Effect of humic acid on growth, yield and quality of wheat

Introduction

Wheat (Triticum aestivum L.) is one of the most important cereal crops globally and plays a crucial role in ensuring food and nutritional security. In India, it is a major rabi crop cultivated across diverse agro-climatic regions due to its wide adaptability and high productivity. Wheat contributes significantly to the national food basket and serves as a primary source of carbohydrates, proteins, minerals and dietary fiber. Over the years, its production has increased substantially due to the adoption of high-yielding varieties, improved irrigation and intensive use of fertilizers. (FAO, 2022) [5] . However, continuous and imbalanced application of chemical fertilizers has led to deterioration of soil health, decline in organic matter and reduced nutrient use efficiency. These challenges highlight the need for sustainable nutrient management practices. Integrated nutrient management (INM), which combines inorganic fertilizers with organic inputs, has emerged as an effective approach to maintain soil fertility and enhance crop productivity. (Nardi et al., 2016; Canellas et al., 2015) [10,2] . Among the various organic inputs, humic substances especially humic acid have attracted considerable interest due to their positive influence on soil properties and plant growth. As an essential component of soil organic matter, humic acid contributes to improved soil aggregation, enhances moisture retention and promotes beneficial microbial activity, thereby supporting overall soil fertility (Canellas and Olivares, 2014) [1] . In addition, it plays a crucial role in increasing nutrient availability by forming complexes with essential elements, which helps in minimizing nutrient losses and improving their uptake by plants. Considering these advantages, the integration of humic acid with conventional fertilization practices offers a promising strategy for achieving higher productivity and maintaining soil sustainability in wheat cultivation.

Materials and Methods

A field experiment was conducted during the rabi seasons of 2023-24 and 2024-25 at the Pulse Research Station, Anand Agricultural University, Vadodara, Gujarat, India, representing the middle Gujarat agro-climatic zone with a semi-arid climate. The experimental soil was loamy sand (Goradu), slightly alkaline in reaction with low electrical conductivity. It was low in organic carbon and available nitrogen and medium in available phosphorus, potassium and micronutrients. The experiment was laid out in a randomized block design with ten treatments and three replications. The treatments consisted of different levels of recommended dose of fertilizers (RDF: 120-60-40 kg N-P 2 O 5 -K 2 O ha -1 ) combined with soil and foliar application of humic acid: T 1: Absolute Control, T 2: 100% RDF, T 3: 100% RDF + Soil application of humic acid @ 5 kg/ha, T 4: 100% RDF + Soil application of humic acid @ 10 kg/ha, T 5: 75% RDF + Soil application of humic acid @ 5 kg/ha, T 6: 75% RDF + Soil application of humic acid @ 10 kg/ha, T 7: 75% RDF + Soil application of humic acid @ 15 kg/ha, T 8: T 5 + Foliar application of humic acid @ 0.2% (30 & 45 DAS), T 9: T 6 + Foliar application of humic acid @ 0.2% (30 & 45 DAS), T 10: T 7 + Foliar application of humic acid @ 0.2% (30 & 45 DAS). The experimental crop was wheat (Triticum aestivum L.) and the variety GW 451, which is well adapted to the region. Sowing was carried out by the line sowing method, maintaining a row spacing of 22.5 cm to ensure optimum plant population and efficient resource utilization. The crop was grown under recommended agronomic practices. Nitrogen was applied in split doses, while phosphorus and potassium were applied as basal. Observations on growth parameters, yield attributes, grain yield, straw yield and quality parameters were recorded using standard analytical procedures.

Results and Discussion

Plant population

Plant population per meter row length recorded at 15 DAS did not show any statistically significant variation among treatments during both experimental years as well as in pooled analysis. This indicates that humic acid application had no noticeable influence on germination or initial plant establishment.

Plant height

Plant height at 30 DAS remained unaffected by different treatments during individual years; however, pooled data indicated a slight improvement under higher levels of humic acid application. At harvest, a clear treatment effect was observed, wherein application of 100% RDF + humic acid @ 10 kg ha -1 recorded the significantly highest plant height (33.51 cm). At harvest, T 4 recorded the tallest plants during both 2023-24 (82.80 cm) and 2024-25 (83.07 cm), remaining significantly superior to the control (T 1 ), while T 3 (100% RDF + humic acid @ 5 kg ha -1 ) remained statistically at par with T 4 in both years and pooled analysis. The pooled data further observed that T 4 recorded the significantly highest plant height (82.94 cm). The increase in plant height with humic acid application may be attributed to improved soil physical properties, enhanced nutrient availability and stimulation of root growth and physiological processes such as cell elongation and division, resulting in improved vegetative growth. Similar finding reported by Patel et al., 2018 [11] , Manjeera et al., 2021 [9] and Kumar et al., 2023 [6] .

