Agronomic and Physiological Efficiency of Hybrid Yellow Corn (Zea mays L) Varieties to Different Fertilization Rates

Agronomic and Physiological Efficiency of Hybrid Yellow Corn (Zea mays L) Varieties to Different Fertilization Rates

*¹Lagaran, Casey P; ¹Taylaran, Renante D; ¹Gonzaga, Apolinario Jr B; ²Harnaiz, Leonie Love A

¹College of Agriculture, University of Science and Technology of Southern Philippines, USTP-Claveria

²College of Agriculture and Agri-Industries, Caraga State University – Ampayon

DOI: https://doi.org/10.51244/IJRSI.2025.12060004

Received: 22 May 2025; Accepted: 27 May 2025; Published: 26 June 2025

ABSTRACT

Corn (Zea mays L.) is a globally significant cereal crop, widely utilized for food, feed, and industrial purposes. In the Philippines, it ranks second to rice in agricultural significance. This vital crop plays a crucial role in sustaining the livelihoods of Filipino farmers. This study aimed to assess the productivity and efficiency of hybrid corn varieties under varying fertilization rates. The experimental design employed a Factorial Randomized Complete Block Design with three replications. Factor A consisted of five fertilizer treatments: control, 120N-90P2O5-60K2O Kg/ha, 60N-90P2O5-60K2O Kg/ha, 180N-90P2O5-60K2O Kg/ha, and 240N- 90P2O5-60K2O Kg/ha. Factor B comprises four hybrid varieties: B118G, P3530THR, Dekalb8899S, and NK6505. The study demonstrated significant effects on agronomic and physiological parameters of corn with varying fertilization rates. Statistically, all hybrid varieties exhibited positive responses to the application of N-P-K. Among the hybrids, NK6505 exhibited notable physiological efficiency and yield. Fertilization rates generally demonstrated a positive influence on plant growth, leading to enhanced yield attributes. The combination of 120N-90P₂O₅-60K₂O Kg/ha, combined with NK6505, yielded the highest net return and return on investment (ROI) of 265.20%. Thus, it is recommended that farmers adopt the combination of NK6505 with 120N-90P₂O₅-60K₂O Kg/ha fertilization rate to enhance the economic profitability of hybrid corn production.

Keywords: agronomic, corn, NPK, physiology, yield

INTRODUCTION

Hybrid yellow corn (Zea mays L.) is vital in global agriculture. Known for its impressive productivity, nutritional value, and adaptability to various climates, it’s a go-to crop for both human consumption and livestock feed. Over the years, researchers have developed hybrid varieties with better kernel quality, stronger resistance to diseases, and improved resilience to harsh environmental conditions. These advancements have solidified its importance in ensuring food security and supporting livestock production (Baghdadi et al., 2012; Mandić et al., 2018).

As one of the most widely grown cereals worldwide, hybrid yellow corn dominates agricultural landscapes in countries like the United States, China, and Brazil (Fromme et al., 2019). In the Philippines, it holds the position of the second most important cereal crop, coming right after rice. The southern region of Mindanao stands out as a major production area, thanks to its fertile land and favorable weather. For many Filipino farmers, corn farming isn’t just a source of income—it’s a way of life. It also plays a crucial role in the livestock industry, which makes up about 18.23% of the country’s agricultural gross value output (Biñas, 2021; Ortega, 2021).

However, scientific studies have focused heavily on improving the traits of hybrid yellow corn to boost productivity and sustainability. Key areas of interest include optimizing plant growth, enhancing nutrient absorption, building resistance to diseases, and maximizing photosynthesis efficiency (Khan et al., 2015; Fromme et al., 2019). Beyond its biological advantages, hybrid yellow corn also appeals to farmers because of its economic potential. Factors like input costs, market demand, and global trade trends all contribute to its profitability. Despite challenges such as climate change and market fluctuations, it continues to be a dependable choice, helping farmers sustain their livelihoods and support rural economies.

Nitrogen, an essential nutrient for corn growth, plays a critical role in plant health by aiding in chlorophyll production, protein synthesis, and energy transfer (Mandić et al., 2018). However, managing nitrogen levels is a balancing act. Over-application can lead to serious environmental problems, like water pollution and greenhouse gas emissions, making it essential to adopt precise and sustainable practices (Baghdadi et al., 2012; Ortega, 2021).

Thus, this study aimed to evaluate the agronomic and physiological efficiency of four distinct hybrid corn varieties under different fertilization rates. Specifically, the study seeks to: Determine the optimum nitrogen levels on agronomic traits; Evaluate the physiological responses to nitrogen application; Identify the optimal nitrogen application rates for the yield of each corn variety; and evaluate the economic efficiency of the hybrid corn varieties.

MATERIALS AND METHODS

Location and Duration of the Study

This research study was conducted at Claveria, Misamis Oriental (latitude 8°35’52”N, longitude 124°49’21”E), situated at an elevation of 510 meters above sea level. It is conducted through a collaborative project between the University of Science and Technology of Southern Philippines, Claveria Campus, and the ACDI Multipurpose Cooperative (External Funder) via the Center for High Value Crops. The study started from July 2023 to September 2023.

Materials

The study utilized a variety of materials, including a tractor for harrowing and plowing, data sheets for recording observations, and a selection of hybrid corn seeds (B118G, P3530THR, Dekalb8899S, and NK6505). Additionally, labels and tags made from bamboo sticks and tags were used for identification purposes. Other equipment includes a weighing scale for fertilizer preparation, a measuring tape for laying out the study area, a bolo for soil sampling, and a knapsack sprayer for herbicide application.

Methods

Experimental Design and Treatments

This study was laid out using a 5×4 Factorial Randomized Complete Block Design (RCBD), replicated three times. Moreover, five different fertilization rates served as Factor A, namely, F₁ – control, F₂ – 120N-90P₂O₅-60K₂O, F₃ – 60N-90P₂O₅-60K₂O, F₄ – 180N-90P₂O₅-60K₂O, and F₅ – 240N-90P₂O₅-60K₂O. On the other hand, four hybrid yellow corn varieties were utilized as Factor B, namely, B118G, P3530THR, Dekalb8899S, and NK6505.

Experimental Layout

An area of 8,760 m2 was utilized in the study. Within this area, each replication measures a plot size of 25 meters in length and 5 meters in width, a planting distance of 50 cm x 25 cm, 1 meter distance between replications, and 1 meter distance between treatments, respectively.

