Nutrient uptake dynamics, yield and post-harvest soil nutrient status of rabi mustard (Brassica Juncea L.) under conventional and nano-urea-based nitrogen management

Introduction

Oilseed crops are important for India's agricultural economy, nutritional security and edible oil supply. Despite being a major oilseed producer, India depends considerably on edible oil imports to meet domestic demand. Increasing consumption and import dependence emphasize the need to enhance domestic oilseed productivity through improved varieties, efficient agronomic practices, balanced nutrient management and supportive policies (Thapa et al., 2019) [1] . India's total oilseed production reached 429.89 lakh tonnes (42.99 million tonnes) for the 2024-25 crop year, Cultivation area expanded to 304.40 lakh hectares. (Department of Agriculture & Farmers Welfare, 2026) [2] . Rapeseed and mustard production in India was 126.67 lakh tonnes during 2024-25 (PIB, 2025) [3] . Indian mustard (Brassica juncea L.) is one of India's major edible oilseed crops and contributes substantially to domestic edible oil production (Sahoo et al., 2018) [4] . Mustard seed contains about 30-33 per cent oil and 17-25 per cent protein, while its oil is widely used for human consumption and other industrial purposes. Although predominantly cultivated in northern and north-western India, mustard has considerable potential in Telangana, particularly during rabi under irrigated and rice-fallow systems. Rao et al. (2021) [5] reported good mustard productivity under the Northern Telangana Zone, indicating scope for expanding the crop in the region. Nitrogen is a key nutrient governing chlorophyll formation, photosynthesis, biomass production and yield in mustard. However, inefficient application of conventional urea can result in substantial N losses, particularly through ammonia volatilization (Faria et al., 2014) [6] , thereby reducing nitrogen-use efficiency. Difficulty in uniform top-dressing under a developed mustard canopy further emphasizes the need for efficient N-management approaches. Nanotechnology-based fertilizers, particularly nano-N, offer a potential approach for improving nutrient-use efficiency through targeted foliar nutrient delivery (Kundu et al., 2025; Singh, 2017; Seleiman et al., 2021) [7, 8, 9] . Foliar application at critical growth stages may improve crop N status, nutrient acquisition and physiological activity while reducing dependence on soil-applied N. However, the response depends on application concentration and growth stage, and information on nano-N management in mustard under Telangana conditions remains limited. Plant N, P and K uptake and post-harvest soil nutrient analysis provide important information on nutrient acquisition and soil fertility status. However, limited studies have evaluated these parameters together to assess nano-N-based nitrogen management in mustard. Therefore, the present study was conducted to evaluate the effect of foliar nano-N applied at critical growth stages in combination with reduced soil-applied N on N, P and K uptake, yield and post-harvest soil nutrient status of mustard, with the aim of identifying an efficient nitrogen-management strategy for mustard cultivation under the conditions of Telangana.

Materials and methods

Experimental site and soil

A field experiment was conducted during rabi 2021-22 at the Agricultural Research Institute, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad, Telangana, India (17°19′44″ N latitude, 78°23′55″ E longitude and 523 m above mean sea level). The experimental site falls under the semi-arid tropical (SAT) region. The soil was Vertisol, with a pH of 7.9, low organic carbon (0.32%) and available nitrogen (145 kg ha -1 ), medium available phosphorus (27.31 kg ha -1 ) and high available potassium (395 kg ha -1 ). During the crop growth period, weekly mean maximum temperature ranged from 27.4 to 38.4 °C (mean 30.59 °C), while mean minimum temperature ranged from 9.6 to 22.2 °C (mean 16.91 °C) (Fig. 1).

Experimental design and treatments

The experiment consisted of eight nitrogen management treatments, laid out in a Randomized Block Design (RBD) with three replications. The recommended dose of fertilizer (RDF) was 75:90:30 kg N: P 2 O 5: K 2 O ha -1 . The treatments were:

T1: No nitrogen application T2: ½ RDN at sowing + ½ RDN at flowering T3: ½ RDN at sowing + foliar nano-N @ 4 ml L -1 at flowering T4: ½ RDN at sowing + foliar nano-N @ 2 ml L -1 at rosette and flowering T5: ½ RDN at sowing + foliar nano-N @ 2.5 ml L -1 at rosette and flowering T6: ½ RDN at sowing + foliar nano-N @ 3 ml L -1 at rosette and flowering T7: ½ RDN at sowing + foliar nano-N @ 3.5 ml L -1 at rosette and flowering T8: ½ RDN at sowing + foliar nano-N @ 4 ml L -1 at rosette and flowering

Mustard was grown at a spacing of 45 × 20 cm and harvested at 100 DAS.

Fertilizer and nano-N application

Neem-coated urea was used as the source of soil-applied nitrogen, while single super phosphate (SSP) and muriate of potash (MOP) were used as sources of phosphorus and potassium, respectively. The full recommended doses of P and K were applied at sowing. Nano-N was supplied through Nano Urea (liquid) manufactured by Indian Farmers Fertiliser Cooperative Limited (IFFCO), containing 4% N. Foliar sprays were applied at the specified growth stages using a knapsack sprayer. A spray volume of 312 L ha -1 was used for each application.

