Influence of fertilizer deep placement and nano urea on Growth, Yield and Economics of transplanted kharif rice

Introduction

Rice (Oryza sativa L.) is one of the most important staple food crops in the world, providing primary dietary energy for more than half of the global population. In India, rice occupies a major share of the cultivated area and plays a crucial role in ensuring food security and rural livelihoods, particularly in rainfed ecosystems where productivity is often constrained by nutrient limitations and erratic rainfall. Efficient nutrient management, especially nitrogen fertilization, is essential for sustaining rice productivity under such conditions. Nitrogen is a key macronutrient required for plant growth and development, as it directly influences chlorophyll formation, photosynthesis, tillering, biomass production, and grain yield in rice (Fageria et al., 2008) [3] . However, conventional nitrogen application methods often result in low nitrogen use efficiency due to losses through volatilization, leaching, denitrification, and runoff, particularly under flooded or rainfed environments. Therefore, improving nitrogen use efficiency through innovative application methods has become a major research priority in rice-based production systems. Fertilizer deep placement (FDP) has emerged as an effective nitrogen management strategy that places fertilizer directly in the root zone, reducing nutrient losses and improving nitrogen recovery efficiency. Several studies have reported that FDP enhances tillering, biomass accumulation, and grain yield in rice compared to conventional broadcast application (Bandaogo et al., 2015; Wang et al., 2022; Zou et al., 2023) [1,12,15] . Similarly, nano-urea has gained attention as a promising nitrogen source due to its controlled-release properties, improved nutrient uptake, and reduced environmental losses, leading to enhanced crop performance and sustainability (Kumar et al., 2021) [11] . In rainfed rice ecosystems, where nutrient availability and water supply are highly variable, optimizing nitrogen dose and application method is critical for maximizing productivity and profitability. Previous research has highlighted the potential of integrating higher nitrogen levels with advanced delivery techniques such as improve crop growth and yield attributes (Mumtahina et al., 2024; Benzon et al., 2015) [8,2] . However, comparative information on the combined effects of nitrogen levels, nano-urea application, and fertilizer deep placement under rainfed transplanted rice conditions is limited, particularly in the Agro-climatic conditions of Assam. Therefore, the present investigation was undertaken to evaluate the effect of different nitrogen doses and application methods, including nano-urea and fertilizer deep placement, on growth, yield, and economic performance of transplanted rice under rainfed conditions. The study aims to identify an efficient and economically viable nitrogen management strategy for sustainable rice production in the region.

Materials and Methods

The present investigation was conducted during the kharif seasons of 2022 and 2023 under rain-fed conditions at the Instructional-cum-Research (ICR) Farm, Assam Agricultural University, Jorhat, which is situated at 26º71' N latitude, 94º18' E longitudes and at an altitude of 86.6 m above mean sea level. The amount of rainfall received during crop period was 1024.3 mm and 852.7 mm in 2022 and 2023, respectively. The maximum and minimum temperature ranges from 28.4 to 34.9 and 11.6 to 25.6 in 2022 respectively. The maximum and minimum temperature ranges from 24.6 to 36.6 and 12.7 to 25.7 in 2023 respectively. The experiment was laid out in a Randomized Block Design (RBD) with a plot size of 4 m × 3 m. The study consisted of three replications. The treatment combinations are T 1 -Control; T 2 -50% RDN; T 3 -75% RDN; T 4 -100% RDN; T 5 -125% RDN; T 6 -50% RDN + Nano-urea; T 7 -75% RDN + Nano-urea; T 8 -100% RDN + Nano-urea; T 9 -125% RDN + Nano-urea; T 10 -50% RDN as FDP; T 11 -75% RDN as FDP; T 12 -100% RDN as FDP and T 13 -125% RDN as FDP. (Note: RDN= Recommended dose of Nitrogen; FDP= Fertilizer deep placement).

