Integrated Pest Management CROP NUTRIENT DEFICIENCIES & TOXICITIES

Plant Protection Programs College of , Food and Natural Resources

Published by MU Extension, University of Missouri-Columbia $3.00 IPM1016 This publication is part of a series of IPM Manuals prepared by the Protection Programs of the University of Missouri. Topics covered in the series include an introduction to scouting, weed identification and management, plant diseases, and insects of field and horticul- tural crops. These IPM Manuals are available from MU Extension at the following address: Extension Publications 2800 Maguire Blvd. Columbia, MO 65211 1-800-292-0969 CONTENTS Authors Gene Stevens, Department of Agronomy, University of Missouri-Delta Center How nutrient disorders develop ...... 3 Peter Motavalli, Science Program, Visual symptoms ...... 4 University of Missouri-Columbia Sulfur-nitrogen ...... 5 Peter Scharf, Department of Agronomy, Zinc-magnesium-iron-manganese ...... 5 University of Missouri-Columbia Others ...... 5 Manjula Nathan, Department of Agronomy, University of Missouri-Columbia Nutrient deficiency in corn ...... 6 David Dunn, Laboratory, Nutrient deficiency and University of Missouri-Delta Center toxicity in soybeans ...... 7

Nutrient deficiency in rice ...... 8 Credits Unless otherwise credited in the captions, the Nutrient deficiency in cotton ...... 9 photographs were provided by the authors. Many of the symptom descriptions were taken from MU Nutrient deficiency in wheat ...... 10 publication G9132, Signs of Crop Hunger, by Marshall Christy. Nutrient deficiency in alfalfa ...... 11 Plant tissue testing ...... 12 Five steps in plant tissue testing ...... 12 On the World Wide Web Sampling plant tissue ...... 12 Updates to this publication will be posted on the Submitting samples for testing ...... 14 World Wide Web at: Interpreting the test report ...... 14 http://muextension.missouri.edu/xplor/agguides/ pests/ipm1016.htm Diagnosing nitrogen need from plant color .15 Measuring greenness ...... 15 Radiometry ...... 16 Aerial imagery ...... 16 Production Other field quick tests ...... 17 MU Extension and Agricultural Infomation Dale Langford, editor Table 1. Essential plant nutrients ...... 3 Dennis Murphy, designer and illustrator Table 2. Environmental conditions associated with crop nutrient deficiency .12 Table 3. Guide for plant sampling of College of selected agronomic crops ...... 13 Agriculture Food and Table 4. Guide for plant sampling of Natural selected vegetables, fruits and trees . . .13 Resources Plant analysis submission form ...... 18 © 2002 University of Missouri the largest amounts. Micronutrients (iron, copper, manganese, zinc, boron, molybdenum, chlorine and nickel) are required in relatively smaller CROP NUTRIENT amounts in . Other mineral elements that are beneficial to some plants but are not consid- ered essential include sodium, cobalt, vanadium, DEFICIENCIES selenium, aluminum and silicon. A deficiency occurs when an essential element is not available in sufficient quantity to AND TOXICITIES meet the needs of the growing plant. Nutrient toxicity occurs when an element is in excess of plant needs and decreases plant growth or qual- ity. Nutrient deficiency or toxicity symptoms oil fertility is one of several factors, often differ among species and varieties of plants. including light, moisture, weeds, insects, Sand diseases, that affect crop yield (Figure 1). An important part of crop farming is being able to identify and prevent plant nutrient HOW NUTRIENT deficiencies and toxicities. This publication provides background information on the nature DISORDERS and development of crop nutrient disorders under DEVELOP the growing conditions commonly encountered in Missouri. It is a guide to identifying crop nutrient problems through observable symptoms on crop he occurrence of nutrient deficien- plants. Information is provided on effects of cies or toxicities is a result of soil, climatic conditions on plant nutrient availability, Tcrop, climatic, and cultural factors. and the results of soil and plant tissue testing. These factors interact to influence the availabil- Plants require 14 mineral elements for ity of nutrients to crop plants over the course of normal growth and reproduction. Each of these a growing season. nutrients has a function in plants and is required Soil properties influence the form, amount, in varying amounts in plant tissue (see Table 1). retention and movement of soil nutrients. The Macronutrients (nitrogen, phosphorus, potassium, effects of soil properties on water availability also calcium, magnesium and sulfur) are required in influence nutrient availability, because water is Table 1. Essential plant nutrients. essential for chemical reactions, biological activ- ity, and the transport and absorption of nutrients Chemical Relative % by roots. Among the critical soil chemical prop- Name symbol in plant* Function in plant Nutrient category erties affecting soil nutrient availability are soil pH Nitrogen N 100 Proteins, amino acids (a measure of the acidity or alkalinity of a soil) and Primary Phosphorus P 6 Nucleic acids, ATP macronutrients soil cation exchange capacity (a measure of the Potassium K 25 Catalyst, ion transport capacity of the soil to retain positively charged Calcium Ca 12.5 Cell wall component nutrient ions). Some important physical proper- Secondary Magnesium Mg 8 Part of macronutrients ties affecting nutrient availability are soil texture Sulfur S 3 Amino acids (the proportion of sand, silt and clay-sized parti- Boron B 0.2 Cell wall component cles in a soil), clay mineralogy (the type of soil Chlorine Cl 0.3 Photosynthesis reactions clay), and soil structure (the physical arrange- Copper Cu 0.01 Component of enzymes ment of soil particles). Iron Fe 0.2 Chlorophyll synthesis The of Missouri vary widely in their Micronutrients inherent and suitability for crop Manganese Mn 0.1 Activates enzymes production. Information about the specific soil Molybdenum Mo 0.0001 Involved in N fixation resources on your farm can be obtained by Nickel Ni 0.001 Component of enzymes consulting your regional extension specialist or Zinc Zn 0.03 Activates enzymes your county Farm Service Agency office or by *Relative amounts of mineral elements compared to nitrogen in dry shoot tissue. May using the Center for Agricultural Resource and vary depending on plant species. Potential yield VISUAL Insects and diseases SYMPTOMS Weeds

