Abstract:
Rice (Oryza sativa L.) is increasingly becoming an important food and cash crop in Ethiopia,
especially among small-scale farmers. However, its productivity is challenged due to lack of
appropriate agronomic practices and recommendations. Especially, uses of appropriate N
fertilizer and seed rates most importantly affect the productivity of rice increasing the cost of
production in subsistence farming. Thus, a field experiment was conducted at Gojeb, Gimbo
district in kaffa zone, southwestern Ethiopia during 2017 main cropping season with the
objective of determining optimum of N level and seed rate application. The experiment was laid
out in randomized complete block design in a factorial arrangement replicated three times. The
treatments consisted of five nitrogen rates (0, 32, 64, 96 ad 128 kg N ha-1
) and three seed rates
(50,60 and70kg ha-1
). The analysis of variance revealed that nitrogen rate highly significantly
(p<0.01) affected all of parameters studied .Similarly, the interaction between nitrogen level and
seed rate also highly significantly (p<0.01) affected total tillers and effective tillers, filled grain
per panicle, panicle length and grain yield. Nitrogen concentration, uptake and N-use efficiency
parametrs were significantly affected by the interaction effect. Highest number of effective tillers
(357.33) persquare meter, numbers of filled grain per panicle (102) and grain yield
(4755.2kg/ha) were recorded at 96kNha -1 with 70kg ha -1
of seed. Similarly, highest total and
straw N-uptake as well as gran N-content were recorded from 128kgNha-1 and 70kgha-1
from 96
kgNha-1
and70kgha-1
.The highest ANUE(23.63 and 22.37) was recorded from 64and 96kgNha1with 70kgha-1
seed rate.The highest PNUE (138.75 and 135.65) as well as ARE% (93.50 ) was
recorded. Therefore, increasing nitrogen rate and seedrate to optimume range 96kgN ha-1
and
70kgha-1
seed rate increased grain yield and yield component of rice. The correlation analysis
also indicated that there was positive and highly significant association between grain yield and
yield components and N uptake at maturity. The Partial budget analysis showed that highest net
benefit and marginal rate of return was obtained at 64kgN ha-1
and70kg ha-1
seed.Hence 64kgN
ha-1
and70kg/ha can be recommended in the study area. However, repeating the experiment over
years by increasing the N level would help to draw sound recommendation.
