Posts Tagged ‘field corn nutrient management’

Sulfur Deficiency in Corn

Friday, June 1st, 2012

Richard Taylor, Extension Agronomist;

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; 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.


Dryland Corn and Nitrogen Sidedressing

Friday, June 3rd, 2011

Richard Taylor, Extension Agronomist;

I was asked recently for thoughts on sidedressing corn during the recent heat we’ve been experiencing. I thought I would share some arcane, although still relevant, information from my soil fertility and plant nutrition class at the University of Delaware. This concerns an old proven principle called (by me at least) the Sprengel-Liebig Law of the Minimum. Essentially what P. Carl Sprengel in 1828 and J. von Liebig, also, in the 1900s stated in various papers they published was that yield will be determined by whatever factor is most limiting to the crop.

For growers who irrigate their corn, chances are that the limiting factor will be something other than water availability. It may be a disease that impacts grain fill or it may be a lack of one of the essential nutrients or even a lack of enough sunlight during the growing season. We often see the latter in years where it’s cloudy or hazy for much of the summer. With respect to nitrogen (N) sidedressing, irrigated growers can easily apply a small amount of water to incorporate the N into the soil and therefore prevent ammonia volatilization losses from the urea component of the UAN (urea-ammonium nitrate) solution.

However for dryland corn producers who may feel the need to sidedress N on their rapidly growing corn crop, what likely is the most yield limiting factor their crop faces. Is it N availability? No in my opinion, the most limiting factor will always be water availability throughout the growing season. If it isn’t the total amount of N, it will be the distribution of the rainfall/moisture during the growing season. For these producers, the decision to sidedress N will come down to the speed of corn growth versus their ability to cover all the corn acreage before the corn runs out of starter N or becomes too tall to sidedress without causing crop damage.

Within the activity of sidedressing, there are some choices to minimize N loss as ammonia volatilization such as knifing in the UAN, using anhydrous ammonia rather than UAN, or using one of the urease inhibitors. Some of the old research suggests only about a 7 to 10 percent loss in N from dribbling the UAN solution on the soil surface. Even with this amount of loss, your most limiting yield factor will still be water availability throughout the growing season.


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.


Will Your Crop Suffer from Sulfur Deficiency this Cropping Year?

Friday, March 11th, 2011

Richard Taylor, Extension Agronomist;

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.

Assessing Nitrogen Status in Corn

Thursday, August 6th, 2009

Gordon Johnson, Extension Ag Agent, Kent Co.;

This has been a challenging year with excess moisture until mid-June. It was difficult to get on some fields and even more difficult to determine how much nitrogen (N) to sidedress, especially in fields with significant water damage or replant acreage. In looking at many fields, I can see some lower leaves that have yellowed or browned, indicating N deficiency. Did you have enough N? The following is some information to consider from Penn State University.

“Research done in central and southeastern PA has shown that when 4–5 green leaves are present at and below the corn ear leaf there is no N deficiency over 95% of the time. This research went on to state that of those plants with less than 4 green leaves only 50% were N deficient. Therefore, at harvest time brown leaves can be present on a perfectly healthy plant. Additionally, a plant that is green the whole way to the ground may have had N over applied, an expensive mistake that should be accounted for next year.”

The end-of-season corn stalk nitrate test would be a good tool to use to see if adequate N was available for your corn crop this year with the wet spring and delayed sidedressing in many fields. It is also very useful for evaluating N fertigation programs in irrigated corn. It is used to assess the N status of a corn crop at the end of the growing season. The following is more information on this test from a UD fact sheet on the subject.

Basis of the Corn Stalk Nitrate Test
Corn plants that do not have an adequate supply of available N in the soil translocate N from stalks and leaves to the grain during the grain-filling period. Under conditions of extreme N-deficiency, this translocation of N results in pale or “yellowed” plants. However, corn plants can experience yield-reducing deficiencies of N without showing obvious visual symptoms. On the other hand, corn plants that have more N than needed to achieve maximum yields tend to accumulate N in their leaves and lower stalks. This may result in plants that appear dark green. However, visual differences between plants with adequate N and plants with excessive N usually are not apparent. Where visual differences are apparent, they are often not related to differences in grain yields.

