Carrot and Parsnip

Introduction

Carrot (Daucus carota) and parsnip (Pastinaca sativa) both belong to the Apiaceae family, along with celery, fennel, dill, cilantro, and parsley. These root crops have small seeds that grow slowly and are compete poorly against early weeds. They grow best in deep, well-drained soils, ideally sandy loam or muck. Using raised beds increases the depth of tilled soil and can encourage good root shape. Some growers chisel plow or rototill before forming beds to loosen the soil and enhance root development, but care should be taken to maintain good soil structure; do not overwork soils or work them while wet. Hilling soil over the shoulders of the roots at the last cultivation can help reduce greening.

Types and Varieties

Soil Fertility

Apply lime according to soil test recommendations to maintain soil pH at 6.5–6.8. Calcium levels should be maintained at a high level (60%–85% base saturation) to avoid cavity spot. 

Suggested rates of nitrogen (N), phosphorus, and potassium are based on high yield expectations of 20–25 tons per acre for carrots. If soil type or other factors limit potential to a lower yield, reduce fertilizer application accordingly.

Less N fertilizer will be needed if legume sod was plowed down or if manure was applied (see Table 1 and Table 7). Take care not to overapply N early on, because this can lead to excessive top growth, increasing susceptibility to foliar disease, and root forking. Sidedressing with N can be important if tops become diseased, as this can help plants put on enough new growth to assist with harvesting. Using urea as a source of N for sidedressing may increase the incidence of cavity spot. If large amounts of potassium (K) are needed or if soils are prone to leaching, some of the K can be applied with the first N sidedress. Carrots and parsnips have relatively high requirements for K, but excessive applications can inhibit calcium uptake and thus increase the incidence of cavity spot. 

Plant Nutrient Recommendations According to Soil Test Results for Carrot and Parsnip

Planting

Weed control in carrot and parsnip is notoriously difficult and is the biggest likely reason for reduced yields. Using stale seedbed techniques, whether physical or chemical, prior to planting is critical for optimized production.

Carrots should be planted to a stand of 15 per row-foot, which requires 2–3 lb/A of seed (or about 1/16 oz per 100 row-feet). Parsnips should be planted to a stand at 8–10 plants per foot of row, which requires 4–5 lb/A of seed (about 0.5 oz per 100 row-feet). Scatter shoes can allot plants more room to grow, but are best used in fields with low weed pressure. Seed for these crops are often pelleted and primed, which improve handling and germination, respectively, but reduces seed longevity. Parsnip seeds should be purchased new each year because they have a short life and lose viability quickly during storage.

Sow seed 0.5"–0.75" deep. These crops are slow to germinate; an adequate and constant moisture supply is necessary during this period. Parsnips require a long growing season (110–130 days) and should be seeded as early in the spring as practical. 

Field Culture

These crops require 1"–1.5” water per week. Root length is fully determined within a month of germination, after which roots enlarge in diameter. During these times, adequate water critical. Near harvest, too much water can cause roots to split.

Harvest and Storage

Carrots can be harvested with or without tops, depending on market and quality of foliage. Parsnips are always topped. Avoid direct skin contact with parsnip leaves since the leaf sap can cause phytodermatitis (sun sensitivity on skin). Tools ranging from handheld forks to tractor-mounted undercutting bars should be used to assist with harvest. Both carrots and parsnips have improved flavor with exposure to low temperatures. Carrots can withstand 28°F while parsnips can be overwintered and harvested the following spring. When overwintered, harvest parsnips before new growth begins in the spring.

Mature roots can be stored for 4–5 months at temperatures near 32°F (do not allow to freeze). Avoid relative humidity higher than 95%, which cause condensation and dripping. Carrots that are not fully mature can be stored only 4–6 weeks. Exposure to ethylene will result in the development of bitter compounds in carrot skin; do not store carrots in the same building as apples, pears, or other ethylene-producing fruits. Wash roots only as crops are removed from storage for sale as excess moisture during storage favors rot.