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Micronutrient Needs for Crops on the Southern Plains. Dave Mengel Professor of Soil Fertility Kansas State University. The Essential Elements. Carbon, Oxygen, Hydrogen Macronutrients N, P, K Secondary Nutrients Ca, Mg, S Micronutrient metals Fe, Zn, Mn, Cu, Ni Other micronutrients

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micronutrient needs for crops on the southern plains

Micronutrient Needs for Crops on the Southern Plains

Dave Mengel

Professor of Soil Fertility

Kansas State University

the essential elements
The Essential Elements
  • Carbon, Oxygen, Hydrogen
  • Macronutrients
    • N, P, K
  • Secondary Nutrients
    • Ca, Mg, S
  • Micronutrient metals
    • Fe, Zn, Mn, Cu, Ni
  • Other micronutrients
    • Cl, B, Mo
micronutrient metals
Micronutrient Metals
  • Of the five micronutrient metals:
    • Zinc deficiency is common on corn and grain sorghum
    • Iron deficiency is common on corn, grain sorghum and soybeans
    • Manganese deficiency is not common in the region, but is of interest due to reports of Manganese x glyphosate interactions in RR soybeans
micronutrient metals1
Micronutrient Metals
  • Of the five micronutrient metals:
    • Copper is not a problem in the region, but recently “foreign experts” have been raising questions concerning potential Cu deficiencies in wheat.
    • Nickel is of academic interest only at this time.
  • Zinc: the most common micronutrient deficiency of corn in the region
  • Deficiencies also are seen in sorghum, soybeans and pecans.
  • Deficiencies in wheat and sunflowers are rare.
  • A cofactor in many enzyme processes in plants, the exact role of the zinc in these reactions is generally not known.
  • Zinc is generally immobile in the plant, and deficiency is commonly noted on the young tissue.
  • Multiple symptoms have been described for zinc deficiency, with some genotypes responding differently.
    • In corn a stunting, yellowing at the whorl and intervienal striping is common.
    • A stunting or rosetting and internode shortening of young seedlings with distinct white band on one side of the mid-rib is also common.
where zinc deficiency is seen
Where Zinc Deficiency is Seen
  • Zinc is low in many soils across the region, and especially in areas of high pH, and where organic matter has been removed, such as eroded areas or land leveled fields.
assessing zinc deficiency
Assessing Zinc Deficiency
  • The DTPA Soil Test is commonly used for zinc
    • The critical level ranges from 0.5 to 1 ppm Zn for most crops
    • Levels 0-0.5 considered strongly deficient
    • Applications are roughly 1 lb Zn per 0.1 ppm below the critical level
correcting zinc deficiency
Correcting Zinc Deficiency
  • Application of zinc can be by:
    • Broadcast applications of a high percentage water soluble zinc source, such as zinc sulfate, oxysulfate or zinc chelate.
    • Band application of these same products with starter fertilizers.
    • Foliar application of zinc, especially on pecans and rice.
    • Application of animal manure. Most manure contains large amounts of zinc
iron in plants
Iron in Plants
  • Iron deficiency in field crops is common, especially on corn, soybeans, and sorghum. It is less common on wheat, but does occur.
  • Iron is the most common micronutrient deficiency of turgrass and ornamentals in Kansas. Iron chlorosis occurs frequently on lawns in new developments or on golf greens built with unwashed river sand.
  • Considerable difference exists between varieties in all crops. Corn and soybean varieties are screened for iron chlorosis.
  • Iron is a structural component of cytochromes, hemes and other substances involved in oxidation-reduction reactions in photosynthesis and respiration.
iron deficiency symptoms
Iron Deficiency Symptoms
  • Iron is very immobile in plants, once deposited in tissue, iron is not easily remobilized to younger tissue.
  • Deficiency symptoms are generally found in the youngest leaves on the plant.
  • Young leaves develop an intervienal chlorosis that rapidly progresses over the entire leaf. This may include a bleaching of the veins and in severe cases the entire leaves will turn white.
where does fe chlorosis occur
Where Does Fe Chlorosis Occur?
  • On high pH depressional soils
  • Most commonly found in “spots” in the field
  • In eroded spots or leveled areas .
assessing iron deficiency
Assessing Iron Deficiency
  • The DTPA test is sometimes used, but it is not reliable
  • pH and OM may be better indicators
correcting iron deficiency
Correcting Iron Deficiency
  • Foliar applications of 2% ferrous sulfate
    • May take multiple applications
  • Band applications of 6-10 pounds soluble iron
  • Animal manure
  • Lowering pH works in home hort or turf, but too expensive for field applications
manganese in the plant
Manganese in the Plant
  • Manganese is involved in photosynthesis, particularly in the evolution of O2.
  • It also is involved in a number of oxidation-reduction reactions and in decarboxiliation and hydrolysis reactions.
  • In many plant reactions Mn and Mg can partially substitute for each other.
  • May be a relationship with the RR gene in soybeans causing Mn deficiency
manganese deficiency symptoms
Manganese Deficiency Symptoms
