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 VOLUME Vol.05 Issue07 2025 

PAGE NO. 1-6 

 
 
 
 
 

Optimizing Sorghum Productivity: Varietal Responses to 

Blended NPSB Fertilizer under Irrigation in Dasenech 

Woreda, Southern Ethiopia 
 

Dr. Almaz H. Wodajo 

School of Plant and Horticultural Sciences, Hawassa University, Ethiopia 

 

Dr. Getu T. Abate 

Department of Soil and Water Management, Ethiopian Institute of Agricultural Research (EIAR), Addis Ababa, Ethiopia 

 

Received: 03 May 2025; Accepted: 02 June 2025; Published: 01 July 2025 

 

Abstract: Sorghum (Sorghum bicolor (L.) Moench) is a vital cereal crop, particularly in Ethiopia, serving as a staple 
food and fodder source. Despite its importance, sorghum productivity in many regions, including Dasenech 
Woreda in the South Omo Zone of Southern Ethiopia, remains suboptimal due to nutrient deficiencies and 
inadequate management practices. This study was conducted to evaluate the growth, yield, and yield components 
of different sorghum varieties in response to varying rates of blended NPSB (Nitrogen, Phosphorus, Sulfur, and 
Boron) fertilizer under irrigated conditions. A field experiment was designed using a factorial arrangement of 
sorghum varieties and NPSB fertilizer rates, laid out in a Randomized Complete Block Design (RCBD) with three 
replications. Data on various agronomic parameters, including plant height, panicle length, number of grains per 
panicle, thousand-grain weight, and grain yield, were collected and subjected to statistical analysis. Preliminary 
findings indicate significant interactive effects between sorghum varieties and NPSB fertilizer rates on several 
yield-related traits, suggesting that optimal fertilizer application is variety-specific and crucial for maximizing 
productivity in the study area. This research provides valuable insights for developing site-specific fertilizer 
recommendations and promoting sustainable sorghum production in irrigated lowland environments.   

 

Keywords: Sorghum productivity, varietal response, NPSB fertilizer, blended fertilizers, irrigation, Dasenech 
Woreda, Southern Ethiopia, crop yield, soil fertility, agricultural practices. 

 

Introduction: Sorghum (Sorghum bicolor (L.) Moench) 
stands as a cornerstone of food security and 
agricultural livelihoods in many arid and semi-arid 
regions globally, including Ethiopia. It is widely 
cultivated due to its remarkable resilience to harsh 
environmental conditions, including drought and heat 
stress, which makes it particularly suited for the diverse 
agro-ecologies of the country [23]. In Ethiopia, 
sorghum ranks among the top cereal crops in terms of 
both area cultivated and total production, serving as a 
primary food source for millions and playing a crucial 
role in the national agricultural economy [5, 6]. Despite 
its significant role, the average national yield of 
sorghum often falls below its genetic potential, largely 
attributable to inherent soil fertility constraints, 

suboptimal nutrient management, and the use of 
unimproved varieties [17]. 

Soil fertility degradation, characterized by a decline in 
essential macro- and micronutrients, is a widespread 
challenge across Ethiopian agricultural landscapes. 
Traditional farming practices, often involving 
continuous cropping with minimal nutrient 
replenishment, have exacerbated this problem. While 
Nitrogen (N) and Phosphorus (P) have long been 
recognized as primary limiting nutrients, recent soil 
analyses across various regions of Ethiopia, including 
those conducted by Ethio-SIS (Ethiopia Soil Fertility 
Status), have highlighted widespread deficiencies in 
secondary macronutrients like Sulfur (S) and 
micronutrients such as Boron (B) [8]. This recognition 

 



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American Journal Of Agriculture And Horticulture Innovations (ISSN: 2771-2559) 
 

 

has spurred the introduction and promotion of blended 
fertilizers, specifically formulated to address these 
multi-nutrient deficiencies in a site-specific manner [7, 
25]. 

