Ask what determines the fertiliser plan on most farms and the honest answer is: last year's plan, plus whatever the dealer recommends. Soil testing — the single cheapest diagnostic in agriculture — is treated as a formality for subsidy paperwork rather than the basis of the input budget.
The consequence is systematic: over-application of urea and DAP where they are least needed, under-supply of micronutrients that actually limit yield, and soil that is progressively pushed further from balance.
What a proper soil programme looks like
Sampling is done per management block, not per village. Results are read against the planned crop's demand curve, not generic thresholds. The input plan is then built backwards from the gap — including where biological inputs can mobilise nutrients that are present but locked.
Repeated over seasons, the same tests become a trend line: organic carbon, pH drift, salinity pressure. That trend line is the farm's real health record, and it is the baseline every serious soil-restoration or carbon programme requires.
On a managed farm, no input purchase precedes the soil report. It is a small discipline, and it is usually the first one that pays for itself.