Observations and nutrient analysis

Plant samples were collected at rosette, flowering and harvest stages for estimation of N, P and K content in samples, analysis was conducted as per the standard procedure followed by Kundu et al. (2026a) [10] . Nutrient uptake was obtained by multiplying nutrient concentrations with dry matter yield (ha -1

) (Kundu et al., 2026b) [11] . Post-harvest soil samples were analysed for ammoniacal-N, nitrate-N and available P and K. Samples were analyzed for N, P and K using the Kjeldahl, vanadomolybdo phosphoric yellow colour and digital flame photometer methods, respectively (Piper, 1966) [12] . Crop yield was recorded from the net plot area and subsequently converted to yield per hectare (kg ha -1 ).

Statistical analysis

The experimental data were subjected to analysis of variance (ANOVA) appropriate for a Randomized Block Design. Treatment means were compared using the Duncan's Multiple Range Test (DMRT) at p ≤ 0.05, and significant differences were expressed using alphabetic notation at the appropriate level of significance following Gomez et al. (1984) [13]

Results and Discussion

Nitrogen uptake

Nitrogen uptake by mustard was significantly influenced by different nitrogen management practices, and the data are presented in Table 1.

At the rosette stage, no significant difference was observed among the N-supplied treatments, as neither split urea application nor nano-urea foliar spray had been applied by this stage. T1 recorded the lowest N uptake. At flowering, the highest N uptake was recorded in T8 (40.0 kg ha⁻¹) with conventional urea at sowing + nano urea spray @ 4 ml L⁻¹, which was on par with T7 (38.3 kg ha⁻¹). T1 recorded the lowest uptake (14.0 kg ha⁻¹). At harvest, T8 (45.2 kg ha⁻¹) was statistically at par with T7 (43.1 kg ha⁻¹) and T2 (43.0 kg ha⁻¹). Higher N uptake was mainly attributed to improved nutrient availability, dry matter accumulation and efficient nutrient absorption under nano-urea application. Qureshi et al. (2018) [14] reported that the smaller particle size and larger surface area of nano-fertilizers enhance nutrient pene tration, uptake and nutrient-use efficiency, thereby promoting crop growth.

Phosphorus uptake

Phosphorus uptake by mustard varied significantly with different nutrient management practices, and the data are presented in Table 2. At the rosette stage, no significant differences were observed among Nsupplied treatments, while T1 recorded the lowest uptake. At flowering, T8 recorded the highest P uptake (15.2 kg ha -1 ), which was statistically similar to T7 (14.3 kg ha -1 ), whereas T1 recorded the lowest (4.7 kg ha -1 ). At harvest, T8 (27.0 kg ha -1 ) recorded the highest P uptake and was at par with T7 (26.3 kg ha -1 ) and T2 (26.0 kg ha -1

). The higher P uptake may be attributed to greater P availability, full application of recommended P at sowing and enhanced nutrient absorption. Van et al. (2013) [15] reported that chitosan nanoparticles enhanced N, P, K, Mg and Ca uptake and photosynthesis, thereby improving the growth of coffee seedlings. Lahari et al. (2021) [16] reported that 50% conventional nitrogen fertilizer combined with foliar application of nano-nitrogen (4 mL L -1

) significantly enhanced N, P, K and Zn uptake by the crop.

Potassium uptake

Potassium uptake was significantly influenced by nutrient management practices and it is depicted in Table 3. At the rosette stage, no significant differences were observed among N-supplied treatments, while T1 recorded the lowest uptake. At flowering, T8 recorded the highest K uptake (24.0 kg ha -1

), followed by T7 (23.0 kg ha -1 ), while T1 recorded the lowest (10.0 kg ha -1 ). At harvest, T8 (36.1 kg ha -1 ) recorded the highest K uptake, which was statistically similar to T7 (35.0 kg ha -1 ) and T2 (33.4 kg ha -1 ). The higher K uptake under T8, T7 and T2 may be attributed to improved K availability and efficient nutrient absorption. Sharma et al. (2022) [17] reported that foliar application of nano-urea @ 4 mL L -1 significantly enhanced K uptake in pearl millet compared with the control. Sahu et al. (2022) [18] reported that application of 75% RDN combined with two foliar sprays of nano-urea significantly increased K uptake. Alimohammadi et al. (2020) [19] similarly reported enhanced K uptake with nano-fertilizer application.

Table 1. Influence of foliar application of nano urea on nitrogen uptake of mustard.

Treatments

Ammoniacal and nitrate soil nitrogen

Table 4 shows that ammoniacal (NH 4 -N) and nitrate (NO 3 -N) nitrogen were significantly influenced by different nutrient management practices. Soil-applied N at sowing and top dressing recorded the highest NH 4 -N (33.0 mg kg -1 ) and NO 3 -N (18.0 mg kg -1 ), followed by T8 (29.0 and 15.5 mg kg -1 , respectively), while T1 recorded the lowest values. The higher soil N under split urea application was mainly due to greater mineral N input, increasing NH 4 -N and NO 3 -N availability. Foliar nano-urea treatments were statistically similar among themselves. Similar findings were reported by Venugopal et al. (2017) [20] .

