Assessing Selection Parameters for Improving Yield in Organically Grown Onion

An increasing interest in organically grown vegetables has led to an increasing demand to select cultivars meeting the requirements of the production system. This two-year field study was undertaken to assess the effects of organic and conventional nutrient regimes on onion (Allium cepa L.) yield and several yield contributing characters, as well as to identify the traits that could be important when selecting genotypes attended for different production systems. The trial involved five commercially grown onion cultivars and four nutrient regimes: bacterial fertilizer, fully decomposed farmyard manure, without fertilization (organic) and NPK fertilization (conventional). Onion yield, bulb weight, number of bulbs plot⁻¹, number of days from sowing to emergence, vegetation period, plant height, neck diameter, neck length, bulb diameter, bulb height and bulb index have been analyzed. Significant differences concerning all analyzed traits have been found among the cultivars, treatments and years, with significant corresponding interactions. The obtained results imply the specific adaptation to the particular treatments and weather conditions and therefore the possibility to select onion cultivars performing well in organic environments. Path coefficient analysis revealed positive direct effects of bulb weight and number of bulbs plot⁻¹ on yield, as well as negative direct effects of plant height and number of days from sowing to emergence; therefore, those traits should be considered when selecting genotypes attended for different production systems. Other traits affected yield indirectly, mostly positively via bulb weight.