We are using Kjeldahl for rice and rice flour. It works fine.

I think Kjeldahl much easier and cheaper but less accurate and slower than Lowry or Biuret. My friend quantified rice's protein from SDS (soft dough stage) and it was okay. I think it depends on your research goals too

Lowry method  is accurate

i think its all can determine the protein estimation but, i ever used the lowry method because very sensitive to analyze the protein compound.

Absoloutley Lowry methodology is the best. Its sensitivity to peptide bonds make it the best choice particularly when the sample size is small. however, it is somehow expensive. In 2nd place Bradford method worth to be tested. The latter is easy to follow and almost cheap. Its accuracy is also considerable.

I am extracting protein firstly from rice seeds (Ground powder) using Tris HCL nd Calcium cholride. Then I am thinking to go for Bradford Method. Is it okay? 

Kjeldahl method is the best when carefully handled. You can now subject the rice product to amino acids profile analysis. The essential amino acid index ratio can then be analysed in comparison with the egg analysis as  standard.

As others have said, I think it really depends on your research objectives. If your goal is to determine the concentration of soluble protein that can be recovered from your sample using specific extraction buffer so that you can use the value for some other analytical methods down the line, such as gel electrophoresis and ELISA, then any of the methods you mentioned earlier will work just fine. Although, you might need to be aware of certain limitations associated with each method (for instance, the composition of your extraction buffer may affect the assay).

However, for other applications such as those related to nutrition or for the purpose of nutritional fact label, you might want to consider the Kjeldahl method which measures total nitrogen. However, the Kjeldahl method will likely provide you with a value that you can easily compare with other products. 

Lowry method is best. It's  very easier method other than two and also very sensitive to analyze protein compound. 

I think Lowery method is more accurate than Bradford method. We generally use Bradford method for protein estimation but in my opinion this method is less sensitive.

Lowry method can be used for estimating total protein content.

Lowry method is more accurate

Can it be accurate to estimate protein content of seed storage protein in rice directly by using UV-VIS Nanodrop-2000 at A280?