Soil Sampling

Before commencing the experiment to assess soil properties, a comprehensive soil analysis was conducted, collection of at least ten soil samples from various locations within the study area. These samples underwent thorough analysis to provide valuable insights into the soil characteristics and composition, ensuring a well-informed experimental setup.

Land Preparation

Field cleaning was done ahead of time. The land was plowed using a traditional plow and harrowed to pulverize the soil after the field experienced adequate rainfall. This comprehensive process included three passes of mechanized tractor plowing, complemented by manual plowing, to meticulously prepare the experimental site.

Layout Set-up

The study area was meticulously measured, spanning 79 meters in width by 59 meters in length. Within this designated area, individual plots were delineated, each measuring 25 meters in length by 5 meters in width. Replications were strategically spaced 2 meters apart to ensure statistical independence, with a 1-meter separation between adjacent plots to prevent any potential interference. To facilitate accurate identification and tracking of treatments, labels were prominently installed at each plot.

Planting Procedure

A single seed was carefully sown per hill. Seven days post-sowing, vigilant observation was conducted to identify any gaps or instances of multiple plants per hill. If such instances are observed, a proactive thinning and transplanting process is implemented to ensure optimal spacing and uniform plant distribution, thereby maximizing growth potential and overall experimental integrity.

Fertilizer Application

One week before planting, agricultural lime was applied at a rate of 1.25 tons per hectare to prepare the soil. During sowing, chicken manure was incorporated at 2.4 metric tons per hectare, except in the control plots. Fertilizer treatments were applied in three stages: 20% as a basal application at sowing, 30% at 21 days after sowing (DAS), and the remaining 50% at 30 DAS.

Water Management

This study emphasizes the use of rain-fed irrigation for corn cultivation, with a focus on optimizing and maximizing the utilization of rainfall as the primary water source for crop growth.

Herbicide Application 

The application of herbicide was judiciously determined based on the weed population observed within the experimental area. Given the tolerance of the corn varieties to Roundup herbicide, commonly used in Roundup Ready crops, its application is deemed both safe and suitable. This decision reflects a careful consideration of both weed management needs and the specific traits of the corn varieties, ensuring effective and responsible agricultural practices.

Pest Management

To safeguard against pest infestations, proactive measures were taken during the vegetative stage to detect any signs of pest presence. Should destructive pests be identified, targeted pesticide applications were deployed as a responsive intervention. This approach underscores our commitment to vigilant monitoring and swift action to protect crop health and optimize yield potential, ensuring a resilient and sustainable agricultural system.

Sampling Period and Data Gathering

Sampling and data gathering were done based on the following schedules: a two-week interval from 14 DAS to 70 DAS for agronomic and physiological parameters and yield parameters at harvest (120 DAS).

Harvesting

Harvesting was done 120 days post-sowing, employing a mechanized harvester primarily for non-data sampling purposes. In addition, manual harvesting of ten randomly selected samples was meticulously conducted to ensure accurate data collection. This comprehensive approach blends efficiency with precision, allowing for thorough evaluation of crop performance and yield potential.

Data Gathered

A. Agronomic Parameters

1. Plant Height (cm). This was measured by taking the length of the plant from the soil level to the tip of the longest leaf. The data will be gathered at 14, 28, 42, 56, and 70 days after sowing (DAS) with ten randomly selected sample plants.
2. Number of Leaves. The number of leaves was determined by visually counting the fully expanded leaves on the main stem of each plant. This assessment selected ten random plant samples from each plot at intervals of 14, 28, 42, 56, and 70 DAS.
3. Stem Diameter (mm). This was determined by measuring the stem using a vernier caliper. This measurement was conducted on ten randomly selected plant samples in each plot at intervals of 14, 28, 42, 56, and 70 DAS.

B. Physiological Parameters

1. Relative Chlorophyll Content (RCC). Total chlorophyll values were taken from five randomly selected plant samples in every plot using a Minolta Chlorophyll Meter (SPAD-502) at 14, 21, 28, 42, 56, and 70 DAS. The upper, middle, and lower parts of three fully expanded leaves were measured between 5:00 am and 8:00 am and were recorded as the mean of three measurements of each selected individual leaf.
2. Leaf Area Index (LAI). The leaf area index was measured manually by tracing the outline of each leaf using a ruler to calculate the leaf area. The LAI was calculated as the total leaf area per unit of ground area. This was collected at 14, 28, 42, 56, and 70 DAS, respectively.

C. Yield and Yield Components

1. Cob Length (cm). This was gathered by measuring the cob length from the tip of the base up to the top of the cob of the 10 samples in each treatment.
2. Cob Weight (g). The data were gathered by weighing the average of 10 samples in each treatment.
3. Weight of Kernels (g). Measurements were taken from ten samples in each treatment per replication using a weighing scale.
4. Weight of 1000 Kernels (g). Measurements were taken from 1000 grains of every treatment per replication using a weighing scale.
5. Grain Yield (t ha-¹). This was taken by weighing the total grain harvested from the plots after shelling and reported as 14% moisture content, with a unit of tons/ha.

D. Cost and Return Analysis

The cost and return analysis was computed based on the actual records of the cost and the gross sales on the prevailing price of corn in the market. The formula for calculating the Return on Investment is as follows:

Statistical Analysis

Statistical analysis was determined using the Analysis of Variance in a 5×4 Factorial in Randomized Complete Block Design (RCBD) for all the parameters obtained, and Tukey’s Test (HSD) at 5 % & 1% was used to test the differences among treatments

RESULTS AND DISCUSSION

Agronomic Parameters

Plant Height (cm)

Plant height across various hybrid corn varieties showed a highly significant difference in response to different fertilizer applications throughout the growth stages, except at 14 DAS, as presented in Table 1. The data indicate that the control treatment consistently exhibited the lowest plant height at 28 DAS (88.39 cm), 42 DAS (160.69 cm), and 56 DAS (166.96 cm). In contrast, treatments 120N-90P₂O₅-60K₂O, 60N-90P₂O₅-60K₂O, 180N-90P₂O₅-60K₂O, and 240N-90P₂O₅-60K₂O demonstrated statistically similar results, with significantly greater plant heights compared to the control across these time points.

