Chemical weed control in Spinach (Spiniacia oleracea)

Introduction Spinach (Spinacia oleracea) is an annual plant of family Chenopodiaceae. It is cultivated in temperate and cold regions in Khouzestan in autumn and winter. Weeds are the main problems that limit the production of vegetables. Competition ability of spinach against weeds is very low and weeds cause the loss of quality and quantity in this plant. Weeds reduce germination and establishment and growth of spinach. Weed management in spinach should be done at the beginning of the season. Hand weeding is the best way to control weeds spinach, although due to the high cost it is not cost effective, but is steel common in large areas. Weed control spinach, using chemical methods, the number of weeds are kept below the threshold of economic damage. Materials and Methods The experiment was conducted in a randomized complete block design with 15 treatments and three replications. Treatments included pre-plant application of EPTC at 5 and 6 lit ha-1, pre-plant application of Trifluralin at 2 lit ha-1, pre-plant and pre-emergence application of Pendimethalin at 3 lit ha-1, pre-emergence and post-emergence application of Meteribouzin at 300 g ha-1, pre-emergence and post-emergence application of Meteribouzin at 400 g ha-1, pre-emergence and post-emergence application of Imazethapyr at 0.7 lit ha-1, pre-emergence and post-emergence application of Imazethapyr at 1 lit ha-1, weedy and weed free checks. Each plot the size of 2.5 × 2 meters and 10 row cultivation with distances between rows of 15 cm and the distance between the plants 25 cm and the sowing depth was 3 cm. The herbicide treatments were applied to the back sprayer with Flat fan nozzle with volume of consumption of 240 lit ha-1 solution. The final harvest was about 50 days after emergence. Sampling of weeds 10 days before harvest was performed with using quadrate 0.5 ×0.5. Results Discussion Important broad-leaf and narrow leaf weeds observed in the field, included field bindweed (Convolvulus arvensis), Common lambsquarters (Chenopodium album), Malva (Malva spp.), Chamomile (Anthemis altissima), Purple nutsedge (Cyperus rotundus), canary grass (Phalaris minor), mouse barley (Hordeum morinum) and Japan brome (Bromus japonicus), respectively. The results of variance analysis showed that the effects of treatments on the number of broadleaf and weed narrow leaves were significant. Meteribouzin and Pendimethalin herbicides (pre-emergence), had better control on broadleaf weed than other herbicides. Low amounts of herbicides EPTC (5 lit ha-1) and imazethapyr (0.7 lit ha-1) were the least effective broadleaf weed control. Trifluralin herbicide reduced approximately 44% broadleaf weed density compared to control plots without control. The minimum weight of broadleaf weed at all doses studied allocated to herbicides Pendimethalin and Meteribouzin. Most of reducing the number narrow leaves was belonged to Meteribouzin and Pendimethalin herbicides as pre-emergence with doses of 300 g and 3 lit ha-1, respectively. The effect of treatments on petiole length, number of leaves per plant and the spinach fresh yield was significant in 1% probability level. Meteribouzin damage in spinach was 100%. It was reported that the half-life in soil herbicide Meteribouzin is about 30-60 days. It seems spinach a high sensitivity to the herbicide and relatively long survival in the soil that causing damage spinach was perfect, while maximum weed control amounts in all methods of used allocated to this herbicide. Number of leaves per plant trait was that less affected by weed interference. Both components of leaves per plant (r= 69.0**) and petiole length (r= 87.0**) showed significant positive correlation with the spinach fresh yield. The highest spinach yield was obtained in Trifluralin herbicide after treatments control. The difference between spinach yield in Trifluralin and control treatments was not significant. Conclusion: In general, the results showed that the broad and narrow leaf weeds were well controlled by different rates of pre-emergence and post-emergence application of meteribouzin, but this was followed by severe damage in spinach. Trifluralin had the lowest damage effect on spinach leaves. Pre-plant application of trifluralin at 2 lit ha-1 reduced approximately 45% of weed density and increased yield of spinach by 26.6% compared with control treatment. Therefore, this herbicide was recommended to use for weed control in spinach fields. According to the results it seems that the use of herbicide meteribouzin not advisable in spinach whereas causing damage, but due to weed well control is recommended increased resistance spinach to the herbicide through breeding programs. However, it should be noted that spinach leaves are consumed fresh, therefore, investigating the presence of herbicide residues in plant is necessary

The effect of growth regulators and irrigation on remobilization and grain filling of bread wheat in tropical climatic conditions

To study the remobilization rate affected by growth regulators in wheat a field experiment was carried out in the south of Iran over 2017-2019 with a split-split plot design and three iterations in completely randomized blocks. The main plots were two irrigation regimes (full irrigation and irrigation interruption at the grain-filling stage), two wheat cultivars (Chamran 2 and Durum Karkheh cv.s) were as sub plots, and four growth regulators (control (no growth regulator), salicylic acid, jasmonic acid, and cytokinin) placed in sub-sub plots. Results revealed the significant impact of the triple interaction on grain yield. The highest grain yield (4803 kg/Ha) was observed for Chamran 2 cv. treated with complete irrigation and salicylic acid. Although grain yield declined by 15.5% in the Karkheh cv. with irrigation interruption at the grain-filling stage and non-administration of growth regulators, treatment with salicylic acid managed to attenuate the adverse impact of drought stress in grain yield. The highest current photosynthesis and its contribution were observed in cultivars treated with complete irrigation. Moreover, irrigation regimen and growth regulators each had significant impacts on proline, catalase enzyme, and stomatal conductance. Overall, results suggested that using salicylic acid in Chamran 2 cv. would be advisable to increase growth and grain yield and reduce decline under stress

Relationships between Canopy Temperature, Leaf Chlorophyll Content and Grain Yield in Wheat Genotypes under Different Nitrogen Levels and Post-Anthesis Heat Stress Conditions

Abstract\ud In order to study the canopy, spike and flag leaf temperature in wheat genotypes under optimum and post-anthesis heat stress conditions and canopy relationships with some morphological and physiological characters, two separate field experiments were conducted in delayed and optimum sowing dates in Ahvaz, Iran in 2007-2008. The experimental site had a moderate winter and dry, hot summer. Plants with delayed sowing date experienced heat stress post-anthesis. Each split-polt experiment had a randomized complete block design with three replicates. The N application rates were (50, 100, and 150 KgNha-1) assigned in the main-plots. Sub-plots consisted of six bread and durum wheat genotypes. Temperature of canopy, spikes and flag leaf were measured in two growth stages (anthesis and milk stage) using a hand-held infrared thermometer. Results indicated that, organs temperature was affected by genotypeenvironment. Although, organs temperature increased as the N rate decreased, the effect of N treatments on organs temperature was not significant. In post-anthesis heat stress conditions, the genotypes that had higher flag leaf and canopy temperature due to higher growth stage duration (such as Star and D-84-5), lower ability in leaf rolling (such as Showa and D-84-5) and higher leaf width (such as Star and D-84-5), had higher chlorophyll reduction under post-anthesis heat stress conditions.\ud \ud Keywords: Wheat, Post-anthesis heat stress, Canopy temperature, Chlorophyll conten