Cereal residue effects on weeds and cucumbers

Abstract

Cereal residues suppress the development of small seeded, summer annual weeds. The focus of this study was to determine whether cereal residues can be used to suppress weeds in cucumber production systems in the Pacific Northwest. In the first of three experiments, cereal residues of fall-planted, spring-killed cover crops suppressed weed density and dry matter by 65 and 34 percent respectively, compared to treatments with no residue at 6 Weeks after cucumber planting. But this level of weed suppression was not an advantage compared to conventional tillage and cultivation. In another scenario, glyphosate was applied over the cereal residues post-plant but before cucumber emergence. Weed density was unaffected but weed dry matter was dramatically reduced. Several residue treatments reduced weed dry matter to a level comparable to the cultivated, conventional tillage control. Weed suppression at the end of the harvest season was unacceptable in all residue treatments, however. Cucumber yield was severely reduced in residue treatments due to weed competition. A second experiment quantified the effect of cereal residues on cucumber growth in no-till conditions and the mechanisms affecting cucumber growth. An inert mulch of Populous excelsior wood shavings significantly increased cucumber growth compared to a natural barley residue even though soil temperatures were equal. Tillage improved plant growth but activated charcoal and metalaxyl treated seeds did not affect growth in no-till conditions. A third experiment examined the weed suppression of a stale seedbed system that included barley and rye planted 0, 2, and 4 weeks before cucumber seeding. Barley and rye improved weed suppression by 85 percent compared to the same treatments without cereals. Cucumber yield of all treatments was less than the weed-free control, but comparable with average yields of commercial cucumber production.