Mechanical management of weeds - Ecological Management of Agricultural Weeds - page 167

• Approximately 5 cm of soil should be scraped from the ridge at planting .This is
sufficient to remove residue and most weed seeds shed the previous
season while retaining the ridge bases intact.Maintenance ofthe ridge
bases facilitates cultivator guidance and fosters development oforganic
matter and macropores in the crop row.
• The ridge should be wide ( 30 cm) and relatively flat topped so that the planter

cleans soil from a substantial strip on either side of the row. Otherwise,weeds
will emerge from surface seeds near the row where they will be difficult
to control.
• Awinter cover crop on the ridges slows emergence and growth ofweeds
in the spring.Since small weeds are more susceptible to the scraping
action ofthe planter, a cover crop helps insure that the planter will destroy any
weeds that establish prior to planting .
• Ridge-building should occur early enough in the crop growth cycle and tools kept far
enough from the row to avoid root pruning the crop. Root pruning is always an
issue in inter-row cultivation,but it is more likely in ridge tillage systems
because the tools works deeper relative to the base ofcrop plants.

As with all reduced tillage methods, populations of perennial weeds some-
times increase with ridge tillage (Clements et al ., 1996). Another significant
problem is that the method is suited only to crops planted in widely spaced
rows. In particular, rotation with sod crops requires destruction of the ridges
(Cox et al ., 1992). Despite these problems, ridge tillage is an important soil
conservation and weed management system, particularly in regions where
maize, sorghum, and soybean are the predominant crops.

Stale seedbed and false seedbed
Since tillage promotes germination of many weed species (see
Chapter 2), tillage followed by destruction of weed seedlings with minimal
further soil disturbance often leads to lower weed density in the crop. This is
referred to as the stale seedbed method of planting. The technique is espe-
cially useful for providing reduced competition early in the development of
small-seeded or slowly establishing crops like onion and carrot. Much recent
work has explored application of the technique to soybean,and in this context
it is largely used to avoid tillage during late spring on clay soils (Heatherly et
al ., 1993; Lanie et al ., 1993, 1994; Oliver et al ., 1993). Usually, removal of the
weeds is accomplished with a herbicide, but flaming can also be used. Balsari,
Berruto & Ferrero (1994) found that a single flaming four days after irrigation
and one day before transplanting lettuce seedlings reduced weed densities by
62% and produced a net income similar to chemical treatment with propyza-
mide (pronamide).