However, at 70 DAS, the trend shifted, with the highest level of nitrogen application of 240N-90P₂O₅-60K₂O resulting in the shortest plant height, measuring 220.03 cm, followed by the control treatment at 235.73 cm. On the other hand, 60N-90P₂O₅-60K₂O recorded the tallest plant height at 255.93 cm. Statistically, 120N-90P₂O₅-60K₂O, 60N-90P₂O₅-60K₂O, and 180N-90P₂O₅-60K₂O demonstrated similar results.

Table 1. Plant height (cm) of agronomic and physiological efficiency of hybrid yellow corn varieties to different fertilization rates

TREATMENTS	PLANT HEIGHT (cm)
	14 DAS	28  DAS	42 DAS	56 DAS	70 DAS
Fertilizer Application
F1– Control	35.25	88.39b	160.69b	166.96b	235.73ab
F2– 120N-90P2O5-60K2O	36.69	94.96ab	173.28a	188.98a	251.12a
F3– 60N-90P2O5-60K2O	37.14	99.93a	178.01a	191.29a	255.93a
F4– 180N-90P2O5-60K2O	37.12	98.87a	177.58a	192.66a	253.64a
F5– 240N-90P2O5-60K2O	36.23	96.94a	178.20a	190.26a	220.03b
F-test	ns	**	**	**	**
Variety
V1 – B118G	37.79a	97.39a	170.47	187.33a	239.78
V2 – P3530THR	35.21b	95.61ab	176.72	193.45a	245.49
V3 – Dekalb8899S	36.52ab	98.58a	172.41	190.15a	244.56
V4 – NK6505	36.43ab	91.69ab	174.61	173.21b	243.32
F-test	*	*	ns	**	ns
Fertilizer Application x Variety
F-test	ns	ns	ns	ns	ns
CV (%)	6.16	6.63	5.75	7.14	8.29

Means in a column with the same letters are not significantly different at 5% level using Tukey’s test.

** – significant at a level of 1% of probability (p < 0.01)

 * – significant at a level of 5% of probability (0.01 =< p < 0.05)

ns – non-significant (p >= 0.05)

DAS – Days After Sowing

These results align with findings from prior research, showing the critical role of balanced fertilizer application in corn growth. Yukui et al. (2012) demonstrated that applying approved nitrogen (N) fertilizer rates optimizes plant height and stem perimeter compared to excessive or insufficient N treatment. Similarly, Bakhmanly (2023) found that complex fertilizers combining nitrogen, phosphorus, and potassium (N, P, K) significantly enhance maize plant height, with fertilized variations consistently outperforming unfertilized maize.

Moreover, when assessing various hybrid corn varieties subjected to different nitrogen levels, the data revealed significant differences in plant height at 14, 28, and 56 DAS, while no significant differences were observed at 42 and 70 DAS. At the early growth stage (14 DAS), B118G exhibited the tallest plant height, measuring 37.79 cm, while P3530THR recorded the shortest height at 35.21 cm. However, by 28 DAS, Dekalb8899S achieved the greatest plant height of 98.58 cm, whereas NK6505 was the shortest at 91.69 cm. At 56 DAS, NK6505 again recorded the lowest plant height at 173.21 cm among all varieties.

These findings are consistent with previous studies highlighting the impact of nitrogen-phosphorus-potassium (NPK) fertilization on plant growth and the variability in response across different hybrid corn varieties. Pusparini et al. (2018) and Asghar et al. (2010) reported that increasing NPK doses promote taller plants and higher yields, though the optimal dosages vary depending on the hybrid. Musa et al. (2023) and Awdalla et al. (2018) further emphasized the variability in hybrid performance, noting that some cultivars, such as white single-cross hybrids, respond more favorably to NPK fertilization than others, such as yellow three-way cross hybrids (Awdalla et al., 2018).

Number of Leaves

Table 2 reveals significant statistical differences in leaf count across different fertilizer applications at 28, 42, 56, and 70 DAS. The control treatment consistently recorded the lowest number of leaves, with averages of 7.59 at 28 DAS, 11.22 at 42 DAS, 10.72 at 56 DAS, and 13.50 at 70 DAS. Specifically, 240N-90P2O5-60K2O showed the highest average number of leaves at 8.11 at 28 DAS. Statistically, 120N-90P2O5-60K2O, 60N-90P2O5-60K2O, and 180N-90P2O5-60K2O exhibited the same values at 42, 56, and 70 DAS, to which 120N-90P2O5-60K2O showed the greatest number of leaves.

Additionally, among hybrid corn varieties subjected to different nitrogen levels, no significant effects on leaf count were observed during the early stages (14, 28, and 42 DAS). However, at 56 and 70 DAS, B118G recorded the lowest number of leaves, with 10.70 and 13.75 leaves, respectively, significantly lower than other hybrids. At 56 DAS, P3530THR significantly demonstrated a higher number of leaves than the other hybrids, while at 70 DAS, P3530THR, Deklab8899S, and NK6505 revealed statistically the same values.

Nitrogen impacts the growth as it is a key component of chlorophyll, amino acids, and proteins. Jones et al. (2018) demonstrated that higher nitrogen levels during the vegetative phase enhance leaf output by boosting photosynthetic activity, which supports overall plant vigor. However, excessive nitrogen application can delay maturity and reduce yield efficiency, underscoring the need for balanced nutrient management.

The observed variations in leaf count among treatments align with research on the impact of NPK fertilizers on maize leaf development. Some studies (Pantas Simanjuntak et al., 2021; Yoskader et al., 2023) reported no discernible effect on leaf number, while others (Lolita Dewi Pertaminingsih et al., 2018; Law-Ogbomo & Law-Ogbomo, 2009) found that NPK treatment increased leaf counts. The consistent differences in leaf numbers in this study, especially in fertilized treatments, support the latter findings, highlighting the benefits of optimized NPK application.

Furthermore, these results also align with Wang et al. (2022), who noted that hybrid corn varieties often display enhanced vegetative growth due to genetic traits that promote photosynthesis and leaf production. Efficient nutrient utilization and adaptability to environmental conditions further contribute to increased leaf yield in hybrids. Additionally, studies by Enujeke (2013) confirm that hybrid cultivars exhibit wide variability in growth traits, including leaf number and area, which are closely linked to maturity classification. These findings emphasize the interplay between genetics and nutrient management in optimizing leaf development and overall maize productivity.

