EFFECT OF PARTIAL REPLACEMENT OF MINERAL N-FERTILIZER BY USING ORGANIC AND BIOFERTILIZERS ON GROWTH AND CHEMICAL COMPOSITION OF SOLO PAPAYA PLANTS

Abstract

An experiment was conducted under the full sun at the Research Tropical Farm, Kom Ombo, Hort. Res. Inst., Aswan, Egypt during 2016 and 2017 seasons to explore how far we can replace mineral N fertilizer which reduces the medicinal benefits of some plants by tea compost and EM biostimulant as safe and friend sources for human, animal and environment, and to study the effect of these sources when applying them at various rates in sole and combined treatments, including: control (no fertilization), 100 % NH4NO3 as a mineral N source (MN) at the recommend dose (8 g/plant), 75 % MN (6 g/plant) + 100 ml tea compost (TC) + 25 ml effective microorganisms (EM) solution, 50 % MN + 200 ml TC + 50 ml EM, 25 % MN + 300 ml TC + 75 ml EM and 400 ml TC + 100 ml EM as bioorganic treatment on growth and quality of 4-months-old seedlings of papaya (Carica papaya L. Solo) grown in 20-cm-diameter black polyethylene bags filled with about 4 kg of loam. The previous treatments were applied as a soil drench per plant, four times with one month interval commencing from mid of June until mid of September. The obtained results indicated that the means of all vegetative and root growth parameters, contents of chlorophyll a, b, carotenoids, total carbohydrates and total soluble sugars in the leaves, as well as the uptake of N, P, K and Mg by plants were significantly increased in response to the different sole and combined fertilization treatments used relative to the control means in most cases of the two seasons. Incorporating both tea compost and EM biofertilizer with mineral N fertilizer at any rate in the former combinations gave better results than applying either mineral N fertilizer alone or tea compost with EM in the combined bioorganic treatment. In addition, means of the aforenamed measurements were progressively increased as the application rate of both tea compost and EM was increased, which was accompanied in the same time with a gradual decrement in rate of mineral N fertilizer. Thus, the dominance in both seasons was for the combination of 25 % mineral N (2 g/plant) + 300 ml tea compost + 75 ml EM, which gave the highest values at all, except for the bioorganic combination (400 ml tea compost + 100 ml EM), that attained the utmost high content of chlorophyll a, b, carotenoids, total carbohydrates and total soluble sugars contents over all the other treatments. Hence, it is advised to fertilize the four-months-old papaya seedlings planted in 20-cm-diameter black polyethylene bags with the low dose of mineral N fertilizer (2 g/plant) + 300 ml of compost tea + 75 ml of EM biostimulant to get the best growth and highest quality.