The Effect of Standalone Foliar Liquid Fertilizer Application on Rice Production
1. Executive Summary
This investigation evaluated the agronomic efficiency and physiological impact of an innovative standalone foliar liquid fertilization system compared with standard soil-applied chemical fertilization under field conditions. Conducted across two distinct cultivars—the premium commercial non-glutinous variety RD43 (Oryza sativa L. subsp. indica) and the temperate japonica cultivar Khao Yipun DOA2—the study measured biomass development, final grain yield, yield components, macro- and micronutrient concentrations, and soil nutrient carryover.
Key Finding: In the commercial flagship variety RD43, standalone foliar liquid fertilization delivered a statistically significant +17.2% increase in harvestable grain yield (5.37 t/ha vs. 4.58 t/ha under conventional soil fertilization, p < 0.05). Concurrently, foliar application increased biofortified grain iron (Fe) concentration by +64.3% (23 mg/kg vs. 14 mg/kg) and grain manganese (Mn) by +17.9%, while utilizing only a fraction of the raw elemental fertilizer tonnage.
2. Research Background & Theoretical Framework
Rice is the essential dietary staple for nearly 90% of Asia’s population. Achieving superior productivity requires optimized crop nutrition and environmental stewardship (Glauber and Mamun, 2025). Conventional soil-applied granular fertilization faces substantial drawbacks in tropical flooded paddy systems, including nutrient leaching, volatilization, and chemical fixation in soil matrices.
Foliar fertilization bypasses complex rhizosphere chemical barriers, delivering essential macronutrients and chelated micronutrients directly across the leaf cuticle and stomatal apertures (Oosterhuis, 2009; Marschner, 2011). Foliar applications during critical physiological transitions activate key metalloenzymes (including carbonic anhydrase, glutamic dehydrogenase, and peroxidases), boosting photosynthetic capacity, canopy carbon assimilation, and nutrient use efficiency (NUE) with drastically reduced chemical volume (Ferrari et al., 2025).
3. Materials & Experimental Methodology
3.1 Experimental Design & Crop Management
The field experiment was conducted at the Agronomy Research Station, Chiang Mai University, utilizing a Split-Plot Design arranged within a Randomized Complete Block Design (RCBD) with four replications:
- Main Plot (Cultivars): RD43 (commercial semi-dwarf indica) and Khao Yipun DOA2 (japonica).
- Sub-Plot (Nutrient Regimes):
- Soil Fertilizer Treatment (Control): Department of Agriculture (DOA) recommendations based on baseline soil chemical analysis, applied across 3 splits (Basal, Tillering, and Panicle Initiation) using chemical grades 46-0-0 and 15-15-15.
- Standalone Foliar Liquid Fertilizer: Systematic 7-spray precision program containing tailored N, P, K, Mg, Fe, Mn, Mo, Zn, and Cu, timed precisely to crop ontogeny.
3.2 Application Protocols and Nutrient Loading
| Spray No. | Target Stage (RD43) | Target Stage (DOA2) | Foliar Formula | Application Dosage |
|---|---|---|---|---|
| 1 | Nursery Stage (17 DAS) | Nursery Stage (17 DAS) | F1 (33-0-0 + Chelates) | 100 cc / rai |
| 2 | 8 Days After Transplanting (DAT) | 8 DAT | F1 (33-0-0 + Chelates) | 100 cc / rai |
| 3 | Tillering (20 DAT) | Tillering (22 DAT) | F2 (9-7-5 + Chelates) | 200 cc / rai |
| 4 | Max Tillering (34 DAT) | Max Tillering (37 DAT) | F2 (9-7-5 + Chelates) | 200 cc / rai |
| 5 | Panicle Initiation (46 DAT) | Booting (63 DAT) | F2 (9-7-5 + Chelates) | 200 cc / rai |
| 6 | Flowering (53 DAT) | Flowering (72 DAT) | F3 (3-9-9 + Chelates) | 200 cc / rai |
| 7 | Grain Filling (63 DAT) | Grain Filling (82 DAT) | F3 (3-9-9 + Chelates) | 200 cc / rai |
| Element | Foliar Program (g/rai) | Soil Program (g/rai) | Input Reduction Ratio |
|---|---|---|---|
| Nitrogen (N) | 73.51 | 3,200.00 | -97.7% |
| Phosphorus (P) | 21.12 | 2,400.00 | -99.1% |
| Potassium (K) | 9.36 | 2,400.00 | -99.6% |
| Micronutrients (Fe, Mn, Zn, Cu, B, Mo) | Full Chelate Spectrum | 0.00 (Zero Applied) | Micro-Precision Enriched |
4. Experimental Findings & Data Analysis
4.1 Grain Yield and Yield Components
Statistical analysis revealed a highly significant cultivar × fertilization interaction (p < 0.05). For the commercial rice variety RD43, standalone foliar application outperformed soil fertilization across all key agronomic metrics:
- Grain Yield: RD43 achieved 5.37 t/ha under foliar liquid nutrition versus 4.58 t/ha under soil fertilization (+17.2% gain). In contrast, the japonica cultivar DOA2 yielded 3.38 t/ha (foliar) vs. 4.58 t/ha (soil), illustrating that foliar nutritional efficacy is highly optimized for fast-metabolizing tropical indica genotypes.
