Essential oils of eucalyptus leaves and clove buds were isolated and tested for their bioherbicidal potential on different annual weed species. Gas Chromatography-Mass Spectrophotometry analysis (GC-MS) identified thirteen compounds representing around 87.11% of the total isolated eucalyptus oil. The main constituent was 1,8-cineole, which accounted for 68.15% of the total identified compounds. As for clove oil, eleven compounds were identified, representing 90.03% of the total compounds. Eugenol was the dominant compound and accounted for 73.89%. The bioherbicidal efficacy of the two oils and their combinations by three concentrations (2.5, 5, and 10%) were tested on four weedy species, namely Chenopodium album, Raphanus raphanistrum, Melilotus indicus, and Sisymbrium irio. The isolated oils significantly affected the dry weight and inhibited the seedling growth of the four weedy species. Using the two essential oils, individually or within their combinations, showed the highest bioherbicidal efficacy against the targeted weeds in comparison with the synthetic herbicide. In addition, utilization of the two essential oils as natural bioherbicides caused an electrolyte leakage as a result of membrane disruption and loss of integrity of weed seedling tissues.  The results showed the possibility of using eucalyptus and clove essential oils individually or in combination as a desirable alternative to synthetic herbicides for sustainable weed management.

No abstract

Allelopathic effects of the sunflower verities Helianthus annuus residues were evaluated on some soil properties and their potential against growth parameters of the proposed successive crops Wheat Triticum aestivumL., Broad Bean Vicia fabe L. and Flax Linum UstatissmimL. Sunflower plants were chopped and incorporated with field soil after getting seed, and then successive crops were cultivated. The sunflower residues have reinforced the soil with the macronutrients considered essential for the germination of any crop. The soil organic matter content and the percentage of organic carbon in the ground were increased. Significant suppression of broad bean and flax crops was observed, while the sunflower residues did not affect wheat growth. The results obtained showed that broad bean and flax crops are not recommended to grow after the sunflower crop to avoid losses due to the negative allelopathic potential of these crops. Sunflower residue incorporation may provide multidimensional benefits for better weed control, enhanced soil health, and higher seed yield of wheat. Keywords: Allelopathic effect; Sunflower residues; Succssesive crops. Crop injury symptoms

Two experiments were carried out under greenhouse conditions at the College of Agriculture - University of Anbar for the spring season 2018, using plastic seedlings containers on sandy soil to study the effect of 6 Benzylaminopurine growth regulator and used at a concentration of 250 mg l-1 on seedlings performance of six varieties of wheat, namely; IBA 99, Bohooth 10, Bohooth 22, Abu Ghraib, Bohooth 158 and Ezz under four levels of saline irrigation water 3.00, 4.50, 6.00 and 7.50 dS m-1 in addition to the comparison treatment distilled water 0 dS m-1. The results of the experiment showed that the low concentrations of salts in the nutrient medium activate the radicle growth in the wheat plant. The seeds of wheat germinated in the irrigated medium were outperformed with salty water 3.00 dS m-1 with the highest averages of the studied traits. Ezz cultivar was the most tolerant category of salinity of irrigation water compared to other cultivars. The results of the experiment also showed that soaking the seeds of wheat with a growth regulator solution 6-Benzylaminopurine contributed to reducing the negative effect resulting from the increase in saline stress in the germination medium which improved the seed germination and seed growth characteristics under saline stress. The research recommends using the Ezz variety in the event of high salinity in irrigation water, as well as treating the seeds with the 6-BAP growth regulator to increase the tolerance of seeds to the stress of irrigation water salinity.

Weed control through the use of conventional chemical compounds presented by synthetic herbicides is a widely used and successful method to control weed by reducing the negative impact of weed and increase agricultural production gradually. However, although the losses in agricultural production arising from weed competition are decreased through the use of synthetic herbicides, the negative impacts of these compounds on the environment and human health have raised awareness and created grave concern of a number of parties to safeguard the environment and humans. The adverse effect of synthetic herbicides can still occur even if such herbicides are applied at the recommended rates. Control weed naturally presented by allelochemical compounds provides an attractive, alternative and safe way to control weed synthetic herbicides. Previous works indicated that terpenoids as the most important group of allelochemicals have shown to exhibit a good phytotoxic effect against a wide range of weed species by suppressing germination and reducing growth. This review was a highlight to detect the desirable phytotoxic effects of some terpenoid compounds as a major content in essential oils on various weed species and the possible uses as natural weed killers.