Posts Tagged ‘micronutrient deficiency’

Boron Deficiencies in Cole Crops

Friday, September 7th, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Long time growers of cole crops know that the micronutrient boron is critical for production. However, newer growers may be unaware of these requirements. Boron is also subject to leaching with rainfall, particularly in our sandy soils, so available soil boron declines over time.

Cole crops have a moderate to high boron requirement. Symptoms of boron deficiency vary with crop type. Most boron deficient cole crops develop cracked and corky stems, petioles and midribs. The stems of broccoli, cabbage and cauliflower can be hollow and are sometimes discolored. Cauliflower curds become brown and leaves may roll and curl, while cabbage heads may be small and yellow. Of all the cole crops, cauliflower is the most sensitive to boron deficiencies.

It is recommended in broccoli and kale to apply 1.5-3 pounds of boron (B) per acre in mixed fertilizer prior to planting. In Brussels sprouts, cabbage, collards and cauliflower, boron and molybdenum are recommended. Apply 1.5-3 pounds of boron (B) per acre and 0.2 pound molybdenum (Mo) applied as 0.5 pound sodium molybdate per acre with broadcast fertilizer.

Boron may also be applied as a foliar treatment to cole crops if soil applications were not made. The recommended rate is 0.2-0.3 lb/acre of actual boron (1.0 to 1.5 lbs of Solubor 20.5%) in sufficient water (30 or more gallons) for coverage. Apply foliar boron prior to heading of cole crops.

Other fall crops such as beets, radishes, and turnips are also susceptible to boron deficiencies in sandy soils with limited boron fertilizer additions.

Sulfur Deficiency in Corn

Friday, June 1st, 2012

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

After visiting a great many fields over the past few days, I came to the conclusion that our efforts in controlling air pollution and especially sulfur (S) emissions have been very successful, perhaps too successful. The number of corn fields that are showing areas that of yellowing plants likely due to S deficiency is as great as or greater than I can ever remember seeing. I’m seeing plants with both the traditional S deficiency we all learned about in school where the plant shows a general chlorosis and stunting (Photo 1) and interveinal chlorosis that has been the hallmark of S deficiency in the past few years (Photo 2). Although many agronomists in the area were unsure of the interveinal chlorosis symptomology when it first appeared, Dr. Greg Binford did a few fertilization studies that seemed to confirm that S was responsible for the symptoms or at least could eliminate the symptoms.

Photo 1. More traditional sulfur deficiency symptom on corn with general chlorosis of the leaves and stunting of the plant which was about half the size of less affected plants.

Photo 2. Less traditional sulfur deficiency symptom on corn with severe interveinal chlorosis of the leaves along with stunting of the plant.

Many growers are already taking steps to reduce the impact of the ‘cleaner air’ by adding some ammonium sulfate to the corn starter fertilizer or to their sidedressed nitrogen (N). In Dr. Binford’s field trials, he did get a yield increase when S fertilizer was added; although in studies a number of years ago, I didn’t find a yield response to added broadcast S fertilizer. In many cases as the corn root system continues development, it is able to pick up S from the deeper soil layers and the deficiency symptoms disappear on their own accord. Another complication in the story is that we have changed from using the old superphosphate fertilizer (rock phosphate treated with sulfuric acid to make a 0-20-0 fertilizer) to new formulations, MAP, DAP and ammonium polyphosphates. This change has reduced the amount of S we were adding to our soils without consciously realizing it. I think as we go forward more and more growers will be using ammonium sulfate at some point in their cropping rotations to add needed sulfur to the topsoil.

You should keep in mind that S is either in an anion (negatively charged ion) form (SO42-) or is rapidly converted in warm, moist soil to the anion sulfate form. Anions such as sulfate and nitrate are subject to leaching loss from the topsoil. Dr. Tom Sims did find large quantities of sulfate in the deep subsoil layers of even the sandy soils in Sussex County, Delaware but the corn and other crops are not able to obtain S from these layers until much later in the growing season when the root system is nearly fully established. Early in the season, we are likely to find more and more fields showing S deficiency unless S fertilizer is regularly applied to the crops.