Table 2. Number of leaves of agronomic and physiological efficiency of hybrid yellow corn varieties to different fertilization rates

TREATMENTS	NUMBER OF LEAVES
	14 DAS	28 DAS	42 DAS	56 DAS	70 DAS
Fertilizer Application
F1– Control	4.82	7.59b	11.22b	10.72b	13.50b
F2– 120N-90P2O5-60K2O	4.94	7.82ab	12.55a	11.58a	14.26a
F3– 60N-90P2O5-60K2O	5.09	8.03ab	12.38a	11.28ab	14.33a
F4– 180N-90P2O5-60K2O	4.98	8.00ab	12.50a	11.24ab	14.33a
F5– 240N-90P2O5-60K2O	4.97	8.11a	12.02ab	11.29ab	14.41a
F-test	ns	*	**	**	**
Variety
V1 – B118G	5.02	7.94	11.99	10.70c	13.75b
V2 – P3530THR	5.07	8.03	12.51	12.03a	14.38a
V3 – Dekalb8899S	4.91	7.85	12.20	11.29b	14.19a
V4 – NK6505	4.84	7.82	11.84	10.86bc	14.34a
F-test	ns	ns	ns	**	**
Fertilizer Application x Variety
F-test	ns	ns	ns	ns	ns
CV (%)	5.09	5.31	5.76	4.85	2.34

Means in a column with the same letters are not significantly different at 5% level using Tukey’s test.

** – significant at a level of 1% of probability (p < 0.01)

 * – significant at a level of 5% of probability (0.01 =< p < 0.05)

ns – non-significant (p >= 0.05)

DAS – Days After Sowing

Stem Diameter (mm)

Stem diameter is an indicator of inter-plant competition and resource allocation, serving as the primary conduit for water and nutrients while facilitating the translocation of photo assimilates. It determines the crop’s biological and stalk yield (Ijaz et al., 2015). Table 3 reveals that nitrogen fertilizer application significantly influenced the stem diameter of hybrid corn at 28, 42, and 70 DAS, while no significant differences were observed at 14 and 56 DAS. Treatments without fertilizer consistently recorded the smallest stem diameters, with measurements of 13.27 cm at 28 DAS, 15.22 cm at 42 DAS, and 17.16 cm at 70 DAS. Conversely, 120N-90P₂O₅-60K₂O and 240N-90P₂O₅-60K₂O statistically do not differ from each other, which had larger stem diameters compared to other treatments at 42 DAS. However, at 70 DAS, 180N-90P₂O₅-60K₂O and 240N-90P₂O₅-60K₂O illustrated similar values and were noted to acquire larger stem diameters.

The results align with findings by Machfud et al. (2019), Simanjuntak et al. (2021), and Afrillah et al. (2023), which demonstrate that NPK application enhances critical growth parameters, including stem diameter, plant height, and cob dimensions. Additionally, Ahmad Raksun et al. (2021) and Law-Ogbomo & Egberanwen et al. (2009) reported that NPK fertilizer treatments consistently resulted in significantly larger stem diameters compared to unfertilized controls.

Moreover, significant differences in stem diameter were observed among hybrid corn varieties at 28 and 56 DAS, with no significant differences at 14, 42, and 70 DAS. B118G consistently recorded the highest stem diameter during the early stage, measuring 17.21 cm at 28 DAS followed by the other varieties, which are statistically similar. At 56 DAS, P3530THR had the largest stem diameter at 19.84 cm, while B118G and NK6505 demonstrated statistically similar results. Additionally, no significant differences were observed in the interaction between nitrogen application and hybrid corn varieties, indicating that the effects of nitrogen and hybrid traits operate independently.

Table 3. Stem diameter (cm) of agronomic and physiological efficiency of hybrid yellow corn varieties to different fertilization rates

TREATMENTS	STEM DIAMETER (mm)
	14 DAS	28 DAS	42 DAS	56 DAS	70 DAS
Fertilizer Application
F1– Control	4.91	13.27b	15.22b	18.77	17.16b
F2– 120N-90P2O5-60K2O	5.17	15.82a	16.93a	18.98	18.51ab
F3– 60N-90P2O5-60K2O	5.42	15.99a	16.26ab	19.00	18.63ab
F4– 180N-90P2O5-60K2O	5.15	16.48a	16.09ab	18.40	18.68a
F5– 240N-90P2O5-60K2O	5.04	15.30ab	16.97a	18.97	18.99a
F-test	ns	**	**	ns	*
Variety
V1 – B118G	5.52	17.21a	16.36	18.54ab	18.16
V2 – P3530THR	5.11	14.65b	16.64	19.84a	18.77
V3 – Dekalb8899S	4.84	15.37b	15.91	18.05b	18.31
V4 – NK6505	5.09	14.27b	16.26	18.87ab	18.33
F-test	ns	**	ns	*	ns
Fertilizer Application x Variety
F-test	ns	ns	ns	ns	ns
CV (%)	13.15	11.35	6.62	9.64	6.96

Means in a column with the same letters are not significantly different at 5% level using Tukey’s test.

** – significant at a level of 1% of probability (p < 0.01)

 * – significant at a level of 5% of probability (0.01 =< p < 0.05)

ns – non-significant (p >= 0.05)

DAS – Days After Sowing

The results align with findings from Pusparini et al. (2018) and Syafruddin et al. (2012), which highlight that corn hybrids exhibit varied growth responses to fertilizer treatments, with some hybrids showing superior performance under optimal nutrient management. Furthermore, Hasan et al. (2020) and Simanjuntak et al. (2021) demonstrated that NPK fertilizers significantly enhance growth parameters, including stem diameter. This study’s observation that nitrogen application influences stem growth but does not interact significantly with hybrid variety supports previous findings emphasizing the independent role of hybrid genetics and nutrient application in corn development.

Physiological Parameters

Relative Chlorophyll Content

Using a chlorophyll meter (SPAD) is a valuable tool for farmers, enabling them to assess crop performance before nitrogen fertilization. This device offers a quick and efficient method for detecting the nutritional status of plants, serving as an effective alternative to traditional methods (Segatto et al., 2017). The relative chlorophyll content of hybrid corn subjected to varying levels of nitrogen shows significant differences among fertilizer applications at 14 DAS and 56 DAS, while no significant effects are observed at 28, 42, and 70 DAS, as shown in Table 4.