Improper crop variety utrient disorders may appear in Poor soil structure many ways in a plant, including Lack of moisture Poor stand Low fertility Nstunting or reduced growth, off- colored leaves (often white, yellow or purple); abnormally shaped leaves, stems, and roots; and a breakdown of certain parts of the plant, includ- ing the root system. “” is a type of defi- ciency or toxicity symptom characterized by yellowing that can be generalized over the whole plant, localized over individual leaves or isolated between some leaf veins (interveinal chlorosis). “Necrosis” is a type of deficiency or toxicity symp- tom characterized by death of plant tissue some- times in spots. Yield and quality of grain or fiber Figure 1. Low soil fertility is only one of several factors that can limit crop yields. may suffer when nutrition is inadequate. When inspecting plants for symptoms of Environmental Systems (CARES) Web site nutrient disorders, compare plants displaying (www.cares.missouri.edu).The parent material of symptoms with normal ones and examine new some soils may contain a large amount of certain and older leaves. Nutrient deficiencies generally plant nutrients (e.g., potassium, calcium and appear first in the oldest leaves when nitrogen, magnesium) and, therefore, the possibility of a phosphorus, potassium, and magnesium are limit- plant response to additional sources of ing. These nutrients move from one part of the those nutrients may be reduced. In addition, plant to another as needed. certain soils have natural soil physical and chem- Younger leaves and terminal buds show a ical restrictions that can limit potential crop deficiency when sulfur, iron, calcium, zinc copper, productivity. A prior knowledge of your soil boron, manganese or chlorine are limiting. These resources will help you to develop a successful nutrients do not readily move about in the plant. program. As a deficiency becomes more severe, visual Primary and secondary macronutrients are symptoms may spread to the whole plant, leaves often limiting factors for crop production in may become more chlorotic or bleached in appear- Missouri depending on soil conditions and prior ance, or stunting, deformity and death of plant management. Most soils in Missouri have suffi- parts may become more extensive. Deficiencies of cient amounts of micronutrients to supply plant certain nutrients, such as sulfur and phosphorus in needs for crop production, but individual crop corn, may also be visible only early in the growing species may have special micronutrient require- season because of immature root development or ments, and soil properties may vary. cold weather, and then become less apparent as the Factors such as soil pH and moisture can plant matures and the weather warms up. affect the solubility of nutrients or interfere with Symptoms of nutrient toxicity vary, depend- the ability of plant roots to absorb nutrients ing on the element and the crop. Essential nutri- (Figure 2). Deficiencies of micronutrients occur ents that can be toxic to plants include manganese, most often in soils with high pH (with the excep- copper, boron and chlorine. Excessive quantities tion of molybdenum). Phosphorus availability is of other nutrients in the soil may cause nutrient reduced by soil acidity and alkalinity. Low soil pH imbalances in plants, resulting in poor growth increases the availability of aluminum and and crop quality. manganese, which can result in toxic levels of Visual symptoms of nutrient deficiency or these elements. toxicity can be confusing because of problems with more than one nutrient. Symptoms associ-

4 Integrated Pest Management ated with different nutrients may resemble crop Soil pH injury caused by herbicide damage, insect damage, or the effects of plant diseases. Listed 4 5 6 7 8 9 below are nutrient deficiencies that may be diffi- cult to determine without laboratory tests. Nitrogen Sulfur–Nitrogen Phosphorus Symptoms of sulfur deficiency in crops are similar to those of . The main difference is that sulfur deficiency may cause leaf Calcium, Magnesium yellowing, beginning in the younger leaves, whereas nitrogen deficiency starts in the older Potassium Iron leaves and then spreads to the whole plant. In Manganese some environments, sulfur and nitrogen deficien- Zinc Copper Sulfur cies can cause yellowing between the leaf veins. Cobalt Without tissue testing, these similarities may cause misdiagnosis of the problem. Tissue testing effec- tively determines whether nitrogen or sulfur is in short supply. Molybdenum Zinc–Magnesium–Iron–Manganese Deficiencies of zinc, magnesium, iron, and Boron manganese all typically cause yellowing of the tissue between leaf veins. Deficiencies of iron and manganese usually occur in high-pH soils, but these are rare in Missouri. Zinc deficiency is most Figure 2. The relative availability of nutrients to plant roots depends on the pH level of the soil. common in corn, and the bleached area can spread to include the veins, but the midrib and leaf edges usually stay green. With magnesium defi- ears or grain. Split the stalks and study the inter- ciency, yellowing between veins will be seen nal circulation system. If you observe potassium mainly on older (lower) leaves, while zinc, iron deficiency symptoms in cotton, always check and manganese deficiency symptoms will be seen inside the stalks for discoloration from Verticillium mainly on younger (upper) leaves. Magnesium or Fusarium wilt. Likewise, check for soybean deficiency is best diagnosed with a soil test. cyst nematodes on soybean plants with potas- sium deficiency symptoms. Do not overlook Others possible contributing causes: disease, insects, Use care to distinguish among various under- herbicides, temperature, physical soil conditions lying causes of crop deficiency symptoms. Insect and moisture conditions. Plants stressed from damage may look like a nutrient deficiency. lack of nutrients are often more susceptible to Herbicides sometimes affect root, stem and leaf diseases and some insects. development, thereby impairing nutrient uptake. The following pages depict nutrient defi- Diseases also can impair nutrient uptake by roots ciency and toxicity symptoms in corn, soybeans, or the translocation of nutrients in the plant. rice, cotton, wheat and alfalfa. Examine stems and stalks, root systems and the

