Mineralized N of plant residues with different C:N ratios under upland and rice paddy condition

Seven organic materials commonly used in South Korea were prepared to evaluate mineralized N in upland and rice paddy soils associated with clay loam and sandy loam soil textures at 20 degrees C, 25 degrees C and 30 degrees C under the controlled condition. Organic materials included: 1) palm meal, 2) castor meal, 3) rice hull, 4) tomato residue, 5) water melon residue, 6) potato residue, and 7) garlic residue. C:N ratio of organic materials was lowest for the castor meal (7.4:1), followed by potato residue (14.3:1), tomato residue (14.7:1), water melon residue (17.6:1), palm meal (18.2:1), garlic residue (23.1:1) and rice hull (210.8:1). Castor meal with the lowest C:N in upland soil maintained the highest mineralized N at 20 degrees C, 25 degrees C and 30 degrees C during the period from 0 to 112 days, followed by tomato residue, while the rice hull with the highest C:N ratio had the lowest mineralized N. Mineralized N in organic materials varied in the rice paddy soil. C:N ratio of the organic materials was strongly correlated to the mineralized N in the upland soil, which was not observed in rice paddy soil.