Wheat is a staple food that provides around 20% of protein and calories consumed worldwide (FAOSTAT, 2015). The demand for wheat is expected to grow by 34 to 60% in 2050 in developing countries (Valin, 2014). The FAO estimates that global commercial production of all types of wheat was 650.9 million metric tons in 2016, harvested from 217.0 million hectares; it is grown on around 4% of the planets agricultural land (FAO, 2017; Sharmin et al., 2021).

Ethiopia is among the biggest cultivators of wheat in Sub-Saharan Africa, with a yearly estimated production of 4.6 million tons on 1.69 million hectares in 2017/18, with productivity of 2.74 tons per hectare (CSA, 2018). Wheat is mainly grown in the mountainous region of Ethiopia, which lies between 6-16° N and 35- 42° E, at altitudes ranging from 1500 to 2800 meters above sea level and with mean minimum temperatures of 6°C to 11°C exclusively under rainfed conditions (Engida, 2 001; MoA, 2012). The average wheat production increased from 1.3 tons ha^-1 in 1994 to 2.74 tons ha^-1 in 2017/18, far below experimental yields of over 5 tons ha^-1 (Gete et al., 2010; Man and Warner, 2015). The typical yield of wheat in SSA is 1.7 tons per hectare (FAO, 2014), which is about 50% lower than the global average. The national wheat productivity in SSA varies across countries. It ranges from 0.7 tons ha^-1 in Burundi to 3.4 tons ha^-1 in Mali.

The main wheat-growing areas of Ethiopia are the highlands of the central, south-eastern, and northwest parts of the country. However, Ethiopias current wheat production is insufficient to meet domestic needs, forcing the country to import 30 to 50% of its wheat demand to fill the gap (Minot et al., 2015). Several factors hindered the yield of wheat crops such as low soil fertility, lack of improved wheat varieties, and lack of improved management practices. The low yield is primarily associated with the depletion of soil fertility due to continuous nutrient uptake of crops, low fertilizer use, and insufficient organic matter application (Kidane, 2015). Continuous cropping and inadequate replacement of nutrients removed in crop harvest or loss through erosion and leaching have been the major causes of soil fertility decline (Hillete et al., 2015 Van Beek et al., 2016). This is particularly evident in the intensively cultivated high-potential areas that are mainly concentrated in the highlands of Ethiopia (Hillete et al., 2015). Nutrient balances in the highlands of Ethiopia, typically the high potential areas for agricultural production are currently exposed to severe soil fertility depletion (Van Beek et al., 2016). In addition, several factors such as improved varieties, adequate cultural practices like balanced fertilization, and management of other biotic and abiotic factors are very important for higher productivity of wheat (Alam and Jahan, 2013).

Yet, agricultural production is increasing which benefits farmers livelihoods and contributes to the food security of the country as a whole, but at the expense of the natural resource base (Van Beek et al., 2016). The yield gap of over 3 tons ha-1, suggests the potential for increasing production through improved soil and crop management practices, particularly increased use of fertilizers and adequate soil fertility maintenance program. Varieties are one of the other major factors that play an important role in producing higher yields of wheat (Alam and Jahan, 2013). Wise use of fertilizers increases crop yield and production; the reverse will lead to a decline in production and ecological imbalance. The fertilizer use efficiency of the crop depends on the performance-specific variety. So cultivar selection plays a very important role in determining grain yield and quality (Brian et al., 2007). In most of the nutrient studies in Ethiopia, more emphasis was given to macronutrients, especially N and P, and micronutrient investigations received little attention. However, Ethiopia is moving from blanket recommendations for fertilizer application rates to recommendations that are customized based on soil type and crop (Nicholas et al., 2015). This is a move towards diversification and inclusion of other types of fertilizers apart from DAP and urea, which have long been the only types of fertilizer imported for grain crops. Different recent studies have shown that elements like N, P, K, S, and Zn levels as well as B and Cu are becoming depleted and deficiency symptoms are being observed on major crops in different areas of the country (ATA, 2013). Most Ethiopian soils are deficient in macronutrients (N, P, K, and S) and micronutrients (Cu, B, and Zn) (EthioSIS, 2014; Sharif et al., 2019). 

