Last revised January 14, 2010
Carrots originated in south Asia, in what is now Afghanistan, Iran, and Pakistan. By 900 to 1000 A.D. they were being grown from India to the Eastern Mediterranean. By the 1300s purple and yellow carrots had spread as far as western Europe and China. The first appearance of white and orange carrots in Europe was during the 1700s. Orange carrots soon displaced other colors and today predominate throughout the world. Nevertheless, other colors of carrots are commercially available. See the section on Nutritionally Enhanced and Unusually Pigmented carrots under Varieties, below. Carrots are an excellent source of beta-carotene (pro-vitamin A). High-pigment varieties are also an excellent source of antioxidants thought to help prevent cancer.
Carrots: Photo credit: Bill Mansour, Oregon State University
Paris market (approximately 60 days): Round to "top-shaped" roots averaging 2-3" in diameter. Grown for specialty fresh markets.
Amsterdam forcing (approximately 65 days): Roots are small to medium (ave. 5"), slender cylindrical shape, blunt tipped, small core and smooth skinned. Foliage and crown are small. Grown for bunching and as a quick maturing crop for market or cello-packing. Also used for freezing and canning especially for "baby carrot" packs where whole-root baby carrots are required. Most baby carrots are "cut and peel" (see below).
Nantes (approximately 70 days): Roots are medium in size (ave. 6"), cylindrical, generally with a slight shoulder, blunt tipped but sometimes tending to taper. Intermediate in foliage and crown size. Quality is between Amsterdam forcing and Berlicum. Because of its high sugar content and tenderness, some varieties of this type have a tendency to split under late season western Oregon conditions. Grown for cello-packing, bunching and processing.
Imperator (approximately 100 days): Very long (ave. 9-10"), tapered, slender roots, small core, excellent color, smooth skinned. Foliage is intermediate with a small crown. Grown for market, often bunched, and sometimes for processing, primarily for sliced packs.
Berlicum (approximately 100 days): Roots are large (ave. 8-9"), cylindrical or only slightly tapering, resembling a large Nantes. Grown mainly for processing.
Danvers (approximately 80 days): Roots average 7", intermediate between conical and cylindrical. Upper portion of the root is tapered toward the crown. Pointed or somewhat stumped root tip. Matures about the same time as the Chantenay group.
Chantenay (approximately 80 days): Roots are medium size (ave. 5"), conical stump -rooted. Generally good core and flesh color. Moderate skin texture. Usually shorter than Nantes but foliage size is between Berlicum and Autumn King. Used widely for canning, freezing and dehydrating. Processed where a multipurpose carrot is needed for slicing and dicing.
Autumn King (approximately 100 days): Roots are very large (ave. 10-12"), tapering, usually with broad shoulders. Core and flesh color are generally inferior. Skin texture is rough. Late ripening and heavy yielding. Foliage and crowns are large and vigorous. Strong flavored. Grown mainly for certain fresh markets.
Baby carrot: These are primarily "manufactured" (cut and peeled) from undersized carrots, or pieces of carrots intended for other packs. Because of the large demand for this product, growers are planting high density carrots for this purpose also. True whole "baby" carrots are more costly and difficult to produce, harvest and handle.
High Vitamin A: These are 2-5 times higher in beta-carotene, the precursor of vitamin A, than standard carrots.
Other "Nutritionally Enhanced or "Unusually Pigmented": High levels of xanthophyll, anthocyanin, lycopene, and other antioxidant pigments.
VARIETIES FOR FRESH MARKET
See the Vegetable Variety Selection Resources page to find varieties that have been shown to perform well in the Pacific NW.
Deep, well-drained, sandy loam and muck soils of pH 5.5 to 7.0 are desirable. A chisel plow is recommended to work these soils to a depth of 12 to 15 inches for good root penetration. Soils should be bedded to obtain optimum drainage and maximum root length and smoothness.
