Effect of potassium humate on growth, yield and quality of transplanted rice (Oryza sativa L.)

Introduction

Rice (Oryza sativa L.), a self-pollinated short-day crop of the Poaceae family, is the world's second most important cereal after wheat and a staple food for millions, with 90% of global production concentrated in Asia. (Vasudevan et al., 2014) [1] . It grows best in humid subtropical to moist tropical climates, under submerged lowland conditions with an optimal temperature range of 21-37 °C and acidic soils (pH 4-6). Globally, Rice is the second most widely grown cereal next to wheat and it has occupied an area of 168 M ha with production and productivity of 532.66 mt and 4.7 tons ha -1 , respectively (USDA, 2021) [2] . In India, rice occupies 47.8 million ha with 145.28 million tons production, While Madhya Pradesh grows it on 2.11 million ha with lower productivity. (Agriculture statistics at a glance, 2023). Rice cultivation commonly involves transplanting in puddled, waterlogged soil, but practices vary with agroclimatic conditions. (Gupta et al., 2015) [3] . Weeds remain a major challenge in both irrigated and rainfed systems. Biostimulants, including humic substances, enhance plant growth by influencing gene expression, hormone-like activity, and nutrient uptake. (Kumar et al., 2018) [4] . Potassium is a vital nutrient for cereals, improving yield, quality, stress tolerance, and carbohydrate metabolism. (Zorb et al., 2014) [5] . Due to intensive cropping and imbalanced fertilization, potassium deficiency has increasingly become a limiting factor. Potassium humate, a potassium salt of humic acid derived from lignite, contains about 50% humic substances and 12% potassium. It is highly soluble, environmentally safe, and improves soil fertility, nutrient mobility, antioxidant defence, and microbial activity.

Humic acids act as natural chelators, reduce nutrient losses, stimulate root growth, enhance photosynthesis, and help plants tolerate abiotic stress. It enhanced the intake of water and nutrients and stimulated plant growth by increasing cell division. Additionally, HA promoted the growth and activities of the soil microbes (Chen et al., 2004) [6] . Although beneficial, its use in cereal crops remains limited due to low awareness. Overall, humic substances, especially potassium humate, have strong potential to enhance soil health, nutrient availability, and crop performance. Therefore, keeping in view all above facts the present investigation entitled "Effect of potassium humate on growth, yield and quality of transplanted rice (Oryza sativa L.)'' has been conduct.

Methods and Materials

The field experiment was conducted during Kharif 2024-25 at the Dusty Acre Research Farm, Department of Agronomy, JNKVV, Jabalpur (M.P.), located in the Kymore Plateau and Satpura Hills agro-climatic zone. The region falls under hot subhumid eco-region number 10 with an average annual rainfall of 1350 mm, mostly from mid-June to September. All required research facilities, inputs, and laboratory support were available at the campus. The study followed a Randomized Block Design (RBD) with six treatments and four replications, using rice variety PB1. The gross plot size was 5.0×4.0 m and net plot size 4.0 × 3.6 m, with spacing of 1.5 m between replications and 1.0 m between treatments. Treatments included 100% RDF alone and in combination with varying doses of potassium humate (5, 7.5, 10, 12.5 kg/ha and 25 g/ha). Data were analyzed using ANOVA as per Gomez and Gomez (1984), and significance was tested through SEm ± and CD at 5% probability. Crop observations were recorded at key growth stages. Plant population (m ²)⁻ was measured at 20 DAT and harvest from three random rows and converted to square meter values. Plant height was recorded at 30, 60 DAT and harvest from ground level to the top growing point, and the mean was calculated. Tillers hill ¹ were counted at 30, 60, 90 DAT⁻ and harvest from selected hills. Leaf Area Index (LAI) was assessed at 30, 60 and 90 DAT using a leaf area meter as per Gardner et al. (1985) [7] . Chlorophyll index (SPAD) was measured at 30 and 60 DAT from fully expanded middle leaves to assess plant health. Effective tillers were counted from five hills, considering only grain-bearing tillers. Grain yield (kgha⁻¹) was recorded from cleaned produce and converted to hectare basis. Economic assessment was done using the benefit-cost ratio:

