四川省试验资料表明，当产量水平较低时，每生产1千克油菜只需800~1000升水。但要获得较高产量时，则要付出较多的水量，需1000~1100升。辽宁和陕西的试验资料表明，当气候趋向干燥时，每生产1千克油菜需要的水量也随之增加，约1400升。
The experimental data in Sichuan Province showed that when the yield level was low, only 800-1000 liters of water were needed for each kilogram of rape. However, in order to obtain higher yields, more water needs to be paid, which requires 1000-1100 liters. The experimental data of Liaoning and Shaanxi provinces show that when the climate tends to be dry, the water requirement per kilogram of rapeseed also increases, about 1400 liters.
油菜不同的生育阶段对土壤水分的要求也各异，一般苗期为70%左右，中期为80%~90%，后期应控制低些，一般在80%以内，以便促使籽粒成熟。经过多年研究，油菜苗期需要充足的水分，土壤干旱将严重影响根系和叶片的生长，苗后期是器官分化、奠定丰产基础的关键时期，不能缺水。蕾薹期是春油菜水分临界期，尤其在开花期水分需求迫切。
Different growth stages of rapeseed require different soil moisture. Generally, the seedling stage is about 70%, the middle stage is 80%~90%, and the later stage should be controlled less than 80% in order to promote grain maturity. After many years of research, rapeseed seedling needs sufficient water. Soil drought will seriously affect the growth of roots and leaves. Late seedling stage is the key period for organ differentiation and laying the foundation for high yield, and water shortage is not allowed. The budding and bolting stage is the critical stage of water content in spring rapeseed, especially in flowering stage.