Valerian (Valeriana officinalis L.) tolerance to some post-emergence herbicides

Valerian (Valeriana officinalis L.) is a medicinal plant, but its cultivation is restricted by weed competition. Therefore, three rates (0.75X, 1X, and 1.25X, where X is equal to the recommended dose of haloxyfop-R (methyl ester), sethoxydim, oxadiargyl, bentazon, oxadiazon, and oxyfluorfen) were applied at the 3–4 leaf stages to valerian plants. This application was done to select the herbicide type and rate for post-controlling broadleaf and grasses weeds in this species. Herbicide injury, Soil-Plant Analyses Development (SPAD) reading, number of leaves per plant, stem diameter, and fresh and dry weights were determined 10, 20, and 30 days after herbicide application. Oxyfluorfen application caused the most herbicide injury followed by bentazon. Injury increased as the rate and the days after application increased. Oxadiazon only caused significant damage 30 days after application under all three rates. Other treatments showed no marked injuries under any rate or date after application, as compared with the control. Effects on other measured traits depended on the trait, herbicide, and herbicide rate. The highest SPAD, leaf number, shoot diameter, fresh weight and dry weight, was recorded under application of 30 mg a.i. ∙ kg–1 soil oxadiargyl and 90 mg a.i. ∙ kg–1 soil oxadiazon, 81 mg a.i. ∙ kg–1 soil haloxyfop-R, 37.5 mg a.i. ∙ kg–1 soil oxadiargyl, 22.5 mg a.i. ∙ kg–1 soil oxadiargyl, 81 mg a.i. ∙ kg–1 soil haloxyfop-R, and 81 mg a.i. ∙ kg–1 soil haloxyfop-R, respectively. To sum up, the results showed that sethoxydim, oxadiargyl, and haloxyfop-R produced no significant symptoms of phytotoxicity or reduction of measured traits. This means that oxadiargyl, haloxyfop-R, and sethoxydim may be used safely for weed control of valerian at the rates used in this experiment under similar conditions

Evaluation of allelopathic potential of safflower genotypes (Carthamus tinctorius L.)

Forty safflower genotypes were grown under normal irrigation and drought stress. In the first experiment, the allelopathic potential of shoot residues was evaluated using the sandwich method. Each genotype residue (0.4 g) was placed in a sterile Petri dish and two layers of agar were poured on that. Radish seeds were placed on agar medium. The radish seeds were cultivated without safflower residues as the controls. The length of the radicle, hypocotyl, and fresh biomass weight and seed germination percentages were measured. A pot experiment was also done on two genotypes with the highest and two with the lowest allelopathic activity selected after screening genotypes in the first experiment. Before entering the reproductive phase, irrigation treatments (normal irrigation and drought stress) were applied. Shoots were harvested, dried, milled and mixed with the topsoil of new pots and then radish seeds were sown. The pots with safflower genotypes were used to evaluate the effect of root residue allelopathy. The shoot length, fresh biomass weight, and germination percentage were measured. Different safflower genotypes showed varied allelopathic potential. The results of the first experiment showed that Egypt and Iran-Khorasan genotypes caused maximum inhibitory responses and Australia and Iran-Kerman genotypes resulted in minimum inhibitory responses on radish seedling growth. Fresh biomass weight had the most sensitivity to safflower residues. The results of the pot experiment were consistent with the results of in vitro experiments. Residues produced under drought stress had more inhibitory effects on the measured traits. Safflower root residue may have a higher level of allelochemicals or different allelochemicals than shoot residue

Effects of wheat-canola intercropping on Phelipanche aegyptiaca parasitism

Parasitic weeds especially Phelipanche aegyptiaca decrease severely the production of canola. This study evaluated the effect of intercropping different wheat genotypes with canola on Phelipanche aegyptiaca growth. Ten wild wheat genotypes with different ploidy levels including TRI11712, TRI19322, TRI18664, TRI19652, TRI565, TRI15593, TRI12911, TRI11554, TRI17606, TRI7259P and seven cultivated bread wheats, namely: Falat, Chamran, Alamut, Baiat, Kavir, Sepahan, Alvand in addition to a canola cultivar called Zarfam were studied. The results revealed that intercropping of canola with wheat could significantly reduce broomrape growth depending on the type of wheat genotype. A significant genetic variation of allelopathic activity in wheat was observed, indicating the contribution of multiple genes conferring the allelopathic trait. TRI565 and TRI12911, TRI15593, TRI18664, TRI19652, TRI17606, TRI19322, and TRI7259 genotypes showed strong inhibitory effects and can be considered as potential allelopathic genotypes to suppress broomrape. The inhibitory potential of wild wheat genotypes was stronger than cultivated wheat genotypes. Alamut, Baiat, Alvand, Sepahan, and TRI11712 possessed strong stimulatory effects on broomrape germination. Such genotypes may be valuable as trap crops for depleting the Egyptian broomrape seed bank

Determination of the critical period of weed control in potato (Solanum tuberosum L.)