At 14 DAS, data revealed that the control treatment exhibited a significantly lower relative chlorophyll content (35.0) compared to other treatments. In contrast, 60N-90P2O5-60K2O and 180N-90P2O5-60K2O demonstrated higher values of 37.81 and 37.88, respectively. Similarly, at 56 DAS, the control treatment recorded the lowest RCC (40.48), continuing the trend observed at the earlier stage. These findings align with Horváth et al. (2019) and Hurtado et al. (2011), who reported that nitrogen fertilizer enhances chlorophyll levels, particularly during early and mid-growth stages. Moreover, Zhang et al. (2023) documented that hybrid maize treated with higher nitrogen dosages exhibited significantly higher chlorophyll levels than untreated controls, a trend also observed in this study. At 56 DAS, the treatments 120N-90P2O5-60K2O, 60N-90P2O5-60K2O, 180N-90P2O5-60K2O, and 240N-90P2O5-60K2O statistically do not differ from each other, which exhibited high readings of RCC.

Additionally, the data also showed significant differences among hybrid corn varieties at 14, 42, 56, and 70 DAS. At 14 DAS, NK6505 recorded the highest relative chlorophyll content among other varieties. At 42 DAS, the data shifted, with Dekalb8899S measuring 49.51, the highest among the varieties. At 70 DAS, P3530THR significantly obtained the highest relative chlorophyll content, while B118G, with 36.02, similar to Dekalb8899S at 38.18, recorded the lowest relative chlorophyll content.

Table 4. Relative chlorophyll content of agronomic and physiological efficiency of hybrid yellow corn varieties to different fertilization rates

TREATMENTS	RELATIVE CHLOROPHYLL CONTENT
	14 DAS	28 DAS	42 DAS	56 DAS	70 DAS
Fertilizer Application
F1– Control	35.08b	35.91	47.08	40.48b	36.79
F2– 120N-90P2O5-60K2O	36.76ab	37.79	47.46	46.40a	38.91
F3– 60N-90P2O5-60K2O	37.81a	37.98	47.18	47.08a	39.18
F4– 180N-90P2O5-60K2O	37.88a	38.25	47.48	46.45a	38.88
F5– 240N-90P2O5-60K2O	37.48ab	39.15	47.99	49.08a	40.79
F-test	*	ns	ns	**	ns
Variety
V1 – B118G	35.30b	36.46	46.76b	43.51b	36.02b
V2 – P3530THR	36.38b	38.58	47.02b	47.09ab	42.64a
V3 – Dekalb8899S	37.33ab	38.75	49.51a	49.31a	38.18b
V4 – NK6505	38.99a	37.46	46.44b	43.69b	38.80ab
F-test	**	ns	**	**	**
Fertilizer Application x Variety
F-test	ns	ns	**	ns	**
CV (%)	5.92	9.47	3.81	9.20	10.67

Means in a column with the same letters are not significantly different at 5% level using Tukey’s test.

** – significant at a level of 1% of probability (p < 0.01)

 * – significant at a level of 5% of probability (0.01 =< p < 0.05)

ns – non-significant (p >= 0.05)

DAS – Days After Sowing

Wang et al., (2022) discovered that hybrid maize cultivars had greater chlorophyll content under balanced NPK fertilizer applications, particularly during critical vegetative stages. The study found that hybrids have a larger yield potential and are therefore more responsive to fertilizer control, which aligns with the results observed in this study. The variation in chlorophyll content among the hybrid varieties supports the notion that hybrid maize cultivars can exhibit distinct responses to nutrient availability, with certain varieties, like NK6505 and Dekalb8899S, showing better chlorophyll development under the given treatments. This supports the findings of Wang et al. (2022), as the hybrid varieties demonstrated different chlorophyll responses based on their growth stages and nutrient treatments.

Moreover, among the hybrid corn applied with different nitrogen levels, the data show a highly significant difference during 42 and 70 DAS, as illustrated in Figure 1. At 42 DAS, the interactions between the combinations of 120N-90P2O5-60K2O and 60N-90P2O5-60K2O and all the hybrid varieties statistically exhibited similar values. However, at 70 DAS, it has been statistically noted that combinations 240N-90P2O5-60K2O and P3530THR, 180N-90P2O5-60K2O:NK6505, 120N-90P2O5-60K2O:B118G, and 120N-90P2O5-60K2ODeklab8899S) revealed almost similar RCC readings.

These findings align with Pusparini et al. (2018), who noted that NPK application often enhances chlorophyll content and production in corn. The observed increase in RCC with higher nitrogen rates also corresponds to the findings of Akram (2014), who reported that nitrogen application improves chlorophyll pigments and yield components in maize hybrids. Furthermore, the variability in responses among hybrids supports the conclusions of Linders et al. (2024), which highlighted the role of genotype-by-environment interactions in shaping chlorophyll content and crop performance.

Figure 1. Relative chlorophyll content at 42 and 70 DAS of agronomic and physiological efficiency of hybrid yellow corn varieties to different fertilization rates.

Leaf Area Index

The analysis of variance on the leaf area index (LAI) at different nitrogen application levels revealed no significant differences among treatments at 14, 28, 42, and 56 DAS. However, a highly significant difference was observed at 70 DAS. Among the treatments, hybrid corn applied with 120N-90P2O5-60K2O recorded the highest LAI at 9.17. In contrast, the application of 180N-90P2O5-60K2O resulted in a LAI of 7.33, which was statistically similar to the control treatment (7.66), the lowest recorded value. These results are summarized in Table 5.

Nitrogen application has been widely reported to enhance LAI and yield. A positive relationship between LAI and grain yield has also been documented. This study’s findings align with those of Berdjour et al. (2020), who reported that the application of NPK fertilizers had a significant impact on LAI, leaf area, and leaf number in maize grown in the Guinea Savanna. Their research also highlighted a positive correlation between LAI and grain yield, emphasizing the critical role of nitrogen in improving crop productivity.

Moreover, 120N-90P2O5-60K2O acquired higher chlorophyll content at 70 DAS which resulted in greater leaf area. Chlorophyll content and leaf area play a crucial role in regulating water, energy, and carbon exchange during photosynthesis (Mustafa et al., 2024). According to Yang et al. (2022), the chlorophyll content in a plant’s leaves can reflect the overall photosynthetic productivity of the population.

