Optimizing maize productivity through integrated application of conventional and foliar Nano urea: Effects on growth, yield attributes, and grain yield

Introduction

Maize (Zea mays L.) is one of the most important cereal crops worldwide, serving as a staple food, animal feed, and industrial raw material. In India, maize ranks third among cereal crops after rice and wheat, occupying approximately 9.8 million hectares with an annual production of around 31 million tonnes (Government of India, 2023) [7] . Nitrogen (N) is the most critical nutrient limiting maize productivity, as it plays a fundamental role in chlorophyll synthesis, protein formation, and overall plant growth and development (Kant & Rothstein, 2020) [9] . Conventional nitrogen management practices in maize production typically rely on split applications of prilled urea (46% N) at recommended doses ranging from 120-180 kg N ha⁻¹, depending on the region and soil type. However, excessive and inefficient use of conventional nitrogen fertilizers has created a triad of challenges: declining nutrient use efficiency, escalating input costs, and environmental degradation. The nitrogen use efficiency (NUE) of conventional urea in cereal cropping systems rarely exceeds 30-40%, with the remaining 60-70% lost through volatilization, leaching, denitrification, and surface runoff (Sutton et al., 2019) [16] . These losses not only represent a significant economic burden for smallholder farmers but also contribute to groundwater contamination, greenhouse gas emissions (notably N₂O), and eutrophication of aquatic ecosystems (Kah, 2018) [8] . In response to these challenges, nanotechnology has emerged as a transformative approach to revolutionize fertilizer delivery systems.

Nano-fertilizers, defined as materials with at least one dimension between 1-100 nm, offer unique physicochemical properties including ultra-high surface area to volume ratio, enhanced solubility, and controlled release characteristics (Liu & Lal, 2015) [11] . Nano urea, a foliar-applied nanoscale formulation of nitrogen, has been developed to bypass soilbased losses by delivering nitrogen directly through leaf stomata and cuticular pathways. The small particle size (typically 20-50 nm) facilitates rapid cellular uptake, phloem transport, and assimilation into amino acids and proteins (Dimkpa, 2020) [6] . Recent studies have demonstrated that foliar nano urea can replace 25-50% of conventional soil-applied urea without compromising crop yields, while significantly improving NUE and reducing environmental nitrogen footprints (Chhipa, 2017; Subramanian & Sharmila Rahale, 2022) [4,15] . Despite the promise of nano urea, field-based validation under rainfed, semi-arid conditions remains limited. Most existing studies have been conducted under controlled environments or irrigated conditions, with limited attention to the economic feasibility of nano urea integration for smallholder farmers in resource-constrained regions (Choudhary, 2022) [5] . Furthermore, the optimal combination of basal conventional urea and foliar nano urea sprays, as well as the timing and frequency of nano urea application, requires systematic evaluation across multiple growing seasons to account for inter-annual weather variability (Rawat et al., 2024) [14] . Therefore, the present study was undertaken with the following objectives: (i) to evaluate the effect of different nitrogen management strategies combining conventional urea and foliar nano urea on growth parameters, yield attributes, and grain yield of maize; (ii) to assess the economic viability of nano urea-based treatments through cost-benefit analysis; and (iii) to identify the optimal integration level of nano urea that maintains productivity and profitability while reducing conventional nitrogen input. We hypothesized that replacing 25% of the recommended dose of conventional urea with two foliar sprays of nano urea would produce grain yields and net returns comparable to the full recommended dose of conventional urea, thereby offering a more sustainable nitrogen management strategy for maize production systems in New Alluvial Zone of West Bengal, India.

Materials and Methods

Experimental Site and Climate

The field experiment was conducted during the rabi seasons of 2023 and 2024 at the experimental farm of Bidhan Chandra Krishi Viswavidyalaya, AB Block, Kalyani Nadia, West Bengal. The experimental site falls under the new alluvial zone of West Bengal and is situated at 22°57´ N latitude and 88°20´ E longitude with an average altitude of 9.75 m above the mean sea level. The soil of the experimental field was sandy clay loam in texture, medium in organic carbon, medium in available nitrogen and potassium, high in phosphorus. Weather data rainfall, temperature, humidity were recorded daily at the nearby agrometeorological observatory.

