Rice (Oryza sativa L.) is the principal staple food for more than one-third of the global population and plays a critical role in ensuring food and nutritional security, particularly in Southeast Asia (Karki et al., 2023). Over two billion Asians derive 60-70% of their energy from rice (Kumar et al., 2024). In India, rice is grown during summer, autumn and kharif seasons. With global cultivation spanning 163 million hectares across more than 100 countries, rice has rightly earned the title of the “global grain”. In India, rainfed rice accounts for 86.88% of total rice production (Ahmed and Saikia, 2020). The country needs an additional 50 million tonnes of rice by 2030 to meet the food demands of an estimated 1.5 billion population (Singh and Solanki, 2026). Phosphorus (P) is the second most essential macronutrient after nitrogen. It is often deficient in agricultural soils due to its low mobility and high fixation rate (Kumar et al., 2019; Purohit et al., 2020). Phosphorus is vital for root development, energy transfer, nucleic acid synthesis and photosynthate translocation (Tsukru and Pandey, 2023; Kayanmunu et al., 2023). Its role in enhancing tiller emergence, panicle development and grain filling is crucial for rice productivity (Erman and Ceritoglu, 2025; Khan et al., 2023). In Odisha, the eighth-largest rice-producing state in India, rice output in 2024 was 5.87 million tonnes. In Gajapati district, rice is cultivated on 32,350 hectares with a total production of 127,100 tonnes at a productivity level of 748 kg ha^-1 (GOI, 2023). Optimizing phosphorus application is essential, especially in such rainfed ecosystems where nutrient losses are high and fertilizer use efficiency is low. Phosphorus improves leaf area index (LAI), plant height and biomass accumulation, contributing to higher yields (Chaudhari and Zinzala, 2024; Yang et al., 2025). Field experiments show that phosphorus applied at transplanting enhances uptake and crop performance (El-Shabasy et al., 2025). Effective phosphorus management strategies should focus on determining the critical dose for maximum yield and phosphorus use efficiency (Ramesh et al., 2023; Mrudhula et al., 2019). Furthermore, in flooded or lowland soils typical of kharif rice cultivation, phosphorus dynamics differ significantly, demanding localized and efficient management approaches (Panda et al., 2023). Hence, optimizing phosphorus use is vital for improving yield, resource use efficiency and ensuring sustainable rice production in South Odisha (Ravali et al., 2022; Barlog et al., 2022).

Experiment location and description of materials
 
During the kharif season of November 2024, a study was conducted at P.G. Research Farm, M.S. Swaminathan School of Agriculture, Centurion University of Technology and Management, Paralakhemundi, Odisha. The geographical location of the experimental site is (18°81'N latitude, 84°18'E longitude, with an altitude of 61 meters above the mean sea level). The meteorological data was collected from an automatic weather station situated at Centurion University of Technology answered Management, Parlakhemundi campus. The research field had soil with a sandy loam texture and a slightly acidic pH level. The soil had low levels of organic carbon and available nitrogen but contained moderate amounts of phosphorus and potassium. The maximum temperature varied from 30.10 to 34.13°C and the minimum temperature ranged from 16.21 to 85°C during cropping. The crop experienced the highest atmospheric temperature (85°C) in the 31^st SMW and the lowest (16.21°C) in the 47^th SMW during the cropping season.
 
Experiment design and treatments
 
The field experiment was conducted using a randomized block design (RBD) with three replications and nine phosphorus levels (0 to 80 kg P₂O₅ ha^-1 at 10 kg intervals). The test crop was rice variety RNR 15048 (Telangana Sona), with a duration of 120 days. Each plot measured 4.5 m × 4 m, with a spacing of 20 cm × 15 cm. The soil type was sandy loam under a sub-humid climate. A uniform recommended dose of 80:40:40 kg ha^-1 N: P₂O₅: K₂O was applied and 27 plots were maintained in total for the study.
 
Measurement of growth and yield parameters
 
Plant height was measured from the base to the tip of the tallest panicle-bearing plant in each plot at harvest. For dry matter accumulation, five representative plants were uprooted, oven-dried at 65°C until constant weight. Yield attributes of rice were estimated through field-based sampling by recording panicle number per unit area, grains per panicle and 1000-grain weight from randomly selected five plants at maturity. Grain yield was recorded by harvesting the net plot area, threshing, drying and expressing at 14% moisture. Straw yield was obtained by subtracting grain weight from total above-ground biomass.
 
