I have failed to grow carrots last year and what I learned from the experience is that pebbles might interfere the carrots growth. According to many guidelines and blogs by veteran gardeners, carrot roots might stop the growth when they touch pebbles, small stones and soil mass and we have to get rid out of them carefully. Yes, I also should have done it.
I have to avoid the recurrence of the failure before seeding carrots so today I screened out pebbles with the about 50cm wooden-framed screen, which my wife's father gave me for free.
Screening-out was a tougher job than I thought! The soil of my plot for carrots contained water so it was so heavy that I got tired even after screening-out for 10 min. But the method was so effective that hundreds of pebbles were removed out of the soil.
You can see easily the deference between the soil after screening out and the one before.
The soil on the left divided with a green plastic pole is the soil after screening out.