Symptoms of potassium deficiency are surfacing in Northeast Iowa corn fields. These symptoms are most likely the result of dry top soil during late May and early June. Any soil factor that limits root growth and water uptake can limit K uptake. For more information, tune into Nick Benson’s most recent YouTube video:

http://youtu.be/F7iVHw8BMo4

Guest blog by Kurt Metzger,
West Area Seed Solutions Specialist, MaxYield Cooperative

Unusually dry weather this fall has corn growers asking questions about whether or not they should wait to apply Anhydrous Ammonia (NH3).

Applying NH3 in dry soils is actually the best situation if a producer can get it to seal. The NH3 bar must be deep enough to get adequate soil separation between the point of ammonia injection and the depth where corn seed will be planted next spring, as stated by John Sawyer, Department of Agronomy, in his recent Integrated Crop Management News article entitled, “Anhydrous Ammonia Application and Dry Soils.”

At MaxYield Cooperative, we began applying NH3 nearly two weeks ago.  It was exceptionally dry then, so we made sure the NH3 bar was in the ground 6 to 7” (4-6” is typical).  We’re recommending that producers apply nitrogen deeper to help prevent damaging seed next spring.  This same point is made in Sawyer’s newsletter article.  He writes, “Shallower injection, greater movement upward from the injection point, wider knife spacing, or higher rates can lead to ammonia being in the seeding area at rates high enough to cause damage” next spring.

Fortunately, the newer NH3 bars have much better disk closers and will be more aggressive to move the soil in order to seal the in the soil.

Another point is with the dryer soils, the zone that the ammonia in the soil becomes a larger radius to attach to the clay.  This means it takes more moisture next spring in order for leaching to occur.  Remember the nitrogen moves with the soil water profile and only will move with the excess moisture.  Use of N-Serve is still very much recommended.

With that said, however, overnight rainfall will help mellow the soil and provide for better sealing upon NH3 application.  Soils are so dry that it will take many more inches of rain before it’s too much moisture is a concern.  The best analogy is that our glass is only ¼ full now, so we have a lot of room before rain fills our glass and runs it over next spring.

Spring planting is just around the corner, and with it comes the age old question, “What is the right rate of Nitrogen for my field?”

A recent research paper published by Purdue University sums up Nitrogen (N) management succinctly: Nitrogen fertilizer costs remain volatile but continue to be one of the most expensive variable costs for corn. Applying “more than enough N” is no longer cheap “insurance” as it once was many years ago. Applying “more than enough N” is also not environmentally friendly.

High fertilizer costs and environmental impacts should encourage growers to critically evaluate their N fertility program, including application rate, fertilizer material, and timing.Here are a few tips for you to consider the right Nitrogen rate for your field this spring:

• Customize applications. Tailor Nitrogen applications to each individual field. Because farmers are constantly striving to achieve higher yields, it’s not effective to try and use a general “one size fits all” recommendation.  That’s why it’s so important to first determine your needs with a soil test.
• Soil test. Conduct a soil test to obtain a guideline of soil nutrients and needs. Purdue’s research paper stated some soils provide as little as 25% of the crop N requirement, the remainder coming from fertilizer N, while other soils provide in excess of 50% of the crop N demand, with a lesser amount needed from applied N. Thus, it’s vitally important to first determine soil needs before application. Through Latham’s Seed2Soil®program, we work with customers to conduct an Amino Sugar Nitrogen Test to help determine where Nitrogen rates need to be increased, maintained, or decreased.
• Recognize timing differences. Certain hybrids respond better to Nitrogen at different times of the growing season. For instance, some hybrids will require an extra shot of Nitrogen when they begin the grain fill period directly after pollination. Work with your seed representative to determine the best timing for the products in your field.
• Better for your pocketbook and the environment. The goal with Nitrogen management should be to place the right amount on the right acres at the right time. Latham’s Seed2Soil program helped reduce Nitrogen needs by 20-25 pounds, according to four years of research and in-field studies. Learn more about Latham’s Seed2Soil program.

Do you have any questions regarding Nitrogen management for your field?

Applying nitrogen to corn at recommended rates is critical to maximize economic returns, minimize environmental losses and conserve energy, says John Sawyer, ISU Extension soil fertility specialist and agronomy professor.

