The residues are categorized into 3 groups Table 4. Some residues have similar patterns under both aeration conditions, but others exhibit differing patterns in submerged and aerobic conditions. The quality indicators presented in Table 4 serve to calibrate the residues investigated in this research with the system proposed by Palm et al. 2001. The organic residues in our Group I fit into the highest category of Palm et al. 2001 in both aeration conditions, i.e., they can be applied directly to the soil as an immediate N source. On the other hand, some of the remaining organic residues fall into different groups i.e., II or III under submerged and aerobic conditions Table 4. They also exhibited different N transformation patterns and, hence, have to be managed as N sources differently under submerged and aerobic conditions. In submerged conditions, they showed some early low N release Figure 1, Figure 2 and, hence can be used as an immediate N source to supplement other higher release N sources. However, in aerobic conditions they did not release N during at least the 16-
week study period Figure 3, Figure 4, therefore they may have to be managed the way suggested for the lower categories of the classification of Palm et al. 2001, i.e., some can be mixed with mineral fertilizers or high-quality organic materials to delay N release while some can be composted before soil application; and some should be used as surface mulch for erosion and water control.