No-tillage winter wheat (Triticum aestivum L.) grown in a
wheat-fallow cropping system has consistently produced lower grain
yields than conventionally tilled soils in the semiarid Pacific
Northwest. A 2-year study was conducted in a long-term tillage trial
at Moro, OR to determine factors responsible for differences in wheat
growth and yield as affected by moldboard plow, stubble mulch, and
no-tillage fallow method. Soil water, soil mineral N, plant N
uptake, soil temperature, above-ground dry matter accumulation, and
yield components were measured.
The highest fallow efficiency during both years was achieved by
stubble mulch tillage, followed by the plow and no-tillage systems.
Accelerated water loss from no-tillage fallow occurred during the
hot, dry summer due to uninterrupted capillary flow. The main yield
limitations to no-tillage technology in this study were: (1)
diminished seedzone water at planting time in the fall which resulted
in reduced germination and stand establishment; (2) cooler spring
soil temperatures which slowed crop development and dry matter
accumulation, and; (3) production of fewer spikes per unit area.
The second objective of this study was to determine if late
season seedzone water loss from fallow could be reduced by altering
the physical characteristics of the dust mulch. Loss of seedzone
water appears to accelerate in late August and September because of
increased diurnal heat flux. Compacting the soil surface with a
roller in mid-August increased surface bulk density and volumetric
water content to depths as great as 10 cm. Evaporative water loss
from compacted plots, however, occurred at a faster rate than from
control plots and, by mid-September, there were no differences in
seedzone water content among treatments. Increased soil thermal
conductivity appeared to be the reason for accelerated water loss in
compacted treatments. Although water loss occurred at a faster rate
in compacted treatments, compacting fallow soils with a roller
immediately prior to fall seeding may increase winter wheat
germination, emergence, and stand establishment during years of
marginal seedzone water. / Graduation date: 1992
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36389 |
| Date | 06 April 1992 |
| Creators | Schillinger, William F. |
| Contributors | Bolton, Floyd E. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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