yield and yield components of Black Cumin (Nigella sativa), an experiment was conducted at Research Station, Faculty of Agriculture, Ferdowsi University of Mashhad, in 2002. A split-plot layout based on randomized complete block design with four replications was used. Irrigation intervals (7, 14 and 21 days) were allocated to main plots and different plant densities (150, 200, 250, 300 and 350 plant/m2) allocated to sub plots. Plant height, number of branch per plant, number of grain per plant, number of seed per follicule, number of follicule per plant, grain weight per plant, biomass, 1000 seed weight, grain yield and harvest index were recorded. Results showed that irrigation intervals had significant effects on all of the characteristics with the exception of 1000 seed weight and harvest index (HI).Plant density did not have significant effects on 1000 seed weight, number of seed per follicule and plant height. There were significant differences between biological yield, HI, number of follicules per plant and grain yield of different plant densities. The one week irrigation interval produced more grain yield compared with the three weeks irrigation intervals (752 vs. 355 kg/ha). The greatest grain yield was obtained with one week irrigation interval and 250 plant/m2. It seems that due to the lack of water in the area, 150 - 250 plant/m2 with two weeks irrigation interval is the best combination for Black Cumin grain production in Mashhad.