Use high quality, size-graded and fungicide-treated, seed for optimum uniformity and performance. Pelletized carrot seed is commonly used with precision spacing, and has been found to be useful in improving size uniformity. A number of pelletizing materials are available, differing in weight, cost and response to soil moisture. Primed seed and seed coatings are also becoming popular. Consult your seed dealer about the availability of primed seed.
First fields may be seeded as early as mid-March and the last about the first of July.
Generally 2 to 4 lb of seed are needed per acre for fresh market carrots or slicers for processing. For dicing carrots for processing, 1 to 2 lb of seed are needed. Carrot seed numbers about 370,000/lb.
Research from Chrisseed in Washington State indicates that carrots grown for the cut-and-peel market should be planted at between 1.5 and 1.75 million seeds/acre. For the cello-pack market, seeding rate should be about 1 million/acre. Foliar diseases may be aggravated at the higher plant populations, and care should be exercised in the choice of varieties when planting at these high populations to select those with appropriate disease resistance and top characteristics.
Plant populations per lineal foot of bed containing 2 scatter rows (or 4 to 6 lines), should be 12-(24) for dicing and 30-(40) for slicing and fresh-market carrots.
Ideally, raised beds 4 to 6 inches high, on 40 to 42-inch centers should be used. Two scatter rows, or two multiple-line sets of 2 or 3 lines each, are planted l2-l4 inches apart per bed (depending on bed width). Seeds are placed 1.3 to 2 inches apart. The lines of each set are spaced 1.5 to 2 inches apart. In some cases, beds 72 inches apart, with 54-inch tops are used. In such configurations, 4 double or triple-line sets are planted across the bed top. When triple line sets are used increase the distance between seeds in the center row. Wide beds can only be used in conjunction with overhead irrigation.
The use of raised beds has been reported to reduce the incidence of cavity spot, a complex disorder recently attributed to Pythium violae and possibly Pythium ultimum. Outbreaks of these fungi are favored by excessive soil moisture and temperatures of 61-72 F. Alfalfa, wheat, cauliflower, broccoli, celery, cucumber, sugarbeet and watermelon also serve as hosts and so should not precede carrot, or be in rotation with it. Long rotations (3-4 years), good water management and prompt harvest are other suggested cultural control measures.
Schematics of planting configurations described above:
two rows of triple-line sets on 2 beds on 40-inch centers
four rows of triple-line sets on a 70-inch bed
Where overhead irrigation and 40 to 42 inch beds are used, and where modified potato diggers are used for harvest, it may be better to place the line sets closer together and further from the edge of the bed. This would reduce exposure of carrots in the outside lines to sunlight as the edges of the beds erode, and reduce the necessity to cultivate between the sets. The distance between the sets would be limited only by the distance needed between planters as depicted below:
two rows of triple-line sets on 2 beds on 40-inch centers with the sets placed closer together
Seeding with a precision seeder is recommended. Vacuum seeders such as Stanhay or Gaspardo are becoming popular. The Stanhay belt planter has a special shoe that plants 3 lines l.5 in. apart with each planter unit. The seed belt is punched to drop 7 to 8 seeds per foot of line in the two outside lines and 5 to 6 seeds per foot in the middle line. The Stanhay vacuum planter also has the capability of planting 3 rows per planter unit. Each vacuum plate meters seed to three separate lines. Lines are generally 1.5 to 2 inches apart and seeds are dropped about 1.5 to 2 inches apart down the line, resulting in 4 to 6 seeds per foot of seed-line for dicers and 6 to 8 plants for slicers. When triple line sets are used increase the distance between seeds in the center row.
For non-bedded plantings use row spacings of l6 to 30 inches apart and in-row stands of 10 to 20 plants per foot for dicing, or 20 to 30 plants per foot of row for slicing carrots. Use the lower plant populations when planting single rows and the higher populations when planting scatter-rows or multiple sets of rows.