Manganese Deficiency on Corn as Related to Soil Organic Matter

Friday, June 24th, 2011

Richard Taylor, Extension Agronomist; rtaylor@udel.edu and Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu

In past articles, we’ve talked about finding manganese (Mn) deficiency in small grains (this spring) and soybeans (last year) but in the past week or two we’ve found the problem in some corn fields as well. Symptoms of Mn deficiency in corn include stunting (Photo 1) and the typical interveinal chlorosis in which the veins remain green and the tissue between veins turns light yellow (Photo 2). Photo 3 and 4 show the field where the deficiency occurred with the good areas in the far distance. It should also be noted that the corn was drought stressed as well.

Photo 1. Manganese deficient corn plants (right) compared with normal corn (left)

Photo 2. Typical interveinal chlorosis caused by manganese deficiency in corn

Photo 3. Field view of Mn deficiency on corn

Photo 4. Field view of Mn deficiency with normal corn in the upper left corner near the woods

For this field, there was a significant difference in the soil organic matter content between the affected areas (2.9%) and the healthier areas (8.9%) (Table 1). Tissue testing of the affected corn plants (Table 2) showed that Mn was deficient while all the other nutrients were either in the sufficient range or higher than the sufficient range. This raised some interesting questions. The good corn soil sample actually contained a lower concentration of manganese than the bad corn soil sample and the soil water pH and percent hydrogen saturation of the soil sample from the good areas showed a greater amount of soil acidity than for the soil sample from the bad areas. The very high organic matter content of the good sample allowed corn growth at the low soil pH (4.9) and the chelating compounds available from the large amount of organic matter helped the plants obtain enough Mn for normal growth. In the lower organic matter areas, Mn availability suffered and was not overcome by the higher level of soil test Mn.

Table 1. Soil Test Results Including (*) Percent Base Saturation for Good and Bad Corn Areas

  Good Corn Bad Corn
Soil pH 1:1 4.9 6
Buffer pH 6.3 6.8
Organic Matter % 8.9 2.9
U of D P Sat Ratio 12 32
Mehlich 3 Phosphorus ppm P/FIV 54 126
K ppm 229 161
Ca ppm 1340 1480
Mg ppm 191 191
SO4-S ppm 41 31
Zn ppm 3.52 3.8
Mn ppm 2 4.4
B ppm 0.98 0.98
CEC meq/100 g soil 16.1 11
H* 45 15
K* 4 4
Ca* 41 67
Mg* 10 14
Na* 0 0

* Base saturation for each of the cations is given in percent of CEC occupied by that cation.

Table 2. Tissue Sample Results for Manganese Deficient Corn Plants

Corn Sample Sufficiency Range
N (%) 4.25  
P (%) 0.57 0.20-0.50
K (%) 4.73 1.50-3.00
Ca (%) 0.52 0.3-1.20
Mg (%) 0.29 0.15-0.50
S (%) 0.39 0.15-0.40
Mn mg/kg 16.0 25-100
Zn mg/kg 23.0 15-70
Cu mg/kg 14.9 5-25
Fe mg/kg 110 NA
B mg/kg 8.0 NA

Interpretation of values based on top of the plant.

In the final analysis, the health of the crop returns to both frequent scouting to pick up problems such as this and to emergency foliar application of manganese, either as a chelated Mn or as manganese sulfate. An application of 0.5 to 2 lbs of Mn per acre should support the corn plant until the root system has penetrated deep enough in the soil to reach the more acidic subsoil where Mn availability is likely to be greater. The exact rate depends on the size of the corn plants, the amount of coverage possible with the intended sprayer, the stress level the corn is under at application time, and the willingness of the grower to possibly make a second application if the first application is not sufficient.