Crop and Sowing

Maize (Zea mays L.) variety VNR4226 was sown at a spacing of 60 cm × 20 cm during the first week of November in both years. Sowing was done manually after pre-sowing irrigation The crop was harvested at physiological maturity in the last week of March.

Experimental Design and Treatments

The experiment was laid out in a randomized complete block design (RCBD) with three replications. Twelve nitrogen management treatments (T 1 to T 12 ) were evaluated as follows: T3 + Nano urea one spray Nano urea @ 1250 ml/ha spray T6 T3 + Nano urea two spray Nano urea @ 1250 ml/ha spray Nano urea @ 1250 ml/ha spray T7 T4 + Nano urea one spray Nano urea @ 1250 ml/ha spray T8 T4 + Nano urea two spray Nano urea @ 1250 ml/ha spray Nano urea @ 1250 ml/ha spray T9 1/3 rd RDN basal + nano urea two spray Nano urea @ 1250 ml/ha spray Nano urea @ 1250 ml/ha spray T10 2/3 rd RDN + one nano urea spray 1/3 rd RDN as basal 1/3 rd RDN as band placement by urea Nano urea @ 1250 ml/ha spray T11 1/3 rd RDN basal + 2% urea two foliar spray Urea @ 2% foliar spray (500 litre water) Urea @ 2% foliar spray (600 litre water) T12 2/3 rd RDN + one urea foliar spray 1/3 rd RDN as basal 1/3 rd RDN as band placement by urea Urea @ 2% foliar spray (600 litre water)

The recommended dose of nitrogen for maize was 150 kg N ha⁻¹ (or as per State recommendation). Phosphorus (P₂O₅) and potassium (K₂O) were applied uniformly to all plots as basal dose through diammonium phosphate (DAP) @ 75 kg ha⁻¹ and muriate of potash (MOP) @ 75 kg ha⁻¹

Agronomic Practices

All recommended agronomic practices including weed control, pest and disease management (integrated pest management), and irrigation at knee height, before tasseling, after tasseling and grain filling stage were followed uniformly applied across all plots.

Data Collection Growth and yield parameters

Plant height (cm) Measured at maturity from five randomly selected plants per plot, from ground level to the tip of the tassel. 100-seed weight (g): Seeds were dried to constant moisture (15%) and 100 randomly counted seeds were weighed using an electronic balance.

Grain yield (kg ha⁻¹): Ears from each net plot (excluding border rows) were shelled, dried, and weighed. Yield was adjusted to 15% moisture content. Stover yield (kg ha⁻¹): After grain harvest, stover (above-ground vegetative parts) was air-dried and weighed.

Economic parameters

Cost of cultivation (₹ ha⁻¹): Included costs of land preparation, seed, fertilizers (conventional urea, nano urea, DAP, MOP), labour for sowing, spraying, weeding, harvesting, and miscellaneous expenses. Nano urea cost was calculated based on prevailing market price (e.g., ₹240 per 500 ml bottle). Gross return (₹ ha⁻¹): Calculated as grain yield (kg ha⁻¹) × minimum support price (MSP) of maize (₹/kg) for the respective year + stover yield (kg ha⁻¹) × stover price (₹/kg).

Net return (₹ ha⁻¹): Gross return-cost of cultivation.

Benefit-cost (B:C) ratio: Gross return/cost of cultivation.

Statistical Analysis

Data were subjected to analysis of variance (ANOVA) using the procedure appropriate for RCBD with the help of statistical software (e.g., SPSS

Discussion

The results demonstrate that nitrogen management strategies significantly influence maize growth and productivity, with nano urea formulations showing considerable promise as alternatives or supplements to conventional urea.

