Punjab uses more fertiliser per hectare than almost any other Indian state, and the balance is skewed heavily toward nitrogen because urea is the most heavily subsidised.
The recommended nitrogen, phosphorus and potassium ratio is not what is applied. Potassium in particular is under-applied because it is not subsidised at the same rate, and Punjab soils are increasingly deficient in it and in zinc, iron and manganese.
Soil organic carbon in Punjab has fallen to low levels across much of the state. The residue that would restore it is burnt.
Nitrate leaching into groundwater from over-application has been measured in several districts.
The subsidy structure, which is set centrally for the whole country, determines what a Punjab farmer puts on a field, and it has been producing a known imbalance for thirty years.
Urea carries the heaviest subsidy of the three nutrients, which makes it the cheapest thing a farmer can add to a field. The imbalance in the ratio follows from that price difference rather than from ignorance.
Soil testing is available through the state and through Punjab Agricultural University and is used by a small minority. Application rates are set by habit and by what the neighbour is doing.
Micronutrient deficiency, zinc and iron in particular, has spread across the state's soils and is now corrected by spraying rather than by anything done to the soil itself.