Table 5. Leaf area index of agronomic and physiological efficiency of hybrid yellow corn varieties to different fertilization rates

TREATMENTS	LEAF AREA INDEX
	14 DAS	28 DAS	42 DAS	56 DAS	70 DAS
Fertilization Rates (N-P-K)
F1– Control	0.46	1.55	5.63	6.70	7.66b
F2– 120N-90P2O5-60K2O	0.46	1.68	6.40	7.00	9.17a
F3– 60N-90P2O5-60K2O	0.47	1.55	5.87	6.95	7.90ab
F4– 180N-90P2O5-60K2O	0.45	1.62	5.67	7.27	7.33b
F5– 240N-90P2O5-60K2O	0.51	1.50	6.23	7.14	8.33ab
F-test	ns	ns	ns	ns	**
Variety
V1 – B118G	0.53a	1.60	5.34b	7.09	6.80b
V2 – P3530THR	0.46ab	1.61	5.90ab	7.00	8.02a
V3 – Dekalb8899S	0.42b	1.61	6.28a	7.20	8.59a
V4 – NK6505	0.47ab	1.50	6.32a	6.75	8.90a
F-test	**	ns	**	ns	**
Fertilization Rates x Variety
F-test	ns	ns	*	ns	**
CV (%)	16.03	19.85	13.36	12.31	13.98

Means in a column with the same letters are not significantly different at 5% level using Tukey’s test.

** – significant at a level of 1% of probability (p < 0.01)

* – significant at a level of 5% of probability (0.01 =< p < 0.05)

ns – non-significant (p >= 0.05)

DAS – Days After Sowing

Additionally, significant effects among hybrid corn varieties were observed at specific growth stages, notably at 14, 42, and 70 DAS. At 14 DAS, B118G exhibited the highest LAI value among the varieties, measuring 0.53, while P3530THR recorded the lowest value at 0.46. Additionally, at 42 and 70 DAS, NK6505 achieved the highest LAI values, reaching 8.90 at 70 DAS. Similarly, nitrogen fertilization further enhances LAI in hybrids, with varying responses observed among different hybrid varieties (Szabó et al., 2022). The relationship between LAI and productivity is well-established; greenery index values at flowering are strongly correlated with grain yield (Castellanos-Reyes et al., 2017).

Moreover, significant interactions between different fertilization rates and hybrid corn varieties were observed at 42 and 70 DAS. Among all combinations, 60N-90P2O5-60K2O and NK6505 achieved the highest LAI value, reaching 10.15 at 70 DAS. However, other combinations revealed statistically similar results to the combination; these combinations can be found in F2, F3, F4, and F5 and selected hybrid varieties, as shown in Figure 2. Studies on hybrid corn varieties and NPK fertilizer interactions have demonstrated varying effects on growth. Nitrogen levels significantly influenced the leaf area index in hybrid corn, with some varieties responding more effectively to fertilizer treatments (Szabó et al., 2022). Similarly, Musa et al. (2023) reported that the combination of NPK fertilizer at 200:150:100 kg/ha and the Pioneer variety resulted in the highest yield of 11.81 t/ha.

Figure 2. Leaf area index at 42 and 70 DAS of agronomic and physiological efficiency of hybrid yellow corn varieties to different fertilization rates.

Yield and Yield Components

Cob Length (cm)

Statistical analysis revealed significant differences in cob length among hybrid corn varieties and fertilizer applications, as shown in Table 6. Fertilizer treatments 240N-90P2O5-60K2O, 60N-90P2O5-60K2O, 180N-90P2O5-60K2O, and 120N-90P2O5-60K2O resulted in statistically similar values, which demonstrated the longest cobs. Among the hybrid corn varieties, NK6505 exhibited superior cob length (18.36 cm), while P3530THR recorded the shortest cob length (16.25 cm). Furthermore, the interaction of 240N-90P2O5-60K2O combined with NK6505 achieved the highest cob length (19.45 cm), whereas control: P3530THR recorded the lowest cob length (14.86 cm). Statistically, several treatment combinations revealed similar results.

These results align with findings from Law-Ogbomo and Law-Ogbomo (2009) and Zapałowska and Jarecki (2024), which reported that NPK fertilization significantly enhances cob length, grain yield, and other yield components in maize. Zapałowska and Jarecki (2024) highlighted that mineral NPK fertilization outperforms organic fertilizers in improving cob length, grains per cob, and thousand-grain weight. Additionally, Thakur et al. (2009) demonstrated that NPK application considerably increases cob length, diameter, and grain production, consistent with the positive impact of NPK fertilizer in this study.

In terms of hybrid variety performance, the findings partially align with Azam et al. (2007), who reported that Pioneer hybrids produced the longest cobs and highest grain output. However, in this study, NK6505 outperformed P3530THR in cob length, contrasting with Azam et al.’s observations of superior performance by specific Pioneer hybrids. Additionally, the study confirms Zarei et al.’s (2012) findings that cob length and yield components, such as grain weight and kernel number, significantly influence grain yield.

Table 6. Cob length (cm), cob weight (g), dry weight (1000 grains) and grain yield of agronomic and physiological efficiency of hybrid yellow corn varieties to different fertilization rates

