Response of wheat (Triticum aestivum L.) to high density planting & foliar application of seaweed extract and amino acid-based biostimulants

Introduction

Wheat (Triticum aestivum L.) is one of the most important cereal crops in the world and plays a significant role in ensuring food and nutritional security. In India, wheat is the second most important food grain crop after rice and contributes substantially to the agricultural economy. The crop provides carbohydrates, proteins, vitamins and minerals required for human nutrition and is widely used for preparation of flour, bread, chapatti, biscuits and other food products. In Punjab, wheat is the principal Rabi cereal crop and forms the backbone of the state's food grain production system. However, wheat productivity is often affected by improper crop management practices, nutrient imbalance and inefficient utilization of available resources. Therefore, adoption of suitable agronomic practices is necessary to sustain higher productivity and profitability. Plant geometry and row spacing are important agronomic factors affecting growth and yield of wheat. Optimum spacing ensures proper plant distribution and efficient utilization of sunlight, soil moisture and nutrients. Appropriate row spacing promotes better tillering, root development and dry matter accumulation, whereas excessively narrow or wider spacing may adversely affect crop productivity due to increased competition or reduced plant population (Peake et al., 2020) [9] . Hence, identification of suitable row spacing is essential for improving growth and yield attributes of wheat under different agro-climatic conditions. In recent years, foliar application of bio-stimulants has gained considerable attention as an ecofriendly approach to enhance crop productivity. Bio-stimulants such as seaweed extracts, amino acids and humic substances improve nutrient uptake, photosynthetic efficiency and tolerance against abiotic stress. Foliar application at critical growth stages provides rapid absorption of growth-promoting substances and improves crop vigor and yield performance (Nardi et al., 2016) [7] . Similar synergistic effects of seaweed-based biostimulants with nutrient management on wheat yield attributes were also reported by (Toppo et al., 2024 and Sharma et al.,2025) [18,15] . The combined effect of optimum row spacing and foliar application of bio-stimulants may significantly influence growth, yield and economics of wheat through efficient resource utilization and improved physiological activity. Comparable improvements in irrigated wheat productivity under seaweed extract and nutrient application were observed by Das et al., (2026) [5] . However, limited information is available regarding their combined effect under Punjab conditions. Therefore, the present investigation was undertaken to evaluate the influence of row spacing and foliar application of bio-stimulants on growth, yield and economics of wheat (Rouphael & Colla 2024) [13] .

Materials and Methods

Experimental Site and Season

The field experiment was conducted at the Agricultural Research Farm, Guru Kashi University, Talwandi Sabo, Bathinda, Punjab, India (29°57'N, 75°7'E; altitude 213 m above sea level) during the Rabi season of 2025 to study the influence of high-density planting and foliar application of bio-stimulants on growth, yield and economics of wheat (Triticum aestivum L.). The site has a semi-arid subtropical climate with mild winters and warm summers, from November 2025 to April 2026. Maximum temperature peaked at 38°C in April, while the minimum temperature dropped to 8°C in January. The total rainfall received during the experimental period was 58 mm, with relative humidity ranging from 24% to 49%. [6] EC (dS m⁻¹) 0.81 Conductivity meter, 1:2 soil:water suspension (Jackson 1967) [6] Organic carbon (%) 0.48 Walkley and Black rapid titration (Jackson 1967) [6] Available N (kg ha⁻¹) 119.2 Alkaline KMnO₄ method (Subbiah & Asija 1956) [17] Available P₂O₅ (kg ha⁻¹) 17.95 0.5 N NaHCO₃ extractable (Olsen et al., 1954) [8] Available K₂O (kg ha⁻¹) 173.4 1N NH₄OAc extractable (Jackson 1967) [6]

