You must choose a sbstrat that keeps the maximum moisture

Hi Chetan

See this reference1

https://hortamericas.blogspot.com/2015/07/buffering-coir-not-necessary-if-its.html

2

https://www.growthtechnology.com/growtorial/soil-and-coco/

3

https://forums.strainhunters.com/topic/2170-1st-steps-for-growing-in-coco/

4

https://www.globalcoirs.com/hydroponics.html

5

https://www.growweedeasy.com/coco-coir

Hey Chetan

Rice is very delicate. You need a loam based soil mixed with peat and grit sand.

Mara

Cocopeat is fine grains or powders of coconut fiber, whatever the term used to call it is not a problem. which is the subject of the benefits of coconut husk is very large for agriculture. The nutrient content owned coconut husk either macro or micro-turns are needed by plants. The content of macro and micro nutrients contained in coconut fiber, among others (K) Potassium (P) phosphorus (Ca) Calcium, (Mg) Magnesium, (Na) Sodium and some other minerals. But of the many nutrient content owned cocopeat, it turns out the number of the most abundant is the element of K (potassium) which may initially inhibit root development and lead to yellowing. But this needs scientific confirmation through study.

I agree with Laith; there can be too much salt in the coco peat. In this case, you can just rinse it for a couple of hours, or you can buy pre-rinsed coco peat which is more expensive. I also think you have a nutrient deficiency in your coco peat, it in itself doesn't contain nutrients especially if it is rinsed for some time before you plant the seed. Is it draining well? Or do you have moisture accumulating?  How is your irrigation set up? Do you use a timer with four hourly intervals? Cocopeat holds moisture relatively well, but not as good as soil with organic matter. Is the cocopeat fresh or was it sterilised before use? If you use it more than once you might have a disease problem, for example, fungal spores accumulate in the substrate