Effect of foliar application of micronutrients on growth and yield of groundnut

Groundnut (Arachis hypogaea L.) is one of India's most important oilseed crops, yet its yield potential is seldom realised because soil-applied micronutrients often remain unavailable in calcareous or high-pH soils. This research examined the effect of foliar sprays of zinc sulphate (0.5%), ferrous sulphate (0.5%), borax (0.2%), and their combination on growth and yield of groundnut (cv. Konkan Gaurav) at Dr. Balasaheb Sawant Konkan Agricultural University, Dapoli, Maharashtra, during Kharif 2021. A randomised block design with seven treatments and three replications was used. Two foliar applications were given at 30 and 50 days after sowing. The combined Zn+Fe+B treatment produced the tallest plants (48.3 cm), highest number of branches per plant (8.7), and greatest pod yield (2,316 kg/ha) — an increase of 27.4% over the untreated control (1,818 kg/ha). Kernel yield and shelling percentage followed the same trend. Among single-nutrient sprays, ZnSO₄ performed best, raising pod yield by 18.6%. Foliar boron improved flower retention by 14.2% relative to control. These results indicate that a combined Zn+Fe+B foliar spray at flowering and pegging stages can meaningfully boost groundnut productivity in the lateritic soils of the Konkan coast.

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Comparison of Nutrient Application MethodsClose ×

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100-K wt (g): T1: Control vs T2: ZnSO₄ vs T3: FeSO₄ vs T4: Borax vs T5: Zn+FeClose ×

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Pods/ plant and Shell %: T1: Control vs T2: ZnSO₄ vs T3: FeSO₄ vs T4: Borax vs T5: Zn+FeClose ×

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Introduction

For centuries, groundnut has served as a dual-purpose crop in tropical agricultureits kernels supplying edible oil and protein while its residues feed livestock and enrich soils through nitrogen fixation. India, the world's second-largest producer after China, harvested about 10.1 million tonnes from 5.8 million hectares in 2020-21, but average yields remain around 1,700 kg/habarely half the potential demonstrated on research stations [1] . The gap between achievable and actual yield is widest in the lateritic and coastal plains of western India, where inherently acidic, iron-rich soils paradoxically bind zinc and boron into forms unavailable to roots [2] . Soil application of micronutrients in such conditions often proves inefficient because the applied ions get fixed within hours of incorporation. Foliar feeding bypasses this problem entirely: spraying a dilute micronutrient solution onto actively growing leaves delivers the element directly to the mesophyll through cuticular and stomatal absorption [3] . Zinc is a cofactor for carbonic anhydrase, alcohol dehydrogenase, and RNA polymeraseenzymes central to carbon fixation, auxin metabolism, and protein synthesis. Iron drives chlorophyll formation and is embedded in the electron transport chain at photosystem I. Boron governs pollen tube growth, cell wall integrity, and sugar translocation from source to sink [4] . Earlier work on groundnut has mostly tested individual micronutrients or relied on soil application alone. Research combining foliar zinc, iron, and boron on a single crop is relatively uncommon, especially under Konkan coastal conditions where lateritic soils create a unique set of nutrient limitations [5] . And among the few combined-spray trials reported, most were conducted in the semi-arid Deccan, not in the high-humidity, high-rainfall Konkan belt where foliar absorption dynamics may differ due to thicker leaf cuticles and more frequent rain washing [6] . This research tested whether foliar application of ZnSO₄, FeSO₄, and boraxindividually and in combinationcould improve growth, flowering efficiency, and pod yield of groundnut under Konkan lateritic soil conditions. The trial was carried out at Dapoli, Maharashtra during Kharif 2021 [7] .

Material and Methods

Material and Methods

Field Experimental Design

The experiment was laid out in a randomised block design with seven treatments and three replications at the Agronomy Research Farm of Dr. Balasaheb Sawant Konkan Agricultural University, Dapoli, Maharashtra (17.76°N, 73.19°E; 250 m elevation) during Kharif 2021. Each plot measured 5 m × 3 m (gross area 15 m²). Treatments comprised: T 1control (water spray), T 2 -ZnSO₄ (0.5%), T 3 -FeSO₄ (0.5%), T 4borax (0.2%), T 5 -ZnSO₄ + FeSO₄, T 6 -ZnSO₄ + borax, and T 7 -ZnSO₄ + FeSO₄ + borax (combined). Randomisation was carried out using a random number table, and buffer rows of one metre separated adjacent plots to prevent spray drift contamination.

Material

Groundnut cv. Konkan Gaurav (a semi-spreading, mediumduration variety recommended for the Konkan region) was sown on 18 June 2021 at a spacing of 30 × 10 cm. Seed was treated with Rhizobium (200 g/kg seed) and Trichoderma viride (4 g/kg seed) before sowing. A basal dose of 25:50:00 kg/ha N:P₂O₅ was applied through urea and single super phosphate. FYM at 5 t/ha was incorporated two weeks before sowing [8] . Foliar sprays were applied at 30 DAS (onset of flowering) and 50 DAS (pegging stage) using a knapsack sprayer calibrated to deliver 500 L/ha. Analyticalgrade ZnSO₄•7H₂O, FeSO₄•7H₂O, and borax (Na₂B₄O₇•10H₂O) were dissolved in water at the specified concentrations, with 0.1% Tween-80 as a surfactant. Spraying was done in the late afternoon (16:00-17:00 h) to minimise evaporative loss [9] .

