Any recommendations for success in growing carrot? for a carrot success for my next season? is clay soil not the best for it? And is it necessary to use fertilizer for vegetables? If so, what kind do I need for NPK 10-10-10 OR 20-20-20 OR anything else? I also start from seeds. Do I need to start the root system with a different approach for a strong development and lots of produce? I follow the instructions package to start the seeds and use soilless soil for the seeds till germination in the small black packs. I succeeded in my 2nd year better because I started them with grow lights for 8 -10 hrs per day. And as soon as weather permits I start the hardening. I understand now that each vegetable has its own way. Perhaps next time I will grow potatoes maybe.
Carrots are fussy. They do not like too much fertilizer, so be careful about how much manure you add to the carrot patch. And they only like very light, fine, and even soil texture. Tough clay soil, any lumps (such as manure that’s not completely broken up, or stones, or clods of earth) will cause the carrots to become deformed. They love light, sandy soil that has lots of organic matter (compost) in it, and that has been dug and sieved to a very fine consistency down to the full length of the mature carrot (about a foot). They are just too lazy to force their way through obstacles.
That said, there are varieties of carrots that are shorter, or even round, so that you don’t have to prepare the soil so deeply. Look for varieties such as Chantenay, Nantes Half Long or Danvers Half Long (all of which are about 6 inches (15 cm)); Little Fingers, which are even smaller; or for small round carrots, try Paris Market or Parmex.
As for fertilizer, if you keep your soil healthy and add good compost each year, you may not need much else. I give my vegetable beds a good feeding of fish emulsion, since I get 2 or 3 crops from them annually, and I also add a bit more compost each time I reseed or replant.
Another option would be to build a raised bed with good soil.
Here is a previous question on raised beds and proper soil requirements https://www.torontomastergardeners.ca/index.php/askagardener/raised-beds/