Estimation of Available Phosphorus Under Phosphorus Fertilization in Paddy Fields of a Cold Region Using Several Extraction Methods: A Case Study from Yamagata, Japan

Shuhei Tsumuraya, Hisashi Nasukawa () and Ryosuke Tajima ()
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Shuhei Tsumuraya: Graduate School of Agricultural Sciences, Yamagata University, Tsuruoka 997-8555, Japan
Hisashi Nasukawa: Faculty of Agriculture, Yamagata University, Tsuruoka 997-8555, Japan
Ryosuke Tajima: Graduate School of Agricultural Science, Tohoku University, Sendai 980-8572, Japan

Agriculture, 2025, vol. 15, issue 13, 1-15

Abstract: Assessing available phosphorus (P) in paddy fields is challenging due to waterlogging-induced reducing conditions. This study tested the applicability of the Truog, Bray 2, and Mehlich 3 extraction methods in both air-dried and incubated soils, as well as the ascorbic-acid-reduced Bray 2 (AR Bray 2), which simulates reducing conditions, for evaluating rice growth under P fertilization. In addition, to investigate the chemical characteristics of the extraction methods, active Al and Fe and P sequential extractions were measured. Soil samples from four representative regions in Yamagata Prefecture were used. Pot cultivation tests using ‘Haenuki’ and ‘Tsuyahime’ cultivars were conducted with varying P fertilizer levels. Variations in P availability across soil types were influenced by levels of active Al and Fe. Sequential extractions identified NaHCO 3 -P and NaOH-P fractions as important for P availability. Bray 2 in both soils and AR Bray 2 were the most effective methods, showing a strong saturating exponential correlation with rice growth and P uptake, whereas Mehlich 3 and Truog showed weaker correlations. Bray 2 and AR Bray 2 show potential but require further evaluation for practical application due to the small number of soils. Future efforts should prioritize developing methods that account for P dynamics under reducing conditions, thereby improving P management strategies and supporting sustainable rice production.

Keywords: aluminum oxides; ascorbic-acid-reduced Bray 2; cold climate agriculture; iron oxides; paddy soil; phosphorus fractionation; reducing conditions; rice growth (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2025
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