5. Conclusion
Drying of soil with sunlight reduced soil pH while tilling (and drying) tended to increase pH. Pond bottom soils containing black and glutinous organic sludge are required to be treated before the next shrimp culture crop because it accumulated the toxic materials and high numbers of shrimp pathogens (Vibrio and Pseudomonas), which are harmful to shrimp culture productivity and sustainability. A combination on the use of soil drying in sunlight and tilling with the addition of probiotics (treatment 5) was effective in significantly maintaining the soil physical characteristics (pH and organic matter) and degradation of toxic organic sludge into stabilized organic matter as well as removal of shrimp pathogenic bacteria (Vibrio and Pseudomonas). Liming would be the suitable management procedure to maintain pH in treated soils containing organic sludge.