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.
