The productivity of rice - 1965 - 66 - 1409 kgs per hectare.
1975 - 76 - 2372 kgs per hectare.
1985 - 86 - 2712 kgs per hectare
2014 - 15 - 4429 kgs per hectare
In the past 50 years, the productivity of paddy has increased more than three times.

1. Rain Fall
2. Water Facility
3. Weather
4. Marketing

(i) There are no perennials rivers in Tamilnadu.
(ii) Tamil Nadu receives the required water from northeast and southwest monsoon.
(iii) When the south west monsoon rains are high in the catchment areas of cauvery River in Karanataka, dams there get filled and inturn cauvery River in Tamil Nadu gets water.
(iv) Northeast monsoon is a major source of water for Tamil Nadu.
(v) The northeast monsoon rains are stored in reservoirs, lakes and tanks for cultivation.
(iv) We see that agriculture in Tamil Nadu is dependent on ground water.

(i) North east monsoon is a major source of water for Tamil Nadu.
(ii) The northeast monsoon rains are stored in reservoirs, lakes, bond and wells for cultivation.
(iii) Conventional water bodies like lakes, ponds and canals provide water for agriculture in Tamil Nadu.
(iv) 2,239 canals run through Tamil Nadu covering a length of 9,750 km.
(v) There are 7,985 small lakes, 33,142 large lakes, 15 lakh open wells and there are 3,54,000 borewells in the state where agriculture is carried out with the help of these water resources.