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Sample Parameters
Lab Test Type
Sample Depth
cm
Bulk Density (leave blank = estimate)
g/cm³
Soil Texture (for BD estimate)
pH & CEC
pH (H₂O)
pH (KCl) (optional)
CEC (meq/100g)
Macronutrients (ppm)
N — Nitrogen
P — Phosphorus
K — Potassium
Ca — Calcium
Mg — Magnesium
S — Sulphur
Micronutrients & Cations (ppm)
Zn — Zinc
Na — Sodium
Al — Aluminium
Fe — Iron
Mn — Manganese
Cu — Copper
B — Boron
Texture & Physical Properties
Clay % (affects P & K fixation)
%
Sandy <15% · Loam 15–35% · Clay >35%
Base Saturations (%)
Ca %
Mg %
K %
Na / ESP %
Haney Biological Test
Microbial Respiration (ppm CO₂)
>50 = good · <30 = poor
WEOC — Water Extractable OC (ppm)
>250 = good food reserves
Soil C:N Ratio
<12 = fast · >14 = slow
Step 3
Historical Crop & Residue Data
Previous crop drives residue nutrient credits
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Previous Crop on Land
Previous Crop Yield
ton/ha
Historical Yield (this season's crop)
ton/ha
Historical benchmark for this crop on this field — helps inform the Target Yield above
Historical Fertilizer Cost (Phase 2 – reference)
R/ha
For future cost-comparison reporting — does not affect current calculation
Fungicide / Herbicide Apps (Phase 2 – reference)
For CPI timing features — does not affect current calculation
Step 4
Calculation Parameters
Moisture, humic acid, target method
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Moisture Condition (dryland)
Step 5 Target Method
Nitrogen — Applied with Humic Acid?
NoYes (removes N leaching penalty)
Rootsure / Phosphate Mobilizer in programme? (reduces effective P requirement by 20%)
NoYes — Rootsure / Rhizoking in programme
REF
Reference Tables — Crop Removal & Residue Factors
Verify with Tiaan before client use
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⚠ These are FSSA/PDA standard defaults. Tiaan should verify and update with his own validated figures before creating client proposals.
Crop
N
P
K
Ca
Mg
S
Zn
Residue Factor
Residue C:N
kg nutrient removed per ton of crop yield (grain/product). Residue factor = ratio of residue DM to yield. C:N drives base release rate.
— Farmer —
Enter details on the left to generate
Crop / Yield—
Soil pH / CEC—
Test type—
Bulk Density—
Lime Rec.—
Gypsum (Na remed.)—
Prepared by—
Soil Supply (kg/ha from ppm)
Nutrient
ppm
kg/ha
Step 2 — Supply vs Demand
Nut.
Demand
Residue
Supply
Deficit
Step 4 — Inefficiency Multipliers
Nut.
Trigger(s)
×
⭐ Step 5 — Final Targets (kg/ha)
Deficit × Multiplier
Nutrient
Target (kg/ha)
Note
FERTASA Benchmark — Maize Handbook 5.4.4
Independent cross-check from the official FERTASA lookup tables (N by clay% · P by soil P & clay band · K by soil K & soil type). Compare against the tool's targets above.
Nutrient
FERTASA (kg/ha)
Tool target
Difference
🧪 Step 6 — Product Plan (least-cost)
Solved from the live product list
Product
Rate (kg/ha)
N
P
K
R/ha
Greedy least-cost mix from active products with a listed analysis + price. An agronomist must confirm product choice, timing and placement before this goes to a farmer.