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Agronomy Notebook



Causes and cures of ear droppage in corn

There are several reasons for ears falling off of corn plants. Ear droppage may be caused by both genetic and environmental factors. Corn breeders try to discard the experimental hybrids with a tendency to drop ears and select hybrids with good ear retention.

• I had observed a lot of European corn borer damage in conventional corn fields this year in July. Larvae of second brood of borer can tunnel into the shank and weaken the attachment of ears to the shank.

• During crop scouting recently, I noticed several dropped ears in a corn field. Investigation revealed that corn borers were one of the causes of ear droppage in conventional hybrids.

• Check the shank attachment of each hybrid. Select those with strong attachment with good ear retention characteristics.

• Select hybrids with tolerance to Diplodia ear rot, the whitish fungus that usually starts at the base of ears, causes ear rot and can result in ear droppage as well.

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Factors affecting corn dry down in the field

Growers like to have hybrids with high yield potential, excellent disease tolerance, great standability, faster dry down and lower grain moisture at harvest. Well there seem to be a contradiction here. Hybrids that live longer are not going to die earlier and dry fast. Management decisions such as planting date, plant population, amount of nitrogen used, and use of foliar fungicides all affect the rate of dry down and grain moisture at harvest.

• Corn breeders have to constantly compromise to find hybrids with the right combinations that will produce the highest income for the growers. What are the agronomic and genetic characteristics of corn hybrids that affect rate of dry down?

• Hybrid relative maturity, thickness of pericarp or skin of the kernel, ear angle after maturity can all affect dry down rate. Hybrids with thinner cobs tend to lose moisture faster.

• As corn matures, moisture is lost through cob and ear shank, exposed ear tips and husks.

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How to prevent N leaching

Even though it appears that we are headed for a record corn crop, some farmers have noticed signs of nitrogen deficiency showing up in their crops. According to some of the Seed Consultant professionals, these growers applied the nitrogen fertilizers by splitting application and side-dressed as late as possible. However, the drenching rains that followed a week after caused nitrogen to leach down and, later in the season, fields showed up with N-deficiency symptoms. It is too late for this year’s crop but what can you do for the growing crop to compensate for N loss due to too much water and what may be done to reduce nitrogen leaching for future?

Consider the following approaches to nitrogen management:

• If it happens again, to rescue a growing crop in the field, you might consider reapplying up to half your N fertilizer if it rained three to six inches over a day or two, or if you have field ponding lasting three days or more.

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Maximizing soybean yield potential

The payoff of a year’s worth of planning, planting and preparation is finally getting started with soybean harvest this fall.

The soybean yield at harvest is affected by several factors starting before planting occurs. Although most are focused on late season rainfall and preparing for the upcoming harvest, it is always important to review current management practices and ways to improve for next year’s crop.

The highest yielding soybean fields start by selecting the best varieties for your geographic area, soil types and planting conditions. There are numerous varieties to choose from and multiple sources of information, but first it is important to understand your fields and the traits that are needed to maximize yields. Do you have soybean cyst nematode or other diseases? Look for varieties that are consistently in the upper yield tier in multiple tests like the state trials. Understand that statistics may show that the performance of many varieties can’t be separated in the results due to variation at the testing sites.

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How does flooding affect corn?

We have seen a lot of corn fields that were flooded in the low-lying areas. How does flooding affects corn plants and what can we do about it?

• Like people, if plants can’t breathe, they can’t survive for long. Flooding interrupts the breathing and photosynthetic processes of plants. Obviously, plants which are completely covered by water are at higher risk than those which are partially submerged.

• Oxygen in the soil also gets depleted within 48 hours of flooding and the plant growth functions like nutrient absorption are affected.

• Duration of ponding or flooding is critical. Cooler temperatures after flooding will help the survival of the young plants. Warmer temperatures above 75 to 80 degrees F following flooding can kill plants.

• Plants older than V6 stage survive better because the growing point is above ground after this stage. If the growing point is still below ground, it may start to rot.