Despite the fact that EthioSIS recommends various blended fertilizer types, farmers in the majority of the nation have little knowledge about the effects of multiple fertilizer types and rates other than the general recommendation, which calls for 46 kg of P₂O₅ and 41 kg of nitrogen ha^-1. Therefore, due to lacking of such information particularly on the use of appropriate fertilizer rate and best performing variety in the district, the study was carried out with the ensuing goals:

1. To investigate an optimum agronomic practice of NPSB fertilizer rates and bread wheat varieties on different yield components and grain yield.
2. To identify the most profitable NPSB fertilizer rates and bread wheat variety for wheat production in the study area.

Description of Experimental Site

The study was carried out at Degam District during 2019 main cropping period. The district is located at 124 km North-West of Addis Ababa, and 12 km from Fitche, the capital city of North Shewa Zone, and Oromia Regional State. Girar Jarso surrounds the district to the north-east, Yaya Gulele and Debre Libanos district to the east, Kuyu to the west, Hidabu Abote to the north-west, Jama River to the north, which divides it from the Amhara Region, and Girar Jarso to the north (Fig. 1). Geographically, the district extends from 9°34 to 10°03N latitudes and 38°29 to 38°44E longitudes. The site is located at 9°4948.2′′ North latitude and 38°3343.8″ East longitude with an elevation of 3014 masl. The temperature varied in between 5.6°C to 23°C. The range of yearly rainfall is 800 mm to 1300 mm and the rainfall pattern is bi-modal; a short rainy season (Belg) from February to March, and a primary rainy season (Kiremt) that extends from June to September. Nitosol, also referred to locally as "Biye Dima and Biye Bore," is what defines the research region, and wheat is the prominent grain grown there (Anoynomous, 2017).

Fig. 1: Location map of experimental site. 

Experimental Materials

Plant Materials

Dandaa (Danphe # 1), Hidase (ETBW5795), and Kakaba (Picaflor # 1) were used for the research study. The details of the three varieties are indicated in (Table 1). Those varieties are selected based on yield, disease resistance, farmers acceptance, and popularity character to the district.

Source: MoA, Crop Variety Register (1995-2013) and; MoA, Crop Variety Register, 2016 KARC=Kulumsa Agricultural Research Center, NI=Not indicated 

Fertilizers Materials

NPSB fertilizer (18.9% N, 37.7% P2O5, 6.95% S, and 0.1% B), Triple super phosphate (TSP of 46% P2O5), and urea (46% N) were used as fertilizer sources. 

Experimental Treatments and Research Design

Treatment combinations of three improved varieties (Dandaa, Hidase, and Kakaba) and five NPSB fertilizers rates [0, 50, 100, 150, 200, and NP (64/20) kg ha-1 of local control] with supplementation of 92 kg N for all treatment except blanket recommended NP and the control were used for treatments (Table 2). The experimental field study was arranged with a total of 18 treatments in a factorial combination with a complete block design (RCBD) in three replications. 

Table 2: Combination of Nutrients and fertilizer rates used. 

Selected Physico Chemical Properties of Experimental Soil before Sowing

 Results of research field soil anlysis before sowing for some physico-chemical properties showed the range level and nutrient contents as indicated below before the application of fertilizer to the field (Table 3).

Table 3: Physico-chemical properties of the experimental field soil before sowing. 

