Technical ArticlePhosphorus Fractions of Red Soils in Guangdong Province of South China and Their Bioavailability for Five Crop SpeciesAo, Junhua1,2; Chen, Zhijian1; Wu, Man1; Lu, Xing1; Huang, Zhenrui2; Liao, Hong1Author Information 1State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Root Biology Center, South China Agricultural University, Guangzhou, People’s Republic of China. 2Guangzhou Sugarcane Industry Research Institute, Guangzhou, People’s Republic of China. Address for correspondence: Dr. Hong Liao, South China Agricultural University, Guangzhou 510642, China. E-mail: [email protected] Financial Disclosures/Conflicts of Interest: National Key Basic Research Special Funds of China (2011CB100301), National Natural Science Foundation of China (No. 31025022), and International Science and Technology Cooperation Projects (2012B 050600034). Received February 26, 2014. Accepted for publication November 25, 2014. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.soilsci.com). Soil Science: October/November 2014 - Volume 179 - Issue 10-11 - p 514-521 doi: 10.1097/SS.0000000000000087 Buy SDC Metrics AbstractIn Brief Red soil, the main soil type in south China, has many limitations for crop production, especially low phosphorus (P) bioavailability. Currently, little is understood concerning P fractions and their bioavailability for crops. In the present study, P fractions were analyzed from 50 red soil samples collected from regions leading agricultural production in Guangdong Province of south China. The most abundant P forms were iron-bound P (Fe-P) and organic P (Org-P), which, combined, account for 64.4% ± 1.9% of total soil P. Both Org-P and Fe-P had less bioavailability for soybean in sand culture than the other sparingly soluble P forms tested, with growth reduced by 78.0% ± 4.2% or 35.4% ± 6.7% and P content reduced by 50.2% ± 8.4% or 68.7% ± 1.8% when P was supplied as Org-P or Fe-P, respectively, compared with plants supplied with KH2PO4. Further field experiment using five crop species showed that P bioavailability in red soils is very low, as reflected by an average of 53.9% ± 2.9% loss in shoot P content for all tested crops in soils without P fertilization compared with plots amended with P fertilizer. After evaluation of root-to-shoot ratio and specific root length, along with rhizosphere P depletion and acidification, it is reasonable to speculate that different crop species have evolved various strategies to overcome P deficiency in red soils. Among the tested crops, rapeseed displayed more rhizosphere acidification and lower carbon cost for maintaining root growth and subsequently possessed a superior ability to use and activate P from red soils than the other four crops. Supplemental digital content is available in the text. Copyright © 2014 Wolters Kluwer Health, Inc. All rights reserved.