Quote

"Organically grown" food is food grown and processed using no synthetic fertilizers or pesticides. Pesticides derived from natural sources (e.g., biological pesticides) may also be used in producing organically grown food. Increasingly, some consumers are purchasing organically grown and processed foods as a way to reduce their exposure to synthetic pesticides and fertilizers. Many supermarkets now stock organic products for their consumers. Ask your grocer about organic food and its availability at your store. - EPA

Quote
http://www.carrotmuseum.co.uk/cultivation.html
Carrots can taste soapy or bitter - Two ingredients determine a carrot's flavour: sugars and terpenoids (volatile compounds that impart the carrot flavour). Some varieties are naturally high in terpenoids, which make the carrots taste bitter or soapy. Because terpenoids develop earlier than sugars, a carrot that is harvested too young might taste bitter.

The taste in carrots is based on the right balance of sugars and terpenoids. Terpenoids produce a soapy turpentine-like taste that will mask sweetness. Differences in flavour components have been found to be attributable more to genetics than to climatic conditions; however, the controversy continues. Volatiles can also increase during cold storage (around -1C) which is a common practice (even for organics!)

Many different terpenes in carrot can cause a turpentine-like taste. Usually terpenes give a desirable taste to carrots, but in high concentrations can give undesirable taste. Factors influencing undesirable taste include genetics, growing conditions, diseases and insects, post-harvest handling and storage atmosphere.

Storing carrots near apples or other fruits that manufacture ethylene gas as they ripen, encourages the development of terpenoids in the vegetable and causing them to become bitter when exposed to ethylene.
Raw carrots will taste more soapy than cooked ones, as cooking breaks down the terpenoids allowing the sweetness to come through.
The Nantes variety produces roots which have higher sugar content, lower in terpenoids and less suitable for long-term storage.

A lot depends on the growing conditions ( if you grow your own) - the flavour is best if they mature when days are warm and sunny and nights are cool and still. The plant is photosynthesizing like crazy in the daytime and putting a lot of sugars down into the root, then a cool night comes and the carrot 'rests' instead of burning up that sugar. Where the night time temps stay in the 60s or warmer, the plants respire more at night and use up the accumulated sugars. So for the sweetest roots, time your carrot crop to mature at a time of year with warm days and chilly nights. and no matter what the conditions, harvest late in the day rather than in the early morning.

One old wives tale I have heard, but not proven - take 2 pounds of carrots and boil them with three whole cloves and a bit of salt, is supposed to make them sweeter. (if you try this do tell me what you observe).