 

Scout Corn Fields for Micronutrient Problems

Friday, June 3rd, 2011

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

With the recent heat, corn development has been proceeding rapidly and before the corn develops past the point where you can get into the field to treat for the most common micronutrient deficiencies we see in Delaware fields you or your consultant-scout should check your most developed corn fields. Pay particular attention to fields that have had a history of micronutrient problems in corn and small grains and in fields where the soil pH is close to neutral (pH of 7.0). Many fields in Delaware begin to show manganese (Mn) deficiency as our soil pH rises towards neutral or alkaline. Application of even a ¼ of a pound of actual Mn per acre up to 1 or 2 lbs/acre in with a post-emergence weed control spray often will restore plant vigor. Mn deficiency in corn like most micronutrients shows up as an interveinal chlorosis meaning the parallel veins remain green and the tissue in between the veins turns yellow to white. The symptoms occur first on the newest growth since the plant is unable to take Mn from older tissue (the first leaves to appear and that will die soon anyway) and move it to the newly developing leaves and ears. The fact that corn is setting its ultimate yield potential even as early as the fifth leaf stage is something we often forget. Micronutrient deficiencies during this early vegetative growth will certainly reduce yields since the active growing points, such as the developing ear, are the first to suffer from a deficiency since micronutrients are not mobile in the plant.

 

Barley With Multiple Nutrient Deficiencies

Friday, April 22nd, 2011

Richard Taylor, Extension Agronomist; rtaylor@udel.edu and Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu

Another field of barley with severe deficiency symptoms showed up in Kent County this past week. Although the field had received ammonium sulfate this spring, the rate used provided only about 10 to 15 lbs of S per acre, which is less than the crop requirement. If the low S fertilization rate is coupled with the heavy rainfall many areas have experienced over the past several weeks, it would not be surprising that a significant amount of the sulfate-S has leached below the rooting zone of barley. In this case, although the visual symptoms (Photo 1 and 2) suggested sulfur (S) deficiency with general chlorosis of the leaves, especially the newest leaves, and shortened plants, the soil test suggested that S was not the only deficiency likely to impact barley yield even if sulfur were added (Table 1). On the bad sample note the low soil organic matter (SOM) level (0.9%) and the impact on the cation exchange capacity (CEC) of the soil (2.1 meq/100 grams of soil in the bad area versus 3.6 meq/100 grams of soil in the good area). The CEC impact was also evident in the amount of potassium (K) and magnesium (Mg) that the soil could hold.

Photo 1. Close-up of deficient barley plants showing general chlorosis, especially in newest leaves, and stunting.

Photo 2. Field view of deficient barley plants showing general chlorosis and stunting compared with less affected plants in the background.

The short term solution to the problem is the addition of K-Mag (0-0-22-11Mg-22S) fertilizer to the field. However, the soil test results suggest that on a longer-term horizon, the critical need of the field is the addition of organic matter, either as green manure crops, compost additions, or manure additions. Trying to maximize the amount of crop residue and minimize the amount of SOM mineralization due to tillage operations is also recommended. The use of winter cover crops and green manure crops whenever the field is not being cropped will gradually raise the SOM levels, as will any additions of manures or composts. Not only with organic will additions help raise the CEC and soil nutrient holding capacity but will also help increase water holding capacity and improve yields in the long run.

Table 1. Soil test report on barley field comparing good and bad areas.

Good Barley Bad Barley
Soil pH 1:1 6 6.3
Buffer pH 6.9 7
Organic Matter % 2.4 0.9
U of D P Sat Ratio 39 59
Mehlich3 Phosphorus ppmP/FIV 193 144
K ppm 98 54
Ca ppm 442 275
Mg ppm 74 44
SO4-S ppm 20 7
Zn ppm 4.56 2.99
Mn ppm 61 15
B ppm 0.36 0.16
CEC meq/100g 3.6 2.1
H* 15 10
K* 7 7
Ca* 61 65
Mg* 17 18
Na* 0 0

*Indicated Base Saturation

 

Manganese Deficiency Can Worsen with Spring N Applications on Small Grains – Part 2

Thursday, April 14th, 2011

Richard Taylor, Extension Agronomist; rtaylor@udel.edu and Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu

Last week, we discussed the possibility that either the starter fertilizer or knifed in nitrogen solution from the previous year’s corn crop might be responsible for the row-like pattern to manganese (Mn) deficiency that we had observed in barley recently fertilized with broadcast nitrogen (N). We took soil tests within the rows where barley was alive and vigorously growing (good area) and between the rows where barley plants were dead or growing very poorly (Photo 1). The soil samples have been analyzed and support our original conclusion (Table 1).

