Allelopathic Potential of Green Manure Cover Crops on Germination and Early Seedling Development of Goose Grass [Eleusine indica (L.) Gaertn] and Blackjack (Bidens pilosa L.)

Petrus Jacobus Pieterse,Stanford Mabasa,Yong In Kuk,Joyful Tatenda Rugare

doi:10.1155/2021/6552928

Petrus Jacobus Pieterse, Stanford Mabasa + Show 2 more

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https://doi.org/10.1155/2021/6552928

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Abstract

Green manure cover crops (GMCCs), which are recommended for improving soil fertility, also have the potential of reducing weed populations in cropping systems through allelopathy. The objective of this study was to evaluate the effect of eight GMCCs on the germination and seedling development of two weeds of divergent morphology, namely, goose grass [Eleusine indica (L.) Gaertn] and blackjack (Bidens pilosa L.). Aqueous leaf, stem, and root extracts of hyacinth bean (Lablab purpureus L), red sunnhemp [Crotalaria ochroleuca (G.) Don], showy rattlebox (Crotalaria grahamiana Wight & Arn.), common bean (Phaseolus vulgaris L.), common rattlepod (Crotalaria spectabilis Roth.), radish (Raphanus sativus L.), tephrosia (Tephrosia vogelii L.), and black sunnhemp (Crotalaria juncea L.) at 0, 1.25, 2.5, 3.75, and 5% wv−1 were applied to weed seeds in Petri dishes to determine their effect on germination, radicle and plumule growth, and germination vigor index. The experimental design was 3(tissue types) ∗ 5(concentrations) treatment combinations replicated four times in a completely randomized design. In the pot study, 25 seeds of either goose grass or blackjack were planted separately in approximately 400 g of soil mixed with cover crop tissue powder at 1% concentration per pot. The experimental design was cover crop residues + control replicated four times in randomized complete blocks. There was a significant (p<0.05) extract ∗ concentration interaction on all germination parameters across all GMCCs. The different cover crop aqueous extracts differentially reduced all germination parameters of both weeds in the order leaf > stem > root extract except for radish root extracts being most inhibitory to all germination parameters of goose grass. The leaf, stem, and root soil-incorporated residues of GMCCs significantly (p<0.05) affected seedling emergence, dry weight, and vigor indices of both weeds. Based on the results of this study, it was concluded that the different GMCC tissues contain allelochemicals that inhibit the emergence of both monocotyledonous and dicotyledonous weeds.

Highlights

Green manure cover crops (GMCCs), which are recommended for improving soil fertility, have the potential of reducing weed populations in cropping systems through allelopathy. e objective of this study was to evaluate the effect of eight GMCCs on the germination and seedling development of two weeds of divergent morphology, namely, goose grass [Eleusine indica (L.) Gaertn] and blackjack (Bidens pilosa L.)
25 seeds of either goose grass or blackjack were planted separately in approximately 400 g of soil mixed with cover crop tissue powder at 1% concentration per pot. e experimental design was cover crop residues + control replicated four times in randomized complete blocks. ere was a significant (p < 0.05) extract ∗ concentration interaction on all germination parameters across all GMCCs. e different cover crop aqueous extracts differentially reduced all germination parameters of both weeds in the order leaf > stem > root extract except for radish root extracts being most inhibitory to all germination parameters of goose grass. e leaf, stem, and root soil-incorporated residues of GMCCs significantly (p < 0.05) affected seedling emergence, dry weight, and vigor indices of both weeds
The study indicated that all the GMCCs used in this study contain possible allelochemicals that could be responsible for the inhibition exhibited on goose grass and blackjack germination, as well as seedling growth

Summary

Introduction

Green manure cover crops (GMCCs), which are recommended for improving soil fertility, have the potential of reducing weed populations in cropping systems through allelopathy. e objective of this study was to evaluate the effect of eight GMCCs on the germination and seedling development of two weeds of divergent morphology, namely, goose grass [Eleusine indica (L.) Gaertn] and blackjack (Bidens pilosa L.). Most of the cover crops that are being promoted in the smallholder sector of Zimbabwe are fast growing and produce a lot of biomass, resulting in rapid canopy closure, which smothers weeds when they are used as live mulches [4] Their dead residues may be used as surface mulches or be incorporated into the soil. According to Ayeni [18], allelopathy can be exploited to achieve reduced application of synthetic herbicides, since most allelochemicals do not have residual effects and can, be exploited for early season weed control in arable fields without affecting successive crops in crop rotations. E fact that allelopathic effects from decomposing cover crop residues were reported to be more pronounced on small seeds and early emerging species compared to large-seeded crops, which offers an opportunity for exploiting them for selective weed control in arable crop production [20]. Aqueous extracts of velvet bean (Mucuna pruriens L) and Jack bean (Canavalia ensiformis L.) reduced weed germination and early seedling development [21, 22]

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