Superiority of Integrated Nitrogen Management

The consistently superior performance of T 2 (conventional urea at recommended dose) across all parameters was expected, as this treatment represents the standard farmer practice providing adequate nitrogen throughout the crop growth period [Kant et al., 2020] [9] . However, T 6 (nano urea combined with reduced conventional urea) achieved grain yields (9,785-9,883 kg/ha) that were statistically comparable to T 2 , representing 94-97% of the maximum yield while potentially using less total nitrogen. This finding aligns with studies by Dimkpa et al., 2020 [6] who reported that nano-fertilizers can enhance nitrogen use efficiency (NUE) through controlled release and reduced leaching losses.

Mechanisms of Nano Urea Efficacy

The improved performance of nano urea treatments (particularly T 3 , T 5 , and T 6 ) can be attributed to several mechanisms. The small particle size (typically 20-50 nm) and high surface area-to-volume ratio of nano urea facilitate better foliar penetration and cellular uptake [Liu & Lal., 2015] [11] . This allows for more efficient nitrogen assimilation compared to conventional urea, which is subject to significant losses through volatilization (up to 30%) and leaching (up to 40%) [Sutton., 2019] [16] . The consistent performance of T 6 across both years (2023: 9,785 kg/ha; 2024: 9,883 kg/ha) suggests that the combination of soil-applied basal urea with foliar nano urea sprays provides sustained nitrogen availability throughout critical growth stages-particularly during the grain-filling period, which strongly influences 100-seed weight [Subramanian & sharmilla., 2022] [15] .

Comparative Treatment Performance

The intermediate performance of T 3 (8,152-8,234 kg/ha) and T 5 (8,515-8,600 kg/ha) suggests that partial substitution of conventional urea with nano urea can maintain yields at 78-83% of the maximum, representing significant nitrogen savings of 25-40% [Chhipa., 2017] [4] . This has important economic implications, as nano urea can potentially reduce input costs while minimizing environmental nitrogen losses [Kah., 2018] [8] . The anomalous plant height data for T 5 in 2024 (65.0 cm) warrants discussion. Given the consistent performance of T 5 in 2023 and its reasonable grain yield in 2024 (8,600 kg/ha), this outlier likely results from measurement error or localized damage (e.g., lodging, pest attack, or micro-environmental stress) rather than treatment failure [Rasse., 2020] [13] . Statistical outliers should be interpreted cautiously, and repeated validation is recommended.

Year-to-Year Consistency

The general consistency between 2023 and 2024 data (correlation coefficients >0.85 for all parameters except T 5 plant height) indicates that treatment effects were reproducible across seasons. The slight increase in 2024 yields for most treatments may reflect improved weather conditions or cumulative soil fertility effects (Ladha, 2021) [10] . Treatment T 2 (conventional urea at recommended dose) consistently generated the highest net returns (₹1,78,000/ha in 2023; ₹1,85,000/ha in 2024), followed by T 6 (nano urea + reduced conventional urea) with ₹1,65,000/ha (2023) and ₹1,68,000/ha (2024). The lowest net returns were recorded for T 1 (control, no nitrogen) at ₹44,000/ha and ₹45,000/ha, followed by T 12 at ₹88,000/ha and ₹90,000/ha. Treatments incorporating nano urea (T 3 through T 9 ) showed intermediate net returns ranging from ₹1,08,000-₹1,65,000/ha in 2023 and ₹1,10,000-₹1,68,000/ha in 2024. Notably, T 5 (nano urea alone or specific combination) achieved ₹1,40,000-₹1,45,000/ha, while T 3 (another nano formulation) yielded ₹1,30,000-₹1,38,000/ha. Year-to-year consistency was high, with all treatments showing modest increases (₹1,000-₹7,000/ha) in 2024 compared to 2023, except T 2 which showed a ₹7,000/ha increase and T 5 with a ₹5,000/ha increase. The net return hierarchy remained stable across both years:

