Effects of different nitrogen levels on phytotoxicity of some allelopathic crops

Abstract

Intensive usage of herbicides can result in the serious negative impacts on environment. Allelopathy by reducing seed germination and early seedling growth can play a fundamental role in suppressing weeds in crop fields. The effectiveness of allelochemicals is governed by different factors such as soil nutrient status, pH and microorganisms. Outdoor pot experiments were conducted at the Faculty of Agriculture and Natural Resources of Razi University, Kermanshah, Iran, in 2013, to evaluate the effects of different levels of N fertilizer (0, 150, 300 kg ha -1 ) on the suppressing effects of alfalfa (Medicago sativa L.), sorghum (Sorghum bicolor L.), and tobacco (Nicotiana tabacum L.) plant materials on emergence and growth parameters of some weed species including Johnson grass (Sorghum halepense (L.) Pers.), barnyard grass (Echinochloa crus-galli (L.) Beauv.) and redroot pigweed (Amaranthus retroflexus L.). Results indicated that adding plant materials of tobacco, sorghum, and alfalfa substantially reduced seed germination and early growth of the tested weeds. However, the weed species responded differently to the presence of the allelopathic plant materials. The use of N fertilizer had significant effects on the inhibitory potentials of the allelopathic plants. However, we didn't find consistent trends regarding the responses of the allelopathic crops to elevated N fertilizer levels in related to the traits under study.Key words: alfalfa, allelopathy, nitrogen, sorghum, tobacco, weeds IZVLEČEK UČINKI RAZLIČNIH ODMERKOV DUŠIKA NA FITOTOKSIČNOST NEKATERIH ALELOPATIČNIH POLJŠČINIntenzivna raba herbicidov ima lahko resne negativne vplive na okolje. Z zmanjševanjem kalitve in začetne rasti lahko igra alelopatija pomembno vlogo pri zatiranju plevelov. Na učinkovitost alelokemikalij vplivajo številni dejavniki kot so količina hranil v tleh, pH in mikroorganizmi. Na Faculty of Agriculture and Natural Resources of Razi University, Kermanshah, Iran, je bil v letu 2013 izveden lončni poskus na prostem, z namenom ovrednotenja različnih odmerkov N gnojil (0, 150, 300 kg ha -1 ) na zaviralni učinek lucerne (Medicago sativa L.), navadnega sirka (Sorghum bicolor L.), in navadnega tobaka (Nicotiana tabacum L.). Po dodatku zmletih nadzemnih delov teh poljščin so spremljali vznik in rastne parameter treh plevelov, divjega sirka (Sorghum halepense (L.) Pers.), navadne kostrebe (Echinochloa crusgalli (L.) Beauv.) in navadnega ščira (Amaranthus retroflexus L.). Rezultati so pokazali, da je dodatek navadnega tobaka, navadnega sirka in lucerne znatno zmanšal kalitev in zgodnjo rast testiranih treh plevelov. Testirani pleveli so se različno odzvali na dodatke alelopatskih rastlinskih ostankov. Uporaba dušičnih gnojil je imela značilen učinek na inhibitorni potencial alelopatskih rastlin, vendar niso uspeli ugotoviti konsistentnega trenda med odzivi plevelov na dodatke alelopatskih rastlin in povečanimi odmerki dušičnih gnojil.

Study of the allelopathic effects of Medicago sativa on the germination characteristics of Secale montanum

“…An essential way of increasing shoot dry weight is the absorption of nutrients such as nitrogen. Reportedly, the phenyl in allelochemicals decreases the absorption of nutrients, generating a decreased shoot growth, and eventually a decreased shoot dry weight (Norouzi et al, 2016).…”