Bio efficacy of biopolymers and bio stimulants in enhancing growth and productivity of Wheat (Triticum Aestivum L. Emend. Fiori & Paol)

Introduction

Wheat is one of the most important cereal crops in the world and serves as a staple food for a large part of the global population. It is widely known as the "King of cereals" due to its major contribution to food security. Wheat is cultivated on about 200-225 million hectares globally and provides nearly one-fifth of total calories and about one-fourth of grain-derived energy worldwide (Erenstein et al., 2022; Tosh et al., 2019) [4,17] . Over time, wheat production has increased significantly, from 247.7 million tonnes in 1961 to about 755 million tonnes in 2020, showing continuous improvement in productivity. India ranks second in wheat production after China, with major growing states including Uttar Pradesh, Punjab, Haryana, Madhya Pradesh, and Rajasthan (Jat et al., 2021) [9] . However, despite achieving self-sufficiency after the Green Revolution, wheat productivity has stagnated in many regions due to factors such as heat stress, limited water availability, and disease problems (Agrawal et al., 2012) [1] . Wheat grain is highly nutritious and provides essential carbohydrates, proteins, vitamins, and minerals required for human health. It contains about 13% protein, which is higher than rice and maize, along with important gluten proteins such as gliadins and glutenins. Whole wheat is also rich in dietary fiber, B-group vitamins, vitamin E, and minerals like iron, zinc, magnesium, and phosphorus (Shewry et al., 2012; Iqbal et al., 2022) [15,8] . Micronutrients such as zinc and copper play an important role in plant growth and development. Zinc is essential for hormone production, enzyme activity, and nutrient balance, and its deficiency leads to poor growth and reduced yield. Copper is involved in key physiological processes such as photosynthesis, respiration, and protection against oxidative stress. The level of micronutrients in wheat grain depends on factors like genotype, environmental conditions, and crop management practices (Murphy et al., 2008; Szira et al., 2014) [13,16] . Low wheat productivity is often linked to improper nutrient management and lack of knowledge about correct fertilizer application methods. In this regard, foliar application is considered an effective method of supplying nutrients directly to plant leaves, which improves nutrient use efficiency and reduces losses. Recently, the use of biostimulants has gained importance in sustainable agriculture. Substances such as humic acid improve nutrient uptake, enhance plant metabolism, and increase tolerance to environmental stresses (Mehrinfar et al, 2022) [10] . Similarly, amino acid-based biostimulants and compounds like glycine betaine help in improving plant growth and stress resistance (Calvo et al., 2014) [2] . Salicylic acid is an important plant hormone that regulates plant defense mechanisms and helps plants tolerate abiotic stresses such as drought and heat. Among different biostimulants, chitosan has emerged as a promising natural compound for agricultural use. It is derived from seafood waste and is biodegradable, non-toxic, and environmentally safe. Chitosan application improves plant growth, enhances enzyme activity, supports nitrogen metabolism, and increases the production of protective compounds like phenolics and flavonoids (Mondal et al., 2012; Saad et al., 2022) [12,14] . In addition, it helps plants tolerate stress conditions and improves overall crop productivity.

Materials and Methods

The experimental trial was conducted at the Instructional Farm, College of Agriculture Bhilwara (Rajasthan) during Rabi, 2024-2025. Soil samples (0-30 cm depth) were collected before sowing and analyzed for physico-chemical properties. The soil was clay loam in texture, slightly alkaline (pH 7.32) with electrical conductivity of 0.828 dS m -1 . It had medium organic carbon (0.51%), low available nitrogen (220.5 kg ha -1 ), medium available phosphorus (15.7 kg ha -1 ) and high available potassium (310.6 kg ha -1 ). The experiment was laid out in a randomized block design with three replications, the experiment consisted of 11 treatments including absolute control, water spray and different concentrations of chitosan-based biopolymers and biostimulants. Treatments involved foliar application of chitosan alone and in combination with Zn and Cu at 1, 5 and 10 ml l -1 . All foliar sprays were applied at 25, 50 and 75 DAS. The gross and net plot sizes were 5.0 x 4.0 m and 4.5 m x 3.5 m, respectively, with a spacing of 22.5 cm (R*R) and the wheat variety Raj-4238 was used at a seed rate of 100 kg ha -1 . The recommended dose of fertilizer NPK (120: 60: 40 kg ha -1 ) was supplied through urea, DAP and MOP, with half of nitrogen applied as basal along with the full dose of phosphorus, potassium and sulphur and the remaining nitrogen top-dressed at 30 DAS. Standard agronomic practices such as gap filling, thinning, weeding, irrigation and plant protection were carried out as required. Yield attributes such as number of effective tillers, ear length and grains per ear were recorded from randomly selected plants at maturity. Test weight was determined from the weight of 1000 grains. Grain yield was recorded after threshing and expressed as kg ha -1 . Straw yield was obtained by subtracting grain yield from biological yield, while biological yield was calculated from total biomass per plot. Harvest index was computed as the ratio of grain yield to biological yield and expressed in percentage.

