~ 18 elements have been identified as essential for the growth of all plants Soil C O H N K Ca Mg P S Cl Fe Mn Zn B Cu Mo air & water macronutrients micronutrients 0.1% V Ni Needed by some plants Si Co Na

N = 100 http://web.missouri.edu/~umcsnrsoilwww/webpub05/micro1_2005rev.htm

Some elements (e.g. Se, I, As, Cr) have been identified as essential for animals but not for plants. Boron is the only element that has been identified as essential for plants but not for animals

Inorganic nutrient forms taken up by plants Co2+

Micronutrients have very important roles in plant metabolism

Classic concept of yield response to nutrient availability …… Macronutrients tend to have a broad sufficiency range Micronutrients tend to have a narrow sufficiency range Crop yield Nutrient availability

Negative interactions Micronutrient deficiency symptoms tend to show up on new leaves Nutrients used in abundance tend to be easily moved around Negative interactions

6.5 7.5

Suggested soil test levels for selected micronutrients in IL   SOIL TEST LEVEL (LB/ACRE) MICRONUTRIENT AND PROCEDURE VERY LOW LOW ADEQUATE Boron (alfalfa only) hot water soluble 0.5 1.0 2.0 Iron (DTPA) -- <4 >4 Manganese (DTPA) <2 >2 Manganese (H3PO4) <10 >10 Zinc (0.1N HCl) <7 >7 Zinc (DTPA) <1 >1

Unfortunately soil tests for micronutrients have limited value sampling and soil test methods are less reliable calibration databases are inadequate Plant tissue levels of micronutrients often provide a better indication of micronutrient needs than soil test results

Critical tissue nutrient levels for corn, soybeans and alfalfa Lower nutrient levels in designated plant tissue indicates that nutrient deficiency is likely. http://iah.aces.uiuc.edu/pdf/Agronomy_HB/11chapter.pdf

Micronutrients deficiencies are normally associated with one or more of the following five situations: highly weathered soils coarse-textured soils high-pH soils Organic/muck soils soils that are low in organic matter because erosion or land-shaping processes have removed the topsoil. If one or of these situations applies and soil test levels and/or plant tissue levels are low, evaluation of micronutrient fertilizers is recommended.

Boron (B) deficiency is a common occurrence on alfalfa in IL Boron (B) deficiency is a common occurrence on alfalfa in IL. Characteristic symptoms of the deficiency are yellowing of the upper leaves, eventually turning to a purpling color, along with stunting of the upper stems. Deficiency symptoms for B are similar to leaf hopper damage. Deficiency symptoms are most commonly observed during drought conditions. If B deficiency has previously been observed, it will likely occur whenever alfalfa is grown in that field unless B is applied on an annual basis.

Boron fertilization in IL On sandy soils, apply 1 lb of boron per acre after the first cutting of alfalfa each year. On heavier soils, 3-4 lb/acre after the first cutting (yr 1) is normally adequate for the life of the stand. Boron should not be applied to the alfalfa seedbed as it can damage germinating seeds and should not be applied to alfalfa the year proceeding corn. Low soil test levels of B are a good indicator that alfalfa will respond to fertilization with B, but field scouting for deficiency symptoms may be just as informative. Correlation between soil test levels of B and corn or soybean response to B is low. According to the U of I, there are no confirmed B deficiencies on either corn or soybean in Illinois.

Adequate boron nutrition is critical for high quality vegetable crops Foliar application of Boron Crops with high demand for boron may benefit from foliar applications of boron (~ 0.2 lbs B/acre) at the following times: prior to heading of cole crops, prior to root swell in root crops, and at first bloom for tomatoes and okra. NCDA recommendations for Boron: all brassicas: 2 lbs per acre cantaloupes & cukes: 1 lb per acre peppers and tomatoes: 1 lb per acre okra: 0.5 lbs per acre Adequate boron nutrition is critical for high quality vegetable crops

Manganese deficiency (stunted plants with green veins in yellow or whitish leaves) is common on high pH (alkaline) sandy soils, especially during cool, wet weather in late May and June. Suggested treatment is to spray either manganese sulfate or a manganese chelate complex onto the leaves soon after the symptoms first appear. Broadcast soil applications of Mn are often ineffective because the Mn becomes unavailable.

Foliar application of MnEDTA at rates as low as 0 Foliar application of MnEDTA at rates as low as 0.15 pound Mn per acre in mid-June to beans planted in early May has resulted in significant yield increases in IL. Delaying application until early July has sometimes provided a slightly higher yield response than mid-June applications. Multiple applications may be necessary to optimize yield.

Are Roundup Ready™ Soybeans more likely to experience Mn deficiency ? There is a growing body of evidence that RR soybeans are more likely to experience Mn deficiency than non-RR soybeans. Researchers at Purdue University have attributed this to less effective Mn utilization within RR beans and interference with Mn uptake.

