Nitrogen Status of Upland Soils

Abstract

Nitrogen status of upland soils were assessed for soil samples collecting from the Northern, Northeastern, and Southern parts of Thailand. Soil organic mater, total nitrogen, mineralizable N and biomass N were analyzed and compared among these oil samples. Results revealed that soil samples from the North had finer texture and contained more organic matter and total nitrogen than soil samples from the Northeast and the South. Furthermore, nitrogen mineralization and nitrification was more efficient in Northern then in Northeastern and Southern soils. Nitrogen loss due to denitrification was observed only in some incubated Southern soils. The amount of soil microbial biomass was found in correlation with the amount of soil organic matter in all soil samples. Moreover, the mineralizable N derived from the biomass N in the North was lower than that in the Northeast.