Results and Discussion

Yield Attributes

Yield contributing traits such as ear length, number of grains per ear and test weight were significantly influenced by foliar application of biopolymers and bio-stimulants (Table 4.6). The maximum ear length (13.90 cm) was recorded under T₁₀ (Chitosan-Cu-Zn @ 5 ml l -1 ), whereas the absolute control (T₁) produced comparatively lower values, showing an increase to the tune of 127.9 per cent. Similarly, the number of grains per ear increased from control to 54.92 under T₁₀, reflecting an improvement of 87.4 per cent. The improved yield attributes under chitosan-Cu-Zn bio-stimulant may be attributed to enhanced availability and efficient utilization of micronutrients, particularly zinc and copper, during reproductive stages. Zinc improved pollen viability, fertilization and grain setting, resulting in higher grains per ear, while copper supported photosynthetic activity and carbohydrate supply. Chitosan further enhanced micronutrient absorption, membrane permeability and stress tolerance, thereby sustaining reproductive development. The findings were supported by of Dubey et al. (2020) [3] , Zheng et al. (2019) [18] , Mohan et al. (2024) [11] . Test weight also followed a similar trend, with the highest value (43.25 g) recorded under T₁₀ as compared to control, showing an increase of 12.8 per cent. Lower values were observed under water spray (2-3% increase) and chitosan alone (5-8% increase), indicating that micronutrient enrichment further enhanced seed development. The improvement in test weight may be due to better assimilate translocation and increased accumulation of photosynthates under balanced nutrient supply. Similar findings have also been reported in wheat and other crops where combined application of bio-stimulants and micronutrients improved yield attributes and seed quality (Gobel et al. 2024)

Yield

Grain yield, straw yield and biological yield of wheat were significantly influenced by foliar application of biopolymers and bio-stimulants, whereas harvest index remained non-significant (Table 4.7). The maximum grain yield (5499.27 kg ha -1 ) was recorded under T₁₀ (Chitosan-Cu-Zn @ 5 ml l -1 ), which was superior over control treatments and other combinations, showing an increase of 84.1 per cent over absolute control. Similarly, straw yield increased to 6638.97 kg ha -1 and biological yield to 12138.23 kg ha -1 under T₁₀, indicating substantial improvement over lower treatments. The increase in yield may be attributed to enhanced nutrient availability and efficient utilization of micronutrients, particularly zinc and copper, which improved photosynthetic activity, assimilate production and overall plant growth. Chitosan might have further enhanced nutrient absorption, metabolic activity and stress tolerance, thereby contributing to higher biomass accumulation and yield. Harvest index was not significantly influenced by different treatments. However, numerically higher values were observed under T₆ (45.33%), T₈ (45.33%) and T₁₀ (45.29%), while lower values were recorded under control treatments. The increase in grain, straw and biological yield may be attributed to improved nutrient use efficiency, enhanced physiological activity and better assimilate production under chitosan-based bio-stimulant application. Improved micronutrient availability might have stimulated photosynthesis and metabolic processes, resulting in higher biomass and grain yield. The relatively higher harvest index under chitosan-Cu-Zn treatment indicates better source-sink relationship and efficient translocation of photosynthates to grains. The variation among treatments was marginal, indicating that partitioning of total biomass into grain remained almost uniform. The findings were supported by Haydar et al. (2024) [6] and Hossain et al. (2024) [7] .