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Palmer amaranth management tips

During winter meetings we have been emphasizing the importance of controlling Palmer Amaranth, one of the most dangerous weeds for Ohio agriculture. It is one of the fastest spreading weeds that is trying to get a foothold in the Corn Belt. It can spread like wild fire unless stopped in its tracks. Check out the facts below:

• Palmer Amaranth is an annual broad leaf and is related to other Amaranth species like Pigweed, Waterhemp, and Redroot.

• It grows faster than other pigweed species and can grow 2-3 inches per day. Some studies have reported it can reduce corn and soybean yields by 70-80%, if not controlled.

• Palmer Amaranth has already caused a lot of problems in the South and recent reports from Kentucky indicate it is marching north and east, spreading into Illinois, Indiana, Michigan and Ohio.

• Each Palmer Amaranth plant can produce up to one million seeds.

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Problem soybean fields can recover

Corn got off to a rocky but reasonable start this year but soybeans went in at a rougher point as we progressed through the planting season. I am reminded of Purdue University’s Bob Nielsen and his corn article of a couple of years ago about the ugly duckling — ugly corn can turn into a lovely crop. This applies even more so to soybeans. Time after time I talk growers out of replanting a thin soybean field, to be told later how great the crop looks.

While we prefer and generally can expect greater yield with uniform, on time planting of soybeans, they have a fantastic ability to compensate for skips, for variability in emergence and for a generally poor start to the season.

From research we have done on soybean production practices, we know of the soybean plant’s ability to compensate for late planting, for wider rows and low seeding rates.

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Advice on post-planting nutrient application

This year’s longer than usual planting season, and less than favorable weather throughout much of May, has led to a stressful time for many fields of corn across the region.

“Give your crop the opportunity to have its top potential,” said  Lonny Smith, Agro-Culture Liquid Fertilizers Senior Marketing Manager.

He said this time of year is crucial for growers and that producers shouldn’t be overly concerned if they did not get to address all of their nutrient needs during planting.

“One of the things we as a company are encouraging growers to do is to not worry about getting all their nutrients on at planting time,” he said. “There have been a number of people across the country and in Ohio as well that ordered, or pre-ordered, fertilizer products they were going to use at planting time and then have found from their co-ops or suppliers that, because of transportation issues, they weren’t able to get the materials they wanted. 

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Assessing early season soybean injury

Spring 2014 has been quite challenging with wet soil and cold temperatures.  We’ve received several calls and e-mails regarding soybean seedling damage (from those who have actually been able to plant).  It appears that some soybean fields were hit with a “trifecta” of stress issues. What should we be looking for in terms of frost, PPO herbicide injury, and disease?

Frost 

Frost can occur at air temperatures between 32 to 36 degrees F while a freeze requires temperatures less than 32 degrees. From the weather records I have looked over, air temperature dropped as low as 34 degrees F in northern Ohio on May 16.  Soybean plants should be assessed for frost damage at least five days after suspected injury to inspect for regrowth.  If damage occurs above the cotyledons, the plant will likely recover.  If damage occurs below the cotyledons, the plant will not recover.  Look for a discolored hypocotyl (the “crook” of the soybean that first emerges from the ground) which indicates that damage occurred below the cotyledons. 

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Why do my soybeans look like they are dying?

This week we have had numerous reports throughout Ohio, Indiana, Illinois and Kentucky regarding soybeans that are not looking as healthy as we like. The majority of soybeans have the outside of the cotyledons that look brown as well as the hypocotyl, especially when in the neck stage.This appears to be happening to all varieties from all companies, so it is not product specific.So what is going on?From what  I can tell there are two things happening.First, the vast majority of fields with this issue have been sprayed with a PPO inhibitor containing the active ingredient flumioxazin.These herbicides would include Valor®, Valor® XLT, Envive®,Enlight®, and Gangster®.
The herbicide label of Valor® actually states,“Crop injury may occur from applications made to poorly drained soils under cool, wet conditions.Risk of crop injury can be minimized by not using on poorly drained soils, planting at least 1.5 inches deep and completely covering seeds with soil prior to preemergence applications.” Several areas impacted received over 3” of rain which would constitute “poorly drained”in my opinion.
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What causes purple corn?

