Posts filed under ‘fertilizer’

Winter Application of Phosphorus and Potassium to Farms

The following appeared in the January 26, 2010 edition of the CORN Newsletter:

A lot of fertilizer has been going on fields in the last couple of weeks, and though it is certainly not an optimal time, there is one advantage to application now with the wet autumn in 2009: compaction is minimized on frozen soils compared to saturated ones. However, just like manure applications on frozen or snow-covered ground, the possibility of commercial fertilizers moving off-site in runoff increases greatly when P and K do not migrate into the soil profile (perhaps more so since commercial P and K sources are water soluble by design). Environmental concerns notwithstanding, fertilizer inputs are a significant part of a crop enterprise budget, and losses from the field equate to losses on a balance sheet.

Consider if an application of P and K to particular fields is even necessary by checking a recent soil test against the Tri State Fertilizer Recommendations for the planned crop and crop rotation. Also strongly consider an application setback from sensitive areas (ditches, waterways, streams, etc.) of at least 200 ft, especially on sloping land where surface movement is accelerated. For more information, there is an Extension Fact Sheet on phosphorus best management practices available online:

Full podcast here:

February 3, 2010 at 11:55 am

OSU Agronomists Recommend Fertilize Now, Avoid Frozen Ground

Reblogged from the November 10, 2009 OSU CORN Newsletter

As you continue to harvest crops, plan on getting your fertilizer down this fall prior to frozen ground setting in or plan on waiting until spring after the thaw. Considering the number of acres that did not receive phosphorus or potassium last year with the prices we were facing, some of you may be in a situation where soil test indicates that you should make the application this year. If that describes your situation there is still time to make your applications this fall. The reason we would rather see applications made this fall is because we do not want to make applications on frozen ground. Applications made to fields with any appreciable slope can result in significant fertilizer losses. Not only do these losses represent an environmental concern, but they also represent an economic loss for your operation. Remember, if you soil test levels are still above our current critical levels (60 pounds per acre phosphorus, and 175-300 pounds of potassium, depending on soil CEC) then your risk of yield loss is small. Thus, you still do not have to make an application for next summer’s crops.

Another issue that producers are bring up is our current phosphorus and potassium recommendations and critical levels. Since at least some producers avoided applications of phosphorus and potassium last year and the crop season was as successful as it has been, growers question if our recommendations are too high. The Tri-State Fertilizer Recommendations are designed to ensure that phosphorus and potassium are not limiting production based upon soil test. A soil test value below the critical does not guarantee a yield loss, so those fields with low tests that performed well may have been those instances where enough phosphorus and potassium was made available (due to chance and weather) to allow for a relatively high yield. Additionally, since no fertilizer was supplemented, we do not know how much yield could have been made with an application (some yield may have been lost, but we have no way of measuring it without non-limiting control treatments replicated in the same field). Operating on low soil test levels is a risky venture, especially with potassium. We have documented yield losses of 35% and 50% on soils with below-critical phosphorus and potassium, respectively. You may be able to produce great yields on soils with low soil test levels, but the one time you do not will be a year you will remember.

November 13, 2009 at 1:19 pm

Tips for Fall Application of Phosphorus and Potassium

University of Illinois’ the Bulletin published an excellent article on September 4, 2009 regarding phosphorus and potassium recommendations. I’ll distill that article into key points for you here.  The past three years have seen incredible price jumps in phosphorus and potassium, and even though prices have retreated there is still very high interest in phosphorus and potassium fertilization. In fact, I cannot recall a time when farmers and agronomists have placed so much interest in phosphorus (P) and potassium (K) fertilization.

Over the past few years, there are some familiar questions that I hear over and over;

Do I need to apply P and K?

How much P and K should I be applying?

Which is better, one application every two years or should I apply every year?

Is it better to apply P and K in fall or spring?

The Tri-State Fertilizer Guide tells us that the absolute first place to begin with regards to answering these questions is with a soil test. A soil test is the only tool currently available to let us know the P and K status of our soils as it relates to a crop.

When soil tests are below the critical level (Figure 1), the soil is not able to supply the P and K requirements of the crop. Soil tests below the critical level should be considered as indicating a soil that is nutrient deficient for crop growth and recommended rates of fertilizer should be applied annually. Placement techniques to enhance nutrient availability, such as fall strip tilling, may also be beneficial on nutrient-deficient soils.

Above the critical soil test level, the soil is capable of supplying the nutrients required by the crop and no response to fertilizer would be expected. Recommendations for soil test values on the maintenance plateau are designed to replace the nutrients lost each year through crop removal. Because the purpose of fertilizer applications in the maintenance plateau range is to maintain fertility, no response to fertilizer in the year of application would be expected. Therefore, farmers may choose to make multiple year applications.

