Wheat cover crops

Study 1. Wheat ( McNair 1813 ) was planted at the Central Crops Research Station near Clayton (Lynchburg sandy loam) and the Tidewater Research Station near Plymouth (Bayboro loam), North Carolina, at a rate of 101 kg/ha in October of 1980. The following spring or early summer, plots were set up in which a green wheat cover crop or wheat straw and stubble remaining after wheat harvest was (1) left... 

Desiccated rye and wheat cover crops were the most consistent in the inhibition of weed seedling emergence. 

Con 2 Phenolic acids were rapidly lost from surface wheat cover crop residues after desiccation and thus release of phenolic acids to soils was limited in time, roughly 3 or 4 weeks, for the cover crop residues tested. The rate of and time for depletion of phenolic acids from surface residues was determined largely by the extent and frequency of rainfall/irrigation events. For most of the growing season phenolic acids in soil extracts were, in fact, largely derived from older decomposed... 

Study 2. The effects of wheat, oats, barley and rye mulches on three broadleaf weed species and crabgrass (Digitaria spp.) are shown in Table VI. Weed control data for the corn test at Kinston are not presented because of poor cover crop kill by the paraquat treatment. 

Inhibitive effects are especially influenced by amount of cover crop biomass and soil management. Weed dry matter was reduced when rye residues were greater than 3.7 Mg ha-1 (Crutchfield et al. 1985), and when wheat residues were greater than Mg ha-1 (De Almeida 1985). Fisk et al. (2001) reported that burr medic (Medicago polymorpha L.) and barrel medic (M. truncatula Gaertn.) reduced by 70% weed dry weights while weed density was not affected if were no-till seeded as winter-killed cover crops into winter wheat (Triticum aestivum L.) stubble. 

Rasmussen IA (2004) The effect of sowing date, stale seedbed, row width and mechanical control on weeds and yields of organic winter wheat. Weed Res 44 12-20 Reddy KC (2001) Effects of cereal and legume cover crop residues on weeds yield, and net return in soybean (Glycine max),. Weed Tech 15 660-668 Reynolds LB, Potter JW, Ball-Coelho BR (2000) Crop rotation with Tagetes sp. is an alternative to chemical fumigation for control of root-lesion nematodes. Agron J 92 957-966 Rice EL (1984) Allelopathy. Academic, New York, p 317... 

The non-legumes used as green-manure cover crops are mostly grasses. They are grown because they are economical, easily established and can quickly produce large amounts of organic material. Examples include aimual rye, oats, wheat and millet. 

Studies were conducted by Burgos and Talbert (1996) at the Main Agricultural Experiment Station in Fayetteville and the Vegetable Substation in Kibler, Arkansas, in 1992 and 1993 on the same plots to evaluate weed suppression by winter cover crops alone or in combination with reduced herbicide rates in no-till sweet com and to evaluate cover crop effects on growth and yield of sweet com. Plots seeded to rye plus hairy vetch, rye, or wheat had at least 50% fewer early season weeds than hairy vetch alone or no cover crop. None of the cover crops reduced population of yellow... 

Abstract This chapter describes the underlying criteria and assumption in the development and execution of field and associated laboratory bioassays. It provides details and commentary regarding the materials and methods used. More specifically, describes how glyphosate-desiccated wheat and other cover crops (crimson clover, subterranean clover, and rye) in no-till systems can directly and indirectly influence morningglory, pigweed, and prickly sida seedling emergence, with emphasis on the role of phenolic acids in plant residues and soil. 

Wheat Triticum aestivum L. Coker 983 or Southern States 555 ), rye Secale cereale L. Abruzzi ), crimson clover (Trifolium incamatum L. Tibbee ), and subterranean clover (71 subterranean L. Mount Barker ) were used as cover crops. These cover crops were chosen because of their different physical and chemical characteristics (Fig. 3.2). Crimson and subterranean clovers are composed primarily... 

Fig. 3.2 Cover crops before they were desiccated with glyphosate (a) crimson clover (front right), subterranean clover (front left), wheat (back right) and rye (back left-, Blum et al. 1997). Wheat plots after they were desiccated with glyphosate (b) shoots cut and uncut and reference plot in the right-hand comer (Blum et al. 2002)...

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