Growth response of blackgram (Vigna mungo L.) to nano DAP application

Introduction

Blackgram (Vigna mungo L.) is an important grain legume of the family Fabaceae and is commonly known as urd bean in India. It is the third most important pulse crop in the country and is valued for its high nutritional content, containing 22.23% protein, 48.0% carbohydrates and appreciable amounts of minerals and vitamins (Asaduzzaman et al., 2010) [1] . Being a leguminous crop, it forms a symbiotic association with Rhizobium bacteria, which fixes atmospheric nitrogen and contributes about 22.1 kg N ha -1 , saving nearly 59 thousand tonnes of urea annually (Jat et al., 2017) [4] . Despite its importance, blackgram productivity remains low due to improper nutrient management. Excessive use of conventional fertilizers such as urea and DAP has resulted in poor nutrient use efficiency, soil degradation and environmental pollution, with substantial losses of applied nutrients (Raliya et al., 2013) [9] . Nanofertilizers have emerged as an efficient alternative to conventional fertilizers because they enhance nutrient use efficiency through controlled nutrient release, improve crop growth and reduce nutrient losses and environmental hazards (Yadav et al., 2023) [14] . Among these, IFFCO developed liquid Nano DAP containing 8% nitrogen and 16% phosphorus, which effectively supplies nitrogen and phosphorus through foliar application (Khemshetty et al., 2024) [5] . Nano DAP improves nutrient availability, corrects nutrient deficiencies in standing crops and enhances crop productivity while minimizing adverse effects on the environment (Chundawat et al., 2025) [2] . Keeping the above points into consideration, the present study was undertaken to evaluate the "Growth Response of Blackgram (Vigna mungo L.) to Nano DAP application."

Materials and Methods

The field experiment was conducted during rabi, 2025-26 at the College Farm, Agricultural College, Polasa, Jagtial, Telangana, India, to evaluate the "Growth Response of Blackgram (Vigna mungo L.) to Nano DAP application." The experiment comprised of eight treatments:-T 1 -Control, T 2 -100% RDF (20:50:0 NPK), T 3 -50% RDF + seed treatment with Nano DAP (3ml kg -1 ) + 1 spray of Nano DAP (3ml l -1 ) at vegetative stage, T 4 -50% RDF+ seed treatment with Nano DAP (3ml kg -1 ) + 1 spray of Nano DAP (3ml l -1 ) at flowering stage, T 5 -50% RDF + seed treatment with Nano DAP (3ml kg -1 ) +2 sprays of Nano DAP (3ml l -1 ) at vegetative and flowering stage, T 6 -100% RDF + seed treatment with Nano DAP (3ml kg - 1 ) + 1 spray of Nano DAP (3 ml l -1 ) at vegetative stage, T 7 -100% RDF + seed treatment with Nano DAP (3ml kg -1 ) + 1 spray of Nano DAP (3ml l -1 ) at flowering stage, T 8 -100% RDF + seed treatment with Nano DAP (3ml kg -1 ) + 2 sprays of Nano DAP (3ml l -1 ) at vegetative stage and flowering stage. These treatments were evaluated under a randomized block design (RBD) with three replications. The experiment field was characterized by well drained sandy clay loam soil with a composition of 62.8% sand, 6.5% silt and 29.85% clay. The initial soil chemical properties included a neutral pH of 7.86, electrical conductivity of 0.21 dS m -1 . The organic carbon content was moderate (0.50%). Prior to sowing, the soil was low in available nitrogen (198.7 kg ha -1 ), medium in phosphorus (21.2 kg ha -1 ) and available potassium (254.1 kg ha -1 ). During the experimental period, the average maximum and minimum temperatures were 31.3°C and 13.3°C, respectively. The crop variety used was blackgram variety 'MBG-1070', which has a duration of 75-80 days. Sowing was done at a spacing of 30 cm × 10 cm using a seed rate of 20-25 kg ha -1 on 17 th October, 2025. The recommended dose of fertilizers (20:50:0 kg ha -1 of N, P 2 O 5 , and K 2 O) was applied using urea and SSP as basal dose i.e., at the time of sowing. Foliar application of Nano DAP was given by knapsack sprayer at 30 and 45 days after sowing. Data was recorded from five plants selected randomly from each treatment. Data on growth parameters such as plant height, number of branches, dry weight of root nodules, dry matter production, leaf area index and SPAD chlorophyll meter readings of blackgram were analysed statistically using ANOVA.