Available soil phosphorus and potassium

Available soil phosphorus was not significantly influenced by different nutrient management practices, indicating that variation in N sources did not appreciably affect soil P availability. Available soil potassium was also not significantly influenced by different nutrient management practices, indicating that the different N management practices had no appreciable effect on soil K availability.

pH, EC, and organic C

Data regarding soil revealed that soil pH did not vary significantly due to different nitrogen management practices. It could be because of the short term of the experiment which may not be enough to bring significant changes in soil chemical property like pH. The data on electrical conductivity presented in Table 5, revealed that EC of soil was not significant influenced due to different nitrogen management practices. Perusal of the data in Table 5 on organic carbon content in soil presented in table revealed that variations in organic carbon in soil were found to be non-significant due to various nitrogen management practices.

Seed yield

The influence of nano-N and RDF on mustard seed yield is presented in (Table 6). The highest seed yield (1126 kg ha -1 ) was recorded with ½ RDN at sowing + nano-N @ 4 ml L -1 at rosette and flowering, which was statistically at par with ½ RDN + nano-N @ 3.5 ml L -1 at rosette and flowering (985 kg ha -1 ) and ½ RDN at sowing + ½ RDN through urea at flowering (975 kg ha -1 ). Application of nano-N @ 3 ml L -1 at rosette and flowering produced 885 kg ha -1 , comparable with the recommended N treatment (975 kg ha -1 ), indicating the potential of two nano-N sprays to partially substitute the 50% RDN top dressing. Lower nano-N concentrations of 2 and 2.5 ml L -1 resulted in 694 and 704 kg ha -1 , respectively, while a single spray of nano-N @ 4 ml L -1 at flowering produced only 529 kg ha -1 . Thus, two foliar applications at rosette and flowering were more effective than a single application at flowering. The control without external N produced 367 kg ha -1 . The higher seed yield under nano-N treatments may be associated with improved growth and yield attributes, particularly siliquae m -2 , seed weight siliqua -1 and test weight, through enhanced N uptake, photosynthetic activity and translocation of assimilates towards reproductive sinks. Drostkar et al. (2016) [21] reported that foliar application of NPK nano-fertilizers improved growth, yield and yield attributes in chickpea. Tarafdar et al. (2012) [22] reported that foliar application of nano-fertilizers significantly enhanced crop yield. Kumar et al. (2021) [23] reported that 50% reduction in nitrogen fertilizer combined with two foliar sprays of nano-nitrogen produced higher yield in mustard. Table 6. Influence of foliar application of nano urea on yield of mustard.

Treatments

T1: No Nitrogen application 367 e T2: 1 /2RDN at sowing + 1 /2 RDN at flowering 975 ab T3: 1 /2RDN at sowing + foliar spray of nano-N @ 4 ml L -1 at flowering 529 d T4: 1 /2RDN at sowing + foliar spray of nano-N @ 2 ml L -1 at rosette stage and flowering 694 c T5: 1 /2RDN at sowing + foliar spray of nano-N @ 2.5 ml L -1 at rosette stage and flowering 704 c T6: 1 /2RDN at sowing + foliar spray of nano-N @ 3 ml L -1 at rosette stage and flowering 885 b T7: 1 /2RDN at sowing + foliar spray of nano-N @ 3.5 ml L -1 at rosette stage and flowering 985 ab T8: 1 /2RDN at sowing + foliar spray of nano-N @ 4 ml L -1 at rosette stage and flowering 1126 a SEm± 52 CD (p = 0.05) 157 CV% 11 Seed yield showed a positive relationship with N uptake at both flowering and harvest stages, with a stronger association at harvest (R 2 = 0.9355) than at flowering (R 2 = 0.6745). This indicates that N uptake at harvest was more strongly associated with seed yield under different nitrogen management practices.

Conclusion

The study demonstrated that integrating foliar nano-urea with reduced soil-applied nitrogen can improve nutrient acquisition and productivity of rabi mustard. Among the nitrogen management treatments, ½ RDN applied at sowing followed by nano-urea @ 4 ml L -1 at rosette and flowering (T8) recorded the highest N, P and K uptake at harvest (45.2, 27.0 and 36.1 kg ha -1 , respectively) and maximum seed yield (1126 kg ha -1 ). The conventional split-N treatment (T2) also performed well, particularly in maintaining higher residual soil mineral nitrogen, with 33.0 mg kg -1 ammoniacal-N and 18.0 mg kg -1 nitrate-N after harvest. However, the higher nutrient uptake and productivity under T8, together with comparatively lower residual mineral N, suggest greater utilization of applied nitrogen by the crop. Nitrogen management did not significantly alter post-harvest soil available P and available K, indicating no measurable changes in these soil nutrient pools during the experimental period. Thus, under the conditions of the present study, supplementing ½ RDN applied at sowing with nano-urea @ 4 ml L -1 at rosette and flowering (T8) was an effective nitrogen management strategy for improving nutrient uptake and mustard productivity. However, the findings should be validated across seasons, locations and soil types before making broader recommendations.

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