Comparative evaluation of seed priming and foliar application of nano DAP on growth, yield and quality of blackgram (Vigna mungo L. Hepper)

Introduction

Pulses are the most important food crops after cereals. They belong to family Fabaceae and commonly called as grain legumes. Pulses contain two to three times more protein than cereals ranging approximately between 20 and 40 per cent (Arora, 1989) [5] . Among all the pulses, one of the important pulse crops in India is blackgram (Vigna mungo L.), a member of the genus Vigna and Papilionaceae subfamily of the Fabaceae family. This self-pollinating annual legume crop (2n = 22) is commonly called "urd bean" and has been evolved from wild plant Phaseolus sublobatus. It is believed that blackgram originated in India, where it is the most popular and highly valued grain legume, as supported by Chatterjee and Bhattacharya (1986) [9] . It is cultivated in all three seasons in India, viz., Kharif, Rabi and summer. This crop is distributed mainly in tropical to subtropical countries and it is more important to India because for the predominant vegetarian population. It fits well in mixed cropping and crop rotation system due to its shorter life cycle. Blackgram has the ideal ratio of all nutrients, viz., protein (25-26%), carbohydrates (60%), fat (1%) as well as minerals, amino acids and vitamins (Jadhav et al., 2017) [15] . It is used in the preparation of dishes like dal, curries, soups, sweets and snacks. It is also used as nutritive fodder, especially for milch cattles. India is the world's largest producer of Black gram, contributing 70 per cent of the global production, followed by Myanmar and Pakistan. India produces approximately 2 million tons of blackgram from around 4 million hectares, with an average yield of 598 kg ha -1 during 2023-24. In India, 80 per cent of blackgram cultivation occurs during the Kharif season and nearly 20 per cent during the Rabi season. Blackgram accounts for approximately 10 per cent of the total pulse production in India, with more than 90 per cent of its production coming from ten states: Maharashtra, Karnataka, Madhya Pradesh, Gujarat, Uttar Pradesh, Jharkhand, Telangana, Odisha, Andhra Pradesh and Tamil Nadu (Anon, 2024). Despite of its importance, its productivity is low in India. The low productivity of blackgram in the country can be due to several factors. These include the lack of quality seeds and short-duration varieties, growing in marginal and less fertile soil with minimal inputs and no control over pests and diseases, growing in conditions of moisture stress and storing in unfavourable conditions. Various other reasons like physiological, biochemical and inherent crop-related factors, as well as the fact that it is mainly grown in rainfed areas with inadequate management practices (Mahala et al., 2001) [20] . Among all the yield limiting factors, fertility management is imperative to ensure better crop production on exhausted soils. In pulse crops, the use of conventional fertilizers often faces several challenges that limit their effectiveness. A large amount of nutrients applied through these fertilizers is not fully utilized by plants, as they are commonly lost through processes such as leaching, runoff, volatilization and fixation in the soil. As a result, only a small portion of the nutrients becomes available to the crop, leading to lower nutrient use efficiency and reduced crop productivity. This not only increases production costs for farmers but also contributes to environmental concerns such as soil nutrient imbalance and water pollution. Smart delivery technologies that support long-term soil health and agricultural output, such as nanotechnology and nano-fertilizers, can help overcome all of these limitations (Lal, 2008) [19] . Nano fertilizer is an important input in agriculture to improve crop growth, yield and quality parameters with increased nutrient use efficiency, reduction in wastage of fertilizers and cost of cultivation. These fertilizers are applied either to soil, seeds or leaves. Applying macronutrients at the nano-scale to seeds via seed priming presents several benefits including enhanced nutrient absorption during seedling development, minimized nutrient runoff, increased seedling vitality and optimized resource utilization. Priming of nanomaterial fertilizer particles hold the material more strongly due to higher surface energy than the conventional fertilizers and thus helps in controlled release to meet the soil and crop demand, preventing rapid dissolution and minimizing losses (Manjunatha et al., 2016) [23] . Foliar application promotes the direct entry of nutrients into the plant system, thus reducing the wastage of fertilizer and correcting nutrient deficiencies. Hence, foliar application of nano fertilizers leads to higher nutrient use efficiency (Mahil and Kumar, 2019) [21] . Phosphorus (P) is among the most critical nutrients for pulses. Nano DAP, a liquid fertilizer developed by Indian Farmers Fertiliser Cooperative (IFFCO). It is applied at critical crop growth stages, that effectively fulfils the phosphorus and nitrogen requirement and leads to higher crop yield and quality in comparison to conventional DAP. It contains nanoscale phosphorus and nitrogen particles; compared to conventional granular DAP; it has about 10,000 times more surface area. Particle size (<100 nm) of P-fertilizers greatly influences their agronomic effectiveness. Nano DAP contains 8 per cent nitrogen and 16 per cent phosphorus compared to 18 and 46 per cent, respectively, in conventional DAP. In this study nano DAP is applied by two different methods, to evaluate the effectiveness of Seed Priming and Foliar Application of Nano DAP on Growth, Yield and Quality of Blackgram (Vigna mungo L. Hepper).

