| Year | Fertilizer (US $/ha) | Yield (ton/ha) |
| 2007 | 243 | 4.69 |
| 2008 | 145 | 5.25 |
| 2009 | 99 | 5.19 |
| 2010 | 94 | 5.25 |
| 2011 | 105 | 5.44 |
| 2012 | 134 | 4.69 |
| 2013 | 88 | 5.94 |
| 2014 | 66 | 5.63 |
| 2015 | 60 | 6.06 |
| 2016 | 72 | 5.75 |
| 2017 | 72 | 7.00 |