Effect of Varying Concentrations of Nitrogen and Phosphorus Supply on the Growth of Enset (Ensete Ventricosum (Welw.) Cheesman) Suckers

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1999-06

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Addis Ababa University

Abstract

The effect of a range of factorially combined concentrations of nitrogen and phosphorus on the growth of enset suckers (Ellsete velltricoSlI1II (Welw.) Cheesman) was studied in a greenhouse using Randomized Complete Block Design with seven replications. The experiment was conducted on soil samples collected from Sidamo, Agereselam as growing medium. To these soils, four concentrations of nitrogen (0, 10, 50 and 250 mgl-l , designated as N" N2 , N3 and N4 , respectively); and four concentrations of phosphorus (0, 9, 27 and 81 mgl-l , designated as PI' P2 , P3 and P4 , respectively) were factorially combined and added to investigate sixteen treatments. The appropriate nutrient solutions were applied to the plants at a rate of 200 ml twice in a week Enset suckers responded to an increase in concentrations of nitrogen and phosphorus in solution through increases in pseudostem girth, leaf area, total biomass and tissue nitrogen and phosphorus contents. Increasing concentrations of nitrogen and phosphorus in solution resulted in significant increase (P < 0.001) in pseudostem girth and total dry weight. The interaction between the two nutrients were also highly significant (P<O.OOl). Plants that received nitrogen (250 mgl-l ) and phosphorus (81 mgl-l ) produced the highest dry matter compared to other treatments and the control. Reduction in the supply of the two nutrients resulted in higher root : shoot ratio and nitrogen and phosphorus stress levels. In comparison with nitrogen, higher levels of phosphorus resulted in higher root: shoot ratio. Total leaf area was also significantly (P < 0.001) affected by increasing concentrations of nitrogen and phosphorus in solution, although the effect of phosphorus on total leaf area was shown only at higher levels of nitrogen combined with higher levels of phosphorus (Le. at N3P3, N3P., N,P3 and N4P.). Of the parameters of growth studied, leaf area increase/week was found to be a sensitive measure of nutrient stress in enset suckers. Nitrogen and phosphorus concentrations less than SO mgl-' and 27 mgl-', respectively resulted in more than 40 percent nutrient stress. The concentration of nitrogen in the shoot ranged from 0.61 ± 0.06 percent (at N,P,) to 1.04 ± 0.05 percent (at N.P.). Root nitrogen ranged from 0.19 ± 0.03 (at N,P,) to 0.47 ± 0.06 percent (at N.P.). There was a significant increase in shoot and root nitrogen following increased concentrations of nitrogen in solution, but was not significantly affected by phosphorus levels. Phosphorus concentrations in the shoot ranged from 0.11 ± 0.02 percent (at PIN,) to 0.48 ± 0.05 percent (at P.N.). Phosphorus concentration in the root ranged from 0.03 ± 0.02 (at PIN,) to 0.21 ± 0.01 (at P.N.). Phosphorus concentration in the tissue increased following increased concentration of phosphorus in solution, which was also significantly affected at higher nitrogen concentration (250 mg-') in solution. Of the two nutrients studied nitrogen was found to be more limiting to the growth of enset suckers.

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Biology

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