  • Like iron, Mn is very immobile in the plant and deficiency symptoms occur as intevienal chlorosis on young leaves.
  • Manganese deficient leaves tend to maintain a greenish tint, unlike iron chlorosis where they turn yellow or bronze.
  • Manganese deficiency is not common in the region, but occurs on high pH, high organic matter soils, found in the eastern cornbelt.
mn and rr soybeans
Mn and RR Soybeans
  • Speculation that the RR gene has added a sensitivity to Mn deficiency. Reports and research in Indiana and Kansas.
  • The yellow flashing which occurs after glyphosate application in some fields has been called Mn deficiency.
  • Research with RR isolines suggest this could be the case, but likley on marginal Mn sites.
assessing mn deficiency
Assessing Mn Deficiency
  • Mn Soil Tests Don’t Work
  • pH and OM may be useful in deficient regions (eastern US)
correcting mn deficiency
Correcting Mn Deficiency
  • Like iron, the soil contains large amounts on Mn, its an availability issue.
  • Foliar application
  • Band application
  • Band apply an acid forming fertilizer (N)
where is copper deficiency found
Where is Copper Deficiency Found?
  • Deficiency is not found in the Southern Plains. It looks similar to drought or heat damage on wheat and has been some confusion recently
  • It is common on organic soils in Canada and the Great Lakes region, and on organic soils or deep acid sands in the southeastern US, which have never received applications of copper as a fertilizer or as a fungicide.
  • On extremely weathered oxisols or sands in tropical regions and Australia.
copper in plants
Copper in Plants
  • Copper is involved in many complex enzyme systems where redox potential is critical. Examples include the enzymes involved in lignin and melanin production.
copper deficiency symptoms
Copper Deficiency Symptoms
  • Corn and wheat are the two commonly grown field crops most likely to be deficient in copper.
  • Like most metals, copper is not very mobile in the plant, with deficiency symptoms occurring on the younger tissue.
  • Copper deficiency results in a unique necrosis and twisting of the leaf tips of young seedlings. Copper is bound very strongly by soil organic matter..
correcting copper deficiency
Correcting Copper Deficiency
  • Broadcast applications of 5 pounds Cu, 20 pounds Copper sulfate per acre. Good residual effects.
  • Foliar applications of 1-2 pounds Copper sulfate per acre.
  • Recently confirmed as an essential element.
  • Only one field deficiency ever found.
  • Primarily of academic interest.
micronutrient non metals
Micronutrient: Non-metals
  • Of the three non-metals:
    • Boron deficiency occurs rarely on alfalfa in SE KS and Oklahoma and on peanuts in OK
    • Old research found Mo deficiencies on soybeans in SE KS
    • Recent reports suggest Mo deficiency may occur on soybeans in Central Kansas also.
    • Chloride response occurs frequently on wheat, sorghum and corn in NE and Central KS where no potash has been applied.
boron deficiency
Boron Deficiency
  • Since B is involved in cell division, deficiency symptoms are cessation of growth at the terminal bud, followed by yellowing and death of young leaves.
  • Severely impaired fruit and seed set are late season symptoms on many crops.
  • Boron deficiency is commonly confused with potato leaf hopper damage in alfalfa
where boron deficiency is seen
Where Boron Deficiency is Seen
  • In Kansas, boron deficiency is occasionally seen on alfalfa, primarily in SE Kansas.
  • There have been reports of boron response in corn and sunflower in Nebraska, cotton in Missouri, and peanut in Oklahoma.
assessing boron deficiency
Assessing Boron Deficiency
  • A hot water soluble soil test is sometimes used for boron. However it is not well correlated with plant growth, so is not recommended.
  • Plant analysis is the preferred diagnostic method.
  • Since B deficiency is easily confused with leafhopper damage, and B toxicity can be a problem, care should be used when applying boron
correcting boron deficiency
Correcting Boron Deficiency
  • Boron is highly toxic to germinating seeds of corn and soybeans. Boron fertilizers should never be applied as a "starter fertilizer" in or near the row at planting time..
  • Application of boron can be by:
    • Broadcast applications of 1-2 pounds of B as granular borate.
    • Foliar application of 0.1-0.5 pounds soluble borate.
  • Chlorine has been generally accepted as an essential element since 1954.
  • Responses to chloride fertilization have been reported since the 1800’s.
  • Chloride plays many roles in plant nutrition, but role in disease suppression, especially leaf rust in wheat and stalk rot in sorghum and corn, sparked interest in chloride in Kansas.
  • Yield responses to potash on high K soils also sparked interest in other states in the plains.
chloride fertilization of wheat in kansas
Chloride Fertilization of Wheat in Kansas
  • Some of the first chloride work reported in Kansas was done in the early to mid 1980’s by Larry Bonczkowski comparing KCl to fungicides on leaf rust suppression.
  • Mark Hooker at Garden City, and Ray Lamond in Manhattan followed that up with work on yield response to chloride on wheat in the mid-80’s.
  • Ray Lamond also screened wheat varieties for differences in response/sensitivity to chloride.