Although most "baby" carrots are manufactured from standard carrots as noted above, whole baby carrots may also be produced. To obtain a uniform size and shape of whole baby carrots, seed should be sown at high density and distributed evenly in wide bands or solid beds. The seed need not be pelleted but should be size-graded by the supplier. Pelleting would be too costly at the plant populations required.
A precision seeder is not necessary for planting this type of carrot. Adequate results have been obtained by planting with a plate seeder at the rate of 80 to 100 seeds/square foot. At these spacings as much as 20 lb seed/acre may be required. Planting multiple, staggered, scatter-rows 4 inches apart results in a "solid" stand when a 4-inch scatter shoe is used. Staggered planters capable of planting multiple lines per unit (such as Beck or Stanhay) might also be used. Thirty or more lines would be needed on a 54-inch-wide bed. Beds are generally 72 inches center-to-center.
Schematic of spacing for whole baby carrots as described above:
Lines placed 1.5-2 inches apart on
beds that are 72 inches "on center"
Research in England and at OSU has shown that fresh market carrots respond favorably to the use of floating row covers. These covers are available in widths of up to 40 feet, and lengths suitable for most fields, allowing the covering of about 1 acre per roll. Researchers in England have demonstrated that the covers can be applied immediately after seeding and should be removed at about the 7th true leaf to maximize earliness and yield without generating too much top growth. OSU researchers have demonstrated that herbicides can be applied through the row covers if necessary, and that herbicides applied prior to covering are as effective as if applied without the covers.
For the most current advice, see Nutrient Management for Sustainable Vegetable Cropping Systems in Western Oregon, available as a free download from the OSU Extension Catalog
A soil test is the most accurate guide to fertilizer requirements.
Good management practices are essential if optimum fertilizer responses are to be realized. These practices include use of recommended varieties, selection of adapted soils, weed control, disease and insect control, good seed bed preparation, proper seeding methods, and timely harvest.
Because of the influence of soil type, climatic conditions, and other cultural practices, crop responses from fertilizer may not always by accurately predicted. Soil test results, field experience, and knowledge of specific crop requirements help determine the nutrients needed and the rate of application.
Fertilizer applications for carrots should insure adequate levels of all nutrients. Optimum fertilization is intended to produce top quality and yield commensurate with maximum returns.
The following recommendations are general guidelines for Western Oregon muck soils:
Nitrogen: 50-100 (N) lb/acre
Phosphate: 100-160 (P205) lb/acre
Potash: 80-150 (K20) lb/acre
Sulfur: 30-50 (S) lb/acre
For the early crop, band half the nitrogen and all the phosphate and disc in the potash. Side dress the balance of the N after the crop is 6 to 8 inches tall. For the later plantings one may broadcast all the fertilizer before seeding.
The following are recommendations for Western Oregon mineral soils:
For carrots, fertilizer materials are usually broadcast and worked into the seed bed ahead of planting.
The suggested fertilizer applications are based on a 24-inch row spacing and 20 to 25 plants per linear foot of row.
Recommended soil sampling procedures should be followed in order to estimate fertilizer needs. The Oregon State University cooperative extension agent in your county can provide you with soil sampling instructions and soil sample bags and information sheets.
Rates of 75 to 120 lb of N/A are suggested. Broadcast N before planting or part of the N can be applied as an early season top dressing. Excess N can cause splitting.
Carrots require adequate available P for satisfactory growth. Broadcast P and work into the seed bed before planting.
|If the soil test* for P reads (ppm):||Apply this amount of of phosphate (P2O5) (lb/A):|
|0 - 20||120 - 150|
|20 - 50||90 - 120|
|50 - 75||60 - 90|
*Assumes extraction procedures similar to those used by the OSU Central Analytical Laboratory. Specific information on soil test procedures is available from the Dept. of Crop and Soil Science.
