[Descuraina spp en alfalfa establecida y su control mecánico]

Tansy mustard and flixweect (Descurainia spp) are annual weeds that emerge late in winter or early spring before alfalfa breaks dormancy. They are competitive even in adequate well-established alfalfa stands. The effects of Descurainia on established alfalfa quality and quantity and mechanical methods of control were studied. Effects of control methods on alfalfa and weeds were studied by comparing tillage with a disk, cultivator, harrow or rotary-hoe, to paraquat or hexazinone. Treatments were applied in late winter before alfalfa broke dormancy at Rocky Ford and in early spring at Fort Collins when alfalfa was about 15 cm tall. Control of Descurainia spp increased the first cutting alfalfa yield about 18% at Rocky Ford. Density of tansy mustard was 159 plants/m. which yielded 1.47 ton/ha, and increased the seed bank by over 39,000 seeds/m. No tansy mustard was present a the second harvest. Disking, cultivation, or post emergence herbicides decreased Descurainia spp over 95% in well-managed alfalfa. The same tillage implements did not control weeds when used in an alfalfa stand where water was limiting. Alfalfa plants in these dry conditions were unable to recover from injury caused by tillage and weeds emergence subsequently increased. Shallow tillage implements such as a harrow or rotary-hoe decreased tansy mustard density and biomass about 50% at the first alfalfa harvest. Disking decreased alfalfa yield compared to the weedy check, while other treatments increased yield. However, only the aggressive harrow was comparable to herbicidas in a well-managed stand. Alfalfa yield was decreased by tillage with a disk, cultivator, rotary-hoe, or by paraquat when applied after alfalfa was growing vigorously. Injury most likely was exacerbated because this stand was not adequately irrigated or fertilized. Disking and cultivation at both locations, as well as late spraying of paraquat at Fort Collins decreased alfalfa height. Percent crude protein of forage increased when weeds were controlled adequately, but disking and cultivation decreased total protein per unit area because these implements injured alfalfa and caused lower forage yield. No treatments had an effect on alfalfa producto at the second cutting

Bibliographic Details

Main Author:	Pedreros L., Alberto
Other Authors:	Colorado State University
Format:	Tesis biblioteca
Published:	1997
Subjects:	alfalfa, control de malezas, control cultural,
Online Access:	https://hdl.handle.net/20.500.14001/54148
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