Economic feasibility of irrigation scheduling and nutrient management practices in direct seeded rice under Vindhya Plateau conditions

Introduction

Rice (Oryza sativa L.) is a principal staple for more than half of the global population and underpins food and livelihood security across Asia. In India, it occupies a central position in the agricultural economy; however, the conventional puddled transplanted system is increasingly constrained by high water demand, rising labour costs and declining resource-use efficiency (Kumar & Ladha, 2011; Carrijo et al., 2017) [2,7] . In this context, direct seeded rice (DSR) has emerged as a viable alternative, offering advantages such as reduced labour requirement, lower water use and timely crop establishment, particularly under water-scarce environments (Sandhu et al., 2021; Jat et al., 2019) [5,11] . Water availability is the most critical factor governing rice productivity. Traditional flooding methods are inefficient, leading to substantial conveyance and percolation losses. Improved irrigation strategies, such as controlled saturation and alternate wetting and drying (AWD), have been shown to enhance water productivity while maintaining or even improving yields by aligning water supply with crop demand (Bouman et al., 2007; Lampayan et al., 2015) [1,9] . However, the performance of these irrigation regimes is highly dependent on soil type, climatic conditions and crop management practices, especially in semi-arid regions such as the Vindhya Plateau of Madhya Pradesh. Parallel to water management, nutrient management plays a decisive role in determining crop productivity and profitability. Nitrogen, phosphorus and potassium are key drivers of plant growth, Modulating physiological activities such as photosynthetic efficiency, tiller formation, and grain filling. Imbalanced or inadequate fertilization not only reduces yield but also lowers nutrient use efficiency and economic returns (Dobermann & Fairhurst, 2000; Ladha et al., 2005) [4,8] . Recent studies have emphasized that optimizing fertilizer inputs beyond conventional recommendations can improve both yield and profitability when supported by appropriate moisture conditions (Liu et al., 2021; Zhang et al., 2020) [10,16] . Importantly, irrigation and nutrient management do not act independently; rather, they exhibit strong interactive effects on crop growth and yield formation. Adequate soil moisture enhances nutrient solubility and uptake, while proper nutrient supply improves plant tolerance to water stress and increases water-use efficiency (Cassman et al., 1998; Kumar et al., 2018) [3,6] . This interaction becomes particularly critical in DSR systems, where soil moisture dynamics differ significantly from transplanted rice systems. Despite growing evidence on individual effects of irrigation and nutrient management, there is limited information on their combined economic feasibility under region-specific conditions, especially in the Vindhya Plateau. Therefore, the present investigation was undertaken to evaluate the economic viability of different irrigation scheduling and nutrient management practices in direct seeded rice, with the objective of identifying an optimal combination that maximizes productivity, profitability and resource-use efficiency under semi-arid agro-ecological conditions.

Materials and Methods

Experimental site

The field investigation was conducted during the Kharif seasons of 2021 and 2022 at the Agriculture Research Farm of Rabindranath Tagore University, located in the Vindhya Plateau region of Madhya Pradesh. This region represents a typical semi-arid to sub-humid agro-ecology where rainfall variability and intermittent dry spells often influence crop performance. The climate during the cropping period was characterized by warm temperatures, moderate to high humidity and monsoon-driven precipitation, creating a dynamic soil moisture environment for direct seeded rice. The experimental field possessed soils representative of the region, moderately fertile with good tilth and drainage capacity, making them suitable for evaluating water and nutrient management strategies under direct seeding conditions. Prior to sowing, the field was uniformly prepared to ensure a fine seedbed, facilitating proper germination and establishment. Such conditions were essential to minimize variability arising from soil heterogeneity and to ensure that treatment effects were clearly expressed.

Experimental design and treatment details

The experiment was conducted in a Split Plot Design with three replications, a choice justified by the practical difficulty of imposing irrigation treatments at smaller plot scales. Irrigation scheduling was therefore assigned to the main plots, while nutrient management treatments were randomized within sub plots to capture their differential effects with greater precision. The main plot treatments consisted of three irrigation regimes: The recommended dose of fertilizers (RDF) was applied according to treatment specifications, ensuring precise nutrient delivery. The rice variety PB-1 was selected for its adaptability to direct seeded conditions. Sowing was carried out using direct seeding under recommended spacing, and all agronomic practices were followed uniformly to maintain experimental consistency.

Crop management

The crop was established under well-prepared field conditions to ensure uniform emergence. Nutrient application was carefully managed, with nitrogen applied in split doses to synchronize nutrient availability with crop demand, thereby improving nutrient use efficiency and minimizing losses.

