Integrated Pest Management

Nutrient Deficienciesand

Application Injuriesin

Field Crops

John SawyerDepartment of Agronomy

IPM 42 Revised July 2004

Nitrogen deficiency in corn

Potassium (K) deficiency is first seen as a yellowingand necrosis of the corn leaf margins, beginning on thelower leaves. Symptoms usually don’t appear for sometime after planting (about 4 to 6 weeks, around the V6growth stage). If the deficiency persists, symptoms

progress up the plantbecause potassium ismobile in the plantand translocates fromold to young leaves.When potassiumdeficiency is severe,older leaves turnyellow with tissuenecrosis along themargins, but the uppernew leaves may remaingreen. Potassium-deficient corn tendsto lodge late in thegrowing season due topoor stalk strength.Potassium deficiencyis favored by conditionsthat limit early rootgrowth, development,and activity – rootpruning, dry soil,compacted soil, seedtrench side-wallsmearing; wet soil;sandy soil; organic soil;strongly geologically-weathered soils;potassium appliedwhere plant rootscannot absorb it; largeamounts of potassium

removed by a preceding crop; and some tillage systemssuch as ridge-tillage and no-tillage, especially in a dryyear and on soil with low levels of subsoil potassium.

Calcium (Ca) deficiency israre in corn. It has not beenverified in Iowa. If deficient,leaf tips stick to the nextlower leaf, creating a ladder-like appearance. Plants maybe severely stunted becausecalcium is immobile in theplant; it is not translocatedfrom old to growing planttissue that needs calcium.Low soil pH and acid soilproblems like excessive levelsof soluble aluminum and

Nutrient deficiencies in corn

Nitrogen (N) deficiency (pictures on front-page)causes pale, yellowish-green corn plants with spindlystalks. Because nitrogen is a mobile nutrient in theplant, symptoms begin on the older, lower leaves andprogress up the plant if the deficiency persists. Symp-toms appear on leaves as a v-shaped yellowing, startingat the tip and progressing down the midrib toward theleaf base. The condition is favored by cold or saturatedsoil; dry soil, particularly after mid-season; largeamounts of low-nitrogen residue; sandy soil; inad-equate fertilization; leaching from heavy rainfall; andflooded or ponded soil when the temperature is warm.

Phosphorus (P)deficiency is usuallyvisible on young cornplants. It readilymobilizes andtranslocates in theplant. Plants are darkgreen with reddish-purplish leaf tips andmargins on olderleaves. Newlyemerging leaves willnot show the colora-tion. Phosphorus-deficient plants aresmaller and growmore slowly than doplants with adequatephosphorus. Defi-ciency symptomsnearly always disap-pear when plantsgrow to three feet ortaller. Some cornhybrids tend to showpurple colors at earlystages of growth eventhough phosphorusnutrition is adequate,yet other hybrids donot show the colorsymptoms even though inadequate phosphorusseverely limits yields. Phosphorus deficiency is favoredby cold soils that are too wet or too dry; phosphorusapplied where plant roots cannot absorb it; restrictedroot growth in compacted soils; and roots injured byinsects, herbicides, fertilizers, or cultivation.

Phosphorus deficiency

Potassium deficiency

Calcium deficiency

manganese are more likely to occur before calciumdeficiency symptoms appear. Calcium deficiency isfavored by very low soil pH, below 5.0 on mineral soilsand 4.8 on organic soils; non-limed, highly weatheredacid soils; or by very high magnesium and potassiumand very low calcium on the cation exchange complex.

Magnesium(Mg) deficiencyis first seen asyellow to whiteinterveinalstriping of thelower cornleaves. Dead,round spotssometimesfollow, whichgive the

impression of beaded streaking. Older leaves becomereddish-purple, and the tips and edges may becomenecrotic if the deficiency is severe. This happens becausemagnesium is mobile in the plant and is translocatedfrom old to new plant tissue. Magnesium deficiency isfavored by very acid, sandy soils in regions of moderateto high rainfall where magnesium has been extensivelyleached from the soil profile. On soils marginal in cropavailable magnesium, deficiency can be induced by highsoil potassium levels or high rates of applied potassium.

Sulfur (S) deficiencyshows on small corn plantsas a general yellowing ofthe foliage, similar tonitrogen deficiency.Yellowing of the youngerupper leaves is morepronounced with sulfurdeficiency than withnitrogen deficiencybecause sulfur is noteasily translocated in theplant.Stuntingof plantsanddelayedmaturityalso aresymp-toms.Interveinalchlorosisof theyoungest

leaves may occur. This deficiency is favored by acidsandy soils; low soil organic matter; and cold - drysoils in the spring that delay the release of sulfur fromorganic matter. Early-season symptoms may disappearas temperature and moisture conditions improve formineralization of sulfur from organic matter, or cornroots reach plant-available sulfate contained within thesoil profile.

