Sub-problem

Crops take up well under half of the nitrogen and phosphorus applied

• National

ICAR's experimental estimates put nutrient use efficiency at 30–45 per cent for nitrogen, 15–25 per cent for phosphorus and 50–60 per cent for potassium; the rest is lost through leaching, volatilisation and runoff, or held in the soil. ICAR also reports a long-run decline in the grain response to fertiliser, attributed to nutrient imbalance, excessive nitrogen use and falling soil organic matter, with recent responses of 9.55 to 11.05 kg of grain per kg of fertiliser. Evidence confidence: Medium — ranges from field experiments, not a national measurement.