Irrigation was applied strictly according to the defined treatment schedules, with careful monitoring of soil moisture conditions to maintain treatment integrity. Particular attention was given to critical growth stages such as tillering and flowering, where moisture availability plays a decisive role in yield formation.

Weed management was carried out using appropriate pre-and post-emergence practices, while plant protection measures were implemented as needed to prevent pest and disease incidence. These uniform management practices ensured that observed differences in crop performance were attributable primarily to irrigation and nutrient treatments rather than external factors.

Observations Recorded Yield and yield attributes

At physiological maturity, crop samples were harvested from the net plot area to record grain yield, straw yield and biological yield, expressed in quintals per hectare (q ha⁻¹).

Care was taken to avoid border effects and ensure representative sampling. Harvest index was calculated as the ratio of grain yield to total biological yield and expressed as a percentage, providing insight into the efficiency of assimilate partitioning from vegetative to reproductive components.

Economic analysis

An economic assessment was carried out to evaluate the practical feasibility of each treatment combination. Cost of cultivation was computed based on prevailing input costs, including seed, fertilizers, irrigation and labour. Gross returns were calculated using market prices of grain and straw, reflecting real-world economic conditions. Net returns were derived by subtracting total cost of cultivation from gross returns, while the benefit-cost (B:C) ratio was used as an indicator of economic efficiency and profitability.

Statistical analysis

The experimental data were subjected to statistical analysis using analysis of variance (ANOVA) appropriate for Split Plot Design. Treatment effects were tested at the 5% level of significance, and critical difference (CD) values were calculated for comparison of means. Interaction effects between irrigation scheduling and nutrient management were also examined to understand their combined influence on yield and economic parameters. This analytical approach ensured a robust interpretation of treatment effects and their practical implications.

Results and Discussion

The data presented in [6,11] .

Effect of Irrigation Scheduling

Among irrigation treatments, IR2 Maintenance of saturation upto tillering (50-55 DAS), flooding from tillering to flowering (55-100 DAS) later saturation till harvest recorded the highest grain yield (52.9 and 54.3 q ha-1), followed by IR1, whereas IR3 recorded the lowest yield. The superior performance of IR2 can be explained through optimized soilplant-water relationships, wherein continuous soil moisture availability during vegetative growth enhances root proliferation, nutrient diffusion and nitrogen uptake, while subsequent flooding during reproductive stages ensures reduced spikelet sterility and improved grain filling. Adequate water availability during critical stages maintains higher leaf water potential and stomatal conductance, thereby sustaining photosynthetic activity and assimilate production. This ultimately improves the source-sink relationship, resulting in higher yield. In contrast, IR3 (alternate wetting and drying) induced intermittent moisture stress, which likely reduced root hydraulic conductivity, restricted nutrient uptake and caused partial stomatal closure, thereby limiting carbon assimilation and reducing grain filling efficiency. [1] , who demonstrated that controlled irrigation regimes improve water productivity by aligning water supply with crop demand. More recent studies by Lampayan et al. (2015) [9] and Carrijo et al. (2017) [2] also confirmed that optimized irrigation enhances yield stability and water-use efficiency in direct seeded rice systems.

Effect of Nutrient Management

Nutrient management exerted a significant influence on yield and its components. Among the treatments, F4 -125% RDF recorded the highest grain yield (56.4ha-1 and 57.1 q ha⁻¹),

followed by F3 and F5. The higher yield under F4 can be attributed to enhanced availability of essential nutrients, particularly nitrogen, which plays a central role in chlorophyll formation, enzyme activation and protein synthesis. Adequate nitrogen supply increases leaf area index and photosynthetic rate, leading to greater dry matter accumulation. This is reflected in higher biological yield (130.56 and 132.64 q ha⁻¹), indicating improved radiation interception and conversion efficiency. Furthermore, higher harvest index under F4 suggests efficient translocation of assimilates from vegetative to reproductive parts, which is a critical determinant of yield formation. In contrast, F1 Control recorded significantly lower yield due to nutrient deficiency, which restricted plant growth, reduced leaf area development and limited sink formation. These findings are consistent with Dobermann and Fairhurst (2000) [4] and Ladha et al. (2005) [8] , who emphasized that balanced fertilization enhances nutrient use efficiency and crop productivity. Recent studies by Jat et al. (2019) [5] and Liu et al. (2021) [10] further confirmed that optimized nutrient management improves physiological efficiency and yield performance in rice-based systems.

