Influence of Nano Urea on Growth Yield and Nutrient Uptake of Blackgram

The use of modern agricultural inputs in the second half of the twentieth century has significantly increased agricultural production in the majority of countries. At the same time, agricultural output has been met with new hurdles. Nonetheless, the world has seen the emergence of innovative technology to solve production constraints and sustain agricultural production. In this context, nanotechnology has a growing role in crop production with strong promise to alter the existing state of fertilizer use with environmental safety, ecological sustainability and economic stability (Nandhakumar et al., 2023). It reduces soil pollution as well as potential negative consequences when conventional mineral fertilizers are used (Velmurugan et al., 2022). Nano fertilizers (NF) are more efficient and effective than conventional fertilizers because of their positive effects on the quality of food crops, reduce stresses that occur to the plant, small applied quantities and costs, fast absorption by plant cells and penetration of cells and fats of transport and representation within plant tissue (Hayyawi et al., 2020).
 
Fertigation is one of the most effective ways to manage water and nutrients while also being more efficient for food production and soil fertility. It is an excellent approach for lowering the cost of fertilizer application. One of the most important benefits of this technology is the application of nutrients in proportion to the growth of the crop to meet nutritional needs with great accuracy and then achieve a high crop yield.
 
Foliar nutrition refers to the application of nutrients to the vegetative part at specific concentrations and times so that the plant can absorb them through the leaf’s stomata or through the cell walls and membranes to participate in vital plant processes. This enhances the vegetative and qualitative aspects to prevent circumstances that restrict the availability of plant nutrients in the soil (Surender Kumar and Kuldeep, 2024).
 
Black gram (Vigna mungo L.) is a widely cultivated legume with significant culinary and nutritional value. In India, it is planted as a single crop, intercrop, or fallow crop in both rainfed and irrigated environments. Globally, India is the major producer and user of blackgram, accounting for 70% of total production. It accounts for roughly 19% of the total pulse acreage and 23% of overall pulse production in India (MoA, 2021). The total area under pulses in India is about 4.2 million hectares, with a yield of 2.34 million tonnes and a productivity of 557 kg ha^-1 (DMI, 2021). In Tamil Nadu, blackgram is grown in 2.69 lakh hectares with a production of 4.07 lakh tonnes and an average productivity of 863 kg ha^-1 (MoA, 2024).
 
This low yield is linked to numerous factors, including low yielding cultivars, cultivation in marginal soils, primarily as rainfed crops, poor management practices and low fertilizer usage efficiency by crops. As a result, boosting pulse output requires higher productivity and efficiency, which improves blackgram productivity and minimizes environmental problems. Nano urea (liquid) for agricultural usage delivers nutrients to plants more efficiently. At the same time, it is critical to understand its efficacy and advantages over traditional fertilizer materials. This is critical to reducing chemical fertilizer consumption and increasing nano urea without sacrificing crop production. Hence, the present study a pot culture experiments were conducted to investigate the effect of nano urea (liquid) on blackgram productivity.

The pot culture experiment was conducted at north farm of Vanavarayar Institute of Agriculture, Manakkadavu, Pollachi during the Kharif (June-September) season of 2022 and 2023. The soil of the experimental was well drained sandy clay loam in texture. The initial soil sample was analyzed for chemical properties nearly alkaline in soil reaction (pH 7.91), low in organic carbon (0.68%), available N (276 kg ha^-1; medium), available P (15 kg ha^-1; medium) and available K (290 kg ha^-1; high). Nutrient sources were urea, single super phosphate, muriate of potash and nano urea to fulfill the requirement of nitrogen, phosphorus and potassium. The experiment was laid out in completely randomized block design (CRBD) with eight treatments and replicated thrice. The treatment details are T₁ - Recommended Dose of Fertilizer (RDF) (25:50:25 kg ha^-1) (CPG, 2020), T₂ - Nano-Urea (Liquid) 1.25 litres ha^-1 as Foliar Spray (FS) (IFFCO) + P (Phosphorus) and K (Potassium) RDF, T₃ - Nano-Urea (Liquid) 1.25 litres ha^-1 as Soil application (Basal Dose) + PandK RDF, T₄ - Nano-Urea (Liquid) 50% as basal + 50% as FS + P and K RDF, T₅ - RDF + Urea 1% FS, T₆ - RDF (50% N as Urea Basal Dose) + Urea 1 % (FS), T₇ - RDF (50% N as Urea Basal Dose) + Nano-Urea (Liquid) 50% (FS) and T₈ - Control (No NPK). The foliar spraying of Nano urea was applied once in 15 days.