Field studies were conducted in north-eastern Iran in 2010 and 2011 to establish the critical period of weed interference in potato (Solanum tuberosum L.) and to investigate the effects of weed interference on weed biomass. The critical period for weed control in potato based on a 5% acceptable yield loss level was calculated by fitting logistic and Gompertz equations to relative yield data. Total dry biomass and total number of weeds increased as the duration of weed infestation increased. The beginning of the critical period for weed control was 19 days after potato emergence in both years. The end of the critical period for weed control in 2011 was 22 days after potato emergence, whereas in 2010 the beginning and end of the critical period for weed control occurred simultaneously. Tuber yields of potato were reduced by prolonged delays in weed removal in both years. The practical implication of this study is that weeds must be controlled during the first 3 weeks of the crop's growing season. Such an approach would keep yield loss levels below 5%

An Assessment of the Effect of Nitrogen Application and Planting Methods on Yield and Yield Components ofLinseed and Berseem Clover Intercropping System

In order to assess the effect of nitrogen application and planting methods on linseed and berseem clover yield and yield components in an intercropping system an experiment was conducted as a split plot based on randomized complete block design with three replications at the Research Farm of College of Agriculture, Isfahan University of Technology, Isfahan, Iran in 2013. Experimental factors included three levels of nitrogen (zero, 30 and 60 kg ha-1) as main plots and linseed and berseem clover planting methods in 4 levels (pure culture of linseed, berseem clover monoculture, mixed cropping) (50%:50%), intercropping row) 50%:50%)) as sub-plots. Results showed that different levels of nitrogen had no effect on the main stem, seed weight and harvest index of both plants, but the number of lateral branches, number of capsules per plant (linseed), inflorescences number per plant (berseem clover), number of seeds per capsules (linseed), biological yield and grain yield were affected by nitrogen fertilizer. Among the methods of planting, pure cultures of linseed and berseem clover with 1604 and 830 kg ha-1 had the highest yield, respectively. Significant difference between treatments was found in the land equivalent ratio, but the highest land equivalent ratio, was archived at 30 kg nitrogen fertilizer application (1.35) and row intercropping treatment (1.32), respectively. According to the results of this research, the use of berseem clover as a nitrogen-fixing plant, intercropped with linseed under 30 kg of nitrogen application per hectare could, probably, be useful for achieving an appropriate grain yield

Effect of Mycorrhizal Inoculation and Pre-treatment with Salicylic Acid at Different Levels of Drought on Morphological Traits and Yield of Flax

The use of plant growth hormones and beneficial microorganisms, could reduce the drought damage. The purpose of this study was to investigate the treatment with salicylic acid and inoculated with mycorrhizal fungi at different levels of irrigation on flax growth. A factorial experiment based on randomized complete blocks design with 3 replications was performed in growth chamber of college of agriculture, Isfahan university of technology and in the years 2010-2011. Treatments were irrigation regimes at 3 levels (100%, 70% and 40% field capacity), mycorrhizae at 3 levels (non-inoculated and inoculated with two species Glomus mosseae and G. intraradices) and salicylic acid in 2 levels (seeds treated with 250 μM concentration of salicylic acid for 8 hours and non-treated seeds). The level of 40% field capacity irrigation reduced the leaf number, root length, root dry weight, height, stem and leaf and total plant dry weight, number and weight of capsules per plant, number of seeds per capsule and seed yield and increased vesicle diameter and percent colonization. Both mycorrhizal species in the three levels of irrigation increased the drought tolerance of the flax but in G. mosseae was more effective. Salicylic acid decreased some of the investigated traits. Inoculation with mycorrhiza and treatment with salicylic acid reduced the investigated characteristics than the inoculation with mycorrhiza and non-application of salicylic acid. 100% field capacity and G. mosseae species were the best irrigation level and mycorrhizal fungi respectively. Therefore it is suggest that application of mycorrhizal fungi especially G. mosseae species increase in the cultivation of flax plants without treatment with salicylic acid, especially in drought conditions because in addition to increased yield, water consumption is also lower and it makes the plant more tolerant to stress conditions such as drought

Effect of rhizosphere bacteria on antioxidant enzymes and some biochemical characteristics of Medicago sativa L. subjected to herbicide stress

