African Journal of
Plant Science

  • Abbreviation: Afr. J. Plant Sci.
  • Language: English
  • ISSN: 1996-0824
  • DOI: 10.5897/AJPS
  • Start Year: 2007
  • Published Articles: 785

Full Length Research Paper

Comparative effects of newly introduced and adopted chemical N and P fertilizers on wheat growth, yield and yield components

Tarekegn Yoseph
  • Tarekegn Yoseph
  • School of Plant and Horticultural Sciences, College of Agriculture, Hawassa University, P. O. Box 05, Ethiopia.
  • Google Scholar
Tewodros Ayalew
  • Tewodros Ayalew
  • School of Plant and Horticultural Sciences, College of Agriculture, Hawassa University, P. O. Box 05, Ethiopia.
  • Google Scholar
Xinzhu Li
  • Xinzhu Li
  • Kingenta Ecological Engineering Group Co., Ltd, Linyi, P. R. China.
  • Google Scholar
He Jigang
  • He Jigang
  • Kingenta Ecological Engineering Group Co., Ltd, Linyi, P. R. China.
  • Google Scholar
Tingshuai Yan
  • Tingshuai Yan
  • Kingenta Ecological Engineering Group Co., Ltd, Linyi, P. R. China.
  • Google Scholar

  •  Received: 03 January 2018
  •  Accepted: 05 April 2018
  •  Published: 31 May 2018


Soil fertility decline is one of the prime factors contributing to low productivity of crops and food insecurity in Ethiopia. To alleviate this problem and achieve maximum yield, identifying suitable agronomic inputs such as N and P types in wheat production systems is very important. The aim of this study was therefore, to estimate the effects of different N and P fertilizer types and rates on growth, yield and yield components of wheat at Hawassa, southern Ethiopia. For this purpose a treatments consisting of seven N and P sources (F1=Control, F2=Local recommended Urea 100 kg ha-1 and DAP 100 kg ha-1, F3=Urea 100 kg ha-1 and Enhanced DAP 100 kg ha-1, F4=Black Urea 103.3 kg ha-1and Enhanced DAP 100 kg ha-1, F5=100 kg ha-1 Enhanced Urea-1 and Enhanced DAP 100 kg ha-1, F6=Enhanced Urea-2 100 kg ha-1and Enhanced DAP 100 kg ha-1 and F7=Compound fertilizer 256.25 kg ha-1) were studied using a randomized complete block design with three replications. Analysis of the data recorded from the combined application of different N and P treatments revealed that maximum grain yield (3.67 t.ha-1) was obtained from the plots which were supplied with Enhanced Urea-2 and Enhanced DAP at the rate of 100-100 kg ha-1. It can be concluded from the result that wheat crop performed better when fertilized with this treatment. Therefore, the application of enhanced DAP 100 kg ha-1 with Enhanced Urea-2 100 kg ha-1 is recommended to optimize the growth and yield performance of wheat.

Key words: Enhanced DAP (diammonium phosphate), enhanced urea, growth, yield components, wheat.