Results and discussion

Plant height increased significantly with the application of nitrogen at various growth stages. The treatment with 125% RDN as FDP (T 13 ) achieved significantly higher plant heights of 130.76 cm, 148.31 cm, and 146.26 cm at 60 DAT, 90 DAT, and at harvest, respectively, compared to other treatments. In 30 DAT 125% RDN+ nano-urea (T 9 ) treatment recorded highest plant height (69.39 cm). However, these results were at par to those from 125% RDN+ nano-urea (T 9 ) and 100% RDN as FDP (T 12 ). The significant increase in plant height is because nitrogen is a critical nutrient that plays a vital role in plant growth, influencing processes such as photosynthesis, tillering, and overall biomass accumulation (Bandaogo et al., 2015) [1] . The deep placement of nitrogen fertilizers ensures that the nutrients are available in the root zone, promoting better uptake and utilization by the plants (Zou et al., 2023) [15] .

Effect on No of tillers per m 2

Results shows that the application of nitrogen significantly increased the number of tillers/ m² at various growth stages of transplanted rice (TPR). The treatment with 125% RDN as FDP (T 13 ) produced significantly higher tiller counts per m² was 330.16, 347.92, 315.79, and 310.86 at 60, 90 DAT, and at harvest, respectively compared to all other treatments. However, these results were statistically comparable to those from 125% RDN + nano-urea (T 9 ) and 100% RDN as FDP (T 12 ). Correspondingly lowest number of tillers were recorded in T 1 (Control) treatment. The increase in tiller number observed with the application of 125% RDN as FDP (T 13 ) can be attributed to the efficient delivery of nitrogen to the root zone, promoting better nutrient uptake and utilization by the plants. Optimized nitrogen fertilization strategies, including deep placement and controlled-release fertilizers, improved yield and nitrogen accumulation in rice (Zou et al., 2023) [15] and Sekhar et al. (2014) [10] . The application of nitrogen fertilizers through deep placement methods led to increased nitrogen recovery efficiency and grain yield in various rice cultivars, reinforcing the positive impact of such practices on tiller development (Wang et al., 2022) [12] .

The dry weight of transplanted rice (TPR) increased significantly with the application of nitrogen, particularly when combined with nano urea and Fertilizer Deep Placement methods at different growth stages. The treatment with 125% RDN as FDP (T 13 ) resulted in significantly higher dry weights are 473.94, 1019.65, 1357.88, and 1528.14 g/m² at 30, 60, 90 DAT, and at harvest, respectively compared to all other treatments. However, these results were statistically at par to those from 125% RDN nano-urea (T 9 ) and 100% RDN as FDP (T 12 ). Fertilizer deep placement method ensures that nutrients are readily available to the plants, leading to improved growth and higher biomass accumulation. Gill et al. (2006) [4] and Bandaogo et al., 2015. [1]

Effect on grain yield

The grain yield data (q/ha) for various nitrogen underscores the effectiveness of different fertilization strategies in transplanting methods of establishment, Treatment T 13 (125% RDN as FDP) registered the highest pooled grain yield of 53.04 q/ha. It was followed by treatment T 9 (125% RDN + nano-urea), yielding 50.75 q/ha (Table 4.19 and 4.20). This treatment was statistically comparable to T 13 in the transplanting method. Conversely, the lowest yield was recorded with Treatment T 1 (control), with 21.24 q/ha. FDP significantly increased rice yields compared to traditional methods (Mumtahina et al., 2024) [8] . Additionally, FDP led to more grains per panicle and higher panicle density, contributing to greater overall yield (Mankotia et al., 2009) [7] . Deep fertilizer placement enhances nutrient availability directly to plant roots, improving uptake efficiency in transplanted rice (Nagabhushanam and Bhatt, 2020) [9] . This method reduces nutrient loss in the upper soil layers and concentrates nutrients in the root zone, allowing plants to absorb them more effectively and reducing the need for excessive fertilizer applications (Benzon et al. 2015) [2] . The improved nutrient assimilation by plants has played a pivotal role in fostering optimal growth of plant components and essential metabolic processes like photosynthesis. Consequently, this phenomenon has facilitated the maximum accumulation and translocation of photosynthates towards the economically valuable plant parts. This effect is in accordance with prior studies by Harsini et al. (2014) [5] , and Benzon et al. (2015) [2] .

