The usefulness of preplant nitrogen (N) in establishing
alfalfa in colder production areas has not been
well characterized. This study was conducted to determine
the effect of preplant N and soil temperature on
yield, percent N derived from biological nitrogen fixation
(PBNF), and shoot N concentration in alfalfa (Medicago
sativa L. cv. 'Vernema'. Field experiments were
conducted in 1987 and 1988 at Powell Butte, OR, to determine
the effect of five levels of preplant N (0, 10, 20,
40, 60 kg ha⁻¹) on yield and shoot N concentration of alfalfa.
Growth chamber experiments were conducted from
1989 through 1991 to examine the effect of five levels of
preplant N (0, 10, 20, 40, 80 kg ha⁻¹) and three day/ -
night soil temperatures (18/12°C, 24/16°C, 27/21°C) on
yield, PBNF, and shoot N concentration of alfalfa.
In field experiments, preplant N had no effect on
shoot N concentration in either year. In 1987 there was
no effect of preplant N on dry matter yield. Application
of 20-40 kg N ha⁻¹ preplant N increased dry matter yield
in 1988. In growth chamber experiments, the highest rate
of dry matter accumulation occurred at a soil temperature
of 24/16°C. At 18/12°C and 24/16°C, 40 kg ha⁻¹ preplant
N resulted in increased shoot and root dry matter yield.
At 18/12°C, 80 kg ha-¹ preplant N increased PBNF 14%
relative to the zero N control. There was no effect of
preplant N on PBNF in plants grown at 24/16°C and 27/-
21°C. The rates of shoot N accumulation were similar at
18/12°C and 24/16°C, and were higher than at 27/21°C.
Shoot N concentration was not affected by preplant N
treatments.
The use of 20-40 kg ha⁻¹ preplant N may result in
increased yield without decreasing PBNF when: 1) soil
temperature remains below 15°C for at least two weeks
after planting, and 2) soil nitrate level is less than 16
mg kg⁻¹. Proper assessment of the use of preplant N in
alfalfa establishment requires a careful consideration of
both soil temperature and soil N availability. / Graduation date: 1992
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36552 |
| Date | 19 July 1991 |
| Creators | Shuler, Philip E. |
| Contributors | Hannaway, David B. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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