Soil Test Crop Response & Targeted-Yield Dose

Soil Test Crop Response (STCR) is an approach that prescribes a fertiliser dose tuned to a specific TARGET yield and your actual soil-test values — not a one-size-fits-all blanket recommendation. It uses calibrated equations so the dose credits the nutrients already in your soil and supplies only what's needed to hit the target.

For each nutrient the dose follows FN = a × target − b × soil-test value, with separate a and b coefficients for N, P and K. The first term is the total nutrient the target yield needs; the second subtracts a credit for what the soil test shows is already available. The result is the fertiliser nutrient to apply per hectare.

A blanket recommendation gives every field the same kg/ha regardless of its fertility. STCR instead reads your soil test and target yield, so a rich field gets less and a poor field gets more. That precision cuts waste, balances the nutrients and lines the dose up with the yield you're actually aiming for.

A recent soil test reporting available N, P and K (commonly in kg/ha), and the target yield you want for the crop. The tool combines them through the STCR equation to give the fertiliser N, P₂O₅ and K₂O, then converts those into bags of urea, SSP and MOP per hectare.

Because it credits the nutrients the soil test already shows are present, you stop paying for and applying nutrients the crop doesn't need. On fertile fields the saving can be large; on poor fields it ensures you actually apply enough. Either way the dose is matched to the target rather than guessed.

It gives the fertiliser requirement as nutrients — N, P₂O₅ and K₂O per hectare — and converts those into straight fertilisers: urea for N, single super phosphate (SSP) for P₂O₅ and muriate of potash (MOP) for K₂O. That tells you exactly how many kilograms or bags of each to buy and apply.

STCR equations are calibrated against soil-test values expressed as available nutrient in kg/ha, so the credit term lines up correctly. If your lab reports in ppm or another unit, convert to kg/ha first (ppm × 2.24 for a standard furrow-slice) so the equation gives a sensible dose.

Yes — that's the point. Raise the target and the required nutrient rises through the a-coefficient term; lower it and the dose drops. This lets you plan fertiliser for an ambitious or a conservative yield goal and see the cost trade-off before you commit.

No — it depends on a lab soil test for the N, P and K credits. The calculator turns that test plus your target yield into a dose; it can't measure your soil for you. Use a recent, properly sampled soil report, ideally with STCR coefficients calibrated for your region and crop.

They're a calibrated prescription, but real response varies with soil type, climate, crop variety, management and the accuracy of the soil test and coefficients. Treat the dose as a strong starting point, split applications sensibly, and refine against your own yield and soil-test history over seasons.