 

 

Table 1. Soil test analyses of good and bad barley areas in field showing barley surviving on 30-inch row spacing.

Barley Area Sampled

Sample Depth (inches)
0 to 4 4 to 8 8 to 12
Water pH Mn lb/A Zinc lb/A Water pH Mn lb/A Zinc lb/A Water pH Mn lb/A Zinc lb/A
Bad barley 6.1 15.1 8.5 6.6 9.0* 2.9 6.6 5.0* 1.0*
Good barley 6.2 16.3 8.7 6.3 10.8 3.2 6.5 6.3* 1.3*

*Deficient soil test level

Photo 1. Barley rows generated following renewed spring growth and nitrogen application showing effect of last year’s fertilizer (either starter band or knifed in nitrogen solution). Barley between corn rows was either severely Mn deficient or had died while barley on rows 30 inches apart grew vigorously.

Another interesting factor showed up on the soil test results. While the visual symptoms resembled traditional Mn deficiency on barley, the soil test indicated that at the deepest (8 to 12 inch) sampled layer zinc was also deficient. For any crop planted after barley (soybeans by tradition), the grower should conduct a tissue analysis mid-season before the crop begins to bloom to determine if tissue zinc levels indicate the possibility of a hidden zinc deficiency that could reduce yield potential. In addition, the grower should scout the crop for obvious zinc and Mn deficiency symptoms so that foliar zinc or Mn can be applied as early as possible.

Zinc deficiency symptoms on soybean include the following:
· Soybean yields are considerably decreased in zinc deficient soils.

  • · Deficient plants have stunted stems and leaves with chlorotic interveinal areas.
  • · Later on the entire leaves turns yellow or light green.
  • · Lower leaves may turn brown or grey and may drop early.
  • · Few flowers are formed and the pods that are formed are abnormal and slow in maturity.

Manganese deficiency symptoms on soybean include the following:
· Manganese deficiency commonly occurs in plants in well drained, neutral and alkaline soils.

  • · Interveinal areas become light green to white and the veins remain green.
  • · Necrotic brown spots develop as the deficiency becomes more severe.
  • · The leaves drop prematurely.
  • · Soybean yields can be significantly reduced by Mn deficiency.

Both micronutrient deficiencies can be reduced or eliminated by either a soil application of the sulfate or oxide compound of the micronutrient at 15 to 25 lbs per acre or by a foliar application of either the chelated form of the micronutrient or the sulfate form of the micronutrient at 1 to 2 lb of the nutrient per acre.

 

Zinc Levels in No-Till and High Phosphorous/pH Soils

Friday, April 8th, 2011

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

I’ve noticed several soil tests recently that showed very low levels of zinc and at the same time high levels of available phosphorus and pH levels in the mid to upper 6 range. Growers should evaluate their most recent soil test reports especially if they are in continuous no-till systems. The combination of cold, wet soils in no-till production systems and high phosphorus, low zinc, and moderate to high pH levels can lead to some early season zinc deficiencies. Be sure to scout these fields frequently for symptoms of zinc deficiency.

The soil tests reports I’ve seen have shown zinc levels as low as 1.8 lb Zn/acre up to almost 5 lbs per acre and these values seem too low to me. Fields at these levels may need either a foliar zinc application once the corn is up and growing or a broadcast application of zinc sulfate to prevent early season zinc deficiency from injuring a corn crop. Another option is the use of an acidifying starter fertilizer possibly with a little zinc added to the fertilizer. The acidification of a narrow band near the corn seed can easily boost zinc uptake and prevent early season problems.