For optimum growth carrots require a good supply of available K. Broadcast K and work into the seed bed before planting.
|If the soil test* for K reads (ppm):||Apply this amount of potassium (K2O) (lb/A):|
|0 - 75||120 - 180|
|75 - 150||90 - 120|
|150 - 225||60 - 90|
*Assumes extraction procedures similar to those used by the OSU Central Analytical Laboratory. Specific information on soil test procedures is available from the Dept. of Crop and Soil Science.
Include 15-20 lb S/A in the fertilizer program for carrots. S is sometimes contained in fertilizers used to supply other nutrients such as N, P, and K, but may not be present in sufficient quantity.
Plants absorb S in the form of sulfate. Fertilizer materials supply S in the form of sulfate and elemental S. Elemental S must convert to sulfate in the soil before the S becomes available to plants. The conversion of elemental S to sulfate is usually rapid for fine ground (less than 40 mesh) material in warm moist soil.
Sulfur in the sulfate form can be applied at planting time. Some S fertilizer materials such as elemental and ammonium sulfate have an acidifying effect on soil.
The S requirements of carrots can be provided by:
1. The application of 15-20 lb S/A in the form of sulfate before planting.
2. Applying 30-40 lb S/A as fine ground (finer than 40 mesh) elemental S the preceding year.
3. Applying coarser ground elemental S at higher rates and less frequently.
To date, there have been no observed indications of yield response from applications of Mg to carrots in the Willamette Valley. Trial applications of 10 to 15 lb Mg/A are suggested with soil test values below 1 meq Mg/100g soil.
Magnesium can also be supplied in dolomite which is a liming material and reduces soil acidity to about the same degree as ground limestone. Dolomite should be mixed into the seed bed at least several weeks in advance of seeding and preferably the preceding year.
Carrots require an adequate supply of B. Apply 2 to 4 lb B/A (broadcast and disk in before planting). Do not exceed the recommended rate of application. Excess B can be toxic to carrots. Boron should be broadcast uniformly on the soil. Never place boron in a side-band close to the seed at planting.
Response of carrots to nutrients other than those discussed in this guide have not been observed in western Oregon.
At present, lime is not generally recommended for carrots, as carrots in western Oregon are commonly grown on sandy river bottom soils which usually have adequate levels of calcium and magnesium.
A lime application is suggested where the soil pH is below 5.6.
|If the SMP Buffer* test for lime reads:||Apply this amount of lime (T/A):|
|Below 5.2||4 - 5|
|5.2 - 5.6||3 - 4|
|5.5 - 5.9||2 - 3|
|5.9 - 6.2||1 - 2|
*Assumes extraction procedures similar to those used by the OSU Central Analytical Laboratory. Specific information on soil test procedures is available from the Dept. of Crop and Soil Science. The liming rate is based on 100-score lime.
Lime should be mixed into the seed bed at least several weeks before seeding and preferably the preceding year. A lime application is effective over several years.
Some soils may have a fairly high SMP buffer value (over 6.2) and a low pH (below 5.3). This condition can be caused by the application of acidifying fertilizer. In this case the low pH value is temporary and the pH of the soil will increase as the fertilizer completes its reaction with the soil. This temporary "active" acidity from fertilizer is encountered following recent applications of most nitrogen fertilizer materials. Acidifying fertilizers also have a long term acidifying effect on soil that is cumulative and leads to lower SMP buffer readings.
Sandy soils to which fertilizers have not been recently applied sometimes record low pH and high SMP buffer values. In such cases, a light application of lime (1 to 2 tons/A) should suffice to neutralize soil acidity.
For acid soils low in Mg (less than 0.5 meq Mg/100g soil) one ton/A of dolomite lime can be used as a Mg source. Dolomite and ground lime stone have about the same ability to neutralize soil acidity.
These recommendations are based on experiments conducted by Horticulture and Crop and Soil Science departments researchers of the OSU Agricultural Experiment Station and Extension Service as quoted form the OSU Fertilizer Guide FG 29.
Carrots grown in western Oregon may require 14 to 16 inches of water depending on seasonal variation, variety, and length of season.