Ethiopia is one of the largest cereal crop producers in Africa, and the second largest wheat producer in sub-Saharan Africa, following South Africa (GAIN, 2012). Most wheat production in the country comes from small holder farmers. Wheat is primarily grown in the Southeast central and Northwest parts of the country. Small amount is produced in the rest of the North and South regions. At the national level currently 1,453,817 ha of land is covered by bread and durum wheat and over 25,376,39.8 tones are produced from this land annually (Crop VarietyRegister, 2010). Nutritionally, the crop provides an excellent source of carbohydrates, proteins (20 to 25%), fates (20 to 25%), vitamins such as:- thiamine, niacin, pantothenic acid, riboflavin and folate and minerals such as iron, magnesium, zinc and phosphate (Kumar et al., 2011). In addition to this, inclusion of wheat in the daily diet has several health benefits and can be used for different liver ailments, to help prevent cancer, tooth decay, skin problems such as eczema and psoriasis ( It is also claimed to reduce hair from greying, improves digestion, reduces high blood pressure as it enhances the capillaries, support the growth of lactobacilli and can remove heavy metals from the body (Meyerowitz, 1999). It is found to improve hematological toxicity related to chemotherapy in breast cancer patients, it reduces the frequency and requirement of blood transfusions in thalassemia major (Singh et al., 2010; Arya and Kumar, 2011). Despite, the importance of wheat and its many useful characteristics, its production is low in Ethiopia. Its average yield for example is about 2.1 t ha-1 which is much lower than the potential yield of 5.0 t ha-1 (Hailu, 1991; MoA, 2012; 2011). The low yields of wheat is partly attributed by biological and environmental factors, such as frequent occurrence of drought, declining of soil fertility, poor agronomic practice, limited and suboptimal use of production inputs, insufficient technology generation, lack of credit facilities, poor seed quality and weak supply, disease, insect, pests and weeds particularly, Striga (Spielman et al., 2011; MoA, 2012; 2011).
The most important constraint that threatens wheat production in Ethiopia is poor soil fertility (CSA, 2012). Particularly, the deficiency of nitrogen (N) and phosphorus (P) is the main factor that severely reduces the growth and yield of most cereals including wheat. In order to alleviate the soil fertility problem in the area, the Bureau of Agriculture and Natural Resources of the Region has introduced chemical fertilizers particularly DAP (diammonium phosphate) and urea fertilizers in each district of the zone. However the fertilizer types and the rate which is being used by farmers are very limited and recommended in blanket basis throughout the region. Fertilizer is the most important agricultural input which contributes markedly towards final grain yield of wheat and to exploit the inherited potential of a cultivar. N is an essential component of deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and proteins, the building blocks of life (Harrison, 2010). All organisms require N to live and grow. Even though N is among the most abundant elements on earth, it is the critical limiting element for growth of most plants due to its unavailability (Graham and Vance, 2000). Several investigators (Khursheed and Mahammad, 2015; Solomon and Anjulo, 2017) reported a beneficial effect of N application on wheat. They reported that plant height, numbers of tillers, spike length, number of spikelet’s and grains per spike, grain and straw yields of wheat increased with increasing N to the optimum level. P has great importance in plant nutrition. It involves in the processes of energy transformations, genetic inheritance, protein synthesis and cell division. Moreover P enhances root development and strengthening of straw, affects flowering, fruiting, seed formation and crop maturation (Gebreslassie and Demoz, 2016). Many researches reported the beneficial effect of P fertilization on growth and grain yield of cereal crops including wheat (Harfe, 2017). Kaleem et al. (2009) has also shown that the application of P fertilizer to wheat crop has significantly increased the plant height, number of tillers plant-1, straw and grain yield over the control treatment. So far, little information is available on the wheat growth and yield enhancing effects of N and P fertilization in Ethiopia in general and in Southern region in particular. Therefore, the present study was aimed to evaluate the effects of newly introduced and adopted chemical N and P fertilizers on wheat growth, yield and yield components.


