A comparison of the isotope recovery and difference methods for determining nitrogen fertilizer efficiency text Ind Repr. from : Plant Soil, 105(1988):55-67. HARMSEN, K. NITROGEN FERTILIZERS RADIOISOTOPES 631.84 Br.631.84HARc INLIS000000000002730 Converted from MARCXML to MODS version 3.5 using MARC21slim2MODS3-5.xsl (Revision 1.106 2014/12/19)