Conclusion

The experimental trial conducted at the Instructional Farm, College of Agriculture, Bhilwara (Rajasthan) during Rabi, 2024-2025 demonstrated that foliar application of chitosan-based biopolymers and micronutrient-enriched bio-stimulants significantly influenced yield attributes and productivity of wheat. Among the treatments, chitosan-Cu-Zn bio-stimulant @ 5 ml l -1 (T₁₀) was found to be the best treatment, producing the highest grain yield (5499.27 kg ha -1 ) along with improved ear length, number of grains per ear and test weight. Enhanced reproductive efficiency, better grain filling and higher biomass production under this treatment highlighted the importance of combined application of chitosan with micronutrients for maximizing wheat productivity under the agro-climatic conditions of Rajasthan.

References

1. Agrawal PK, Gupta RK, Jat ML, Singh R. Wheat productivity trends and prospects in India. Indian J Agric Sci. 2012;82(4):331-336.
2. Calvo L, Nelson JW, Kloepper JW. Agricultural uses of plant biostimulants. Plant Soil. 2014;383:3-41.
3. Dubey R, Pathak H, Chakrabarti B, Singh S, Gupta DK, Harit RC. Impact of terminal heat stress on wheat yield in India and options for adaptation. Agric Syst. 2020;181:102826.
4. Erenstein O, Jaleta M, Sonder K, Donovan J. Global trends in wheat production, trade, and consumption. Glob Food Secur. 2022;32:100617. doi:10.1016/j.gfs.2021.100617.
5. Göbel M, Dulal S, Sommer L, Weinmann M, Al Mamun MA, Ahmed A, et al. Protective potential of selected microbial and non-microbial biostimulants against Zymoseptoria tritici leaf blotch in winter wheat as affected by the form of supply. Front Plant Sci. 2024;15.
6. Haydar MS, Ghosh D, Roy S. Slow and controlled release nanofertilizers as an efficient tool for sustainable agriculture: Recent understanding and concerns. Plant Nano Biol. 2024;7:100058.
7. Hossain S, Paul AK, Hasan MM, Prodhan DU. Impact of foliar zinc and boron application on wheat yield, quality and post-harvest soil properties. Int J Biosci. 2024;25:219-227.
8. Iqbal A, Khalid N, Ateeq N, Khan MI. Nutritional significance and health benefits of wheat and whole grains: A comprehensive review. Crit Rev Food Sci Nutr. 2022;62(3):654-670.
9. Jat ML, Gupta R, Kumar M. Wheat in South Asia: Trends, challenges, and opportunities. Mexico: CIMMYT; 2021.
10. Mondal MMA, Malek MA, Puteh AB, Ismail MR, Ashrafuzzaman M, Naher L. Effect of foliar application of chitosan on growth and yield in okra. Aust J Crop Sci. 2012;6(5):918-921.
11. Murphy KM, Reeves PG, Jones SS. Relationship between yield and mineral nutrient concentrations in historical and modern spring wheat cultivars. Euphytica. 2008;163(3):381-390.
12. Saad AM, Alabdali AYM, Ebaid M, Salama E, El-Saadony MT, Selim S, et al. Impact of green chitosan nanoparticles fabricated from shrimp processing waste as a source of nano nitrogen fertilizers on the yield quantity and quality of wheat (Triticum aestivum L.) cultivars. Molecules. 2022;27(17):5640.
13. Shewry PR, Piironen V, Lampi AM, Edelmann M, Kariluoto S, Nurmi T, et al. The healthgrain wheat diversity screen: Effects of genotype and environment on phytochemicals and dietary fiber components. J Agric Food Chem. 2012;60(47):11839-11849.
14. Szira F, Monostori I, Galiba G, Rakszegi M, Bálint AF. Micronutrient contents and nutritional values of commercial wheat flours and flours of field-grown wheat varieties-a survey in Hungary. Cereal Res Commun. 2014;42(2):294302.
15. Tosh J, Mishra JS, Sharma RK. Wheat production in India: Constraints and opportunities. J Wheat Res. 2019;11(2):1-9.