TREATMENTS	COB LENGTH (cm)	COB WEIGHT (g)	DRY WEIGHT 1000 GRAINS (g)	GRAIN YIELD (t ha-1)
Fertilizer Application
F1– Control	16.00b	168.91c	225.33	6.95b
F2– 120N-90P2O5-60K2O	17.31a	201.16bc	235.91	9.72a
F3– 60N-90P2O5-60K2O	17.55a	205.58bc	236.58	9.71a
F4– 180N-90P2O5-60K2O	17.35a	234.16ab	253.41	9.78a
F5– 240N-90P2O5-60K2O	18.09a	246.25a	237.25	9.97a
F-test	**	**	ns	**
Variety
V1 – B118G	17.24b	177.06b	238.00	8.12b
V2 – P3530THR	16.25c	199.40b	230.26	9.41a
V3 – Dekalb8899S	17.18bc	190.20b	234.40	9.52a
V4 – NK6505	18.36a	278.20a	248.13	9.85a
F-test	**	**	ns	**
Fertilizer Application x Variety
F1V1	16.21aAB	154.00aA	227.66	6.61bA
F1V2	14.86aB	151.00bA	217.33	6.90cA
F1V3	15.73bAB	148.66aA	220.00	7.07bA
F1V4	17.21aA	222.00bA	236.33	7.19bA
F2V1	17.00aA	149.00aB	241.33	8.19aC
F2V2	16.61aA	200.00abAB	226.66	9.66bB
F2V3	17.08abA	207.00aAB	237.66	9.99aAB
F2V4	18.47aA	248.66bA	238.00	11.04aA
F3V1	18.04aA	216.33aA	253.33	9.13aA
F3V2	16.61aA	185.00bA	214.66	9.77bA
F3V3	17.08abA	209.33aA	223.66	9.91aA
F3V4	18.47aA	211.66bA	254.66	10.00aA
F4V1	17.26aAB	182.00aB	244.66	8.23aC
F4V2	16.24aB	186.33bB	244.00	9.64bB
F4V3	17.53abAB	217.00aB	258.33	10.16aAB
F4V4	18.39aA	351.33aA	266.66	11.09aA
F5V1	17.68aAB	184.00aC	223.00	8.43aC
F5V2	17.10aB	247.66aB	248.66	11.10aA
F5V3	18.13aAB	169.00aC	232.33	10.47aAb
F5V4	19.45aA	357.33aA	245.00	9.91aB
F-test	*	**	ns	**
CV (%)	5.60	16.42	11.52	5.52

Means in a column with the same letters are not significantly different at 5% level using Tukey’s test.

** – significant at a level of 1% of probability (p < 0.01)

 * – significant at a level of 5% of probability (0.01 =< p < 0.05)

ns – non-significant (p >= 0.05)

DAS – Days After Sowing

Cob Weight (g)

The cob weight of different hybrid corn varieties applied with varying levels of nitrogen showed highly significant differences among fertilizer treatments, hybrid varieties, and their interactions, as presented in Table 6. The data revealed a trend similar to that observed in cob length. Control treatment recorded the lowest cob weight at 168.91 g, while the application of 240N-90P₂O5-60K₂O resulted in the highest cob weight at 246.25 g.

Among the hybrid varieties, NK6505 exhibited the highest cob weight, measuring 278.20 g, outperforming other varieties. Furthermore, the interaction of 240N-90P2O5-60K2O:NK6505 achieved a significantly higher cob weight of 357.33 g, indicating the combined effect of optimal fertilizer application and superior hybrid variety selection, but statistically, there are other combinations demonstrated similar values to 240N-90P2O5-60K2O: NK6505, as shown in Table 6.

Dry Weight of 1000 Grains (g)

The dry weight of 1000 grains of hybrid corn applied with varying nitrogen levels showed no significant effect between fertilizer treatments or their interactions, as presented in Table 6.

While some studies have reported significant effects of fertilizer treatments on growth indices and yield components (Khan, 2022; Pusparini et al., 2018; Kandil, 2013; Awdalla et al., 2018), the findings on 1000-grain weight have been inconsistent. For example, Khan (2022) found that while tillage methods and fertilizer levels did not significantly interact for most growth indices, they did influence 1000-grain weight. This contrasts with the current study, which found no significant effect. Similarly, Kandil (2013) observed that increased nitrogen levels produced the highest 1000-grain weight, aligning partially with Pusparini et al. (2018), who reported that 300 kg/ha of NPK fertilizer optimized hybrid corn growth and production.

In contrast, Awdalla et al. (2018) found that NPK levels and hybrid cultivars did not affect 100-grain weight, a result that aligns with the findings of this study, suggesting that the impact of NPK fertilization on grain weight may vary based on hybrid type, soil conditions, and agronomic practices. Additionally, Pusparini et al. (2018) noted that different hybrid varieties respond variably to fertilizer application, with some hybrids outperforming others in yield, supporting the idea that hybrid-specific responses may explain the lack of uniform effects on 1000-grain weight.

Grain Yield (t ha-¹)

The grain yield of hybrid corn applied with varying levels of nitrogen fertilization showed highly significant differences, as presented in Table 6. The data revealed that all fertilizer treatments, regardless of nitrogen levels, produced statistically similar grain yields, except for the control treatment, which had the lowest yield at 6.95 t ha⁻¹.

Among the hybrid corn varieties, NK6505 recorded the highest grain yield at 9.85 t ha⁻¹, followed closely by Dekalb 8899S with 9.52 t ha¹ and P3530THR with 9.41 t ha⁻¹. In contrast, B118G produced the lowest yield among the varieties, at 8.12 t ha⁻¹. The interaction between fertilizer application and hybrid corn varieties also showed highly significant differences. Statistically, the combinations of 120N-90P2O5-60K2O x NK6505, 60N-90P2O5-60K2O x B118G, 60N-90P2O5-60K2O x Dekalb8899S, 60N-90P2O5-60K2O x NK6505, 180N-90P2O5-60K2O x NK6505, and 240N-90P2O5-60K2O x P3530THR demonstrated similar results, thus, these combinations achieved higher grain yields compared to other combinations.  The control x B118G recorded the lowest grain yield, at 6.61 t ha⁻¹.

These findings are supported by Tamang et al. (2024), who reported that increasing nitrogen levels can enhance grain yield up to a certain threshold, beyond which yields may plateau or even decline. Additionally, Adhikary and Adhikary (2013) found that higher nitrogen doses in acidic soils can result in maximum grain yields, underscoring the importance of soil conditions in determining nitrogen response.

Similarly, Miao et al. (2007) highlighted that variable-rate nitrogen application can improve yields for certain hybrids compared to uniform-rate application, though hybrid selection plays a critical role in optimizing both yield and grain quality. This aligns with Adhikary and Adhikary’s (2013) findings that optimal nitrogen rates depend on soil conditions, emphasizing the need for tailored fertilizer management strategies to maximize hybrid corn yield.

Cost and Return Analysis 

Return on Investment (%) 

Return on investment is a crucial economic metric that compares the financial advantages to the related costs to assess how profitable agricultural techniques are. To evaluate the financial effectiveness of various treatments, ROI was examined in this study, presented in Table 7. The findings showed a highly substantial impact, highlighting how important cost-effective measures are to optimizing profitability. These results offer important new information about how to best allocate resources for agricultural output that is both sustainable and profitable.

The cost of production was computed based on the prevailing price of hybrid corn seeds, labor costs from land preparation, planting, maintenance, and harvesting, per unit area. The data shows that the treatment combination of 240N-90P₂O₅-60K₂O and Dekalb8899S incurred the highest total production costs at approximately Php90, 215 per hectare, while control and P3530THR recorded the lowest expenses at approximately Php50,933.30.

