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Agronomy Notebook



Watch for Palmer amaranth

Now is the time of year when scouting for Palmer amaranth is critical. This weed’s emergence begins in May and will last through the fall. Because of its prolific growth habit and resistance to multiple herbicide modes of action, it is critical to identify and control Palmer amaranth shortly after it emerges.

It is important for growers to have the ability to identify Palmer amaranth so that it is not confused with other pigweed species. Universities have published some excellent resources for ID and control of Palmer, including this Purdue Fact Sheet and this Herbicide-Resistance Management publication. Staying on top of this aggressive weed is critical to managing it and keeping it from competing with crops.

 

Tips for controlling Palmer amaranth

‪1. Scout for and identify problem weeds early. Palmer Amaranth is a pigweed species and can easily be confused with other pigweeds, such as redroot pigweed, during early growth stages.

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Corn plants appreciate a stress-free summer

Over the next several weeks the upper canopy in Ohio corn fields will look much different, as tassels begin to emerge and extend beyond the top leaves of the plant. This visual change signifies that the corn crop will soon be shifting from vegetative into reproductive growth. The first reproductive growth stage (R1) begins when silks extends outside of the husk leaves and typically occurs two to three days after tassel emergence.

The two basic processes that occur during corn reproduction are pollination (transfer of pollen grains from the tassel to the silks) and fertilization (joining of the pollen grain and ovary to create an embryo). Though these processes seem very simple, there is a lot riding on their success. Approximately 85% of the variability in grain yield is related to the number of kernels produced per acre while the remaining 15% of the variability in grain yield is related to the weight of these kernels.

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Watching for fertilizer burn

Some plants don’t have much of a root system while others show a beautiful root system with no shoot.  What is going on? In each case I have looked at this year, each farmer was using more than 30 pounds of total nitrogen (N) (28% plus 10-34-0) and/or sulfur in a 2×2 system. These reduced stands appear to be caused by fertilizer injury burn.
Urea ammonium nitrate (28% UAN) is made up of 50% urea, 25% ammonium, and 25% nitrate. When urea volatilizes, it turns into ammonia (the same type of ammonia in anhydrous ammonia) and is lost to the air. That’s why we need to work in urea (or stabilize it) within a few days after application if we are using it as a N source. As a starter, stabilizing N is not recommended and is not normally a problem.
So what made urea volatilize faster this year?
  1. Volatility of urea is microbial driven, so warmer temperatures make this reaction occur more quickly.
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With planting finished, it’s time to take a walk

Finally corn and soybean fields are planted and are up and growing. Now growers need to walk their fields often or hire a professional to identify crop issues that can impact yields.

What happens in the next 80 to 90 days will have a major effect on maximizing yield potential. A good tool for scouting plan is the Corn and Soybean pocket Field Guide from Purdue or Ohio State University. Here are some potential problems to monitor.

There are corn fields where seedling blights — especially Pythium  — had an effect on the stand, especially in early planted fields. With the wet and cold conditions of early May, soil borne insects including wireworms and seed corn maggots attacked the seed and also hurt the stand. For some fields where 30,000 to 34,000 kernels were dropped, because of seedling blights and insect issues, stands were reduced down to 24,000 to 28,000 plants.

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Documenting the relationship between corn emergence and yield

One very important aspect of corn plant development and yield is emergence. While evenly spaced “picket fence” stands are often discussed, agronomists and university experts stress the more important aspect of emergence-uniform emergence. According to Paul Jasa, University of Nebraska Extension ag engineer, “When a plant develops ahead of its neighbor, it hurts yield dramatically. It’s going to vary somewhat from year to year, but a plant lagging behind those around it becomes a weed.”

In order to achieve high yields, uniform emergence is essential.

As part of Seed Consultants testing in 2016, our agronomic team has planted a test plot in Fayette County that will be observed twice daily (morning and evening) during the emergence process. This study will observe 1/1000 acre sections of rows for 5 different hybrids. Approximately every 12 hours an agronomist will walk through the plot and place garden stakes next to plants as they emerge (as pictured above).

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Deal or no deal: Finding the right nitrogen rate

One of the largest investments in a corn crop is the nitrogen (N) application, and many farmers will be sidedressing their corn soon. Especially with this year’s profit outlook, it is important to carefully consider how much N to apply. Deciding on the correct N rate can be a lot like playing the game “Deal or no deal.”