Experimental design and treatments

A Randomized Block Design (RBD) comprising nine treatments with three replications was adopted for the experiment. Each experimental plot measured 5 m × 4 m gross plot size with a net plot area of 3.8 m × 3 m. The wheat variety PBW-826, a highyielding and heat-tolerant cultivar developed by Punjab Agricultural University (PAU), Ludhiana for timely-sown irrigated conditions, was used in the study. The variety is known for its superior grain quality, rust resistance and high yield potential, and is suitable for cultivation in the North-Western and North-Eastern Plains Zones of India (Sharma et al., 2025) [15] . The recommended dose of fertilizer (RDF) for wheat cultivation in Punjab is 120:60:40 kg N:P:K ha⁻¹ (PAU, 2025). The treatments consisted of different concentrations of amino acid-based plant growth regulator and seaweed extract applied as foliar spray under high-density planting conditions. The treatments comprised T 1 -Control (recommended density without bio-stimulant spray), T 2 -High density planting + Amino Acid Based PGR @ 2 ml L⁻¹ + Seaweed Extract @ 2 ml L⁻¹, T 3 -High density planting + Amino Acid Based PGR @ 2 ml L⁻¹ + Seaweed Extract @ 4 ml L⁻¹, T 4 -High density planting + Amino Acid Based PGR @ 2 ml L⁻¹ + Seaweed Extract @ 6 ml L⁻¹, T 5 -High density planting + Amino Acid Based PGR @ 4 ml L⁻¹ + Seaweed Extract @ 2 ml L⁻¹, T 6 -High density planting + Amino Acid Based PGR @ 4 ml L⁻¹ + Seaweed Extract @ 4 ml L⁻¹, T 7 -High density planting + Amino Acid Based PGR @ 4 ml L⁻¹ + Seaweed Extract @ 6 ml L⁻¹, T 8 -High density planting + Amino Acid Based PGR @ 6 ml L⁻¹ + Seaweed Extract @ 2 ml L⁻¹, T 9 -High density planting + Amino Acid Based PGR @ 6 ml L⁻¹ + Seaweed Extract @ 4 ml L⁻¹ and T 10 -High density planting + Amino Acid Based PGR @ 6 ml L⁻¹ + Seaweed Extract @ 6 ml L⁻¹. Foliar sprays were applied at 30-35, 50-55 and 70-75 days after sowing as per treatment details. Recommended agronomic practices were uniformly followed for all treatments throughout the crop growth period.

Agronomic management

The experimental field was prepared by giving pre-sowing irrigation followed by ploughing and harrowing to obtain a fine tilth. Wheat seeds with high germination percentage were sown under high-density planting using narrow row spacing to maintain a higher plant population, while the control treatment was maintained under recommended plant spacing. Phosphorus (60 kg P₂O₅ ha⁻¹ as single superphosphate) and potassium (40 kg K₂O ha⁻¹ as muriate of potash) were applied basally at the time of final land preparation. Nitrogen was applied through urea in three equal splits: one-third at sowing, one-third at crown root initiation stage, and the remaining one-third at tillering stage. The experiment comprised foliar application treatments of an amino acid-based plant growth regulator and seaweed extract at different concentrations under high-density planting conditions. Foliar sprays were applied at 30-35, 50-55 and 70-75 days after sowing (DAS) according to the treatment schedule. The treatments included different combinations of amino acid-based PGR (2, 4 and 6 mL L⁻¹) and seaweed extract (2, 4 and 6 mL L⁻¹), along with an untreated control. Irrigations were applied according to crop requirements with special emphasis on crown root initiation, tillering, booting, flowering and grain filling stages. Weed management was carried out through manual weeding and recommended herbicide application at appropriate stages. Plant protection measures were adopted as needed to manage insect pests and diseases during the crop season.

Observations Recorded

Growth observations were recorded at 30, 60, 90 and 120 DAS, as well as at harvest, for five randomly tagged plants from each plot. Number of tillers plant⁻¹ was counted at different growth phases and at maturity. Chlorophyll content was measured using a SPAD meter. Crop growth rate (CGR) and relative growth rate (RGR) were estimated using conventional methods. At harvest, yield attributes including effective tillers m⁻², spikes plant⁻¹, spike length (cm), grains spike⁻¹ and test weight (1000grain weight, g) were measured. Grain yield, straw yield and biological yield were represented in q/ha. Harvest index (HI) was determined using the following formula: HI (%) = (grain yield / biological yield) × 100.

Economic study of the treatments was carried out by calculating cost of cultivation, gross returns, net returns and benefit:cost (B:C) ratio (B:C ratio = gross return / cost of cultivation).

Statistical Analysis

Data were analyzed using analysis of variance (ANOVA) for a randomized block design (RBD) with three replications, following the procedure described by Cochran and Cox (1967) [3] using COSTAT software. Treatment means were compared at the 5% level of significance using the critical difference (CD) test. Pearson's correlation coefficients were computed between grain yield, straw yield, and other observed parameters at different growth stages of wheat to assess the relationship among traits under varying nutrient management practices. All statistical comparisons were performed at P = 0.05.