Table 7. Return on investment of 1-ha production of agronomic and physiological efficiency of hybrid yellow corn varieties to different fertilization rates

	TOTAL PRODUCTION COST (PhP)	GROSS SALES @PhP 25.00 kg-1	NET INCOME (PhP)	ROI (%)
Fertilizer x Variety
F1V1	51,066.66	165,430.72	114,364.06	223.95aA
F1V2	50,933.30	172,747.85	121,814.55	239.16abA
F1V3	52,850.00	176,989.66	124,139.66	234.89abA
F1V4	52,700.00	179,958.93	127,258.93	241.48aA
F2V1	76,187.66	212,832.98	136,645.32	179.35bC
F2V2	76,054.30	249,630.71	173,576.41	228.23abB
F2V3	77,971.00	257,796.21	179,825.21	230.63abAB
F2V4	77,821.00	284,201.49	206,380.49	265.20aA
F3V1	71,276.66	236,375.05	165,098.39	231.63aA
F3V2	71,143.30	252,281.85	181,138.55	254.61aA
F3V3	73,060.00	255,887.39	182,827.39	250.24aA
F3V4	72,910.00	258,750.61	185,840.61	254.89aA
F4V1	78,632.16	213,787.39	135,155.23	171.88bC
F4V2	78,498.80	248,994.44	170,495.64	217.20bB
F4V3	80,415.50	262,038.02	181,622.52	225.86abAB
F4V4	80,265.50	285,367.99	205,102.49	255.53aA
F5V1	88,431.66	218,771.52	130,339.86	147.39bC
F5V2	88,298.30	285,474.04	197,175.74	223.31abA
F5V3	90,215.00	269,779.33	179,564.33	199.04bAB
F5V4	90,065.00	255,781.34	165,716.34	184.00bB
F-test                                                                                                                                        **
CV (%)				7.17

Means in a column with the same letters are not significantly different at 5% level using Tukey’s test.

** – significant at a level of 1% of probability (p < 0.01)

 * – significant at a level of 5% of probability (0.01 =< p < 0.05)

ns – non-significant (p >= 0.05)

DAS – Days After Sowing

Moreover, 240N-90P₂O₅-60K₂O and P3530THR combination produced the highest gross sales at 285,474.04. In contrast, the highest net return was gained by the combination 120N-90P₂O₅-60K₂O:NK6505, which also yielded the highest ROI of 265.20%. Lower ROIs indicate less profitability relative to investment, stressing the importance of strategic decision-making in agricultural management. It has been noted that 240N-90P₂O₅-60K₂O: P3530THR and 120N-90P₂O₅-60K₂O:NK6505 varied in the total production cost. The combination of 120N-90P₂O₅-60K₂O:NK6505 acquired a lower production cost compared to 240N-90P₂O₅-60K₂O:P3530THR, which resulted in 120N-90P₂O₅-60K₂O:NK6505 acquiring the highest ROI.

These findings give useful insights for farmers and stakeholders, assisting them in improving production techniques to increase profitability and achieve long-term economic returns in maize cultivation. Farmers can dramatically enhance their ROI and overall financial outcomes by selecting the best fertilizer application and hybrid variety combinations.

CONCLUSION

This study aimed to evaluate the agronomic and physiological efficiency of four distinct hybrid corn varieties under varying nitrogen fertilization rates. This research study was conducted at Claveria, Misamis Oriental. Data revealed that the application of varying nitrogen levels significantly influenced the agronomic traits of hybrid corn, including plant height, number of leaves, and stem diameter. Physiological responses, particularly Relative Chlorophyll Content (RCC) and Leaf Area Index (LAI), also varied significantly among hybrids and nitrogen treatments. The combination of 120N-90P₂O₅-60K₂O and NK6505 showed superior performance, achieving the highest RCC, LAI, cob length, cob weight, and grain yield. This combination also resulted in the highest return on investment at 265.20%. Based on these findings, the 120N-90P₂O₅-60K₂O: NK6505 combination is recommended to optimize grain yield and profitability, making it a suitable option for improving economic outcomes and production efficiency in hybrid corn cultivation.

ACKNOWLEDGEMENT

In profound gratitude and humility, she extends her heartfelt appreciation to Almighty God for His Glory, Guidance, and Grace, which have illuminated her path and enriched her endeavors with purpose and fulfillment. To her beloved parents, especially her father, Mr. Richard T. Palacio, who instilled in her the profound significance of a life led under God’s guiding light, and to her devoted mother, Mrs. Nelsie T. Palacio, whose unwavering support and care allowed her to pursue her dreams while nurturing her children, she expresses deep admiration and thanks. To her siblings, whose unwavering support in all facets of life provided strength and encouragement, she is profoundly grateful.

Her loving husband, Mr. Jimbo Y. Lagaran, is celebrated for his boundless love and steadfast support—financially, emotionally, and spiritually—making possible her aspirations and easing her burdens with unyielding devotion to their family. Her sons, Bronn, Johnsnow, and Ragnar, are cherished inspirations and sources of comfort, enabling her to persevere through challenges and triumphs on her journey. Acknowledgment is extended to her esteemed Adviser, Dr. Renante D. Taylaran, whose guidance and paternal mentorship were pivotal throughout her academic and personal growth.

To Dr. Nelda R. Gonzaga, Dr. Eric Randy R. Politud, and Dr. Imelda U. Hebron, esteemed members of her thesis panel, are recognized for their academic guidance and invaluable contributions to her manuscript revisions. Heartfelt appreciation is extended to her cherished friends, whose unwavering support and camaraderie provided solace and encouragement.

The USTP Claveria Center for High Value Crops, led by Dr. Apolinario B. Gonzaga, Jr., is acknowledged for providing transformative academic opportunities and fostering her passion for agriculture, enriching her dedication to her responsibilities. And big thanks to Ms. Leonie Love A. Harnaiz, research assistant, for the support during and after the conduct of the study.

Finally, sincere gratitude is extended to the CHED-SIKAP for their grant, enabling the realization of her academic pursuits. In reflection and gratitude, she acknowledges these individuals and institutions whose unwavering support and encouragement have shaped her journey and contributed to her personal and academic growth.

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