The end-of-season corn stalk nitrate test makes use of the fact that corn plants either remove N from, or accumulate N in, the lower stalk based on soil N availability. Studies over a wide range of conditions have found remarkably similar relationships between the amount of N found in the lower stalks late in the growing season and the likelihood that corn has been under or over-fertilized.

Collecting Corn Stalk Nitrate Samples
Corn stalks should be sampled at least one week after black layers have formed on about 80% of the kernels of most ears. Sampling can be performed up to harvest. Areas selected for sampling should be on a uniform soil type and management history.

Collect the corn stalk samples by cutting the 8-inch segment of stalk found between 6 and 14 inches above the soil. Leaf sheaths should be removed from stalk samples. Severely damaged or diseased stalks should be avoided. Fifteen 8-inch segments should be collected from every 10 acres of corn and combined to form a single sample.

Corn stalk samples should be shipped immediately to a soil and plant testing laboratory that is familiar with this test. University of Delaware Cooperative Extension can assist in locating reliable testing laboratories. The stalk samples should be stored in paper bags, not plastic, to allow for some drying and to minimize the growth of mold. Samples that cannot be shipped to the testing lab within 24 hours should be refrigerated until shipping.

Interpreting Corn Stalk Nitrate Test Results
The concentration of nitrate in stalks at the end of the season is a consequence of all the factors that influenced growth during the season; not just N management. For this reason, care must be taken when interpreting the results of the stalk nitrate test. For example, any factor that limits crop yields, such as unusually wet or dry weather, may result in high concentrations of nitrate in corn stalks. The same may be true when yields are limited by deficiencies in other essential plant nutrients

The amounts of N in corn stalks are commonly expressed as concentrations of nitrate-N in parts per million (ppm). These concentrations can be divided into four ranges:

Low (< 250 ppm): Stalk nitrate concentrations in the Low range indicate a high probability that additional fertilizer or manure N would have resulted in higher yields. Visual signs of N deficiency usually are obvious when nitrate concentrations are within this range.

Marginal (250-700 ppm): Stalk nitrate concentrations in the Marginal range indicate that N availability was very close to the minimal amount needed to maximize grain yields. Visual signs of N deficiency are less common when nitrate concentrations are in this range. Although yields usually are not adversely affected by N deficiencies of this magnitude, this range is too close to the economic penalties associated with N deficiencies to be the target for good N management.

Optimum (700-2000 ppm): Stalk nitrate concentrations in the Optimum range indicate a high probability that the amount of soil, fertilizer, and manure N available during the growing season was sufficient to maximize profits for the producer.

Excessive (> 2000 ppm): Stalk nitrate concentrations in the Excessive range indicate a high probability that the amount of fertilizer or manure N applied was greater than necessary to maximize profits for the producer. Nitrate leaching to ground waters is a serious concern when corn stalks have nitrate concentrations in the excessive range. Nitrogen management practices used this year should be reviewed carefully and modified in the future to avoid over-fertilization with N which is uneconomic and can contribute to nonpoint source pollution of ground and surface waters.

After appropriate consideration of weather and other factors, fertilizer and manure rates should be increased on fields that usually test below the optimal range and decreased on fields that usually test in the excessive range. The test does not, at present, directly indicate how much N rates should be increased or decreased for a given stalk nitrate concentration. However, use of the test for several years will allow corn producers to identify N management practices, including rates, forms, and times of application, that tend to result in optimum amounts of plant-available N.

The University of Delaware is currently conducting research to further refine the stalk nitrate test.

Information from a factsheet prepared by Dr. David Hansen, Dr. Greg Binford, and Dr. Tom Sims, Department of Plant and Soil Sciences, College of Agriculture and Natural Resources, University of Delaware. Information on the Penn State research is from the current edition of the Penn State Field Crop News.