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Foliar Spray Calculator.
Foliar Spray / Feed Calculator
Foliar feeding from corrective deficiency through general biostimulation. Concentration math, timing, surfactant, and what to avoid.
When foliar feeding works (and doesn't)
| Use | Effectiveness |
|---|---|
| Quick correction of immobile micronutrient deficiency (Fe, Mn, Zn, B) | ★★★★★ Top use case; far faster than soil application |
| Calcium for blossom-end rot (with sticker / surfactant) | ★★★★ Effective at fruit-set timing |
| Biostimulants (kelp, humic) for general plant health | ★★★ Marginal but documented |
| Compost tea for biology + minor nutrients | ★★ Variable; best as part of broader program |
| Major nutrients (N, P, K) — supplemental only | ★★ Limited absorption; use root feeding for bulk |
| Macronutrient base feeding | ★ Foliar can\'t carry enough; not a substitute for root feed |
Timing rules
- Early morning OR late afternoon. Stomata open; sun not strong; absorption maximized.
- NOT in midday sun. Sun + droplets = leaf burn. Especially with strong nutrient solutions.
- NOT before forecasted rain < 4 hours. Wash off = wasted material.
- NOT during high heat (above 85°F). Stress + foliar = damage risk.
- Once leaves are fully expanded. Newly-unfurling tissue can be damaged by foliar concentrates.
- Once weekly maximum for general feeding. Weekly compost tea is fine; weekly heavy nutrient spray = damage.
Surfactant / sticker guidance
| Type | Purpose | Rate |
|---|---|---|
| Sticker (e.g., Nu-Film, latex) | Helps droplets adhere; rain-resistant | ~0.5-1 oz per gal water |
| Spreader (e.g., yucca extract, silicone surfactant) | Improves leaf coverage; reduces beading | ~0.5 tsp per gal |
| Penetrant | Helps active ingredient enter leaf | ~0.25 tsp per gal |
| All-in-one (e.g., M-pede, dish soap) | Cheap option; serves all 3 functions roughly | ~0.5 tsp per gal mild dish soap (no degreaser, no antibacterial) |
Common rates
| Foliar nutrient | Rate per gallon | Notes |
|---|---|---|
| Iron (FeEDDHA chelate) | 0.5-1 g per gallon | Deficiency correction; avoid mixing with high-pH water |
| Iron (FeSO₄ — non-chelated) | 0.5-1 oz per gallon | Cheap but less stable |
| Manganese (MnSO₄) | 0.5-1 oz per gallon | Similar to Fe |
| Zinc (ZnSO₄) | 0.25-0.5 oz per gallon | For deficiency only |
| Boron (Solubor or borax) | 0.05-0.1 oz per gallon | VERY narrow toxicity margin |
| Calcium (Ca chloride or Ca nitrate) | 0.5-1 oz per gallon | For BER prevention; weekly during fruit set |
| Magnesium (Epsom salt MgSO₄) | 1 tbsp per gallon | Yellowing remedy; lasts weeks |
| Urea (N) | 0.5 oz per gallon | Quick N; biuret-free urea preferred |
| Kelp / seaweed extract | 1-2 tsp per gallon | Biostimulant; weekly application standard |
| Fish hydrolysate | 1-2 tbsp per gallon | Smelly; mild N + biology |
| Humic / fulvic acid | 1-2 tsp per gallon | Helps nutrient uptake |
| Compost tea | 1:1 to 1:5 dilution | Within 4 hours of brew completion |
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