“Deal or no deal” was a TV game show that aired a few years ago. The game consisted of a series of 26 cases, each containing a different amount of money ranging from $0.01 to $1,000,000. A contestant would select a case at random, and then play the game to reveal how much money was in their case, or try to sell their case for more than it was worth.

Each corn field will require a certain amount of N to reach its maximum yield potential. However, that ideal rate is a lot like the dollar value in the contestant’s case — it isn’t known until the end of the game (harvest).

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Purple corn concerns?

For many areas of the eastern Corn Belt, a great deal of corn has been planted over the past few weeks. Some corn has emerged and is in the early stages of growth. One phenomenon that commonly occurs at the early stages of the growing season is the appearance of purple corn plants. Corn plants can turn purple for several reasons related to environmental factors such as:

• Sunny days and cool nights (temps in the 40s to 50s F)

• Soil pH lower than 5.5

• Cool temperatures

• Wet soil

• Stresses that hinder the uptake of phosphorus

• Herbicide injury

• Soil compaction

Because many fields have saturated soils and the forecast includes a week of cooler weather, producers may see some purple plants in their fields. Purpling in corn due to cooler weather most often occurs when plants are in the V2 to V5 growth stages. Because of diverse genetics, hybrids react differently to early stress and some will exhibit purpling while others will not.

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Uniformity continues with seed germination

The first step in corn stand uniformity is getting the corn planter maintained and adjusted to plant the corn crop as uniformly as possible. The next step in the uniformity equation is achieving uniform emergence.

Germination is simply the process that allows a seed to sprout or begin to grow. Although the definition is simple, the actual process is quite complex. The germination of a corn seed requires soil moisture to “reawaken” the seed and adequate temperatures to speed along the enzymes and chemical reactions that allow the cells in the corn plant to grow and reproduce.

Corn growers know the importance of germination but often don’t believe they have much of a roll in that process. Growers tend to be disconnected from the germination process because they cannot control the rainfall, sunshine and/or temperatures. But, in all accounts where and how a grower places the corn seed greatly dictates the ultimate success and/or failure of germination.

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Identifying wheat growth stages: Feekes Stage 6

For determining the right timing of winter wheat management decisions, identifying the growth stage of wheat plants is critical. For example, knowing how to identify wheat Feekes Stage 6 is important because this is the cutoff timing for certain herbicides ( i.e. 2,4-D and dicamba) and also the point at which rapid development with increased need for nitrogen occurs. Feekes Stage 6 is also the timing when extreme cold temperatures can cause significant damage to wheat plants. Agronomists and wheat experts recommended that spring applications of N are made prior to Feekes Stage 6 (also known as jointing) when the wheat plant begins a period of rapid growth and will utilize more nitrogen. Wheat is currently at or past Feekes 6 in many areas.

How do you identify wheat plants at Feekes Stage 6? The easiest way to tell is to dig up a wheat plant and examine the main stem.

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Is starter fertilizer a practice to cut in 2016?

Growers use multiple fertilizer practices and application timings to address the fertility requirements for successful corn production. As the “bearish” agricultural economy continues, resulting in low commodity grain prices, many producers are looking for ways to streamline their crop production budgets, and often pose the question, “Should I remove my corn starter fertilizer program in 2016?”

Starter fertilizer is typically defined as placing a small volume of fertilizer, either in close proximity (i.e. two-by-two, which is two inches adjacent and two inches below the seed furrow) or inside the seed furrow while in direct contact with the seed (i.e. pop-up fertilizer). Two-by-two placement allows the newly emerging seminal roots to encounter the fertilizer shortly after emergence. “In-furrow” fertilizer may result in earlier nutrient utilization by the plant when compared to a traditional two-by-two adjacent nutrient placement and involves less application hardware, less overall cost and lower amounts of fertilizer. So in regards to a nitrogen, phosphorus and potassium starter program, does this option benefit your bottom line?

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Corn germination and emergence processes

As growers across the Eastern Corn Belt get ready to plant corn, it is important to review and understand what goes into corn the germination and emergence process. Uniform corn emergence is one of the most important aspects of stand establishment and producing high yielding corn. Understanding germination, emergence, and how environmental factors influence these processes is the first step toward ensure uniform emergence.