Manganese Deficiency Can Worsen with Spring N Applications on Small Grains

Friday, April 8th, 2011

Richard Taylor, Extension Agronomist; rtaylor@udel.edu and Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu

Over the years, with respect to soil pH and manganese (Mn) deficiency, we have found that barley seems to be if not the most sensitive then close to the most sensitive small grain. When soil pH approaches the mid 6 range where we would expect it to be optimum for corn and beans, we often see Mn deficiency symptoms on barley, especially in certain areas of the state where the native Mn levels are low. During late fall and winter, the symptoms can often be confused with winter injury, wind burn, or other problems. However, the confusion usually clears after nitrogen (N) fertilizer is applied in the spring. Unfortunately, clearing the confusion often means that partial or entire stands of barley are lost.

The impact of spring N can vary depending on the soil acidity profile. If the Mn deficiency is severe or if the deeper soil layers are higher in pH, the N applied can cause barley plants to quickly die or, as frequently described, the barley appears to go backwards in appearance. The N stimulates rapid growth and if Mn is not available either as a result of soil pH levels or just low native Mn levels in the soil, the plants suffer significant damage.

This has been the case in several fields in southwestern Kent County over the past couple of weeks. Of particular interest is a field shown in the photographs below. The field developed striping across it on 30-inch centers (Photos 1, 2, and 3). In some areas, plants between the “rows” died and disappeared (Photo 4) and in other areas plant growth was slower other than in the “rows”. As can be seen in the photos, the rows are very straight and on 30-inch centers. We think the pattern follows where starter fertilizer was applied next to the corn rows last year since the lines are very straight. Rather than residual nutrients, the effect is very likely due to the slight acidulation of the soil that surrounded the banded starter fertilizer. The slightly lower pH in these areas has increased Mn availability just enough so that the plants were healthy enough to survive until the field received foliar Mn about a week before the photographs below were taken. Between the ‘rows” where banded starter did not affect Mn availability, the plants were so stressed for Mn that the N application caused them to die.

This week we took additional soil samples to investigate whether we can detect the small pH differences expected and we will report on the results in a future issue of Weekly Crop Update.

A concern that the grower may have is whether the Mn deficiency will show up in double-cropped soybeans if they are planted after the barley. First, the foliar treatment on the barley will not have any effect on a future crop. Second, a soybean crop is subject to Mn deficiency but whether the soil Mn levels are low enough for symptoms to appear is still in question. Barley seems to be more sensitive than soybean so visual symptoms may not been seen in the soybean plants. However, there is a strong possibility that the soybean crop will suffer from what is often referred to as “hidden hunger’. This occurs when the soil Mn availability is not quite low enough to stimulate visual symptoms but is at the critical range where yield potential is lowered without visual symptoms appearing. Our recommendation is that either the grower should consider a broadcast application of Mn (usually for a broadcast application 30 lbs actual Mn is applied per acre) so that soil Mn levels are increased above the critical range or the grower should plan on a foliar Mn application around the fifth leaf stage (V-5) when enough leaf area is present to adsorb adequate Mn from a foliar application. One to two pounds of actual Mn is the suggested rate for a single application. This rate is suggested since application costs are more than the cost of the product and so a single application will be the preferred method.

Photo 1. Barley rows generated following renewed spring growth and nitrogen application showing effect of last year’s starter fertilizer.

Photo 2. Barley between corn rows was either severely Mn deficient or had died while barley on rows 30 inches apart grew vigorously.

Photo 3. Wide view of barley field with old corn rows showing vigorous barley growth.

Photo 4. Between the “rows” barley Mn deficiency symptoms following spring N application were severe.

Will Your Crop Suffer from Sulfur Deficiency this Cropping Year?

Friday, March 11th, 2011

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

Past and recent emphasis has been placed on reducing sulfur (S) emissions from power plants, diesel vehicles, and other industries. The question of whether the Clean Air Act and other programs run by the Environmental Protection Agency are accomplishing their objectives can be answered by the farm community with respect to sulfur emissions. The answer growers would likely give is that yes the air quality programs have worked, but so well that their crops are increasingly showing sulfur deficiency symptoms, especially when grown on sandy, low organic matter, non-manured soils.

