| Years |
Centre |
North-West |
| 2003 |
231.48 ± 13.80 a |
279.49 ± 8.93 b |
| 2004 |
222.92 ± 12.28 a |
284.34 ± 9.53 b |
| 2005 |
238.54 ± 13.45 a |
286.80 ± 11.49 b |
| 2006 |
226.04 ± 10.85 a |
281.47 ± 9.15 b |
| 2007 |
232.29 ± 10.50 a |
282.06 ± 10.56 b |
| 2008 |
228.05 ± 9.30 a |
273.16 ± 9.42 b |
| 2009 |
223.54 ± 8.73 a |
289.57 ± 8.12 b |
| 2010 |
200.28 ± 6.21 ab |
279.31 ± 8.16 b |
| 2011 |
182.66 ± 7.29 ab |
299.37 ± 16.55 b |
| 2012 |
143.11 ± 5.01 c |
352.89 ± 18.01 a |
| 2013 |
75.86 ± 3.02 d |
216.28 ± 13.28 c |
| Means followed by the same alphabetic letter of same character and for the same factor are not significantly (P> 0.05) different according to Student Newman-Keuls test. |
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