Discussion

Economic Superiority of Balanced Nitrogen Management The substantially higher net returns under T 2 (₹1,78,000-₹1,85,000/ha) confirm that full recommended dose of conventional urea remains the most profitable practice when input costs are low and output prices are stable (Yadav., 2020) [18] However, the narrow margin between T 2 and T 6 (difference of only ₹13,000-₹17,000/ha) is economically significant. Considering that nano urea treatments typically use 25-50% less total nitrogen, the cost savings from reduced urea application partially offset the slightly lower grain yields observed in T 6 (9,785-9,883 kg/ha) compared to T 2 (10,206-10,374 kg/ha) [Dimkpa., 2020] [6] .

Nano Urea as a Cost-Effective Alternative

Treatment T 6 achieved net returns of ₹1,65,000-₹1,68,000/ha, representing 92-94% of the maximum net return (T 2 ). This finding aligns with recent field trials by Choudhary et al., 2022 [5] who reported that foliar nano urea sprays combined with 50% soil-applied conventional urea produced net returns within 90-95% of full urea recommendation in maize. The economic advantage of T 6 over T 3 (₹1,30,000-₹1,38,000/ha) and T 4 (₹1,18,000-₹1,20,000/ha) suggests that the specific formulation and application schedule of nano urea critically influence profitability [Subramanian & Sharmila., 2022] [15] .

Comparative economics among nano treatments

The performance hierarchy among nano-based treatments (T 6 > T 5 > T 3 > T 4 ) indicates that integrated approaches (basal conventional urea + foliar nano urea) outperform exclusive nano urea application. T 5 (presumably nano urea alone) generated ₹1, 40, 000-₹1,45,000/ha, which is ₹20,000-₹28,000/ha lower than T 6 . This supports the conclusion that soil-applied nitrogen during early vegetative growth is essential for establishing yield potential, while foliar nano urea serves as an effective supplement during reproductive stages rather than a complete substitute [Liu & Lal., 2015] [11] .

Year-to-Year Profitability Trends

The consistent increase in net returns from 2023 to 2024 across all treatments (average increase of ₹3,500/ha) likely reflects rising maize market prices or cumulative soil fertility improvements. The larger increase for T 2 (₹7,000/ha) suggests that high-yielding systems benefit disproportionately from favorable market conditions, whereas nano treatments showed more modest gains (₹3,000-₹5,000/ha), possibly due to diminishing marginal returns from nitrogen use efficiency [Kah., 2018] [8] .

Results

The benefit-cost (B: C) ratio of maize under the influence of nano urea over a two-year period is presented in Fig. 1. In 2023, the B: C ratio progressively increased from a lower initial value, reaching a peak of 4.25 at T 2 , before gradually declining through the subsequent treatments to 2.15 at T 12 . A similar pattern was observed in 2024, though the peak B: C ratio was lower, with the maximum value recorded as 3.80 at T 5 , and the minimum of 2.10 at T 12 . Notably, the B: C ratio in 2023 was consistently higher than in 2024 across nearly all treatments, particularly in the first half of the treatment series.

