Effects of seed rate and inter row spacing on yield and yield components of food barley in Semen Ari Woreda, Ethiopia

A field experiment was carried out for two successive cropping seasons in 2017 and 2018 at Shama Bulket, Semen Ari Woreda, South Omo Zone, Southern Ethiopia, to determine optimum seed rate and inter-row spacing for food barley production. The experiment involved a factorial combination of three seed rates (80, 100 and 120 kg ha -1 ) and three inter-row spacing (20, 30 and 40 cm). The experiment was conducted using a randomized complete block design with three replications. The results indicated the treatments had significant effect in all parameters except plant height and spike length. Based on the result of this study, use of 30 cm inter-row spacing and 120 kg ha -1 seed rate is superior in grain yield (4481 kg ha -1 ) and total biomass (14.6 t ha -1 ). Therefore, use of 30 cm inter row spacing with seeding rate of 120 kg ha -1 can be recommended for food barley production at Shama Bulket kebele and its vicinity.


Introduction
Barley is an annual cereal crop, which belongs to grass family Poaceae, tribe Hordeae and genus Hordeum in which spikes have a zigzag rachis. Ethiopia and Asia have been suggested as probable centers of origin of barley (Martin and Warren, 1971).
Barley is one of the most important small cereal crops which ranks fourth after wheat, maize and rice in the world (Onwueme and Sinha, 1991) and third in Ethiopia both in terms of area coverage and production after teff and maize (Alemayehu, 1994). The mean area under barley production in Ethiopia has been estimated to be 892,500 hectares (ha) during the period 1980-1989(Berhanu et al., 2005. Barley is the most important food crop after teff (Eragrostisef sp. L.) and sorghum (Sorghum bicolor L.). Barleybased human food accounts for about 90% of grain, while the rest is used for beer making and animal feeds (Kiros, 1993). Barley straw is used as animal feed, thatching roofs and bedding (Kiros, 1993). The average national yield of barley is in the range of 0.8 to 0.9 tons ha -1 (CSA, 2002). Farmers in Semen and Debub Ari Woredas food barley used for human food (such as "kollo", "kineto" and "besso") and animal feed (barley straw).
Increased food barley production involves use of different agronomic practices such as improved variety, seed rate, spacing, fertilizer rate, and pesticide application at the recommended rate. When, assessing grain yield of a set of cultivars in different width of row spacing and seed rate changes are commonly observed in the relative yield performance with respect to each other.
In the high land parts of Semen and Debub Ari Woredas that are mostly under cereal cultivation, farmers plant barley with inappropriate row spacing or blanket recommendation. Barley productivity in Debub Omo zone is low because farmers have limited awareness on the appropriate planting row spacing and improved varieties (Biruk et al., 2018). Therefore, in order to minimize this constraint, determination of appropriate row spacing and seed rate trails should be conducted. Therefore, the objective of this study was to identify the optimum row spacing and seed rate for food barely that would enhance the productivity of food barley.

Description of the study area
This experiment was conducted at Shama Bulket kebele, Semen Ari Woreda South Omo Zone for two successive cropping seasons in 2017 and 2018. Shama Bulket is located about 840 km from Addis Ababa, and 610 km from SNNPRS capital city (Hawassa), in South Omo zone, which is in the south part of the country. It lies at 036 O 39' 08 " E longitude and 006 O 11' 35" N latitude at an altitude of 2570 masl. The study area has a mean annual rainfall and temperature ranging from 800-1000 mm and 18-32.1℃, respectively. The annual rainfall ranges from 1400-2300 mm. Average max and min temperature 22 0 C and 11 0 C.

Experimental treatments and procedures
The experiment involved a factorial combination of three seed rates (80, 100 and 120 kg ha -1 ) and three inter row spacing (20, 30, 40 cm). The experiment was conducted using a randomized complete block design with three replications. The test crop was food barley (variety called HB 1307).
The experimental field was prepared following the conventional tillage practice before planting. In accordance to the design, a field layout was prepared and each treatment was assigned randomly to experimental plots within each block. The gross plot size was 7.2 m 2 (2.40 m × 3.00 m).