Effect on growth parameters

Although height differences at 30 DAT were statistically nonsignificant, the numerica increase from 41.2 cm (T 1 ) to 43.8 cm (T 6 ) suggests early stimulation of vegetative growth. This can be attributed to the root-stimulating property of humic substances, which promote cell elongation and root biomass development. By 60 DAT, significant differences emerged. Plant height increased progressively from 77.8 cm in T 1 to 86.9 cm in T 6 , with the CD (P=0.05) of 5.44 cm indicating a clear treatment effect. Potassium humate application enhances nutrient uptake (especially N, P, K, and micronutrients) through improved membrane permeability and chelation activity. This stage coincides with the rapid vegetative growth phase, where enhanced nutrient absorption directly influences internode elongation and canopy development. At Harvest tallest plants (103.7 cm) were recorded in T 6 (100% RDN + 25 kg/ha Khumate), followed by T 5 and T 4 , while the lowest height (94.9 cm) occurred in the control (T 1 ). These findings agree with earlier reports that humic acids improve plant morphological traits through. It might be due to the fact that application of potassium humate lies in their ability to enhance nutrient availability to the plant. By improving the uptake of essential nutrients stimulate vital physiological process in plants, ultimately promoting growth and produce taller plant stature. Similar results were reported by Sahu et al. (2013), Kumar et al. (2022) [8] Gajbhiye et al a and b (2024) [9] , Gangwar et al (2011) [10] and Dwivedi et al 2012 [11] , tillering Phase (60 DAT) [11] significant effect was observed where tillers/hill increased from10.02 (T 1 ) to 12.96 (T 6 ). Humic substances play a significant role in Enhancing cytokinin activity, which stimulates lateral bud growth, Improving N-use efficiency, leading to vigorous vegetative growth, Activating root branching and enzymatic activity. These physiological improvements support higher tiller production. At 90 DAT, the highest number of tillers (13.19) was found under T 6 , significantly superior to the control. Treatments T 4 and T 5 were also close contenders, reflecting the dose-responsive nature of potassium humate. Tiller formation is closely linked to root activity, and humates are known to increase root length, surface area, and number of root tips. This improved root system supports higher nutrient uptake, leading to more tiller development and ultimately higher yield potential. Kumaravel et al. (2022) [12] and Ansari et al. (2023) [13] .

Grain yield kg/ha

The experimental results clearly demonstrate that the integration of potassium humate with the recommended dose of nutrients (RDN) significantly enhances the productivity of rice.

A progressive and consistent increase in grain yield, straw yield, and harvest index was recorded with increasing levels of potassium humate applied as a soil amendment. The lowest grain yield (3679.5 kg/ha) was recorded under T 1 (100% RDN alone). A gradual increase was observed as the dose of potassium humate increased, with yields ranging from 3815.5 kg/ha in T 2 to 4296.3 kg/ha in T 6 . The highest grain yield of 4296.3 kg/ha was obtained under T 6 (100% RDN + 25 kg/ha potassium humate), showing a substantial improvement over control (Jha et [14,17,15,16] . The increase in grain yield with potassium humate may be attributed to its beneficial role in improving soil physical properties, enhancing nutrient uptake, stimulating root growth, and boosting microbial activity-all of which collectively contribute to better plant growth and productivity. potassium humate stimulate physiological activities within the plant, viz., photosynthesis, hormone regulation and enzymatic processes, which collectively contribute to increased biomass accumulation and enhanced yields. Similar findings were also reported by Gohary et al. (2010) [18] , Osman et al. (2013) [19] and Barai et al. (2022) [28] Shri et al 2014 [20] Sahu et al 2023 [21] .

Straw yield kg/ha

The minimum straw yield (5980.8 kg/ha) was recorded in the control treatment (T 1 ). Treatments receiving potassium humate showed steady increments, with yields ranging from 6027.3 to 6406.3 kg/ha. The maximum straw yield (6406.3 kg/ha) was recorded in T 6 , indicating improved vegetative growth due to enhanced nutrient availability and better soil health. Higher straw yield reflects improved biomass accumulation, often linked with increased photosynthetic activity and better assimilation of nutrients stimulated by potassium humate (Tiwarti et al 2013 and Tiwarti et al 2017, Tomar et al a and b 2023, Singh et al 2013, Pahade et al 2023) [22,23,24] .

Harvest index%

It is an indicator of the efficiency of the plant to convert its total biomass into economic yield, also showed a gradual improvement with the application of potassium humate. HI increased from 38.09% in T 1 to 40.14% in T 6 . The rise in HI suggests better partitioning of assimilates towards grain formation in humate-treated plants. The highest HI in T 6 signifies that potassium humate not only enhances biomass production but also improves crop efficiency in converting this biomass into grain yield (Sairam, et [25,26,27] .

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