Germination

Germination begins in a corn seed when it has imbibed 30% of its weight in water. While corn can germinate when soil temperatures are 50 degrees F or higher, research has determined that the optimal temperature is 86 degrees F. Visual signs that corn germination is taking place are the appearance of the radicle root, coleoptile, and seminal roots. When temperatures are cooler, the germination process is slower and seedlings are more susceptible to disease, insects, and other damaging factors.

Emergence

Uniform emergence is one of the most important yield-influencing factors that growers should work to achieve.

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Reminder about winter wheat management for spring of 2016

Wheat Feekes

With recent warm weather, winter wheat has broken dormancy and begun to green up. With wheat plants no longer dormant, scouting and management of wheat fields is critical to producing high yields. As discussed earlier in the year, now is the time to plan for N applications where field conditions allow. Below is an excerpt from and a previous newsletter with recommendations for nitrogen application and rates:

Spring applications of N should be made after the plants break dormancy. Although in some situations field conditions may be favorable, nitrogen applied in the late winter before plants have broken dormancy is more likely to be lost before plants can utilize it. Spring N applications should not be made before wheat has broken dormancy and begins to green up. The University of Kentucky publication “A Comprehensive Guide to Wheat Management in Kentucky” recommends: “When making a single N fertilizer application the best time is when the crop growth stage is Feekes 4-5, (Zadoks 30, usually mid-March) just before the first joint appears on the main stem and when wheat starts growing rapidly.” The UK publication goes on to say that “The rate of N fertilizer for a single application should be between 60 and 90 lb N/acre for fields with a yield potential less than 70 bu/acre and 90 to 100 lb N/acre for fields with greater yield potential.”

Wheat plants begin a period of rapid growth and stem elongation once they reach Feekes Stage 6 (first node visible).

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Things to watch with corn emergence

Two aspects of stand establishment often discussed by agronomists are emergence and seed spacing. “Picket fence” spacing in corn helps plants grow efficiently and minimizes competition between them. Uniform spacing is an important part of stand establishment. More importantly, however, is uniform emergence. Plants that are just 1 leaf collar behind (due to uneven emergence) significantly reduce yield. According to Paul Jasa, University of Nebraska Extension ag engineer, “When a plant develops ahead of its neighbor, it hurts yield dramatically. It’s going to vary somewhat from year to year, but a plant lagging behind those around it becomes a weed.” To achieve uniform emergence, consistent planting depth is critical.

Field conditions, gauge wheel settings, unit down pressure, and planter speed all affect seeding depth. Set planter depth and check it regularly. A planter may have enough weight to apply the proper down force when full, but what about when it’s almost empty?

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Corn planting date considerations

For much of the Eastern Corn Belt it is widely understood that the optimal planting period is between April 20 and May 10. Research has proven that corn loses yield potential daily when planted after the beginning of May. For the Central Corn Belt, the declines in yield potential due to planting delays vary from about 0.3% per day early in May to about 1% per day by the end of May, according to Bob Nielsen from Purdue University. Knowing that this is true, it can be frustrating during a wet spring or when field work is delayed for one reason or another. Planting is a critical component of a successful crop as it sets the stage for the entire growing season. However, it is important to keep in mind that early planting is just one of many factors that contribute to high yield potential. Planting early favors high yields, but it does not guarantee them and growers should not focus entirely on the calendar.

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How do wheat tillers contribute to yield?

In the coming months as the weather warms up, winter wheat will break dormancy and will begin to green up. After a period of about two weeks following green up producers should evaluate their stand in order to make management decisions for their wheat crop. Part of this evaluation includes counting tillers to determine if there is an adequate stand for achieving high yields. According an article in a 2014 C.O.R.N. Newsletter written by Laura Lindsey, Ed Lentz, Pierce Paul, “Yield potential is reduced if tiller numbers fall below 25 per square foot after green up.”

So, what is a tiller? And how should they be counted? Tillers are additional stems that develop off of the main shoot of the plant. Primary tillers form in the axils of the first four or more true leaves of the main stem. Secondary tillers may develop from the base of primary tillers if conditions favor tiller development.

