Abstract:
Field experiment was conducted during 2014-15 to assess the effect of combined NP rate on yield, yield
components and grain protein of bread wheat varieties on Robe Farms, Bale Zone of Oromyia, South-eastern
Ethiopia. The NP rates combinations were N
0P0, N46P23, N92P46, N138P69, N184P92 and N
46P46 kg/ha, .whereas
varieties were Kakaba, Pavon-76 and Dandaa. Experiment was designed in factorial RCBD with eighteen
treatments and three replications. There was significant response of wheat to fertilization. The higher levels of
N138P69 and N
184P92 kg ha
-1
gave significantly higher grain yields and grain protein than lower levels, including
state level recommendation of N46P46 kg/ha. Dandaa produced significantly higher grain yield than Pavon-76
and Kakaba. The protein content was similar for Dandaa and Pavon-76, but significantly higher than Kakaba.
The quadratic yield responses showed high correlation between yields and fertilizer rates for varieties (R
2
0.99,
0.98, 0.84) and wheat in general (R
2
0.98). The yield potentials of Dandaa, Pavon-76 and wheat in general
were 71.4, 61.5 and 67.1 q ha
-1
, achieved at N
147P74, N133P66 and N
191P96 kg ha
-1
,
respectively. The optimum
yields of Dandaa, Pavon-76 and wheat in general were 71.2, 61.2 and 66.8 q/ha, achieved at N
135P68, N121P60
and N
170P85
kg ha
-1
,
respectively. Kakaba had still not reached maximum yield. The profit was higher for
Dandaa (25,659 birr/ha) compared to Pavon-76 (20,608 birr/ha) and wheat in general 23,872 birr/ha. Dandaa
and pavon-76 were more nutrient-use efficient than Kakaba at low to high application rates with higher
marginal rate of returns (MRR) and agronomic efficiency. Accordingly, Dandaa and pavon-76 varieties may be
more universal for adoption under varied situations. The Kakaba variety, on the other hand, showing promise
only at very high rate of fertilization may be less preferred for adoption in areas with low to medium fertility
and resource-poor farmers. The results indicating the need for fertilization three to four times the state level
recommendations may be further validated through verification trials on farmers’ fields with same agroecology, in cooperation with Commercial Agricultural Development enterprises and private investors.
