ONION PRODUCTIVITY AND SOIL FERTILITY STATUS AS INFLUENCED BY INTEGRATED USE OF INORGANIC, COMPOST TEA AND N2-FIXING BACTERIAl FERTILIZERS

Abstract

Two field experiments were carried out at the Experimental Farm of Sakha Agricultural Research Station in Kafr El-Sheikh Governorate at North Nile Delta Region. The experiments were conducted to study the response of onion to nitrogen fertilizer levels under different bio-organic fertilizers (compost tea and biofertilizer) as well as their interaction, on the growth and onion bulbs yield and its quality as well as storability of onion bulbs during the two successive winter seasons of 2010/2011 and 2011/2012. A split-split plot design with three replicates was used in this study. The main plots were designated to the three mineral nitrogen fertilizer levels (60, 90 and 120 kg N fad.-1), whereas foliar spraying treatments with compost tea at the same dose, 20 L fad.-1 (spraying with water; foliar spraying at 40 days after transplanting (DAT); foliar spraying at 40 and 60 DAT; foliar spraying at 40, 60 and 80 DAT and soil application, 30 DAT at rate of 30 L fad.-1) were randomly distributed in sub plots. While uninoculated and Inoculation with di-nitrogen fixing bacteria (Azotobacter and Azospirilium) were randomly distributed in the sub-sub plots. The obtained results could be summarized as follow: The two higher nitrogen levels (90 and 120kg N fad.-1) achieved a significant increase in vegetative growth characters (plant height, plant fresh weight, leaves dry weight/plant, bulb dry weight, plant dry weight and bulb diameter) as well as bulbs yield and quality (marketable and total bulbs yield as well as bulb diameter) as compared to the lower nitrogen rate (60 kg N fad.-1) in both seasons. The lower level of nitrogen (60 kg N fad.-1) resulted in a significant increase in TSS and dry matter % in addition to decrease weight loss% of onion bulbs at different storage periods in the two seasons. Growth and onion bulbs yield and its quality were highest due to application of compost tea on thrice than twice batches at the same dose and other treatments. The lowest values of bulbs weight loss% at 6 months were obtained under the application of compost tea on thrice batches. The effect of bio-fertilizer in plant height, Leaves dry weight/plant, bulb dry weight, plant dry weight, bulb diameter and bulb weight as well as bulb quality was evident in both seasons. In general, inoculation with Azotobacter and Azospirilium possitively increased all the previous characters. Total bulbs yield increased above 4.2 % in the plots treated by bio-fertilizer as compared with uninoculated treatment. Bio-fertilizer exert a significant effect on total weight loss of onion bulbs during different storage periods in the two seasons, where the lowest values were recorded with Azotobacter and Azospirilium inoculation. The interaction between mineral nitrogen and compost tea treatments had a significant effect on most studied characters. It is clear that the application of 90kg N fad.-1x foliar spraying with compost tea at 40, 60 and 80 DAT treatments produced the highest values of these traits in both seasons.