Molybdenum (Mo) deficiency (no picture) is rarely, ifever, found in corn. It has not been identified in Iowa.If it occurs, however, older leaves become necrotic atthe tip, along the margins, and between the veins. Thiscondition is favored by very low soil pH and stronglyweathered soils, conditions not normally found in theMidwest.

Boron (B) deficiency (no picture) is rare in corn. It hasnot been verified in Iowa. Leaves have small dead spotsand are brittle. Boron is not readily translocated in theplant and as a result upper internodes do not elongate.Tassels and ear shoots are reduced and may not emerge.Corn is very sensitive to boron fertilizer. Boron toxicitycan result if fertilizer is applied at rates above recom-mendations, or row applied. Deficiency is favored bydrought; sandy soils that are low in organic matter; andhigh soil pH. Drought reduces the release of boronfrom organic matter, but lack of water also delays earshoot emergence and possible pollination; therefore,symptoms may occur simultaneously and could beconfused with each other.

Copper (Cu) deficiency (no picture) is rare in corn. Ithas not been verified in Iowa. The youngest leaves areyellow as they come out of the whorl, and the tips maydie. Copper is relatively immobile in the plant. Leavesbecome streaked, causing an appearance that is similarto iron deficiency. The stalk is soft and limp. Somenecrosis of older leaf edges occurs as it does in cases ofpotassium deficiency. Copper deficiency is favored byorganic soils (very high soil organic matter) and byhigh soil pH (above7.5).

Iron (Fe) deficiencyturns the interveinalarea along the length ofthe upper leaves palegreen to nearly white.It has not been verifiedin Iowa. Iron is immo-bile and is not translo-cated from old toyoung plant tissue.This deficiency is rareon corn because of itslow iron requirement,

Magnesium deficiency

Iron deficiencySulfur deficiency

and it only occurs on high pH soils. Iron deficiency isfavored by calcareous soils with a high soil pH in thesurface soil and by cold, wet, poorly aerated soils.

Manganese (Mn)deficiency symptoms arenot clear-cut. It has notbeen verified on corn inIowa. Newly emergedleaves become olive-green and may becomeslightly streaked. If thecondition is severe,deficient leaves becomeelongated with whitestreaks that turn brownin the center, deteriorateand fall out. Manganeseis relatively immobile inthe plant. Manganesedeficiency is favored byhigh soil pH; sandy soilsthat are high in organicmatter, and peat ormuck soils.

Zinc (Zn) deficiencyin corn causesinterveinal, lightstriping or a whitishband beginning atthe base of the leafand extendingtowards the tip. Themargins of the leaf,the midrib area, andthe leaf tip usuallyremain green. Plantsare stunted becauseinternodes areshortened. Zinc isrelatively immobilein the plant. Severezinc deficiency mayresult in new leavesthat are nearly white,an effect termed“white bud.” Plants

frequently outgrow zinc deficiency unless it is severe.Zinc deficiency is favored by high soil pH; low organicmatter soils with high soil pH; cool, wet soil; and highphosphorus fertilizer applications on soils that aremarginal in zinc availability, although high soil phos-phorus levels alone don’t create zinc deficiency.

Fertilizer injury to cornand soybean

Anhydrous ammonia (NH3) vapor damage to leaves

can occur when sidedressing ammonia if the applicatorknives arenear orabove thesoil surfaceand there isescape ofammoniaduringapplication.Corn plantsusuallyoutgrow thedamage ifonly aportion ofthe leaves isdamaged.

Non-pressure nitrogen solutions (urea-ammoniumnitrate solution, 28 or 32% UAN) broadcast on top ofgrowing corn can burn leaf tissue. The solutions tendto move towards the leaf tip and margins, resulting ingreater burning of those leaf areas. Corn plants usuallyoutgrow the damage if only a portion of the leaves isinjured. However, leaf damage and potential yield

impactsincrease withhigherapplicationrates andlarger plants.

Manganese deficiency

Zinc deficiency

Anhydrous ammonia vapor damage

Broadcast solution nitrogen

Non-pressure nitrogen solutions (urea-ammoniumnitrate solution, 28 or 32% UAN) broadcast on top ofgrowing soybean can burn leaf tissue. Application evenat low rates can cause tissue damage. Soybean plantsusually outgrow the damage if only a portion of theleaves is injured.

Broadcast nitrogen solution

Granular urea applied on top of growing cornresults in some granules falling in the whorland lodging in leaf axils. Tan to white burnspots and damaged tissue areas appear onleaves where granules lodge. Plants absorb urea

Anhydrous ammonia injury results in uneven cornseedling emergence, slow plant growth, plants with a

spiked and blue-green color appear-ance, and wilting ofseedlings in dryweather. Ammoniainjury is detectedmore frequently indry weather becauseroots are slow todevelop; if a portion

of the root system isdestroyed, it limitswater uptake. Rootinjury browns theroots. If severelyinjured, roots dieand turn black backto the seed.