Materials and Methods

The field experiment was conducted at Zonal Agricultural and Horticultural Research Station (ZAHRS) of College of Agriculture, Navile, Shivamogga during Kharif 2024. The experimental location is situated between 13° 58' to 14° 1' N latitude and from 75° 34' to 75° 42' E longitude, at an elevation of 615 meters above mean sea level. It lies in the Southern Transition Zone (Zone-7) of Karnataka. The soil of the experimental site was sandy loam in texture with pH (6.19), EC (0.32 dS m -1 ), organic carbon (4.98 g kg -1 ), low available nitrogen (238 kg ha -1 ), high phosphorus (57.64 kg ha -1 ) and medium potassium (226.63 kg ha -1 ). The actual total rainfall of the station during cropping period was 644.20 mm. This research experiment was laid out in Randomized Complete Block Design with eight treatments and replicated thrice. The treatments details consist of T1: Absolute control, T2: RDF (12.5: 25: 25 kg ha -1 of N, P2O5, K2O), T3: 75% N and P + Seed priming with Nano DAP @ 3 ml/l, T4: 100% N and P + Seed priming with Nano DAP @ 3 ml/l, T5: 75% N and P + one foliar spray with Nano DAP @ 4 ml/l at 30 DAS, T6: 100% N and P + one foliar spray with Nano DAP @ 4 ml/l at 30 DAS, T7: 75% N and P + Seed priming with Nano DAP @ 3 ml/l + one foliar spray with Nano DAP @ 4 ml/l at 30 DAS, T8: 100% N and P + Seed priming with Nano DAP @ 3 ml/l + one foliar spray with Nano DAP @ 4 ml/l at 30 DAS. Recommended farm yard manure and potassium were applied commonly for all the treatments, except absolute control (T1). Blackgram seeds were primed using the nano-DAP at the rate of 3 ml l -1 . Treatment seeds were primed for 5 hours with water in seed to solution ratio of 1:3 (w/v) as per the treatment needs. Later, the primed seeds were shade dried then sowing was done. Variety used was LBG-791 (Suraksha), which is suitable for cultivation under both rainfed and irrigated conditions. This variety matures in 75-80 days and harvested at a time (synchronous maturity). From five tagged plants, growth parameters (at 30 and 60 DAS) and yield attributes (at harvest) were recorded. Crude protein content was calculated by multiplying the nitrogen content with a correction factor 6.25. The protein yield was estimated by using the formula given below

Results and Discussion

Growth parameters

The plant growth parameters of black gram increased with the advancement of crop age irrespective of the treatments (Table 1). A significant variation was observed among different treatments due to application of nano DAP. Between seed priming and foliar application of nano DAP, seed priming treatments recorded better performance over foliar spray, with both 75 and 100 per cent recommended dose of N and P, at 30 and 60 DAS. At 30 DAS, seed priming with 100 per cent recommended dose of N and P treatment (T8) recorded higher growth parameters such that plant height (34.82 cm), number of branches (4.27), leaf area (550.50 cm 2 ) and dry matter production (5.49 g plant -1 ), over non primed treatments. Foliar application was carried out at 30 DAS and parameters were recorded at 60 DAS. At 60 DAS, Application of nano DAP (Seed priming + Foliar spray) along with 100 per cent N and P (T8) was recorded significantly enhanced the growth parameters, such as plant height (46.61 cm), number of branches (10.87), leaf area (840.42 cm 2 ) and dry matter production (15.67 g plant -1 ). Between seed priming and foliar spray, at 100 per cent N and P, seed priming (T4) treatment recorded comparatively higher growth parameters, viz., plant height (42.74 cm), number of branches (9.93), leaf area (757.84 cm 2 ) and dry matter production (14.07 g plant -1 ). whereas foliar spray treatment recorded comparatively lower growth parameters, viz., plant height (42.25 cm), number of branches (9.85), leaf area (740.47 cm 2 ) and dry matter production (12.46 g plant -1 ), same trend followed at 75 per cent recommended dose also. Significantly lowest plant growth parameters were recorded in absolute control (T1). Growth parameters were significantly influenced by the application of nano DAP as seed priming and foliar spray along with basal conventional fertilizers. Because, phosphorus (P) is an essential nutrient both as a part of several key plant structural compounds and in the numerous biochemical reactions in plants. P is noted especially for its role in capturing and converting the sun's energy into useful plant compounds; thus, P is essential for the general health and vigour of plants (Badini et al., 2015) [7] . Combined application of conventional DAP along with nano DAP seed priming and foliar spray at earlier vegetative stage favoured better crop growth by absorbing through stomata leads to increased enzymatic activity in leaves, which converts nano nitrogen into protein, amino acids and growth hormones, this encourages cells growth, might be responsible for the better plant height (Samui et al., 2022) [27] . The improvement in plant height under optimal nano DAP seed priming can be ascribed to enhanced seedling vigour. This enhanced vigour might be associated with quicker germination and better early growth traits of seedlings. Such responses could be linked to the efficient supply and utilization of phosphorus, which is vital for early seedling establishment. Comparable results were also reported by Niu et al. (2013) [24] and Ashoknarayanan et al. (2021) [6] in blackgram. Similar findings were also reported by Kumar et al. (2016) [18] , Akshay (2021) [2] in rice, Girigoud et al. (2023) [14] in pigeonpea, Khemshetty et al. (2024) [17] and Sarika et al. (2025) [28] in chickpea.