Crop Nutrient Deficiencies and Toxicities 5 6 Corn nitrogen deficiency. indicate brown midribs Figure 3.Yellow or slow maturity (Figures 5 and 6). off); (rot weak roots kernels); dull-colored (starchy, nubbins chaffy tips; ear filled poorly internodes; lation in joints; weak stalks and excessive lodging; short accumu- iron ragged; edges leaf first); affected leaves (oldest edges leaf along and tips at drying or Firing yields (Figures 3 and 4). but highinfats);lightbrownstoveratmaturity;poor pinched off: kernels have glossy luster (low in protein, tip ear tip); at fill to (fail ears small growth; stunted remain green (oldest leaves affected first); spindly stalks; edges while Yellowingmidrib along and tip leaf from Nitrogen deficiency Bryan. Gerald Photo: easily lodged. deficiency isstuntedand withpotassium Corn Figure 5. Potassium deficiency or yellow leaves. plantshavecorn palegreen Nitrogen-deficient Figure 4. Integrated Pest Management along edesoflower leaves. bronzing andyellowing causes deficiency incorn Potassium Figure 6. upper corn leaves.upper corn Zincdeficiencycausesyellow inthe stripes Figure 8. Fgr 9). (Figure slickness distinctive a reveal may tissue affected the rubbed, When leaves. lower on mainly veins; leaf between bleaching or streaking yellowish or White yellow onthelower stripes leaves. willhave Magnesium-deficient corn whiteor Figure 9. curved ears; retarded maturity (Figure 7). stalks; missing rows of kernels on ears: small twisted or barren and pollination imperfect silks; of emergence delayed system; root shallow stalks; weak varieties); some of characteristics be (may plants young of tips leaf and stalks purplish growth; early slow Stunted, have leaves. purple plantssometimes corn Phosphorus-deficient Figure 7. Zinc deficiency remain green. bleached area between midrib and leaf margins, which a form to together join may Stripes 8). (Figure leaves Narrow yellow or white stripes between veins of upper Soybeans 7 Figure 14. Dead areas in field were this soybean sodium caused by toxicity. Salt toxicity tolerance; salt affect moisture soil in changes Seasonal salt dry, becomes soil as spring; in healthy be may plants causes plants to wilt and die; soil may have a white or and 14 (Figures surface the on crust gray-colored light 15). Potassium deficiency Potassium and drying edges, leaflet on mottling yellow Irregular curling downward (older leaves affected first); dead leaf tissue falls away from leaf edges leaving ragged appearance; shriveled, poorly shaped seed; delayed 13). (Figure yields poor and maturity Figure 13. causes deficiency in soybeans Potassium veins. areas along leaf margins between yellow Figure 15. White crystals on usually indicate soil surface of sodium for levels toxic soybeans. Photo: Hefner. Steve Crop Nutrient Deficiencies and Toxicities Nutrient Deficiencies and Crop ellowing Figure 11. Manganese deficiency causes y between veins. between Manganese deficiency Manganese Leaves are mostly yellow, gradually becoming dark dark on usually are plants deficient veins; to next green sandy soils that tie up manganese. Foliar or banded applications of manganese fertilizer are used to mini- 11). and 10 (Figures fixation mize Figure 10. on right from manganese-deficient are Leaves plants. soils. common on low-pH is Manganese toxicity Boron toxicity Boron Figure 12. areas on soybean causes brown Boron toxicity leaves. Leaves have scorched appearance and eventually fall off fall eventually and appearance scorched have Leaves 12). (Figure plants the 8 Rice and doesnotform afullcanopy. ispale green incolor Nitrogen-deficientrice Figure 17. canopy over water; poor yields (Figures 17 and 18). complete a form not do plants leaves; older of tip spindly stemsandshortheads;yellowingstartsatleaf with extreme yellowing of lower leaves on young plants; green yellowish pale stalks and leaves tillering; Poor Nitrogen deficiency brown areasonleaftipsandedges. Potassium-deficient willhave rice yellow or Figure 16. 16). toms usually develop after internode elongation (Figure leaves; severity of condition varies by variety; of leaf symp- margins and tips on discoloration brown or Red nitrogen statusofrice. metercanbeusedtomonitorthe and thecholorphyll Tools suchastheplantareaboard(above)Figure 18. Potassium deficiency Integrated Pest Management to starve forto starve oxygen. seedlings Zincdeficiencycausesfloodedrice Figure 19. plants will die (Figures 19 and 20). quickly,rice drained not is field the if fields; in tions is most acute at the water inlet or other high pH loca- erect. If well water has calcium carbonate, the problem standing of instead surface water the on limply float Leaves begin to turn brown after flooding fields; plants Zinc deficiency deficiency, plantswilldie. rice Ifthewater isnotdrained fromfieldswithzinc Figure 20. preplant phosphorus fertilizer.preplant phosphorus didnotreceive Riceplantsonthe right Figure 21. rity; poor yield and milling (Figure 21). age; abnormal bluish green color of foliage; slow matu- same the of plants healthy with compared are plants Slow, dwarfed growth; may not be noticeable until sick Phosphorus deficiency Cotton 9 Potassium deficiency “Rust” starts with yellowish white mottling of leaves; tip and margin of leaves scorch and curl downward; prema- shed and die brown, reddish turn leaves whole suscep- more are plants bolls; immature dwarfed turely; 27). and 26 (Figures diseases wilt to tible Figure 26. with potassium deficiency have Cotton leaves edges. or bronze yellow Boron deficiency Boron as petioles; leaf on rings dark usually is symptom First the season progresses, some leaves may become 25). (Figure deformed Figure 25. terminal. Chronic boron deficiency on cotton Photo: Extension Arkansas Cooperative Miley, Woody Service. Figure 27. deficiency in cotton at midbloom. Potassium Crop Nutrient Deficiencies and Toxicities Nutrient Deficiencies and Crop Low soil pH Magnesium deficiency causes purplish red leaves with mistaken easily be can season in late symptoms veins; green 23). (Figure leaves lower in first appears aging; normal for Figure 22. strips Light green in this cotton field indicate of nitrogen fertilizer. poor distribution Poor germination and emergence; death of seedling plants; new leaves are “crinkled” as in thrips insect damage; yellowish green foliage color; limited and petioles; leaf of collapse and bending fruiting; delayed (Figure maturity delayed system; root underdeveloped 24). Figure 24. aluminum can have on acid soil Cotton grown and manganese toxicity.The crinkle leaf symptom is insect damage. for often mistaken Photo: Milam. Mike Figure 23. Magnesium deficiency causes purplish leaves in cotton. Magnesium deficiency Nitrogen deficiency Nitrogen green foliage; older Yellowish leaves dry up and shed to fail branches fruiting growth; stunted prematurely; 23). and 22 (Figures develop 10 Wheat injury from blowing sand (Figure 29). and disease by caused symptoms to similar are ciency supporting tissue test results. Symptoms from K defi- without diagnose to difficult is wheat in deficiency yellow or brown along the tips (Figure 28). Potassium are deficiency potassium with wheat of leaves The will usually be of normal size andcolor.will usuallybeofnormal resembling potassiumdeficiency, but therestofplant Blowing sandcancausescorchedleaftips Figure 29. Potassium deficiency along theedgesindicatepotassiumdeficiency. Leaves withyellow tipsbecomingscorched Figure 28. Integrated Pest Management leaves. Nitrogen-deficientwheatisstuntedwithyellow Figure 31. Sulfur deficiency indicate sulfurdeficiency. Wheatleaves withpalegreen oryellow color Figure 30. dead leaf tips are signs of phosphorus deficiency.dead leaftipsare signsofphosphorus leaves Stuntedwheatplants withpurple and Figure 32. sulfur deficiency (Figure 30). and nitrogen between distinguish to needed usually is testing Tissue applied. is fertilizer nitrogen more when “green-up” to fail and leaves green pale have with low organic matter. Wheat plants with low sulfur Sulfur deficiency in wheat usually occurs on sandy soils deficiency (Figure 31). sulfur of symptoms the resembling yellow, or green pale is plants nitrogen-deficient in color Leaf plan. healthy than tillers fewer produce and height plant reduced have deficiency nitrogen with plants Wheat Nitrogen deficiency become purple or brown (Figure 32). plants phosphorus-deficient cases, severe In toms. acterized by stunted growth with no distinct leaf symp- Mild phosphorus deficiency in wheat can only be char- Phosphorus deficiency Alfalfa 11 Figure 37. Leafhopper injury can be confused with boron “V” causes a yellow deficiency but at the tip of a leaf. Figure 36. Closeup of boron-deficient alfalfa. Boron deficiency Boron than alfalfa in common more is boron of deficiency The reddish a develop leaves upper The . other in (Figures 35 and 36). Injury yellow rosette appearance or boron for confused often is leafhopper potato from 37). (Figure deficiency potassium Figure 35. areas in alfalfa Boron deficiency causes yellow fields. Crop Nutrient Deficiencies and Toxicities Nutrient Deficiencies and Crop Figure 33. leaves alfalfa White spots on edges of lower potassium deficiency;are caused by as plants get older turn yellow. leaves Yellow leaf color in alfalfa may be caused by potassium by caused be may alfalfa in color leaf Yellow the of bottom the at begins deficiency This deficiency. plants with small white spots on leaf edges. As potas- spots the between tissue the progresses, deficiency sium and the leaves become ragged. turns yellow or brown most the affected usually are cuttings third and Second 33). (Figure deficiency potassium by Potassium deficiency Potassium Figure 34. phosphorus caused by growth Stunted alfalfa deficiency. Alfalfa plants with phosphorus deficiency have retarded have deficiency phosphorus with plants Alfalfa 34). (Figure leaves small and growth Phosphorus deficiency Table 2. Environmental conditions associated with selected crop nutrient deficiencies. PLANT TISSUE TESTING Nutrient Conditions favoring deficiency

