The Effect of Preplant Nitrogen Fertilization and Soil Temperature on Biological Nitrogen Fixation and Yield of Alfalfa (Medicago Sativa L.) PDF Download

Author: Philip E. Shuler
Publisher:
ISBN:
Category : Alfalfa
Languages : en
Pages : 170

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Book Description
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.