In an effort to increase awareness of farm energy conservation practices, Iowa State University Extension has released a publication titled, Energy Conservation in Corn Nitrogen Fertilization. This publication shows the energy consumed during the production of nitrogen versus phosphorus and potassium fertilizers. It also provides resources to determine recommended nitrogen application rates for corn, such as the online Corn Nitrogen Rate Calculator from ISU’s Department of Agronomy.

More information, including a link to this Extension publication, is available today from Wallaces Farmer online.  To view the entire article, click here.

Oftentimes questions surrounding emergency or catch-up fertilization for soybeans arise in June, as highlighted in a recent e-newsletter from the Iowa Soybean Association. We’ve seen a lot of conversations on Farmers for the Future and New Ag Talk surrounding this question, as well. Most producers don’t have to worry about this since adequate amounts of phosphorous (P) and potassium (K) are usually applied before planting. In a year like this, however, excessively wet conditions alter the crop nutrient uptake and affect fertilization.

Is applying dry, granulated fertilizer a viable post-emergence option?

The short answer is “probably not” for two main reasons:  First, both P and K (but especially P) are needed at early growth stages to enhance plant cell multiplication when the number of nodes, leaves, and potential seed numbers are largely determined. Second, the application of fertilizer to the soil surface or banded/injected between the rows will be of low efficiency, mainly due to the common low, or infrequent summer rainfall (which hasn’t been the case for many areas this season). There is one situation in which an in-season application of granulated P and K fertilizer might be considered, and that’s when soil tests are very low, and for certain the producer will have to apply a high fertilizer rate for the following year’s corn crop to assure adequate P and K levels.

What about foliar fertilization?

Some producers ask if foliar fertilization could help improve soybean growth and grain yield. While it’s a possibility, the chances are low for fields that have been well fertilized or where growth is limited by factors other than nutrient supply.

Thus, the article concluded in-season fertilizer application for soybean will seldom prove cost-effective in Iowa production systems. The exception might be when soil samples confirm that the soil tests very low or low and there was insufficient pre-plant fertilization. A large application of granulated fertilizer to soil during the very early growth stages may result in some yield increase and will begin to build up soil test levels that will have to be increased for the next crop anyway, but the economic benefit for this year’s soybean is very doubtful. The probability of an economic response to foliar fertilization is small, but this practice may be justified when nutrient deficiency symptoms are obvious, with confirmed deficient-testing soil, or when soil or climactic factors (other than drought) limit nutrient uptake in early summer.

Source: Iowa Soybean Association, Gold Standard

An article on the Wallaces Farmer website today stated some farmers and crop scouts are reporting signs of potassium deficiency on plants in cornfields. They also reported some fields showing symptoms of anthracnose leaf blight.

Brian Lang, Iowa State University Extension field agronomist provided the following information.

As corn begins to move to its rapid growth phase (beyond V6 stage), you may see potassium, or K, deficiency symptoms show up on corn in localized areas of the field (see right hand image). Areas showing potassium deficiency are usually associated with two situations:

1) Soil K levels are low and initial seedling roots and/or

2) The mesocotyl had premature rotting and contributed little to the rooting area for absorption and movement of K to the topgrowth.

As the permanent root system advances in development, the symptoms of K deficiency will often subside, but not always. The following link provides a series of photos that walk you through a description of anthracnose and K deficiency symptoms as well as corresponding rooting problems found in some fields with these issues.

www.extension.iastate.edu/NR/rdonlyres/229080A5-0FEE-44E7-86C0-C63F2E81654A/127137/AnthracnoseKDeficiency.pdf

Anthracnose leaf blight is a disease of corn that’s fairly normal

Most cornfields will exhibit some scattered anthracnose lesions on lower leaves (see image below). Corn routinely grows through this stage, however, some fields may exhibit necrosis of entire leaf margins on the lower two to three leaves. One way to distinguish this symptom from K deficiency or leaf burn injury from postemergence herbicides is to look for the acervuli on the lesions. These are small black spiny structures that are visible with a hand lens on the dark-bordered lesions on the corn leaves.

If the field becomes a significant problem, the following management options are considered for the field’s immediate future:

• Crop rotation to a nonhost crop like soybeans, alfalfa, etc.
• Select a more resistant corn hybrid next year.
• Utilize tillage to bury crop residue which can harbor the fungus over winter.

Click here to read the full article.

Photos courtesy of Iowa State University