Sugarcane production and N fertilizer application of the top 14 sugarcane producing countries, which account for 86 and 88% of global sugarcane production area and cane yield, respectively.

a<p>FAO area and yield data 2008.</p>b<p>Heffer 2009 International Fertilizer Industry Association Assessment of fertilizer use by sugar crops at the global level 2007/2008.</p><p>*Figures for USA calculated from average application rate and area, sugarbeet production in remaining countries is minor compared to sugarcane.</p>c<p>Calculated based on a stalk dry matter content of 30% and N content of 0.2% dry weight.</p>1<p>Hartemink <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0019045#pone.0019045-Hartemink1" target="_blank">[43]</a>.</p>2<p>Dr. T.K. Srivstava, Indian Council of Agricultural Research, India (<i>pers. comm</i>. 2010).</p>3<p>Dr. Jiang Xiong Liao, Guanxi Sugarcane Research Institute, China (<i>pers. comm</i>. 2010).</p>4<p>FAO Fertilizer use by crop (2005).</p>5<p>Average application rate Wood et al <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0019045#pone.0019045-Wood1" target="_blank">[23]</a>.</p>6<p>Louisiana State University Agricultural Center, 'Fertilizer Recommendations-(2009).</p>7<p>R. Rice, Institute of Food and Agricultural Sciences, University of Florida, USA (<i>pers. comm.</i> 2010).</p>†<p>Weighted average output/input ratio.