Water Supply and Temperature Effects on Some Nutritive Constituents of Direct Sown Onion

Attila Ombódi,Andrea Lugasi,Hussein Gehad Daood,Mária Berki,Lajos Helyes

doi:10.15835/nbha44110257

Abstract

Irrigation is a prerequisite for economical onion production under dry conditions. However, its effect on dry matter and nutrient content often remains a concern for growers. A direct sown onion hybrid was grown under open field, rain-fed and irrigated conditions for three years, investigating the effects of air temperature and water supply on some nutritive constituents. Dry matter, storage sugar, total flavonol and total polyphenol content showed strong positive correlation with average air temperature and negative correlation with water supply. However, irrigation had a positive effect on storage sugar and dry matter content. Presumably better water supply during dry periods ensured by irrigation provided the basis for higher photosynthetic production, and hereby more dry matter partitioning and accumulation in the bulb, a storage organ. An unexpected decrease in vitamin C content was experienced in 2011 and 2012, compared to the result of 2010, which was explained by the hot and dry conditions of the pre-harvest irrigation cut-off period. Fibre and ash content was found to be the most stable nutritional characteristics, affected neither by the environmental conditions, nor by the irrigation. Irrigation has proved to be very beneficial for direct sown onion, doubling bulb yield while not affecting the nutritive quality negatively.

Highlights

Onions can be grown under different environmental conditions, being a well adaptable crop (Brewster, 2008)
Based on the results of an experiment conducted with onion grown from set on the same experimental farm at the same period (Ombódi et al, 2013), it can be stated that this yield-decrease was not caused by environmental conditions but too late sowing time
The current study revealed that irrigation of direct sown onion is strongly recommendable even from the viewpoint of product nutritional quality

Summary

Introduction

Onions can be grown under different environmental conditions, being a well adaptable crop (Brewster, 2008). Onions grown for their dried bulbs are rather difficult to produce, as environmental factors impact growth and development to a great extent (Welbaum, 2015). Literature categorises onion as a cool-season crop, tolerant of frost but with higher optimum temperature range than most cool-season vegetables (Rubatzky and Yamaguchi 1997). Supraoptimal temperatures negatively affect yield, bulb quality, dry matter content and bulb shape of onion (Welbaum, 2015), while lower temperatures cause later foliage fall down and longer duration of bulbing (Khokar, 2008). Besides affecting the growth of bulbs, temperature affects nutritional values, flavour intensity, dry matter and sugar content of the bulb (Lee and Suh, 2009)

Objectives

Methods

Results

Conclusion