Why is S critical for maximum economic yields (MEY)? Sulfur is needed by a crop when making certain amino acids such as cystine and methionine that are vital components of many proteins. The entire factory output (yield) of a crop is dependent on proteins that make up the chlorophyll molecule, all the plant enzyme systems, the plant’s genetic material such as DNA, the assimilation function of legume rhizobia, and all the inter-related metabolic activity in the plant. The ideal nitrogen (N) to sulfur ratio in a plant is 15:1. Above that ratio, the S concentration is not adequate for MEY.

Sources for S include commercial fertilizers, atmospheric deposition, and manures or biosolids. The movement away from the old superphosphate (16 to 22% P2O5 and 12 to 14% S) to triple superphosphates in the late 1900s and then more recently to ammonium phosphates and ammonium polyphosphates (DAP, MAP, and others) has reduced the amount of S fertilizer applied without us consciously being aware of the trend. With the success of the Clean Air Act, atmospheric S deposition had dramatically decreased even before the very recent change over to ultra low sulfur diesel fuel. In addition, the emphasis on nutrient management planning to reduce manure application rates due to phosphorous buildup in the soil and the development of programs to help move poultry manure to areas without manure resources has also contributed to reduced S application rates.

Who should be concerned about the potential for S deficiency on their crops? The answer is that probably everyone but especially those growers with coarse textured soils, with soils low in organic matter, or with soils that have received enough rainfall or irrigation water to leach S below the crop rooting zone should be concerned. For shallow rooted crops such as wheat and barley, it is especially critical to ensure that adequate S is available during tillering and early growth and development. Growers should consider adding enough ammonium sulfate to their normal nitrogen application to provide from 20 to 30 lbs of S per  A in the first N application split in the spring.

If there is adequate S accumulation in the soil clay subsoil as determined with a deep soil test, S fertilization may not be a yield limiting factor on deep rooted crops such as corn. However, this does not mean that early season growth won’t be improved with the early season addition of some type of sulfate fertilizer. Even in high yield irrigated environments, such an application could help improve yield potential or at least not limit yield.

Some growers will want to rely on soil test results to make a decision on whether to add S fertilizer. These growers should be aware that the normal soil test depth of 0 to 6 or 0 to 8 inches is not as good an indicator of soil S status as it is for phosphorus and potassium. Sulfur is taken up by plants as the sulfate (SO42-) ion and as an anion (negatively charged ion) in the soil that is similar to nitrate. It is subject to loss via leaching and anaerobic conditions (similar to denitrification).

Sulfur deficiency symptoms vaguely resemble those of N except that S, unlike N, is not mobile in the plant so symptoms occur first on new growth. Sulfur deficiency is most often described as stunting with general yellowing or chlorosis of the plant. For examples, please review the photos at the end of this article.

The choices available for fertilizing with S include ammonium sulfate and potassium magnesium sulfate (K-PoMag) plus ammonium thiosulfate, calcium sulfate (gypsum), magnesium sulfate (Epsom salts), potassium sulfate, and elemental sulfur. Sulfate is immediately available for plant uptake whereas elemental So must be oxidized by the soil bacteria (requiring warm soil temperatures and adequate moisture) into sulfate before plants can absorb the S. Organic sources (manures, crop residues, biosolids) must undergo mineralization into inorganic sulfate before being available for plant uptake.

Other by-products such as derivatives from battery acid are sold as S sources but should be evaluated carefully by the grower to be certain that potential problems such as heavy metal contamination, non-available S forms, or injurious compounds are not present. Even then the S form in some by-products will need to be converted into plant available forms by the soil microorganisms and if S is needed immediately or if soil conditions are not favorable for this conversion yield potential could be impacted negatively. Certainly, any form other than the sulfate form is not appropriate in-season when deficiency symptoms indicate the immediate need for S.

Photo 1. Induced sulfur deficiency in corn grown in sand culture. Note reddening of lower stem, general chlorosis or yellowing especially of new growth, and stunting of the plant.

