The sodium is naturally occuring in the soil and tranferedd to the plants. Nitrogen is also in the soil, air etc. Green plant have more nitrogen than or red, yellow etc. Through photosynthisis plant abosorb the oxegen and give off carbondioxide. Nitrates are NO2 - 1 nitrogen molecule and 2 oxegen molecules. dioxide means 2 oxgen molecules. The nitrogen is absorbed from the soil giving it the 1 nitrogen molecule. NO2. I can't say why the extra carbon molecule gets bumped. I may have to research that.