Anhydrous ammoniainjury

Seed-placed urea stand lossand biuret damage

Granular urea

through their leaves. If the amount of ureaabsorbed is excessive, the leaf margins turnwhite. Although this is a symptom of toxicity,plants outgrow the injury unless a largeamount of material lodges in the whorl andthe plant leaves are severely damaged or thegrowing point is injured.

Urea containing fertilizers when row banded with ornear corn seed can result in uneven corn seedlingemergence, stand loss, slow growth, and damagedroots as free ammonia is released during urea conver-sion to ammonium. Also, biuret in urea can causemisshapen plants or leaves that don’t unroll.

Nutrient deficiency in soybean

Potassium (K) deficiencyyellows soybean leaves,beginning at the marginsand moving inward overthe leaf. Deficiency symp-toms occur on olderlower leaves first. All butthe newest emerged leavesmay show potassiumdeficiency symptoms insevere cases.

Iron (Fe) deficiencyof soybean is usuallyidentified on youngplants. Because iron isimmobile in the plant,the deficiency symp-toms occur on theyoungest upperleaves. The leaves turnyellow, but the veinsremain green. Irondeficiency occurs onhigh pH soils andfrequently occurs onthe calcareous soils ofcentral and northcentral Iowa.

Molybdenum (Mo) deficiency results in light greensoybean plants. This indicates nitrogen deficiencybecause molybdenum is essential for the symbioticnitrogen-fixation process. Molybdenum deficiency ofsoybean only occurs on very acid, highly weatheredsoils and has not been seen in Iowa.

Potassium deficiency

Iron deficiency

Nutrient deficiency in alfalfa

Molybdenum (Mo)deficiency reduces thegrowth of alfalfa. Deficientplants tend to be pale orlight green becausemolybdenum is essential forthe nitrogen-fixation process.Molybdenum deficiency inalfalfa usually occurs only onvery acid soils. It has notbeen verified in Iowa.

Potassium (K) deficiency creates small dots on themargins of the upper leaflets of alfalfa. When severelydeficient, the size and number of spots increase, theleaves become yellow and dry, and the lower leavesdrop.

Molybdenum deficiency

Molybdenumdeficiency

Potassium deficiency

Phosphorus (P)deficiency resultsin reduced earlyplant growth andtiller development,which gives theimpression of athin stand. Plantsremain green butolder leaves havereddish-purplishleaf tips andmargins. Newlyemerging leaves donot show thecoloration. Phos-phorus-deficientplants are smallerand grow moreslowly than doplants with ad-equate phospho-rus.

Potassium (K)deficiency appears asa yellowing andnecrosis of the leaftip and margins,beginning on thelower leaves. If thedeficiency persists,symptoms progressup the plant aspotassium is mobilein the plant andtranslocates from oldto young leaves.

Boron (B) deficiency on alfalfa shortens the internodesnear the plant top, resulting in a bunching or bushyappearance of the upper plant. The top (new) leavesturn yellow and may have a reddish purple-pink

coloration on the leaflet margins. This causes thedeficiency to be mistaken for leafhopper injury. Lowerleaves remain green. Boron deficiency usually occurswhen weather is dry and on soils that are low inorganic matter.

Boron deficiency

Nutrient deficiency in winterwheat

Nitrogen (N) deficiency appears as a general paleyellowish-green plant with slow growth and reducedtiller development. If the deficiency persists, plantsremain pale green, have reduced growth, and the standappears thin.

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Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, incooperation with the U.S. Department of Agriculture. Stanley R. Johnson, director,Cooperative Extension Service, Iowa State University of Science and Technology, Ames,Iowa.

File: Agronomy 8-2

Nitrogen deficiency

Potassium deficiency

Phosphorus deficiency

Diagnosis

Potassium deficiencyNot chiseled (left), chiseled (right)

Iron deficiency in soybeanZinc deficiency in corn

Potassium deficiency in corn, lower leaves Iron deficiency in soybean, upper leaves

Nitrogen skip pattern in corn

Symptoms caused by nutrients mobile in theplant occur on the lower, older leaves.

Symptoms caused by nutrients immobile in theplant occur on the upper, younger leaves.

Symptoms that occur in a regular geometrical pattern are most likely due to cultural practices.

Nutrient deficiency symptoms occur as yellowing of leaves, interveinal yellowing of leaves, shortenedinternodes, or abnormal coloration such as red, purple, or bronze leaves. These symptoms appear on

different plant parts as a result of nutrient mobility in the plant.

Nutrient deficiency symptoms that occur in irregular patterns in a field are probably due to a soil condition.

Diagnosing nutrient deficiency symptoms is most reliable when all factors otherthan the nutrient in question favor normal growth and when the symptoms occur

on several plants in an area following a specific soil or management pattern. Comparison of plants in affectedand non-affected field areas, as well as other information like soil tests and cultural practices, can helpdetermine specific causative factors.