Effects of nitrogen fertilizer rate and timing of application on yield components and yield of bread wheat (Triticum aestivum L.) in Gombora District, Hadiya Zone, Central Ethiopia

J. Biodiv. & Environ. Sci. Haile et al. RESEARCH PAPER OPEN ACCESS Effects of nitrogen fertilizer rate and timing of application on yield components and yield of bread wheat ( Triticum aestivum L.) in Gombora District, Hadiya Zone, Central Ethiopia Mathewos Haile, Sate Sahle, Tagesse Abera* Collage of Agriculture, Department of Plant Science, Wachemo University, Ethiopia Key words: Inorganic N fertilizer, Bread wheat, Grain yield DOI: http://dx.doi.org/10.12692/jbes/27.1.82-89 [ Published: July 18, 2025 ] ABSTRACT Bread wheat productivity is constrained by incorrect use of inorganic nitrogen rate and time of application. The objectives of this study were to determine economically feasible rate and time of nitrogen for wheat. Five levels of nitrogen (0, 23, 46, 69 and 92 kg ha-1) and three time (1/2 at the time of sowing and 1/2 at mid tillering stage, 1/3 at the time of sowing and 2/3 at mid tillering stage and 2/3 at time of sowing and 1/3 at mid tillering stage) were tested by using a randomized complete block design with three replicates. SAS software was used to analysis of variance which revealed almost all parameters were significantly (p ≤ 0.01) affected by the main effects of nitrogen rate and its application time, except time of N had no significant effect on thousand kernels weight, straw yield and harvest index, while, their interaction effects had significant effect on grain yield, above ground dry biomass, spike length and plant height. The highest net benefit was obtained from the 92 kg/ha N with 1/3 at the time of seed sowing and 2/3 at mid-tillering stage, which produced high grain yields with the best profitability. Therefore, this treatment could be recommended as best for maximum seed yield of wheat. However, the experiment was carried out only in one location for one cropping season, additional studies at different locations for at least three years or seasons should be conducted. *Corresponding Author: Tagesse Abera  [email protected] Journal of Biodiversity and Environmental Sciences | JBES ISSN: 2220-6663 (Print); 2222-3045 (Online) Website: https://www.innspub.net E-mail contact: [email protected] Vol. 27, Issue: 1, p. 82-89, 2025 J. Biodiv. & Environ. Sci. Vol. 27, Issue: 1, p. 82-89, 2025 83 Haile et al. Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net INTRODUCTION Bread wheat (Triticum aestivum L.) is the most widely grown cereal grain in the world, and it is a member of the Poaceae family (Clayton et al., 2015). It is a key industrial and food grain that is traded internationally and ranks second among the world's most important cereal crops after rice (Asadallah, 2014). Wheat is a strategic commodity in SubSaharan African countries as it generates farm income and improves food security (Amentae et al., 2017). It is widely cultivated in the middle to highaltitude zones (1,800 - 2,400 m) and the total wheat area farmed and total production, Ethiopia is one of Africa's top wheat producers (CSA, 2012). But, the production of wheat is tremendously of a subsistence nature and is dominated by the country’s numerous smallholder farmers that cultivate more wheat for consumption and less for the market. The farmers in most parts of the country in general and in the study area in particular have limited information on the impact of different types and rates of fertilizers except blanket recommendation of nitrogen (46 kg N ha-1) and phosphorus (46 kg P2O5 ha-1) moreover, essentially nitrogen fertilizer required for successful plant growth and good productivity. The average productivity of wheat at national level, Central Ethiopia and study area are 3.04, 2.92, 2.89 ton ha-1, respectively (CSA, 2020) and this is low compared to the world’s average yield of 3.4 tones ha-1 (FAO, 2019). Low soil fertility is one among the major factors limiting maize production and productivity in the lowland areas of the country in general and in Central Ethiopia in particular, where depletion of macro-nutrient and micro nutrient, inappropriate fertilizer rate and application time are the most significant constraints limiting wheat production in Ethiopia including the study area (Demeke and Antonio, 2013). Techniques that increase the yield of the wheat crop on low soil fertility especially, low nitrogen soil by the application