4.2.2. Number of effective nodules The ANOVA result revealed that number of effective nodules affected by both the main effects of bio-fertilizer rate and inter-row spacing and their interaction (appendix table 1). The interaction effect of bio-fertilizer and inter-row spacing was highly significant (P ˂ 0.001) (Table 4). The highest number of effective nodule (22.8) was recorded from the combination of treatments that inoculated with the highest bio-fertilizer rate (0.75kg ha-1) with widest inter-row spacing (50cm) whereas; the lowest number of effective nodule (12.5) was recorded at control and narrowest (30cm) inter-row spacing. These variation in number of effective nodules among the treatments might be due to the soil contained indigenous rhizobium that could be activated and effective in nodule formation by rhizobium inoculation and may be due to wide spacing that enables plant to get more nutrients, light and water with relatively less competition. Also increased nodule number with Rhizobium inoculation could be associated with the efficiency of introduced rhizobia to compete with indigenous bacteria dwelling in the soil. This result is in line with Bezabih, Walelign and Girma (2018), reported that seed inoculation with Rhizobium inocula produced significantly highest number of effective nodule per plant than control. Also Abebe and Tolera (2014) stated that Rhizobium inoculation produced significantly highest nodule number of active nodule per plant than control. Furthermore, results are in line with the findings of Sajid et al. (2011) who revealed that the Rhizobium inoculation significantly enhanced nodule number. Table 5 Interaction effects of bio-fertilizer rate and inter row spacing on leaf Area Index and Number of effective nodules at Bonga agricultural research center in Kaffa Zone, in 2019 main cropping season. LAI(cm2) NEN Row space (cm) Biofert (kg ha-1) 30 0 224.7l 12.5l 30 0.25 373.3i 15j 30 0.5 378.7h 15.8h 30 0.75 533g 16g 40 0 246k 13.5k 40 0.25 564f 17f 40 0.5 592e 19e 40 0.75 689d 20d 50 0 278j 14j 50 0.25 794c 21c 50 0.5 966.3b 22b 50 0.75 978.3a 22.8a LSD(0.05) 4.2 0.7 CV (%) 0.75 10.8 Means with the same letters in the same column (P˂0.05) are not significantly different; where LAI＝leaf area index, NEN＝number of effective nodules. 4.2.3. Number of leaf per plant The result of the analysis of variance showed that number of leaf per plant was significantly affected by the main effect of both bio-fertilizer rate and inter-row spacing (Table 6). The interaction effect of bio-fertilizer rates and inter-row spacing was not significant. The main effect of bio-fertilizer application and inter-row spacing was highly significant (P ˂ 0.001) (Appendix table 2). Accordingly, the highest number of leaf (43.6) of per plant was recorded at highest bio-fertilizer rate (0.75kg ha-1) whereas; the lowest numbers (22) per plant was recorded at control. This is because high rate of bio-fertilizer inoculation cause high vegetative growth by the soil contained indigenous rhizobium that could be activated nutrient uptake of plant and as a result initiating the vegetative growth of plant. This study was in line with Abebe and Tolera (2014) stated that Rhizobium inoculated plants of faba bean produced significantly highest number of leaf per plant than control. Also Bezabih, Walelign and Girma (2018), that climbing bean varieties inoculated with rhizobium showed increased number of leaf per plant after six weeks of planting. Likewise, widest inter row spacing produced highest number of leaf per plant than narrowest. The result of the analysis of variance showed that the highest number of leaf (32.5) was recorded at widest inter row spacing (50cm) whereas; the lowest number (21) at narrowest inter-row spacing (30cm).This might be due to less competition for resources (light, nutrient and water) at wide spacing and this encourages more vegetative growth as well as more number of leaf productions. This result was in agreement with Terefe (2012) who stated more number of leave at wider row spacing on faba bean. 4.2.4. Plant height The result of the analysis of variance revealed that plant height was significantly affected by the main effect of both bio-fertilizer rate and inter-row spacing (Table 6). The interaction effect of biofertilizer rates and inter row spacing was not significant. The main effect of bio-fertilizer