Effect of Some Soil Additives and Mineral Nitrogen Fertilizer at Different Rates on Vegetative Growth, Tuber Yield and Fixed Oil of Tiger Nut (Cyperus esculentus L.) Plants .

Abstract

A pot experiment was carried out in the Experimental Station of Horticulture and Medicinal and Aromatic Plants, Fac. Agric., Mansoura Univ., during the two summer seasons of 2014 and 2015 to study the effect of different soil additives(rice straw compost (R.S.C.), town refuse compost (T.R.C.) and bio-fertilizer nitrobien) and different rates of mineral nitrogen fertilizer (ammonium sulfate (20.6% N) at 0, 50, 100 and 150 kg/fed) on vegetative growth, tuber yield , fixed oil percentage and compositionof tiger nut (Cyperus esculentus L.) plants. The results indicated that (R.S.C.or T.R.C.) fertilizer at the rate (15 m3/fed) plus nitrobien at the rate of(4 kg/fed) had a positive effect on vegetative growth of tiger nut plant; expressed as plant height (cm), number of tillers/pot, herb dry weight (g/pot) and harvesting characters including number of tubers/pot, tuber yield (g/pot), fixed oil percentage and oil yield (ml/pot), compared with other soil additive treatments.In addition,R.S.C. fertilizer was more effective on all studied characters in both seasons than either T.R.C. or nitrobien treatment. The highest level of nitrogen fertilizer (150 kg/fed) significantly enhanced all vegetative growth characters and some harvesting characters including tuber yield (g/pot) and fixed oil yield (ml/pot), but the maximum number of tubers per pot, fixed oil % were obtained from plants treated with nitrogen fertilizer at rate of 100 kg/fed compared with the other levels of nitrogen fertilizer. The combined treatment of 150 kg/fed nitrogen fertilizer with R.S.C. plus nitrobien was the most effective treatment to improve vegetative growth and harvest characters including tuber yield (g/pot), fixed oil yield (ml/pot), followed by the same combination using 100 kg/fed nitrogen fertilizer instead of 150 kg/fed nitrogen fertilizer with non-significant differences between the two treatments. The combined treatment of 100 kg/fed nitrogen fertilizer with R.S.C. plus nitrobien was more effective on number of tubers per pot, fixed oil % than any individual or combination treatments in both seasons. The gas liquid chromatography (G.L.C.) analysis identified twelve fatty acids in tiger nut fixed oil: six unsaturated fatty acids (oleic, linolinc, gondoic , palmitoleic , α-linolenic and heptadecenoic acids),as ranged from 78.50 to 79.21% of the oil and six saturated fatty acids (palmatic , stearic, myristic, arachidic, behenic and margaric acids),as ranged from 20.80 to 21.81%. The main components of the unsaturated fatty acids in tiger nut fixed oil were oleic acid (67.42-69.19 %), linolenic acid (9.42 – 10.27%), while the main saturated fatty acids in the fixed oil were palmatic acid (12.29 – 13.26 %) and stearic acid (6.60 – 8.13%).