Effect of intra-row spacing and NPS fertilizer rates on growth and bulb yield of onion (Allium cepa L.) in Saharti District, South Eastern zone of Tigray, Ethiopia

Abstract

Onion (Allium cepa L.) is one of the most important vegetable crops cultivated under irrigated conditions in the southeastern zone and some parts of the other region; the Tigray. The cultivation of onions requires proper supply of plant nutrients and plant densities. Despite of several constraints linked with onion production and productivity Inappropriate application rates of NPS fertilizer and inappropriate plant densities are one of the major constraints for onion production and growth in the study area. Therefore, this study was initiated with the aim of to determine Effect of intra row spacing and NPS fertilizer rates on growth and bulb yield of onion in Saharti District, South Eastern zone of Tigray, Ethiopia. The experiment was arranged in factorial combination of four level of intra row spacing (5, 7.5,10 and 12.5 cm) and four NPS fertilizer rates (0,150,200 and 250 kg ha -1) in a Randomized Complete Block Design with three replications. Growth and bulb yield components of onion data were collected and analyzed using GenStat software 18th edition. The analysis of variance showed that intra row spacing and NPS fertilizer had significant effect on days to physiological maturity, leaf length, leaf number per plant, bulb length and bulb diameter. The interaction effect of intra-row spacing and NPS fertilizer had significant effect on plant height, average bulb weight gram per plant, marketable bulb yield, unmarketable bulb yield, and total bulb yield. The highest marketable bulb yield 38.5 t ha-1 was obtained on the combined application of 200 kg ha -1 NPS fertilizer rate with 5 cm intra-row spacing. The highest net benefit (ETBirr 1,843,300) with the highest of Marginal rate of return (2942 %) was obtained on the combined application of 200 kg ha-1 NPS fertilizer rate with 5 cm intra-row spacing. Accordingly, onion producers in Saharti District and similar agro-ecologies can adopt the combination of 5 cm intra-row spacing and 200 kg ha-1 NPS fertilizer to achieve high marketable bulb yields, maximize net benefits, and obtain high marginal rates of return. However, as this study was conducted in a single location and season using the Bombay Red onion variety, further research is necessary to validate these findings across various seasons, locations, and with different improved onion varieties.