Competitiveness of Three Leguminous Cover Crops with Yellow Nutsedge (Cyperus esculentus) and Smooth Pigweed (Amaranthus hybridus)

Abstract

Greenhouse replacement-series experiments were conducted to evaluate the competitiveness of cowpea, sunn hemp, and velvetbean when grown in combination with yellow nutsedge and smooth pigweed. The effect of the cover crop species on yellow nutsedge tuber production was also evaluated. Cowpea and velvetbean were equally competitive with yellow nutsedge, but sunn hemp was less competitive. Although sunn hemp height was double that of cowpea or velvetbean, photosynthetically active radiation penetrating to the soil surface was twofold to eightfold greater than with the other two species. Leaf area per plant with sunn hemp monocultures were only 63 to 70% of cowpea and 37 to 41% of velvetbean. Increasing the proportion of cover crops in crop : weed mixtures did not significantly affect nutsedge tuber number per plant or tuber weight per plant. Cowpea was more competitive than smooth pigweed, whereas both sunn hemp and velvetbean were less competitive than smooth pigweed. The utility and efficacy of leguminous cover crop species for nutsedge and smooth pigweed suppression do not appear to be due to inherent competitiveness. Until cultivars that are more competitive become available, cultural measures should be employed that enhance cover crop modification of soil environmental conditions to minimize weed seed germination and vegetative propagule sprouting.

Utilization of Sunn Hemp for Cover Crops and Weed Control in Temperate Climates

“…This research also found that sunn hemp could also tolerate 2,4-DB as a postemergent application (Mosjidis and Wehtje 2011). Imazethapyr was also determined to be safe for use in sunn hemp and effective against yellow nutsedge (Cyperus esculentus L.), which is not well suppressed by sunn hemp (Collins et al 2007;Mosjidis and Wehtje 2011). With advancements in sunn hemp breeding and increased utilization of this species in a broader geographical range, continued research efforts to determine additional herbicide programs will be critical for successful production in the future.…”

“…), and morningglory (Ipomoeae spp.) (Collins et al 2007;Teasdale 1988;White et al 1989). Either as a ground cover or through allelopathy, as noted in subterranean clover (Trifolium subterraneum L.), weed control achieved through legume cover crops has the potential to reduce early-season herbicide use in agricultural systems (Hartwig and Ammon 2002;Leather 1983;Mosjidis and Wehtje 2011).…”

“…It has been noted by many researchers that C. juncea can suppress populations of pests such as nematodes and vigorous weed species (Collins et al 2007;Fassuliotis and Skucas 1969;McSorley et al 1994;Taylor 1985;Wang et al 2001). Much of the pest control potential of sunn hemp has focused primarily on nematode control of such species as Meloidogyne spp., Rotylenchulus reniformis, Radopholus similis, and Heterodera glycines (Birchfield and Bristline 1956;Desaeger and Rao 2000;Good et al 1965;Marla et al 2008;Robinson et al 1998;Wang et al 2004).…”

“…In fact, Mosjidis and Wehtje (2011) demonstrated that there was a progressive reduction in weed biomass as a sunn hemp stand increased up to 100 plants/m 2 . Furthermore, recent research has suggested allelopathic compounds released from sunn hemp also cause weed suppression (Adler and Chase 2007;Collins et al 2007;Leather and Forrence 1990;Price et al 2008). More research is necessary to determine the extent of allelochemical functions in sunn hemp.…”

“…), morningglory (Ipomoea spp. ), and bermudagrass (Cynodon dactylon), are capable of thriving in a sunn hemp stand (Chaudhury et al 2007;Collins et al 2007;McKee et al 1946). It is expected that, as sunn hemp utilization for cover crops and weed control grows, research efforts to fully understand weed suppression by C. juncea will continue.…”