Spike length

Spike length of wheat was significantly influenced by humic acid and fertilizer treatments during both years and in pooled analysis. The combined application of 100% RDF and humic acid @ 10 kg ha -1 (T 4 ) recorded the significantly highest spike length (8.94 and 9.10 cm during 2023-24 and 2024-25, respectively) with a pooled mean of 9.02 cm, and was significantly superior to T 1 , T 2 , and all 75% RDF treatments. Treatment T 3 (100% RDF + humic acid @ 5 kg ha -1 ) remained statistically at par with T 4 in both individual years and pooled analysis. The improvement in spike length may be attributed to enhanced nutrient availability, chelation of micronutrients, and improved cation exchange capacity due to humic acid, leading to better nutrient uptake. Additionally, humic substances promote root growth, membrane permeability and enzymatic activity, resulting in improved plant vigour and spike development, as also reported by Patel et al. (2018) [11] , Manjeera et al. (2021) [9] , and Kumar et al. (2023) [6] .

Number of total tillers

The significantly highest number of tillers count (329.67, 332.00 and 330.83 m -1 row length during 2023-24, 2024-25 and pooled, respectively) was observed under treatment T 4 (100% RDF + humic acid @ 10 kg ha -1 ) compare to the control, which was statistically comparable with the treatment receiving 100% RDF with soil application of humic acid @ 5 kg ha -1 in both years and pooled analysis. The increase in tiller number may be attributed to improved nutrient availability, enhanced root growth and better translocation of assimilates, along with stimulation of hormonal activity (auxin-like effects), leading to enhanced tillering (Nardi et al., 2016 and Canellas et al., 2015) [10, 2] . These findings are consistent with the research of Kumar et al. (2023) [6] , Porchelvan et al. (2024) [12] and Chaubey et al.

Protein content

Grain protein content of wheat exhibited a significant response to different treatments. The application of 100% RDF and humic acid @ 10 kg ha -1 resulted the highest protein content (14.60, 14.92 and 14.76% during 2023-24, 2024-25 and pooled, respectively), followed by T 3 . Treatments involving soil and foliar application of humic acid showed intermediate protein content, with foliar application exerting a slight additive effect. The increase in protein content may be attributed to improved nitrogen availability, enhanced uptake and assimilation, better translocation of photosynthates and stimulation of protein synthesis. Similar findings were reported by Chaitra et al. (2024) [3] , Labade et al. (2024) [7] and Mane et al. (2024) [8] .

Yield of wheat

Both grain and straw yields were markedly influenced by the application of humic acid in conjunction with fertilizers (Table 4). The treatment receiving 100% RDF along with humic acid @ 10 kg ha -1 produced the significantly highest grain yield (5200, 5283 and 5242 kg ha -1 during 2023-24, 2024-25 and pooled, respectively) and was superior to all other treatments, though it remained statistically at par with T 3 . The lowest grain yield was recorded under control (T 1 ). The increase in yield may be attributed to improved soil properties, enhanced nutrient availability and use efficiency, better growth and tillering and increased photosynthetic activity leading to greater assimilate translocation to grains. Similar findings were reported by Sharma et al. (2023) [14] , Vinod et al. (2024) [16] , Labade et al.

(2024) [7] and Chaubey et al. (2025) [4] . Similarly, straw yield followed a trend comparable to grain yield (Table 4). The significantly highest straw yield (6120, 6153 and 6137 kg ha -1 during 2023-24, 2024-25 and pooled, respectively was found in application of 100% RDF + humic acid @ 10 kg ha -1 , followed by T 3 . The increase in straw yield may be attributed to improved soil fertility, enhanced nutrient availability and uptake and better plant growth attributes such as plant height, tiller number and dry matter accumulation. Similar findings were reported by Sharma et al. (2023) [14] , Vinod et al.

(2024) [16] and Chaubey et al. (2025) [4] .

Chlorophyll content

Humic acid treatments significantly effect in chlorophyll content at 30 and 45 DAS during both years and in pooled analysis (Table 5). At 30 DAS, chlorophyll content was not significantly affected during individual years; however, T 4 (100% RDF + humic acid @ 10 kg ha -1 ) noted comparatively higher chlorophyll content (32.80 SPAD) in pooled analysis and remained at par with T 3 , T 8 , T 9 and T 10 . At 45 DAS, chlorophyll content was significantly influenced by treatments, with T 4 recording the significantly highest values (34.83, 35.08 and 34.95 SPAD during 2023-24, 2024-25 and pooled, respectively), while control (T 1 ) recorded the lowest (28.85 SPAD). The increase in chlorophyll content may be attributed to improved nitrogen availability, enhanced enzymatic activity and stimulation of chlorophyll biosynthesis due to humic acid application, as also reported by Thakur et al. (2018) [15] , Rajamani et al. (2021) [13] and Chaitra et al. (2024) [3] .

Conclusion

The results of the study concluded that integration of humic acid with the recommended dose of fertilizers significantly enhances growth, yield and grain quality of wheat. The combination of 100% RDF along with humic acid @ 10 kg ha -1 underscores its potential to enhance nutrient use efficiency and optimize crop productivity, indicating that such integration is a viable strategy for improving productivity and sustaining soil health.

Acknowledgement

AcknowledgementsThe authors acknowledge Anand Agricultural University for providing necessary facilities and support for conducting the experiment.

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