Soil type does not affect the amount of total water needed, but does dictate frequency of water application. Lighter soils need more frequent water applications, but less water applied per application.
Carrot Water Use:
The following crop water use and irrigation management information is from the OSU Carrot Irrigation Guide developed by M. Hess, J. Smesrud, and John Selker (Dept. of Bioresource Engineering) and N.S. Mansour:
Total Seasonal Evapotranspiration (inches)
|Peak Evapotranspiration Rate (inches/day)||0.20|
|Maximum Allowable Depletion (percent)||50|
|Critical Moisture Deficit Period:||seedling emergence, root expansion|
Moisture management in carrots is especially important during stand establishment and during root expansion. Since small carrot seeds are unable to emerge when surface crusting occurs and can be burnt off if surface temperatures are too high, irrigation during the pre-emergence period revolves around maintaining a moist, cool, loose soil surface. This often requires frequent, light irrigation. Conversely, deep, excessive irrigation during this period promotes problems with damping off of emerging seedlings. In the remainder of the season, available soil moisture should be depleted by no more than 50 percent1. However, maintenance of excessively moist soil may cause anaerobic soil conditions that can kill the root growing point resulting in misshapen carrots at harvest. As carrot roots develop most of their size in the last half of their growth period, irrigation is especially critical during this time. Water deficit during this period will have the greatest negative impact on yields. A balance must be struck however, between maintaining adequate moisture while minimizing wetness in the canopy which promotes the common fungal diseases alternaria and cercospora. During the last half of the growing period, irrigate only early in the day to allow for rapid canopy drying whenever possible. Soils should also be allowed to dry to 50 percent of available soil moisture during harvest to prevent excessive cracking and damage to roots during harvest.
The peak water use for carrots is approximately 0.20 and 0.17 inches per day for April and May plantings respectively. On most soils, weekly irrigation during the peak is adequate, however with sandy and sandy loam soils, irrigation may be required as frequently as every three to four days.
1. Sanders, D.C. 1993. Vegetable Crop Irrigation, Leaflet No: 33-E (North Carolina State University, Raleigh).
HARVESTING AND HANDLING
The University of California-Davis has a file on Minimal Processing of Fresh Vegetables that discusses film wrapping and other topics.
Early fresh market carrots are harvested from early July to September. Late market carrots are harvested into December, and, weather permitting, as late as the end of February. The prime harvest season for fresh market carrots in western Oregon is from the first of August to the end of November. Market carrots must be over 5 inches long and between 0.75 and 1.5 inches in diameter. Carrots harvested and handled in hot weather are more likely to decay, and care should be exercised in handling to prevent wilting.
Average yields of fresh market and processing carrots combined were reported to be about 500 cwt/acre for 1990, through 1992 in the Pacific Northwest where most of the acreage is for processing. For the same period, California carrot yields (which are mostly for fresh market) averaged about 300 cwt/acre.
Processing carrots may be harvested from the first of August to the end of November. The prime harvest period is from the end of August to October 25. For late harvest, carrot fields are limited to well-drained river bottom soils, even so, harvest schedules are often disrupted by the weather. This is the main reason considerable acreage of late carrots has shifted to the lower Columbia Basin sandy soil areas.
Generally, custom-built, coulter pick-up, or modified potato harvesters, rather than the belt pick-up Scott-Viner harvesters are used in the harvest of carrots for processing. Scott-Viner types are generally used in harvesting carrots for fresh market or where tops are expected to be suitable. Although carrots can be harvested several ways, single or multiple-row harvesters can be custom built.
Carrots for processing are processed immediately after harvest, and not stored. Most are scalped (tops removed) just before digging. A reduction in yield of about 15-20% occurs when carrots are field scalped. Scalped carrots, and those with inadequate, or frozen tops are harvested with a coulter pick-up or a modified potato harvester. Carrots with intact tops are harvested with a belt pick-up harvester that lifts carrots by their foliage and allows tops to be removed in the same operation.