Macronutrients oil testing is the foundation of a sound Nitrogen ¥ Wet currently, or wet since fertilizer nutrient management program and will application help prevent the development of crop ¥ Surface application of urea S ¥ Broadcast N solution on high-residue nutrient deficiencies. Soil and plant testing are surface also valuable diagnostic tools when possible nutri- Phosphorus ¥ High or low soil pH ent deficiency symptoms are seen. Similar visual ¥ High soil clay content symptoms may be caused by different nutrient Potassium ¥ Dry or wet soil deficiencies or toxicities and by herbicide injury, ¥ Compacted soil diseases, insect damage or environmental condi- Sulfur ¥ Sandy soil low in organic matter Figure 38. “Hidden tions. As a result, diagnosis based on symptoms ¥ Cool, wet weather alone is much less reliable than diagnosis based on hunger,” caused by mild Micronutrients nutrient deficiencies, symptoms plus additional evidence, which may can be detected only by include soil test results, results or Zinc ¥ Very low (terrace soil or tissue analysis. channels, cut areas in leveled fields) knowledge of other factors that are associated ¥ Cool, wet weather with deficiencies of particular nutrients (see ¥ High soil pH Table 2). Iron ¥ High soil pH Plant tissue testing is the most accurate of all Manganese ¥ High soil pH diagnostic tools for nutrient deficiencies, partic- ularly when paired samples are taken. Plants with possible deficiency symptoms should be compared Sampling plant tissue with nearby plants that appear to be healthy. Nutrient analysis of plant tissue at different Tissue testing is also the only way to detect growth stages is a major tool for determining "hidden hunger." Mild nutrient deficiencies may which nutrients are limiting growth. Plant moni- not produce obvious visual symptoms, such as toring with tissue testing is especially important leaf yellowing or chlorosis. However, significant with high value crops. Plant nutrient content will reductions in crop yields can occur with these vary depending on the type of plant being deficiencies. Steps for successfully using tissue sampled, the specific plant part sampled, and the tests are shown in the box below. stage of growth of the plant. Tables 3 and 4 provide guides for suggested stages of growth and plant parts to sample for

