Carrot and Parsnip Factsheet

Factsheet 08/04 Horticultural Bradbourne House Development East Malling Council Kent ME19 6DZ Carrots and Parsnips T: 01732 848383 F: 01732 848498 E: [email protected]

Interpretation of leaf nutrient analysis results

Don Tiffin, ADAS Boxworth

Carrot and parsnip quality and marketable yield can be affected by nutrient deficiencies. If the nutritional status is below the ‘critical level’ visual symptoms will be present in the field. In the absence of visual symptoms, ‘subclinical’ deficiencies or toxicities may be present which will reduce growth and subsequently yield. The foliar application of nutrients to carrot and parsnip crops can be an effective way of tackling nutrient deficiencies diagnosed either visually or by plant analysis. Yield or quality benefits from the application of essential elements are only likely when a specific deficiency has been accurately diagnosed.

This factsheet aims to: • Assist with the diagnosis of the most common visual deficiency symptoms • Provide guidance on sampling plants so that meaningful results are obtained • Provide guidance on interpreting leaf tissue analysis results • Provide information on managing nutrient deficiencies

Visual symptoms solely on visual symptoms: • More than one nutrient may be • Severe deficiencies are rare deficient in plants causing different Visual diagnosis of nutrient disorders symptoms from those caused by can be made where specific symptoms • Crop disorders induced by non- a single nutrient. Under most of deficiency and toxicity have been nutritional factors e.g. drought, low circumstances, reliance on diagnosis accurately described and illustrated. It temperatures, herbicides, some by visual symptoms alone can is the quickest method for diagnosing pests and diseases or even air be misleading the cause of poor crop performance pollutants may result in symptoms due to mineral disorders. There are, that could be mistaken for nutrient however, several difficulties in relying disorders Nutrient deficiency 3 Relate a particular disorder to the Photographs of nutrient circumstances e.g. soil type or pH deficiencies in carrots and symptoms in carrots parsnips and parsnips 4 Knowledge of susceptibility of carrots or parsnips to that disorder Note: Not all deficiencies produce The diagnosis of a nutrient disorder clear field symptoms. Photographs in the field should follow clearly 5 Consider possibility of symptoms are helpful in providing a visual definable steps: having arisen from other causes diagnosis, but often prove slightly 1 Realisation that something is wrong such as drought, waterlogging, etc ambiguous. ‘A colour illustrated guide with the crop (as mentioned under ‘Similar to pests, diseases and disorders of Symptoms’ for each nutrient) vegetables’, a CD-ROM that contains 2 Observation of abnormalities, noting further images and information on if these are worse on older or 6 Identification of possible causes by vegetable nutrient deficiencies and younger leaves; chlorosis or reference to photographs ‘Carrot crop walkers guide’ are both interveinal yellowing; marginal available from HDC. If in doubt, back scorch around leaf edges, necrosis 7 If doubt remains, check diagnosis up with leaf analysis. of leaf tissue; pattern of distribution; by means of leaf analysis deformities such as cupping, twisting and thickening

Nitrogen (N) small roots are noticeable. Plants excessive leaching or waterlogging Deficiency symptoms: grow slowly and can appear stunted. has occurred. Foliage uniformly pale green and has frail appearance due to fineness of Occurrence: Similar symptoms: leaflets. Oldest leaves become yellow, Very common whenever insufficient N Can be caused by cold weather, drought, sometimes with red tints, and shrivel. available especially on sandy soils waterlogging and root damage e.g.free In parsnips weak spindly growth and following heavy rainfall, where living nematodes and carrot fly.

Nitrogen – mildly deficient carrot crop showing Nitrogen – Seven week old parsnip plants showing healthy (left) and deficient fine, pale foliage.

Phosphorus (P) wet soil. Rarely occurs because most Deficiency symptoms: vegetable growing soils contain good Reduced growth rate. Purpling of levels of plant available phosphate. older leaves, beginning at margin can occur. In parsnips symptoms include Similar symptoms: purple tints and spindlyness to leaves Low temperatures and drought can and petioles or leaves have a dull cause similar symptoms. Also, carrot green colour. No yellowing. fly attack – check taproots for evidence of mining - and carrot Occurrence: motley dwarf virus that causes older On acid soils, calcareous soils or peats. leaves to redden or purple but Temporary deficiencies occur on cold, younger leaves are yellow.

