This study evaluated the effects of tillage system, rotational tillage sequences, and
winter seed burial depth on weed seedling recruitment in irrigated cropping systems.
Notill (NT) planting of vegetable crops reduced emergence of hairy nightshade by 77 to
99% and Powell amaranth emergence from 50 to 87% compared to conventional tillage
(CT) and planting of crops. Cover crops suppressed weed emergence if soils were
undisturbed but not if soils were tilled in the spring. Four years of NT vegetable crops
reduced summer annual weed density by 48 to 79% at two sites. Rotational tillage
sequences that alternated between NT and CT only reduced summer annual weed density
if the shorter season crop of snap beans was paired with CT and sweet corn was paired
with NT. Hairy nightshade density decreased by 83 to 90% if NT was paired with the
longer season crop of sweet corn. Hairy nightshade seedling recruitment at 30.7 C was
more than 15 times greater for seeds buried at 6, 13 and 25 cm than when buried at 1 cm
in simulated NT. Recruitment potential was low in March and April but increased to a
maximum in May and June. Germination rates for seeds buried at 1 cm were lower and
mortality and dormancy greater than for seeds buried from 6 to 25 cm during the winter.
Protecting the seeds buried at 1 cm from rainfall during the winter increased seedling
recruitment from 0 to 2 of 10 buried seeds, but had a negligible effect on seed mortality
and dormancy. Treatment of seeds buried at 25 cm with 1 cm soil temperature reduced
recruitment from 4.8 to 2.3 of 10 buried seeds at 33.3 C, but did not significantly increase
seed mortality or dormancy. Estimates of seed drift using electronic transponders found
that 16% of the seeds at 5 cm moved to within the emergence zone for hairy nightshade.
Seed drift coupled with the faster germination rate and lower mortality of seeds buried at
12 cm or below predicts that hairy nightshade recruitment will be optimized when soil is
tilled in the spring. / Graduation date: 2005
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29497 |
| Date | 20 July 2004 |
| Creators | Peachey, Ronald Edward |
| Contributors | Smith, Carol Mallory |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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