Site description
The field experiment was conducted in Hawassa University research field which is located at 273 km Southwest of the capital Addis Ababa in the South Nation Nationalities and People Regional State (SNNPR). The site is located at 70 4’N latitude and 380 31’E longitude and at an altitude of 1969 m.a.s.l. The soil type of the area is sandy loam with a pH of 7.9. The average annual rainfall of the area is 800 to 1100 mm, with the average annual maximum, minimum and mean temperature of 27, 12, and 20°C, respectively (Agro-Meteorology Department, Hawassa Agricultural Research Center).
Source of inputs, plant material, treatments, experimental design and procedures
Except treatment F2 (locally used Urea and DAP fertilizers) all fertilizers were imported and obtained from the Kingenta Fertilizer Company of China. These different fertilizers were known to enhance growth and yield performances of cereals including wheat in different provinces of China. A high yielding wheat variety Jonsen, which is adapted to the agro-ecology of the area, was used for the study. Seeds were obtained from the Hawassa Agricultural Research Centre, Hawassa, Ethiopia. The variety was chosen based on its high yield ability, acceptability by farmers and seed availability. The treatments consisted of seven N and P types (F1=Control, F2=Local recommended Urea 100 kg ha-1 and DAP 100 kg ha-1, F3= Urea 100 kg ha-1 and Enhanced DAP 100 kg ha-1, F4=Black Urea 103. 3 kg ha-1and Enhanced DAP 100 kg ha-1, F5=Enhanced Urea-1 100 kg ha-1and Enhanced DAP 100 kg ha-1, F6=Enhanced Urea-2 100 kg ha-1and Enhanced DAP 100 kg ha-1 and F7=Compound fertilizer 256.25 kg ha-1. The size of each plot was 3 m × 4 m (12 m2) and the distance between adjacent plots and blocks kept at 1.0 m and 1.0 m apart, respectively. Seeds were sown by drilling using a row spacing of 20 cm. The experiment was laid out using a factorial randomized complete block design (RCBD) with three replicate plots. Weeding was done manually by hoe at two weeks after seedling emergence, and three weeks later. Finally, wheat plants were harvested from the three central rows to determine yield and yield components of wheat on 27 September, 2017.
Data collected
Plant height
This was measured at mid-head setting stage by measuring ten randomly selected plants from ground level to the top of the spike termination node and averaged for a single reading.
Root length
The same sample was taken and root length was measured through measuring tape and averaged for a single mean root length in each experimental unit.
Number of tiller per plant
Tiller number was counted by ten randomly selected plants and values averaged for a single reading.
Shoot dry weight per plant
This was measured at harvest by measuring ten randomly selected plants and averaged for a single reading.
Spike length
This was measured from ten randomly selected spikes at harvest from each plot through measuring tape.
1000-grains weight (g)
This was measured at harvest and weighed on top loading digital balance and its averaged was taken as 1000-grain weight.
Grain and biological yield
Grain and biological yield were recorded at three central rows harvested in each experimental unit. Subsequent sample was oven dried at 70°C for maximum 48 h to estimate dry matter yield.
Harvest index
This was calculated as a ratio of grain yield to total biological yield.
Statistical analysis
The obtained data were subjected to analysis of variance (ANOVA) using the General Linear Model (GLM) of the Statistical Analysis System (SAS, 2002) version 9.0. Mean separation was done using Least Significant Difference (LSD) test at 5% probability level. Plants grown in non-N and P amended soil served as control.
Soil sampling and analysis
Before planting soil samples were randomly taken from the experimental site at a depth of 30 cm using an auger and the samples were mixed thoroughly to produce one representative composite sample of 1 kg. The composite soil sample was air-dried and ground to pass 2 and 0.5 mm (for total N) sieves. Then the processed sample was analyzed following standard laboratory procedures as outlined by Sahlemedhin and Taye (2000) at Hawassa University College of Agriculture soil laboratory. Organic carbon (OC) and total N contents of the soil were determined following the wet combustion method of Walkley and Black, and wet digestion procedure of Kjeldahl method, respectively. The available P content of the soil was determined following Olsen method. Soil texture was analyzed by Bouyoucos hydrometer method. The cations exchange capacity (CEC) of the soil was determined following the 1N ammonium acetate (pH 7) method. The pH (1:2.5 solid: liquid ratio) of the soils was measured in water using pH meter with glass-calomel combination electrode.