Effects of NPSB Fertilizers on Phenological Traits and Growth Parameters

Days to Heading

Days to 50% heading was highly significantly (P < 0.01) affected by the main effect of NPSB fertilizer and variety while the interaction effect did not statistically influence the parameter (P < 0.05) (Table 4). The mean number of days required for 50% panicle heading ranged between 75 days for the variety Kakaba and 83.3 days for the variety Hidase. The earliest days to heading (77.9 days) were recorded with unfertilized plots and the longer days to heading (82.4 days) were recorded with a maximum application of 200 kg ha-1 blended NPSB fertilizer (Table 4). Similarly, the shortest days to panicle heading (72.3 days) on variety Kakaba in unfertilized plot and the longest (85.3 days) on variety Hidase treated with 200 kg of NPSB supplemented by nitrogen fertilizer (Urea) were recorded (Table 4). The longest days to heading were observed for all varieties at 200 kg ha-1 of NPSB supplemented with nitrogen fertilizer (Urea). This difference in days to 50% panicle heading among varieties could be attributed to their genetic factor variability and amount of nutrient management (different rates of NPSB fertilizer supplemented with nitrogen fertilizer) provided for them especially due to fact that nitrogen fertilizer has favored vegetative growth stage and delayed the heading of crops. This result was in line with (Diriba et al., 2019) who reported that time to head of bread wheat was significantly affected by different rates of nitrogen fertilizers. Similarly (Abebe and Hirpa, 2018) reported that NPSZnB fertilizer and sowing methods were significantly affected days to heading by indicating that the application of (macro and micro) and Urea, resulting in a higher rate of nitrogen nutrients which appeared to prolong the vegetative growth stage of wheat and delay time to a heading of the crop. 

Days to Maturity

Both the main and interaction effects influenced 90% of bread wheat physiological maturity highly significant and significant at (P < 0.01) and (P < 0.05) respectively (Table 5). The earliest mean days to maturity (141.0 days) was recorded on variety Kakaba in an unfertilized plot, while the longest (171.0 days) was observed on variety Hidase in plots treated with 200 kg ha-1 of NPSB fertilizer (Table 5). The longest days to maturity were observed for all varieties treated with the maximum rate of NPSB fertilizer supplemented with nitrogen fertilizer (Urea); whereas crops matured early in unfertilized (control) plots. The bread wheat varieties grown under 200 kg NPSB supplemented with nitrogen (Urea) fertilizers matured 11, 11, and 9 days later than crops grown under unfertilized (control) for varieties of Dandaa, Hidase, and Kakaba respectively (Table 5). These variations in days to physiological maturity might be due to the genetic makeup of the varieties and an adequate amount of nutrients that crops have got from NPSB as well as due to in the fact that nitrogen fertilizer promotes greater vegetative development before the beginning of the reproductive phase and thereby delay the maturity. The result is also in line with (Diriba et al., 2019) who reported the longest days to maturity for the variety Wane and Kingbird at maximum kg ha-1 of NPSB fertilizer application with supplementary urea. 

Spike Length (cm)

The main effect of NPSB fertilizer was very highly significant (P < 0.01) on spike length while the main effect of variety and interaction were not significant (Table 4). As the rate of NPSB fertilizer increased there was an increased trend in spike length. The highest rate of 200 kg ha-1 followed by 150 kg ha-1of NPSB fertilizer which were statistically similar to each other resulted in the longest spike length of 8.5cm and 8.3cm respectively; whereas the shortest spike length of 6.7cm was obtained from unfertilized plants (Table 4). This nutrient is available in the formulation of applied NPSB fertilizer as in fact it has a great role in cell division and grain filling thereby attributed to spike length. All the treatments showed an increasing tendency of spike length with increasing NPSB rates supplemented with nitrogen fertilizer. Similarly (Diriba et al., 2019) found that the highest spike length (7.3cm) was recorded from the plot treated with 300 kg ha-1 of NPSB application which improved by 12% as compared to the shortest spike length (6.4cm) obtained from control plot indicating that; use of mixed blended fertilizer along with supplementary nitrogen had significant influence on the spike length. 

Table 4: Main effect of NPSB fertilizers and varieties on days to 50% heading, days to maturity, plant height and spike length of bread wheat. 

