Abstract
This study evaluated a TOC-based soil water-shaking extraction method using oven-dried subsamples to estimate available nitrogen in air-dried paddy soils in Fukui Prefecture. In this method, air-dried soils are oven-dried before extraction, and total organic carbon (TOC) extracted by shaking the oven-dried soils in water is measured with a TOC analyzer as an indicator of available nitrogen. The TOC-based method was compared with a flooded incubation–Bremner distillation procedure regarded as a conventional reference method for available nitrogen; with a 0−10 mg C/L calibration range and 20-fold dilution of extracts, the estimated available nitrogen values showed good agreement with those obtained by this reference method. These results show that the TOC-based method is a practical tool for evaluating available nitrogen in paddy soils and is applicable in small-scale testing laboratories lacking nitrogen-specific analytical instruments.
https://ror.org/01n09qc98 
