Castor is mostly raised under rained conditions. However, it has been observed that it responds very well to irrigation. Castor being a deep-rooted crop can extract water from considerable depth in the soil. Irrigations may thus be relatively heavy and less frequent. For higher yields, wherever, possible 2-3 heavy irrigations may be given. In case of soil moisture deficiency at flowering stage, essentially one irrigation be provided. In heavy rainfall areas, proper drainage is most essential.

Under irrigated conditions, 3-4 irrigations at an interval of 15 to 20 days should be given after cessation of monsoon

Farmers of south Saurashtra zone growing GCH-4 are advised to apply 11 irrigations to their crop. After cessation of monsoon, three irrigations should be given at 20 days interval and remaining 8 irrigations at 15 days interval. Mulching with straw mulch @ 5 t/ha can result in 10 % more income, though black plastic mulch (BPM) can increase the yields by 22 %, it is economically not viable at present.

For castor seed production in north Gujarat, 14 irrigations each of 60 mm depth to female line are recommended. The interval between two irrigations should be 10 days during October and November and 15 days during December and February. The female line should be fertilized with 125kg N/ha.