What is the ideal soil mix for carrots?
My view on the best medium for carrots is that we need to have a very light sandy or loamy medium primarily (in pots this can be a combination of fine sand 50% : 30% loamy soil/coco-soil : 20% vermi-compost). This achieves loose growth area (less splitting and stunting (because of the sand); consistent moisture availability without compaction (due to the coco-soil/loamy soil) and ample nutrition (from the vermi-compost). In case your soil is heavy in nature, it may be better to form raised ridges and plan your carrot seed in them.

Stages of growth for Carrots (Images by Hariram Pagadala Sreenath)

 What is the average time needed before harvest in pots/ground in different Indian cities?

Time to harvest for us in Goa has been about three months 95-110 days (in the winter season which is from 30 deg to 18 dec) sowing in early November and harvesting early Feb. Ideal dates to sow seeds would be Nov 1 and Nov 15.

How do carrots grow in warmer weather?
Carrot is a cool season crop and when grown at 15°C to 20°C, therefore growing them well in warm places (like Chennai) is unlikely. However, you can try sowing in November – (if your temp is similar to Goa, 30 deg to 18 deg) you can manage one crop and one succession (2 weeks apart).

Do we sow carrots directly or transplant?
Direct sowing only for carrots because the early development of the taproot is critical to good development and transplants are most likely to disturb them. Seeds can be sown in rows about 25-30 cms apart. Transplanting carrots is very tricky and not worth an effort. You can however, thin them out to one plant every 2-3 inches by the end of the first month.

Do we need to feed carrots periodically?
Not particularly, but we usually do three foliar sprays of panchagavya across three months of growing and just one top dressing of compost in month 2. Over composting of carrots can lead to more leaves than roots, which is usually not the objective. Also, it may be a good thing to rotate the carrot crops into beds that have been heavily manured for other crops leafy crops earlier, as the residual nutrition is sufficient for them.

How often should you water carrots?
For a sandy medium that I described, watering moderately once every evening is fine. They don’t need the same level of water as crops like leafy and crucifer vegetables. Watering on alternate days may also be ok, if you are being liberal with your water. However, continuous water availability is important so mulching between rows may be a good idea.

Can you save carrot seeds?
This may not be worth the effort in warmer climes, but in places with cooler weather like Bangalore and Pune (or Ooty) it may be worth trying. The quality of seed (virility) is best when it is grown in the vegetable’s ideal climatic conditions (in this case between 15-20 deg C).

Where can you buy open pollinated seeds?
We have been getting our seeds from Navadanya (north India) but this isn’t ideal since we are in the plains. The better option for places at sea level and with warmer weather would be to grow shorter variety carrots (perhaps Danvers and Pusa Kesar) – while cooler regions are better for the longer varieties (like Nantes and Kuroda).

What kinds of pests affect carrots?
No real pests that we have faced, though I guess that some soil borne ones like nematodes may be an issue in some conditions.

This is a useful resource for the basics of organic management of carrots http://agritech.tnau.ac.in/org_farm/orgfarm_carrot.html