Pendimethalin

Abstract: The transformations of eight herbicides (atrazine, simazine, terbutryn, pendimethalin, carbetamide, 2,4-D, metsulfuron-methyl and dimefuron) in soil after compost addition were monitored during long-term laboratory incubations. The herbicides were applied to soil, compost and soil-compost mixtures. Herbicide sorption, their kinetics of mineralisation and the extractability of residues were compared in the different treatments. Compost addition to soil generally decreased herbicide mineralisation and favoured the stabilisation of herbicide residues. A fraction of the stabilised residues remained extractable and potentially available. However, most of them were unextractable and formed bound residues. Sorption could be at the origin of a kinetically limited biodegradation, mainly for the most highly-sorbed herbicides (atrazine, simazine, terbutryn, pendimethalin and dimefuron). Compost addition had little effects on the less sorbed herbicides (carbetamide, 2,4-D and metsulfuron- methyl). © 1997 SCI.

Abstract: Rice (Oryza sativa), the staple food of more than half of the population of the world, is an important target to provide food security and livelihoods for millions. Direct seeding of rice (DSR) refers to the process of establishing the crop from seeds sown in the field rather than by transplanting seedling from the nursery. Before the advent of Green revolution and adoption of irrigation, rainfed rice was often broadcasted into moist soil and yields were low, variable and highly prone to weed competition. Weed spectrum and degree of infestation in rice field are often determined by rice ecosystems and establishment methods. Research evidences at different places has shown around 20–100% losses due to weeds such as Echinochloa spp., Leptochloa spp., Cyanotis spp., Commelina sp., Digitaria spp. and Alternanthera sp in DSR. Integrated weed management approach based on the critical period of crop weed competition, involving different direct and indirect control measures, has been developed and widely adopted by farmers to overcome weed problem in DSR in a sustainable way. Stale seed bed combined with herbicide (paraquat/glyphosate) and zero till results in better control. About 53% lower density was recorded due to stale seed bed. Brown manuring of Sesbania reduces weed population by 50%. Mulches, crop rotation and rice cultivars like ‘Narender 359’ and ‘Sarjoo 52’ were found better for Indo-Gangetic plains. Application of penoxsulam 25 g/ha as broad-spectrum, azimsulfuron + metsulfuron-methyl for Cyperus spp., pendimethalin at 1.25 kg/ha for Echinochloa spp. were found suitable for chemical weed management.Weed-competitive and allelopathic rice varieties, seed priming for increased weed competitiveness, higher seeding density should be considered as a management strategy.

Abstract: Weed management systems were compared in bromoxynil-resistant, glyphosate-resistant, and nontransgenic cotton. A standard system of pendimethalin preplant incorporated (PPI), fluome- turon preemergence (PRE), fluometuron plus MSMA early postemergence-directed (POST-DIR), and cyanazine plus MSMA late POST-DIR in combination with cultivation controlled broadleaf signal- grass, large crabgrass, common lambsquarters, jimsonweed, pitted morningglory, prickly sida, sick- lepod, and smooth pigweed 98 to 100% late season. Weed control, cotton yield, and net returns were similar when pyrithiobac or bromoxynil plus MSMA postemergence (POST) replaced fluometuron plus MSMA POST-DIR. Fluometuron PRE had little to no effect in bromoxynil systems. Glyphosate POST to three- to four-leaf-stage cotton followed by cyanazine plus MSMA late POST-DIR and cultivation controlled weeds 96 to 100%. Glyphosate POST followed by glyphosate POST-DIR and cultivation controlled pitted morningglory and large crabgrass 89 to 90% and other species at least 94%. Yields and net returns at one location were similar for glyphosate applied twice or glyphosate POST followed by cyanazine plus MSMA POST-DIR and the standard system. Pendimethalin plus fluometuron in glyphosate systems did not increase yield or net returns. At a location severely infested with large crabgrass, pendimethalin plus fluometuron in glyphosate systems increased yield 37 to 44% and net returns 85 to 108%, respectively, when glyphosate was applied to cotton at the three- to four-leaf stage, but not if glyphosate was applied to cotton at the one-leaf stage. Yield and net returns were similar when bromoxynil-resistant, glyphosate-resistant, and nontransgenic cotton were treated using the standard system. Nomenclature: Bromoxynil, 3,5-dibromo-4-hydroxybenzonitrile; cyanazine, 2-((4-chloro-6-(ethyl- amino)- 1 ,3,5-triazin-2-yl)amino)-2-methylpropanenitrile; fluometuron, N,N-dimethyl-N'-(3-(trifluo- romethyl)phenyl)urea; glyphosate, N-(phosphonomethyl)glycine; MSMA, monosodium salt of meth- ylarsonic acid; pendimethalin, N-(l-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine; pyrithiobac, 2-chloro-6-((4,6-dimethoxy-2-pyrimidinyl)thio)benzoic acid; broadleaf signalgrass, Brachiaria platy- phylla (Griseb.) Nash #a BRAPP; common lambsquarters, Chenopodium album L. # CHEAL; jimson- weed, Datura stramonium L. # DATST; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; sicklepod, Senna obtusifolia (L.) Irwin and Barneby # CASOB; smooth pigweed, Amaranthus hybridus L. # AMACH; cotton, Gossypium hirsutum L. 'Deltapine 51,' 'Paymaster 1220RR,' 'Stoneville BXN 47.'