Generally people think that there is no need of any fertiliser in natural farming. Fukuoka san talks about fertilization in his book, natural way of farming. In the chapter 'Rice and Winter Grain' under the sub-heading ' Direct Seeding, No-Tillage Barley/Rice Succession with Green Manure Cover' there is a topi called Fertilization and the book reads as follows..
"Following the rice harvest, spread 650-900 pounds of chicken manure per quarter acre either before or after returning the rice straw to the fields. An additional 200 pounds may be added in late February as a topdressing during barley heading stage.
After the barley harvoest, manure again for the rice. When high yields have been collected, spread 450-900 pounds of dried chicken manure before or after returning the barley straw to the field. Fresh manure should not be used here as this can harm the rice seedlings. A later application is generally not needed, but a small amount (200-450 pounds) of chicken manure may be added early during the heading stage, preferably the 24th day of heading. This may of course be decomposed human or animal wastes or even wood ashes".
So there is fertilization done in natural farming, but it is much less effort in just scattering in chicken manure. May be this was not considered as fertilizer, rather just a decomposing agent for straw. So whoever gets into natural farming should observe these facts very closely, before concluding that no fertiliser is required for natural farming.