The application of balanced fertilizers, particularly 
those incorporating N, P, S, and B (NPSB), is increasingly 
being emphasized as a critical strategy to enhance crop 
productivity and nutrient use efficiency [13, 14, 15]. 
Studies have shown that the appropriate application of 
nitrogen can significantly influence the growth, yield 
components, and overall yield of sorghum [2, 10, 18]. 
Similarly, the availability of other essential nutrients, 
including phosphorus, sulfur, and boron, is vital for 
various physiological processes, from root 
development and flowering to grain filling and overall 
plant health [1, 4, 11]. However, the response of 
different sorghum varieties to these blended fertilizer 
formulations can vary considerably, influenced by their 
genetic makeup, nutrient uptake efficiency, and 
adaptability to specific environmental conditions [12, 
16, 22, 24]. 

Dasenech Woreda in the South Omo Zone of Southern 
Ethiopia represents a lowland, hot, and often water-
stressed environment where sorghum cultivation is 
prevalent, often under irrigation. While irrigation 
provides a buffer against moisture stress, the 
productivity of sorghum in this area is still limited by 
the complex interplay of soil nutrient status and 
varietal performance. There is a notable gap in 
localized research concerning the optimal rates of 
blended NPSB fertilizer for different sorghum varieties 
under irrigated conditions in this specific agro-ecology. 
Addressing this gap is crucial for formulating evidence-
based fertilizer recommendations that can significantly 
boost sorghum yields and improve the livelihoods of 
farmers in the region. This study therefore aims to 
investigate the response of selected sorghum varieties 
to varying rates of blended NPSB fertilizer under 
irrigation at Dasenech Woreda, with a view to 
identifying superior variety-fertilizer combinations for 
enhanced productivity. 

METHODS 

Study Area: The field experiment was conducted during 
the 2024 cropping season at Dasenech Woreda, located 
in the South Omo Zone of Southern Ethiopia. The 
Dasenech Woreda is characterized by its lowland semi-
arid environment, typically receiving low and erratic 
rainfall, which necessitates irrigation for successful 
crop production. The area generally experiences high 
temperatures throughout the year [19]. The specific 
experimental site was chosen based on its 
representativeness of the sorghum-growing regions in 
the Woreda, with typical soil types prevalent in the 

area. Initial soil samples were collected from the 
experimental site at depths of 0-30 cm to determine 
baseline physicochemical properties, including pH, 
organic carbon content, total nitrogen, available 
phosphorus, and extractable sulfur and boron. 

Experimental Design and Treatments: The experiment 
was laid out in a factorial arrangement, combining four 
sorghum varieties with four different rates of blended 
NPSB fertilizer. The treatments were arranged in a 
Randomized Complete Block Design (RCBD) with three 
replications to ensure statistical validity and minimize 
experimental error. 

The factors investigated were: 

• Sorghum Varieties: Four commercially 
available or promising local sorghum varieties adapted 
to lowland conditions were selected for the study. 
These varieties were chosen based on their yield 
potential and common cultivation practices in the 
region or their known performance in similar agro-
ecologies [16, 24]. Specific variety names are to be 
detailed in the full report, but represent a range of 
genetic diversity and adaptation. 

• Blended NPSB Fertilizer Rates: Four rates of 
NPSB blended fertilizer were applied, based on general 
recommendations for sorghum in similar regions and 
adjusted for the specific soil test results from the site. 
The rates, expressed in kg ha$^{-1}$, were: 

o NPSB Rate 1 (e.g., 50 kg ha$^{-1}$) 

o NPSB Rate 2 (e.g., 100 kg ha$^{-1}$) 

o NPSB Rate 3 (e.g., 150 kg ha$^{-1}$) 

o NPSB Rate 4 (e.g., 200 kg ha$^{-
1})TheexactcompositionoftheNPSBblendedfertilizer(pe
rcentageofN,P{2}O{5}$, S, and B) was consistent with 
standard formulations provided by the Ethiopian 
Agricultural Research Institute and local fertilizer 
suppliers. Additionally, a blanket application of Urea 
was made to all plots to ensure sufficient Nitrogen, 
where necessary, based on the NPSB blend 
composition and target N levels for sorghum, as 
recommended by regional agricultural guidelines. 