Observation and measurement
Plant height (PH): The average height of five randomly selected plants from the net plot area of each plot was measured in centimeters from the ground to the top of spike.

Spike Length (SL):
The spike length was measured at maturity from five randomly selected plants of the inner rows in centimeter and the mean length was recorded on each plot measuring from the base to the upper most part of the spike excluding awns.

1000-kernel weight (g):
Thousand grains were counted after threshing randomly taken from each plot and weights were measured with sensitive balance.
Biomass yield (BY): Total biomass was measured by weighing the sun dried total aboveground plant (straw + grain) to constant weight from the net plot area of each plot.
Grain yield (GY): Grain yield was measured by taking the weight of the grains threshed from the net plot area of each plot and converted to kilograms.

Statistical Analysis
The collected data were subjected to ANOVA using SAS computer software (SAS Institute, 2000). Significance differences between and among treatments were delineated by LSD (least significance difference).

Plant height
The main effects of seed rate and inter row spacing as well as their interactions did not affect plant height significantly. Similar with the present finding, Soomro et al. (2009) noted that wheat sown at higher seeding rate (175 kg ha -1 ) produced greater plant height i.e. 101.25 cm followed by 150 kg ha -1 i.e. 99.09 cm and 125 kg ha -1 i.e. 94.27 cm. Another research finding by Worku (2008) also concluded that plant height increased consistently with increasing seeding rate from 72.7 cm at the seeding rate of 100 kg ha -1 to 80.4 cm at the seed rate of 150 kg ha -1 .
Higher seeding rate caused change in plant height and stem thickness because of the lower light penetration in to the plants canopy bed and more inter specific competition to more absorption light. These factors (higher seeding rate and lower light penetration) increasing inter node length, reducing stem thickness and increasing plant height (Otteson et al., 2007). Rahim et al. (2012) also reported that the significant difference on plant densities of 450 and 300 plants m 2 with highest and lowest plant height, respectively. Other researchers also reported in wheat that the height of plants grown at the lowest seeding rate was significantly lower than the height of plants grown at higher seeding rates (Haile et al., 2013;Laghari et al., 2011). Moreover, this result was in harmony with the finding of Fani et al. (2014) who indicated that with increasing density, plant height slightly increases and there after decreases that could be because restrictions on plant food sources therefore, in treatment 150 and 200 kg ha -1 , maximum plant height was observed.

Spike length
The main effects of seed rate and inter row spacing as well as their interactions did not affect plant height significantly (Table 1). However, the lower seeding rate and wider row spacing the spike length was higher compared to higher seeding rate and the higher seed rate. This might be due to more free space between plants at the lower seed rates and less intra-plant competition for available resources that resulted in higher spike length. The current result is indirectly in agreement with the finding of Zewdie et al. (2014) in that plant height and spike length are negatively interrelated. Another research finding by Gafaar (2007) stated that increasing sowing density from 200 up to 400 grains m -2 significantly decreased spike length. Similarly, Seleiman et al. (2010) reported that the longest spikes were obtained from 250 and 300 grains m -2 but without significant differences between both of them.

Grain yield
The analysis of data revealed significant difference due to interaction effects on grain yield in 2017 and 2018 cropping season (Table 3 & 4). The highest mean grain yield (4481 kg ha -1 ) was obtained from 30 cm inter row spacing and 120 kg ha -1 seed rate, while the lowest mean grain yield (2811 kg ha -1 ) was obtained from 40 cm inter row spacing and 80 kg ha -1 seed rate in 2018 (Table 4). Also, in 2017 cropping season the highest mean grain yield (2835 kg ha -1 ) was obtained from 30 cm inter row spacing and 120 kg ha -1 seed rate, while the lowest mean grain yield (878 kg ha -1 ) was obtained from 40 cm inter row spacing and 80 kg ha -1 seed rate (Table 3). Based on the present study, increasing seeding rate results in increasing grain yield. Similar with the present finding, Worku (2008) reported that grain yield increased as seeding rate increased from 50 to 150 kg ha -1 . Moreover,  concluded that grain yield was maximum at seeding rate of 150 kg ha -1 followed by 175 and 200 kg ha -1 , which are against the seeding rate of 125 kg ha -1 . The same result also reported by Iqbal et al. (2010) who concluded that seeding rate of 150 kg ha -1 produced significantly higher grain yield (4120 kg ha -1 ) followed by 175 and 200 kg ha -1 seeding rates (3904 and 3785 kg ha -1 ).

