Please check the PDF attachments.

Nice question Mahbub. We recommend to recycle rice straw in the field mainly for potassium (K). However, other nutrients also be added through rice straw incorporation. Up to 90% of K uptake by rice plant remains in straw. This K is not in complex form, as a results when it is soaked in water K comes out in solution. For this reason, rice acts as chemical K fertilizer. However, attached papers may give some message for you on rice straw and its nutrient content.

For soil health improvement, carbon return to the soil is usually a prominent management technique. Adding substances like rice straw to serve as an energy soil for the soil microbiota is often valuable for maintaining soil health.

As far I know that rice straw mainly added enough potash to the soil and in addition it is also served as a mulch material. No it doesn't replace the chemical fertilizers.

Bir Jahangir Shirazy

I attached some files with my earlier response. You can read those and can get some idea about the contribution of rice straw in rice production. If you return the whole amount of rice straw it may save about 90% to full dose of potassium. 

I agreed with Thomas that incorporation of rice straw promote the growth of soil microbes. 

I suggest you go through our reviews on rice straw management published in Advances in Agronomy

The below mentioned researcher has many articles on rice straw. Happy new year.

https://www.researchgate.net/profile/Yehia_Fahmy