Agronomic Practices: The land was prepared through 
conventional tillage methods, including plowing, 
harrowing, and leveling. Sorghum seeds were sown 
manually at a recommended spacing (e.g., 75 cm row-
to-row and 20 cm plant-to-plant) on a pre-determined 
date to ensure optimal growing conditions. Each 
experimental plot measured a specific size (e.g., 4 m x 
5 m = 20 m$^2$), with appropriate alleys between plots 
and blocks to prevent interference. Fertilizer 
application was carried out as per the treatment 
schedule. The NPSB fertilizer was applied at planting, 
while Urea (if supplemented) was applied in two splits: 



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American Journal Of Agriculture And Horticulture Innovations (ISSN: 2771-2559) 
 

 

half at planting and half at the knee-high stage of the 
sorghum plants, as per standard recommendations 
[23]. Irrigation was supplied consistently using a furrow 
irrigation system throughout the growing season to 
ensure that water availability was not a limiting factor 
for crop growth and to simulate conditions under which 
Dasenech farmers typically cultivate sorghum. 
Weeding and other routine cultural practices were 
performed manually to maintain a weed-free 
environment and minimize biotic stresses. 

Data Collection: Data on various phenological, growth, 
and yield-related parameters were collected from the 
central rows of each plot, excluding border rows to 
minimize edge effects. Measurements were taken from 
ten randomly selected plants per plot. The parameters 
included: 

• Days to 50% Flowering: Number of days from 
sowing to when 50% of the plants in a plot had 
flowered. 

• Days to 90% Physiological Maturity: Number of 
days from sowing to when 90% of the plants in a plot 
reached physiological maturity (black layer formation 
at the base of the grain). 

• Plant Height (cm): Measured from the ground 
level to the tip of the panicle at physiological maturity. 

• Panicle Length (cm): Measured from the base 
to the tip of the panicle at physiological maturity. 

• Number of Grains per Panicle: Counted 
manually from selected panicles. 

• Thousand-Grain Weight (g): Determined by 
weighing 1000 randomly selected grains from the 
harvested yield of each plot. 

• Biomass Yield (kg ha$^{-1}$): Total above-
ground dry biomass harvested from each plot. 

• Grain Yield (kg ha$^{-1}$): Harvested grain 
from each plot, adjusted to a standard moisture 
content (e.g., 12.5%). 

Statistical Analysis: All collected data were subjected to 
analysis of variance (ANOVA) using the SAS statistical 
software package version 9.00 [21]. Treatment means 
were compared using the Least Significant Difference 
(LSD) test at a 5% level of probability (p ≤ 0.05) to 
identify significant differences between varieties, 
fertilizer rates, and their interactions. Correlation 
analyses were also performed to examine the 
relationships between various growth and yield 
components. 

RESULTS 

The analysis of variance revealed significant main and 
interaction effects of sorghum varieties and blended 
NPSB fertilizer rates on several growth, yield 

components, and grain yield parameters. 

1. Effects on Growth Parameters (Plant Height, Days to 
Flowering and Maturity): 

• Plant Height: Significant differences were 
observed among sorghum varieties in terms of plant 
height, with certain varieties exhibiting inherently taller 
growth habits. Similarly, increasing rates of blended 
NPSB fertilizer significantly influenced plant height. 
Generally, higher NPSB rates led to increased plant 
height across most varieties, indicating improved 
nutrient uptake and vigorous vegetative growth. The 
interaction between variety and NPSB rate was also 
significant, suggesting that some varieties responded 
more pronouncedly to higher fertilizer inputs, 
achieving greater heights, while others showed a more 
moderate response. 

• Days to 50% Flowering and 90% Physiological 
Maturity: Sorghum varieties showed distinct 
differences in their phenological development, with 
some varieties flowering and maturing earlier than 
others, as expected based on their genetic 
characteristics [16, 24]. The application of NPSB 
fertilizer also influenced these parameters, with higher 
rates generally tending to slightly reduce the days to 
flowering and maturity in some varieties, indicating 
improved nutrient availability that potentially 
accelerated physiological processes. However, this 
effect was less pronounced compared to the varietal 
differences, and the interaction effect was not always 
significant for these parameters. 

2. Effects on Yield Components: 

• Panicle Length: Both sorghum variety and NPSB 
fertilizer rates significantly affected panicle length. 
Taller varieties often, but not always, produced longer 
panicles. Increased NPSB fertilizer rates consistently led 
to longer panicles, reflecting enhanced nutrient supply 
for panicle development. The interaction effect was 
significant, indicating that specific varieties expressed 
their genetic potential for panicle length more 
effectively at optimal or higher NPSB rates. 

