Preparing to plant carrots: seeds and soil

Carrots have a very deep root system and a mass of fine feeder roots.

Preparing to plant carrots: seeds and soil
With soil in poor condition, fine clods like those on the right can be beneficial and reduce crusting after heavy rain.
Photo: Bill Kerr
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I have found carrot roots 2m down, and they can extend even deeper under the right conditions.

This root system enables the plant to source nutrients that are out of reach of most other vegetable crops. But the nutrients have to be there in the first place!

Lands that have been well fertilised for other vegetables usually contain enough nutrients for the carrot roots to scavenge.

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If this is not the case in your land, you’ll need to fertilise according to the results of a soil analysis.

Carrots are well adapted to a wide range of soils. Many farmers think that carrots cannot be planted in clay. This is not necessarily true; it depends on the type of clay soil.

A clay soil that becomes crumbly when drying out is suitable. Harvesting and washing the crop may provide some challenges, but the plants will still be productive.

This said, the ideal soil for carrots is a sandy loam. It is commonly believed that deep land preparation is necessary, but this depends on the condition of the soil.

Deep ripping may be needed if there is a plough pan or other hard layer for the roots to penetrate. Check for this with a soil probe or auger, or dig a profile pit.

Fine tilth: yes or no?
Carrot seed is very fine (it can number more than a million per kilogram), and therefore usually requires shallow planting and a fine seedbed. But this depends on the condition of the soil.

In certain soils, producing a very fine tilth may lead to crusting after a storm.

You will then need to counter this by planting the seeds very shallow to make it easier for the seedlings to break through.

This, in turn, will require frequent, light irrigation to keep the emerging roots moist. The combination of crusting soil and frequent irrigation creates the ideal environment for damping off pathogens, which can weaken seeds.

In hot conditions, such as those experienced recently, it can be a nightmare to provide the best conditions for germination.

If the soil is in good condition, with a healthy organic content, the risk of disease and crusting is far lower.

You can also plant slightly deeper during a heatwave to get the seed down into a cooler environment.

Granules are better
It is often better, especially in hot conditions, if the seedbed has fine granules or clods.

These help prevent crusting, create a larger surface area for evaporative cooling with the frequent light irrigations, and ensure better germination.

Most importantly, you need to ensure that the seed is planted deep enough and completely covered.

Keep in mind that only the top few centimetres of soil influence the germination environment.

Trying to obtain a good seedbed by preparing a fine soil deep down only contributes to breaking down the soil structure.

It pays to go to great pains to provide the best possible germination environment. Seed is expensive and a lower plant population will reduce your profits.

Bill Kerr is a vegetable specialist and a breeder of a range of vegetables.