Five steps in plant tissue testing

1. Determine correct 2. Handle samples prop- 3. Clearly label all sample 4. Complete plant sample 5. Maintain records of plant part to sample erly after collection to bags and maintain information forms for plant tissue test results and how many plants to avoid contamination and records of sampling date, submission of samples to and consult regional and sample (see Table 3). potential molding. field name or number your regional soil and local extension agents if Collect samples from and any other identifying plant testing laboratory. you have questions about affected plants and from information. the results and the test nearby healthy plants. interpretations.

12 Integrated Pest Management Table 3. Guide for plant sampling of selected agronomic crops.

Plant Stage of growth Plant part Number of plants to sample Seedling (<4 inches in height) Whole aboveground plant 20Ð30 Early growth (>4 inches in height Entire leaf fully developed below the whorl 15Ð25 Corn to tasseling) Tasseling/bloom Earleaf 15Ð25 Maturity Earleaf 15Ð25 Seedling Whole aboveground plant 20Ð30 Soybean Early growth and flowering Most recently matured trifoliate leaves 20Ð30 Seedling to tillering Whole plant 50Ð60 Small grains Before heading Upper 1/3rd of plant 50Ð60 Before bloom (1/10th bloom) Top 6 inches or top 1/3 40Ð50 Alfalfa Harvest Top 6 inches or top 1/3 40Ð50 Head fully emerged but before Sorghum Most recently matured and fully expanded leaves 15Ð25 pollination Cotton First square to midbloom Fourth petiole from the top of plant 30Ð40 Rice First tiller (preflood) Whole aboveground plant 25Ð35 Sources: Campbell, C.Ray (ed.) 2000. Reference sufficiency ranges for plant analysis in the Southern Region of the United States. Southern Cooperative Series Bulletin #394, Raleigh, N.C. Mills, Harry A., and J. Benton Jones, Jr. 1996. Plant Analysis Handbook II, MicroMacro Publishing, Inc., Jefferson City, Mo.

Table 4. Guide for plant sampling of selected vegetables, fruits and trees. Number of plants Plant Stage of growth Plant part to sample Apples July 15 to August 15 Leaf from middle of current terminal shoot 60 Asparagus Mature fern (August) Fern from 17 to 35 inches up 20 Beans, snap Initial flowering Young mature trifoliate 50 Beans, table Mature Young mature leaf 20 Blueberries First week of harvest Young mature leaf 50 Broccoli Heading Young mature leaf 15 Heads, 1/2 grown Young wrapper leaf 15 Cantaloupe Early fruiting Fifth leaf from tip 25 Carrots Midgrowth Young mature leaf 25 Cauliflower Buttoning Young mature leaf 15 Celery Half-grown Young mature leaf 20 Cherry Summer Mature leaves from new growth 50 Cucumbers Early fruiting Fifth leaf from tip 20 Grapes Flowering Petiole from young mature leaf 75 Lettuce Heads, 1/2 size Wrapper leaf 20 Onions Midgrowth Top, no white portions 25 Peaches/nectarines Spring at fruit set Midshoot leaf 20 Peas First bloom Recently matured leaflet 50 Pecan 56Ð84 days after terminal bud set Leaflet pairs from new growth 25 Peppers Early fruiting Young mature leaf 20 Plum Summer Whole leaf from midshoot growth 25 Potatoes 40Ð50 days after emergence Young mature leaf 20 Pumpkin/squash Early fruiting Young mature leaf 15 Radishes Midgrowth to harvest Young mature leaf 40 Raspberries First week in August Leaf 18 inches from tip 50 Spinach 30Ð50 days old Young mature leaf 35 Strawberries At flowering Young mature leaf 20 Sweet corn Tasseling to silk Ear leaf 10 Tomatoes First mature fruit Young mature leaf 20 Walnut (black) Summer Mature leaf from new growth 5 Walnut (English) Summer Center leaflet from mature leaf 25 Watermelons Midgrowth Young mature leaf 15