The highest straw yield was recorded with application of 125% RDN as FDP (T 13 ) with average of 68.41 q/ha. This was closely followed by 125% RDN + nano-urea (T 9 ) yielding 65.71 q/ha, which was statistically at par to T 13 . The lowest straw yield was seen with treatment T 1 (control), averaging 36.73 q/ha. FDP improves the root zone nutritional environment, allowing for better absorption of nitrogen and other essential nutrients, particularly during critical growth stages between 50-75 days after sowing (DAS) (Sheoran et al., 2025) [11] . Deep placement methods, such as using hand or applicator tools, enhanced nitrogen use efficiency and reduced nitrogen losses. This led to better overall plant growth, including increased straw biomass. Increased nitrogen levels lead to the production of growthpromoting hormones and compounds within the plant, enhancing cell division and elongation, which contributes to increased biomass and higher straw yields (Wu et al., 2017) [13] . The deep placement of fertilizers encourages the development of a more extensive root system. As roots grow deeper to access nutrients, they can also explore a larger volume of soil, which improves the plant overall ability to absorb water and other essential nutrients (Zhu et al., 2019); (Li et al., 2020) [14,6] .

Effect on Economics

The lowest cost of cultivation was recorded under T 1 (Control) with a mean value of Rs. 44,305.50/ha, owing to the absence of nitrogen fertilizer application the highest cost of cultivation was observed in T 13 (125% RDN as FDP), which registered a mean cost of Rs. 50,380.58/ha, followed closely by T 12 (100% RDN as FDP) with Rs. 50,173.63/ha. Overall, treatments involving higher nitrogen doses and fertilizer deep placement (FDP).

The highest gross returns were achieved with treatment T 13 (125% RDN as FDP), resulting in an average return of ₹146,253.82/ha. Following this, the second highest returns were recorded with Treatment T 9 (125% RDN + nano-urea) at ₹134,683.56 / ha. In stark contrast, the lowest gross returns were observed in the control group treatment T 1 leading to an average return of ₹63,149.74 / ha. The highest net returns were recorded for Treatment T 13 (125% RDN as FDP). This treatment yielded an outstanding mean net return of ₹ 95,873.24 /ha over the two years using FDP with 125% RDN significantly enhanced profitability, this was followed by treatment T 9 (125% RDN + nano-urea), with a mean net return of ₹90,624.47 /ha. The lowest net returns were noted for the control treatment T 1 (control), with a mean net return of ₹18,844.24 /ha. Among the treatments evaluated, the one with the highest mean benefit-cost ratio of 1.90 corresponds to the application of treatment 125% RDN as FDP (T 12 ). The second highest mean ratio of 1.83 is associated with the treatment of 125% RDN + nano-urea. The lowest mean benefit-cost ratio of 0.43 is linked to the control treatment (T 1 ) with no additional nitrogen application.

Conclusion

The study revealed that nitrogen management significantly influenced the growth, yield, and economics of transplanted rice under rainfed conditions. Among all treatments, 125% RDN applied through fertilizer deep placement (FDP) consistently produced the highest plant height, tiller number, dry matter accumulation, grain yield (53.04 q/ha), and straw yield (68.41 q/ha). Although FDP treatments involved higher cultivation costs, 125% RDN as FDP resulted in the maximum gross and net returns and the highest benefit-cost ratio (1.90), indicating superior profitability. Treatments with 125% RDN + nano-urea and 100% RDN as FDP were statistically comparable with the best treatment for several parameters. Overall, the findings suggest that fertilizer deep placement of nitrogen at 125% RDN is an effective and economically viable nitrogen management strategy for enhancing productivity and profitability of transplanted rice under rainfed conditions.

