Effect of integrated application of nano urea and conventional urea on soil parameters, nutrient uptake and nitrogen use efficiency of winter maize (Zea mays L.)

Introduction

Maize (Zea mays L.) is a key crop in Bihar, cultivated across roughly 5.58 lakh hectares with an average yield of 7,262 kg/ha (UPAg, 2023-24) above the national average of 5,529 kg/ha, yet still short of the attainable potential of 8.5 t/ha (Jat et al., 2025) [1] . As a nutrient-demanding crop (Setiyono et al., 2010) [2] , maize relies heavily on efficient nitrogen management for higher yields. Nitrogen, a core component of proteins, chlorophyll, enzymes, and growth hormones, drives cell division, cell enlargement, and photosynthesis, making its adequate supply essential for healthy growth and productivity (Leghari et al., 2016) [3] . Urea remains the dominant nitrogenous fertilizer, yet its nitrogen use efficiency is poor (30-50%), resulting in substantial nitrogen loss to the environment (Govindasamy et al., 2023) [4] . This inefficiency also carries a heavy economic cost; the government spends nearly ₹1.32 lakh crore annually on nitrogenous fertilizer subsidies, out of a total ₹1.95 lakh crore fertilizer subsidy outlay (Department of Fertilizers, 2023-24) [5] . Additionally, the sudden influx of readily available nitrogen from urea stimulates microbial activity that consumes soil organic carbon, accelerating its depletion (Chen et al., 2014) [6] ; a serious concern given the already low organic carbon reserves in Indian soils. These issues underscore the need to improve nitrogen use efficiency and reduce dependence on conventional urea through alternatives like nano urea. Owing to their extremely small size (1-100 nm), nanoparticles carry a high nutrient load and are absorbed more readily by plants than conventional fertilizers. Applied as a foliar spray, they penetrate the leaf cuticle and stomata (10-80 µm) directly and may also enter cells via endocytosis, unlike conventional fertilizers, which rely on slower diffusion and active transport. This improves nutrient solubility, delivery, and overall nitrogen use efficiency (Nongbet et al., 2022) [7] . While 4% nano urea has been reported to replace about 25% of conventional urea, findings vary across studies. This study uses a higher-concentration 12% nano urea to test whether it can achieve a greater substitution while improving maize yield. Accordingly, a field experiment titled "Effect of Integrated Application of Nano Urea and Conventional Urea on Soil parameters, Nutrient uptake and Nitrogen Use Efficiency, and Economics of Winter Maize (Zea mays L.)" was conducted on problem soils of Samastipur district, Bihar, during Rabi 2025-26, with the objective of evaluating the effect of 12% nano urea on the nitrogen use efficiency of winter maize.

Materials and method

Experimental site

An experiment conducted at Pusa farm of Dr. Rajendra Prasad Central Agricultural University, India to understand performance of combined application of nano urea and nitrogenous fertilizer on yield and nitro-gen use efficiency of winter maize. The experimental area located at 25.9780° N latitude and 85.6488° E longitude, with an altitude of 52.9 meters above mean sea level (MSL). The crop growing period (Standard meteorological week of 46 in 2025 to 18 in 2026) in experimental area has characterized by highest temperature of 35.37°C elsius and lowest temperature 5.21° Celsius, average relative humidity of (%) (58-107) and highest rainfall of 29 mm. The experimental site's soil characterized as sandy loam soil and has pH, E.C (dS/m), soil organic carbon of (%) of 8.29, 0.34, 0.42 respectively & available nitrogen (kg/ha), available phosphorus (kg/ha), available potassium (kg/ha) of 187, 11.78, 111.29 respectively.

Experimental details

The experiment of performance of combined application of nano urea and nitrogenous fertilizer on yield and nitrogen use efficiency of winter maize (Variety: DKC 9081) conducted in randomized block design of 8 treatments and 3 replications in a plot size of 21 m 2 area. In this experiment we use urea (46% N) and nano urea (12% w/v) which is prepared by Shriram fertilizers private limited. Treatments details are like that: T 1 (Control), T 2 (100% Urea), from T 3 to T 5 comprised of 100%, 85%, 70% Urea, combined with 2.5 ml/l of nano urea at V3 (3 leaf stage) and tasselling stage and from T 6 to T 8 comprised of 100%,

Soil analysis

For soil analysis we collected soil sample from 15 cm depth in a zigzag pattern from 4 places of each treatment and replication followed by air drying and sieving through 2 mm of collected soil sample.

Then the processed sample gone through analysis of pH and EC (dS/m) using standard protocols (Jackson, 1973) [8] , soil organic carbon (%) (Walkley et al., 1934) [9] , available nitrogen by using alkaline permanganate method (Subbiah et al., 1956) [10] , available phosphorus by using sodium bi-carbonate method (NaHCo 3 ) (Olsen et al., 1954) [11] , available potassium by using ammonium acetate (NH 4 OAc) method (Merwin et al., 1951) [12] .

Plant nitrogen analysis

For plant analysis, samples were oven-dried followed by grinding. The processed sample gone through modified micro-Kjeldahl method following di-acid (H2SO4-salicylic acid) digestion (Piper, 1966) [13] .