Plant Height (cm)

The result of the analysis of variance showed that plant height was very highly significantly (P < 0.01) affected by the main effect of blended NPSB fertilizer supplemented with nitrogen fertilizer and varieties. The interaction effect of both factors was also found highly significant (P < 0.01) for plant height of bread wheat in the study area (Table 5). The mean tallest plant height of 105 cm was observed with the Dandaa variety under the application of 150 kg ha-1 NPSB which is statistically at par with 104.9 cm with the Hidase variety under the application of 200 kg ha-1 NPSB fertilizer. The shortest plant 77.9 cm was recorded with the Dandaa variety under an unfertilized plot (Table 5). The result showed that plant height increased with an increase in blended fertilizer rate supplemented by nitrogen fertilizer (Urea). This might be due to a total increase of nitrogen nutrient fertilizer provided for plants with the increased rate of blended NPSB fertilizer and adequate supply of other nutrients for the growth and development of plants thereby resulting in an increment of plant height. In agreement with this result (Diriba et al., 2019) found highest plant height of 95.5cm for bread wheat at a maximum application of 300 kg ha-1 NPSB fertilizer along with 100 kg ha-1 of urea and the shortest plant height was obtained from the control plots. However different plant height was reported for different bread wheat cultivars with the tallest of 101.97cm for Digalu and 85.87cm for Hidase (Wogene and Agena, 2017) who indicated that the difference was due to variety, nitrogen fertilizer level, and genetic constitution of crops. 

Effects of NPSB fertilizers on Yield Components and Yield

Total Number of Tillers

The main effect of NPSB fertilizer and varieties were highly significant and significantly influenced the total tiller number of bread wheat respectively. However, the interaction effect of two factors was not significant (Table 4). The highest number of total tillers per plant (5.6) was produced from crops treated with 200 kg ha-1 of NPSB supplemented with nitrogen fertilizer while the lowest number (4.4) was recorded from unfertilized plots. A total number of tillers per plant responded differently to NPSB fertilizer with supplementary nitrogen and bread wheat varieties. This might be due to an increase in cell division, and differentiation of growing cells which ultimately results from an adequate provision of sufficient nutrients by crops from blended fertilizer in addition to the genetic makeup of cultivars. In line with this result (Bizuwork and Yibekal, 2020) reported that the highest number of total tillers was produced by plants treated with the highest rate of combined application of (150/115 NPSB/N kg ha-1) fertilizers and the lowest from unfertilized plots which stating that; the synergetic role of the four nutrients played in enhancing growth and development of the crop. 

Number of Productive Tillers per Plant

The result of the analysis of variance showed that the number of productive tillers was significantly (P < 0.05) affected by the main effect of NPSB fertilizer and variety; whereas the productive tillers were highly significantly (P < 0.01) affected by the interaction effect of both factors (Table 5). The maximum number of productive tillers (5.0) was obtained in the Kakaba variety at the application of 200 kg ha-1 of NPSB fertilizer followed by Dandaa variety treated with 150 kg ha-1 of NPSB fertilizer (4.9) although the difference between the two is statistically at par. While the minimum number of productive tillers was 3.7 was obtained from unfertilized plot with Dandaa variety (Table 5).  

Table 5: Interaction effect of NPSB fertilizer and varieties on days to maturity, plant height and number of productive tillers of bread wheat. 

Keys: The means of each feature in the columns and rows that are followed by the same letter or letters do not differ substantially at the 5% level of significance; DM= Days to Maturity, PH= Plant Height, NPT=Number of productive tillers, LSD=Least significance difference at 5% and CV (%) =Coefficient of variations. 

The reason for differences in productive tillers by different levels of NPSB fertilizers might be due to provision of a sufficient supply of essential nutrients and balanced fertilization of crops especially at a time of its emerging, growth and developmental period of crops which results in a higher number of total and productive tillers. The result in this study conformed with (Tilahun and Tamado, 2019) who reported that the highest number of productive tillers was 306.7 m-2 at 150 kg NPS ha-1 supplemented with 92 kg N ha-1 which indicates that the productive tillers were higher by 107.4% over that of control plots.

