Abstract:
Ethiopia is one of the largest wheat producers in Sub-Saharan Africa with an estimated
area of 1.696 million ha and production of 4.642 million tones. The area suitable for
wheat production falls between 1,900 and 2,700 m above sea level and is produced
exclusively under rain fed conditions. However there is little knowledge among farmers on
the rates of N and P-fertilizer application at Jimma Arjo. Therefore, there is a need to
determine the rates of N and P fertilizer application on growth and yield of wheat.
Accordingly, a field experiment was conducted to evaluate the effect of different rates of N
and P fertilizer application on yield and yield components of wheat at Jimma Arjo,
western Ethiopia in 2018/2019 cropping season. A factorial combination of the rate (0,
23, 46 and 69 kgha-1) of N and rate (0, 10, 20 and 30 kg ha-1) of P was arranged in RCBD.
Rates of N and P fertilizer and their interaction had significantly affected days to heading,
days to physiological maturity, number of tillers, spike length, number of seeds per spike,
grain yield, straw yield, total biomass yield and harvest index. Meanwhile rates of N and
P fertilizer interaction had not significantly affected plant height. Application of the 69 kg
N/ha and 30 kg P/ha interaction increased number of tillers per plant by 264% as
compared with the control treatment. The lowest number of grains per spike (34.33) was
found in control plot and while the highest number of grainsper spike (74.33) was
recorded with 69 kg N and 30 kg P ha-1interaction. Application of the 69kg N/ha and 30
kg P/ha interaction increased number of grains per spike by 116.5% as compared with the
control treatment. The highest grain yield (6339.22 kg/ha) was obtained at treatment
combinations of 69 kg N/ha and 30 kg P/ha, followed by 69 kg N/ha and 20 kg
P/ha.Application of 69 kg N/ha and 30 kg P/ha interaction increased the grain yield by
145.7% as compared with the control treatment. Relatively high dry biomass yield
(18708.33 kg/ha) was obtained due to treatment combination of 69 kg N/ha and 30 kg
P/ha and followed by 69 kg N/ha and 20 kg P/ha which was 18236.11 kg/h. Application of
the 69 kg N/ha and 30 kg P/ha interaction increased the biomass yield by 56.99%and
straw yield by 32.5% as compared with the controltreatment.The effect of N on 1000-grain
weight was highly significant (P≤ 0.001), while the interaction was significant (P≤ 0.05).
The lowest harvest index (22%) was found in control plot and while the highest harvest
index (34%) was recorded with interaction of 69 kg N and 30 kg P ha-1.The economic
analysis revealed that the interaction of 69 kg N and 30 kg P ha-1 gave marginal rate of
return4617.32 Ethiopian birr ha-1and considered to be recommended for farmers atJimma
Arjo district. Since the increment trend of grain yield with N and P was not ceased to their
maximum tested rates, more rates should be experimented in the future to investigate the
declining point of the economical yield for these locations.
