raised across Asia within a generation and is now applied at rates that produce very little extra.
Beyond a threshold, additional does not enter the plant at all.
It leaves the field in water or as gas, which is a cost to the farmer and to everybody downstream.
Farmers are not applying too much through ignorance.
is cheap relative to the loss from a poor , and the safest visible action is to add more.
Correcting that requires information about a specific field rather than advice about crops in general.
services exist in most countries and are used by a small minority.
The test costs a day and a fee; the result arrives weeks later and often in a form nobody explains.
Programmes that placed a trained adviser in the village, with a simple colour chart for leaf shade, cut use by a fifth without reducing .
The tool was not the chart but the person who came back the following week.
is the part of the problem that no season can fix.
Decades of removing every stalk for fuel or feed have left soils that hold neither water nor nutrients.
Returning to the field competes directly with a household's fuel need, which is why advice alone fails.
Where an alternative fuel was available, returned to the soil within two seasons.
Soil policy is therefore energy policy, which no ministry is organised to notice.