My name is John from India and new to this forum as well as the Bonsai world. The temperature​ here is quite hotter throughout the year. I generally buy tree saplings from nurseries and pot it in a colander or a tray till it matures. Before transferring the plants from the plastic bag to the pot, I rake out the soil from the top gently and prune any downward or upward poking roots or stubs and thoroughly wash it before planting. As these are only available in India, my soil mixture is perlite, red soil, river sand, granite chips (1:1:1:2) and NPK 19:19:19 pellets. Unfortunately, the plants completely dry out and die after 2 days. One out of 5 plants survive generally and that would be a ficus. When I checked with the local nursery, they said that I should not rake out completely to transfer the plant as this method of exposing roots will not survive, but the soil comes with the plastic bag is a general clayey garden soil which cannot be used at all. I am not sure what mistake I am doing here whether it is the 19:19:19 NPK pellets or the exposure of roots.

I have attached the dried plants for your view (out of 3, only ficus in pink tray started to bud after the dried leaves have fallen).

Kindly advise on how to overcome this issue. Any ideas or suggestions would be really helpful for an amateur like me.

I don't think the exposure of the roots is the big problem, I think it's the lak of water to the soil, if it's as hot as you say then the soil will dry up fast. You need to water your plants daily. Other than that heavy root pruning could also shock the plant esspetally in the hot heat, leaving them out in the sun after such work will further stress the plant causing it to die. If you must do heavy root pruning in the heat be sure to place them in a shaded area to recover. Also don't feed right away it could cause root burning with the high fertilizer that your using.

Thanks a lot Travi for your wonderful advice. I feel the soil as wet always and will make sure it doesn't dry out as you mentioned. This would help me take care of my issue I guess...

I agree no fertiliser. Also you must not allow it to dry out. Shade will help but watering is key. I would not remove all soil however bad but just the loose soil, and also not remove any more root than is absolutely necessary.

thanks for your valuable and quick reply I will not add fertilizer in the soil mix and give a try next time. I will also keep a close watch on watering..

Can you sift the sand you are using? This looks like very dense substrate you are creating. In my substrate, I have no particles smaller than 2-3 mm. This leaves a lot of open space in the soil for the tree to grow in.

As you are starting out, probably is it better to not be so aggressive in combing out the roots:
- Remove the foliage of your trees
- Trim the original rootball to be a little bigger than the contianer youw ould like to use.
- Remove all around the original soil up to the point where you can, without breaking a lot of roots. This could be 1/3 to 2/3 of the soil in the leftover rootball
- Plant them in the open substrate. Feritilizer is not needed at this point
- Place the containers in a shaded position without a lot of wind and keep the substrate well-watered

Next repotting you can remove more of the old soil.

Note: In the tropics you should also repot in times of reduces growth ideally. I can imagine you have a period during which plants take a rest and growth is reduced or even at a stand-still for a few months. This is the time for repotting.

Thanks leatherback for your wonderful and clear explanation on my issues. I will try to sift the sand on my next project and update the status over here.