Impact of glyphosate on Mn transforming microorganisms

Impact of glyphosate on fusarium colonization of soybean roots

Far reaching effects of glyphosate on soil chemistry and ecology

Impact of low levels of glyphosate on metal micronutrient concentrations in “non target” plants *

A recent study at the U of I found that the amount of "flash" following glyphosate application increased with glyphosate rate, but that foliar application of Mn had no impact on the amount of "flash", leaf Mn content, or crop yield. It is likely that glyphosate effects on yield related to Mn immobilization only occur when Mn levels are approaching deficiency.

Summary of recent research

Caution should be taken when mixing Mn and other micronutrients with glyphosate. Dry flowable products show the most antagonism, while chelates show the least. Antagonism may result in reduced weed control. It has also been reported that glyphosate inhibits the uptake of Mn applied to plant foliage prior to, with, and for up to eight days after glyphosate application.

Soybeans normally outgrow the stunted, yellow appearance of Fe chlorosis. As a result, it has been difficult to measure yield losses or decide whether or how to treat affected areas. Research in Minnesota has shown that timing of Fe application is critical to attaining a response. Researchers recommend that 0.15 lb/acre of iron as iron chelate be applied to foliage within 3 to 7 days after chlorosis symptoms develop (usually in the second-trifoliate stage of growth). Waiting for soybeans to grow to the fourth- or fifth-trifoliate stage before applying iron resulted in no yield increase.

There is no reliable soil test for Cl in Illinois. Chloride According to the U of I, chloride (Cl) deficiency has not and is likely to be observed in IL. The Cl requirement is much less than that of K, and each time that K is applied as 0-0-60, there is as much Cl applied as K. Chloride deficiency of wheat has been observed in states where potassium deficiency is rare (and thus 0-0-60) is not normally applied. There is no reliable soil test for Cl in Illinois.

Copper Copper (Cu) deficiency is rare in the U.S. and has not been observed in Illinois. Sweet corn and wheat are two of the crops most sensitive to Cu deficiency. Limited reports of the deficiency have been reported in Michigan and Wisconsin on high organic matter soils (mucks and peats).

Molybdenum Molybdenum (Mo) differs from most of the other micronutrients in that it increases in availability with an increase in pH. The deficiency is limited almost exclusively to legumes, including soybeans grown on very acidic soils (pH< 5.0). In nearly all cases, it is more economical to apply limestone to correct the problem than to apply Mo. However, if you must grow soybeans on very acidic soils, be sure to use a seed treatment that includes molybdenum. Soil pH is the only soil test that detects the potential for Mo deficiency.

Zinc Zinc (Zn) deficiency, while not common in IL, is much more likely to occur on corn than on soybean. Documented response to Zn has been limited to low organic matter soils and sandy soils in northwestern Illinois. High pH (greater than 7.3) and very high P levels increase the likelihood of Zn deficiency. If high P levels have resulted from manure applications, Zn deficiency is unlikely. Soil test levels of Zn are poor indicators of yield response to the application of Zn.

Zinc deficiency in corn is exhibited on the upper leaves as interveinal chlorosis. The veins, midrib and leaf margin remain green. As the deficiency intensifies “feather like” bands develop on either side of the midrib and the leaves may turn almost white (hence the term “white bud” was coined to describe Zn deficient corn plants); internodes are short resulting in stunted plants. http://www.cropsoil.uga.edu/~oplank/diagnostics70/Symptoms_/Corn/Images-Corn/images-corn.html

Summary None of the micronutrient soil tests are very reliable for predicting crop response to fertilization. If soil test levels are high, the likelihood of response to fertilization is very low. If soil test levels are low to medium, the potential for response to the applied element may be high, or it may be low. Decisions about micronutrient fertilization should take into account the sensitivity of the crop to be grown, soil characteristics that affect the availability of the element, such as soil pH, organic matter, soil texture, and soil P level, soil test levels and tissue test levels. If multiple factors indicate potential for deficiency, fertilization on a trial basis is probably a good risk.

Metal-EDTA complex

Micronutrients can be blended with macronutrient fertilizers Segregation is likely to occur if granules are not all the same size

Mn, B and Cl help crops to resist fungal pathogens Chloride (Cl), usually in the form of potassium chloride (KCl), has been shown to reduce the severity of some fungal diseases. Adequate Mn nutrition reduces the incidence of foliar disease in most crops. Mn is needed for the synthesis of lignin and phenols, compounds used by plants to combat infection by pathogens. Boron (B) deficiency has been linked to the production of small fissures and cracks that may be the initial entrances for fungal pathogens.

Micronutrient Malnutrition Affects nearly half the world’s population More than 840 million people cannot meet their basic daily food and nutritional needs About 2 billion people, mostly women and children, are at risk from diseases, premature death, and lower quality of life linked to deficiencies of vitamin A, iodine, and iron

Global Prevalence of Iron, Vitamin A and Iodine Deficiencies Source: USAID

HarvestPlus: NOT a silver bullet, but an additional weapon to fight deficiency Biofortification Supplementation Commercial Fortification Dietary Diversity

Biofortification Useful genetic variation exists in key crops Breeding programs can enhance nutritional quality traits, which for some crops are highly heritable and simple to screen for Desired traits should be stable across a wide range of growing environments Nutritional quality traits should be combined with superior agronomic characteristics (e.g., higher yields)