Competition and Allelopathy Between Soybeans and Weeds¹

Abstract

This research was initiated to determine how soybean [Glycine max (L.) Merr.] cultivars differ in competitive ability and also whether allelopathy functions to inhibit surrounding weed growth. Initially 280 soybean cultivars were screened in the field for competitive ability based on emergence, seedling vigor, quickness of canopy closure, and ability to inhibit growth of velvetleaf (Abutilon theophrasti Medic.) and foxtail millet [Setaria italica (L.) Beauv.]. Experiments were conducted at Lincoln, Nebr. on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls) during 1981 and 1982. Soybean cultivars of later maturity tended to compete more effectively with weeds. Competitive cultivars emerged quickly, rapidly formed a canopy, and were able to slow the growth of competing weed species. Twenty soybean cultivars of varying competitive ability were selected and grown in the greenhouse during 1981 and 1982 to determine the importance of allelopathy in competing with weeds. Exudates from roots of soybean cultivars grown in sand reduced the dry weight of 4‐week‐old velvetleaf plants an average of 15%, but foxtail millet was not inhibited. Incorporation of 1% ground soybean dry matter into Sharpsburg silty clay loam inhibited germination and dry weight of greenhouse grown velvetleaf an average of 46% each. Foxtail millet germination and dry weights were reduced an average of 82 and 65%, respectively. Undiluted soybean plant extracts of all cultivars tested slowed the germination and dry weight accumulation of 6‐day‐old velvetleaf and foxtail millet, but dilution of the extracts caused quite variable responses. Osmotic potential of the extract solution appeared to be the main cause of inhibition, however, extracts of some cultivars, diluted to decrease the osmotic potential, still inhibited growth. Allelopathy appears to be one mechanism for competition among soybeans and weeds. Soybean cultivars possessing the ability to chemically inhibit competing weed growth would be a great benefit to the soybean producer.

Allelopathic effects of barley extracts on germination and seedlings growth of bread and durum wheats

“…1 vs. 2). This could be the case among varieties within the same species as reported by Kimber [7] and Rose et al [13]. In addition, the allelopathic potential of barley was unstable over the life cycle of the barley plant.…”

“…Bioassays of germination, radicle growth and coleoptile growth are used to test the allelopathic potential of a crop species [7,13,16]. The allelopathic potential can be observed in the form of autotoxicity as in the case of alfalfa (Medicago sativa L.) [5,6] or heterotoxicity as in the case of tall fescue (Festuca arundinacea L.) [10].…”

Otimização Da Eficiência Nutricional Na Produção Das Culturas

“…Rice (1974) define alelopatia como o efeito nocivo de uma planta sobre ela mesma ou sobre outra planta, através da produção de substâncias químicas. A liberação de substância química na rizoosfera é feita, geralmente, através de excreções das raízes ou através da decomposição dos restos culturais (Rose et al, 1984). Os restos culturais incorporados ao solo podem produzir aleloquímicos que inibem a germinação da semente e o crescimento inicial das plantas (Martin et al, 1990).…”

“…Em adição ao efeito negativo dos aleloquímicos no crescimento da planta, eles podem inibir a absorção de nutrientes pela cultura afetada (Bhowmik & Doll, 1984). Ruschel & Paula (1994) observaram alelopatia e autotoxicidade em arroz de sequeiro em solo de cerrado. Os mesmos autores relatam que extrato de macerado de raiz de arroz de sequeiro, verdes ou secos, inibiram a germinação.…”

Avaliação do potencial alelopático de genótipos de aveia no início do ciclo

“…Este estudo baseouse na exsudação de escopoletina pelas radículas de plântulas de aveia, substância conhecida como inibidora do crescimento vegetal, e levou à seleção de genótipos que mostravam maior capacidade de produção desse inibidor. Outros trabalhos, apresentando objetivos semelhantes, foram realizados com outras espécies (Putnam & Duke, 1974;Leather, 1983;Rose et al, 1984; Alsaadawi, 1988;James et al, 1988; Dilday et al, 1992).…”