The growth parameters were recorded at critical stages of blackgram. These parameters were statistically analyzed using analysis of variance (ANOVA) as applicable to completely randomized block design. The black gram (Vigna mungo) variety was VBN8. The variety VBN8 is derivative of VBN 3/VBN 04-008 with duration of 65-75 days and an average yield potential of 900 kg ha^-1 under irrigated condition.

The pots with a size of 30 cm diameter and 30 cm height were used for the experiment. The number of pots taken up for the study was 24 numbers. The pots were filled with 1:2 ratio of vermicompost and soil at the time of sowing. In each pot, five seeds were sown. However, after the germination of seeds, two germinated seeds were maintained in each plot by thinning. Observations in each pot, were recorded from both of the germinated seeds.

Plant height
 
There was a significant influence of the treatments on the height of black gram. Plants with maximum height (39.0 cm) were recorded statistically significant in RDF + Urea 1% FS (T₅) at 40 DAS whereas the shortest plant height (26.5 cm) was recorded in RDF - 50% N as Urea Basal Dose + Nano-Urea (Liquid) 50% (FS) + P and K RDF treatment (T₇) as compared to other treatments during 2022. The similar trend was observed during 2023 too.

However, at 60 DAS, the tallest plants were observed in RDF + Urea 1% FS (T₅) (42.1 cm) and shortest plants (31.6 cm) were observed in Control (No NPK) (T₈) (Table 1) Similar results were observed during 2023 also. The tallest plant was significantly recorded under the treatment of RDF + Urea 1% FS compared to others. Increase of growth attributes of black gram under the treatment of RDF + Urea 1% FS (T₅) could be attributed to improved nutrient availability throughout the crop growth phases, with chemical fertilizer supplying NPK at the crop’s initial growth stages and later stages of nutrients. These results also corroborate the findings (Gaurav and Chaturvedi, 2023).


 
Number of branches plant^-1
 
All the treatments showed marked variation on number of branches during 2022 and 2023. At 40 and 60 DAS, maximum number of branches were recorded (26.7 and 37.7 numbers plant^-1) in treatment RDF + Urea 1% FS (T5) that was at par with Nano-Urea (Liquid) 1.25 litres ha^-1 as Foliar Spray (FS) (IFFCO) + P and K RDF (T₂) and RDF - 50 % N as Urea Basal Dose + Urea 1 % (FS) + P and K RDF (T₆). The least number of branches per plant (13.7 and 21.7 numbers plant^-1) were noted in Control (No NPK) (T8) (Fig 1). As a matter of thumb, as the number of leaves plant^-1 increases, so does the leaf area, may haves received observed increased photosynthesis from the source and sink, which results in the growth of additional branches. Application of Nitrogen as a basal dose results in more number of branches (Marimuthu et al., 2024). A combina-tion of soil application and foliar spray, matching the N requirement of crop in demand with time series and subsequent nano N spray probably sustained the N content, so helping to promote cell  division, elongation and in turn the number of branches (Arun Kumar et al., 2024). Alqader et al., (2020) also reported that the application of nano nutrients, particularly nitrogen, has a good influence on the branching development of pea and other pulse crops.



Number of pods plant^-1
 
Significant variation was noticed among the treatments during both the years of experimentation. Recommended Dose of Fertilizer + Urea 1% foliar spray (T₅) registered more number pods per plant (19.0) over others which was at par with T₂ (Nano-Urea (Liquid) 1.25 litres ha^-1 as foliar spray (FS) (IFFCO) + P and K RDF). Persistently, lesser number of pods per plant (9.1) in 2022 was produced by Control (No NPK) (T₈) (Table 2). Similar findings were recorded during 2023. The improved yield characteristics and overall productivity observed with this treatment can be attributed to increased growth parameters caused by a greater availability of vital plant nutrients (Marimuthu et al., 2024). Nitrogen promotes vegetative growth, phosphorus stimulates root development and flowering, while potas-sium aids in a variety of physiological functions. When these vital nutrients are delivered in appropriate quantities, they promote development and increase production charac-teristics. Adequate availability of these nutrients is believed to contribute to enhanced carbohydrate buildup and efficient translocation from source to sink, particularly in reproductive organs. This method results in a significant rise in many yield-attributing characters. These results pertain in close agreement with numerous researchers like Sahu  et al.  (2021); Pareek et al., (2022) and Aniket et al., (2024). It is possible that sufficient nitrogen through nano urea at the crucial period, which would have maintained a constant supply of nitrogen, led to meristematic activity and promotion of cell elongation in plants, resulting in a greater number of pods per plant. These result findings were in close agreement with the findings of Rajesh et al., (2023).


