Commercial N fertilizer formulations, ammonium nitrate, calcium nitrate, sodium nitrate, potassium nitrates (15-0-14 and 13-0-44) applied at 84 and 168 kg N/ha in 3 or 5 split applications did not affect total marketable yield of dry onion. Application frequencies causing an increase in total amount of N applied during the spring months (Feb.-Apr.) increased marketable yield by 5 MT/ha. Bulb decay was the highest when ammonium nitrate was applied, whereas the least number of decayed bulbs resulted from sodium nitrate applications. Plants grown with potassium nitrate (13-0-44) were most susceptible to cold injury. Ammonium nitrate and sodium nitrate applications produced the highest percentage of onions that bolted. The lowest percentage of plants showing bolting incidence resulted from calcium nitrate applications. Bolting of onions was closely associated with rapid growth and increased onion size. However, cold injury and bulb decay were not influenced by these growth factors.
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