Thousand seed weight
The analysis of data revealed significant difference due to interaction effects on thousand seed weight (Table 4). The highest mean thousand seed weight (51.83 g) was obtained from 40 cm inter row spacing and 80 kg ha -1 seed rate, while the lowest mean thousand seed (40.83 g) was obtained from 20 cm inter row spacing and 80 kg ha -1 seed rate (Table 4).
The result showed that seeding rate and row spacing had inverse relation in affecting thousand kernels weight. The lowest kernels weight was obtained from the highest seeding rate and this might be due to thickening of population density, which resulted competition among nearby plants nutrients and moisture. Similar with the present finding, Baloch et al. (2010) concluded that the higher the seeding rate in bread wheat resulted in decrease in 1000-kernels weight. Another research finding by Hiltbrunner et al. (2005) also noted that as seeding rate increased, 1000kernel weight decreased. Similarly, Fani et al. (2014) showed that at high densities (250 and 300 kg ha -1 ) thousand seeds weight declined whereas in low densities of 50 and 100 kg ha -1 , thousand seed weights increased..

Total biomass
The analysis of data revealed significant difference due to interaction effects on total biomass (Table 4). The highest mean total biomass (14.6 t ha -1 ) was obtained from 30 cm inter row spacing and 120 kg ha -1 seed rate, while the lowest mean grain yield (7.63 t ha -1 ) was obtained from 40 cm inter row spacing and 80 kg ha -1 seed rate.
The result showed that when seeding rate increased, the total biomass increased total biomass. Zewdie et al. (2014) reported a positive association between biomass yield and plant height and thus taller plants resulted higher biomass yield. Similar with the present finding, Jemal et al. (2015) also reported that higher biomass yield was recorded when seed rate increased from 200 and 175 kg ha -1 . Similarly, Iqbal et al. (2010) found that biological yield increased as seeding rate increased from 125 kg ha -1 to 150 and 175 kg ha -1 .

Conclusion and Recommendation
From the present study, it is possible to conclude that both seeding rate and inter row spacing affect yield and yield related traits of food barley.
The results indicated significant differences in all parameters except plant height and spike length. Based on the results, among treatments use of 30 cm inter row spacing and 120 kg ha -1 seed rate is superior in grain yield (4481.53 kg ha -1 ) in 2018 and (2835 kg ha -1 ) in 2017 cropping season. Therefore, this study investigated and concluded that inter row spacing of 30 cm and seeding rate of 120 kg ha -1 performed better and gave higher grain yield (4481.53 kg ha -1 ) and (2835 kg ha -1 ). However, the highest spike length and thousand kernel weight were recorded in the lowest seeding rate (80 kg ha -1 ) and the wider inter row spacing (40 cm).
Therefore, use of 30 cm inter row spacing with seeding rate of 120 kg ha -1 can be recommended for food barley producing farmers at Shama Bulket kebele and its vicinity.
References Alemayehu, A. 1994. Drought stress during the belg season and selection of barley land races in the north Shewa, Ethiopia. Nile Valley and Red Sea Regional Program on season food legume and cereals, ICARADA/NVRSRP. Ethiopia. pp. 209-216. Ali, M., Ali, L., Sattar, M. and Ali, M.A. 2010. Improvement in wheat (Triticum aestivum L.) yield by manipulating seed rate and row