application and inter-row spacing was highly significant (P ˂ 0.001) (Appendix table 2). The longest plant height (135cm) was recorded at highest rate of bio-fertilizer (0.75kg ha-1) whereas; the shortest plant height (101cm) was recorded from the control treatment. This might be due to the increased vegetative growth because of high bio-fertilizer rate applied initiated nutrient uptake by changing soil Nitrogen “N” to available or ionic form (NO3-). The present work is in agreement with the findings of Bezabih (2018), Endalkachew et al. (2016) who were reported that an increase in plant height of lentil in response to inoculation with rhizobium strain. Also this result is in line with the report of Impact of Plant Arrangement on faba bean (2017) Mansoura Univ., Vol. 8 (12): which stated that plant height of soybean was increase in the presence of Rhizobium inoculants. Similarly, inter-row spacing was highly significant with respect to plant height. The tallest plant (128.9cm) was recorded at narrowest inter row spacing (30cm) whereas; the shortest plant (109cm) at widest inter row spacing (50cm). This is the fact that under narrow inter-row spacing; there is comparatively low solar radiation, interception through crop canopy compared to wider inter-row spacing. Therefore, high and low interplant competition for light in the narrow and wide spacing respectively could have resulted in such variation in plant height. These results were in agreement with Terefe (2012), Almaz, Meseret and Gezahegn (2009) who were reported taller plants in a narrow spacing because of competition for light compared to the case in wider spacing where light distribution was normal. 4.2.6. Dry Weight of Nodules The result of this study showed that dry weight of nodules was significantly affected by the main effect of bio-fertilizer rate and inter-row spacing (Table 6). However the interaction effect of bio-fertilizer rates and inter-row spacing was not significant. The main effect of bio-fertilizer application and inter-row spacing was highly significant (P ˂ 0.001) affected dry weight of nodules (Appendix table 2). The highest dry weight of nodules (148.7gm) was recorded at the treatment inoculated with the highest rate (0.75kg ha-1) of rhizobium whereas; the lowest (67.3gm) was recorded at control. This variation among the treatments with respect to dry weight of nodules of faba bean might be due to the supply of bio-fertilizer to the crop through symbiotic N2-fixation and changing soil nitrogen to ionic form (NO3-) made available for plant uptake and enables to produce highest dry weight of nodules by initiating vegetative growth. This study is in line with Togay et al., (2008); the observed benefits on faba bean dry weight of nodules by Rhizobium inoculation seem to be to the supply of N to the crop through symbiotic N2-fixation. Sharma et al. (2000) also reported the significant effect of seed inoculation on dry weight of nodules compared to the control treatments. Likewise, the dry weight nodule of faba bean was significantly affected by inter-row spacing at level (P ˂ 0.001). The highest dry weight of nodules (123.8gm) was recorded at widest inter row spacing (50cm) whereas; the lowest (104.5gm) was at narrowest inter-row spacing (30cm). This result might be due to wide spaces between the plants attributed to decreased inter plant competition that leads to increased plant capacity for utilizing the environmental inputs in building great amount of metabolites to be used in developing new tissues and increasing its yield components. Table 6 Interaction effects of bio-fertilizer rate and inter row spacing on plant height, number of leaf per plant and dry weight of nodules at Bonga agricultural research center in Kaffa Zone, in 2019 main cropping season NLP PLH DWN Bio-fertilizer rate (kg ha-1) 0 22d 101.8d 67.3d 0.25 27.7c 111.6c 108c 0.5 34b 127b 132.3b 0.75 43.6a 135a 148.7a LCD(0.05) 5.07 7.03 7.7 Row spacing’s (cm) 30 21c 128.9a 104.5c 40 26.9b 118.8b 114b 50 32.5a 109c 123.8a LSD(0.05) 4.39 6.09 6.67 CV (%) 16.2 6.04 6.9 Means with the same letters in the same column of each factors are not significantly different (P˂0.05); Where; NS＝ means are not significantly different (P˂0.05) probability level; PLH＝ plant height, NLP＝ number of leaf per plant, and DRW＝ dry weight. 