Effect of irrigation scheduling on growth, yield, and water use efficiency and economics in wheat (Triticum aestivum L.)

Introduction

Wheat, scientifically known as Triticum aestivum L., is one of the most important food crops in India. It plays a key role in ensuring food security and supporting the income of people in rural areas. India is the second-largest producer of wheat in the world, with annual production ranging between 113 to 122 million tonnes over an area of 31 to 33 million hectares. However, the average yield remains around 3.6 tonnes per hectare (ISRO, 2025). The study conducted in the area of Eastern Rajasthan features a semi-arid climate marked by low and erratic rainfall (averaging 500-700 mm annually) alongside high evapotranspiration rates that surpass 1,500 mm per year. Achieving optimal wheat productivity under these conditions requires supplemental irrigation. Irrigation not only ensures adequate soil moisture but also influences nutrient availability, root development, and the expression of genetic potential for growth and yield (Prajapat et al., 2020; You et al., 2022) [1,2] . Despite the critical importance of irrigation, determining the optimal number and timing of irrigations remains a challenge for farmers and agronomists. Insufficient irrigation hampers crop development and lowers yields, whereas over-irrigation raises production expenses, depletes groundwater, and can worsen waterlogging and salinization (Molden, 2007) [3] . Furthermore, water use efficiency (WUE), defined as the crop biomass or yield produced per unit of water applied, is crucial for sustainable agriculture in water-scarce regions (You et al., 2022) [2] . Recent studies have shown that optimizing irrigation timing during critical growth stages substantially impacts both wheat yield and water use efficiency. Applying irrigation at the crown root initiation, tillering, jointing, and flowering stages has been demonstrated to optimize both productivity and water use efficiency (Khan et al., 2025; Ma et al., 2025) [4,5] . Against this background, the present investigation was undertaken with the objectives of: (i) evaluating the effect of varying irrigation schedules on growth parameters in wheat; (ii) assessing the influence of irrigation schedules on yield attributes and grain yield; (iii) analyzing the impact of irrigation schedules on water use efficiency and economic returns; and (iv) determining the correlation between irrigation frequency and grain yield under controlled field trial conditions.

Materials and Methods

Experimental site and design

A field experiment was conducted during the Rabi season of 2025-26 at the Agricultural Research Farm of Suresh Gyan Vihar University, Jaipur (26°48'37.6"N 75°51'31.4"E, elevation 390 m). The soil was silt loam in texture with pH 8.25, electrical conductivity 1.42 dS/m, and organic carbon 0.23%. The experimental design was a Randomized Block Design (RBD) with six treatments and four replications (24 plots). Each plot measured 4 m × 3 m. Wheat variety RAJ-1482 was sown on 17 November 2025 at 100 kg/ha with 21 cm row spacing. The recommended fertilizer dose (120:60:40 kg N:P 2 O 5 :K 2 O/ha) was applied at sowing, with nitrogen split-applied at sowing and tillering.

Treatment details and observations

Six irrigation treatments comprised progressive increases in the number of irrigations at critical growth stages: T 1: one irrigation at 25 DAS (crown root initiation); T 2: two irrigations at 25 and 45 DAS (tillering); T 3: three irrigations at 25, 45, and 65 DAS (jointing); T 4: four irrigations at 25, 45, 65, and 85 DAS (flowering); T 5: five irrigations at 25, 45, 65, 85, and 105 DAS (milk stage); T 6: six irrigations at 25, 45, 65, 85, 105, and 120 DAS (dough stage). Each irrigation applied 60 mm depth via conventional method, bringing soil moisture to field capacity. Growth parameters (plant height and number of tillers per plant) were recorded at each critical irrigation stage and at harvest from five randomly selected and tagged plants per plot. Yield attributes were determined at harvest: number of effective tillers per plant and number of grains per spike were counted on the five tagged plants, spikes per m 2 were counted in a 1 m 2 area, and test weight was determined from 1,000 grains. The entire plot was harvested on 25 th March 2026; grain and straw yields were recorded at 14% moisture content and expressed in kg/ha. The harvest index was calculated as the ratio of grain yield to biological yield (%). Water use efficiency (WUE, kg/ha-mm) was calculated as grain yield divided by total water input (rainfall + irrigation). Economic parameters including cost of cultivation, gross returns, net returns, and benefit-cost (B:C) ratio were computed based on prevailing market prices. Experimental data were statistically analyzed using ANOVA appropriate to RBD. Treatment means were compared using critical difference (CD) at 5% probability. Pearson correlation analysis was performed to determine the relationship between irrigation frequency and grain yield. All analyses were conducted using SPSS version 27.0.