Phosphorus – nine week old carrot plant showing leaf purpling Potassium (K) Occurrence: Deficiency symptoms: On light sandy soils with excessive Older leaves scorch and collapse leaching if K has not been applied. beginning at margins of leaflets. More Similar symptoms: Marginal scorch advanced symptoms; entire petioles of lower leaves can be confused with acquire water-soaked appearance, chloride toxicity (see ‘Toxicities’ then dry up and collapse. In parsnips; section) and wind damage. marginal and interveinal chlorosis of older leaves leading to scorch; margins of scorched leaflets roll upwards.

Potassium – nine week old carrot plant showing complete collapse and death of old leaves

Magnesium (Mg) Deficiency symptoms: Older leaves become strongly chlorotic (yellow) beginning at leaf edges. Red tints move in from the margins. Some backward curling of leaflets may occur. Bright yellowish orange colours develop at the margins of older leaves and the chlorosis extends to the main veins.

Occurrence: On acid soils; on soil with very high extractable potassium/magnesium ratios, or on very sandy soils subject to leaching after heavy rainfall.

Similar symptoms: Easily confused with N deficiency and Magnesium – mature healthy carrot leaf (left), ten week old leaf showing marginal chlorosis (centre) carrot motley dwarf virus. Symptoms and reddening (right) of Mg deficiency can occur as a result of restricted root growth, commonly due to soil compaction or wetness. Also frequently associated with low spring temperatures.

Magnesium – left to right: fourth, third and second leaves of 13 week old parsnip plant with chlorosis and scorched areas towards centre of leaf Sulphur (S) Deficiency Symptoms: New leaves are uniform yellow colour, and may appear frail. Parsnips leaves are also stiff and slightly concave

Occurrence: S deficiency has not yet been recorded as a problem in root vegetables, but likely to occur over the next decade due to the continuing decline in sulphur dioxide emissions from industry sources and lower atmospheric sulphur deposition.

Sulphur – nine week old carrot plant showing pale new leaves

Calcium (Ca) Deficiency symptoms: Necrosis (yellowing) of growing point and new leaves. Sudden appearance of short lengths (max 15mm) of watersoaked area petioles, leading to collapse of the upper portion of leaf whilst still green. In more advanced symptoms, these leaves shrivel up.

Occurrence: On acid soils following leaching rains, on soils with very high potassium levels (Index 7+), or on very dry soils. Associated with rapid growth in hot weather.

Similar symptoms: Frost damage and parsnip yellow fleck virus can give similar symptoms. Calcium – petiole collapse in thirteen week old carrot plant

Manganese (Mn) Occurrence: Deficiency symptoms: Frequently induced by overliming. Whole plant, but especially young Most severe problems occur on leaves, uniformly pale yellowish green organic and peaty soils with a pH and frail. Appearance in fields as above 6.0. Deficiency is common but patchy distribution of bright yellow generally less severe on sands and areas whilst the rest of the field a loamy sands, particularly at pH of 6.5 reasonably normal green. For parsnips and above. the symptom can be striking interveinal chlorosis. Symptoms are Similar symptoms: often transient and may disappear Differs from Mg and K deficiency in following rain. that the chlorotic areas are light green rather than yellow and in the whole plant being fairly uniformly affected.

Manganese – mature leaves from healthy (left) and deficient carrot plants Boron (B) the surface of the central carrot root sandy loams that have been limed Deficiency symptoms: as diffuse areas or tiny spots, has recently rather than those which are Leaflets of young leaves are greatly been demonstrated, in part at least, to naturally alkaline, and particularly reduced in size and later die back. be caused by boron deficiency. when the soil pH is raised above Older leaves are chlorotic, curled In parsnips new leaves are glossy, pH 6.5 and more usually over pH 7.0. backwards, giving prostrate habit, old ones pale, sometimes with a Since boron is water soluble and with purple edges to leaflets. Growing red margin. readily leached from sandy soils, point may die. Corky splits may occur deficiency is more common following on leaf petioles. Roots can split, Occurrence: a wet winter and spring, and exposing central core. Dark discoloura- Boron deficiency is more likely to particularly in dry summers. tion, known as ‘shadow’, shown on occur on sands, loamy sands and

Boron – 11 week old carrot leaves showing healthy (right) and deficient (left) Boron – chlorosis of older parsnip leaf

Boron – hollows in centre and breakdown of carrot cortex

Copper (Cu) Zinc (Zn) Iron (Fe) Deficiency symptoms: Deficiency symptoms: Deficiency symptoms: Youngest leaves of carrots become Extremely rare, but if seen, leaves Very rare in annual crops. Yellowing of very dark green and fail to unfold. become yellow. the young leaves and the veins stand Older leaves appear wilted. out green in contrast giving a Occurrence: herringbone appearance. Soil and Occurrence: Associated with sandy soils, that are plant analysis offers little help in Copper deficiency has only been high in pH and phosphate status diagnosing deficiency, as results are diagnosed in a few specific soil (Index 7+). difficult to interpret due to the situations but symptomless deficiency presence of other forms of iron within may be more widespread. It occurs the tissue. Also, sample contamination on peats and occasionally on loamy of soil by leaves growing close the peats, mainly in the Fens. Deficiency ground may elevate total iron results. also occurs on leached sandy soils, particularly reclaimed heathland. Occurrence: Occurs on chalk soils containing free lime, especially if poorly drained. Why analyse leaf Part of parsnip leaf for sampling samples?