Cool and wet weather at early stages of corn development, as we are experiencing this year, are ideal for the appearance of purple plants. What causes the plants to become purple? Some of the reasons are given below:

• Purple leaves are caused by a pigment called anthocyanin. When sugars produced by the chlorophyll cannot be deposited in the growing stalks, leaves, and roots, they are converted to anthocyanin pigment which is red to purple in color.

• Acidic soils with pH lower than 5.5 may also cause seedling purpling.

• Wet soils can also inhibit the nutrient uptake and cause purple leaves.

• Purpling generally occurs between V2 to V5 stages of growth. By V8, purple leaf syndrome disappears and color becomes normal healthy green again.

• Any plant stresses which reduce uptake of phosphorus may result in purple leaves and stalks. Root restrictions may also cause phosphate deficiency symptoms.

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Early season corn growth and development

A corn plant requires the accumulation of Growing Degree Units (GDUs) to reach maturity. This is regardless of the number of calendar days it takes to accumulate them. A 105-day hybrid requires about 2600 GDU’s to reach Black Layer and a 114-day hybrid requires about 2800. You can use this information to your advantage because we know about how many GDU’s need to accumulate for each growth stage. In other words, if you know the planting date, we can predict when the hybrid will pollinate. This can help growers make timely applications of herbicides and fungicides. Also, it can predict when optimum timing is for foliar fertilizer applications.

 

Calculating GDUs

To calculate GDUs, record the minimum and maximum temperatures for the day. Add them together and divide by two. Next subtract the base threshold of 50 degrees F. Because optimum corn growth takes place between 50 degrees and 86 degrees F, the lowest temperature that can be used in the formula is 50 degrees F, and the highest temperature is 86 degrees F.

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Planting corn after a failed wheat crop

fairfield-county-wheat

Late fall planting, harsh winter conditions and/or excessive rainfall can all lead to an undesirable wheat stand in the spring. Often growers would like to turn those failed wheat acres into a corn field and questions arise as to how to best ensure a successful transition.

The transition starts with killing the existing wheat stand to avoid the competition of early season weeds. Then nutrient management and the intricacies associated with the existing nutrients and future nutrient recommendations need to be addressed. Growers then need to identify tools and keys to ensure a successful stand establishment is obtained. In addition, insect pressure is greater in volunteer wheat stands and need to be controlled to ensure a prosperous corn crop.

The first step is to kill the remaining wheat crop prior to planting the corn. Corn is very sensitive to early season competition and killing the growing wheat will eliminate that competition.

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Tips for high yielding soybeans

Rotate: The highest soybean yields often are in fields that have been continuous corn, have high yield potential soils and often have plenty of manure.

Proper fertility levels: Soil test: pH 6.5-7, 30-60+ pounds per acre Phosphorous, 200 to 300 pounds per acre K depending on soil type. Adequate drainage is a very important consideration also.

Variety Selection: Varieties that are proven to have above average yield potential while considering defensive characteristics such as Sudden Death Syndrome, Phytophthora Root Rot, Brown Stem Rot, White Mold, Frog Eye Leaf Spot.

Use treated seed. Acceleron seed treatment gives you protection against early season diseases. Upgrade to Acceleron with Poncho/Votivo for protection against bean leaf beetle, nematodes and other spring pests such as seed corn maggot, which is more likely in high amounts of decaying matter, even if tilled. Bean leaf beetle are most likely if you have the first planted beans in the area.

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Starter fertilizer in corn production

Starter fertilizer in corn production has traditionally been recommended for fields with cool soil temperatures, including exceptionally early planted or no-till fields, or those with high residue cover. In cool soil conditions, starter fertilizer placed near the developing seed provides easily accessible nutrients until soil conditions improve and an adequate root system is established. Starter fertilizer has also been recommended for fields with low phosphorus levels, and research studies have proven the value of this practice. However, some growers seeking to exploit grain price opportunities are evaluating whether starter fertilizer can play a more prominent role in increasing corn yields.

