Abstract:
Sweet potato (Ipomoea batatas (L.) Lam) is economically important and a food security root
crop in Ethiopia. In addition to this, orange fleshed Sweet potato (OFSP) is the cheapest source
of β-carotene which is a precursor of Vitamin A whose deficiency (VAD) is a serious public
health problem in Ethiopia. However, its productivity and quality is very low due to low soil
fertility, lack of information on type and appropriate rate of fertilizers which have been
recognized to be deficient in Ethiopian soil. Hence, a field experiment was conducted at Jimma
Agricultural Research Center in 2017 cropping season to evaluate the effect of five different
rates of NPSB fertilizer kg ha-1
(0,100 ,159, 214 and 239 ) on growth, yield and quality of three
orange fleshed varieties (Kulfo, Tulla and Guntutie).The experiment was arranged in 3X 5
factorial RCBD with three replications. Data on growth, yield and quality were collected and
subjected to various data analyses. Results revealed that, the interaction effect of varieties and
NPSB rates were highly significant influenced the above ground biomass fresh weight, storage
root girth, marketable storage root yield per hector, harvestable index, storage root dry matter
content, β-carotene, ash (P <0.01) and Starch (P<0.05). Leaf area index and storage root
length were resulted significantly highest difference due to the main effect of variety (P<0.01).
Significantly the highest Storage root girth was obtained from Tulla with 159 kg ha-1 (79.35
mm). Guntutie with 159kg ha-1
, 214kg ha-1 and 239 kg ha-1 NPSB fertilizer resulted in
significantly highest difference in marketable storage root yield in ton per hectare (63.33 ton
ha-1
, 60.16 ton ha-1
and 63.44 ton ha-1
) respectively. Guntutie with 159 kg ha-1
resulted in
significant highest difference in harvestable index (0.58). Tulla with 159 kg ha-1 resulted in
significantly highest difference in storage root dry matter (35.4%) and Starch (28.21%).
Significantly highest difference of β-carotene contents was scored in the variety Guntutie, that
received 100 kg ha-1 NPSB fertilizer (1.4298mg/100g fwb). But the highest yield of β-carotene in
terms RAE or RDA retinol μg ha-1
(g ha-1
) was obtained in Guntutie with 159 kg ha-1 NPSB
fertilizer (46.4 g ha-1
) which was enough for 84.5 households (507 peoples) for 6 months.
Marketable yield ton ha-1 was highly significant and positively correlated with LAI (r=0.614),
SRL (r=0.711), β-carotene (r=0.495), MSRNP (r=0.555), MSRWP (1), HI (r=0.913).β-carotene
content was highly significant positively correlated to SRL (0.521), MSRWP(r=0.495), MY ton
ha-1
(r=0.495), LAI (r=0.315), HI (0.48). Storage root dry matter was high significant and
positively correlate with SRG(r=0.768), HI(r=0.299), Starch (r=0.771). The highest marginal
rate of return 805.19% were obtained in Guntutie with159 kg ha-1
. Use of selected orange
fleshed sweet potato with NPSB blended fertilize to the optimum rate is important for yield
improvement and qualities. Overall, 159 kg ha-1 NPSB should be recommended with Guntutie
for highest significant yield and β-carotene; with Tulla for its higher significant storage root dry
matter and starch content