When soil test levels exceed the maintenance plateau level, the objective of the fertilizer recommendation is to utilize residual soil nutrients. Fertilizer recommendations are rapidly reduced from maintenance levels to zero. There is no agronomic reason to apply fertilizer when soil tests are above the maintenance plateau level.

Full podcast here:

September 9, 2009 at 8:15 am

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

Inspect Farm Poly Tanks

Dr. Fred Whitford, Purdue University, has provided some research in the area of farm poly tank longevity.  He recommends taking a baseball bat to your empty farm poly tank this spring prior to using your tank this year.  Many of the poly tanks used for transporting pesticides and fertilizer can be quite old, and poly tanks are not meant to last a lifetime. In addition, some tanks may be used for pusposes which they were not desinged.  For example, it is very common to see vertical storage tanks strapped to a flatbed and transported.  Vertical storage tanks are not designed for transport, and this presents a risk especially if that tank is carrying fertilizer or pesticide.

Dr. Whitford also recently released a very nice publication with pictures and demonstrations about this topic. The publication is available online from Purdue at:

After hitting the empty tank with a baseball bat, inspect the tank visually.  If the tank splits or cracks, it is obviously not suitable for use this spring. After striking the tank, one should take a water soluble pen (dry erase marker) and cover the area with ink where the bat impacted the tank. Immediately wipe the area with a cloth rag.  A tank that is still in good shape will not show crazing (a checkered pattern) where the impact occurred.

When replacing your poly tank, there are several factors to consider. First, pay attention to the density rating. Poly tanks come in three density ratings: 1.0, 1.5 and 1.9.  A 1.0 density tank is rated equal to the pressure exerted by water whereas a 1.9 density tank is would be rated to withstand 1.9 times the pressure exerted by water. A 1.5 or 1.9 rated density tank should be used when the tank will be utilized for transport. Another consideration is use of the tank.  If the tank will be used for transport, the tank should be baffled appropriately.

Full podcast available here:

March 18, 2009 at 7:00 am

Sulfur Recommendations for Wheat in Ohio

In the March 3, 2009 issue of the OSU CORN Newsletter, Keith Diedrick discusses sulfur applications on winter wheat.

Sulfur deficiencies are most likely to occur in soils that are coarse textured (sandy) with very low organic matter. In replicated research done in Ohio over the years (as well in our neighboring states), wheat grain quality and yield improvements are rarely and inconsistently realized when sulfur (as ammonium sulfate or gypsum) was supplemented in the system. Most yield improvements in wheat seem to be due to using the varieties adapted to your fields, planting date, and nitrogen rates. In most Ohio soils, sulfur is in sufficient levels to avoid limitation of yield. Unless you have coarse-textured, very low OM soils where it is economically beneficial, we do not recommend applying sulfur fertilizers to soft red winter wheat in Ohio.  Full CORN Newsletter story available here:

In 2004 a local research project was conducted at Farm Focus to examine the addition of sulfur topdress in wheat.  This study is set up with two different nitrogen topdress rates with and without sulfur for a total of four treatments. The treatments are 60 lb./A nitrogen, 60 lb./A nitrogen with 20 lb./A sulfur, 90 lb./A nitrogen, and 90 lb./A nitrogen with 20 lb./A sulfur. The nitrogen only treatments were applied using 28% UAN liquid fertilizer. The treatments with sulfur had THIO-SUL (26% sulfur solution, 2.87 lb. sulfur/gal.) added at a rate of 7 gallons per acre, and the amounts of 28% UAN liquid fertilizer were adjusted to compensate for the nitrogen available in THIO-SUL. Based on the yield differences from this trial, it would appear the sulfur did improve nitrogen efficiency at the lower rate of application, but had no effect on the higher rate of nitrogen application. If nitrogen was not a limiting factor for yield at the higher 90 lb./A application rate, then a difference in yield from the addition of sulfur at this higher rate would not be expected.  Full study available here:

Podcast available here:

Edit 04/09/09:  On the subject of adding formaldehyde to wheat topdress, below is a quote from Robert Mullen:

We tried this years ago in North Dakota (no real scientific study), and it still burned the wheat when urea formaldehyde was applied. The key to N application this time of year that really influences the injury seen is air temp and humidity. Higher temps and lower humidity increase burn. Burn this time of year is not really a serious issue and it is unlikely to decrease yield, but it is tough for a producer to look at. The only real concerns with burn are if the flag leaf has emerged.

March 11, 2009 at 7:00 am

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