Weed Control in Soybean (Glycine max) with Green Manure Crops

Abstract

Greenhouse and field experiments were initiated to evaluate rapeseed and mustard species as green manure crops for weed suppression. Under greenhouse conditions incorporating 20 g fresh wt leaf and stem tissue of rapeseed, two white mustards, and brown mustard into 450 g Sharpsburg, silty clay loam soil resulted in significant reductions in weed emergence, biomass, and height. Kochia, shepherd's-purse, and green foxtail emergences were reduced by all green manure crops. Redroot pigweed emergence was reduced by all green manure crops except brown mustard, and velvetleaf emergence was reduced by white mustards only. Kochia and shepherd's-purse fresh weights were reduced by all green manure crops, while redroot pigweed and velvetleaf fresh weights were reduced by brown mustard and white mustard var. Salvo. Green foxtail fresh weight was reduced by all green manure crops except rapeseed. With the exception of shepherd's-purse, no relationship between glucosinolate content of the incorporated green manure and suppression of weed growth was found. Under field conditions, early spring-planted green manure crops reduced early season weed biomass in soybean at one of the two locations. Mustard species as green manure crops reduced total weed biomass in soybean by 40% 4 weeks after emergence (WAE) and 49% 6 WAE. Soybean biomass and yield were sometimes reduced by the incorporation of green manure crops in treatments containing weeds; however, hand-weeded plots with green manure treatments yielded similar to hand-weeded plots without green manure.

The biology of Canadian weeds. 138. Kochia scoparia (L.) Schrad.

“…In greenhouse experiments, white mustard (Sinapis alba L.) and rapeseed (Brassica napus) residue reduced kochia emergence by 54 and 25%, respectively, and seedling shoot dry weight by about 30 and 15%, respectively; glucosinolates were suggested as the major chemical component responsible for allelopathic activity (Al-Khatib et al 1997). In other greenhouse experiments, shoot residue of various Brassica crop species (rapeseed and mustard) reduced kochia emergence by a maximum of 50% and biomass by a maximum of 70% (Krishnan et al 1998). In field studies, yellow sweetclover [Melilotus officinalis (L.) Lam.]…”

The biology of Canadian weeds. 130. Amaranthus retroflexus L., A. powellii S. Watson and A. hybridus L.

“…Emergence and biomass of A. retroflexus in Nebraska were reduced by spring-planted green manure crops (Brassica spp.) incorporated just prior to soybean planting (Krishnan et al 1998; reviewed by AlKhatib and Boydston 1999). Lehman and Blum (1997) in North Carolina found that cover crop residues inhibited A. retroflexus emergence prior to desiccation with glyphosate, but were no longer inhibitory one month after desiccation.…”

Potencial alelopático de extratos aquosos de genótipos de canola sobre Bidens pilosa

“…Castro et al (1983) constataram que extratos de Brassica napus inibiram a germinação e o crescimento da radí-cula de alface e tomateiro e relataram também que a canola afeta o desenvolvimento de outras espécies cultivadas. A incorporação no solo de plantas do gênero Brassica como adubação verde reduziu a emergência e biomassa de plantas daninhas e soja, além de diminuir o rendimento de grãos da cultura (Krishnan et al, 1998). Rizzardi et al (2008) observaram efeito inibitório de extratos de folhas, raízes e caule de canola na velocidade de emergência e na porcentagem de germinação de picão-preto e soja.…”