Results and Discussion

Growth Parameters

The data presented in Table 3 The crop growth rate during the final growth period (90-120 DAS) was also significantly influenced by foliar nutrition and plant growth regulators. The highest CGR was recorded in T 10 (6 mL L⁻¹ amino acid PGR + 6 mL L⁻¹ seaweed extract) (150 g m⁻² day⁻¹), followed by T 9 (Amino Acid Based PGR @ 6 ml L⁻¹ + Seaweed Extract @ 4 ml L⁻¹) (148 g m⁻² day⁻¹), whereas the lowest value was observed in T 1 (recommended density without bio-stimulant spray) (120 g m⁻² day⁻¹). The higher CGR under treated plots may be associated with enhanced photosynthetic activity, improved nutrient uptake, and greater dry matter accumulation. Relative growth rate gradually declined with crop maturity; however, treated plots maintained significantly higher RGR values than the control. Treatment T 10 (6 mL L⁻¹ amino acid PGR + 6 mL L⁻¹ seaweed extract) recorded the highest RGR (0.032 g g⁻¹ day⁻¹), while T 1 (recommended density without bio-stimulant spray) showed the lowest value (0.025 g g⁻¹ day⁻¹). Overall, the combined application of Seaweed extract and amino acid PGR positively influenced crop growth, physiological performance, and biomass accumulation, thereby improving wheat productivity under high-density planting conditions.

Yield Attributes and Yield

The data presented in Table 3 showed that foliar application treatments had a positive and significant effect on the yield and yield-related traits of wheat grown under high-density planting conditions. Clear differences among the treatments were observed for parameters such as 1000-grain weight, grain yield, straw yield, and harvest index, indicating the beneficial role of biostimulants and plant growth regulators in improving crop growth and productivity. Among all the treatments, T 10 (6 mL L⁻¹ amino acid PGR + 6 mL L⁻¹ seaweed extract) performed the best by recording the highest 1000-grain weight (43.87 g), grain yield (52.53 q ha⁻¹), straw yield (52.52 q ha⁻¹), and harvest index (50.0%). On the other hand, the control treatment T 1 (recommended density without bio-stimulant spray) showed the lowest values, with 38.42 g 1000-grain weight, 38.34 q ha⁻¹ grain yield, 42.37 q ha⁻¹ straw yield, and a harvest index of 47.5%. The improvement in grain weight and grain yield under the treated plots may be due to better movement of photosynthates from leaves to grains, which helped in proper grain filling and increased accumulation of assimilates. The foliar treatments also appeared to improve tillering, chlorophyll content, and overall photosynthetic activity, resulting in greater dry matter production and better utilization of nutrients for grain development. Similarly, the higher straw yield recorded in treated plots reflected improved vegetative growth, increased plant height, and greater biomass accumulation. The higher harvest index observed in T 10 (6 mL L⁻¹ amino acid PGR + 6 mL L⁻¹ seaweed extract) further indicated that the plants were more efficient in converting total biomass into economic yield, mainly through better partitioning of assimilates towards grain production rather than vegetative parts. Overall, the combined application of Seaweed extract and amino acid PGR proved highly effective in enhancing crop growth, grain quality, biomass production, and yield performance of wheat under high-density planting conditions. These findings highlight the importance of foliar nutrition and amino-acid-based plant growth regulators in improving wheat productivity and supporting sustainable crop production practices.

Economic Analysis

The economic analysis revealed that the cost of cultivation increased from ₹45,600 ha⁻¹ in T 1 (recommended density without bio-stimulant spray) to ₹53,900 ha⁻¹ in T 10 (6 mL L⁻¹ amino acid PGR + 6 mL L⁻¹ seaweed extract) due to higher input application, foliar sprays, and intensive crop management practices (Table 4). Despite the increased cultivation cost, treated plots recorded higher economic returns than the control. Gross return ranged from ₹99,123.90 ha⁻¹ in T 1 (recommended density without bio-stimulant spray) to ₹1,35,790.05 ha⁻¹ in T 10 (6 mL L⁻¹ amino acid PGR + 6 mL L⁻¹ seaweed extract) (Table 4) calculated based on the prevailing market price of wheat at ₹2,585 q⁻¹, indicating that foliar nutrition and plant growth regulator application significantly improved crop productivity and profitability. Similarly, net return increased from ₹53,523.90 ha⁻¹ in T 1 (recommended density without bio-stimulant spray) to ₹81,890.05 ha⁻¹ in T 10 (6 mL L⁻¹ amino acid PGR + 6 mL L⁻¹ seaweed extract) (Table 4), reflecting the beneficial effect of enhanced yield over additional input costs. The highest benefitcost ratio was also observed in T 10 (6 mL L⁻¹ amino acid PGR + 6 mL L⁻¹ seaweed extract) (2.52), followed by T 8 (Amino Acid Based PGR @ 6 ml L⁻¹ + Seaweed Extract @ 2 ml L⁻¹) (2.51) and T 7 (Amino Acid Based PGR @ 4 ml L⁻¹ + Seaweed Extract @ 6 ml L⁻¹) (2.50), demonstrating superior economic efficiency under these treatments (Table 4). In contrast, the control treatment recorded the lowest B:C ratio (2.17), indicating comparatively lower profitability. These findings suggest that the application of foliar sprays and growth regulators improved input-use efficiency, yield, and economic returns in wheat cultivation under high-density planting conditions. Similar results were reported by Rajala and Peltonen-Sainio (2000) [12] and Shakirova et al., (2003) [14] , who observed enhanced profitability and economic efficiency with improved nutrient and growth regulator management practices.