Soil physico-chemical properties
The results of pre-planting soil analysis revealed that, the experimental soil is sandy loam in texture (38.0% sand, 24.0% silt and 38.0% clay). Soil texture is a fundamental soil property which in practice the farmer can do little to modify. It is also closely related to the water-holding capacity of soils, since loams and clays hold more water than sandy soils (Brady, 2002). Thus, the experimental soil has good water holding capacity, which creates a suitable growing media for cereal crops. Wheat is characteristically grown on such soils which holds sufficient amount of residual soil moisture. The soil was slightly acidic in reaction with the pH (H2O 1:2.5) value of 6.4, which is within the range of optimum soil pH for cereal production including wheat (Havlin et al., 1999). The total N, available P, OC and CEC of the soil before planting were 0.15%, 7.6 mg kg-1, 5.9%, and 24.3 cmol (+) kg-1, respectively (Table 1). According to Havlin et al. (1999) soils are classified depending on their total N content in percentage (%), as very low (<0.1), low (0.1 to 0.15), medium (0.15 to 0.25), and high (>0.25). Thus, the soil of the study site has low total N content. Olsen et al. (1954) classified available P content of the range <5 as very low, 5 to 15 as low, 15 to 25 as medium and >25 mg kg-1 as high. According to Landon (1991) the soil organic carbon content ranges from 1 to 2, 2 to 4, and 4 to 6% are rated as low, medium and high, respectively. Thus, the OC content of the soil is considered as low before planting. The CEC ranges from 5 to 15, 15 to 25 and 25 to 40 cmol kg-1 are rated as low, medium and high, respectively. Based on these ratings, the cation exchange capacity (24.3 cmol kg-1) before planting of the experimental field was in the medium range. Generally the soil analysis result indicated that, the soil is nutrient deficient to support the potential crop production. This may be associated with poor farm management practices and continuous cropping with little or no fertilizers input which resulted in a decline in soil fertility. It may be because of this that growth, yield and yield components of wheat responded to supplied N and P fertilizers in the present experiment.
Plant height
Different types of N and P fertilizer had highly significant effects on the plant height (Table 2). The highest mean plant height was obtained from plots supplied with treatment F7 (compound fertilizer) (46.3 cm) which was significantly different from the other treatments, except F6 (Table 3). The lowest plant height (34.8 cm) was recorded from the treatment F1 (control), which was significantly inferior to all other treatments. Plant height increment of 87.5% was obtained from F7 as compared to the F2 (locally used urea and DAP) fertilizers. The reasons for the increased plant height under different N fertilizer types could be due to the increased vegetative growth with applied N. In line with this, Razaq et al. (2017) obtained increased plant height of wheat fertilized with N. Similarly, Abera (2013) reported that applied N at different rates resulted in increased vegetative growth period of maize that increases photosynthetic assimilate production and its partitioning to stems that might have favorable impacts on heights of maize. On the other hands, increase in plant height due to application of P might be attributed to more availability of nutrients due to increased levels of P, which exerted beneficial effect on vegetative growth of plant. Increase in plant height with supplied N and P levels has also been observed by Khan et al. (2014). This may be due to increased root growth, which strengthened the stem against lodging during prolonged vegetative growth. Furthermore, Khalil et al. (1988) and Umeri et al. (2016) reported that marked increase in plant height of maize due to combined application of NP fertilizers.

Root length plant-1
Statistical analysis of data revealed significant effects of different N and P fertilizer types on root length plant-1 (Table 2). Maximum mean root length plant-1 was obtained from the F6 (11.9 cm) and it was significantly different from all other treatments except treatment F7 which in turn was not significantly different from treatments F2, F4 and F5 (Table 3). The lowest root length plant-1 (6.3) was recorded from F1 (control). All other N and P fertilizer treatments increased root length plant-1 to a variable extent over the control, indicating that the need of N and P sources for better root growth in nutrient deficient soils. The increased root growth beneficially increases the potential soil water and nutrient reservoirs of the growing crops (Gajri et al., 1989). Studies in wheat have reported that applications of N fertilize, typically increase water use efficiency in both irrigated (Hussain and Al-Jaloud, 1995) and rain-fed systems (Belford et al., 1987). P also plays an important role in lateral root morphology and root branching and influences not only root development, but also the availability of N nutrients (Lopez-Bucio et al., 2003; Jin et al., 2005). Similar to these results Razaq et al. (2017) reported an increased root growth due to supplied N and P fertilizers.
Number of tillers plant-1
Analysis of variance on tiller number plant-1 revealed the existence of highly significant difference among the combined application of N and P fertilizers (Table 2). Maximum mean number of tillers plant-1 was obtained from the treatment F6 and it was significantly at par with treatments F3 and F4 (Table 3). The lowest tiller number per plant (5.1) was recorded from the control treatment. This study is supported by Tabar (2013) where application of N and P fertilizers found to favor tillering in rice. Wakene et al. (2014) also reported an increased number of fertile tillers, total biomass and straw yield of barley due to addition of P.
Shoot dry weight plant-1
Plant growth measured as shoot dry matter was significantly (P<0.001) affected by combined application of N and P fertilizers (Table 2). The highest (11.1 g plant-1) shoot dry matter was recorded from treatment F6, but statistically parity between this treatment and treatments F7, F4 and F5 (Table 3). However, the lowest shoot dry weight (8.2 g) was recorded from treatment F1 (control). This is in agreement with the findings of Elgharably (2011) who stated an increased shoot dry matter of wheat due to individual and combined application of N and P in a saline sandy loam soil.
Spike length plant-1
Application of different types of N and P fertilizers significantly increased spike length (Table 4). The highest spike length (14.5 cm) was recorded from the application of treatment F6 (Enhanced Urea-2 100 kg ha-1and Enhanced DAP 100 kg ha-1). However, statistically significant variation in spike length was not detected between this treatment and treatment F7 (Table 5). However, these treatments were significantly higher over the control. These results are similar with the findings of Kaleem et al. (2009) who reported maximum NP fertilizer utilization recorded the highest yield effects due to maximum accumulation of photosynthates. The length of spikelets per spike plays a paramount role towards the grain per spike and final yield of wheat crop (Shahzad et al., 2007).

