How to improve rice quality

Increased rates of N nutrition increased the protein content of 9 tested varieties. 

Low N = No N nutrition 
High N = N as urea was added at a rate of 200 kg ha-1 to half of the pots at flooding and again at panicle initiation

Application of N fertilizer improves protein content-related traits like the milled rice rate, head rice rate and translucency (in: Chen et al., 2012).