A portable GPS receiver and a navigation software were used to investigate land application practices of manure composts. The field investigation indicated that most of the land application of manure composts were observed before April. Plowing for incorporation of manure with soil were continued from the middle of April. The results also revealed that over 60% of the farms were within 1 km from livestock farms from which manure composts were transported. Most of the farms having land application were dry field rather than paddies, Some of fields located near livestock farms frequently experience over-application of manure composts. It seems to have been difficult to complete the investigation in this study without the Gps/navigation system. The GPS/navigation system will become an essential tool in field investigations such as ecological/environmental monitoring works that require repeated observation at a number of sites.