Crop Nutrient Deficiencies and Toxicities 13 common agronomic and horticultural crops in growing well and from another area in which the Missouri. When the recommended plant part is plants are affected by a suspected nutrient disor- sampled at the designated stage of growth, the soil der. This comparison can assist in diagnosing and plant testing laboratory can compare the specific nutrient problems, especially when nutri- results of the tissue test with established nutrient ent sufficiency ranges are not available for a sufficiency ranges for the crop. specific crop, growth stage or plant part. Plant If specific sampling instructions are not found tissue samples from one plant may not be repre- in the selected crops, the rule of thumb is to sentative of all the plants in a field with a similar sample upper, recently matured leaves. The problem. To obtain a representative sample, avoid recommended time to sample is just before the collecting plants that have insect damage, are beginning of the reproductive stage for many infested with disease, are covered with dust or soil plants. More specific information on plant tissue or foliar-applied sprays, or are border row plants. sampling procedures and available nutrient suffi- If possible, take random plant samples from ciency ranges can be obtained by consulting your several plants distributed throughout the affected regional soil and plant testing laboratory. area of the field. In sampling plants for tissue testing, it is crit- ical to obtain a representative sample. Take sepa- Submitting samples for testing rate plant samples from an area in which plants are Remove any soil or foreign matter on the collected plant material by wiping with a clean damp cloth or rinsing directly with water while the material is still fresh. Place the collected plant tissue samples in a clearly labeled paper bag. If the plant part is collected and stored in plastic bags for more than several hours, be sure to refriger- ate it to prevent the plant material from molding. Air dry the plant sample for 12 to 24 hours before mailing it in an envelope or dropping it off at your regional soil and plant testing laboratory or exten- sion office. Maintain records of the sampling date, field location, submission date to the soil and plant testing laboratory and any prior results of tissue or soil testing. These records will help you to keep track of your samples and assist you in moni- toring the effectiveness of your fertility manage- ment program over time. Your regional soil and plant testing laboratory will have forms for submission of samples for plant tissue testing (see the Plant Analysis Information Form for the University of Missouri Soil and Plant Testing Laboratory, page 18). Providing the requested information on the forms is crucial for interpreting analytical results from plant tissue testing. You may wish to consult your local or regional extension agent or the soil and plant testing laboratory as to the appropriate analytical tests for your situation. Interpreting the test report You will be sent your plant sample test results within about five working days after the MU soil and plant testing laboratory receives your plant samples (times may vary for other labs). An inter-

14 Integrated Pest Management pretation of the results will also be included based higher for that nutrient in the healthy area than on crop and management information, available in the affected area, then deficiency of that nutri- nutrient sufficiency ranges, available soil test ent is strongly indicated. For example, if brown- information, and (when paired samples are ing of the edges of older (lower) leaves is observed, submitted) comparison of test results from and tissue potassium levels are higher in healthy affected and healthy areas (see the example of a plants than in affected plants, then potassium plant tissue test report on page 14). deficiency is a solid and convincing diagnosis. The sufficiency level for a particular nutrient If you do not submit healthy plants, the may depend on genetic and environmental results from your affected plants will instead be factors. The sample from the healthy area of your compared with a large database of tissue test field establishes the tissue nutrient levels needed results for your crop to determine which nutrients for healthy plants, given the genetics, soil type, may be deficient or excessive. Once a diagnosis of and weather specific to your field. nutrient deficiency is made, the appropriate nutri- Only nutrients with substantially different ent may be applied immediately or for the next test levels between the affected and healthy areas growing season. Your local or regional extension should be considered as possibly deficient and specialist can assist you in understanding the contributing to the observed symptoms. If the report and determining its significance for your observed symptoms are typical for a particular future management. nutrient deficiency, and if the tissue levels are

DIAGNOSING NITROGEN NEED FROM PLANT COLOR

itrogen is one of the most Crop color can also be measured using commonly deficient plant nutrients instruments designed for this purpose. This Nbecause large amounts of this approach may allow greater sensitivity to small element are required to produce amino acids and differences in color, as well as making it easier to proteins in the tissue and because nitrogen is collect enough color information to get a good easily lost from the soil during wet conditions. field average. It can also be used to characterize Nitrogen-deficient crops are lighter green in color the spatial variability of crop color in support of than healthy crops. The lighter the green, the variable-rate nitrogen applications. Several differ- more severe the deficiency and the more nitrogen fertilizer will be required to correct the deficiency. Crop color can be used as a guide to how much fertilizer to apply to correct deficiencies. There is also pressure, for environmental reasons, to reduce overapplication of nitrogen fertilizer. Diagnosing nitrogen need from plant color has the potential to give accurate nitrogen rate recommendations that will ensure optimal crop yield while reducing overapplication of N. Measuring greenness The simplest way to measure plant color is by visual comparison to a color scale. The University of California has developed a leaf color chart to measure the “greenness” of crops (Figure 39), and has developed interpretations of the color Figure 39. Visual rating of "greenness" of corn plants with leaf color chart (scale 1 to 8). chart to guide midseason nitrogen applications for The row on the right did not receive nitrogen fertilizer. Preplant nitrogen fertilizer was rice. applied in the left row.

