What is manganese for

Contents

Magnesium versus Manganese: What’s the difference? – Part I

Magnesium (Mg) and manganese (Mn) are essential plant nutrients. They are absorbed by plant roots as bivalent cations (Mg++ and Mn++). Deficiencies of both nutrients have been diagnosed in Michigan. There are important differences between the two nutrients. Their deficiency symptoms may be hard to distinguish in certain situations.

Magnesium is one of the three “secondary” plant nutrients along with sulfur and calcium. It is taken up in moderately large qualities compared to only trace amounts of Mn (Table 1). Magnesium is a constituent of the chlorophyll molecule. So Mg deficient plant leaves will become pale-green to yellow and then develop interveinal chlorosis (yellowing between veins). Magnesium is mobile in the plant and therefore the symptoms will start with the lower (older) leaves.

Table 1. Sufficiency ranges of magnesium and manganese in corn ear leaf just before silking, based on plant tissue analysis.

Nutrient

Sufficiency range (concentration in ppm)

Magnesium (Mg)

1,600 to 6,000

Manganese (Mn)

20 to 50


Photo 1. Magnesium deficiency in corn. Photo credit: University of Illinois

Most Michigan soils contain sufficient amounts of Mg. However, deficiencies have been observed particularly in the southwestern and western areas of Michigan on acid, coarse-textured soils.

Magnesium availability decreases in acidic soils when pH gets below 6.0 (Photo 2). Michigan State University Extension recommends Mg applications when the soil test value is less than 35 ppm on sandy soils or less than 50 ppm on fine-textured soils; also when Mg is less than 3 percent (as a percent of exchangeable bases on an equivalence basis) or when percent exchangeable potassium (K) exceeds the percent Mg on an equivalence basis. Applying high rates of potassium (K) fertilizer can induce Mg deficiency. Livestock feeding on Mg deficient grass can develop grass tetany disorder.


Photo 2. Relative availability of plant nutrients with soil pH on mineral
soil. The thickness of the bar indicates availability of the nutrient.

Manganese is not a part of chlorophyll, but it is vital for enzyme systems involved in photosynthesis. Thus, Mn deficiency also develops yellowing and interveinal chlorosis on leaves (Photo 3). Manganese is less mobile in the plant, therefore symptoms will appear first in the uppermost (youngest) leaves. Since yellowing of plants can be due to several factors such as K, Mg, iron deficiency, herbicide injury, poor nodulation and cyst nematodes, good scouting practices and tissue sampling may be needed to confirm the exact cause. Symptoms may look similar from a distance, but differences in the yellowing pattern may offer useful diagnostic clues. MSU Extension recommends that Mn be applied in a band as a starter fertilizer at planting or as foliar spray during the season.


Photo 3. Manganese-deficient soybean
plants. Uppermost (youngest) leaves
show interveinal chlorosis while the veins
remain green. Photo credit: Ron Gehl

In contrast to Mg, manganese availability increases in acidic soils and decreases markedly as soils become alkaline and pH gets above 7.0 on mineral soils (Photo 2). Soybeans will show Mn deficiency symptoms on high pH soils (Photo 3). The critical soil test value on mineral soil at pH 6.3 is 6 ppm and at pH 6.7 is 12 ppm. Manganese deficiency symptoms on soybeans also appear on peat or muck soils (Photo 4). In these soils, Mn deficiencies occur when the soil pH gets above 5.8 (Photo 5). The soil organic matter and Mn ions usually combine to form insoluble compounds. This reaction is favored by increasing pH.


Photo 4. Manganese deficiency on a muck
soil near Lansing, Mich. Photo credit: Ron Gehl


Photo 5. Relative availability of plant nutrients with soil pH on organic soil.

Research indicates that soil tests for Mn do not always closely correlate with crop response to Mn fertilizer. One reason is because extractable Mn level decreases when soil samples are air-dried. The Mn oxidation state increases in the drying process, thereby decreasing its solubility and extractability.

Part II of this article series, “Magnesium versus Manganese: Supplemental sources and application methods – Part II,” addresses Mg and Mn supplemental sources and application methods.

What Is the Difference between Magnesium and Manganese?

Chemically, the two elements are very different. Magnesium and manganese are both metals, but belong to different groups. Magnesium is an alkali metal and is highly reactive, which means that it is never found as a free element in nature. It tarnishes in the air and reacts chemically with water in a manner similar to other alkali metals such as calcium, though much less violently. Manganese is chemically more similar to iron than to magnesium. It oxidizes readily, and it is usually found in the earth’s crust as manganese dioxide, a mineral that is also called pyrolusite.

Both elements are important nutrients but serve different functions. Magnesium, although present in the human body in small amounts, is still extremely important. It is used by every major organ and metabolic system, especially in bone formation and in the heart and musculature function. Magnesium plays a role in hundreds of metabolic functions, and without it, we could not live. The human body uses magnesium to modulate levels of other minerals in the body, and it is the trigger for many enzymes which the body requires to convert food to energy. Magnesium also plays an important role in the entire ecology of the earth, as it is one of the central elements in the chlorophyll molecule, which fuels all photosynthesis in green plants.

Manganese is also an important micronutrient but in other ways than magnesium. The human body uses much less manganese than magnesium, and it has a narrower range of functions, most of which are related to metabolic functions involving carbohydrates, fats, and cholesterol, among others. It is also one component of an important enzyme that helps the body convert certain molecules to glucose, or blood sugar. Manganese is an important component in many other enzymes as well and is a component of the human body’s most important natural antioxidant, which helps protect our cells from damage due to oxidation by harmful ions and free radicals.

Why do we need magnesium?

Share on PinterestMany types of nuts and seeds are rich in magnesium.

Magnesium is one of seven essential macrominerals. These macrominerals are minerals that people need to consume in relatively large amounts — at least 100 milligrams (mg) per day. Microminerals, such as iron and zinc, are just as important, though people need them in smaller amounts.

Magnesium is vital for many bodily functions. Getting enough of this mineral can help prevent or treat chronic diseases, including Alzheimer’s disease, type 2 diabetes, cardiovascular disease, and migraine.

The following sections discuss the function of magnesium in the body and its effects on a person’s health.

1. Bone health

While most research has focused on the role of calcium in bone health, magnesium is also essential for healthy bone formation.

Research from 2013 has linked adequate magnesium intake with higher bone density, improved bone crystal formation, and a lower risk of osteoporosis in females after menopause.

Magnesium may improve bone health both directly and indirectly, as it helps to regulate calcium and vitamin D levels, which are two other nutrients vital for bone health.