Acknowledgement

AcknowledgementsThe authors thank the Department of Agronomy, Faculty of Agriculture, Guru Kashi University, Talwandi Sabo, for providing experimental and analytical facilities. The technical assistance of field, staff, and laboratory technicians is sincerely

References

1. Ali O, Ramsubhag A, Jayaraman J. Biostimulant properties of seaweed extracts in crop production systems. Plants. 2024;13(2):244. doi:10.3390/plants13020244.
2. Calvo P, Nelson L, Kloepper JW. Agricultural uses of plant biostimulants. Plant Soil. 2014;383:3-41. doi:10.1007/s11104-014-2131-8.
3. Cochran WG, Cox GM. Experimental designs. 2nd ed. John Wiley & Sons; 1967.
4. Colla G, Hoagland L, Ruzzi M, Cardarelli M, Bonini P, Canaguier R. Biostimulant action and plant responses: A review. Biol Agric Hortic. 2017;35(2):109-119. doi:10.1080/01448765.2017.1304016.
5. Das N, Sarkar M, Mandal A, Dasannavar G. Seaweed extract under different doses of NPK on productivity of irrigated wheat. Int J Res Agron. 2026;9(3):53-63. doi:10.33545/2618060X.2026.v9.i3a.4993.
6. Jackson ML. Soil chemical analysis. Prentice Hall of India Pvt. Ltd., New Delhi; 1967.
7. Nardi S, Pizzeghello D, Schiavon M, Ertani A. Plant biostimulants: Physiological responses induced by protein hydrolyzed-based products. J Agric Food Chem. 2016;64(36):6984-6992. doi:10.1021/acs.jafc.6b01929.
8. Olsen SR, Cole CV, Watanabe FS, Dean LA. Estimation of available phosphorus in soils by extraction with sodium bicarbonate. USDA Circular No. 939; 1954.
9. Peake AS, Bell KL, Fischer RA, Gardner M, Das BT, Poole N, Mumford M. Cultivar × management interaction to reduce lodging and improve grain yield of irrigated spring wheat: Optimising plant growth regulator use, N application timing, row spacing and sowing date. Front Plant Sci. 2020;11:401. doi:10.3389/fpls.2020.00401.
10. Peake AS, Gillingham O, Norton RM. Optimising row spacing and plant population in wheat. Crop Pasture Sci. 2020;71(6):543-552. doi:10.1071/CP19503.
11. Punjab Agricultural University. Package of practices for crops of Punjab: Rabi 2025-26. Vol. 42, No. 2. Ludhiana, Punjab: Directorate of Extension Education, Punjab Agricultural University; 2025.
12. Rajala A, Peltonen-Sainio P. Manipulating yield potential in cereals using plant growth regulators. In: Basra AS, editor. Plant Growth Regulators in Agriculture and Horticulture. Food Products Press; 2000. p. 27-70.
13. Rouphael Y, Colla G. Plant biostimulants for sustainable agriculture: Recent advances and future perspectives. Front Plant Sci. 2024;15:1352145. doi:10.3389/fpls.2024.1352145.
14. Shakirova FM, Sakhabutdinova AR, Bezrukova MV, Fatkhutdinova RA, Fatkhutdinova DR. Changes in the hormonal status of wheat seedlings induced by salicylic acid and salinity. Plant Sci. 2003;164:317-322.
15. Sharma P, Kaur H, Singh B. Influence of foliar biostimulants on growth and productivity of wheat under Punjab conditions. Indian J Agron. 2025;70(1):78-84.
16. Singh J, Kaur P, Sidhu HS. High-density planting and foliar nutrition effects on wheat productivity. Agric Res J. 2024;61(3):401-408.
17. Subbiah BV, Asija GL. A rapid procedure for determination of available nitrogen in soils. Curr Sci. 1956;25:259-260.
18. Toppo N, David AA, Thomas T, Singh R, Reddy IS. Synergistic effects of inorganic and organic fertilizers with Kappaphycus alvarezii biostimulant on yield attributes of wheat. Int J Res Agron. 2024;7(9):260-264. doi:10.33545/2618060X.2024.v7.i9d.1516.