1. A series of experiments were made to test the mineral requirement of wheat at different developmental stages. By varying the concentration of the culture solution, the behaviour of plants was carefully observed.
2. The provision of double strength of culture solution (2N) from shooting to heading stage was favourable to grain production. The total yield after this treatment was over 40% more than that of the control (normal strength all through the season). The increase was mainly clue to the increase in average number of grains per ear.
3. Though double strength of culture solution from tillering to shooting stage could increase the average number of grains par ear, it did not better in other characteristics of the treated plants as compared with the control.
4. The growth and development of the plants cultivated initially in one eighth strength of culture solution (1/8N from seedling to tillering stags) fell greatly behind the condition of other lots. The depressing effect prolonged to a very late date, and thus the final yield was reduced.
5. One fourth strength of culture solution (1/4 N) from seedling to tillering stage depressed early growth only slightly. Some time after transferring from 1/4 N to 1 N, plants behaved very much like the control.
6. It is revealed that mineral requirement of wheat at different stages of development is different. Wheat plants are in need of mineral nutrition during the tillering stage, but not so much as at the shooting stage. Although high nutritional level from shooting to heading stage is decidedly important, adequate nutrition before this stage should not be overlooked.