Year Nitrogen
2000 63.18
2001 61.04
2002 59.59
2003 64.98
2004 54.28
2005 54.82
2006 57.38
2007 57.98
2008 52.87
2009 47.21
2010 50.65
2011 50.86
2012 52.01
2013 51.4
2014 48.4
2015 52.43