2. Diabetes

Research has linked high magnesium diets with a lower risk of type 2 diabetes. This may be because magnesium plays an important role in glucose control and insulin metabolism.

A 2015 review in the World Journal of Diabetes reports that most, but not all, people with diabetes have low magnesium and that magnesium may play a role in diabetes management.

A magnesium deficiency may worsen insulin resistance, which is a condition that often develops before type 2 diabetes. On the other hand, insulin resistance may cause low magnesium levels.

In many studies, researchers have linked high magnesium diets with diabetes. In addition, a systematic review from 2017 suggests that taking magnesium supplements can also improve insulin sensitivity in people with low magnesium levels.

However, researchers need to gather more evidence before doctors can routinely use magnesium for glycemic control in people with diabetes.

3. Cardiovascular health

The body needs magnesium to maintain the health of muscles, including the heart. Research has found that magnesium plays an important role in heart health.

A 2018 review reports that magnesium deficiency can increase a person’s risk of cardiovascular problems. This is partly due to its roles on a cellular level. The authors observe that magnesium deficiency is common in people with congestive heart failure and can worsen their clinical outcomes.

People who receive magnesium soon after a heart attack have a lower risk of mortality. Doctors sometimes use magnesium during treatment for congestive heart failure (CHF) to reduce the risk of arrhythmia, or abnormal heart rhythm.

According to a 2019 meta-analysis, increasing magnesium intake may lower a person’s risk of stroke. They report that for each 100 mg per day increase in magnesium, the risk of stroke reduced by 2%.

Some research also suggests that magnesium plays a role in hypertension. However, according to the Office of Dietary Supplements (ODS), based on current research, taking magnesium supplements lowers blood pressure “to only a small extent.”

The ODS call for a “large, well-designed” investigation to understand the role of magnesium in heart health and the prevention of cardiovascular disease.

4. Migraine headaches

Magnesium therapy may help prevent or relieve headaches. This is because a magnesium deficiency can affect neurotransmitters and restrict blood vessel constriction, which are factors doctors link to migraine.

People who experience migraines may have lower levels of magnesium in their blood and body tissues compared with others. Magnesium levels in a person’s brain may be low during a migraine.

A systematic review from 2017 states that magnesium therapy may be useful for preventing migraine. The authors suggest that taking 600 mg of magnesium citrate appears to be a safe and effective prevention strategy.

The American Migraine Foundation report that people frequently use doses of 400–500 mg per day for migraine prevention.

The amounts that may have an affect are likely to be high, and people should only use this therapy under the guidance of their doctor.

Read more about magnesium for migraine.

5. Premenstrual syndrome

Magnesium may also play a role in premenstrual syndrome (PMS).

Small-scale studies, including a 2012 article, suggest that taking magnesium supplements along with vitamin B-6 can improve PMS symptoms. However, a more recent 2019 review reports that the research is mixed, and further studies are needed.

The American College of Obstetricians and Gynecologists suggest that taking magnesium supplements could help to reduce bloating, mood symptoms, and breast tenderness in PMS.

6. Anxiety

Magnesium levels may play a role in mood disorders, including depression and anxiety.

According to a systematic review from 2017, low magnesium levels may have links with higher levels of anxiety. This is partly due to activity in the hypothalamic-pituitary-adrenal (HPA) axis, which is a set of three glands that control a person’s reaction to stress.

However, the review points out that the quality of evidence is poor, and that researchers need to do high quality studies to find out how well magnesium supplements might work for reducing anxiety.

The Role of Manganese

From photosynthesis to building carbohydrates, manganese packs a punch

Like other micronutrients we’ve discussed, manganese is a mighty mite. It requires only 10 ppm to 25 ppm
in the soil, but it packs a punch.
Farm Journal Field Agronomist Ken Ferrie has observed 5 bu. to 7 bu. per acre yield increases in soybeans and 3 bu. to 5 bu. per acre increases in corn when manganese was applied to correct deficiencies.
In this installment of Nutrient Navigator, we’ll explain why manganese is important and how to spot problems. In the next installment, we’ll tell you how to avoid or correct them.
Manganese exerts its impact because of its role in the vital photosynthetic process, which converts sunlight into plant energy, Ferrie explains. “It affects chloroplast formation in leaves, which impacts chlorophyll production. It also plays a role in building carbohydrates and metabolizing nitrogen, especially in corn. It also serves as a trigger that causes certain enzymes to perform their roles in the plant.”
Plants vary in their response to manganese, Ferrie continues. Soybeans, oats and wheat are highly responsive; corn falls into the medium range.
“Monitor these crops more closely than less-responsive crops,” Ferrie says. “If you’re going to apply manganese fertilizer to just one crop, it should be soybeans. But if you see manganese deficiency in corn, pay attention because the following soybean crop will show the effect more aggressively.”

Although there are differences, manganese deficiency symptoms can be confused with those of zinc deficiency and the early stages of iron deficiency. Confirm visual symptoms with plant tissue testing.

Recognizing manganese deficiency symptoms is important because they are your main tool in deciding whether to treat, Ferrie says. Because manganese is not mobile inside plants, you’ll find deficiency symptoms on the newer growth.
Since the nutrient affects chlorophyll production, deficiencies reveal themselves with unnatural leaf color. “Younger leaves will exhibit chlorosis, so they will be kind of olive green, instead of bright green, in color,” Ferrie says. “When you inspect closely, you will discover chlorosis between the veins, while the veins themselves remain unnaturally dark.
“In corn, the lighter stripes will run the full length of the leaf,” Ferrie continues. “They can be mistaken for zinc deficiency, magnesium deficiency and the early stages of iron deficiency. But zinc striping shows up only on the lower half of the leaf, while magnesium striping occurs only on the older leaves. With iron deficiency, the veins become even more pronounced, darker in color, than with manganese deficiency, resulting in greater contrast between the interveinal area and the vein.
“If a moderate manganese deficiency becomes severe, the chlorosis between the veins turns almost white, and the dark color of the veins disappears,” Ferrie continues. “In soybeans, brown spots eventually appear between the veins, and usually, the leaf falls off. In corn, the chlorosis turns white, so dead spots show up in the tissue between the veins.”
Manganese toxicity, the opposite of deficiency because it results from excessive manganese, is characterized by darkening of veins and some chlorosis on the older leaves of plants. In corn, dead tissue develops between the leaf veins. In soybeans, leaves crinkle and cup downward.

When soybeans are deficient in manganese, brown spots appear between the leaf veins. The leaves also crinkle and cup downward. Eventually, the leaves fall off.