Fresh market carrots are washed, sorted, and packed in one or two-pound plastic bags packaged 48 1-lb bags, or 24 2-lb bags per carton; or loose in 50-pound mesh or plastic sacks at a packing house.
STORAGE (Quoted or modified from USDA Ag. Handbook 66 and other sources)
Research in Michigan evaluating carrots that have been crowned or not, washed or not and stored in a plastic lined bin or unlined bin found that carrots stored best when untopped, unwashed and stored in plastic lined bins. Ideal storage is at 32 F and 99 % relative humidity. Carrots stored in unlined bins can lose 6% to 10% of their weight. Topping carrots and washing them also increased losses from decay. The worst treatment was topping, washing and storing carrots in unlined bins.
Carrots for processing are not normally stored. When storing, store carrots at 32 F and relative humidity of 98 to 100 %. Carrots for processing may be given a pre-storage dip treatment in a 0.1 % solution of sodium o-phenylphenate (SOPP) to effectively reduce storage decay. The solution is not rinsed off after treatment.
Mature carrots are well adapted for storage and are stored in large quantities during the fall and winter for both the fresh market and processing. Careful handling during and after harvest to avoid bruising, cutting and breakage will help ensure successful storage.
Mature topped carrots can be stored 7 to 9 months at 32 to 34 F with a very high relative humidity, 98 to 100 %. However, even under these optimum conditions 10 to 20 % of the carrots may show some decay after 7 months. Under commonly found commercial conditions (32 to 40 F) with 90 to 95 % relative humidity, 5 to 6 months storage is a more realistic expectation. Prompt cooling to 40 F or below after harvest is essential for extended storage. Poorly precooled roots decay more rapidly.
Carrots lose moisture readily and wilting results. Humidity should be kept high. Carrots stored at 98 to 100 % relative humidity develop less decay, lose less moisture, and remain crisper than those stored at 90 to 95 % relative humidity. A temperature of 31 to 34 F is essential if decay and sprouting are to be minimized. With storage at 40 to 50 F, considerable decay and sprouting may develop within 1 to 3 months.
Pre-storage washing of carrots may be desirable if they are harvested under wet conditions. Many potential decay-causing organisms are removed by washing. Also, clean, washed carrots allow freer air circulation. Air circulation between crates of pallet boxes in which carrots are stored is desirable to remove respiratory heat, maintain uniform temperatures, and help prevent condensation. An air velocity of about 14 to 20 ft/min is adequate at low storage temperatures.
Bitterness in carrots, which may develop in storage, is due to abnormal metabolism caused by ethylene. This gas is given off by apples, pears, and certain other fruits and vegetables and from decaying tissues. Bitterness can be prevented by storing carrots away from such products. Also, development of bitterness can largely be avoided by low-temperature storage, as it minimizes ethylene production. Some surface browning or oxidative discoloration often develops in stored carrots.
The highest freezing point for carrots is 29.5 F. Severe injury in carrots immediately after freezing is identified by lengthwise cracking and by blistering caused by the formation of ice crystals immediately beneath the surface. After thawing, a darkened and water-soaked skin is observed, and the carrots are soft and flabby. Use of controlled atmospheres to extend storage of carrots has not been promising. Atmospheres containing 5 to 10 % carbon dioxide with reduced oxygen concentrations of 2.5 to 6 % caused a marked increase in mold growth and rotting over that of carrots stored in air.
The most important decays of carrots in storage are gray mold rot (Botrytis), watery soft rot (Sclerotinia), crater rot (Rhizoctonia), fusarium rot, rhizopus soft rot, bacterial soft rot, black rot (Stemphylium), and sour rot (Geotrichum). Spoilage losses will be minimized if the following precautions are observed: Use new or disinfected storage containers, handle carefully to prevent injuries, pre-cool carrots, maintain them at a temperature near 32 F and avoid temperature fluctuations.