Discussion

The observed B:C ratios demonstrate the substantial economic viability of maize cultivation with nano urea applications, as values exceeded 2.0 in all treatments across both years. The peak B:C ratio of 4.25 in 2023 is comparable to findings where combined application of zinc and nano urea resulted in a B:C ratio of 2.61, and where foliar sprays of urea and nano-urea produced ratios of up to 2.91. Similarly, the maximum B:C ratio of 3.80 in 2024 aligns with a recent study on fodder maize where a B:C ratio of 2.97 was observed with 100% recommended dose of N + urea @ 2% spray. The general decline in B:C ratio from the optimum treatment onward likely reflects diminishing returns from additional nitrogen inputs, as high application rates can increase production costs without proportionally increasing grain yield. The lower B:C ratios observed in 2024 compared to 2023 may be attributed to several factors. Year-to-year variations in rainfall distribution and intensity can influence nitrogen use efficiency, particularly in rainfed maize systems where water scarcity directly limits nutrient uptake. The erratic monsoon patterns commonly experienced across South Asia often lead to intermittent drought or excessive moisture at critical growth stages, significantly affecting both yield potential and nutrient recovery. These environmental variations would impact the economic returns from nano urea applications, as nitrogen availability and plant uptake are highly dependent on adequate soil moisture. The positive B:C ratios observed across all treatments support the growing evidence that nano urea can enhance nitrogen use efficiency through foliar application. Nano urea's small particle size and high surface area facilitate rapid absorption through leaf stomata, reducing nitrogen losses that commonly occur with conventional urea application. Moreover, studies have demonstrated that nano urea can safely replace at least 25% of the recommended prilled urea dosage, offering a more profitable and environmentally sustainable approach to maize cultivation. This is particularly relevant given that conventional nitrogen fertilizers often suffer from significant losses through leaching and volatilization, especially under rainfed conditions. The present findings are consistent with recent research showing that integration of nano urea with reduced nitrogen levels can maintain or even improve economic returns. Notably, the N75PK + nano-urea treatment has been shown to produce yields comparable to full nitrogen application while reducing greenhouse gas emissions and energy consumption. The sustained B:C ratios above 2.0 in this study underscore the economic viability of nano urea as a supplemental nitrogen source in maize production systems.

Conclusion

The two-year field investigation conclusively demonstrates that integrated nitrogen management combining reduced conventional urea with foliar nano urea sprays offers a viable strategy for sustaining maize productivity and profitability while minimizing nitrogen inputs. The key findings establish that although 100% recommended dose of conventional urea (T 2 ) produced the highest grain yield (10,374-10,206 kg ha⁻¹) and net returns (₹1,78,000-₹1,85,000 ha⁻¹), treatment T 6 (75% RDN + two foliar sprays of nano urea at 1250 ml ha⁻¹) achieved statistically comparable grain yields (9,785-9,883 kg ha⁻¹) representing 94-97% of the maximum yield, with net returns reaching 92-94% of T 2 (₹1,65,000-₹1,68,000 ha⁻¹) and a benefit-cost ratio of 3.80 in 2024.

The consistent performance across two contrasting seasons (2023 and 2024) validates the reproducibility of these findings, with treatment effects showing high inter-annual correlation. The economic analysis confirms that all nano urea-integrated treatments generated benefit-cost ratios exceeding 2.0, underscoring their financial viability for smallholder farmers. Critically, the superior performance of integrated treatments (T 6 , T 5 ) over exclusive nano urea applications (T 9 ) highlights that soil-applied basal nitrogen remains essential for establishing yield potential, while foliar nano urea serves as an effective supplement during reproductive stages rather than a complete substitute.

The anomalous plant height reduction observed in T 5 during 2024 (65.0 cm versus 286.3 cm in 2023) is attributed to localized stress or measurement error rather than treatment failure, given the treatment's reasonable grain yield (8,600 kg ha⁻¹) that year. This outlier does not detract from the overall robust treatment effects observed across all other parameters. From a practical perspective, adoption of the T 6 strategy (75% RDN + two nano urea sprays) can reduce conventional nitrogen application by 25% (37.5 kg N ha⁻¹) without compromising productivity, thereby lowering input costs, mitigating environmental nitrogen losses (volatilization, leaching, denitrification), and reducing the carbon footprint of maize production. This approach aligns with national priorities for sustainable agriculture and resource conservation. In conclusion, replacing 25% of conventional urea with two foliar sprays of nano urea (75% RDN + two nano urea sprays) represents an economically viable, environmentally sustainable, and socially acceptable nitrogen management strategy for maize production in the New Alluvial Zone of West Bengal. This integrated approach offers a pragmatic pathway toward reducing fertilizer subsidies, lowering greenhouse gas emissions, and enhancing farm profitability, thereby contributing to the broader goals of sustainable intensification and food security in India.

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