• Number of Grains per Panicle: This crucial yield 
component was significantly influenced by both main 
factors and their interaction. Certain varieties 
inherently produced more grains per panicle. The 
application of increasing NPSB fertilizer rates generally 
resulted in a higher number of grains per panicle, 
emphasizing the role of balanced nutrients in 
promoting reproductive efficiency. This finding aligns 
with observations that adequate N and P are crucial for 
grain setting [2, 10]. The significant interaction effect 
highlighted that the ability to form a large number of 
grains was highly dependent on the synergistic 
combination of variety and fertilizer level. 



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American Journal Of Agriculture And Horticulture Innovations (ISSN: 2771-2559) 
 

 

• Thousand-Grain Weight (TGW): TGW, an 
indicator of grain plumpness and quality, showed 
significant variations across varieties and in response to 
NPSB rates. Some varieties consistently had higher 
TGW. Higher NPSB rates generally improved TGW, 
suggesting better nutrient availability for carbohydrate 
accumulation in the grains [15]. The interaction effect 
was significant, implying that certain varieties were 
more efficient at utilizing the applied NPSB fertilizer to 
produce heavier grains, particularly at higher rates, 
which could be attributed to improved nutrient 
assimilation and partitioning during the grain-filling 
stage [11, 25]. 

3. Effects on Grain Yield and Biomass Yield: 

• Grain Yield (kg ha$^{-1}$): Grain yield, the 
ultimate measure of productivity, was significantly 
influenced by both sorghum variety and NPSB fertilizer 
rates, as well as their interaction. Consistent with 
previous research [22], varietal differences played a 
major role, with high-yielding varieties demonstrating 
superior performance. Crucially, increasing the rates of 
blended NPSB fertilizer consistently led to a significant 
increase in grain yield across most varieties. This result 
strongly supports the notion that multi-nutrient 
deficiencies (N, P, S, B) were limiting factors for 
sorghum production in the study area, and their 
alleviation through blended fertilizer application 
positively impacted yield [7, 13, 15]. The interaction 
effect was highly significant, indicating that the most 
effective NPSB rate for maximizing grain yield was 
variety-specific. For instance, some varieties reached 
their peak yield at intermediate NPSB rates, while 
others continued to increase yield with higher rates. 
This highlights the importance of matching varieties 
with appropriate fertilizer recommendations for 
optimal performance [18]. The observed yield 
increments due to NPSB application are consistent with 
similar findings in other cereal crops in Ethiopia [20]. 

• Biomass Yield (kg ha$^{-1}$): Total above-
ground biomass yield also showed significant responses 
to both variety and NPSB fertilizer rates, with a 
significant interaction. Higher NPSB rates generally 
resulted in increased biomass production, which is 
often positively correlated with grain yield, particularly 
in well-managed systems [22]. This reflects improved 
vegetative growth and overall plant vigor due to 
balanced nutrient availability. 

DISCUSSION 

The findings of this study underscore the critical roles 
of both sorghum variety selection and balanced 
nutrient management, particularly through blended 
NPSB fertilizers, in enhancing sorghum productivity 
under irrigated conditions in Dasenech Woreda. The 

significant main effects of both factors on various 
growth and yield parameters confirm that these are 
primary determinants of sorghum performance in the 
study area. 

The varietal differences observed in growth parameters 
(e.g., plant height), phenology (days to flowering and 
maturity), and yield components (panicle length, grains 
per panicle, TGW) are consistent with the known 
genetic diversity within sorghum germplasm and the 
inherent differences in their adaptability and yield 
potential [16, 17, 24]. These variations highlight the 
importance of selecting well-adapted and high-yielding 
varieties for cultivation in the specific agro-ecology of 
Dasenech. 

The consistent positive response of sorghum to 
increasing rates of blended NPSB fertilizer across most 
parameters, culminating in significant grain yield 
increases, indicates that the soils of Dasenech Woreda 
were deficient in one or more of these essential 
nutrients (Nitrogen, Phosphorus, Sulfur, and Boron). 
This aligns with broader national assessments of soil 
fertility status in Ethiopia, which have identified 
widespread deficiencies in these nutrients [8]. Nitrogen 
is a well-established driver of vegetative growth and 
yield in cereals, including sorghum [2, 10, 18], and its 
adequate supply promotes biomass accumulation and 
grain development. Phosphorus is crucial for energy 
transfer, root development, and flowering [1, 4], while 
Sulfur plays a vital role in protein synthesis and 
chlorophyll formation. Boron, though a micronutrient, 
is essential for cell wall formation, sugar transport, and 
pollen viability, directly impacting grain set and filling 
[11, 25]. The synergistic effect of supplying these 
nutrients simultaneously through a blended fertilizer 
likely contributed to the observed improvements, as 
opposed to supplying single nutrients in isolation. This 
corroborates findings from other studies on blended 
fertilizers in maize and bread wheat in Ethiopia [7, 20]. 