References

1. Bandaogo A, Bidjokazo F, Youl S, Safo E, Abaidoo R, Andrews O. Effect of fertilizer deep placement with urea supergranule on nitrogen use efficiency of irrigated rice in Sourou Valley (Burkina Faso). Nutrient Cycling in Agroecosystems. 2015;102(1):79-89.
2. Benzon HRL, Rubenecia MRU, Ultra VU Jr, Lee SC. Nano-fertilizer affects the growth, development, and chemical properties of rice. International Journal of Agronomy and Agricultural Research. 2015;7(1):105-117.
3. Fageria NK, Baligar VC, Li YC. The role of nutrientefficient plants in improving crop yields in the twenty-first century. Journal of Plant Nutrition. 2008;31(6):1121-1157.
4. Gill MS, Kumar P, Kumar A. Growth and yield of directseeded rice (Oryza sativa) as influenced by seeding technique and seed rate under irrigated conditions. Indian Journal of Agronomy. 2006;51(4):283-287.
5. Harsini MG, Habibi H, Talaei GH. Study on the effects of iron nano-chelated fertilizers foliar application on yield and yield components of a new wheat line in cold regions of Kermanshah province. International Journal of Farming and Allied Sciences. 2014;3(7):781-786.
6. Li L, Zhang Z, Tian H, Mo Z, Ashraf U, Duan M, Pan S. Roles of nitrogen deep placement on grain yield, nitrogen use efficiency, and antioxidant enzyme activities in mechanical pot-seedling transplanting rice. Agronomy. 2020;10(9):1252-1267.
7. Mankotia BS, Shekhar J, Negi SC. Effect of crop establishment techniques on productivity of rice-wheat cropping system. ORYZA -An International Journal on Rice. 2009;46(3):205-208.
8. Mumtahina N, Yoshinaga K, Moriwaki A, Uemura M, Matsuoka A, Shimono H, Matsunami M. Effects of deep placement of fertilizer on growth, productivity, and fertilizer use efficiency of rice in cool climatic regions. Journal of Soil Science and Plant Nutrition. 2024;24(2):2985-2996.
9. Nagabhushanam U, Bhatt PS. Effect of sowing dates and different crop establishment methods on yield and economics of rice (Oryza sativa L.). Journal of Pharmacognosy and Phytochemistry. 2020;9(2):1075-1079.
10. Sekhar D, Rao KT, Rao NV. Effect of integrated nitrogen management on yield and quality of rice. International Journal of Farm Sciences. 2014;4(4):1-7.
11. Sheoran HS, Kumar V. Fertility management in saltaffected soils under rice-wheat cropping system: A review. Agricultural Reviews. 2025;46(2):1-12.
12. Wang W, Shen C, Xu Q, Zafar S, Du B, Xing D. Grain yield, nitrogen use efficiency, and antioxidant enzymes of rice under different fertilizer nitrogen inputs and planting density. Agronomy. 2022;12(2):430-445.
13. Wu G, Yu G, Xiang X, Wang L. Design and test of rice potted-seedling transplanting mechanism with three transplanting arms. Transactions of the Chinese Society of Agricultural Engineering. 2017;33(15):15-22.
14. Zhu C, Xiang J, Zhang Y, Zhang Y, Zhu D, Chen H. Mechanized transplanting with side deep fertilization increases yield and nitrogen use efficiency of rice in Eastern China. Scientific Reports. 2019;9(1):5653-5665.
15. Zou Y, Zhang Y, Cui J, Gao J, Guo L, Zhang Q. Nitrogen fertilization application strategies improve yield of rice cultivars with different yield types by regulating phytohormones. Scientific Reports. 2023;13(1):2180321815.