EFFECT OF MOTHER BULB SIZE AND NITROGEN FERTILIZER RATES ON GROWTH, SEED YIELD, AND YIELD COMPONENTS OF ONION (Allium cepa L.) AT LAELAY MAYCHEW DISTRICT, CENTRAL ZONE OF TIGRAY, NORTHERN ETHIOPIA

Abstract

Inappropriate uses of bulb size and without or with very low rates of nitrogen fertilizer application are major factors constraining onion seed production in Tigray. Therefore, a field experiment was conducted during 2023/2024 in Laelay Maychew Woreda Central Zone of Tigray to study the effect of mother bulb size (3-4 cm), medium (4.1-5 cm), and large (5.1-6 cm) and nitrogen fertilizer rates (0, 23, 46, 69, and 92 kg ha-1) on growth, seed yield, and yield components of onion. The experiment was laid out in a randomized complete block design (RCBD) with three replications. The results revealed that all growth and yield components were significantly (P < 0.05) influenced by the main effect of bulb size and nitrogen and nitrogen only. The tallest plant heights (cm), flower stalk length (cm) and Maximum numbers of flowers talks per plant were obtained from the plant that received 69 N kgha-1 as well as those large bulb sizes (5.1-6 cm).However highest values of flower stalk diameter (mm), wider umbel diameters (mm) and number of seed per umbel (550) were found from the plant treated at the rate of 92 kg ha-1 of N and medium mother bulb size (4.1-5cm).The maximum seed weight per umbel (2.32g), thousand seed weight (3.86g) and seed yield per plant (17.20g) and seed yield per plot (1197.91g) were obtained from the combination of large (5.1-6 cm) mother bulb size with 69 kg of Nha-1.The shortest days to 50% flowering and maturity were found from the treatment combination of 69 kg ha-1 with 5.1-6 cm mother bulb size. The highest seed yield per hectare (1983.25 kg ha-1) was obtained from the treatment combination of 69 kg and 5.1-6 cm mother bulb size. As the partial budget analysis revealed that maximum net field benefits (4550120) Ethiopian Birr with Marginal rate of return (56.88) were obtained from a bulb of 5.1–6 cm size grown with an application of 69 kg N ha-1. Hence, for high yield and economically feasible seed yield of onion, the treatment combination of 5.1–6 cm bulb size and 69 kg ha-1 of N are recommended for the study area. To make a final recommendation, it is advised to conduct the experiment again in the study area, as it was conducted for only one season and one site