4.3. Yield and Yield Components 4.3.1. Number of pods per plant The result obtained from this experiment showed that the number of pods per plant was significantly affected by the main effect of bio-fertilizer rate and inter row spacing (Table 7), whereas; the interaction effect was not significant. The main effect of bio-fertilizer application and inter-row spacing was highly significant P ˂ 0.001 (Appendix table 2). The result of ANOVA revealed that, number of pods per plant was significantly affected by rhizobium inoculation. The highest number of pods per plant (32.9) was recorded at highest bio-fertilizer rate (0.75kg ha-1) inoculation whereas; the lowest (21.6) number of pod per plant was recorded at control. This might be by initiation of Rhizobium Inocula for more vegetative growth and yield increment of faba bean when added by highest rate. This result is in agreement with the work of Malik et al. (2006) who concluded that increased number of pods per plant with bio-fertilizer inoculation in faba bean. Similarly, the research on groundnut by Dereje et al. (2007) showed that plants that were inoculated with rhizobium strain yielded higher number of pods per plant, but un-inoculated yielded lower. Table 7 Interaction effects of bio-fertilizer rate and inter row spacing on number of pod per plant at Bonga agricultural research center in Kaffa Zone, in 2019 main cropping season NPP Bio-fertilizer rate (kg ha-1) 0 21.6d 0.25 25.1c 0.5 29.5b 0.75 32.9a LCD 3.2 Row spacing’s (cm) 30 25.4c 40 30.6b 50 36.5a LSD 4.96 ns CV 14.2 Means with the same letters in the same column of each factors are not significantly different (P˂0.05); NS＝ means are not significantly different (P˂0.05) probability level; where NPP is number of pod per plant Correspondingly, inter-row spacing showed significant differences on the number of pods per plant. Accordingly, the highest number of pod per plant (36.5) was recorded at widest inter-row spacing (50cm) whereas; the lowest number (25.4) was recorded at narrowest inter-row spacing (30cm). This result may be due to wide spaces between the plants attributed to decreased inter plant competition that leads to increased plant capacity for utilizing the environmental inputs in building great amount of metabolites to be used in developing new tissues and increasing its yield components. This result is in line with Abdel (2010), Kubure, Raghavaiah, Hamza (2016) and Shad et al. (2010), Almaz, Meseret and Gezahegn (2009) who were reported a decrease in the number of pods per plant in faba bean due to a reduction in the number of stems per plant at the higher plant densities. 4.3.6. Number of seed per pod The result of ANOVA revealed that, number of seed per pod affected neither by the main effects of bio-fertilizer rate and inter-row spacing nor by their interaction (Table 8). The number of seeds per pod was not significantly (P ˃ 0.05) affected by both application of different bio-fertilizer rate and inter-row spacing (Appendix table 4). This was due to the fact that the number of seeds per pod is mainly under genetic control and can be little affected by the environmental factors. This result was supported by Gebre-Egziabher, Murut, Hadush, Fetien, Abay et.al (2014). Similarly, Abebe and Tolera (2017) reported that number of seed per pod of faba bean was not significantly affect due to fertilizer rate, rhizobium inoculation and lime rate. Table 8 Interaction effects of bio-fertilizer rate and inter row spacing on number of seed per pod at Bonga agricultural research center in Kaffa Zone, in 2019 main cropping season NSP Bio-fertilizer rate (kg ha-1) 0 3.2 0.25 3.1 0.5 3.1 0.75 3.4 LCD 0.4 ns Row spacing’s (cm) 30 3.25 40 3.25 50 3.16 LSD 0.4 ns CV 14.2 Means with the same letters in the same column of each factors are not significantly different (P˂0.05); NS＝ means are not significantly different (P˂0.05) probability level; where NSP is number of seed per pod 4.3.4. Hundred Seeds weight The result obtained from this research showed that hundred seed weight was significantly affected by the main effect of both bio-fertilizer rate and inter-row spacing (Table 9), whereas, the interaction effect was not significant. The main effect of bio-fertilizer inoculation and inter-row spacing was highly significant (P ˂ 0.001) (Appendix table 3). The highest (98.8gm) 100 seed weight was recorded for the highest (0.75kg ha-1) rate of bio-fertilizer inoculation