of appropriate rates and time of application are essential to sustain productivity and avoid soil fertility constraints. Therefore, the objectives of the study were on the effect of N fertilizer application rate and time of application on yield components and yield of bread wheat. MATERIALS AND METHODS Description of the study area An experiment was conducted at Wera Keble Farmers Training Centre in 2022, which is located in Gombora District, Hadiya Zone, Central Ethiopia, during the main cropping season. The site is located on geographic coordinates of 7O 33′ N 7O 37′ N latitude and 37O 35′ E to 37O 40′ E longitudes at altitude of this District ranges from 1400 to 2400 meters above sea level. The annual rainfall varies from 600 to 2200mm, and the annual mean temperatures also vary from 1525°C (GDFEDO, 2022). Soil sampling and analysis Soil sample was taken from experimental plots to determine some physical and chemical properties. The prepared soil sample was composited to one sample and air dried, ground, and sieved using 2mm sieve. Then, these composited soil sample was analyzed for the determination of soil pH, organic carbon (OC), total nitrogen (N), available phosphorus (av. P), and cation exchange capacity (CEC) according to the standard laboratory procedures at wachemo university, soil and water analysis laboratory. Organic carbon content was determined by the wet digestion method of Walkley and Black (1934) and total N by the semi-micro-Kjeldahl method of Bremner and Breitenbeck (1983). CEC of the soil was determined by the neutral ammonium acetate (CH3COONH4) saturation method (Rhoades, 1982). The av. P was extracted with a sodium bicarbonate solution at pH 8.5 following the procedure described by Olsen and Khasawneh (1980). The pH of the soil was measured potentiometrically in the supernatant suspension of a 1:2.5 soil: water mixture by using a pH meter (Van Reeuwijk, 1992). Experimental materials and design Bread wheat variety 'kakaba' was used which was released by Kulumsa Agricultural Research Centre (KARC) in 2012. The treatments consisted of five levels of nitrogen (0, 23, 46, 69 and 92 N kg ha-1) and J. Biodiv. & Environ. Sci. Vol. 27, Issue: 1, p. 82-89, 2025 84 Haile et al. Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net three times of N application 1/2 at the time of sowing with seed and 1/2 at mid tillering, 1/3 at the time of sowing and 2/3 at mid tillering stage, 2/3 at the time of sowing and 1/3 at mid tillering stage. The experiment was laid in a randomized complete block design with three replications. The gross size of each plot was 2.5m x 3m consisting of ten rows and the distance between adjacent plots and blocks was 0.5 m and 1m apart respectively thus the net plot size was 2m x2m. The outermost row on both sides of each plot was considered a border row and was not used for data collection to avoid border effects. Data collection and analysis Plant height (cm): It was measured in cent meter from the soil surface to the tip of the spike (awns excluded) from 10 randomly pre-tagged plants from the net plot area at physiological maturity and their average was computed. Spike length (cm): it was measured from the bottom of the spike to the tip of the spike excluding the awns from 10 randomly tagged spikes from the net plot. Number of total tillers: It was determined from two rows per net plot at physiological maturity by counting the number of tillers. Number of productive tillers: It was determined at maturity by counting all spikes bearing kernels from two predemarked rows per plot at physiological maturity. Thousand kernels weight (g): It was determined based on the weight of 1000 kernels sampled from the grain yield of each net plot by counting using electronic seed counter and weighed with sensitive balance. Then the weight was adjusted to 12.5 % moisture content. Aboveground dry biomass (kg): It was determined after the crop harvested from the net plot area after sun drying to a constant weight and converted to kilogram per hectare. Grain yield (kg): It was recorded after harvesting and threshing the seed yield from net plot area. The yield was adjusted to 12% moisture content. Finally, yield per plot was converted per hectare basis and the average yield was reported in kg ha-1. Grain yield kg ha-1 at 12.5% moisture bas=Yield obtained (kg ha-1) (100-%MC)/100-12.5%. Adjusted grain yield= (100-%MC) × unadjusted grain yield100-12.5%. Straw yield was obtained as the difference