1000- grains weight
The data given in Table-4 showed that there were highly significant (P<0.01) variations in fertilized and non-fertilized treatments for 1000-grain weight. Maximum 1000 grain weight (55.7 g) was obtained from plots treated with enhanced urea and DAP at 100-100 kg ha-1. However, the minimum (30.7 g) 1000-grain weight was obtained from the treatment where NP was not supplied (Table 5). All the other treatments fall in between these treatments. The relatively heavier seed weight in N and P treated plots was obtained possibly due to increased assimilates production and photosynthesis efficiency at the grain filling stage of the plant because of improved plant mineral nutrition. Furthermore, it may be due to greater contribution of N and P by producing healthy grains which have well filled and bigger grains than the control treatments. These results are similar with the findings of Khan et al. (2014) who reported improved seed weight due to combined application of NP fertilizers on maize.
Grain yield
The fertilizer treatments significantly affected the grain yield of wheat (Table 4). The yield was highest in the F6 treatment, followed by treatments F5, F7, F3 and F2, respectively. In the F1 (control), the yields of wheat was significantly lower than those other treatments. On the other hands, it was visually observed that wheat plants in the control plots were very thin with small spike size, short and light in color. Whereas, plants in the N and P fertilized plots had thick and strong stems, green in color, large spike size. The increased grain yield due to applied N and P might be attributed to low nutrient contents of study site (Table 1). Thus, the availability of these nutrients enables the plant to develop more extensive root system to extract water and nutrients, from more depth. This could enhance the plants to produce more assimilates, which was reflected in higher biomass (Gobarah et al., 2006). Furthermore, the increases in yield due to P fertilizer may be attributed to the activation of metabolic process, where its role in building phospholipids and nucleic acid is known (Gentili and Huss-Danell, 2003). This result is in agreement with the findings of Bereket et al. (2014) who reported that application of N and P fertilizers increase grain yield of wheat. These results do not agree with the findings of Kulhare et al. (1991) who studied NP doses effect on late sown wheat crop and reported that application of NP, does not increased wheat yield.
Biological yield
Application of different types of N and P fertilizer had highly significant effects on the biological yield of wheat (Table 4). Highest biological yield of (5.81 t. ha-1) was obtained from treatment F6 but was not statistically different than the treatments F4 and F5 (Table 5). The lowest biological yield (2.67 t ha-1) was recorded from the control, which was significantly inferior to all other treatments. Greater plant height, yield and yield components might have contributed to the differences observed in biological yield among the different types of N and P application. These results are in confirmation with the findings of Islam and Baten (1987) and Patel et al. (1991) who recorded maximum biological yield by the application of optimum N and P fertilizer rates when compared to the treatments receiving no N and P fertilizers.
Harvest index
Harvest index was influenced significantly by different N and P fertilizers treatments (Table 4). The highest harvest index (0.63) was recorded in F6 and it was at par with all the treatments except the control. The lowest harvest index (0.34) was recorded from the control treatment (Table 5). The physiological ability of a crop plant to convert proportion of dry matter into economic yield is measured in terms of harvest index. The results indicated that adequate supply of N and P fertilizers in combination enhanced dry matter partitioning in favor of grain showing a greater harvest index. This is illustrated by the lower harvest indices observed under the treatments that received no N and P treatments. These results corroborate the findings of Mesfin and Zemach (2015), who reported similar results.


In this study it was found that, the combined application of N and P fertilizers had significant effect on growth, yield and yield components of wheat. Among the treatments studied, Enhanced Urea-2 and enhanced DAP 100 kg ha-1, respectively gave greater grain yield. Furthermore, this treatment enhanced growth and yield related parameters compared to the control treatment. Thus, it is possible to recommend the combined application of Enhanced Urea-2 and Enhanced DAP at the rate of 100 kg ha-1 each to attain greater grain yield of wheat in the study area. However, it is advisable to undertake further research across soil type, years and locations to draw sound recommendation on a wider scale.



The authors have not declared any conflict of interests.


The authors are grateful to Kingenta Fertilizer Company for supplying enhanced N and P fertilizers and for financial support to conduct this experiment.



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