Number of Kernels per Spike 

The main effect of NPSB fertilizer and variety had highly significant (P < 0.01) effect whereas the interaction effects of both factors are found to be non-significant on number of kernels per spike (Table 6).

Table 6: The main impact of NPSB fertilizer and types on bread wheats above-ground biomass production, thousand kernel weight, and number of kernels per spike. 

Keys: Means with the same letter/s in column are not significantly different at a 5% level of significance; NKS= Number of Kernels per Spike, TKW= Thousand Kernels Weight, ABGB=Above Ground Biomass Yield, LSD=Least significant differences at 5% and CV (%) =Coefficient of variation.  

The highest number of kernels per spike (54.9) was obtained at application of 200 kg NPSB fertilizer with supplementary nitrogen (urea) fertilizer whereas the lowest number of kernels (42.5) was recorded in unfertilized plot. The higher number of kernels per spike under different levels of NPSB fertilizer could be due to an optimum nutrient provision for growth and development of crops from respective sources of applied fertilizers as phosphorus is essential for grain development and boron for grain setting and the difference among bread wheat varieties might be due to genetic variability of crops. So, the synergistic effect of nutrients supply in combination with genetic capacity of cultivar might ultimately result in increases in number of kernels per spike. Similarly the finding of (Bizuwork and Yibekal, 2020) also found that the highest (50.07) and the lowest (34.73) number of kernels per spike at combined application of 150/92 kg NPSB/N ha-1 fertilizer and unfertilized plots respectively; indicating that adequate application of NPSB and N fertilizer supply enables the crop to make rapid growth and to intercept more solar radiation and thus attribute for more number of kernels per spike.

Thousand Kernel Weight 

Thousand kernel weight was very highly significantly (P < 0.01) affected by the main effect of variety. Whereas the main effect of NPSB fertilizer as well as the interaction effect of both factors were found to be non-significant (Table 6). Among varieties the maximum thousand kernels weight of 49.3 g was obtained by Hidase variety while the minimum of 44.4 g was obtained by Kakaba variety (Table 6). These differences in weight of kernels might be due to the genetic capacity of a variety to absorb light and the highest photo assimilate and nutrient use efficiency of the plants other than the nutrient management practices which thereby attributes for more grain filling of the crops and increase in size of seeds as well as weight of crops. Similarly many research findings reported that too much amount of nitrogen fertilizer application had not significant effect on thousand kernels weight. i.e., it has a negative correlation on the parameter. For example, research findings (Bereket et al., 2014; Gerba et al., 2013; Tilahun et al., 2016) reported that the highest thousand kernels weight was obtained from application of 92 kg N ha-1 but, the value decreased as the rate of nitrogen exceeds above this rate. 

Above Ground Biomass Yield

The result of analysis of variance showed that the main effect of fertilizer highly significantly (P < 0.05) affected the above-ground biomass yield. However, the main effects of variety as well as the interaction effect of both factors were found to be non-significant (Table 6). The highest above-ground biomass yield (13.8 tons ha-1) was recorded under 200 kg NPSB ha-1 application followed by 11.8 tons ha-1 under application of 150 kg ha-1 of NPSB fertilizer while; the lowest biomass yield was recorded from unfertilized plot (Table 6). These increases in biomass yield with an increase of NPSB fertilizer might be due to better crop growth rate, maximum accumulation of photo-assimilate, and LAI in parallel with maximum days to maturity by the crop which ultimately results in highest biomass yield. In addition, the highest biomass might also resulted from the synergetic effect of the nutrients which increased uptake of nutrients and root growth favoring better growth of above-ground biomass yield. The present result is in agreement with (Abebe and Hirpa, 2018) who reported that the highest biomass yield under application of 200 kg blended fertilizer and 63.91 kg of urea ha-1 followed by 150 kg blended fertilizer and 82.71 kg of urea ha-1 and the lowest was under no fertilizer application. 

