Posts tagged ‘foliar fertilizer’

Short Soybeans and Possible Yield Implications

This post is reblogged from the outstanding article written by Chad Lee, University of Kentucky

Some farmers are concerned that the smaller growth of soybeans could result in reduced yields. Some are questioning the use of foliar fertilizers and/or fungicides to help make up the difference. Soybeans were planted late across the area. Most farmers’ and agronomists’ (including my own) “internal clock” says that soybeans should be larger by now. Most years, that is correct. This is not most years.

Taken by A. Kleinschmidt July 27, 2009

Taken by A. Kleinschmidt July 27, 2009

What a difference a year makes! Notice last year’s soybeans below.

Taken by A. Kleinschmidt July 22, 2008

Taken by A. Kleinschmidt July 22, 2008

Some soybeans are flowering, growth stage R1, and some soybean are beyond that stage. The cooler temperatures combined with later planting dates will cause smaller plants. The smaller plants could be a concern if rows are not closed in shortly after flowering. If the rows are not closed and the soybeans begin to flower, then yield potential is likely lost. This brings us to the main question: will a foliar fertilizer or a foliar fungicide help? The short answer…probably not.

Fungicides will not improve the speed at which soybeans grow and will not help with canopy closure, in the absence of a disease. Fungicides will help soybeans retain leaves, especially if a disease is present in the field. However, the cooler night temperatures and the smaller soybean plants both contribute to less of a threat from diseases this season. Foliar fertilizers will not compensate for lower temperatures. They will not increase the speed of growth, assuming P2O5 and K2O levels are adequate in the field. They will make the plants greener and that might make someone feel better.

If you are absolutely set on spraying something, then consider a foliar fertilizer. It will likely make the plants greener and it should cost a little less than the fungicide. The bottom line is that small soybeans or late-planted soybeans that do not reach full canopy by flowering probably have lost some yield potential. Cooler temperatures also reduce the chances of soybeans reaching full canopy by flowering. Foliar fertilizers and fungicides will not make up the difference in temperatures, planting date or row spacing. However, a foliar fertilizer may alleviate some of the yellow soybean symptomology we are experiencing, although that application may not necessarily translate into increased yields.

Full podcast here:


July 29, 2009 at 8:10 am

Yellow Soybeans: What is the Cause?

You don’t have to drive too far to see patches, or small areas, within a soybean field that show yellow soybeans.  Here are the typical symptoms:

1. Generally, the areas in the field are small–perhaps a circular area with a diameter ranging from 25′ to >75′

This is a typical yellow area currently observed in some soybean fields.

This is a typical yellow area currently observed in some soybean fields.

2. The uppermost leaves are affected–that is, the symptoms show up only on the newest growth on the soybean plant

The newest growth of soybeans clearly shows the symptomology.

The newest growth of soybeans clearly shows the symptomology.

3. The uppermost leaves have interveinal chlorosis–the veins are green or dark green and the leaf area between the veins is yellow or very light yellow.

Interveinal chlorosis: green veins and yellow leaf tissue.

Interveinal chlorosis: green veins and yellow leaf tissue.

Robert Mullen, Keith Diedrick and Ed Lentz wrote an excellent article in the July 7, 2009 CORN Newsletter providing an overview of yellow soybeans and diagnosis. There are a few things you can do to verify the presence of a nutrient deficiency.  Mullen recommends the following: tissue sampling, soil sampling, and root observation.

  • Tissue sampling: sample the uppermost, fully-expanded trifoliate and discard the petioles (small stem that connects the trifoliate to the main stem). Collect samples from an unaffected area as well as the affected area.
  • Soil sampling: collect corresponding soil samples from the unaffected area and the affected area at a depth of 8″, unless in no-till or severely reduced tillage.  In no-till or very minimum tillage operations, sample the profile at the 0-4″ zone and at the 4-8″ zone.
  • Root observation: By doing a root observation, we are specifically looking for soybean cyst nematode (SCN). These SCN structures will appear as tiny, lemon-shaped objects on the roots that range in color from white, yellow, tan and brown. They are easy to see with slight magnification (a field lens works fine). The cysts are about the size of a pinhead and considerably smaller than nitrogen nodules. You must carefully remove the soil as not to dislodge the SCN structures.

So what to do? In some cases an application of 1-2 qt. per acre of a liquid manganese product can alleviate the visual symptoms.  However, this may not translate in to a positive return on yield.  Research was conducted in 2004 examining this very problem.  Research results are available here:

Full podcast available here:

July 22, 2009 at 8:00 am


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