Results and Discussion

Effect of Nano DAP treatments on growth parameters of blackgram 1. Plant height (cm) Plant height was significantly influenced by application of Nano DAP at 30, 45 DAS and at harvest in blackgram crop. At all the growth stages, the maximum plant height was recorded in treatment T 8 -100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 2 sprays of Nano DAP (3 ml l -1 ) at vegetative and flowering stages, recording 24.4, 33.8 and 41.8 cm at 30, 45 DAS and at harvest, respectively. At 30 and 45 DAS, T 8 is on par with T 6 -100% RDF + seed treatment with Nano DAP (3ml kg -1 ) + 1 spray of Nano DAP (3ml l -1 ) at vegetative stage, which recorded 23.6, 31.9 cm respectively. However, at harvest, T 8 was significantly superior to all other treatments. The lowest plant height of 17.9, 24.4 and 31.9 cm at 30, 45 DAS and at harvest was recorded in T 1 (Control) respectively. The increased plant height under T 8 may be attributed to the combined effect of 100% RDF along with Nano DAP seed treatment and two foliar sprays at vegetative and flowering stages, which ensured a continuous supply of nutrients throughout the crop growth period. Adequate availability of nitrogen and phosphorus enhanced cell division, cell elongation, chlorophyll synthesis and photosynthetic efficiency, resulting in vigorous vegetative growth and taller plants. These results are in agreement with those reported by Girigoud et al. (2023) [3] and Shete et al. (2024) [11] .

Number of branches plant -1

The number of branches plant -1 was significantly influenced by the different Nano DAP treatments at 30 DAS, 45 DAS and at harvest. At all the growth stages treatment T 8 -100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 2 sprays of Nano DAP (3 ml l -1 ) at vegetative and flowering stages, recorded maximum number of branches plant -1 of 3.5, 5.4 and 7.5 at 30, 45 DAS and harvest, respectively. At 30 DAS and 45 DAS, treatment T 8 was on par with T 6 -100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray of Nano DAP (3 ml l -1 ) at the vegetative stage, which recorded 3.2 and 5.2 branches plant -1 , respectively. At harvest, T 8 was significantly superior to all other treatments. The lowest number of branches plant -1 was observed in T 1 i.e., Control, with 2.4, 3.4 and 5.3 branches plant -1 at 30, 45 DAS and harvest, respectively. The increase in number of branches may be due to foliar application of Nano DAP at vegetative and flowering stages improved nutrient use efficiency and photosynthetic activity, resulting in vigorous vegetative growth and increased branch formation. Results analogous to this have also been reported by Sruthy et al. (2023) [12] and Maurya et al. (2024) [7] .

The dry weight of root nodules at the flowering stage was significantly influenced by the different Nano DAP treatments. Among the treatments, T 8 -100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 2 sprays of Nano DAP (3 ml l -1 ) at vegetative and flowering stages, recorded the highest dry weight of root nodules (88.67 mg plant -1 ). This treatment is on par with T 6 (87.00 mg plant -1 ), T 7 (82.33 mg plant -1 ), T 2 (81.20 mg plant - 1 ). The lowest dry weight of root nodules (60.60 mg plant -1 ) was observed in T 1 . The increased dry weight of root nodules under T 8 may be attributed to the synergistic effect of recommended fertilizer application along with Nano DAP seed treatment and foliar nutrition, which provided an adequate supply of phosphorus required for nodule initiation, development and functioning. Phosphorus plays a crucial role in energy transfer and metabolic activities associated with nitrogen fixation, thereby promoting the formation of larger and more active nodules. These findings are in close agreement with the reports of Kumar et al. (2022) [6] .

The dry matter production was significantly influenced by the different Nano DAP treatments at 30 DAS, 45 DAS and at harvest. At all growth stages, the highest dry matter production was recorded in T 8 -100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 2 sprays of Nano DAP (3 ml l -1 ) at vegetative and flowering stages, recording 359, 881 and 4183 kg ha -1 at 30 DAS, 45 DAS and at harvest, respectively. At 30 DAS and 45 DAS, treatment T 8 was on par with T 6 -100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray of Nano DAP (3 ml l -1 ) at the vegetative stage, which recorded 323 and 810 kg ha -1 , respectively. However, at harvest, T 8 recorded significantly higher dry matter production than all other treatments. The lowest dry matter production was recorded in T 1 i.e., Control, recording 201, 606 and 2480 kg ha -1 at 30 DAS, 45 DAS and at harvest, respectively. The foliar application of Nano DAP at critical growth stages might have further improved nutrient-use efficiency and reduced nutrient losses, thereby enhancing biomass production. Concordant result was reported by Sarika et al. (2025) [10] .

