Response of Onion Productivity and Storability to Some Sources, Rates and Times of Application of Nitrogen Fertilizers

摘要

Two field experiments were carried out during the two seasons of 2008/2009 and 2009/2010 at Sakha Agricultural Research Station to study the effect of N-fertilizer sources i.e., ammonium nitrate (33.5% N) and Enciabein (40% N) as a slow release N fertilizer. Six nitrogen treatments including three rates (60, 90 and 120 kg/fed.) and two times of application were used. These amounts were divided in to two equal doses applied at 30 and 60 days after transplanting (DAT), or applied in three equal doses,at transplanting, 30 and 60 DAT, on plant growth, yield and quality, as well as storability of onion plants (Allium cepa L. cv. Giza 20). The main results could be summarized as follows:Ammonium nitrate treatments were detected as the best source of nitrogen for vegetative growth characters (plant height, bulb diameter and fresh and dry weight of whole plant)at 90 and 120 DAT, bulbs yield (marketable, culls and total bulbs yield/fed.) as well as bulb quality (average bulb weight, bulb diameter, TSS and dry matter percentage) except storability of onion bulbs was decreased.The highest values concerning the previous characters and total loss of bulbs weight during storage periods were obtained in plants which received 120 kg N/fed. at two equal doses(at 30 and 60 DAT). On the other hand, TSS and dry matter percentage recorded maximummean values by adding 90 kg N/fed. at two or three equal doses in both seasons.Mean while, highly significant differences concerning the interaction effects between nitrogen fertilizer sources and different nitrogen treatments were noticed. Adding 120 kg N/fed. as ammonium nitrate at two equal doses in 30 and 60 DAT gave the vigourplant growth, marketable yield and total bulbs yield with the best quality and caused a reduction in the storability of onion bulbs in 1~(st) and 2~(nd) seasons.