Changes in natural¹⁵N abundance in paddy soils under different, long-term soil management regimes in the Tohoku region of Japan

Abstract

Long-term temporal changes in natural 15 N abundance (δ 15 N value) in paddy soils from long-term field experiments with livestock manure and rice straw composts, and in the composts used for the experiments, were investigated. These field experiments using livestock manure and rice straw composts had been conducted since 1973 and 1968, respectively. In both experiments, control plots to which no compost had been applied were also maintained. The δ

Characteristics of the Relationship between Natural 15N Abundances in Organic Rice and Soil

“…δ 15 N values of synthetic fertilizers have been reported to be as low as atmospheric N (Shearer et al, 1973;Freyer and Ali, 1974;Black and Waring, 1977;Yoneyama, 1996;. On the other hand, the reported δ 15 N values for organic fertilizers in Japan were high, ranging from 4.2‰ to 20.8‰ (Morita et al, 1999;Tokunaga et al, 2000;Nakano et al, 2003aNakano et al, , 2003bNakano et al, , 2010Nakano and Uehara, 2005, 2006b, 2009Nishida et al, 2007;Hayashi et al, 2011).…”

Using different versions of the Rothamsted Carbon model to simulate soil carbon in long-term experimental plots subjected to paddy–upland rotation in Japan

“…These sites were originally used as paddy fields of single rice cropping for more than 100 years prior to the paddy-upland rotation experiments. Values in Table 1 were obtained from Sumida et al (2005) and Nishida et al (2007). Initial SOC contents (in t C ha À1 ) were calculated from the measured SOC concentration and bulk density of topsoil to the depth shown in Table 1.…”

“…Center for the Tohoku Region. The soils at both sites are classified as Gray Lowland soils in the Japanese soil classification system for cultivated soils in Japan, with second approximation and as Typic Fluvaquents (Nishida et al 2007) in the US Soil Taxonomy system (Soil Survey Staff 1998). These sites were originally used as paddy fields of single rice cropping for more than 100 years prior to the paddy-upland rotation experiments.…”

Areal variation in the relationship between natural15N abundances of rice (Oryza sativaL.) and soil

“…These samples were put into tin capsules and analyzed for natural 15 N abundance using an isotope-ratio mass spectrometer (IRMS) coupled with an elemental analyzer (DeltaXP, Thermo Fisher Scientific Inc., Waltham, MA, USA). Preparation of irrigation water for IRMS followed the method used in previous studies (Morita et al 2002;Nishida et al 2007); irrigation water was concentrated to approximately 500 μg N mL −1 on a hotplate and 0.2 mL of this concentrated water was transferred to a tin capsule and freezedried. The samples were then analyzed for natural 15 N abundance using the IRMS coupled with an elemental analyzer.…”