Most of the manganese used by plants comes from the soil solution (water and nutrients held in pore spaces between soil particles). Manganese is mineralized from unavailable forms and released into the soil solution by microbial activity. Remember the healthier your soil, the more microbes there are and the more nutrients are available to plants.
Manganese in the soil solution reaches plant roots by processes called mass flow and diffusion. In mass flow, nutrients are carried in water as it moves from the soil through the plants and, ultimately, out of the leaves and into the atmosphere through the process called transpiration. In diffusion, nutrients move from an area of higher concentration to one of lower concentration.
The process—from the unavailable form to the available form and into your plant—can be called the manganese cycle, Ferrie says. If the cycle gets thrown out of whack, plants become deficient in manganese or suffer from manganese toxicity.
With experience, you’ll learn how to identify deficiencies and where to expect them, Ferrie says. As with all fertility issues, soil testing is one of your primary tools.

In corn, manganese deficiency shows up as lighter stripes running the entire length of the leaves.

“But when soil testing for manganese, there are challenges,” Ferrie says. “For one, the availability of manganese is affected by soil pH and organic matter content. The manganese level that is considered adequate at a water pH reading of 6.2 in one soil will be considered deficient at a water pH of 7.2 in another soil. So, test your soil based on established management zones.
“Secondly, separate out naturally high pH areas, separate organic soils (mucks and peats) from mineral soils and separate clays and clay loams from sandy loam soils,” Ferrie says.
Be aware different laboratories use different chemicals to extract manganese from soil. This results in different scales designating high, medium or low soil test values. “Using the same laboratory every time you soil test will make it easy to see changes in soil levels,” Ferrie says.
“A soil test provides a starting point by telling you whether the soil manganese level is high, medium or low,” Ferrie says. “But because the amount of fixation varies based on soil texture and pH, I’ve seen instances where a farmer doubled the amount of manganese in his soil without increasing uptake by plants. I recommend combining soil testing with knowledge of where to expect deficiencies, field scouting and tissue testing.”
Anticipate pH issues where soil pH is too high or too low; in muck soils; in sandy, leachable soils; in poorly drained soils; and in any soil during a drought. “At a water pH reading above 6.5, manganese becomes tied up and unavailable to plants,” Ferrie explains. “Below a water pH of 5.0, excessive amounts of manganese become available, and you may encounter toxicity problems.”
On muck soils, inorganic manganese (the form that can be used by plants) becomes tied up by organic material and unavailable to plants. “A muck soil with a water pH reading above 6.5 is facing a double whammy,” Ferrie says. “Availability of manganese is almost guaranteed to be poor.”
In sandy soils with poor waterholding capacity, manganese is leached away. “But a lack of moisture can cause problems in any soil,” Ferrie says. “If even a heavy soil runs out of water, mass flow will be reduced and less manganese will enter the plant.”
Cold, wet soil conditions can also exert a double whammy on manganese, regardless of soil texture. “In those conditions, microbial activity slows down, so less manganese is mineralized from the soil,” Ferrie says. “Because plant growth also slows down, less manganese is taken up. Deficiencies will occur, regardless of how much manganese is in the soil.”
Also look for manganese toxicity, Ferrie says. In waterlogged conditions, manganese oxide, which is unavailable to plants, undergoes a chemical reduction and enters the soil solution.
“Target areas of high soil pH, poor drainage, high-organic matter levels and highly leachable sands for scouting every year, regardless of soil test readings,” Ferrie advises.
“When you notice visual symptoms, follow up with tissue analysis to confirm the deficiency,” he adds. “After a few years of scouting, you’ll know where to expect problems every year and where to expect them occasionally because of cold weather, wet soils or severe drought.”

A Mighty Micronutrient

Keep a close eye on soybeans, oats and wheat, which are highly responsive to manganese. Corn is less responsive. If you’re going to apply manganese fertilizer to just one crop, it should be soybeans.

Where to Expect Manganese Problems

  • Soils with a water pH reading below 5.0 or above 6.5
  • High-organic matter or muck soils
  • Sandy, leachable soils
  • Saturated or waterlogged soils
  • On any soil during drought or cold, wet growing conditions

Manganese Management Tips

  • Soil test—determine soil test levels
  • Identify and scout areas with potential problems
  • Confirm scouting with tissue testing
  • Compile history of problem areas to focus future scouting efforts
  • Plan to routinely treat areas that always have problems

Know symptoms of these 7 corn nutrient deficiencies

Nitrogen is still the 800-pound gorilla when it comes to corn nutrition. But it’s now joined by several other nutrients, even some secondary and micronutrients, which can be limiting enough in some situations to affect yield. Part of this change may be due to farmers striving for higher yields. Crops consultants like Joe Nester, Nester Ag, Bryan, Ohio, say Clean Air Act laws resulting in less sulfur in the air and raising the pH of rain have also played a role.

You can find symptoms of nutrient deficiencies in the Corn & Soybean Field Guide published by the Purdue University Crop Diagnostic Training and Research Center. Corey Gerber, a Purdue Extension agronomist and director of the center, notes they also just released the Corn Field Scout app for iPhones and Android cellphones. Soybean Field Scout is also available. These apps cost $5.99 each.

Here are symptoms for seven deficiencies you could find in corn this year. Descriptions provided here are from the Corn Field Scout iPhone app.

1. Nitrogen. Younger plants with nitrogen deficiency may be stunted and spindly, with light-green or yellowish-green color. Older plants show traditional V-shaped yellowing on older leaves. It starts at the leaf tip and progresses down the midrib.

2. Phosphorus. Low levels in the soil is an obvious cause of phosphorus deficiency, but cold soils, wet soils, or dry and compacted soils can limit how much phosphorus roots can find, producing a deficiency in the plant. Early symptoms include stunted, dark-green to bluish-green plants with purpling or reddening of tips and leaf margins.

3. Potassium. Yellowing leaf margins on lower leaves, beginning at the tip and running around the margin, is a symptom of potassium deficiency. Plants may wilt easily, especially in full sunlight.

4. Sulfur. Young plants deficient in sulfur will be stunted, spindly and light green in color. Upper leaves will become light green first. Interveinal yellowing or leaf striping is a key symptom.

5. Magnesium. Symptoms for magnesium deficiency are most likely to appear on sandy, acidic soils in high rainfall areas, where soil tests are less than 100 pounds per acre for magnesium, where soil exchangeable potassium levels are high, and where a high rate of ammonia was applied on soils with low magnesium levels.

Look for yellow to white interveinal striping in young plants. Beaded streaking of dead, round spots may appear. Older leaves become reddish purple. Actual symptoms expressed for this deficiency — or any deficiency — are heavily tied to weather conditions. Confirm suspected deficiencies with tissue tests.