Crop Nutrient Deficiencies and Toxicities 15 Figure 40. SPAD Figure 41. Hand-held devices such as a SPAD chlorophyll chlorophyll meter. meter can be used to monitor the nitrogen status of crops.

ent types of instruments can be used in measur- ing crop color. One of the simplest is the Minolta SPAD chlorophyll meter, a portable hand-held device that clamps over a leaf (Figures 40 and 41). This meter measures transmittance of red and infrared light through the leaf and displays a number that is proportional to the nitrogen and chlorophyll concentrations in the leaf. As with soil Figure 42. A spectral radiometer mounted on a variable- rate applicator can reduce overapplication while deliver- or tissue samples, numerous measurements spread ing nitrogen fertilizer where it is needed. out evenly over the sample area must be taken to get a reliable average. Several states have devel- oped or are developing interpretations to convert meter readings to nitrogen fertilizer recommen- dations. Radiometry A spectral radiometer can also be used to measure crop color. Most spectral radiometers measure light intensity over a range of visible and near-infrared light wavelengths. One advantage of spectral radiometers, relative to the chlorophyll meter, is that they can be mounted on nitrogen applicators (Figure 42). The color measurements Figure 43. Aerial images can assist in detecting crop stresses, then represent a much larger amount of plant including nutrient deficiency. In Missouri, nitrogen deficiency and waterlogging are the main causes of yellow-green corn. tissue, can capture spatial patterns in crop color, and can be used to guide variable-rate nitrogen applications. Norsk Hydro manufactures a system Aerial imagery based on this concept for variable-rate nitrogen Aerial images acquired with film or with digi- applications to small grains. tal image capture from satellites or airplanes The disadvantage of spectral radiometers is provide another way to measure crop color that their readings are sensitive to sunlight inten- (Figure 43). This approach is particularly well sity, sun angle, cloud cover and interaction of sun suited for detecting for nitrogen deficiencies, angle with plant geometry. A radiometer posi- because large areas can be examined quickly. tioned to measure the intensity of incoming light, Images are also well suited for detecting spatial as well as the light reflected from the crop, helps patterns of nitrogen deficiency and producing to correct for these variations. Additional variable-rate nitrogen recommendations. advances in these areas will improve the quality Experiments in Missouri have produced methods of the nitrogen recommendations from spectral for interpreting images to produce nitrogen rate radiometers. recommendations for corn, but capabilities for

16 Integrated Pest Management acquiring and processing images and delivering results to producers in a timely manner remain limited. It may be difficult to detect nitrogen deficiencies from aerial images before the crop has a high percentage of ground cover. Factors other than nitrogen deficiency can cause light-green or yellow-green coloration of crops. These factors include disease, insect damage, herbicide damage, and deficiencies of other nutrients. Automated sensors probably cannot detect the other features that allow the human eye to distinguish between these causes. Thus, these sensors are most suited to production systems in which nitrogen deficiency is by far the most common cause of light-green foliage. This would be the case when a main part of the crop’s Figure 44. Using a Cardy¨ meter to test nitrate in cotton plants begins with extracting nitrogen fertilizer requirement is to be applied sap from cotton petioles with a garlic press. based on color measurements. Humid regions, with greater potential for nitrogen loss and defi- ciencies, will be more suited to these tools than Among the disadvantages of quick test kits is semiarid regions. Soils with high pH may be less their sensitivity to differences in types of plants, suited for these types of color measurements sample handling, and the time of day when because of relatively common micronutrient samples are taken. For example, time of day, (iron, manganese, zinc) deficiencies that cause a temperature and cloudiness can affect the concen- light green or yellow-green color in the crop. tration of nitrate in plant sap and the calibration of the instrument. For consistent results, samples Other field quick tests should be collected at a standard time of day (10 New technology and the need for rapid in- am to 2 pm) and taken indoors for analysis or in field plant testing results have stimulated an inter- a shady area away from direct sunlight and wind. est in “quick test kits” for determining plant nutri- For woody plants, such as cotton, collecting suffi- ent deficiencies. These kits often have the cient sap to test can be a problem. Often it helps advantages of being portable, less expensive than to freeze the sample briefly because freezing standard laboratory methods, and suitable for use breaks down the cell walls and releases a larger by growers and consultants without extensive volume of sap. laboratory training. The usefulness of quick tests for plant nutri- Extensive research has been conducted, espe- ent management depends on the availability of cially among horticultural crops, on several quick research-based information for interpreting test procedures, including the measurement of nutrient concentrations in plant sap for specific nitrate and potassium in plant sap as indicators of crops. In Misssouri, research is being conducted plant nitrogen and potassium nutrition. for developing interpretation information for Concentrations of nitrate and potassium are nitrogen and potassium readings from the usually measured with an ion-selective electrode Cardy® meter for cotton. Interpretation tables (for example, the Horiba Cardy® nitrate or potas- should provide information that shows the ranges sium meters, Figure 44) or by use of colorimet- of deficient and sufficient nutrient concentra- ric test strips (for example, Merckoquant® nitrate tions for plant sap for the specific plant part and test strips). With the ion-selective electrode, growth stage of the sampled crop. nitrate or potassium concentrations are deter- Other disadvantages of many quick test kits mined based on readings from standard solutions are a lack of quality control (e.g., use of standards of known concentrations. For test strips, a cali- and blanks to ensure the test procedure is work- brated color chart or a strip color reader can be ing), dependence on a single supplier for new used to estimate the color intensity, which is then reagents and replacement parts for the kit, and the converted to nutrient concentrations based on effects of improper storage on the viability of information supplied with the kit. chemicals or strips used in the procedures.