There are two reasons for recommending the use of leaf analysis in carrot and parsnip crops: • To confirm a diagnosis based on the appearance of symptoms: in such cases the concentrations will usually be well below the ‘critical level’ and there should therefore be little doubt about the diagnosis. Cut

• To test for ‘subclinical’ deficiencies or toxicities which may be already limiting growth but which are not yet resulting in visible symptoms.

Guidance on methods of crop foliage sampling for nutrient analysis

It is essential to collect leaf samples Part of carrot leaf for sampling that accurately reflect the nutritional status of the crop submitted for analysis. Therefore to adequately represent any field or smaller area of crop, the following sample procedure should be followed: Cut • plants should be sampled at the 6 true leaf stage or when the roots are 10 + mm in diameter

• for each plant take the last fully expanded leaf

• if there is a clear differentiation between ’good’ and ‘poor’ crop, collect a second sample of leaves from the ‘good’ crop

• sample at least 25 plants to provide a minimum of 250 g material

• sample the crop following a ‘W’ pattern, collecting leaves randomly at regular intervals

• for carrots with compound leaves discard the main petiole but include • plant tissue damaged by insects When sending samples to an petioles of the individual leaflets in and mechanical equipment analytical laboratory the sample • ensure there is sufficient material • plant tissue which has been (250+ g) • collect leaves without any petiole for stressed by excesses of cold, heat parsnips or moisture • avoid soil contamination

Do not sample • plant tissue within a week after a • ensure that the sample is • diseased or dead plant material foliar application of nutrients or a representative of the crop/area fungicide • include all relevant documentation Although adequate soil fertility is and background information Soil nutrition important, carrots and parsnips do (sowing date, variety, field name, not generally require nutrient inputs growers details, etc) Though soil nutrition is outside the scope as high as for many other vegetable of this factsheet, growers are advised crops. However, carrots can be • pack the sample, typically in a Jiffy to consult and act upon the nutrition particularly susceptible to nitrogen, Bag, so it arrives in the best requirements and fertiliser management manganese, copper and boron possible condition for carrot and parsnip crops in ‘Fertiliser deficiencies. Recommendations for Agricultural and • do not post fresh material in an Horticultural Crops (RB208)’ or the airtight container appropriate crop protocols.

• label each sample clearly Interpretation of leaf tissue analysis • avoid sending samples before weekends and bank holidays Carrots Parsnips • send by overnight courier or deliver directly to the analytical laboratory Element Unit Deficient Normal Toxic Normal Range Range Precise and meaningful analytical results are only possible when Nitrogen % <2.0 2.0–4.5 3.0–4.8 carefully selected plant material is submitted for analysis. Phosphorus % <0.2 0.2–0.5 0.3–0.7

Potassium % <2.0 2.5–6.0 3.5–6.0 Interpretation of leaf tissue analysis results Magnesium % <1.15 0.2–0.5 0.4–0.8

Interpretation of laboratory results is Sulphur % 0.2–0.4 0.4–0.5 possible by comparison with normal levels expected for the crop. The Calcium % <1.0 1.0–3.5 1.2–2.0 interpretations given here are based on the best information available and Manganese mg/kg <20 20–200 30–200 relate specifically to the sampling instructions given. Boron mg/kg <20 20–60 >150 25–60