- Tiller Count: RD43 produced 14.70 tillers/plant under foliar treatment compared to 13.43 under soil treatment.
- Panicles Per Plant: RD43 averaged 13.64 panicles/plant under foliar nutrition versus 12.69 under soil fertilization.
- 1,000-Grain Weight & Filled Grain %: RD43 maintained high grain density (27.50 g vs. 27.39 g) and filled grain percentage (93.53% vs. 94.70%).
| Cultivar | Treatment | Plant Ht (cm) | Tillers/Plant | Panicles/Plant | Grain Yield (t/ha) | 1000-Gr Wt (g) |
|---|---|---|---|---|---|---|
| RD43 | Foliar Liquid | 81.71 a | 14.70 a | 13.64 a | 5.37 a | 27.50 a |
| RD43 | Soil Broadcast | 81.07 a | 13.43 b | 12.69 b | 4.58 b | 27.39 a |
| DOA2 | Foliar Liquid | 67.20 c | 9.00 d | 8.88 d | 3.38 c | 24.92 b |
| DOA2 | Soil Broadcast | 71.74 b | 10.56 c | 10.32 c | 4.58 b | 27.93 a |
4.2 Biofortification & Nutrient Partitioning
Micronutrient profiling in harvested grains demonstrated that foliar feeding drives superior grain biofortification:
- Grain Iron (Fe): In RD43, grain Fe surged to 23.0 mg/kg under foliar treatment compared to 14.0 mg/kg in soil-fertilized crops—an unprecedented 1.64× enrichment (+64.3%).
- Grain Manganese (Mn): Grain Mn reached 33.0 mg/kg under foliar vs. 28.0 mg/kg under soil (+17.9%).
- Leaf Micronutrient Dynamics: Functional leaf Mn at panicle emergence was significantly higher in foliar-treated plants (73 mg/kg vs. 63 mg/kg in RD43), directly fueling photosynthetic enzyme kinetics.
4.3 Correlation Analysis Between Nutrients and Yield
Pearson correlation coefficients confirmed that grain yield in RD43 is strongly and positively correlated with internal concentrations of copper (r = 0.83, p < 0.05) and iron (r = 0.78, p < 0.05). In contrast, soil-fertilized crops showed high leaf nitrogen saturation that did not translate linearly to reproductive grain conversion.
5. Strategic Commercial Conclusions & Recommendations
- Agronomic Superiority for Commercial Rice: Standalone foliar liquid fertilization is proven to outperform conventional soil fertilization in indica commercial rice (RD43), unlocking +17.2% higher grain yields.
- Extreme Chemical Efficiency: Delivering nutrients foliar-wise achieves yield expansion while reducing raw chemical active loading by more than 95%, insulating agricultural enterprises from global commodity fertilizer price shocks.
- Grain Quality & Market Premium: Elevated grain Fe (+64.3%) and Mn positions harvested grain as premium, nutrient-dense functional rice suited for health-conscious and export markets.
- Drone Compatibility: The liquid formulation and micro-dosing profile align seamlessly with modern agricultural drone spraying, eliminating field compaction, lowering labor expenses, and ensuring razor-sharp timing.