Nitrogen use efficiency

Nitrogen use efficiency was assessed using agronomic efficiency (AE), physiological nitrogen uses efficiency (PNUE), apparent recovery efficiency (ARE), and nutrient harvest index (NHI). AE was calculated as the increase in grain yield per unit of nitrogen applied (Grain yield in treated plot (kg/ha) -Grain yield in control (kg/ha))/N applied (kg/ha), while PNUE was expressed as the increase in grain yield per unit increase in nitrogen uptake (Grain yield in treated plot (kg/ha) -Grain yield in control (kg/ha))/(N uptake in treated plot (kg/ha) -N uptake in control (kg/ha)). ARE (%) was computed as the proportion of applied nitrogen recovered by the crop [(N uptake in treated plot (kg/ha) -N uptake in control kg/ha))/N applied (kg/ha) × 100], and NHI (%) was calculated as the ratio of nitrogen accumulated in grain to total nitrogen uptake by the plant (N uptake in grain (kg/ha)/Total N uptake in plant (kg/ha)) × 100.

Statistical analysis

Statistical analysis and graphical representation was carried out using the AgroR and ggplot2 package respectively in R. Treatment means are compared with 5% significance level using LSD and SEm (±).

Result and discussion

Soil parameter: Data on post-harvest soil properties present on table no 3.5. Although post-harvest soil properties such as pH, EC (dS/m), soil organic carbon (%), and available nitrogen, phosphorus, and potassium (kg/ha) did not differ significantly among treatments, a numerical trend was evident. Post-harvest available nitrogen status was higher under T 3 (100% Urea + 2 foliar sprays of nano urea @ 2.5 ml/l), whereas available phosphorus and potassium were relatively higher under T 1 (control . As P and K were applied uniformly across treatments, residual differences reflected crop uptake alone higher-yielding treatments removed more and left lower residues, while T 1 , with the least biomass, retained the highest residual P and K.

and nutrient uptake (kg/ha) by plant can be presented in fig 3.4 and fig 3.5 respectively. Nutrient uptake is multiplication of nutrient content (%) and yield (kg/h). T 3 (100% Urea + 2 foliar sprays of nano urea @ 2.5 ml/l) shows highest nutrient content and nutrient uptake among all other treatments; it may be due to 100% urea provided all the nutrient of plant needed with that nano urea can penetrate easily plant system. T 2 (100% Urea), T 4 (85% Urea + 2 foliar sprays of nano urea @ 2.5 ml/l), T 6 (100% Urea + 2 foliar sprays of nano urea @ 1.25 ml/l) are statically at par with that; means nano urea can compensate 15% conventional urea consistent with Gopinath et al. (2025) [ 14] . Data on nutrient use efficiency presented on table 3.6 where AE, PE, ARE, NHI represent like agronomic efficiency, physiological efficiency, apparent recovery efficiency and nutrient harvest index respectively. Agronomic efficiency was highest under T 3 (100% Urea + 2 foliar sprays of nano urea @ 2.5 ml/l) and remained statistically at par with all other treatments except T 8 (70% Urea + 2 foliar sprays of nano urea @ 1.25 ml/l), likely attributable to the higher grain yield recorded under this treatment. Physiological efficiency was highest under T 2 (100% Urea) and was statistically at par with all treatments except T 5 (70% Urea + 2 foliar sprays of nano urea @ 2.5 ml/l) and T 8 , which may be due to limited sink capacity restricting the conversion of additional nitrogen uptake into extra grain yield. Apparent recovery efficiency was highest under T 5 , likely because the reduced conventional urea dose minimized nitrogen losses to the environment, allowing a greater proportion of applied nitrogen to be recovered by the plant; which is consistent with thakur et al. (2022). Nutrient harvest index did not differ significantly among treatments, though it was numerically highest under T 5 .

Correlation between various variables and principal component analysis

Correlation analysis among yield and its attributing parameters, along with nitrogen use efficiency indices, is presented in Figure 3.6. Grain yield showed a highly significant positive correlation with SPAD value (r = 0.822), nitrogen uptake (r = 0.824), agronomic efficiency (r = 0.809), and apparent recovery efficiency (r = 0.738), and significant positive correlation with leaf N content (r = 0.761) and harvest index (r = 0.607). Among the NUE indices, nitrogen uptake showed the strongest association with agronomic efficiency (r = 0.964) and apparent recovery efficiency (r = 0.920), while harvest index was most strongly correlated with nutrient harvest index (r = 0.943). Principal component analysis explained 89.9% of total variance (PC 1 = 78%, PC 2 = 12%; KMO = 0.64), with PC 1 driven by yield, SPAD, leaf N, N uptake, AE, and ARE. T 3 , T 6 , and T 2 clustered on the positive PC 1 axis, reflecting superior overall performance, while T 1 (control) was clearly separated on the negative axis, and T 8 occupied an intermediate position. This separation confirms the consistently poor performance of the unfertilized control, while the clustering of T 4 and T 2 at sample place; suggest that we can replace 15% conventional urea without reducing the yield.

Conclusion

This study evaluated the effects of combined nano urea and conventional urea application on nutrient uptake of winter maize. T 3 (100% urea + two foliar sprays of nano urea @ 2.5 ml/l) recorded the highest nutrient uptake and content, and the highest agronomic efficiency (statistically at par with all treatments except T 8 ). T 4 (85% urea + 2.5 ml/l nano urea) remained at par with T 3 for nutrient uptake and content, and clustered with T 2 and T 3 on the positive PC 1 axis in the PCA biplot, reflecting comparable overall performance. This indicates that nano urea can substitute up to 15% of conventional urea without a significant reduction in yield, nutrient status, or profitability. Postharvest soil nutrient status did not differ significantly among treatments. Collectively, these results support nano urea as a viable component of integrated nitrogen management for improving nitrogen use efficiency while reducing dependence on conventional fertilizer, though long-term studies on its environmental and soil-health implications are warranted before large-scale adoption.

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