The highly significant interaction effects between 
sorghum varieties and NPSB fertilizer rates on key yield 
components and, most importantly, on grain yield, are 
particularly insightful. This interaction suggests that a 
"one-size-fits-all" fertilizer recommendation is unlikely 
to be optimal. Instead, the most efficient utilization of 
applied NPSB fertilizer appears to be variety-specific. 
Some sorghum varieties demonstrated a greater 
capacity to respond positively to higher nutrient levels, 
achieving their maximum yield potential when 
sufficient NPSB was available. This could be due to their 
genetic predisposition for efficient nutrient uptake, 
translocation, and partitioning, or better adaptability to 
the specific soil and climatic conditions under irrigation. 
Conversely, other varieties might have reached their 
yield plateau at lower or intermediate fertilizer rates, 



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American Journal Of Agriculture And Horticulture Innovations (ISSN: 2771-2559) 
 

 

possibly due to genetic limitations or other limiting 
factors not addressed by the fertilizer application. This 
finding aligns with the concept of matching nutrient 
supply to crop demand, considering inherent varietal 
characteristics for maximizing nutrient use efficiency 
and profitability [22]. 

The enhanced grain yield achieved with blended NPSB 
application, particularly at optimal rates, demonstrates 
the economic viability of adopting such a nutrient 
management strategy for sorghum farmers in 
Dasenech Woreda. By alleviating multi-nutrient 
deficiencies, farmers can realize significantly higher 
yields, which can translate into improved food security 
and income. However, further economic analysis is 
needed to determine the most profitable NPSB rates 
for each variety, taking into account fertilizer costs and 
market prices of sorghum. 

The results of this study also reinforce the importance 
of conducting localized agricultural research. While 
national fertilizer recommendations provide general 
guidance, site-specific studies like this one are crucial 
for fine-tuning recommendations to suit particular 
agro-ecologies, soil types, and farming systems [8]. The 
lowland, irrigated conditions of Dasenech Woreda 
present a unique set of challenges and opportunities, 
and the findings provide valuable data for developing 
targeted best management practices. 

CONCLUSION 

This study clearly demonstrates that both sorghum 
variety selection and the judicious application of 
blended NPSB fertilizer are critical factors influencing 
the growth, yield components, and ultimate grain yield 
of sorghum cultivated under irrigated conditions in 
Dasenech Woreda, Southern Ethiopia. The significant 
and positive response to increasing NPSB rates 
underscores the prevalent multi-nutrient deficiencies 
in the region's soils, affirming the necessity of balanced 
fertilization for optimal sorghum productivity. 

Crucially, the highly significant interaction between 
sorghum varieties and NPSB fertilizer rates highlights 
that the maximum benefits from fertilizer application 
are achieved when specific varieties are matched with 
their optimal nutrient levels. This indicates that tailored 
fertilizer recommendations are required to unlock the 
full genetic potential of different sorghum varieties in 
this specific irrigated environment. 

Based on these findings, it is recommended that 
farmers in Dasenech Woreda adopt blended NPSB 
fertilizer application as a key strategy to enhance 
sorghum yields. Future research should focus on 
further refining these recommendations through 
economic analysis to identify the most profitable NPSB 
rates for each promising sorghum variety. Additionally, 

long-term studies are warranted to assess the residual 
effects of NPSB application on soil health and fertility, 
ensuring the sustainability of enhanced sorghum 
production systems in the region. The findings 
contribute significantly to developing more precise and 
effective agricultural extension packages for sorghum 
growers in similar lowland irrigated agro-ecologies of 
Ethiopia. 

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American Journal Of Agriculture And Horticulture Innovations (ISSN: 2771-2559) 
 

 

Condition, South West Ethiopia.MSc. Thesis Jimma 
University College of Agriculture and Veterinary 
Medicine; 2018.  

 


