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