Sensor based nitrogen management in direct seeded basmati rice (Oryza sativa L.)

Introduction

Rice (Oryza sativa L.) is the most important and extensively cultivated food crop that has been referred as "Global grain" because of its use as prime staple food in about 100 countries of the world. Its cultivation is of immense importance to food security of Asia, where more than 90 % of the global rice is produced and consumed. Cereals are the most important part of our diet throughout the world and thus, play major role in our food security. Among cereals, rice has been staple food for more than 60 per cent of the world population, providing energy for about 40% of the world population where every third person on earth consumes rice every day in one form or other (Datta et al., 2002) [1] . Basmati known as the "queen of India" is prized by the consumers across the world for its long grain, soft texture, extreme kernel elongation and pleasant aroma. Basmati rice is the most fragrant rice in the world with no comparison in terms of its distinctive aroma, which is caused by a chemical component known as 2acetyl-1-pyrroline (Buttery et al., 1983) [2] Besides, there is a great diversity in non-Basmati fragrant rice cultivars in the country, which vary greatly in size, shape, colour, texture and flavour. In India basmati rice is cultivated on an area about 21.35 lakh hectares with productivity around 9.85 million tonnes at productivity level of 4.61 tonnes ha -1 (APEDA, 2023) [3] . Direct seeded rice (DSR) has emerged as a viable alternative to traditional transplanting methods, offering several advantages such as reduced labor, water use and greenhouse gas emissions (Jat et al., 2022, Chaudhary et al., 2023 and Singh et al., 2024) [4] . DSR requires 30-50% less water than conventional transplanting, to make it a viable option in water-scarce regions (Sandhu et al., 2021 and Chaudhary et al., 2023) [5] . Labor shortage, during peak transplanting season, has always a challenge (Kumar et al., 2022). ). DSR eliminates need for nursery preparation, transplanting and related activities, thereby reducing Labor requirement. However, efficiency of DSR depends largely on better agronomic practices, such as choosing appropriate fertilization combinations and application timings (Ramesh et al., 2017, Jat et al., 2022 and Zhang and Hu, 2022) [6] Fertilizer management has Shown a significant impact on growth, development and yield of rice (Noulas et al., 2023 and Srivastav et al., 2024) [7] .

Urea is the most common N in rice production worldwide (Fageria, 2009) [8] . Tisdale et al. (1993) [9] also reposrted that the most cost-effective granular form of N is urea [CO(NH2)2] which is widely used as a N source because it has a high N concentration (45%) and lower relative manufacturing, handling, storage, and transportation cost. Nano urea is a novel agri-input based on nanotechnology that gives plants nitrogen. It has a desirable particle size of roughly 20-50 nm, larger surface area (10,000 times over 1 mm urea prill), and more particles (55,000 nitrogen particles over 1 mm urea prill) than ordinary urea prill. Leaf color chart (LCC) is an affordable, user-friendly tool that helps farmers decide when and how much nitrogen fertilizer to apply. It increases rice output and N use efficiency. Farmers without literacy skills can easily use LCC to decide when to apply fertilizer N. Using the spectral properties of rice leaves was the best way to help farmers make an immediate decision on the need for top dressings of in-season fertilizer nitrogen (Singh et al., 2017) [10] .

Materials and methods

This chapter provides a description of the materials and methodology used in the study "Sensor based nitrogen management in direct seeded basmati rice (Oryza sativa L.)" The experimental site is located at a latitude of 29° 40' North and a longitude of 77° 42' East, at an altitude of 237 metres above mean sea level with a subtropical climate, Meerut lies in the central part of western Uttar Pradesh. The experimental field land was uniform in topography and possessed an efficient drainage system. The experimental field's soil had a sandy loam texture, low levels of accessible nitrogen and organic carbon, medium levels of available phosphorus and potassium, and a reaction that was almost neutral. Pusa Basmati-1979 was sown on 20 June 2025 using a row spacing of 20 cm. The experiment was laid out in a Randomized Block Design (RBD) with 8 treatments with 3 replications. The gross plot size was 5.0 m × 3.4 m. The crop receives a total annual rainfall of 850 mm.

Results and Discussion

Yield attributing characters

Table 1. provide the information on rice yield attributes as affected by efficient nitrogen management. Improved yield contributing characteristics (number of effective tillers m -2 , Filled grains panicle -1 , Unfilled grains panicle -1 and test weight) were observed.

Effective tillers m-2

It was evident from the data in Table 1 that applying nitrogen greatly enhanced the number of effective tillers m -2 in the rice crop. The application of nitrogen, namely 33.3% Basal N + nano urea spray at MT and PI stages (T 7 ) resulted in the largest number of effective tillers m -2 (220), while T 1 (50% Basal N + 25% at MT + 25% at PI through urea) had the lowest effective tillers (185). Additionally, T 6 was considerably better than the other treatments and on par with the delivery of nitrogen @ 33.3% Basal N + Rest through Green Seeker.

Filled grains panicle-1

A review of the data revealed that different nitrogen treatments had a considerable impact on the panicle -1 of filled grains (Table 1). At the MT and PI stages, the administration of nitrogen (33.3% Basal N + Spray of nano urea plus at MT and PI stage) resulted in the significantly greatest number of filled grains (88) T 7 . This was statistically comparable to T 6 (33.3% Basal N + Rest through Green Seeker), however T 1 (50% Basal N + 25% at MT + 25% at PI through urea) had the fewest filled grain panicle -1 (70).