Crop Nutrient Deficiencies and Toxicities 17 Plant Analysis Soil and Plant Testing Laboratory 23 Mumford Hall, University of Missouri Columbia, MO 65211 573-882-0623 Fax: 573-884-4288

(Please type or print) Lab # Lab Use Only Date Sampled ______/______/______Date Received Name Firm submitting Address Address

(City) (State) (zip code) (City) (State) (zip code) Tel: Fax: Tel: Fax: e-mail address e-mail address County to be billed & Code______Firm # Outlet #

Sample identification Crop Field I.D. Previous Crop Stage of Growth Accompanied by soil sample? Yes______No_____ Moisture If Yes: Serial # When last limed Soil Test Results Position on landscape N P K Ca Fertilizer applied Mg pH OM CEC Other: Description of problem:

Check Tests Desired for this sample Analysis Cost Total Cost Regular Analysis: Nitrogen, phosphorus, potassium, $17.00 calcium and magnesium + drying and/or grinding Micronutrients: (with regular analysis) $6.00 Fe, Zn, Cu, Mn ($1.50 per micro-nutrient) Analysis Package: (Regular+Micronutrients+Boron) $25.00 N, P, K, Ca, Mg, Fe, Cu, Zn, Mn, B Individual analyses (per nutrient) Nitrogen (TKN) $10.00 Phosphorus (P) $5.00 Potassium (K) $5.00 Calcium (Ca) $4.00 Magnesium (Mg) $4.00 Iron (Fe) $4.00 Copper (Cu) $4.00 Manganese (Mn) $4.00 Zinc (Zn) $4.00 Sulfate-S $6.50 Nitrate-N $8.00 Boron (B) $5.00 Chloride $6.50 Sample Grinding $2.00 Total Due for this sample

We encourage a plant sample be taken from a poor growing area and compared to a sample from an adjacent normal area. The testing fee for a good sample accompanying an abnormal sample will be analyzed at one-half the regular price. Samples will be discarded after 30 days unless other arrangements are made. November 2000

18 Integrated Pest Management For further information Available from Extension Publications 1-800-292-0969 XPLOR [Extension Publications Library on Request] on the Web at http://muextension.missouri.edu/xplor/ EC929 Ð Micro and Secondary Nutrients in Missouri G9110 Ð How to Get a Good Soil Sample G9112 Ð Interpreting Missouri Sil Test Reports G9174 Ð Nitrogen in Missouri Soils G9175 Ð Nitrogen Management for Conservation in Missouri G9180 Ð Phosphorus in Missouri Soils G9185 Ð Potassium in Missouri Soils G9804 Ð Nitrate in Soils and Plants MP729 Ð Use of a Portable Chlorophyll Meter to Manage Crop Nitrogen in Rice NCR326 Ð Management of Urea Other publications American Phytopathological Society. Nutrient Deficiencies and Toxicities of Plants CD-ROM. Web address for ordering: http://www.scisoc.org/apspress/ Bennett, William F.1993. Nutrient Deficiencies and Toxicities in Crop Plants. American Phytopathological Society (APS). Web address for ordering: http://www.scisoc.org/apspress/. Mills, Harry A., and J. Benton Jones, Jr. 1996. Plant Analysis Handbook II. Micro- Macro Publishing, Inc. Phone number for ordering: 1-800-500-4635, email for ordering: [email protected]. Potash and Phosphate Institute. 1999. Nutrient Deficiency Symptoms CD-ROM. Phone number for ordering: (770) 447-0335, e-mail for ordering: [email protected]. Issued in furtherance of Cooperative Extension Work Acts of May 8 and June 30, 1914, in cooperation with the United States Department of OUTREACH & EXTENSION Agriculture. Ronald J. Turner, Director, Cooperative Extension, University of Missouri and Lincoln University, Columbia, MO 65211. University UNIVERSITY OF MISSOURI Outreach and Extension does not discriminate on the basis of race, color, national origin, sex, religion, age, disability or status as a Vietnam COLUMBIA era veteran in employment or programs. If you have special needs as addressed by the Americans with Disabilities Act and need this publi- cation in an alternative format, write ADA Officer, Extension and Agricultural Information, 1-98 Agriculture Building, Columbia, MO 65211, or call (573) 882-7216. Reasonable efforts will be made to accommodate your special needs.

IPM1016 New 4/02/5M