Chloride applied Grain Yield Percent Chloride

lbs Cl-/acre bu/A in leaf at boot


0 48.4 b 0.29 c

10 51.7 a 0.38 b

20 52.5 a 0.43 a

LSD 0.05 1.3 0.03

n 34 30


sorghum 1996 to date
Sorghum: 1996 to date
  • Unlike wheat, no visual chloride deficiency symptoms have been described on sorghum.
  • There appears to be a relationship in sorghum between chloride nutrition and stalk quality.
  • The first chloride studies on sorghum were conducted by Lamond in 1996.
  • 23 chloride response trials on dryland sorghum have been reported, by several people, primarily in central Kansas.
Response of dryland grain sorghum to applied

chloride fertilizer in Kansas, 1996-2006.


Chloride applied Grain Yield Percent Chloride in leaf

lb Cl-/acre Bu/A at boot, percent ________________________________________________________

0 98.5 b 0.10 c

20 108.2 a 0.24 b

40 109.9 a 0.33 c

LSD 0.05 2.4 0.05

n 20 11


corn 1996 to 2001
Corn: 1996 to 2001
  • Like sorghum, no visual chloride deficiency symptoms have been described on corn.
  • There appears to be a relationship in corn between chloride nutrition and stalk quality.
  • The first chloride studies on corn were conducted by Lamond in 1996.
  • Only 11 chloride response trials on dryland corn have been reported, all in central Kansas.
Response of dryland corn to applied chloride

fertilizer in Kansas, 1990-2001.


Chloride applied Grain Yield Percent Chloride

lb Cl-/acre Bu/A in earleaf at tassel


0 104.4 b 0.17 c

20 108.9 a 0.27 b

40 111.6 a 0.36 c

LSD 0.05 3.4 0.05

n 11 11


Soil test chloride interpretations and fertilizer

recommendations for Kansas.


Soil Chloride in a 0-24" sample Cl Recommended*

Category lb/acre ppm lb/acre


Low <30 <4 20

Medium 30-45 4-6 10

High > 45 >6 0


*Recommendations for corn, sorghum and wheat only.

molybdenum in plants
Molybdenum in Plants
  • Molybdenum is involved in the nitrate reductase and nitrogenase systems in plants.
  • Plants require very low levels of Mo. In legumes, enough molybdenum can be present in the seed to meet the needs of the plant. But subsequent generations may need additional molybdenum.
molybdenum deficiency symptoms
Molybdenum Deficiency Symptoms
  • Molybdenum deficient plants appear stunted, light green and N deficient.
where does molybdenum deficiency occur
Where Does Molybdenum Deficiency Occur?
  • On low pH, weathered soils in SE and SC Kansas. Molybdenum deficiency is not common in Kansas, but occurs most frequently on old, highly weathered acid soils.
  • Recent reports suggest low molybdenum in seed may be contributing to Mo deficiencies under high pH.
assessing molybdenum deficiency
Assessing Molybdenum Deficiency
  • No reliable soil test is currently available.
  • Soil pH and seed molybdenum may be better indicators of molybdenum needs.
  • Plant analysis is a good diagnostic tool.
correcting molybdenum deficiency
Correcting Molybdenum Deficiency
  • Liming
  • Seed treatment with 1-2 ounces of ammonium molybdate.
  • Foliar applications of ammonium molybdate of 2-4ounces per acre.
  • Due to the toxic nature of molybdenum to ruminant animals, molybdenum fertilization is normally not recommended.