Photo 2. Field corn showing stunting and general chlorosis or yellowing, especially of new growth on sandy soil in southern Delaware.

Photo 3. Sulfur deficiency in barley grown on a very light sandy soil low in organic matter in Sussex County, Delaware. Note general chlorosis or yellowing especially of new growth and severe plant stunting.

Photo 4. Sulfur deficiency in wheat grown on a very light soil low in organic matter in Sussex County, Delaware. Note general chlorosis or yellowing especially of new growth and severe plant stunting.

Check Soybeans for Manganese (Mn) Deficiency

Friday, June 11th, 2010

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

An interesting fact came up recently about the research retired Purdue University plant pathologist Don Huber has done linking glyphosate and reduced uptake of several nutrients in field crops. I found the notation that significantly lower tissue levels of the micronutrients manganese (Mn), zinc (Zn), and iron (Fe) are being taken up by the field crops he studied. In Delaware, we frequently see Mn deficiency symptoms on soybeans, especially on sandy soil or where the soil pH is maintained near neutral or above.

Just yesterday driving back from the University of Delaware Research and Education Center, I noticed Mn deficiency symptoms showing up in several fields. Manganese deficiency is characterized by dark green veins and light green (mild deficiency) to yellow (moderately severe deficiency) to white (severe deficiency) interveinal leaf tissue. The symptoms often are most severe on the most recently emerged leaves. Manganese deficiency symptoms are similar to the deficiency and toxicity symptoms of some of the other micronutrients.

 

Photo 1. Moderately severe interveinal chlorosis on no-till single-crop or full-season soybean. Note dark green veins with tissue between veins yellow. Younger leaves are most affected since Mn is not mobile in the plant.

Yield reductions can be avoided to a large degree by early diagnosis and treatment with foliar application of Mn. Multiple applications of foliar Mn may be needed especially when Mn deficiency is severe. If enough leaf area is present to absorb adequate Mn, a single application higher rate (1 to 2 lb Mn/acre) was shown to be effective by Virginia and North Carolina researchers. Ignoring or not catching the problem until later in the season can not only reduce yield potential but make a foliar application more difficult and possibly more expensive since driving over the soybeans may cause damage on drilled beans. You may need to treat early season symptoms several times since the leaf area available to absorb Mn is limited so always rescout treated fields to be sure Mn deficiency does not reappear after treatment.

 

Photo 2. Moderately severe interveinal chlorosis on no-till single-crop or full-season soybean. Note dark green veins with tissue between veins yellow.

Where the symptoms are widespread and moderate to severe, foliar Mn applied at 1 to 2 lbs Mn per acre can boost yields significantly. Since the crop is still in the vegetative stage, mild to moderate symptoms can be alleviated with a 0.5 lb Mn per acre foliar spray. Researchers in Delaware, Virginia, and North Carolina have shown that soybeans are very responsive to foliar Mn especially when applied well before soybeans begin to bloom.

Even if you do not apply foliar Mn, you should be making note of which fields and where in the field symptoms occur so you can monitor these areas in the future. If wheat or barley are to be planted this fall, careful early monitoring will allow you to apply Mn to the small grains before they are severely injured by Mn deficiency. You should also note the areas so you can do soil testing to determine the underlying problem. Check to see if the native Mn concentration in the soil is too low or whether the soil pH is too high since the higher the pH the lower the availability of Mn in the soil. Also, any factor restricting root growth (compaction, drought, etc.) can aggravate Mn deficiency symptoms and should be corrected.

Dr. Joseph Heckman at Rutgers University is writing a series of articles on Mn deficiency in Rutgers Plant and Pest Advisory publication. These publications are available on the web through the Rutgers New Jersey Agricultural Experiment Station. A recent article (Vol. 16, No. 7, page 3) showed research Dr. Heckman conducted comparing manganese sulfate and chelated manganese and this article can be found at the following web address: http://njaes.rutgers.edu/pubs/plantandpestadvisory/2010/vc051210.pdf