6. Manganese. Light-green or olive-green leaves may indicate a problem with manganese. Look for a slight yellowish stripe on upper leaves. Manganese deficiency is most common where manganese soil test levels are low and soil pH and/or organic matter levels are high, in low areas of fields, and in organic sands, peats and mucks.

7. Zinc. Low soil levels combined with high pH or high phosphorus levels may produce symptoms of zinc deficiency. You may also see problems with zinc on cool, wet soils with low organic matter, when it’s cloudy early in the season, and if soil compaction affects rooting.

Classical symptoms are white, interveinal strips extending from leaf base to leaf tip. Leaf edges, tips and midribs stay green.

How to Fix Manganese Problems

You’ve tested your soil, scouted your crop and confirmed manganese problems by sending plant tissue samples to a laboratory. Now it’s time to fix those deficiency or toxicity issues and minimize their impact on yield.

“In some cases, broadcasting manganese, along with your other fertilizer, might increase soil test levels and prevent or correct deficiencies,” explains Farm Journal Field Agronomist Ken Ferrie. “However, in most situations, foliar applications, (possibly several applications) will be required.”

NutrientNavigator

One place to broadcast manganese is on sandy, highly leachable soils. “Unless your sandy soil has a low pH, you can expect manganese problems,” Ferrie says. “Because of the risk of leaching on sandy soil, apply manganese fertilizer as close to plant uptake as possible—in the spring, along with potassium and phosphorus, for example.”

Ferrie recommends using the sulfate form of manganese because it is more readily available. On sandy soils, though, you might have to make an application every season, he adds.

In heavier soil, the problem usually involves getting plants to take up manganese from the soil before it becomes tied up and unavailable. “In such soils, broadcasting, in my experience, is pretty inefficient,” Ferrie says. “Doubling the amount of manganese in the soil won’t help. If you do choose to broadcast, apply the manganese as close to uptake by the plants as possible because anything not taken up will quickly become fixed and unavailable.”

In these soils, or any time you spot a manganese deficiency in growing crops, the best solution is foliar application. “But first, make sure manganese really is the problem,” Ferrie says. “Scout your crops, and send off samples for tissue testing. After you have become skilled at identifying visual symptoms, you might be able to eliminate tissue testing. In highly organic muck soils, where you know deficiencies will occur, apply manganese as soon as you see visual symptoms.”

When plants are small, the challenge with foliar application is to make sure the spray lands on plants, rather than on the soil where it will become tied up and unavailable. “If possible, use a directed spray or band the fertilizer over the row,” Ferrie advises. “Because manganese does not move inside the plant, you might have to make another application after new growth emerges. With severe deficiencies, especially with soybeans in mid-flower (the R2 or R3 reproductive stage), you might need to make several foliar applications.”
Soil-applying won’t help in alkaline soils, high-organic matter mucks or sands. Although foliar application is the best choice, you might be able to fix early deficiencies in those soils by adding manganese to your starter fertilizer, Ferrie notes. “In corn, you might also sidedress manganese, especially if you use a tool such as the Y-Drop,” he says. “It places fertilizer near the base of the corn plant, where it has a better chance to be carried inside by water through the mass flow process.”

In typical mineral soils, which is most soils, you are less likely to encounter manganese problems (although they might arise during drought or cool, wet growing conditions). “Clay loam soils, which are moderately drained and have water pH readings of 6.8 or 6.9, will have intermittent deficiencies,” Ferrie says. “In those soils, starter might not pay every year, and soil applications might get tied up. Scout those fields, and make foliar applications when needed. If possible, use variable-rate technology for your foliar application; you might only need to treat the areas prone to manganese deficiency.”

If you farm fields where organic matter content varies from 1% to 3%, you can help prevent manganese problems by varying your limestone rate. “If you apply a single rate across the whole field, you will apply too much lime on some soils and too little on others,” Ferrie says. “Overapplication wastes money, and underapplication will not maintain optimum pH levels. But, more important, if soil pH gets above 6.5, manganese and other nutrients will become less available. If it falls below 5.0, the soil might release excessive amount of manganese, which can be toxic to plants.”

In all situations, manganese sulfate is the most efficient form of manganese fertilizer, Ferrie says. “If you foliar-apply, use the sulfate form or chelated manganese. Manganese oxide fertilizer is cheaper, but it contains less available manganese.”

“Because manganese is not mobile inside the plant, time your fertilizer applications to match the early symptoms of manganese deficiency in your crop,” Ferrie adds. “That might not be the ideal time to simultaneously apply a herbicide or fungicide.”

Ferrie believes the unintentional overapplication of lime is causing manganese deficiencies in fields. Problems arise when a farmer’s nutrient management techniques have not kept pace with their implementation of new tillage practices.

“Aside from problem soils, a high percentage of the manganese problems I encounter as a consultant are, to some extent, manmade,” he says. “The problems result from how farmers incorporate lime.
“Years ago, the standard lime application rate was 3 tons to 4 tons of lime per acre followed by moldboard plowing or deep disk-ripping to incorporate. We applied 3 tons or 4 tons because we only tested our soil every five years, so pH showed major changes. We had to apply enough lime to correct past acidity and prevent acidity in the future.

“Today, many farmers use no-till, strip-till, vertical tillage or some other form of conservation tillage, which provides less incorporation of lime at a shallower depth,” Ferrie continues. “Because their application rates remain the same, they are incorporating large applications of limestone only a few inches deep. Three tons of lime per acre incorporated only 2″ deep is the equivalent of 6 tons or 7 tons applied to the surface layer of the soil. That shifts the surface pH to alkaline and causes early season manganese deficiencies.”
When Ferrie discovers a new farm showing frequent early season manganese deficiencies, his first step is to test soil pH at 0″ to 3″ deep and 3″ to 6″ deep. If the surface pH readings are 6.8 to 7.2, that’s likely the cause of the manganese problems, he says. “The farmer might have to temporarily fix those problems by making foliar applications of manganese fertilizer. But long-term, the solution is to till to correct the stratification. After the farmer mixes lime uniformly throughout the top 6″ of soil, he can return to no-till, strip-till or reduced tillage,” he adds.

“In the future, the farmer should test the soil every two years and apply 1 ton to 1½ tons of lime per acre every other year, rather than 3 tons to 5 tons every five years. This not only improves the availability of manganese and other micronutrients, but improves overall soil health by creating a better environment for soil microbes.”