Straw Yield

The analysis of variance showed that the main effect of NPSB fertilizer highly significantly (P < 0.01) affected the straw yield whereas the main effect of variety and interaction effect of both factors were found to be not significant (Table 7). The highest straw yield (9.4 tons ha-1) was obtained at the application of 200 kg ha-1 of NPSB fertilizer with nitrogen supplementation and the lowest straw yield (4.8 tons ha-1) was from the control plot (Table 7).

The highest straw yield from the highest NPSB rate of 200 kg ha-1 might be attributed to the synergetic effect of nutrients as the presence of sulfur increases the nitrogen use efficiency of crops which plays a great role in promoting the vegetative growth and development thus by increasing the straw yield of bread wheat. The result is consistent with that of [28] who reported an increase in straw yield of bread wheat with the increase of NPSB and nitrogen from 150/115 to 100/92 NPSB/N kg ha-1 even if the yield is statically at par with each other. 

Grain Yield

The analysis of variance showed that the main effect of NPSB fertilizer and varieties was highly significantly (P < 0.01) affected the grain yield of bread wheat. However, the interaction effects of the two factors were found to be non-significant (Table 7). The highest grain yield (4549 kg ha-1) was obtained under application of 200 kg of NPSB ha-1 supplemented with nitrogen fertilizer whereas the lowest was under no fertilizer application.

The mean of grain yield was increased with the increment of NPSB from 50 kg ha-1 to 200 kg ha-1. Grain yield obtained at application of 200 kg of NPSB ha-1 with supplementary nitrogen increased grain yield by 38.62% and 54.51% as compared to blanket recommendation (64/20 NP) and control respectively (Table 7). The highest mean grain yield (3351 kg ha-1) was recorded in Hidase variety whereas the lowest was recorded in Kakaba variety which is statically at par with Dandaa variety.

 Table 7: Main effect of NPSB fertilizer and varieties on straw yield, grain yield and harvest index of bread wheat.

Keys: At the 5% level of significance, means that have the same letter in each column do not differ substantially; SY= Straw Yield, GY= Grain Yield, HI= Harvest Index, LSD=Least significant differences at 5% and CV (%) =Coefficient of variation. 

The main and final ultimate goal in every crop production is achievement of maximum economic profit in yield, which is a complex function of environmental condition, response of yield components and yield of the genetic potential of varieties, management practice, and the interaction of all of these factors. The differences in grain yield under different rates of NPSB fertilizers and varieties might be due to a sufficient supply of balanced nutrients from NPSB fertilizer for crops both in quantity and quality from respective increased rates of blended fertilizer for growth and development of crops thus by which attributes for increment of grain yield. This result was in agreement with the finding of (Bizuwork and Yibekal, 2020) who reported that the highest mean grain yield of 5666 kg ha-1 was obtained at combined application of 150 kg of NPSB and 92 kg N ha-1, whereas the lowest mean grain yield of 1960 kg ha-1 was obtained from unfertilized plots. 

Harvest Index

The analysis of variance for harvest index showed that main effect of NPSB fertilizer rates, varieties, and their interaction effects were found to be statically non-significant (Table 7). 

Analysis of Correlation of Parameters

Days to heading and maturity, number of total tillers and number of productive tillers, number of kernels per spike and thousand kernels weight, above-ground biomass yield and straw yield, grain yield and harvest index; and above-ground biomass yield and grain yield showed strongly significant positive correlation. Furthermore, maturity date and number of kernels per spike, number of total tillers and number of kernels per spike, and plant height with spike length were significantly positive correlations. Among those parameters considered; number of total tillers and thousand kernels weight, straw yield and grain yield as well as above-ground biomass yield and harvest index had a negatively significant correlation (Table 8).

Table 8: Correlation coefficient of various parameters of bread wheat. 

Keys: DH= Days to heading, DM= Days to maturity, NTT= Number of Total Tillers, NPT= Number of Productive Tillers, PH= Plant Height, SL= Spike Length, NKS= Number of Kernels per Spike, TKW= Thousand Kernels Weight, AGBM= Above Ground Biomass, SY=Straw Yield, GY=Grain Yield and HI=Harvest Index. 