Leaf area index

Leaf area index was significantly influenced by the different Nano DAP treatments at 30 DAS, 45 DAS and at harvest. At all growth stages, the highest leaf area index was recorded in T 8 -100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 2 sprays of Nano DAP (3 ml l -1 ) at vegetative and flowering stages, recording 0.71, 3.94 and 2.89 at 30 DAS, 45 DAS and harvest, respectively. At 30 and 45 DAS, treatment T 8 was statistically on par with T 6 , which recorded leaf area index values of 0.70 and 3.81, respectively. However, at harvest, T 8 registered a significantly higher leaf area index compared to all the other treatments. The lowest leaf area index was recorded in T 1 (Control), with the values 0.37, 2.34 and 1.54 at 30 DAS, 45 DAS and harvest, respectively. The superior LAI under T 8 might be attributed to the combined effect of RDF, seed treatment and foliar application of nano DAP, which ensured adequate and continuous nutrient supply throughout the crop growth period. The increase of leaf area index in T 8 is due to enhanced availability of nitrogen and phosphorus which promoted vigorous vegetative growth, increased leaf initiation and expansion, higher chlorophyll synthesis and improved photosynthetic activity, leading to greater canopy development. Similar findings were recorded by Khemshetty et al. (2024) [5] .

SPAD chlorophyll meter readings (SCMR)

SPAD chlorophyll meter readings were significantly influenced by the different Nano DAP treatments at 30 and 45 DAS. The highest SPAD meter readings was recorded with T 8 -100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 2 sprays of Nano DAP (3 ml l -1 ) at vegetative and flowering stages recording 40.9, 46.6 at 30 and 45 DAS respectively. At 30 and 45 DAS, T 8 was on par with T 6 -100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray of Nano DAP (3 ml l -1 ) at the vegetative stage, which recorded 39.2, 44.0 respectively. The lowest SPAD chlorophyll meter readings were recorded in T 1 (Control) with values of 31.4 and 36.4 at 30 and 45 DAS respectively. Foliar application of Nano DAP at critical growth stages could have facilitated rapid nutrient absorption and utilization, thereby maintaining higher chlorophyll content in leaves. Similar findings were observed by Venkatarao et al. (2025) [13] . 5.8 T3-50% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray Nano DAP (3 ml l -1 ) at Vegetative stage.

3.0 4.6 6.3 T4-50% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray Nano DAP (3 ml l -1 ) at Flowering stage.

2.9 3.9 6.0 T5-50% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 2 sprays Nano DAP (3 ml l -1 ) at Vegetative and Flowering stage.

3.0 4.7 6.8 T6-100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray Nano DAP (3 ml l -1 ) at Vegetative stage. 3.2 5.2 6.7 T7-100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray Nano DAP (3 ml l -1 ) at Flowering stage.

3.1 4.8 6.5 T8-100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 2 sprays Nano DAP (3 ml l -1 ) at Vegetative and Flowering stage. 75.63 T4 -50% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray Nano DAP (3 ml l -1 ) at Flowering stage.

71.50 T5-50% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 2 sprays Nano DAP (3 ml l -1 ) at Vegetative and Flowering stage.

77.97 T6-100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray Nano DAP (3 ml l -1 ) at Vegetative stage.

87.00 T7 -100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray Nano DAP (3 ml l -1 ) at Flowering stage.

82.33 T8-100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 2 sprays Nano DAP (3 ml l - 36.0 41.2 T3 -50% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray Nano DAP (3 ml l -1 ) at Vegetative stage.

35.7 40.9 T4 -50% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray Nano DAP (3 ml l -1 ) at Flowering stage.

34.1 39.1 T5 -50% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 2 sprays Nano DAP (3 ml l -1 ) at Vegetative and Flowering stage.

35.6 41.8 T6 -100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray Nano DAP (3 ml l -1 ) at Vegetative stage.

39.2 44.0 T7 -100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 1 spray Nano DAP (3 ml l -1 ) at Flowering stage.

35.3 42.1 T8 -100% RDF + seed treatment with Nano DAP (3 ml kg -1 ) + 2 sprays Nano DAP (3 ml l -

Conclusion

Plant height, number of branches, dry weight of root nodules, dry matter production, leaf area index, SPAD chlorophyll meter readings were significantly influenced by different Nano DAP treatments. Among the treatments T 8 recorded the highest values for all growth parameters and was found to be on par with T 6 . This is due to improved phosphorus availability and sustained nutrient release through Nano DAP resulting in better vegetative growth, chlorophyll synthesis and overall crop development.

Acknowledgement

AcknowledgementI express sincere gratitude to the Department of Agronomy, Agricultural College, Polasa, Jagtial, PJTAU, for providing the facilities and guidance required for this study.

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