of the total above ground dry biomass and grain yield and expressed in kg ha-1. Harvest index (%): Harvest index was calculated as ratio of grain yield per plot to total aboveground dry biomass yield per plot expressed as percent. RESULTS AND DISCUSSION Physicochemical properties of the experimental soil Textural class of soil is clay loam; the soil pH is moderately acidic, organic carbon content of the experimental site was 2.8% which was medium according to the rating of Tekalign (1991). Mengel and Kirkby (1996) reported optimum pH range of 4.1 to 7.4 for wheat production. Total N content of 0.1% which is considered very low, medium in av. P mg/kg1, low in CECcmol+/kg (Table 1). Table 1. Physicochemical properties of the experimental soil Soil parameters Physical properties Value Rating Reference Clay (%) 38 High Hazelton and Murphy (2007) Sand (%) 28 Moderate Hazelton and Murphy (2007) Silt (%) 24 Moderate Hazelton and Murphy (2007) pH(1:2.5 H2O) 5.9 Moderately acidic Tekalign (1991) N (%) 0.15 Poor Tekalign (1991) OC (%) 2.8 Medium Landon (1991) CECcmol+/kg 15 Low Landon (1991) A. P(ppm) 10.4 Medium Tisdale (2002) Yield and yield parameters of maize The analysis of variance (ANOVA) showed that the main effects of nitrogen rate, time of application and their interactions had a significant (p 0.01) effect on both plant height and spike length. The tallest mean plant height (99.00cm) was recorded from the nitrogen rate of 92 kg ha-1), in 1/3 of the dose at sowing and 2/3 at mid tillering stage, whereas, the shortest mean plant height J. Biodiv. & Environ. Sci. Vol. 27, Issue: 1, p. 82-89, 2025 85 Haile et al. Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net (67.83cm) was recorded from 0 kg N with (1/3 at sowing and 2/3 at mid-tillering stage (Table 2). Similarly, the longest mean spike length (9.47cm) was recorded from the nitrogen rate of 92 kg ha-1), in 1/3 of the dose at sowing and 2/3 at mid tillering stage, whereas, the shortest mean spike length (6.03cm) was recorded from 0 kg N with (1/3 at sowing and 2/3 at mid-tillering stage. Plant height generally increased with an increase in the rate and frequency of N application and the shortest plants were recorded from unfertilized plot. These results were in line with Khan et al. (2000) who reported that increasing nitrogen rates increased the wheat plant height. Similary, Amsal et al. (2000) observed a positive and linear response to applied N fertilizer to plant height in the central highlands of Ethiopia. According to Rahmatullah et al. (2007) and Amjed et al. (2011) who reported that spike length increased significantly with increased application of nitrogen. Table 2. Plant height and spike length of bread wheat as influenced by the interaction of N rate and time of N application N rate (kg ha-1) Timing of application Plant height(cm) Spike length(cm) T1 T2 T3 T1 T2 T3 0 69.00hi 68.17i 67.83i 6.50fg 6.03f 6.43g 23 73.17g 76.20fg 72.67gh 7.63e 7.67e 7.50e 46 78.5ef 88.43bc 81.67de 8.40cd 8.60c 8.30d 69 87.80c 92.17b 85.33cd 8.60c 9.07b 8.47cd 92 89.33bc 99.00a 92.00b 9.00b 9.47a 8.57c LSD(0.05) 4.12 0.25 CV (%) 9.03 11.86 Parameter means followed by the same letter within a column are not significantly different at 5% level of significance according to Tukey Tests; LSD (5%) = least significant difference at 5% level and CV = coefficient of variation, T1= N application of 1/2 at sowing and 1/2 at mid-tillering; T2= N application of 1/3 at sowing and 2/3 at mid-tillering; T3= N application of 2/3rd at sowing, 1/3rd at mid-tillering. Table 3. Number of total and productive tillers of bread wheat as influenced by main effects of N rate and time of N applications N rate (kg ha-1) Number of total tillers Number of productive tillers 0 126e 85.00d 23 152.89d 119.22c 46 193.53c 166.11a 69 246.67b 146.11b 92 266.78a 126.11c LSD (0.05) 8.04 19.55 N application time T1 199.00b 127.33ab T2 207.53a 139.33a T3 185.07c 118.87b LSD (0.05) 6.22 15.14 CV (%) 12.22 15.76 Parameter means followed by the same letter within a column are not significantly different at 5% level of significance according to Tukey Tests; LSD (5%) = least significant difference at 5% level and CV = coefficient of variation, T1= N application of 1/2 at sowing and 1/2 at mid-tillering; T2= N application of 1/3 at sowing and 2/3 at mid-tillering; T3= N application of 2/3rd at sowing, 1/3rd at mid-tillering. Number of total and productive tillers The both number of total and productive tillers per meter square were significantly (p<0.05) affected by main effects of N fertilizer rate and time of applications but, not significantly interaction effect of the two factors. The maximum (266.78) and minimum (126.11) mean total number of tillers were recorded from the application of the highest rates of J. Biodiv. & Environ. Sci. Vol. 27, Issue: 1, p. 82-89, 2025 86 Haile et al. Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net N rate (92 kg ha-1) and control treatments, respectively (Table 3). This result is in line with Hameed et al. (2003) who observed that increasing nitrogen application significantly increased the number of tillers per meter square and Genene (2003) who reported higher tillering and maximum survival percentage of tillers with increasing N application in bread wheat. Also the maximum (166.11) and minimum (85.00) mean productive number of tillers were recorded from the application of the rate of N (46 kg ha-1) and control, respectively. This result agrees with those of Prystupa et al. (2004), who reported that the number of productive tillers was significantly affected by nitrogen application. Aboveground dry biomass Analysis of variance indicated that the aboveground dry biomass had respond significantly to the effects of N rate, N time of applications as well as interaction effect. The highest mean of above ground dry biomass (8920 kg ha-1) was obtained from the interaction of 92 kg N ha-1 with application time of 1/3 at the time of sowing and the rest 2/3 at mid tillering stage whereas, the lowest mean of above ground dry biomass (3460 kg ha-1) was also recorded from the interaction of 0 kg N ha-1 with application time of 2/3 at the time of sowing and the remain 1/3 at mid tillering stage (Table 4). The increase in above-ground dry biomass with a higher N rate might be due to improved N availability for bread wheat vegetative growth as well as appropriate fertilizer supply and assimilation in meristematic tissue which facilitated tillering and overall plant growth. These results are in conformity with the results of Jasemi et al. (2014) reported that vegetative growth and biological yield have a dependence on the consumption of chemical fertilizers. Similarly, Bekalu and Mamo (2016) also reported that increasing N rate from 23 to 69 kg ha-1 increased the above ground dry biomass of wheat by about 22.6%. Table 4. Aboveground dry biomass and grain yield of bread wheat as influenced by the interaction of N rate and time of N application N rate (kg ha-1) Timing of application Aboveground dry biomass (kg ha-1) Grain yield (kg ha-1) T1 T2 T3 T1 T2 T3 0 3833.3i 3800.0i 3460.0i 1633.3f 1616.7f 1626.7f 23 4383.3h 4716.7gh 4866.7g 1900.0ef 2063.3ef 1900.0ef 46 5633.3f 6616.7e 6466.7e 2600.0d 3416.7b 3016.7c 69 7138.3d 7583.3cd 7333.3d 3383.3b 3733.3a 3296.7bc 92 7813.3bc 8920.0a 8146.7b 3420.0b 4016.7a 3760.0a LSD(0.05) 460.77 315.4 CV (%) 14 8.83 Parameter means followed by the same letter within a column are not significantly different at 5% level of significance according to Tukey Tests; LSD (5%) = least significant difference at 5% level and CV = coefficient of variation, T1= N application of 1/2 at sowing and 1/2 at mid-tillering; T2= N application of 1/3 at sowing and 2/3 at mid-tillering; T3= N application of 2/3rd at sowing, 1/3rd at mid-tillering. Grain yield Analysis of variance for grain yield indicated significant effects of N application rate, time and interaction with both N rate and time of applications. The highest mean grain yield (4016.7 kg ha-1) was recorded from the interaction of 92 N kg ha-1 with its application time of 1/3 at the time of sowing and 2/3 at mid tillering stage, while the lowest mean (1616.7 kg ha-1) was obtained from the interaction of the 0 N kg ha-1 with its application time of 1/3 of N at the time of sowing and the rest 2/3 of N at mid tillering stage (Table 4). This result showed that there is high potential to increase bread wheat yield through increased application of nitrogen fertilizer rates. Generally, wheat grain yield consistently increased as the rate of applied N increased to the highest level of N and the grain yields recorded due to each successive rate of N J. Biodiv. & Environ. Sci. Vol. 27, Issue: 1, p. 82-89, 2025 87 Haile et al. Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net were significantly different. The results obtained from this study in lined with the research findings of many previous works, Haile et al. (2012), Getachew (2004) who reported significant increases in grain yields of bread wheat with increasing application levels of N fertilizer. Straw yield The results of analysis of variance revealed that the straw yield of bread wheat was significantly (p 0.01) affected by the N fertilizer rate. However, its application time and the interaction of the two factors were not significant. The highest (4561.1 kg ha-1) and the lowest (2072.2 kg ha-1) straw yield were recorded from the highest N rate of 92 kg ha-1 and control treatments, respectively (Table 5). This result is in line with Gul et al. (2012), who reported that higher nitrogen application has a greater contribution to higher straw yield production as compared to control treatment. Table 5. Straw yield harvest index of bread wheat as influenced by main effects of N rate and time of N applications N rate (kg ha-1) Straw yield( kg ha-1) Harvest index (%) 0 2072.2e 44.26bc 23 2701.1d 42.08c 46 3227.8c 47.99a 69 3863.9b 47.36ab 92 4561.1a 45.03abc LSD (0.05) 260.39 3.37 CV (%) 8.21 7.71 Parameter means followed by the same letter within a column are not significantly different at 5% level of significance according to Tukey Tests; LSD (5%) = least significant difference at 5% level and CV = coefficient of variation, T1= N application of 1/2 at sowing and 1/2 at mid-tillering; T2= N application of 1/3 at sowing and 2/3 at mid-tillering; T3= N application of 2/3rd at sowing, 1/3rd at mid-tillering. Harvest index (%) The main effect of N rate had a highly significant (p<0.01) influence on harvest index; but the main effect of N application time as well as its interaction with N application rate did not influence this. The highest (47.99%) and the lowest (42.06%) of harvest index were recorded from the nitrogen rate of 46 kg ha-1 and 23 kg ha-1, respectively (Table 5). This result is aligned with that of Sakatu (2017), who reported the maximum harvest index (0.43) at a nitrogen level of 190 kg N ha-1 while a minimum harvest index (0.35) was recorded from control. Similarly, Muhammed et al. (2012) who reported the highest harvest index (36.17%) was obtained from a treatment of 150 kg N ha-1 and the lowest harvest index (31.53%) was recorded from control. CONCLUSION The low productivity of bread wheat in the study area is diminished by inappropriate use of nitrogen rate and its time of application. Thus, increased usage of N fertilizer is considered to be a primary means of increasing wheat yield in this area. In view of this, a field experiment was conducted to determine the effect of N rate and time of application on yield components and yield of wheat; and to determine economically feasible rate and time of N application. The results of the field experiment revealed that all parameters were significantly affected by main effects of nitrogen rate and its application time, except time of N had no significant effect on thousand kernels weight, straw yield and harvest index, although, their interaction effects had significant effect on grain yield, above ground dry biomass, spike length and plant height. In general, the highest net benefit was obtained from the 92 N kg ha-1 with 1/3 at the time of seed sowing and 2/3 at mid-tillering, which produced high grain yield with the best profitability and this treatment could be recommended. However, the experiment was carried out only in one location for one cropping season, additional studies should be conducted. J. Biodiv. & Environ. Sci. Vol. 27, Issue: 1, p. 82-89, 2025 88 Haile et al. Journal of Biodiversity and Environmental Sciences | JBES Website: https://www.innspub.net ACKNOWLEDGEMENTS I would like to acknowledge my Advisors for their interest in the work, frequent supervision with genuine comments, and reviewing, their guidance, encouragement, support and advices starting from proposal preparation to Thesis write up. My special thanks go to the Gombora Woreda Agriculture and Natural resource Office for providing me the research site I used for the experiment. Further, the magnificent support and contribution of all my families and friends are profoundly acknowledged which accentuated during my entire study. REFERENCES Amentae TK, Kaso HT, Gebresenbet G, Ljungberg D. 2017. Exploring wheat value chain focusing on market performance, post-harvest loss, and supply chain management in Ethiopia: The case of Arsi to Finfinnee market chain. Amsal T, Tanner DG, Chanyalew M. 2000. 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