Partial Budget and Economic Analysis

In the present study, the prices for purchasing the NPSB fertilizer, Urea, bread wheat, and labor cost for fertilizer application were considered variable costs whereas other costs were constant for each treatment. To recommend the present finding in the study area, it is necessary to estimate the minimum rate of return acceptable to producers in the recommendation domain. It is quite evident from the result presented in Table 9, that the partial budget analysis showed that mean highest net benefit of (97993) Birr ha-1 was obtained from variety Hidase that received 200 kg NPSB ha-1 with nitrogen fertilizer supplementation. However, the lowest mean net benefits of (39582) Birr ha-1 were obtained from the unfertilized treatment with the variety Dandaa.

Table 9: Partial budget and economic analysis of the effect of NPSB fertilizer rates supplemented with nitrogen fertilizer on bread wheat varieties at Degam District.  

Keys: NPSB= Nitrogen, Phosphorous, Sulfur and Boron; NP= Nitrogen and Phosphorus; AGY= Adjusted Grain Yield; ASY= Adjusted Straw Yield; TGB= Total Gross Benefit; TVC= Total Variable Cost; NB= net Benefit; ΔNB= Change in Net Benefit; MRR= Marginal Rate of Return; ETB= Ethiopian Birr per hectare and D= Dominated.

The experimental research study indicated that application of balanced and sufficient soil nutrient management with high yielder improved variety is one of the best agronomic practice for increasing yield components and yield of bread wheat. Accordingly, analysis of the result revealed that 50% days to heading, total number of tillers, number of kernel per spike and grain yield were highly significantly affected by main effect of both varieties and NPSB fertilizers; Whereas spike length, above ground biomass yield and straw yield were significantly affected by the main effect of NPSB fertilizer rate while thousand kernels weight was affected only by the main effect of variety. However, the analysis of result study indicated that as days to 90% maturity, plant height and number of productive tillers were significantly affected by the interaction effect of both factors. The highest, maximum grain yield (4549 kg ha-1), above ground biomass yield (13.8 tons ha-1), straw yield (9.4 tons ha-1), number of kernels per spike (54.9), total number of tillers (5.6), number of productive tillers (4.7), the longest days to heading (82.4 days), physiological maturity (163.6 days), highest number of kernels per spike (54.9) and highest plant height (102.4 cm) were recorded at the maximum NPSB rate application (200 kg ha-1) supplemented with nitrogen fertilizers. While the lowest and minimum result for all parameters were recorded from unfertilized plot except for thousand kernels weight and harvest index. The result of economic analysis showed that combined production of 200 kg ha-1 blended NPSB fertilizer with Hidase variety gave economic benefit of 97993ETB ha-1 with the acceptable marginal rate of return (640.14%). Similarly, the grain yield also showed that statistically the highest grain yield (4979 kg ha-1) was obtained from the combined application of 200 kg ha-1 of NPSB fertilizer with Hidase variety. Therefore, it could be concluded that application of 200 kg NPSB in supplement of 92 kg N ha-1 fertilizer with Hidase variety was temporarily the best producing alternatives and economically profitability and with acceptable grain yield of bread wheat production at the study area. Finally it is advisable to undertake further research across soil types, season and locations involving others best performing cultivar to draw sound recommendation on a wider scale and for longer duration and variable cropping systems.

A.F.B.; L.A. designed the study. A.; and A.N.M. performed the methodology. A.R.I carried out the data analysis. D.Y.A composed the manuscript. All the authors checked and approved the final manuscript.

The authors acknowledged Oromia Agricultural Research Institute for funding experimental research. The authors also extend their gratitude acknowledgment to Fitche Agricultural Research Center for its financial support and providing working facility. The authors also express their special thanks to all staff members of Fitche Agricultural Research Center for their unreserved assistance in setting up, planting, collecting the data and maintaining the field experiments.

The authors declared that they have no any financial or persona conflicts of interest that can affect the report of this research paper.