Posts Tagged ‘manganese’

Yellow Cantaloupe Leaves

Friday, August 10th, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist;

Each year we see problems with cantaloupe leaves turning yellow. There are several potential causes. If the yellowing is on leaf edges it most commonly is due to salt effects and fungicides, see the article by Jerry Brust two weeks ago for more details Copper fungicides are often the culprit in this leaf yellowing, causing a phytotoxic reaction. Foliar fertilizer applications can often worsen the yellowing by increasing salt levels on the leaves.

Each year there are some fields of cantaloupes that are affected by manganese toxicities. This occurs when bed pH drops below 5.4 which affects soil chemistry so that plant available manganese increases greatly and plants take up quantities that become toxic. As a micronutrient, Manganese is needed in only small amounts and the sufficiency range is between 20-100 ppm. Magnesium deficiencies also can occur at low pH and older leaves will show interveinal chlorosis. These symptoms can be confused with mite damage so check for mites in the diagnostic process.

Air pollution is another cause of yellowing of cantaloupe leaves. This yellowing is usually confined to older crown leaves.

Cantaloupe leaves showing signs of salt injury, copper fungicide phytotoxicity and managanese toxicity. Bed pH was 5.4.

Manganese Deficiency on Corn as Related to Soil Organic Matter

Friday, June 24th, 2011

Richard Taylor, Extension Agronomist; and Phillip Sylvester, Kent Co., Ag Agent;

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;

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.


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

Thursday, April 14th, 2011

Richard Taylor, Extension Agronomist; and Phillip Sylvester, Kent Co., Ag Agent;

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.


Manganese Deficiency Can Worsen with Spring N Applications on Small Grains

Friday, April 8th, 2011

Richard Taylor, Extension Agronomist; and Phillip Sylvester, Kent Co., Ag Agent;

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.