I can't place nether wart in the condition shown in the picture(I tried removing all blocks in 3X3X3 area around the soulsand)

According to the debug on the first sceenshot, you're looking at netherrack, not soul sand, of which none is in view from what I can see.

That is not a Soul Sand block?

No, look at the first screenshot debug text, on the right hand side, last line. It says minecraft:netherrack

@Tan Chin Cheern
Soulsand has this sort of texture in the pack you're using: http://pixelpapercraft.com/files/1351525091116.png