Rice Hull analysis by R. Bryant and co-wrokers at USDA in close collaboration with UA scientists, are reported in a paper published in Genetica
The full reference:
R. Bryant, A. Proctor, M. Hawkridge, A. Jackson, K. Yeater, P. Counce, W. Yan, A. McClung and R. Fjellstrom; “Genetic variation and association mapping of silica concentration in rice hulls using a germplasm collection”, Genetica, Online First™, 8 March 2012
http://www.springerlink.com/content/q8p00117l738543l/?MUD=MP