Statistical analysis
 
For reliable interpretation, the biometric data collected were statistically analyzed following the standard procedures outlined by Gomez and Gomez (1984). Analysis of variance (ANOVA) was performed using the “F” test to determine the significance of treatment effects. The standard error of the mean was calculated for each parameter. Significant differences among treatment means were further assessed using the critical difference (CD) at a 5% probability level. Where applicable, duncan’s multiple range test (DMRT) at 5% significance was employed for mean separation. All analyses were conducted using OPSTAT software developed by CCS Haryana Agricultural University, Hisar (http://www.opstat.nic.in). Correlation and PCA analysis were by using R Studio (version 4.2).

Plant height
 
The plant height of rice at harvest was significantly influenced by varying phosphorus levels (Table 1). The treatments P₄₀ (114 cm), P₅₀ (116 cm), P₆₀ (118 cm), P₇₀ (117 cm) and P₈₀ (116 cm) recorded the tallest plants and were statistically at par with each other. However, these treatments were significantly superior to all lower phosphorus levels (P₀ to P₃₀). This indicates that beyond 40 kg P₂O₅ ha^-1, further increases in phosphorus did not significantly influence plant height, although a numerical increase was observed up to 60 kg P₂O₅ ha^-1. The enhancement in plant height with increased phosphorus levels up to 60 kg P₂O₅ ha^-1 can be attributed to the crucial role of phosphorus in promoting cell elongation, root development and energy transfer through ATP. These physiological processes collectively support better vegetative growth and increased plant stature. The results align with the findings of Tsukru et al., (2023); Pal et al., (2018). Beyond 60 kg P₂O₅  ha^-1, the marginal or no significant increase in height may indicate that the phosphorus requirement had already been met and additional application resulted in luxury consumption without further growth advantage.


 
Dry matter accumulation
 
Phosphorus application significantly affected dry matter accumulation (DMA) of rice at harvest (Table 1). A significant increase was observed with P₂₀ (933 g m^-2) over the lowest values which was statistically at par with P₃₀ (947 g m^-2). Further increases in phosphorus level resulted in progressive increases in DMA. The treatment P₆₀ (1047 g m^-2) recorded the highest dry matter accumulation that was significantly higher than all other treatments. However, it was statistically at par with P₄₀ (990 g m^-2), P₅₀ (1022 g m^-2), P₇₀ (1037 g m^-2) and P₈₀ (1032 g m^-2). These results suggest that dry matter accumulation improved consistently with phosphorus up to 60 kg P₂O₅  ha^-1, beyond which the increases were not statistically significant. The significant increase in dry matter accumulation with increasing phosphorus levels up to 60 kg P₂O₅ ha^-1 can be attributed to the role of phosphorus in enhancing energy transfer, photosynthesis and root development. These factors contribute to greater vegetative growth and biomass accumulation. Similar trends have been observed by Hu et al., (2025) and Panda et al., (2023), who reported improved dry matter production in rice with balanced phosphorus fertilization.
 
Yield attributes
 
Phosphorus application significantly influenced most yield attributes of rice at harvest. The number of panicle-bearing tillers increased from 200 m^-2 in the control (P₀) to a maximum of 283 m^-2 at P₆₀, which was statistically at par with P₅₀, P₇₀ and P₈₀. Panicle length was shortest in P₀ (20.07 cm) and significantly increased up to 25.1 cm in P₆₀, with all treatments from P₃₀ onward showing statistically similar values and superior to the control. The number of spikelets per panicle also increased markedly with phosphorus, from 226 (P₀) to 286 (P₆₀), with P₄₀ to P₈₀  being statistically at par and significantly higher than lower levels. A similar trend was observed for effective grains per panicle, with the lowest in P₀ (198) and the highest in P₆₀ (254), statistically comparable with P₅₀  to P₈₀. In contrast, 1000 grain weight was not significantly affected by phosphorus application, although it showed a slight numerical increase from 13.2 g (P₀) to 14.4 g (P₆₀ and P₈₀ ). The improvements in yield attributes with increasing phosphorus levels can be attributed to phosphorus’s vital role in promoting root growth, tiller development and reproductive efficiency. Increased panicle-bearing tillers, panicle length and number of spikelets and grains per panicle suggest enhanced assimilate production and partitioning under adequate phosphorus supply. This reflects better sink development and grain filling potential, as also reported by earlier studies of Han et al., (2022); Hemasravanthi et al. (2022).
 