whereas; the lowest (62.9gm) value of 100 grain weight was obtained from the control. This is because larger seeds were yielded by obtaining more nutrients from highest rate of bio-fertilizer inoculation that initiates plant’s nutrient uptake by changing soil N to ionic form (NO3-). This result is in line with the finding of Ali et al (2004) who stated, inoculation of faba bean brought a significant effect on hundred seed weight of chickpea. Table 9 Interaction effects of bio-fertilizer rate and inter row spacing on 100 seed weight at Bonga agricultural research center in Kaffa Zone, in 2019 main cropping season HSW Bio-fertilizer rate (kg ha-1) 0 62.9d 0.25 77.1c 0.5 89.3b 0.75 98.8a LCD 1.92 Row spacing’s (cm) 30 76c 40 82.9b 50 90.2a LSD 6.8 CV 2.32 Means with the same letters in the same column of each factors are not significantly different (P˂0.05); NS＝ means are not significantly different (P˂0.05) probability level; where HSW is 100 seed weight In the same way, inter-row spacing showed significant differences on hundred seed weight. Thus the highest value (90.2gm) of 100 seed weight was recorded at widest (50cm) inter-row spacing whereas; the lowest value (76gm) of 100 seed weight was recorded at narrowest (30cm) inter-row spacing. This is because widely spaced plants get more nutrient, light and water for growth and development with less competition and advanced for more photosynthetic efficiency and this creates the probability of accumulating more dry matter that can be partitioned to the seed during grain filling period. This result is in line with Abdel (2010), Kubure, Raghavaiah and Hamza (2016), who were reported a decrease in the weight of seeds with the higher plant densities. 4.3.1. Grain yield The analysis of variance data revealed that, the main and interaction effects of bio-fertilizer rate and inter-row spacing had highly significant (P˂0.001) variation on grain yield of faba bean (Appendix table 1). The highest grain yield (2540kg ha-1) was recorded from the interaction of highest rate of bio-fertilizer (0.75kg ha-1) and widest inter-row spacing (50cm) which was followed by (2383kg ha-1) obtained from bio-fertilizer rate of (0.75kg ha-1) and inter-row spacing (40cm) and also (2316 kg ha-1) which was obtained from bio-fertilizer rate of (0.75kg ha-1) and inter-row spacing (30cm). There was not significant variation between above treatments, but showed significant difference on the rest treatments (table 10). In contrast the lowest grain yield (1083.3 kg ha-1) was obtained from control and narrowest inter-row spacing (30cm). It might be attributed to highest rate of bio-fertilizer inoculation, the increased availability of N in the soil for uptake by plant roots through fixed N2 and changing soil N to ionic form (NO3-). At widest inter-row spacing, the result might be due to decreased inter plant competition that leads to increased plant capacity for utilizing the environmental inputs in building great amount of metabolites to be used in developing new tissues, increasing its yield components and advanced for more photosynthetic efficiency and this creates the probability of accumulating more dry matter that can be partitioned to the seed during grain filling period. At narrowest spacing, the adverse effect on the yield was noticed which might be due to intense interplant competition, floral abortion and the reduction in yield per plant at control was un-availability of soil nutrient for plant uptake compared than inoculated. Also yield reduction at narrow inter-row spacing (30 cm) could be explained by the canopy development at the early stages of this treatment was insufficient to maximize light interception and photosynthesis. This result coincide with the findings of Sajid et al. (2014), who concluded that the treatments with Rhizobium inoculation gave higher grain yield than those without inoculation. A similar increasing effect of Rhizobium inoculation on grain yield of soybean has also been reported by Abbas, (2014). Also Abebe and Tolera (2014) stated that Rhizobium inoculation produced significantly highest total grain yield than control. Furthermore, this result was in collaboration with Al-Suhaibani et al. (2013) who reported higher seed yield per plant at low plant density. Singh (2002), Kubure, Raghavaiah and Hamza, (2016), Birhanu et al. (2018) also indicated that the yield potential