Unfilled grains panicle-1

The data showed that different nitrogen treatments had a considerable impact on the panicle -1 of unfilled grains (Table 1). T 1 (50% Basal N + 25% at MT + 25% at PI through urea) and T 7 (33.3% Basal N + Spray of nano urea plus at MT and PI stage) had the greatest (45) and lowest (32) unfilled grains panicle -1 , respectively.

Test weight

The use of nitrogen, specifically 33.3% Basal N + nano urea spray during MT and PI stages (T 7 ), resulted in the noticeably highest 1000grain weight (22.8 g). T 6 , T 3 , T 4 , and T 8 were the next top treatments in terms of test weight. On the other hand, T 1 recorded the minimal 1000-grain weight (20.1 g), followed by T 2 . Sajjad et al. (2024) [11] reported a similar improvement in test weight with equal split nitrogen application and Singh et al. (2024) found that split application of neem-coated urea enhanced yield attributes.

Yield

Table 2. provide information on rice yield as affected by efficient nitrogen management. Improved grain yield, straw yield, biological yield and harvest index were observed.

The application of 33.3% Basal N + nano urea spray @ 4 ml l -1 at MT and PI stages (T 7 ) produced the highest grain yield (4500 kg ha -1

), followed by 33.3% Basal N + Rest through Green Seeker (T 6 ) and significantly higher than other treatments. Farmer's practice (T 1 ) had the lowest grain yield (3840 kg -1 ). Although T 6 had 12.5% and 11.0% higher grain yield as compared to T 1 and T 2 respectively. Danish et al. (2025) [12] reported that 75% prilled urea combined with one nano urea spray recorded the highest grain yield in Basmati rice.

Table 2. provide information on straw yield as affected by various nitrogenous treatments. The highest straw production (6502 kg ha -1 ) was seen when nitrogen @ 33.3% as Basal + nano urea was sprayed at MT and PI stages (T 7 ). Although the per cent increment under T 3 (50% Basal N + Rest through Green Seeker) was to the tune of 1.8% over T 1 (50% Basal N + 25% at MT + 25% at PI through urea), which registered the lowest straw yield (6120 kg ha -1 ).

The maximum biological yield (11002 kg ha -1 ) was recorded with 33.3% Basal N + nano urea spray applied at MT and PI stages) T 7 followed by T 6 (33.3% Basal N + Rest through Green Seeker). However, T 6 had 7.8 % and 6.2 % higher biological yield in comparison to T 1 (50% Basal N + 25% at MT + 25% at PI through urea) and T 2 (33.3% Basal N + 33.3% at MT + 33.3% at PI through urea). The lowest biological yield (9960 kg ha -1 ) was recorded in T 1 followed by T 2 .

Significant variation was brought about by different nitrogen management treatments in the harvest index, which is the ratio of economic output to total biological yield. The treatment that received 33.3% Basal N + nano urea spray at the MT and PI phases had the highest numerical harvest index value (40.9), which was statistically comparable to T 6 , T 3 , and T 4 . Two equal split application of N over 50 % N as basal had the lowest harvest index (38.6). Treatment T 2 and T 5 were next in the order in this regard.

Nitrogen content and its uptake

The chemical analysis data concerning N content and its uptake by grain, straw and the total crop are presented in Table 3.

The application of 33.3% Basal N + Spray of Nano urea plus @ 4 ml l -1 at MT and PI stage (T 7 ) resulted in significantly higher nitrogen content in grain and straw (1.42% and 0.77%, respectively). This was statistically comparable to T 6 (33.3% Basal N + Rest through Green Seeker) and T 3 (33.3% Basal N + 33.3% at MT + 33.3% at PI through urea) than the other treatments. However, T 1 (50% Basal N + 25% at MT + 25% at PI through urea) had the lowest nitrogen concentration in grain (1.29%) and straw (0.61%). Chang et al. (2022) reported that controlled-release urea significantly increased the nitrogen recovery and decreased nitrogen losses, while, Li et al. (2018) [13] found that polymer-coated CRU enhanced nitrogen uptake and NUE. Patel et al. (2019) [14] also reported that split application of neem-coated urea boosted nitrogen use efficiency and nutrient uptake.

In comparison to the other treatments, the application of 33.3% Basal N + Spray of Nano urea plus @ 4 ml l -1 at MT and PI stage (T 7 ) had significantly higher nitrogen uptake in grains, straw and total uptake (35.4, 34.6, and 70.07 kg ha -1 , respectively). This might be probably due to more accumulation of nitrogen and higher yield under T 7 . This was statistically comparable to the application of nitrogen @ 33.3% Basal N + Rest through Green Seeker (T 6 ). However, treatment T 1 had the lowest uptake in grains (24.03 kg ha -1 ), straw (23.42 kg ha -1 ) and total (47.45 kg ha -1 ) followed by T 2 .

Conclusion

Based on the experimental results, it can be concluded that applying 33.3% basal N along with nano urea spray @ 4 ml l -1 at MT and PI stages enhances the yield attributes, yield and total nutrient uptake in rice. The next best option is sensor based i.e., 33.3% basal N along with Green Seeker based N application.

Acknowledgement

AcknowledgementThe authors express sincere gratitude to Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut, India (250110), for providing necessary facilities to carry out this study. The authors are also thankful to their chairperson Dr. Adesh Singh, Professor, Department of Agronomy and advisory committee for their guidance and support throughout the research work. Sincere thanks are extended to the technical staff of the Crop Research Centre for their assistance during field experimentation.

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