Manganese toxicity is the opposite problem from manganese deficiency. “One of the primary causes of toxicity is acid soil,” Ferrie says. “If the soil pH is too low, manganese becomes highly available in the soil solution, which restricts plants’ ability to pick up calcium.

“Inside the plant, one of the main functions of calcium is to prevent manganese toxicity. It does that by forming calcium pectate, which blocks excessive amounts of manganese from entering the plant. Consequently, the visual symptoms of calcium deficiency are identical to the symptoms of manganese toxicity because that’s what it actually is,” he adds.

The solution to manganese toxicity is to lime the acid areas. “The lime must be tilled in to correct acidity throughout the soil profile,” Ferrie says. “That process might take six or seven years. After the acidity is corrected, a farmer can go to no-till, strip-till or reduced tillage. He should make frequent light applications of lime to hold pH in the optimum range.”

Toxicity also occurs in saturated or waterlogged soils. “In waterlogged soil, manganese toxicity is likely to be only one of many problems,” Ferrie says. “In that situation, there really is no way to correct manganese toxicity. The only solution is to improve drainage, if possible.”

Understand the role of pH and organic matter content in creating manganese issues; test your soil and learn to spot deficiency and toxicity symptoms, and you’ll keep manganese problems at bay, Ferrie concludes.

Magnesium striping only occurs on older corn leaves. Look for veins that are unnaturally dark and lighter stripes that run the full length of the leaves.

© Darrell Smith

Manganese (Mn) is an essential plant mineral nutrient, playing a key role in several physiological processes, particularly photosynthesis. Manganese deficiency is a widespread problem, most often occurring in sandy soils, organic soils with a pH above 6 and heavily weathered, tropical soils. It is typically worsened by cool and wet conditions (Alloway 2008). Numerous crop species have been reported to show high susceptibility to Mn deficiency in soils, or a very positive response to Mn fertilization, including cereal crops (wheat, barley and oats), legumes (common beans, peas and soybean), stone fruits (apples, cherries and peaches), palm crops, citrus, potatoes, sugar beets and canola, among others. The impact of Mn deficiencies on these crops includes reduced dry matter production and yield, weaker structural resistance against pathogens and a reduced tolerance to drought and heat stress.

Manganese has a relatively low phloem mobility in plants, and as a result, typical leaf symptoms of Mn deficiency first develop in younger leaves. The critical concentration for Mn deficiency is generally below 20 ppm dry weight in fully expanded, young leaves. In the case of dicots, Mn deficiency first results in pale mottled leaves, followed by typical interveinal chlorosis. Under severe Mn deficiency dicots may also develop a number of brownish spots. In cereals, Mn deficiency can cause pale green or yellow patches in younger leaves. This condition is known as gray speck, and is characterized by necrotic spots that form in older leaves (Figure 1).

Figure 1: Soybean leaves with an adequate (A) and deficient (B-C-D) supply of Mn (Pictures: I. Cakmak)

Manganese deficiency symptoms in corn and wheat (Pictures: IPNI).

Physiological Functions

Manganese plays a key role in photosynthesis, as the photosystem II-water oxidizing system has an absolute Mn requirement (Hakala et al. 2006). Adequate Mn is critical in this system, as Mn facilitates the photolysis (light splitting) of water molecules and provides energy for photosynthesis. It is, therefore, not surprising that Mn deficiency substantially impairs photosynthesis, even in the absence of visual leaf symptoms. The negative effect of Mn deficiency in photosynthesis results in marked decreases in soluble sugar concentrations in different parts of plants (Figure 2). It is widely believed that the reduction in photosynthesis is the major reason behind the decline in dry matter production and yield under Mn-deficient conditions.

Figure 2: The influence of low and adequate Mn supply on soluble carbohydrate concentrations observed in the roots, stems and leaves of bean plants (redrawn from Marschner, 2012).

Tolerance to Pathogenic Infection

Lignin Synthesis

As a cofactor, Mn is reported to activate over 35 enzymes, several of which catalyze different steps of the lignin and phytoalexins biosynthesis. Impairment of lignin biosynthesis in Mn-deficient plants, especially in the roots, is associated with increased pathogenic attack, particularly soil-born fungi, because lignin serves as a barrier against pathogenic infection (Figure 3; Marschner 2012). Manganese application contributes to the resistance against not only various soil-borne diseases including take-all in wheat, common scab in potato and root rot in cotton, but also fungal leaf diseases such as tan spot in wheat, powdery mildew in grape and black leaf mold in tomato (Brennan 1992; Graham and Webb, 1991; Heine et al. 2011; Yao et al. 2012).

Peroxidase Enzyme

The peroxidase enzyme, which generates hydrogen peroxide, is another Mn-dependent enzyme that contributes to pathogen resistance. The hydrogen peroxide produced is not only involved in the stabilization of the cell wall, but is also thought to be directly toxic to pathogens (Heine et al. 2011), and therefore acts as a fungicide (Graham and Webb, 1991).

Stress Tolerance

Nearly all environmental stress factors represent an oxidative stress. Manganese plays an important role in improving stress tolerance, as superoxide dismutase enzymes, which are responsible for the detoxification of the destructive free radicals, require different metal cofactors, such as Mn, to function. Not surprisingly, increases in activity of Mn-superoxide dismutase contributed greatly to plant tolerance of different environmental stress factors such as winter hardiness, ozone stress, salinity and drought stress.

Figure 3: Effect of lignin concentration in the shoots and roots of wheat plants, as a function of Mn supply (redrawn from Marschner, 2012).

Manganese deficiency in plant tissues has also been reported to impair fatty acid production, which can adversely affect the cuticular wax deposition, as wax synthesis begins with fatty acid synthesis in plastids. Since the wax layer is responsible for limiting non-stomatal water loss and reducing the heat load on leaves (Hebbern et al. 2009), weakening of this layer due to Mn deficiency can cause an increase in the susceptibility of crops to both drought and heat stress. In barley, for example, latent Mn deficiency was found to significantly reduce the wax content (up to 40%), resulting in increased transpirational water loss and lower water-use-efficiency (Hebbern et al. 2009).

Conclusion

To sum up, prevention and correction of Mn deficiency by fertilization can:

  • Enhance the photosynthetic efficiency and dry matter production

  • Provide resistance to biotic stress by increasing plant resistance to various diseases and reducing the need for fungicides

  • Contribute to abiotic stress tolerance, particularly drought and heat

  • Result in significantly higher crop yield.

