Season, and Nitrogen Source and Rate Affect Development and Yield of Shallot

Abstract

ABSTRACT Three field experiments were conducted in 1999 and 2000 to assess the response of shallots (Allium cepa var. ascalonicum Backer) to nitrogen fertilizer sources and rates in eastern Ethiopia. Treatments comprised three nitrogen sources, urea, ammonium nitrate and ammonium sulphate, each at 0, 50, 100, 150 and 200 kg ha−1 N. Bulb yield was significantly increased with nitrogen fertilization up to 150 kg ha−1 in the main rainy season of 2000 when supplemental irrigation was applied. However, fertilization significantly reduced growth and yield of shallot in the main rainy season of 1999 and the short rainy season of 2000 under rain-fed conditions. Fertilization tended to increase bulb number per plant while reducing mean bulb weight. The dry matter and total soluble solids of bulbs from fertilized plots were either higher than or similar to those of unfertilized shallots. Ammonium nitrate produced significantly higher yields of shallots than ammonium sulphate, but did not differ from urea. Nitrogen source did not have significant effects on plant height, leaf number, bulb weight or bulb diameter. Higher nitrogen levels increased leaf and bulb nitrogen contents at harvest. The results indicated that nitrogen fertilizer should not be used for rain-fed shallots under low moisture regimes. Supplemental irrigation is essential in order to achieve high yields with nitrogen fertilization practices.