Yield      
 
The grain yield increased steadily with phosphorus levels from 3.14 t ha^-1 in the control (P₀) to a maximum of 4.50 t ha^-1 at P₆₀, which was significantly higher than all other treatments (Fig 1). Treatments P₅₀ (4.33 t ha^-1), P₇₀ (4.42 t ha^-1) and P₈₀ (4.37 t ha^-1) were statistically at par with P₆₀ and significantly superior to P₀ to P₂₀. Grain yield under P₄₀ (4.15 t ha^-1) and P₃₀ (3.98 t ha^-1) also showed significant improvement over lower phosphorus levels. For straw yield, the lowest value was recorded under P₀ (5.17 t ha^-1) that was significantly lower than all other treatments. The highest straw yield (6.37 t ha^-1) was recorded under P₅₀, statistically at par with P₆₀ (6.33 t ha^-1), P₇₀ (6.33 t ha^-1), P₈₀ (6.27 t ha^-1) and P₄₀ (6.03 t ha^-1). The increase in grain and straw yield with rising phosphorus levels up to 60 kg P₂O₅ ha^-1 can be attributed to enhanced crop growth, nutrient uptake and better reproductive development. Adequate phosphorus supply plays a vital role in energy metabolism, root proliferation and translocation of assimilates, which collectively contribute to improved biomass and grain formation. The findings are consistent with reports by Gupta et al. (2024) and Pal et al. (2018), who also observed maximum rice productivity at phosphorus levels around 50-60 kg ha^-1. The lack of significant yield improvement beyond P₆₀ indicates that this level meets the crop’s phosphorus demand under the prevailing soil and climatic conditions. The concurrent increase in straw yield with grain yield further confirms the overall improvement in biomass production with optimal phosphorus nutrition.


 
Correlation matrix among important agronomic traits affecting crop growth and yield performance
 
The correlation matrix (Fig 2) illustrates the pairwise relationships among key agronomic traits influencing crop growth and yield. In the upper triangle, Pearson correlation coefficients with significance levels (*** for p<0.001) are presented, while the lower triangle shows corresponding scatterplots. Strong positive correlations were observed among traits such as tillers per square meter, leaf area index (LAI), dry matter accumulation (DMA), panicle-bearing tillers and grain yield. Notably, tiller density exhibited near-perfect correlations with LAI (r = 0.99***), DMA (r = 0.99***) and panicle-bearing tillers (r = 0.98***), highlighting the interconnected role of vegetative growth and reproductive development in enhancing yield potential.Grain yield was strongly correlated with primary yield components including 1000 grain weight (r = 0.99***), straw yield (r = 0.98***), spikelets per panicle (r = 0.96***) and effective spikelets (r = 0.95***), underscoring the importance of panicle efficiency and grain size in yield formation. Additionally, panicle length and LAI were also positively associated with yield attributes. In contrast, plant height showed weak to moderate negative correlations (r = -0.23 to -0.42) with most traits, suggesting that taller plants may allocate fewer resources to grain production, potentially limiting productivity under the studied conditions.


 
Principal component analysis (PCA)
 
The first principal component (PC1) accounts for 87.78% of the total variation, while the second component (PC2) explains an additional 10.03%, cumulatively capturing 97.81% of the variability (Fig 3). The traits such as grain yield, straw yield, panicle-bearing tillers, 1000 grain weight, number of tillers per m², dry matter accumulation, effective spikelets per panicle and number of spikelets per panicle are closely clustered and positively aligned with PC1, suggesting a strong positive association among them. These traits are the major contributors to the variation explained by PC1 and are indicative of yield potential. Treatments T₁, T₃ and T₄ are positioned on the positive side of PC1, showing strong association with these yield-contributing traits, particularly T₁ that was farthest along PC1, indicating superior performance. In contrast, plant height was distinctly oriented along PC2, forming a separate axis of variation, suggesting it contributes independently and was not strongly associated with other yield components. T₂, located far along the positive PC2 axis, is strongly associated with plant height but not with yield traits. Conversely, T₆ and T₅ lie closer to the origin, indicating moderate performance across all traits.


 
Correlation between principal components and variables
 
The principal component PC1 had positive correlation (Fig 4) with variables plant height (0.1381), while negative correlation with variables effective spikelets per panicle (-0.3429), panicle bearing tillers (-0.3461), No. of spikelets per panicle (-0.3465), 1000 grain weight (-0.3519), Nooftillersm-2 (-0.3522), straw yield (-0.3527), dry matter accumulation (-0.3541) and grain yield (-0.3547).


       
Application of phosphorus up to 60 kg P₂O₅ ha^-1 significantly improved rice growth, yield attributes and productivity. Beyond this level, no further yield advantage was observed, indicating optimal phosphorus requirement. Strong correlations among growth and yield traits highlight the importance of balanced phosphorus nutrition in rice cultivation on lateritic soils.

From these results it can be concluded that application of 60 kg P₂O₅ ha^-1 can be considered the optimum dose for maximizing rice growth and yield under the prevailing southern Odisha conditions.

There is no conflict for publication.