Readings

Alloway BJ. (2008) Micronutrients and Crop Production: An Introduction. In: Alloway BJ (Ed) Micronutrient Deficiencies in Global Crop Production. Springer, pp 1-40

Brennan RF (1992) The role of manganese and nitrogen nutrition in the susceptibility of wheat plants to take-all in western Australia. Fertilizer Res 31:35-41

Hakala M, Rantamaki S, Puputti EM, Tyystjarvi T, Tyystjarvi E (2006) Photoinhibition of manganese enzymes: insights into the mechanism of photosystem II photoinhibition. J Exp Bot 57:1809-1816

Hebbern CA, Laursen KH, Ladegaars AH, Schmidt SB, Pedas P, Bruhn D, Schjoerring JK, Wulfsohn D, Husted S (2009) Latent manganese deficiency increases transpiration in barley ( Hordeum vulgare). Physiol Plant 135:307-316

Marschner P (2012) Marschner’s Mineral Nutrition of Higher Plants (3rd ed). Elsevier Science

Yu Q, Osborne L, Rengel Z (1998) Micronutrient deficiency changes activities of superoxide dismutase and ascorbate peroxidase in tobacco plants. J Plant Nutr 21:1427-1437


What is manganese most responsible for? As an essential nutrient that’s usually tied to iron and other minerals, manganese plays a role in numerous chemical processes, including synthesis of nutrients like cholesterol, carbohydrates and proteins. Also importantly, manganese is involved in the formation of bone mass and helps balance hormones naturally that affect nearly every aspect of health.

Manganese is an important trace mineral needed for many vital functions, including nutrient absorption, production of digestive enzymes, bone development and immune-system defenses.

Manganese is present in the highest quantities in whole foods, including sprouted grains, legumes or beans, certain nuts, and seeds. To some extent, it’s also found in fruits and vegetables, although whole grains are usually considered the best natural source. Wherever manganese is found, iron is usually also present since these two work closely together.

Manganese also helps balance levels of calcium — helping fight calcium deficiency — and phosphorus, all of which work together in many crucial ways.

What Are the Risks for Manganese Deficiency and Toxicity?

Although a manganese deficiency is pretty rare in developed nations where people are generally not malnourished, a deficiency can cause serious health threats including bone loss, muscle and joint pain, and changes in mood.

Manganese deficiency is usually caused by a lack of manganese-rich foods in someone’s diet and sometimes by chronic digestive disorders that make it hard to absorb manganese.

Because the body tightly regulates the amount of manganese it holds through levels of absorption and excretion, humans maintain stable tissue levels of manganese in most cases. This is the reason manganese deficiencies are rare. (1)

When a manganese deficiency occurs, some of the most common symptoms of include:

  • weak bones (osteoporosis)
  • anemia
  • chronic fatigue syndrome
  • low immunity and frequently getting sick
  • worsened symptoms of premenstrual syndrome (PMS)
  • hormonal imbalances
  • impaired glucose sensitivity
  • changes in digestion and appetite
  • impaired reproductive abilities or infertility

Too much manganese, on the other hand, usually poses more of a threat, especially during development years when the brain is still forming. What is manganese toxicity capable of doing to someone’s health? Excessive accumulation in the central nervous system can cause birth defects and cognitive problems but is considered a low risk. (2)

Only a small percentage of dietary manganese is even actually absorbed, and the rest is excreted very rapidly into the gut via bile and then excreted — so trouble neutralizing and eliminating manganese due to existing liver, gut or digestive problems pose the biggest risk for acquiring too much manganese. At the same time, manganese is taken up from the blood by the liver and transported to tissues throughout the body, so liver damage can also cause a deficiency.

Recommended Daily Intake of Manganese

Currently, there isn’t any standard recommended dietary allowances for manganese. When there isn’t a USDA-regulated amount for a nutrient, an adequate intake (AI) is used instead as a guide for how much to consume each day. As with all nutrients, it’s always best to get enough manganese from whole food sources as opposed to supplements whenever possible. Whole foods contain the proper mix of different vitamins and minerals that work to balance one another and enable functioning.

The daily AI levels for manganese depend on someone’s age and gender and are listed below, according to the USDA:

Children:

  • Infants up to 6 months: 3 micrograms
  • 7 to 12 months: 600 micrograms
  • 1 to 3 years: 1.2 milligrams
  • 4 to 8 years: 1.5 milligrams
  • Boys 9 to 13 years: 1.9 milligrams
  • Boys 14 to 18 years: 2.2 milligrams
  • Girls 9 to 18 years: 1.6 milligrams

Adults:

  • Men age 19 and older: 2.3 milligrams
  • Women 19 and older: 1.8 milligrams
  • Pregnant women age 14 to 50: 2 milligrams
  • Breastfeeding women: 2.6 milligrams

11 Manganese Benefits

1. Supports Bone Health and Helps Prevent Osteoporosis

Manganese, in combination with other minerals, including calcium, zinc and copper, can help reduce bone loss, especially in older women who are more susceptible to bone fractures and weak bones. Manganese deficiency also poses a risk for bone-related disorders since manganese helps with the formation of bone regulatory hormones and enzymes involved in bone metabolism.

According to studies, taking manganese along with other bone-supporting nutrients like calcium, vitamin D, magnesium, zinc, copper and boron can improve bone mass in women with weak bones, which is useful to naturally treat osteoporosis. (3)

2. Needed for Antioxidant and Enzyme Function

Manganese is used in numerous important enzymes, including arginase, glutamine synthetase and manganese superoxide. These work as antioxidants in the body, helping lower levels of oxidative stress and inflammation that can lead to heart disease or cancer.

What is manganese most beneficial for when it comes to disease prevention? Manganese-deficient animals have been shown to have low manganese-related superoxide dismutase function, which can be harmful because this is one of the major free radical damage-fighting enzymes in the body. In fact, superoxide dismutase is sometimes called the “primary” or “master antioxidant” since it’s especially powerful at reducing inflammation, pain and bodily stress that can lead to numerous chronic diseases. (4) Superoxide dismutases (SODs) are the only enzymes capable of consuming superoxide radicals, making them valuable for slowing the aging process and prolonging health.

Manganese also helps form important enzymes related to bone formation, including glycosyltransferases and xylosyltransferases. And finally, manganese plays a part in important digestive enzymes that turn compounds found in food into useable nutrients and energy within the body, including glucose and amino acids.