Results and Discussion

Growth parameters

Plant height

Plant height increased significantly with each additional irrigation throughout the crop growth period. At 25 DAS (crown root initiation), plant heights were uniform across all treatments, ranging from 14.2 to 15.03 cm, with no significant differences observed (CD = NS). However, from 45 DAS onwards, the effects of irrigation became evident and progressively enhanced plant height at successive growth stages. At harvest (128 DAS), plant heights reached 74.3, 82.95, 88.38, 96.55, 96.63, and 96.79 cm for T 1 through T 6 , i.e. showing a significant linear increase with additional irrigations, respectively, with CD (5%) = 8.23 cm (Table 1). The effect plateaued beyond T 4 , indicating that soil moisture saturation beyond a certain threshold provides no further enhancement in plant height. Similar findings were reported by Kumar et al. (2023) [6] , who observed progressive increases in wheat plant height from 68.5 cm (one irrigation) to 88.4 cm (four irrigations) in the Indo-Gangetic Plains. The plateau in plant height beyond four irrigations suggests that additional water does not further increase height, likely due to an increase in reproductive growth.

Number of tillers per plant

Tiller production exhibited a similar pattern to plant height, with negligible differences among treatments at early growth stages (25 and 45 DAS). By 65 DAS (jointing stage), clear differentiation among treatments became apparent, with T 3 , T 4 , T 5 , and T 6 recording significantly higher tiller counts (4.62-4.71 tillers/plant) compared to T 1 and T 2 (4.11-4.55 tillers/plant). The number of tillers per plant at harvest were 3.75, 4.23, 4.70, 5.53, 5.50, and 5.55 for T 1 through T 6 , respectively, with CD (5%) = 0.35 (Table 2). Khan et al. (2025) [4] similarly observed that irrigation at critical stages increased wheat tillers from 3.2 (rainfed) to 5.8 (four irrigations). The absence of significant differences in effective tillers between T 5 and T 6 suggests that beyond four irrigations, additional water does not substantially improve tiller viability, possibly due to increased lodging risk and tiller mortality.

Yield attributes

All yield attributes were significantly improved by additional irrigations. Effective tillers per plant (tillers bearing grain-producing spikes) showed a similar trend, increasing from 3.34 (T 1 ) to 5.28 (T 6 ), with CD (5%) = 0.55. Notably, no significant difference in effective tillers was observed between T 5 and T 6 , indicating yield plateau beyond four irrigations. The number of spikes per m 2 increased progressively from 178.8 (T 1 ) to 304.5 (T 6 ), with CD (5%) = 27.39. Similarly, the number of grains per spike showed a significant increase from 31.2 (T 1 ) to 46.8 (T 6 ), with CD (5%) = 3.14. Test weight (1000-grain weight) increased marginally but significantly from 39 g (T 1 ) to 42 g (T 6 ), with CD (5%) = NS (Table 3). Ma et al. (2025) [5] demonstrated that irrigation at flowering stage specifically enhanced grain number per spike in winter wheat. The modest improvement in test weight suggests that irrigation's primary benefit resides in producing greater numbers of reproductive structures rather than increasing individual grain size, indicating that grain-filling conditions were generally adequate across most irrigation schedules.

Grain yield, straw yield and harvest index

Grain yield increased progressively and significantly with each additional irrigation from T 1 to T 4 . Grain yields were 2304, 2905, 3728, 4614, 4722, and 4855 kg/ha for T 1 through T 6 , respectively, with CD (5%) = 338.47. The yield increase from T 1 to T 4 represented a substantial improvement, a gain of considerable practical significance. However, the yield increment from T 4 to T 6 was minimal clearly indicating that beyond four irrigations, grain yield does not increase significantly (Table 4). Straw yield followed a similar pattern, increasing from 3390 kg/ha (T 1 ) to 6181 kg/ha (T 6 ), with T 4 , T 5 and T 6 showing at-par straw yields. The harvest index (grain yield/biological yield) showed a relatively stable increase across treatments, ranging from 40.4% to 44% indicating that additional irrigation does not substantially alter the partitioning of photosynthates between grain and straw (Table 4). Kumar et al. (2023) [6] reported similar patterns, with maximum wheat yields achieved at three to four well-timed irrigations, beyond which further irrigation frequency provided diminishing returns. Prajapat et al. (2020) [1] reported wheat yields of 2.3 t/ha (one irrigation) to 3.5 t/ha (four irrigations) under semi-arid eastern Rajasthan conditions, closely paralleling the current results.

