From the 1960s onward Punjabi farmers bought land in other Indian states, where it was a fraction of Punjab's price, and took the Green Revolution package with them.
There are Punjabi farming communities in the Terai, in Ganganagar, in the Malwa region of Madhya Pradesh, in Kutch and Gujarat, in Maharashtra, in Karnataka and in Andhra Pradesh, several thousand families in total.
The pattern is consistent: a family sells or mortgages a small holding in Punjab, buys a much larger one elsewhere, brings tubewell and tractor farming with it, and raises yields on land the local farmers were farming differently.
This has produced friction in several states over water use and over land, and in some cases legislation restricting outside purchase.
It is agricultural emigration within India, driven by the same land pressure that drives emigration abroad, and it is far less discussed.
Punjabi families have also farmed in Africa, Australia and Canada for the same reason.
Punjabi farmers bought land in Madhya Pradesh, Rajasthan, Gujarat, Maharashtra and Karnataka from the 1970s, when Punjab land prices went beyond what a second son could buy into.
They took the package with them: tubewells, tractors, the wheat and paddy cycle and the input intensity, into places where the water and the soil are different.
The Terai of Uttarakhand and Uttar Pradesh was the earliest of these settlements, from the 1950s, made out of allotments to ex-servicemen and to displaced families.