3. Helps Maintain Cognitive Function

A percentage of the body’s manganese supply exists in the synaptic vesicles within the brain, so manganese is closely tied to electrophysiological activity of the brain’s neurons that control cognitive function. Manganese is released into the synaptic cleft of the brain and affects synaptic neurotransmission, so it’s possible that a manganese deficiency can make people more prone to mental illness, mood changes, learning disabilities and even epilepsy. (5)

4. Fights and Damages Diabetes

Manganese is needed to help with proper production of digestive enzymes responsible for a process called gluconeogenesis. Gluconeogenesis involves the conversion of protein’s amino acids into sugar and the balance of sugar within the bloodstream. Although the exact mechanism still isn’t clear, manganese has been shown to help prevent overly high blood sugar levels that can contribute to diabetes.

When researchers from the Department of Internal Medicine and Biochemistry at the Veterans Affairs Medical Center tested the effects of manganese supplementation in mice that were susceptible to diet-induced diabetes, they found that the group of mice given manganese over 12 weeks experienced improved glucose tolerance compared to mice not taking manganese. The manganese-treated group exhibited improved insulin secretion, decreased lipid peroxidation and improved mitochondrial function. (6)

5. Supports Lung and Respiratory Health

Research suggests that manganese taken along with minerals like selenium and zinc can help people suffering from lung disorders, including chronic obstructive pulmonary disease. Oxidative stress is believed to be a key mechanism for smoking-induced chronic obstructive pulmonary disease and other respiratory disorders, so manganese’s ability to help lower inflammation and oxidative stress through the production of SODs makes it beneficial for those in need of lung healing.

6. Helps Prevent Arthritis and Osteoarthritis

Manganese, along with supplements containing glucosamine hydrochloride or chondroitin sulfate, makes it a recommended natural treatment for arthritis. Regularly eating foods high in manganese, plus possibly taking supplements, can help reduce inflammation in the joints and tissue, allowing arthritis sufferers to feel more comfortable and do more normal activities. Manganese has been sown to be especially helpful with reducing common pains in the knees and the lower back.

7. Reduces PMS Symptoms

Consuming plenty of manganese along with calcium can help improve symptoms of PMS — such as tenderness, muscle pain, anxiety, mood swings and trouble sleeping — and work as a natural remedy for PMS. One study published in the American Journal of Obstetrics and Gynecology found that women who have lower levels of manganese in their blood experienced more pain and mood-related symptoms during pre-menstruation. (7)

8. May Help with Weight Loss

Some early research points to the fact that manganese, taken in a specific form called 7-Keto Naturalean, combined with other supportive nutrients like L-tyrosine, asparagus root extract, choline, copper and potassium, may be able to help reduce weight in obese or overweight people. More research is still needed to determine how manganese supports healthy weight loss and metabolism, but it’s likely related to manganese’s ability to improve digestive enzymes and balance hormones.

9. Speeds Up Wound Healing

By applying manganese, calcium and zinc to serious and chronic wounds, studies show that wound healing can speed up significantly over a period of 12 weeks. (8)

10. Helps Balance Iron Levels and Prevent Anemia

Iron and manganese work closely together, and a strong inverse relationship between deficiency in iron and high manganese levels has been found. While overly high manganese can contribute to anemia, manganese also helps the body use and store iron to some degree as well, which can help prevent anemia (low iron).

11. Prevents Infertility

Manganese deficiency can contribute to infertility since manganese helps with hormone regulation and antioxidant activity, thus manganese works as a natural infertility treatment.

Best Food Sources of Manganese

Percentages based on the adult women’s AI of 1.8 milligrams/daily:

Related: Natto: The Fermented Soy Superfood

Are There Any Interactions or Concerns with Manganese?

Manganese “toxicity” is possible, although it’s rare. Most adults are safe taking and consuming up to 11 milligrams of manganese each day, but in some cases certain people aren’t able to flush manganese from the body properly and high levels can accumulate.

In healthy adults, it’s extremely unlikely to consume too much manganese from food source alone; rather people usually take in too much manganese when taking certain supplements. Supplement products promoted for osteoarthritis, for example, can include high levels of manganese in the form of chondroitin sulfate and glucosamine hydrochloride, which can bring someone’s intake above the tolerable upper limit (UL) for adults, 11 milligrams of manganese per day.

Other people who should avoid manganese supplements or speak with a doctor first include those with existing liver disease, who likely have trouble getting rid of manganese, and people with a history of alcoholism or anemia. Manganese can build up in these people and cause side effects, including mental problems, dizziness and shaking, and worsened liver disease. People who have existing iron deficiency (anemia) are also likely to absorb higher levels of manganese so they need to be cautious about their consumption rate.

Consuming more than the UL of 11 milligrams per day of manganese can possibly cause side effects, even some that are serious and very harmful, such as neurological disorders like Parkinson’s disease. Always make sure to check supplement labels carefully and follow the dosage directions. Before taking high dosages of manganese, or any other mineral or nutrient, you might also want to have your current level checked by your doctor to confirm how much you need via supplements, if any.

Manganese-Rich Recipes

Brown Rice Salad Recipe

Total Time: 5 minutes

Serves: 4–6

INGREDIENTS:

  • 3 cups cooked brown rice
  • 1 apple, diced
  • 1 red bell pepper, chopped
  • 2 celery stalks, chopped
  • ½ cup walnuts, chopped
  • 3 tablespoons parsley, chopped
  • ¼ cup coconut vinegear
  • 3 tablespoons coconut oil
  • Sea salt and black pepper to tastte

DIRECTIONS:

  1. In a bowl, combine cooked rice with all ingredients. Mix lightly and serve.

Hummus Recipe

Total Time: 5 minutes

Serves: 8–12

INGREDIENTS:

  • 2 cans garbanzo beans
  • 1/4 cup raw sesame seeds
  • 1 tablespoon olive oil
  • 1/4 cup lemon juice
  • 1 garlic clove, peeled
  • 1 teaspoon cumin
  • Sea salt to taste

DIRECTIONS:

  1. Drain and rinse garbanzo beans, reserving 1/4 cup liquid. Place all ingredients in a blender and blend. Add more water or olive oil until desired consistency is reached.

Black Bean Brownies Recipe

Total Time: 55 minutes

Serves: 9–12

INGREDIENTS:

  • 1 can (15 ounces) black beans, drained
  • 1/2 cup cacao powder
  • 4 tablespoons coconut oil melted
  • 3/4 cup raw honey
  • 2 teaspoons stevia
  • 1 teaspoon vanilla extract
  • 3 eggs
  • 1/2 cup gluten-free flour
  • 1/4 teaspoon sea salt
  • 1/4 cup water

DIRECTIONS:

  1. Blend all ingredients together.
  2. Grease 8 x 8 pan with coconut oil.
  3. Bake for 40 minutes at 350 degrees.
  4. Allow to cool for 10–15 minutes.

