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Project description

Influence of Oat Intercropping on Weed Suppression in the Final Year of an Alfalfa Stand. (90BC077)
Program UC IPM competitive research grants program
W.T. Lanini, Botany, UC Davis
Host/habitat Alfalfa
Pest Unspecified Weeds
Discipline Weed Science
Biological Controls
Start year (duration)  1990 (Two Years)
Objectives Demonstrate weed suppression by interseeding oats (grass) into the final year of an alfalfa stand.

Determine the yield and composition of the oat (grass)alfalfa mixture.

Economically assess the cost/benefit relationships of oats (grass) interseeded into the final year of an alfalfa stand.

Final report Interseeding oats or perennial grasses into thin alfalfa stands reduced weeds by providing competition. Studies were conducted to evaluate interseeding oats or forage grasses into established alfalfa, assessing variety, seeding rate, and nitrogen rate and their effect on weed cover and hay yield. Grass treatments were compared to paraquat treatments or cultivation. Hay yields were generally increased when oats or grasses were interseeded. Oats were found to provide good first cutting yield increases but had no effect on subsequent cuttings, as they failed to regrow after cutting. Perennial grasses were slower to establish than oats but regrew after cutting; yield increases in second and subsequent cuttings were observed, particularly with tall fescue and orchardgrass. Weeds were consistently reduced more by grass interseeding than by paraquat application or cultivation alone. Cultivation without grass planting often increased weed density over other treatments. Paraquat has no residual activity and provided no control of summer weeds. Oats were effective in controlling winter weeds and spring germinating after the first cutting. Perennial grasses were more effective than oats at suppressing summer weeds. Interseeding a combination of oats and a perennial grass provided good yield increases and weed control.

Grass/alfalfa hay prices were generally close to that received for alfalfa hay. Price depended upon the market, with grass/alfalfa hay receiving the highest prices when sold to horse markets. Dairy producers preferred pure alfalfa hay and generally buy grass/alfalfa hay only at lower prices.

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