Copper mg/kg <5 5–25 >20 6–30

Zinc mg/kg <20 20–50 >100 20–40

Iron mg/kg 50–100 50–500

Sodium % 0.0–0.2 0.0–0.2

Overall strategy and foliage as appropriate to remedy a Nitrogen (N) problem in a particular field. Leaf analysis is valuable for the specific action to All trace elements except iron can be confirmation of plant N status. applied as simple salts, usually as Treatment is usually by addition of rectify nutrient foliar sprays. These are cost effective N fertiliser to the soil and plant deficiencies identif- treatments. Multi-element sprays may response to nitrate is very rapid not contain enough of a particular except when the surface soil is very ied from visual or element to correct a specific deficiency, dry. Foliar applications of N are and where no deficiency exists, appli- sometimes used as a ‘fire brigade’ laboratory testing cation can be wasteful. ‘Insurance’ treatment; foliar sprays of ammonium treatments are not recommended and nitrate salts can cause leaf As deficiencies normally occur where no deficiency has been identified, damage except at very low individually, specific treatments but where deficiencies are known to concentrations. Urea may be used but should be applied to the soil or crop occur prophylactic sprays may be used. there is still a slight risk of scorch. Phosphorus (P) magnesium sulphate (Epsom salts) Copper (Cu) Most soils have adequate P supplies. plus wetter in 500 l water may As there is often only a slight For severe deficiencies in a crop a accelerate recovery even when the difference in the copper content of foliar spray can be used but care must cause of the condition is poor soil healthy and deficient plants, plant be taken as leaf damage can occur, physical condition limiting root growth analysis has been of much less value particularly on hot/sunny days and at and nutrient uptake. in diagnosis than soil analysis. The high concentrations. Where P is disorder can be treated by application deficient, application to the soil is the Sulphur (S) of Cu compounds to soil using copper best treatment for subsequent crops. S deficiency has not been diagnosed sulphate or to leaf using copper in carrots or parsnips but in the longer oxychloride or cuprous oxide at Potassium (K) term there is a possibility that 2 kg/ha. Adequate applications of potassium deficiency will occur. fertiliser mean that K deficiency Manganese (Mn) should not be seen in carrots or Calcium (Ca) Plant analysis provides an accurate parsnips. Foliar feeding is not Ca is a major nutrient and provided diagnosis and response to foliar recommended because there is a high soil pH is satisfactory there should be application is usually rapid, with risk of leaf scorch. always be a good supply to carrots or effective control of the symptoms and parsnips. If Ca problems occur it is for the crop to recover and make Magnesium (Mg) generally not an absolute deficiency normal growth, though some It is more effective to apply Mg to the but rather the lack of movement of the irretrievable loss of yield may occur. soil than to use the ‘fire brigade’ element within the plant, due to water Apply 5 kg/ha manganese sulphate approach of a foliar spray. Applications stress, so it is the youngest tissues plus wetter in at least 250 l water or of Mg can be effective if symptoms which will suffer. Foliar sprays of Ca other proprietary sources. More than are seen very early, on soils with a low have not been found to be useful. one spray may be necessary. Mg content. Although visual Mg deficiency symptoms may be very Boron (B) Zinc (Zn) marked, the deficiency generally has Plant analysis is useful in the Leaf analysis is the most useful aid to only a small effect on plant growth diagnosis of boron deficiency diagnosis, but commercial incidence and yield is only slightly affected. especially when used in conjunction is extremely rare. Symptoms of Mg deficiency can with soil analysis. However soil occur as a result of restricted root treatment prior to sowing is preferable. Always check compatibility if growth, commonly due to soil If foliar sprays are required apply at mixing nutrients with compaction or wetness and frequently an early crop stage at 5-10 kg/ha agrochemicals associated with low temperatures in Solubor in at least 250 l water. the spring. Foliar sprays of 20 kg/ha

Toxicities through soil and plant analysis. Toxic It is not possible within this factsheet effects from over-application can last to list all the laboratories that offer leaf Manganese toxicity, particular in many years. nutrient analysis. Growers should parsnips, can occur in acid soils Chloride toxicity causes marginal discuss with their agronomist or crop especially those low in organic matter. leaf scorch, abscission and chlorosis. protection consultant. Symptoms of manganese toxicity are Usually associated with irrigating with darkening of leaf veins, usually on saline water Acknowledgement older foliage with interveinal chlorosis, Photographs courtesy of and leaf cupping or necrotic blotching. Foliar treatments should only be copyright of Warwick HRI. Boron toxicity occasionally found as applied when an identified problem a result of application of too much B. has been confirmed and when a Symptoms are marginal chlorotic foliage application is the preferred band on old leaves. method. Over-application can last Copper should not be applied to for years and in extreme cases lead soils without a demonstrated need to toxicities.

Further information available from the Whilst publications issued under the auspices © 2004 Horticultural Development Council. HDC office (01732 848383). of the HDC are prepared from the best available No part of this publication may be reproduced in information, neither the authors or the HDC can any form or by any means without prior permis- accept any responsibility for inaccuracy or sion of the Horticultural Development Council. liability for loss, damage or injury from the appli- August 2004 cation of any concept or procedure discussed. Design and production: HDR Visual Communication