Abiotic stresses such as herbicides can affect plant growth and yield. Using herbicide-resistant plant growth-promoting bacteria is a new approach to mitigate these side effects. This study was conducted to evaluate the effect of three native plant growth-promoting bacteria isolated from the Medicago sativa rhizosphere, including Serratia rubidaea (A) and Pseudomonas putida (B), Serratia sp. (C) plus Synorhizobium meliloti (R) and their combinations (AB, AC, BC, ABC, AR, BR, CR, ABR, ACR, BCR, and ABCR) on microbial population, plant biomass, antioxidant enzymes (CAT, APX, and GPX) activities, and hydrogen peroxide and malondialdehyde contents at the presence and absence of imazethapyr herbicide. The results indicated that herbicide application decreased plant biomass but increased microbial population, antioxidant enzymes activities, and the concentrations of hydrogen peroxide and malondialdehyde of all inoculated and non-inoculated plants. Bacterial inoculation in most cases increased microbial population, plant biomass, and antioxidant activities. These increases were more evident under herbicide application. The highest increase in these attributes was achieved by AB, AR, and ABR inoculums in the presence and absence of the herbicide. The microbial population, plant biomass and antioxidant activities were decreased under BC, CR, BCR, and ABCR inoculations. It can be concluded that in addition to growth promotion, these bacteria increase resistance against herbicide stress by controlling free-radical induced oxidative stress and lipid peroxidation through antioxidant enzymes. These findings create new visions in biofertilizer preparation for reducing environmental stresses

The Combined Effect of Different Nitrogen Levels and Planting Arrangement on Weed Interference with Linseed and Seed Berseem Clover Intercropping

Intercropping is one of the effective components of sustainable agriculture. In order to assess the effects of nitrogen application and planting arrangement on linseed and berseem clover leaf area, light absorption and their yield an experiment was conducted as a split plot based on randomized complete block design with three replications at the Research Farm of College of Agriculture, Isfahan University of Technology in 2012. The main plots included three nitrogen rates (0, 30 and 60 kg/ha of nitrogen) and subplots were different planting arrangement of linseed and berseem clover (monoculture of linseed, 70% linseed: 70% berseem clover, 70% linseed: 50% berseem clover, 50% linseed: 50% berseem clover, 50% linseed: 70% berseem clover, monoculture of berseem clover). The highest weed dry weight (286 g/m2) was obtained in monocultures of linseed when 60 kg/ha nitrogen was applied. The highest percentage of light absorption (85.3%) was achieved at different planting arrangements with application of 30 kg/ha nitrogen. The highest  seed yield of linseed (53.19 g/m2) and berseem clover (72.6 g/m2) were obtained in monocultures and 0 and 30 kg/ha nitrogen treatments, respectively. In general, linseed and berseem clover intercropping with application of 30 kg/ha nitrogen were proven beneficial as they led to the greater yield and successful weed control

Effects of Metribuzin Herbicide on Some Morpho-Physiological Characteristics of Two Echinacea Species

Echinacea is a perennial plant that is used for its phytotherapeutic potential. Echinacea crops are often affected by invasive weeds. One of the most effective strategies in weed control is the use of chemicals such as herbicides. However, herbicides also affect the physiological and morphological processes of Echinacea. For this reason, the aim of this study was to determine the effects of different dosages (0, 250, 500, 750, 1000, and 1250 g ha−1) of the postemergent herbicide metribuzin on some morphological and physiological characteristics of Echinacea purpurea and Echinacea angustifolia collected from different locations in Iran (E. purpurea from the Shiraz and Isfahan regions and E. angustifolia from the Ardestan and Kazerun regions). Application of metribuzin decreased leaf dry weight for both Echinacea species at high doses (750 and 1250 g ha−1). At high metribuzin dose (1250 g ha−1), E. purpurea Shiraz leaves showed an increase in MDA (malondialdehyde) up to 9.14, while in other species the MDA content was lower. Minimum and maximum fluorescence increased at both the registered dosage (500 g ha−1) and at high doses (750–1250 g ha−1) of metribuzin treatments in both species. The Fv/Fm (maximum quantum yield) value was reduced in herbicide treated species, compared to the control, starting at the 250 g ha−1 dose, and was lowest at 750 g ha−1 dose. The results of this study indicate that metribuzin has adverse effects on the physiology and morphology of Echinacea species at dosages above 500 g ha−1

Competitive ability effects of datura stramonium l. And xanthium strumarium l. on the development of maize (zea mays) seeds

The objective of this study was to explore the physical properties of maize seeds in competition with weeds. The basic and complex geometric characteristics of seeds from maize plants, competing with Datura stramonium L. (DS) or Xanthium strumarium (XS) at different weed densities, were studied. It was found that the basic and complex geometric characteristics of maize seeds, such as dimension, aspect ratio, equivalent diameter, sphericity, surface area and volume, were significantly affected by weed competition. The increase in weed density from 0 to 8 plants m2 resulted in an increase in the angle of repose from 27◦ to 29◦, while increasing weed density from 8 to 16 plants m2 caused a diminution of the angle of repose down to 28◦ . Increasing the density of XS and DS to 16 plants m2 caused a reduction in the maximum 1000 seed weight of maize by 40.3% and 37.4%, respectively. These weed side effects must be considered in the design of industrial equipment for seed cleaning, grading and separation. To our knowledge, this is the first study to consider the effects of weed competition on maize traits, which are important in industrial processing such as seed aeration, sifting and drying