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Purpose Persistence of herbicides in soil is a major concerning world issue due to their negative impacts on environment and human health. Laboratory and bioassay experiments were conducted to evaluate the effects of municipal waste compost (MC) and sheep manure (SM) on metribuzin degradation and phytotoxicity of this herbicide. Methods In degradation studies, soil samples were mixed separately with amendments at a rate of 2.5% (w/w) and metribuzin at a concentration of 5 mg kg −1 soil was used for fortification of selected samples. A liquid extraction method was chosen and final extracts were analyzed by HPLC. In bioassay study, the phytotoxic effects of different concentrations of metribuzin (0, 0.01, 0.05, 0.1, 0.2, 0.4, 0.8 and 1 mg kg −1 soil) on oilseed rape (Brassica napus L.) were evaluated. Results The results indicated 88.8% degradation of metribuzin in MC during 120-day period followed by SM recording 72.2%, compared to non-amended soil where 59.8% of metribuzin were removed. The half-life was 119.48 days in nonamended soil as compared to 87.72 and 103.43 days in MC and SM application, respectively. MC was the most efficient treatment to accelerate metribuzin dissipation from the soil. Bioassay results showed that metribuzin residues had a negative effect on root and shoot biomass of oilseed rape. However, the root parameter was more sensitive than the shoot. Conclusions It could be concluded that application of organic amendments to agricultural soils is an eco-friendly strategy to improve soil conditions and non-target crop protection as well as the removal of herbicide residues from soil environment.

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Flax-leaf alyssum (Alyssum linifolium Steph. ex. Willd.) is a winter growing annual weed species widely distributed in many semi-arid cropping regions of Iran, especially in the Khorasan Razavi and East Azerbaijan provinces. The germination of two populations (one each from Khorasan Razavi and East Azerbaijan) of this weed was evaluated under different experimental conditions. Seeds of A. linifolium germinated over a wide range of day/night temperature regimes, with the highest germination percentage observed with a regimen of 20°C/10°C. Light was not required for germination for either population, and >70% seeds germinated under all photoperiods tested. Germination was affected by pH levels; seeds germinated over the pH range 4–9 and germination was maximum at pH 7. For the Khorasan Razavi and East Azerbaijan populations, ≥50% of seeds germinated at a water potential of –0.69 and –0.78 MPa and salinity of 12.64 and 11.7 dS m–1 respectively. Maximum seedling emergence occurred when seeds were slightly covered with soil, but emergence decreased with increasing depth of soil cover, with no emergence at depths >3 cm. These results indicate that A. linifolium germinates in a wide range of climatic conditions and could invade into new regions. Burying the seeds through tillage may reduce their emergence.

Planta Daninha 2019; v37:e019182818 MIRZAEI, M. et al. The response of different weed species to glyphosate using ammonium sulfate and hard water ABSTRACT -Water hardness antagonism and the effect of ammonium sulphate (AMS) on efficacy of glyphosate have been well documented. However conflicting results between weed species were noted by the authors. Greenhouse experiments were conducted twice at the Ferdowsi University of Mashhad in a randomized complete block design with a factorial arrangement and three replications during 2014-2015. Four experiments were arranged separately on cypress (Kochia scoparia), redroot pigweed (Amaranthus retroflexus), little seed canary grass (Phalaris minor) and winter wild oat (Avena ludoviciana) using ammonium sulphate and deionizad water and in the presence of different salts, (i.e. NaHCO 3 , CaCO 3 , MgCl 2 and CaCl 2 at 500 ppm) against three doses of glyphosate (256.25, 512.5 and 1,025 g a.i. ha -1 ), with and without ammonium sulphate (AMS) as adjuvant (2% w/v). The results showed the application of AMS overcomes the inhibitory effects of salts in the spray solution in tested species. The degree of effectiveness in A. retroflexus was more than A. ludoviciana and P. minor. Glyphosate with AMS caused reduction in dry matter in grasses from 0.34 to 0.28 g, while glyphosate toxicity in A. retroflexus with AMS was 100 percent and all of the plants were destroyed (0.82 to 0 g). The application of AMS in overcoming the inhibitory effects of water hardness had no effect on K. scoparia control. However, Increasing AMS could overcome the inhibitory effects of hard water in the spray solution on glyphosate efficacy in A. retroflexus and K. scoparia, but it had no effect on tested grassy weeds. We may conclude that glyphosate work differently on weed species using AMS and hard water.

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