Please let me know if there is any data for the total protein content in rice leaf by Lowery's method and total carbohydrate content in rice grain by anthrone method.
Turns up a large number of results. NDVI is the ratio of the refection of two wavelengths of red and infrared light off the leaves of rice. Some of those papers and their Bibliographies will lead on a long journey of remote sensing Nitrogen and other properties in rice and other crops.
I believe most of the Nitrogen will be in proteins in the rice.