Nitrogen Composition of the Plow Layers of Paddy Soils in Yamaguchi Prefecture

The nitrogen composition of the plow layers of 30 paddy fields which belong to major soil groups in Yamaguchi Prefecture was investigated. The soils, namely 8 gray lowland soils, 7 gley soils, 6 yellow soils, 6 gray upland soils, and 3 brown lowland soils, were used. The results are as follows: 1) The total nitrogen contants per 100 g soil sample ranged widly from 150 to 480 mg, being 200 to 300 mg in 19 out of 30 samples studied. 2) The amounts of the NaOH-extractable nitrogen were 85-300gm per 100 g in all soil samples and were 100-200mg in 24 from a total of 30 samples. 3) The ratios of the NaOH-extractable nitrogen to the total nitrogen were 60-70% in 19 out of 30 samples. 4) The amounts of humic acid-nitrogen were nearly aqual to those of fulvic acid-nitrogen in most soil samples used. 5) No definite tendency was found between the nitrogen composition and the soil groups.