Allelopathic Effects of Annual Weed Residues on Growth and Nutrient Uptake of Corn and Soybeans1

Abstract

AbstractAnnual weeds have shown allelopathic potential in recent years. Few studies clearly compare effects of weed residues on growth inhibition and nutrient uptake in corn (Zea maysL.) and soybeans [Glycine max(L.) Merr.]. Therefore, the residues (aboveground biomass) of common lambsquarters (Chenopodium albumL.), redroot pigweed (Amaranthus retroflexusL.), common ragweed (Ambrosia artemisifoliaL.), velvetleaf (Abutilon theophrastiMedic.), and yellow foxtail [Setaria glauca(L.) Beauv.] were evaluated for their allelopathic effects on growth and uptake of N, P, and K in corn and soybeans in controlled environments. Weed residues in silica sand produced more inhibitory effects than the mixture of soil (Typic Agriudoll) and sand. The growth inhibition was more (8 to 14%) when the residues were incorporated in all soils than when they were surface applied. All residues except common ragweed reduced corn (6 to 20%) and soybean (2 to 20%) dry matter production. The inhibition or stimulation of N, P, and K uptake in both crops was not consistent and depended on the residue source, residue placement, or soil texture. Addition of supplemental N and P to various residues provided no alleviating effect on crop growth. Addition of P markedly enhanced P uptake without affecting total dry weights of both test species when compared to the controls. Yellow foxtail and common ragweed residues increased K uptake (21 to 48%) in corn but not in soybeans. The weed residues demonstrated an allelopathic inhibition of growth independent of N and P nutrition, and suggest that the inhibitory effects are not related to nutrient uptake.