title: Seed germination ecology of Echinochloa glabrescens and its implication for management in rice (Oryza sativa L.).
abstract: Echinochloa glabrescens is a C4 grass weed that is very competitive with rice when left uncontrolled. The competitive ability of weeds is intensified in direct-seeded rice production systems. A better understanding is needed of factors affecting weed seed germination, which can be used as a component of integrated weed management in direct-seeded rice. This study was conducted to determine the effects of temperature, light, salt and osmotic stress, burial depth, crop residue, time and depth of flooding, and herbicide application on the emergence, survival, and growth of two populations [Nueva Ecija (NE) and Los Baños (IR)] of E. glabrescens. Seeds from both populations germinated at all temperatures. The NE population had a higher germination rate (88%) from light stimulation than did the IR population (34%). The salt concentration and osmotic potential required to inhibit 50% of germination were 313 mM and -0.24 MPa, respectively, for the NE population and 254 mM and -0.33 MPa, respectively, for the IR population. Emergence in the NE population was totally inhibited at 4-cm burial depth in the soil, whereas that of the IR population was inhibited at 8 cm. Compared with zero residue, the addition of 5 t ha(-1) of rice residue reduced emergence in the NE and IR populations by 38% and 9%, respectively. Early flooding (within 2 days after sowing) at 2-cm depth reduced shoot growth by 50% compared with non-flooded conditions. Pretilachlor applied at 0.075 kg ai ha(-1) followed by shallow flooding (2-cm depth) reduced seedling emergence by 94-96% compared with the nontreated flooded treatment. Application of postemergence herbicides at 4-leaf stage provided 85-100% control in both populations. Results suggest that integration of different strategies may enable sustainable management of this weed and of weeds with similar germination responses.
authors.affiliation: Crop and Environmental Sciences Division, International Rice Research Institute, Los Baños, Laguna, Philippines.
authors.forename: Jhoana L
authors.initials: JL
authors.lastname: Opeña
authors.affiliation: Crop and Environmental Sciences Division, International Rice Research Institute, Los Baños, Laguna, Philippines.
authors.forename: Bhagirath S
authors.initials: BS
authors.lastname: Chauhan
authors.affiliation: University of the Philippines Los Baños, Los Baños, Laguna, Philippines.
authors.forename: Aurora M
authors.initials: AM
authors.lastname: Baltazar
mesh_terms: D001565:Benzoates / Q000494:pharmacology; D031747:Echinochloa / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D018525:Germination; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006540:Herbicides / Q000494:pharmacology; D008027:Light; D012275:Oryza / Q000502:physiology*; D009997:Osmotic Pressure; D018517:Plant Roots / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D057685:Plant Weeds / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D011743:Pyrimidines / Q000494:pharmacology; D055049:Salt Tolerance; D036226:Seedlings / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D012639:Seeds / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D013312:Stress, Physiological; D013449:Sulfonamides / Q000494:pharmacology; D013453:Sulfonylurea Compounds / Q000494:pharmacology; D014529:Uridine / Q000031:analogs & derivatives / Q000494:pharmacology; D058728:Weed Control; D000097797:Glyphosate
chemical_list: D001565:Benzoates; D005998:Glycine; D006540:Herbicides; D011743:Pyrimidines; D013449:Sulfonamides; D013453:Sulfonylurea Compounds; D014529:Uridine; D000097797:Glyphosate; C544125:1-(4,6-dimethoxypyrimidin-2-yl)-3-(2-ethoxyphenoxysulfonyl)urea; C504402:penoxsulam; C549011:bispyribac