After the Battle of Buxar (1764), East India Company had got the Diwani (revenue) rights over Bihar, Bengal and Orissa. Starting then, in order to collect the revenue, various land revenue policies were introduced by the Britishers. The various policies and their impacts on Indian agriculture are as follows:

Permanent Settlement:
It was planned by John Shore but was introduced by Lord Cornwallis in Bihar, Bengal, Orissa and district of Benares in 1793. In this model, zamindars and revenue collectors became the owners of the entire land in their zamindaris, and the right of ownership was hereditary and transferrable.

Its impact on Indian Agriculture:

Cultivators were reduced to the low status of mere tenants and were deprived of long standing rights to the soil and other customary rights like use of pasture land, forest lands, irrigation canals, fisheries, homestead plots and protection against enhancement of rent, etc.
Rise of the problem of Absentee Landlordism - where new moneyed men from Calcutta with no local connections bought lands when Zamindars struggled to meet revenue obligations. The new landlords were often absentees from their lands, and generated resentment among the farmers.
Ryotwari System (or Zamindari System):
It was introduced by Read and Munro in 1820 in South and South Western India, later it was introduced in parts of Madras and Bombay presidency. In this system, cultivator was to be recognised as the owner of his plot of the land subject to the payment of land revenue. The settlement was not made permanent, it was revised periodically after 20 to 30 years, when the revenue demand was usually raised.

Its impact on Indian Agriculture:

Ryot had to pay revenue even when his produce was partially or wholly destroyed by drought or floods.
Government retained the right to enhance the land revenue at will, and claimed very high tax of 45% to 55%.
Rigid system of revenue collection forced ryots into the hands of moneylenders.
Mahalwari System:
It was introduced by Holt Mackenzie and R Merttins Bird in 1822 in Ganga valley, N-W provinces, Central India, Punjab. In this, the revenue settlement was to be made village by village or estate by estate (Mahals) with landlords or heads of families (called Lambardar) who collectively claimed to be the landlords of the village or the estate.

Its impact on Indian Agriculture:

As the revenue was revised periodically, and revenue demands increased, farmers were the sufferers even in this system.
This brought about some improvement in agriculture facilities like irrigation, but farmers benefited little from them.
The various types of British revenue settlement policies gave rise to a new form of private ownership of land, in which the benefits of innovation did not reach the cultivators. Land became a commodity which could be freely bought and sold and thus shaking up the village structure and stability. They led to impoverishment of the peasantry and hence rural indebtedness.