Water use efficiency

Water use efficiency (WUE) exhibited a marked inverse relationship with irrigation frequency. The total water input (rainfall + irrigation) was 76. 6, 136.6, 196.6, 256.6, 316.6, and 376.6 mm for T 1 through T 6 , respectively. Water use efficiency values were 30.08, 21.27, 18.96, 17.98, 14.92, and 12.89 kg/ha-mm for T 1 through T 6 , respectively, with CD (5%) = 2.85 kg/ha-mm. Water use efficiency was highest under T 1 (38.08 kg ha -1 mm -1 ), which received the lowest irrigation amount (76 mm) (Table 5). Although increased irrigation improved grain production, the increase in yield was not proportional to the additional irrigation water applied, resulting in a progressive decline in WUE with increasing irrigation levels. Molden (2007) [3] explained this phenomenon as a consequence of the law of diminishing marginal returns: as soil moisture approaches saturation, the marginal productivity of additional water declines sharply because subsequent water beyond the plant's evapotranspiration requirement is lost as non-beneficial evaporation or percolation. You et al. (2022) [2] reported similar WUE patterns in winter wheat, with maximum WUE of 32.5 kg/ha-mm under rainfed conditions declining to 14.8 kg/ha-mm under a six-irrigation schedule.

Effect of irrigation scheduling on economics

The cost ratio improved from 0.96 (a loss-making proposition) to 2.62 under T 6 , with T 4 and T 5 (2.58 and 2.59) statistically at par with T 6 . This indicates that despite its lower WUE, T 6 remained the most profitable treatment because the value of the additional grain yield far outweighed the marginal cost of the extra irrigation (Table 6). These findings are consistent with Kumar et al. (2023) [6] , who reported that irrigation scheduling close to full crop water requirement maximized net returns and benefit-cost ratio in wheat, even though the highest water-use efficiency was recorded under comparatively lower irrigation levels.

Correlation analysis: irrigation frequency and grain yield

Pearson correlation analysis revealed a strong positive and highly significant correlation between irrigation frequency (number of irrigations) and grain yield under controlled field trial conditions: r = 0.826 (p < 0.001, n = 24). This correlation coefficient represents a strong positive linear relationship, demonstrating that approximately 68.2% of the variation in grain yield (R 2 = 0.682) could be explained by irrigation frequency alone under controlled field conditions. Each additional irrigation at the prescribed critical growth stages progressively increased grain yield in a highly predictable manner, validating contemporary irrigation management theory and the importance of precise irrigation scheduling for maximizing wheat productivity. Khan et al. (2025) [4] and You et al. (2022) [2] have similarly established strong correlations (r > 0.80) between irrigation frequency and wheat yield in semi-arid environments, confirming the applicability of this relationship across diverse agro-climatic zones.

Conclusion

This field experiment demonstrates that irrigation scheduling significantly influences wheat growth, yield, water use efficiency, and economics. The strong correlation (r = 0.826) between irrigation frequency and grain yield under controlled conditions validates the importance of strategic irrigation scheduling. Plant height and tiller production increased progressively with irrigation, yielding an improvement in grain yield from T 1 to T 4 . However, diminishing returns beyond four irrigations (T 4 ) suggest an optimization point exists. Water use efficiency exhibited an inverse relationship with irrigation frequency, highlighting the trade-off between maximizing absolute yield and maximizing water productivity. Economic analysis demonstrated that four well-timed irrigations at critical growth stages (25, 45, 65, and 85 DAS) provide optimal re-turns (₹122,005/ha net returns, B:C ratio 2.58), balancing productivity, water conservation, and economic viability. This recommendation is particularly relevant for groundwater-scarce regions facing rising irrigation costs. Future research should validate these findings across multiple seasons and locations to establish robust recommendations for irrigation management in wheat under diverse agro-climatic and socio-economic conditions.

References

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7. Indian Space Research Organisation. Crop condition and yield assessment. 2025. How to cite this article: Suri M, Qidwai S, Chaturvedi V, Yadav I, Sarkar D, Dhayal L. Effect of irrigation scheduling on growth, yield, and water use efficiency and economics in wheat (Triticum aestivum L.). International Journal of Research in Agronomy. 2026;9(9):1458-1462. doi: https://www.doi.org/10.33545/261806
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