of an individual plant is fully exploited when sown at wider inter row spacing. Table 10 Interaction effects of bio-fertilizer rate and inter row spacing on grain yield at Bonga agricultural research center in Kaffa Zone, in 2019 main cropping season Bio-fertilizer rate (kg ha-1) 0 0.25 0.5 0.75 Row spacing’s (cm) 30 1083.3hij 1450fg 1586.7e 2316.7b 40 1150hi 1483.3f 1916.7d 2383.3ab 50 1215.7h 1550ef 2150c 2540a LSD (0.05) 148.36 CV (%) 11.3 Means with the same letters in the same column of each factors are not significantly different (P˂0.05); Where; NS＝ means are not significantly different (P˂0.05) probability level; GY＝ grain yield 4.3.3. Above ground dry biomass yield The result obtained from this experiment showed that the above ground dry bio-mass yield was significantly affected by the main effect of bio-fertilizer rate and inter row spacing (Table 11). The main effect of biofertlizer application and inter row spacing was highly significant (P ˂ 0.001) (Appendix table 3). On the other hand, the interaction effect of biofertilizer and inter row spacing was statistically, not significant. The highest (7994.4kg ha-1) ADB was recorded at highest bio-fertilizer rate (0.75kg ha-1) whereas; the lowest (3379.1kg ha-1) ADB was recorded at control. This might be by initiation of Rhizobium inocula for more vegetative growth and yield increment of faba bean when added by high rate. Correspondingly, the highest (6041kg ha-1) ADB was recorded at widest (50cm) inter-row spacing whereas; the lowest one (5035kg ha-1) was recorded at narrowest inter-row spacing (30cm). This might be by initiation of wide spacing for more vegetative growth with low competition, more light penetration for photosynthesis made plants to accumulate more assimilates and yield increment of faba bean by wide spacing. Also, this result may be due to wide spaces between the plants attributed to decreased inter plant competition that leads to increased plant capacity for utilizing the environmental inputs in building great amount of metabolites to be used in developing new tissues and increasing its yield components. This result is in line with Almaz, Meseret and Gezahegn (2009) who were found a maximum above ground dry bio-mass of faba bean under wider inter-row spacing. 4.3.4. Harvest index The analysis of variance result revealed that harvest index was significantly affected by the main effect of both bio-fertilizer rate and inter-row spacing (Table 11) whereas; the interaction effect was not significant. The main effect of bio-fertilizer application and inter-row spacing was highly significant (P ˂ 0.001) (Appendix table 3). In this experiment the highest HI (32.8%) was recorded at highest bio-fertilizer rate (0.75kg ha-) whereas; the lowest HI (24.7%) was recorded at control. Because increasing bio-fertilizer rate more initiate the vegetative growth of faba bean plant. This also increases the total dry bio-mass and grain yield of the plant. This growth was directly proportional with harvest index. Also inter-row spacing showed significant effect on HI. Thus, the highest (31.9%) HI was recorded at widest (50cm) inter-row spacing whereas; the lowest (26%) HI was recorded at narrowest (30cm) inter-row spacing. This result may be due to wide spaces between the plants attributed to decreased inter plant competition that leads to increased plant capacity for utilizing the environmental inputs in building great amount of metabolites to be used in developing new tissues and increasing its yield components which were directly proportional with HI. Similar result was reported by Birhanu et al., (2018), Khan et al. (2010) who recorded maximum harvest index at the widest row spacing of chickpea than narrowest row spacing. Table 11 Interaction effects of bio-fertilizer rate and inter row spacing on above ground dry bio-mass yield and harvest index at Bonga agricultural research center in Kaffa Zone, in 2019 main cropping season ADB HI Bio-fertilizer rate (kg ha-1) 0 3379.1d 24.7d 0.25 4505.6c 27.3c 0.5 6193.3b 30b 0.75 7994.4a 32.8a LCD(0.05 574.2 2.2 Row spacing’s (cm) 30 5035c 26c 40 5478.3b 29.5b 50 6041a 31.9a LSD(0.05) 434.3 2.3 CV 4.04 2.79 Means with the same letters in the same column of each factors are not significantly different (P˂0.05); NS＝ means are not significantly different (P˂0.05) probability level; ABD＝ above ground dry bio-mass, HI＝ harvest