Crop rotation and lots of organic manure are the important elements of maintaining the goodness in the soil as different crops take out and leave different nutrients. Changing the crop in the field can also reduce the number of pests likely to affect it. Therefore planning the fields and what they will be growing is carried out well in advance.
At the start of the season the ground has to be prepared to be ready for sowing the various crops. The fields are ridged up, destoned and leveled. Then they are either left level, ploughed or raised up as beds depending on the crop. For carrots the soil needs to be loose (preferably slightly sandy) to allow the carrots to grow long and straight. To assist them they are planted in raised beds which helps them to grow straight and also prevents the carrots getting waterlogged if it rains too heavily.
In spring (depending on the crop) the seeds are sown (hopefully avoiding the frosts) to suit their needs for depth and spacing. For carrots a precision sower is used to place a single seed every 22.4cm apart which is over 4 million per hectare!!
In different parts of the country the climate is slightly different and causes both the sowing and the harvesting to be spread over a number of weeks depending on the geography. As it is warmer the further south you go their crops can be planted and harvested earlier.