Methods

Observations were recorded on five randomly tagged plants per plot. Growth parametersplant height, number of branches, leaf area indexwere measured at 30, 60, and 90 DAS. Flower count was taken at peak flowering (45-50 DAS), and flower retention percentage was calculated as (pods formed / total flowers) × 100. Yield componentspods per plant, pod weight per plant, kernel yield, shelling percentage, and 100-kernel weightwere recorded at harvest. Pod yield and haulm yield were recorded on a whole-plot basis and converted to kg/ha. Data were analysed by ANOVA, and treatment means were compared using Duncan's multiple range test at p≤0.05 [10] .

Nutrient Budget

Soil samples (0-20 cm) were collected before sowing and after harvest from each plot. Available Zn (DTPAextractable), Fe (DTPA-extractable), and hot-water-soluble B were analysed to estimate the net change in available micronutrient status. The apparent recovery of foliar-applied nutrients was calculated as (nutrient uptake in treatednutrient uptake in control) / (nutrient applied via spray) × 100 [11] . The combined Zn+Fe+B treatment (T 7 ) produced the highest values across all parameters. Pod yield reached 2,316 kg/haa 27.4% increase over controland was significantly superior to all single-nutrient treatments. Among individual sprays, ZnSO₄ (T 2 ) gave the best response, raising pod yield by 18.6% over control. Two-nutrient combinations (T 5 , T 6 ) were intermediate. Shelling percentage improved from 67.2% (control) to 73.4% (T 7 ), and 100-kernel weight increased from 36.8 g to 41.7 g. Flower retention was 14.2% higher in the borax-containing treatments, pointing to boron's specific role in pollen viability and tube elongation [4,9] .

Results

Results

Comprehensive Interpretation

The additive response seen in T 7 suggests that Zn, Fe, and B act through complementary pathways -Zn boosting enzyme activity, Fe supporting chlorophyll and electron transport, and B securing reproductive successand that correcting all three deficiencies simultaneously removes a broader set of physiological bottlenecks than addressing any single nutrient alone [3,4] . The nutrient budget analysis showed apparent foliar recovery of 14.8% for Zn, 11.3% for Fe, and 9.6% for B, which are within ranges reported for foliar feeding in oilseed crops [11] .

Discussion

The 27.4% pod yield increase with combined Zn+Fe+B foliar spray aligns with reports by Chitdeshwari et al. (2011) from Tamil Nadu, who recorded a 22-30% yield gain in groundnut receiving similar combinations [12] . The stronger response compared with soil application is expected given Dapoli's lateritic soils, where high iron oxide content binds added zinc and boron into unavailable forms within days of application. Foliar delivery avoided this fixation entirely [2,5] . Zinc's contribution was the largest among single nutrients, likely because Zn deficiency impairs the activity of carbonic anhydrase, limiting CO₂ hydration at the chloroplast level and therefore constraining photosynthesis [3] . The 18.6% yield gain from ZnSO₄ alone is consistent with Cakmak's (2008) meta-analysis showing zinc as the most yieldresponsive foliar micronutrient in legumes [13] . Boron's primary value was in reproductive biology. The 14.2% improvement in flower retention matches Marschner's (1995) description of boron's role in pollen germination and tube elongationprocesses that directly determine peg formation and, consequently, pod number [14] . That borax alone increased pod yield by only 9.3% while its combination with Zn and Fe gave 27.4% suggests synergistic rather than merely additive effects, possibly because boron-mediated sugar translocation is more efficient when zinc-dependent enzyme systems and irondependent electron transport are also operating at full capacity.

The slightly lower apparent recovery of Fe (11.3%) compared with Zn (14.8%) likely reflects iron's tendency to form insoluble oxides on the leaf surface before complete absorptiona known challenge with foliar iron applications in humid climates [15] . Including a chelating agent such as Fe-EDTA in future trials could improve uptake efficiency.

Conclusion

Conclusion

Figures and tables from the paper

Treatment	Ht (cm)	Branches	Pods/ plant	Shell %	100-K wt (g)	Pod yield (kg/ha)	Kernel yield (kg/ha)
T1: Control	39.2	6.1	17.4	67.2	36.8	1818	1222
T2: ZnSO₄	44.7	7.6	21.3	70.4	39.1	2156	1518
T3: FeSO₄	42.3	7.1	19.8	69.1	38.3	2041	1411
T4: Borax	41.6	6.9	19.2	68.7	37.6	1987	1366
T5: Zn+Fe	45.1	7.9	22.1	71.8	40.2	2218	1593
T6: Zn+B	44.3	7.7	21.7	71.3	39.8	2179	1554
T7: Zn+Fe+B	48.3	8.7	24.6	73.4	41.7	2316	1700
SEm(±)	1.23	0.31	0.87	0.94	0.82	57.3	41.6
CD (P=0.05)	3.68	0.93	2.61	2.81	2.46	171.4	124.5

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Growth and yield parameters of groundnut as affected by foliar micronutrient application

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Plant height progression of groundnut under different foliar micronutrient treatments at Dapoli, Kharif 2021

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Schematic illustration of the physiological pathways through which foliar-applied Zn, Fe, and B influence groundnut growth and yield

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