Four levels of nitrogen fertilization in two onion (Allium cepa) varieties
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Colberg, O., & Beale, A. (1991). Four levels of nitrogen fertilization in two onion (Allium cepa) varieties. The Journal of Agriculture of the University of Puerto Rico, 75(1), 1–10.


The effect of fertilization with 0, 75, 150 and 225 kg/ha on onion varieties Ringer Grano and Texas Grano 502 was studied on San Antón soil (Cumulic Haplustolls). Ammonium sulfate was used as the source of N. Basic applications of K2O and P2Owere made by hand, at a rate of 155 and 25 kg/ha, respectively. Planting distances were 30 cm between rows and 7.5 cm between plants. The experimental plot consisted of four beds with two rows per bed. Nitrogen fertilization was performed in two equal applications. The first half was applied four weeks after germination; the second half, 30 days after the first application. Sprinkle irrigation was used. Variety Ringer Grano was the sample for nutrient absorption analysis. Results showed that variety Ringer Grano produced 28.5 t/ha at 75 kg N/ha. There were no significant differences among 75, 150 and 225 kg N/ha. treatments within this variety. Variety Texas Grano 502 showed its best production at 225 kg N/ha., 13 t. There were no significant differences among this treatment and 0, 75 and 150 kg N/ha. There were no significant differences in plant height, bulb diameter, number of leaves and plant dry weight. Ringer Grano variety showed higher green foliage and bulb weight at 75 kg N/ha than the other treatments eighteen weeks after seeding. The highest nutrient absorption when no N was applied was found 116 days after seeding. These samples contained 14 kg N/ha, 12 kg P/ha, 60 kg K/ha, 26 kg Ca/ha and 4 kg Mg/ha. When 75 kg N/ha was applied to the soil, the highest nutrient absorption in the plant was found 131 days after seeding, with 63 kg N/ha, 13.7 kg P/haf 51 kg K/ha, 38 kg Ca/ha and 10 kg Mg/ha.
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