index 4.4. Partial Budget Analysis Partial budget analysis was calculated by considering the input costs (variable costs) involved and the gross returns obtained from different treatments (Table12). The variable cost also included the labor cost involved for total activities started from land preparation to harvesting. For determining gross returns, prevailing local market price at the harvest of faba bean was used for computation. The net returns was calculated by subtracting the cost of treatment from its gross returns as, RNR＝GR-VC, where RNR＝Relative Net Returns, GR＝Gross Returns & VC＝Variable Cost. Partial budget analysis since the cost of faba bean seeds increases each year, there is a greater need to define optimum plant density to maximize yields and economic return. All un-dominated treatments gave MRR which was greater than the minimum acceptable rate of return (100%). The highest MRR was obtained from the interaction of 0.75kg/ha bio-fertilizer rate with 50 cm inter row-spacing (53850 ETB ha-1) followed by 0.75kg/ha bio-fertilizer rate and 40 cm inter-row spacing (50391.75 ETB ha-1) and 0.75kg/ha bio-fertilizer rate with 30 cm inter-row spacing (48825.75 ETB ha-1). The partial budget, B:C ratio, marginal analysis and minimum rate of return together give the information necessary to arrive at a tentative or candidate recommendation. Therefore, 0.75kg/ha bio-fertilizer rate and 50 cm inter-row spacing gave highest net benefit which was higher than the minimum rate of return (100%). Table 12Partial budget analysis of faba bean with response of bio-fertilizer rate and inter row spacing. TreatmentsGain yield (Kg ha-1)Adjusted grain yield (Kg ha-1)Impute cost (ETB ha-1)Variable cost (ETB ha-1)Total variable cost (ETB ha-1)Gross return (ETB ha-1)Net return (ETB ha-1) Spacing Bio- fertilizer 3001083.3974.9703000300024374.2521374.25 400115010350300030002587522875 5001215.71094.1303000300027353.2524353.25 300.2514501305350275031003262529525 400.251483.31334.973502750310033374.2530274.25 500.2515501395350275031003487531775 300.51586.71428.037002500320035700.7532500.75 400.51916.71725.037002500320043125.7539925.75 500.521501935700250032004837545175 300.752316.72085.0310502250330052125.7548825.75 400.752386.32147.6710502250330053691.7550391.75 500.75254022861050225033005715053850 4.5. Correlation Analysis Correlation analysis between phonological data’s, growth parameters and yield and yield related traits were given in (Table 11). Days to emergency, number of seed per pod and harvest index did not significantly correlated with any of the traits. Number of effective nodules, number of leaf per plant, leaf area index, grain yield and dry weight had a significant positive correlation with each other. Number of pod per plant was significantly correlated with days to 50% flowering (r＝0.7**) number of effective nodules (r＝0.74**), leaf area index (0.8**), dry weight (r＝0.66**) and grain yield (r＝0.63**). Grain yield was positively and significantly correlated with dry weight of nodules (r＝0.56**), days to 50% flowering (r＝0.66**), number of effective nodules (r＝0.63**), leaf area index (r＝0.7**), number of leaf per plant (r＝0.64**), number of pods per plant (r＝0.66**) and above ground bio-mass yield (r＝072**). Here, positive increase in such characters was enhanced the grain yield. These results therefore indicated that the growth and development of one parameter was highly dependent on other. The application of bio-fertilizer with appropriate spacing would improve nutrients uptake of plant, increases N fixation capacity and reduce inter- competition of plants for resource. Increasing number of pods per plant and 100 seed weight were positively correlated with highest yield of the faba bean in this experiment. The current result of Ashenafi and Mekuria (2015) revealed that grain yield of faba bean per hectare was significantly and positively correlated with leaf area index, 100 seed weight, number of pod per plant and dry biomass. Also the finding of Lopez and Bellido et al. (2005) was indicated that LAI was positively associated with low plant population and high grain yield. Furthermore the finding of Tekle and Ibrahim (2015) confirms that correlation between Seed yield, growth and yield components showed a significant positive relation between seed yield ha-1 and plant height, leaf area index and seed yield per plant.
