SOIL POTASSIUM SUPPLYING CAPACITY AND RELEASE OF NON EXCHANGEABLE POTASSIUM IN SHANDONG SOILS

By plant exhausting method, the K supplying capacity of different type of soils brown, cinonniom and fluvo aquic soils were compared It was clearly demonstrated that their K supplying capacity mainly depended on their basic physical and chemical properties besides their parent materiel and weathering intensity The tested soils taken from the major soil types of Shandong Province shown destinct capacity of K supplying; brown soil (Linzi)cinnamon soil (Guodian)fluvo aquic soil (Dingtao)fluvo aquic soil (Jiyang)brown soil (Juxian)brown soil (Muping) The capacity was evaluated according to the contents of both easily available and nonexchangeable potassium (NEK) in soil, total K uptake and the fraction form nonexchangeable form during the exhausting period by the crops, as well as the time required for both K forms to reach the lowest level The distinction of quantity and release velocity of NEK can largely reflect their difference of K supplying capacity The total uptake of crop, reflecting the release characteristics of NEK, varied with soil types as well Uptake from cinnamon soil (Linzi) was 2 05 times as that from the brown soil (Muping) with the lowest capacity In terms of NEK, the former was 2 41 times as high as the later Of all the tested soils, cinnamon soil showed the highest K supplying capacity, brown soil the lowest and fluvo aquic soil in between It is therefore concluded that both brown soil and sandy fluvo aquic soil area should be given priority in potash application