It was also called zerat cultivation. It was a land settlement between the planters and ryots wherein the ryots were bound to a bond to undertake a cultivation for a particular crop. The issue of indigo crops became a major incidence in Bihar and Bengal region.
It is researched based observation that this system of contract was preferred by the English Planters of indigo. They leased the land from the zamindars and then executed the Nij or zerat cultivation with the crop producers or ryots. The nij contracts were adopted after indigo revolts. Before the indigo revolt (1858) raiyati system was practiced. The nij cultivation declined in Bengal after the indigo revolt and continued in Bihar where it had spread at a later stage.
The leases acquired by the English planters from the Big Zamindars were in form of Thika tenure ( temporary lease) or mukrari tenure (premanent lease).
(based on the quotation and references from Plantations, proletarians and peasants in colonial Asia. pp.178, Edited by E. Valentine Daniel, Henry Bernstein, Tom Brass, Routledge, London, 1992. ISBN 0-7146-3467-0.