Starter fertilizer is defined as small amounts of plant nutrients — nitrogen (N), phosphorus (P) and potassium (K) — placed in close proximity to the seed, usually at planting.  Placement can be directly below, to the side, or to the side and below the seed. Growers sometimes consider broadcast or liquid fertilizer application to the soil surface as “starter”; however, these should not be included because nutrient placement is positionally unavailable to early seedling growth.

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What’s the right seeding rate for soybeans?

I am in Ukraine on a training mission to assist growers here in growing better corn and soybeans. One question that keeps coming up is, “What is the right seeding rate for soybeans?” Some of them have told me that it’s 1 million seeds per hectare. I think in terms of 1 million for wheat, but a hectare is 2.47 acres, so 1 million is 405,000 seeds per acre — still too high. Take into account that they use brown bag seed, so add maybe 20% due to reduced quality seed — still too high. And oh, by the way, this brown bag seed seems to tolerate very high levels of “gleefosat” herbicide applied over the top.

I give them the same answer I do when the question comes up in Ohio — we need about 100,000 plants per acre at harvest to achieve full yield. You just calculate backwards to determine your losses to germination percent, emergence, disease, insects, crusting, excessive moisture, etc.

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Boost corn yields

We will be discussing the proven methods you can use to boost corn yields this year. I am sure you are already using most of these ideas. I challenge you to pick at least one idea that fits your farming practices and try to improve it.

• Use minimum or no-till — especially on erodible land. It helps in conserving moisture loss reduces soil erosion and minimizes compaction.

• Set a realistic yield goal — It should be based on your soil type, organic matter and historical data. Goals based on 2012 or 2013 alone will be unrealistic. So you may want to use last five-year average as a guide.

• Study yield maps — Analyze your yield data field by field with your Seed Consultant and try to Match hybrids with soil types.

• Do soil tissue tests — These tests should be conducted at the right time and the advice of the consultant followed.

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Sub-surface soil compaction

Compaction that occurs below the soil surface is even more important than surface crusting. It is hard to diagnose and can cause serious yield losses if not corrected. Soil compaction can occur throughout the growing season and can cause poor crop growth.

• If the soils are wet, tillage implements can cause soil compaction just below the depth of the operation.

• Large farm equipment like tractors, manure spreaders, trucks, planters and combines can cause compaction within the root- zone, especially, when the soils are wet.

• If tillage operations are always performed at the same depth, a hardpan can develop just below the depth of tillage operation. Weight of the tillage machines can cause compression of the soil particles causing compaction.

• Wet soils, especially those with higher clay content are more likely to develop a hardpan. The depth of the compacted layer can be determined by slowly digging and moving the soil with a shovel and exposing the top of the compacted layer.

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Soil compaction and soil health

What are the causes of soil compaction?

Soil compaction is one of the most important factors that can affect soil health and reduce crop yields. In the early 1980s, Purdue University soil scientist Gary Steinhardt and Ohio State University Ag Engineer Randall Reeder were making farmers aware of the compaction problem and its effect on yield reduction. Compaction may be caused in many ways. We need to diagnose the reasons for compaction before corrective measures can be taken. Surface compaction can occur from the impact of rain drops or in the form of crusting due to excessive rains and ponding. It may also be caused by the impact of irrigation water.

• If the soil is left bare and is exposed to hard rains or irrigation water, the impact of water breaks down the larger soil aggregates and the granular structure of the soil on the surface are degraded, causing compaction.

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Managing crop residue

Corn growers know the satisfaction of seeing newly emerged, uniform rows of green corn plants set against the backdrop of dark, rich soils. By contrast, it can be painful to see an uneven stand from the truck window when driving past a field.

The cause of an uneven stand could be excess crop residue in the planter row.

“Corn residue will delay and outright interrupt plant establishment, and suppress the resulting plant population,” said Andy Heggenstaller, DuPont Pioneer agronomy research manager. “Corn residue is always a management issue, and high-yield production systems increase residue levels.”

Stand establishment is more of a challenge for corn than it is for soybeans, because corn is typically planted earlier, into cooler and wetter soils. Also, soybeans can accommodate reduced emergence by adding additional pods to make up for yield that could be lost from lower plant populations. That’s why hitting optimum corn plant population levels is so important.

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