Many factors that determine bioavailability of essential elements are expected to change after a shift to aerobic system of rice cultivation. Soil pH is an important characteristic and controls the availability of most essential plant nutrients and there by the growth and yield of rice. Flooding overcomes both acid and alkaline (sodic) conditions in soil. The pH of an acid soil changed from 3.5 to near 6.0 and that of an alkaline soil changed from 8.1 to near 7.3 on submergence for a period of 2 weeks due to the dilution of H+ or Na+ ions and reverted back to its original pH when flooding was withdrawn. In aerobic rice, as the concept of flooding the paddy fields is abandoned, bulk soil pH may either increase or decrease depending on the original soil pH. In an aerobic rice study at Philippines, the pH of soil increased from 7.0 at seeding to near 8.0 at flowering in 2007 and was reported to be responsible for micronutrient deficiency.