Read Next: Power Mineral: Phosphorus Helps Your Body Detox & Strengthen

The Role Of Manganese In Plants – How To Fix Manganese Deficiencies

The role of manganese in plants is important for healthy growth. Keep reading to learn more about how to fix manganese deficiencies to ensure the continual health of your plants.

What is Manganese?

Manganese is one of nine essential nutrients that plants require for growth. Many processes are dependent on this nutrient, including chloroplast formation, photosynthesis, nitrogen metabolism and synthesis of some enzymes.

This role of manganese in plants is extremely crucial. Deficiency, which is common in soils that have neutral to high pH or a substantial deal of organic matter, can cause serious problems with plants.

Manganese and Magnesium

It’s necessary to note the difference between magnesium and manganese, as some people tend to get them confused. While both magnesium and manganese are essential minerals, they have very different properties.

Magnesium is a part of the chlorophyll molecule. Plants that are lacking in magnesium will become pale green or yellow. A plant with a magnesium deficiency will show signs of yellowing first on the older leaves near the bottom of the plant.

Manganese is not a part of chlorophyll. The symptoms of manganese deficiency are remarkably similar to magnesium because manganese is involved in photosynthesis. Leaves become yellow and there is also interveinal chlorosis. However, manganese is less mobile in a plant than magnesium so that the symptoms of deficiency appear first on young leaves.

It’s always best to get a sample to determine the exact cause of the symptoms. Other problems such as iron deficiency, nematodes, and herbicide injury may also cause leaves to yellow.

How to Fix Manganese Deficiencies

Once you’re sure that your plant has a manganese deficiency, there are a few things that can be done to fix the problem. A foliar feed fertilizer with manganese will help to alleviate the issue. This can also be applied to the soil. Manganese sulfate is readily available at most garden centers and works well for this. Be sure to dilute any chemical nutrients to half strength to avoid nutrient burn.

Generally, application rates for landscape plants are 1/3 to 2/3 cup of manganese sulfate per 100 square feet. The per-acre rate for applications is 1 to 2 pounds of manganese sulfate. Prior to use, it may help to thoroughly water the area or plants so that the manganese can be absorbed more easily. Read and follow application guidelines carefully for best results.

Identifying nutritional deficiencies in backyard plants

Fertilisers

When applying fertilisers a well balanced general purpose product containing both essential and trace elements is recommended. Trace elements are required in small amounts and should be used sparingly.

On sandy soils small amounts of fertiliser should be used frequently, to ensure a steady supply of nutrients to the plant. A time saving alternative is to use controlled release fertilisers. On heavier soils apply fertiliser in greater quantities, but less often.

Gardenia leaf showing iron and manganese deficiency.

Plants can also suffer from nutrient toxicity if too much of a particular nutrient is applied. Water plants before fertiliser application and ensure the fertiliser is watered in well after application, to avoid burning of the plants.

Liquid fertilisers or trace elements in a liquid form, applied to the foliage of the plant, are one of the quickest ways of solving nutrient deficiencies.

Deficiency symptoms

Nitrogen

Nitrogen is a necessary element for leaf growth and blossom formation. It is an important component in chlorophyll which is essential for photosynthesis. If nitrogen is deficient, the oldest leaves appear pale and lack the lustre of healthy ones. Yellowing appears at leaf tips and will affect all the leaves. Apply fertilisers high in nitrogen such as sulphate of ammonia or blood and bone. Organic matter and manures can also be added to the soil.

Phosphorus

Phosphorus is essential for the development of flowers, fruit and roots. It is a mobile nutrient and is moved from older leaves to the newly developing tissue. Older leaves turn a darker green followed by a purplish tint starting from the leaf margins. Leaf tips dry off. In fruit trees, flowering and fruiting may be affected. Deficiency symptoms are more prevalent during cold, wet conditions. To correct the deficiency apply solid or liquid phosphate fertilisers.

Potassium

Potassium is also required for flower and fruit formation and thickening of cell walls. It is essential for the lengthening of stems. Mature leaves show a browning and drying of the upper surface and puckering on the margins. Darkening appears between the leaf veins. The stalks are thin and shortened. The fruits may fail to develop full colour, be pulpy in texture and lack flavour. To correct the deficiency apply sulphate of potash.

Magnesium

Magnesium is essential for photosynthesis and the formation of proteins and chlorophyll. It moves freely within the plant and is taken from the older leaves to supplement new growth. Lower leaves are first affected, yellowing from the tip downwards. Dead spots appear. Deficiencies occur on sandy acid soils and affect palms and citrus. To correct the deficiency apply magnesium sulphate (Epsom salts) or dolomite (magnesium-calcium-carbonate).

Manganese deficiency on a cycad leaf.

Zinc

Citrus trees suffering from a zinc deficiency show yellowing between the leaf veins, rolling of the margins and smaller leaves than normal. Zinc becomes unavailable in soils which have high pH. It is not a very mobile nutrient so a foliar spray of zinc and manganese is recommended for fruit set.

Iron

A condition often referred to as lime induced chlorosis affects acid loving plants that are unable to take up iron in alkaline soils. The newer leaves become pale green, yellow and, in severe cases, white. Veins remain green. This is a common occurrence on coastal alkaline soils. To correct the deficiency reduce the pH of soil with ammonium sulphate or agriculture sulphur, and apply iron sulphate. A foliar feed with a complete liquid fertiliser will help correct this problem.

Manganese

Manganese deficiency causes yellowing between the veins of new foliage. In extreme cases new palm fronds emerge withered and dead. This is referred to as frizzletop, and commonly occurs on alkaline soils. To correct the deficiency apply manganese sulphate. During summer yellowing appears on cycads as manganese is diverted from older fronds to support a flush of new growth. Yellow spots merge into a mass. A spray with the fungicide mancozeb, which contains manganese, is beneficial. This deficiency can appear on either new or older leaves.

Sulphur

Sulphur is a component in the formation of chlorophyll. Deficiencies result in yellow leaves and stunted growth. Sulphur can be used to lower the pH of alkaline soils. To correct the deficiency apply sulphur fertiliser such as sulphate of potash or ammonium sulphate rather than agricultural sulphur.

Calcium

Symptoms are more prevalent on the fruits than on the leaves. Fruits like tomatoes, plums and olives show a blemish on the blossom end of fruit. To correct the deficiency, apply calcium nitrate early in the season.

Iron and manganese deficiency on acid preferring plants

Symptoms show yellowing between the veins, which remain dark green. This is a common condition in soil with a high pH, and particularly on citrus, roses and gardenias. To correct the deficiency add iron sulphate or iron chelate and manganese sulphate to the soil.

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