Interaction Effect (I × F) on Yield

The interaction data presented in Table 1(a) and 1(b) revealed a significant combined effect of irrigation and nutrient management on yield parameters, clearly indicating that these factors operate in a synergistic manner. The treatment combination IR2 × F4 recorded the highest grain yield (59.8 and 60.4 q ha⁻¹), straw yield (75.5 and 75.9 q ha⁻¹), biological yield (135.3 and 136.3 q ha⁻¹) and harvest index (44.20 and 44.31%). This superior performance can be attributed to resource synchronization, where IR2 ensures continuous soil moisture availability, enhancing nutrient solubility and uptake, while F4 provides adequate nutrient supply, improving physiological efficiency and metabolic activity. The combined effect results in enhanced radiation use efficiency, nutrient use efficiency and assimilate partitioning, ultimately leading to higher productivity. Conversely, the lowest yield observed under IR3 × F1 indicates that simultaneous limitation of water and nutrients severely restricts crop growth, confirming that these inputs are co-limiting factors. This aligns with the concept proposed by Cassman et al. (1998) [3] that yield is maximized only when nutrient supply is synchronized with crop demand under favorable environmental conditions. Similar interaction effects have also been reported by Kumar and Ladha (2011) [7] and more recently by Yadav et al. (2020) [14] , emphasizing the importance of integrated water and nutrient management in DSR systems.

Effect of Irrigation Scheduling and Nutrient Management on Economic Returns

The economic analysis presented in Table 2 indicated that both irrigation scheduling and nutrient management significantly influenced cost of cultivation, gross returns, net returns and B:C ratio, thereby determining overall profitability. Among irrigation treatments, IR2 recorded the highest net returns (₹131592 and ₹136484 ha-1) and B:C ratio (4.23 and 4.30). This was primarily due to higher grain yield and efficient utilization of water resources. Although IR1 produced comparable yields, its higher irrigation cost reduced profitability, whereas IR3 resulted in lower returns due to yield reduction despite lower input cost. This clearly suggests that economic efficiency depends on optimizing resource use rather than minimizing inputs alone. Similar findings have been reported by Tuong et al. (2005) [13] and Carrijo et al.

(2017) [2] , who emphasized that water-saving technologies must maintain yield stability to be economically viable.

Effect of Nutrient Management on Economics

Among nutrient treatments, F4-125% RDF recorded the highest net returns (₹143252 and ₹145628 ha⁻¹) and B:C ratio (4.51 and 4.57), indicating that increased fertilizer input was economically justified due to higher yield gains. The improved profitability under F4 suggests that investment in balanced fertilization enhances economic returns by improving productivity and resource-use efficiency.

Interestingly, F5 Farmers' practice also recorded a comparable B:C ratio, indicating that farmers tend to optimize input-output relationships based on field experience. However, lower returns under F1 highlight that nutrient deficiency significantly reduces profitability. These results are supported by Ladha et al. (2005) [8] and recent findings by Zhang et al. (2020) [16] , which indicate that economic optimum fertilizer levels often align closely with agronomic optimum under well-managed systems.

Interaction Effect (I × F) on Economics:

The interaction data presented in Table 2(a) clearly demonstrate that economic returns are maximized when irrigation and nutrient management are optimized simultaneously. The combination IR2 × F4 recorded the highest net returns (₹148310 and ₹149690 ha-1) along with a B:C ratio of 4.21, making it the most economically viable treatment. This clearly establishes that profitability is directly linked to productivity and resource-use efficiency, and not merely to cost reduction. In contrast, IR3 × F1 recorded the lowest economic returns, highlighting that low-input systems are not sustainable when they significantly reduce yield. These findings strongly support the concept of sustainable intensification, as proposed by Tilman et al. (2002) [12] , and further validated by recent studies (Jat et al., 2019; Yadav et al., 2020) [5,14] , which emphasize that optimal input management is essential for maximizing both productivity and profitability in modern agriculture.

Conclusion

The study demonstrates that productivity and profitability of direct seeded rice are strongly governed by the synergistic interaction between irrigation scheduling and nutrient management. The irrigation regime IR2, coupled with F4 (125% RDF), consistently optimized yield attributes, grain yield and economic returns, indicating superior resource-use efficiency. Conversely, sub-optimal input combinations resulted in marked yield and profit reductions. Thus, precise synchronization of water and nutrient supply is essential for achieving sustainable intensification and maximizing economic viability of DSR under Vindhya Plateau conditions.

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