Calcium Products - Are you seeing uneven tasseling/flowering in corn?
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Are you seeing uneven tasseling/flowering in corn?

Over the past week I have driven from Minneapolis, MN to Topeka, KS. I am seeing more delayed and uneven tasseling/flowering this year then I have for a number of years.

To achieve high yields it is vitally important that silking and tasseling (flowering) happens all at once.

Could uneven flowering be a sign that your corn is sulfur deficient?

Determining if sulfur is deficient

If you follow this blog you know sulfur deficiency can result in a general yellowing of the plant in corn, as interveinal chlorosis, similar to magnesium or zinc deficiency. Sulfur is not easily translocated in plants, so symptoms will appear first and be most pronounced on the younger, upper leaves. Deficiencies of mobile nutrients such as nitrogen will appear first on the lower leaves as nutrients are remobilized to growing plant tissues. 

Sulfur deficiency symptoms follow a similar pattern in other crops such as soybean, wheat, canola and alfalfa, with yellowing of the plant in the youngest tissue. In canola, early season deficiency symptoms include yellowing between leaf veins, cupped leaves and stunting. Late season symptoms are slender, cupped leaves that may be purple along the edges, delayed flowering and pale yellow or white flowers.

Sulfur deficient canolaI have had the opportunity to work with canola growers over the last year. The one thing that really stands out in canola is that sulfur deficiency affects rapidly growing parts, especially reproductive structures. Since sulfur has a low mobility within the plant, symptoms are usually observed early in the season on the youngest leaves which are greenish-yellow compared to the normal bluish-green. If sulfur deficiency occurs around flowering, leaf symptoms may not be obvious, but flower petals may become paler. Yellow and white petals may even exist side by side on a single flower. (See the photo: flower on the left was treated with SuperCal SO4, control on the right)

The lifespan of sulfur deficient petals is shortened to one day instead of two or three, and pollen production is greatly reduced. In addition, sulfur deficient petals are egg-shaped compared to more round petals on plants with sufficient sulfur. By podding, sulfur deficiency becomes more distinctive. Pod number and size and seed number per pod are reduced significantly. Pods may be pale green, often with purpling and can be compressed or flattened. Sulfur deficiency can lead to a big reduction in yield and quality, namely a reduction in oil and protein.

Canola isn’t corn, but is this what we are seeing in this year's corn crop?

Delayed TasselingI have had trouble finding scientific journal relating flowering in corn and sulfur fertilization. However last year we delayed flowering in our trials. (picture at right: SuperCal SO4 trials on the left; control on the right).

Historically, sulfur deficiencies were thought to be a concern strictly on sandy soils, but in recent years, deficiencies have become more prevalent across a variety of soil types. Sulfur deficiencies may appear on hilltops or slopes where soils are eroded and low in organic matter soils. Sulfur deficiency symptoms are typically not uniform across the field, more often appearing in spots or streaks due to field variability. Symptoms may also appear in places where soils are colder or wetter, such as low spots or high residue areas. This is because the rate of sulfur mineralization and the supply of available sulfate are reduced in those areas.

A key component of sulfur for plant growth is the soil mineralization path. The amount of sulfur released from residues will depend on soil organic matter. Plant residues are decomposed by soil microbes, releasing sulphate. Like nitrogen, the sulfur mineralization rate is quite slow, and can not match the uptake rate of growing plants. Sulfur oxidizing bacteria are most active under warm, moist, well-aerated conditions.

So are we seeing uneven flowering due to the drought or from lack of available sulfur?

The answer is likely both. Sulfur may not be available to the plant due to the dry conditions. It is also in lower supply due to clean air laws. While this is a topic that definetly needs more research, be sure to make sure that your start your crop off right by supplying, at the least, grain removal rates of a good sulfate sulfur fertilizer like SuperCal SO4.


Yield Starts Here is a blog for farmers, focusing on increasing yield and profitability by focusing on the soil. It is managed by Craig Dick, a Blogronomist and Sales and Marketing Manager at Calcium Products. Find other articles by Craig and guest writers at .

Additional Info

  • Article Reference:: Calcium Products, Inc.
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