High humidity contributes to the development of diseases. Cultivation Castor is propagated entirely by seed treated to resist disease. Castor exhausts the soil quickly. Leaves, stalks and seed hulls are disked into the field following harvest. 2 O 5 is recommended.
Furrow irrigation is preferred, but subirrigation reduces weed problems.
In the United States 1,500 to 2,000 cu m of water per hectare is applied during the growing season. In Brazil 2,400 cu m of water is applied during the 3 months between flowering and harvest, with about 400 cu m being applied at each irrigation at 15 day intervals. Seed may be planted by hand or with a corn planter with special plates, after the soil has become warm and out of danger of frost. For seed increase, castor should be planted on fallow land, and should not follow small grains or another castor crop. In tropics, harvest is from wild or native plants.