 
Number of grains per pod
 
Statistically maximum number of grains per pod (6.2 and 6.8) were recorded in Nano-Urea (Liquid) 1.25 litres ha^-1 as Foliar Spray (FS) (IFFCO) + P and K RDF (T₂) during 2022 and 2023 (Table 2). The least number of grains per pod (3.4 and 3.5) was observed with Control (No NPK) during 2022 and 2023, respectively. The same outcomes were observed in 2023 as well. The total number of grains per pod may be due to the foliar spray of nano urea, which leads to increased photosynthate assimilation and translocation of photosynthates from the source to the sink Algym et al., (2020); Hafize  and Bati (2023) and Aniket et al., (2024). Islam et al., (2023) reported that, timely supply of nitrogen stimulates the initiation of grain formation, which contributes to the increase in grain count per pod.
 
Pod weight and seed weight
 
Discernible variations have been observed due to various treatment combinations during two years of field experiments. Among the different treatment combination, application of nano-urea (Liquid) 1.25 litres ha^-1 as Foliar Spray (FS) (IFFCO) + P and K RDF (T₂) resulted in higher pod weight and seed weight (4.5 and 3.2 g per plant) during 2022, respectively (Table 3). It was closely on par with RDF + Urea 1% FS (T₅) as compared to others. Lowest pod and seed weight (2.6 and 1.4 g per plant) were recorded in control pot (T₈) during the year of 2022, respectively.



During 2023, marked difference of pod weight and seed weight was manifested due to various treatments. Higher pod and seed weight (6.2 and 3.6 g per plant) was noted under nano-urea (Liquid) 1.25 litre ha^-1 as Foliar Spray (FS) (IFFCO) + P and K RDF (T₂) than other treatments. It was on par with T₅ (RDF + Urea 1% FS). The lowest values for pod and grain weight (4.5 and 1.6 g per plant) was registered under T₈ [Control (No NPK] during 2023, respectively.

It was found to be enhanced by foliar applying fertilizer containing nano-urea. greater starch translocation from the active site of leaves and straw to grain (sink), as well as increased nitrogen provided by nano-urea and a basal dose of potassium throughout the growth phases, could be the cause of this. Consequently, more photosynthetically active radiations are intercepted, increasing photosy-nthesis. The results were in conformity with the findings Islam et al., (2023).

The pod and seed weight per plant considerably increased under Recommended Dose of Fertilizer + Urea 1% FS, showing the function of balanced fertilization in increasing agricultural output. It could be attributed to phosphorus enhanced nodulation and efficient working of nodule bacteria for fixation of nitrogen to be used by plants during grain development stage in protein synthesis as shown in N uptake, which led to a rise in pod and seed weight (Satyanandam et al., 2022). Furthermore, potassium may increase the feeding environment of the rhizosphere and the plant system, resulting in increased nutrient transfer in multiple plant sections, which may directly contribute to pod and seed weight. These findings agree with Kunwar and Victor, 2023.
 
Nutrient (NPK)
 
Recommended dose of fertilizer + Urea 1% foliar spray (T₅) recorded significantly more nitrogen, phosphorus and potassium uptake (0.33, 0.059 and 0.18 g per plant) at harvesting of crop, respectively followed by  nano-urea (Liquid) 1.25 litres ha^-1 as Foliar Spray (FS) (IFFCO) + PandK RDF (T2) (25 x 20 cm) (Fig 2). Control (T₈) resulted in the least nitrogen, phosphorus and potassium uptake (0.10, 0.011 and 0.05 g per plant) at harvesting of the crop, respectively. Similar analyzed results were obtained during 2023 too. This may have attributed to the fact that a balanced utilization of multiple plant nutrient sources results in proper absorption, transport and digestion of those nutrients, ultimately enhancing plant drymatter accumulation and nutrient contents and therefore exhibiting greater uptake of elemental nutrients. Similar findings were reported by Shekhawat et al., 2021.

The study confirmed that the foliar application of nano urea had significant effect on growth and yield parameters of blackgram. Accordingly, it can be concluded that, application of nano-urea (Liquid) 1.25 lit/ha as Foliar Spray (FS) (IFFCO) + PandK RDF responded equally, with the Recommended Dose of Fertilizer + Urea 1% foliar spray on growth and yield attributes of blackgram.

The authors extend their appreciation to the Vanavarayar Institute of Agriculture, Pollachi for funding of this work.
 
Author contributions
 
The process of conceptualization collection of data K.K., C.T. and P.N. and methodology confirmation, M.R.N. and R.M.K., K.K., C.T. and P.N. formal analysis, M.R.N.; investigation, M.R.N. and R.M.K; resources, M.R.N; preparing an original draft, R.M.K and P.N.; Visualization and oversight., C.T and K.K; editing and corrections. All authors read and agreed to the published version of the manuscript.

The authors declare no conflict of interest.