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Leaf disease: Management and consideration for 2016

As spring of 2016 approaches, producers across the Eastern Corn Belt will begin to put more thought towards their production plans and management decisions for the upcoming season. One challenge that has affected corn yields in our sales territory over the past few years is foliar disease, especially Northern Corn Leaf Blight. Anyone who attended one of our Winter Agronomy Meetings heard a discussion of what conditions promote diseases (Northern Corn Leaf Blight and Gray Leaf Spot) and possible management options. You might ask, “What are the important management options that will protect yield from leaf diseases?” Below are the answers to that question:

• Select Resistant Hybrids: One very effective way to protect yield potential is to plant varieties that have resistance to leaf disease. Many university publications, including this MSU fact sheet, generally recommend that fungicides are not required for hybrids with strong disease resistance.

• Crop Rotation: It is widely understood that crop rotation is one of the best management practices for mitigating problem diseases.

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Helpful tips for reducing soil erosion

Soil erosion is an annual problem throughout the Eastern Corn Belt. Recent research estimates that farmland across the Corn Belt looses close to four tons of soil per acre each year due to erosion. Additionally, even under the best conditions topsoil buildup is very slow, if it occurs at all. Soil particles can be detached and moved out of a field by both wind and water. Wind can pick up small soil particles, transporting them long distances. Water moving along the ground surface can remove a thin sheet of soil, create small channels, or wash out large gullies.

Soil erosion has a large number of negative effects to both crops and the environment. It is important to use various management practices to protect the soil’s surface and minimize the likelihood of erosion.

 

Factors that contribute to erosion

‪1. Rainfall — soil erosion increases as length or intensity of rainfall increases.

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Palmer amaranth update

During the past few years agronomists and university weed experts have been discussing the potential northern movement of an aggressive weed that can reduce yields and increase costs of weed control. The arrival of Palmer Amaranth, nicknamed “Pigweed on Steroids”, has been confirmed in multiple states across the Eastern Corn Belt. Seed Consultants’ customers and agronomists have already worked together this year to deal with new populations of Palmer that were discovered this spring. Palmer amaranth populations have recently been confirmed in several counties in Indiana, and are present in Michigan, isolated areas of Ohio, and areas of Western Kentucky.

Palmer amaranth is an aggressive plant that thrives in drought, can grow more than two inches a day, is resistant to multiple herbicide modes of action, and produces 100,000 or more seeds per plant. Many populations of this weed are resistant to multiple herbicide modes of action. The key to keeping Palmer Amaranth from establishing itself is implementing management practices to effectively eliminate seed production and hinder its ability to spread.

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Use plot data to make good decisions

As harvest continues across the Eastern Corn Belt, seed companies, universities, and growers will have the chance to compile and analyze data from yield testing. One of the most important decisions a farmer will face all year is deciding what variety to plant and in which field to plant it. To ensure that the best possible decision is made next spring, it is critical to spend some time looking at yield data. While reviewing data is critical, knowing how to determine whether it is accurate and useful is equally important. Below are some tips for using data to make sound planting decisions next spring.

Look for replicated data

Don’t rely on yield results from one strip plot on a farm or from a single plot location. Look for data from randomized tests that are repeated multiple times and across multiple locations. Replications in testing increase the reliability of the data.

For strip plot data, was a “tester” used?

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Tassel ears showing up in fields

While scouting fields this time of year it is common to find a few strange looking ears. Corn is a monecious plant, which means it has separate male (the tassel) and female (the ear) flowers. In some cases, both male and female structures form as a combination in the same plant structure.

“Tassel-ears” often form on the tillers or “suckers” of a corn plant. Corn experts and agronomists believe that tassel ears are the result of some kind of environmental occurrence, however, the exact event that causes their development is unknown. The number of kernels that form on the tassel ear are limited. Without a husk to protect them, these kernels are exposed to environmental conditions and are usually damaged by the time harvest occurs.

According to Bob Nielsen from Purdue University, “The male and female reproductive organs of a corn plant are contained in physically separate unisexual flowers (a flowering habit called “monoecious” for you trivia fans.) The tassel represents the male flower on a corn plant, while the ear shoots represent the female flowers.

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