Yield parameters

The yield and yield attributes of blackgram were significantly influenced by the application of conventional fertilizers and nano DAP by two different methods of application as depicted in Table 2. Results revealed that, the treatment receiving 100 per cent N and P as a basal along with seed priming using nano DAP @ 3 ml l -1 along with foliar application of nano DAP @ 4 ml l -1 at 30 DAS (T8) recorded significantly higher seed yield per plant (12.03 g), seed yield (1111 kg ha -1 ) and haulm yield (2431 kg ha - 1 ) biological yield (3542 kg ha -1 ). In combination with 100 per cent N and P, higher seed yield (1023 kg ha -1 ), haulm yield (2238 kg ha -1 ) and biological yield (3261 kg ha -1 ) were recorded in the treatment with seed priming (T4), compared to foliar spray (T6) treatment. 75 per cent recommended N and P also followed the same trend. Further the treatments involving application of nano DAP either seed priming or foliar spray were recorded higher yield compared to RDF (T2). Test weight and harvest index were recorded as non significant. Overall, the results indicated that seed priming with nano DAP was more effective than foliar spray. Treatments involving nano DAP application recorded higher yield parameters than RDF. Significantly lowest yield parameters were recorded in absolute control treatment (T1). This increased yield might be due to integration of nano DAP that results in better nutrient uptake supported good plant growth, including height, dry matter build-up and important processes like photosynthesis. This helped the plants to produce more food and move it to the useful parts such as seeds. As a result, more assimilates were shifted to seeds, which increased biomass and yield traits. Similar results were also reported by Kailas et al. (2017) [16] and Choudhary et al. (2018) [10] . Using both conventional DAP and nano DAP, as a seed priming at sowing and as a foliar spray during the reproductive phase, helps the plant to produce more photosynthates and move them to the developing pods. This increase in photosynthesis results in more sugars and starches, which are then effectively translocated to the pods. As a result, the pods develop better, finally higher pod weight and seed weight. These results are in line with the findings of Manjili et al. (2014) [22] and Abdelghany et al. (2022) [1] . El-Azizy et al. (2021) [11] found increased biological yield in broad bean due to application of nano phosphorus. Sachin (2023) [26] , in their study found increased seed yield with nano DAP seed priming in maize over RDF alone.

Quality parameters

Table . 3 presents the data showing significant differences in crude protein content and protein yield among the various treatments as influenced by nano DAP application. The highest crude protein content (25.50%) and protein yield (286.05 kg ha - 1 ) were achieved in the treatment T8, closely followed by T7, where nano DAP was applied both as seed priming and foliar spray. In the treatments nano DAP application with 100 per cent N and P (T4 and T6), seed priming treatment (T4) recorded comparatively higher crude protein content (23.75%) and protein yield (242.87 kg ha -1 ), over foliar spray treatment (T6), which recorded crude protein content (23.63%) and protein yield (240.69 kg ha -1 ). The treatments with seed priming produced better quality parameters over foliar spray, while foliar spray treatments showed improvement over RDF (T2) and absolute control (T1) but remained lower than seed priming. Among all the treatments, treatments involving nano DAP application recorded good quality parameters over RDF and absolute control treatment. Significantly lowest crude protein content (15.81%) and protein yield (80.95 kg ha -1 ) were recorded in absolute treatment (T1). Nitrogen plays a key role in building proteins and phosphorus helps in forming important coenzymes needed for protein making. Together, they improved the protein content and protein yield. Similar results were reported by El-Ghany et al. (2021) [12] , Farhana et al. (2022) [13] and Bhavyashree (2024) [8] . Amirnia et al. (2014) [3] reported that application of nanoparticles in a number of crops has evidenced for enhanced physiological activities, gene expression and protein level indicating their potential use in crop improvement. Yacoub et al. (2020) [29] reported improved protein content in soybean due to application of nano P particles. Seed priming with nano DAP helps in absorbtion of nitrogen and phosphorus more easily at the early growth stage because the nutrients are present in very small nano-sized particles. This improves root growth and nitrogen fixation in the plant, which helps in producing more amino acids and finally increases the protein content in blackgram seeds. Sharifi et al. (2016) [25] revealed that seed priming and foliar spray of nano fertilizers significantly increased the crude protein content.

Conclusion

The present investigation showed that application of nano DAP significantly influenced growth, yield and quality of blackgram.

Between seed priming and foliar spray of nano DAP, seed priming of nano DAP treatments performed better than foliar application in enhancing the crop performance. Application of 100 per cent recommended nitrogen and phosphorus as basal along with nano DAP seed priming @ 3 ml l -1 followed by one foliar spray of nano DAP @ 4 ml l -1 at 30 DAS recorded higher growth and yield parameters of blackgram. Since seed priming is cost effective (lower dose and application cost) and easy application, it is found to be effective.

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