C.O.R.N. Newsletter 2005-37

Dates Covered: 
November 1, 2005 - November 8, 2005
Editor: 
Curtis E. Young

Nitrogen Prices and Management

Authors: Robert Mullen, Edwin Lentz

Nitrogen (N) prices continue to creep up putting more pressure on agronomists to manage this input more efficiently. Because prices are increasing, you may be considering some alternative methods of application. These may or may not be the best management options.

Fall N prices are traditionally lower than spring prices; hence it is more economical to secure N fertilizer this time of year than next spring. Unfortunately, unless you can work out delivery next spring with your retailer, you will need a facility for storage (obviously). Considering the cost of storage, fall purchase may or may not be the most economical option because we do not know how high N prices will be in the spring (we are speculating that on average prices will rise).

Fall Application of Anhydrous Ammonia
Because fall N prices are typically cheaper than spring prices, fall application of anhydrous ammonia may appear to be a good alternative to spring fertilization. The economic argument may appear to be sound, but if you consider the considerable risk of fall/winter application this method of application is probably not the best option. Depending upon when the anhydrous is applied and soil temperatures after application, nitrification can take place resulting in a mobile form of N susceptible to loss (nitrate). This can also occur if soils warm up quickly in the spring and planting is delayed. On average, the yield levels from fall applied anhydrous are 10% lower than spring applied anhydrous (within a giver year the loss could have been greater (28%) or very little loss at all). There is a greater risk for N loss (and subsequent yield reduction) if fall anhydrous is applied to coarse textured soils.

Starter Applications of N
Not only are you facing higher N costs, you are also seeing higher fuel bills. This makes single pass applications of multiple inputs much more attractive. Application of starter fertilizer is such an operation. The cost of fertilization is low because the equipment is already going through the field. Depending upon your planter and its capabilities, you can either apply dry or liquid material with the seed or beside and below the seed. Do not apply more than 8 to 10 lbs of N with the seed (furrow application or pop-up), salt injury and/or ammonia toxicity can potentially limit germination. Planters with 2 x 2 application attachments (liquid or dry) allow you to apply more N fertilizer, but there is still a limit on the rate. Current recommendations state not to exceed 40 to 50 pounds of N (N not material rate) per acre applied 2 x 2 specifically urea-based N fertilizers. Urea-based fertilizers present the greatest threat due to ammonia volatilization as urea is hydrolyzed (broken down by water). Application of high rates of urea-based products 2 x 2 may not provide a large enough buffer zone between the seed and the ammonia being released. In summary, you are not going to be able to satisfy all of your nitrogen needs through the planter (unless you can offset fertilizer application attachments to increase the distance between the seed furrow and the fertilizer band).

Seed Decisions for 2006 - The Pathologists Perspective

Authors: Anne Dorrance, Pierce Paul

It is time to begin to peruse the company catalogues, websites and flyers to start deciding which varieties or hybrids to plant in your fields next year. When making these decisions, how a variety or hybrid yields should be one of the last points to consider in the process. We did not say that it should not be considered at all, but rather, it should be fairly far down on the list. The first questions that we feel you should ask are, “What problems have occurred in this field? Does this field to be planted to soybeans have a history of Phytophthora, soybean cyst nematode, brown stem rot, Sclerotinia, and/or seedling replant problems? Or does this corn field have a history of seedling replant problems, gray leaf spot or northern corn leaf blight?” All of these disease problems can occur in any given year - what limits them is the environment. So the best and most cost effective means to manage these diseases is to have a resistant variety already in the field when that disease’s favorable environment develops. For example for fields with replant and late season Phytophthora stem rot - choosing a variety that has an Rps gene (Rps1c, Rps1k, Rps3 or combination) PLUS high levels of field resistance (tolerance, partial resistance) is required to provide the best season long protection. For corn, northern corn leaf blight has moved into the state, although it was a late comer during 2005. Choosing corn hybrids with resistance to this pathogen is now essential. As you peruse the literature - keep in mind what has been limiting your yields - then chose the resistance package to manage it - in a high yielding variety or hybrid.

Lodging in Corn: Stalk vs. Root Lodging

Authors: Peter Thomison

This year we are hearing more about lodging problems in corn than we have in several years. Lodging seems more widespread in southwest Ohio because many corn fields in this part of the state experienced greater drought stress. When using the term ‘lodging’ it’s important to know what’s being referred to, especially with regard to hybrid selection decisions. University and seed company agronomists characterize plants with stalks broken below the ear as ‘stalk lodged’ plants. In the Ohio Corn Performance Test (and in other state corn tests and seed company trials), the number of broken stalks in each test plot is determined just prior to harvest and only those plants with a stalk broken below the ear are considered stalk lodged. Stalk lodging is recorded at harvest because it’s usually not evident prior to maturity. Stalk lodging is reported as a percentage of final plant stand. Stalk lodging at two of our test sites in southwest Ohio this year may average as high as 30%.

In contrast to stalk lodging, agronomists describe corn stalks leaning 30 degrees or more form the center, as ‘root lodged’ plants; broken stalks are not involved. Root lodging can occur as early as the late vegetative stages and as late as harvest maturity. Both stalk and root lodging can be affected by hybrid susceptibility, environmental stress (drought), insect and disease injury. Root lodging is frequently attributed to western rootworm injury. However, much root lodging in Ohio occurs as the result of other factors, i.e. when a hybrid susceptible to root lodging is hit by a severe windstorm. A hybrid may be particularly sensitive to root lodging yet very resistant to stalk lodging. A corn field may exhibit extensive root lodging in July but show little or no evidence of root lodging at harvest maturity in September (except for a slight “goose necking” at the base of the plant). As a result, while stalk lodging data is regularly included in corn hybrid test results, root lodging is reported less often.

Sampling for Soybean Cyst Nematode (SCN)

Authors: Dennis Mills, Anne Dorrance, Nancy Taylor, Pierce Paul

Analysis of soil samples for SCN submitted by Ohio growers represents less than 3% of the cropland acres and indicates that about 8% have very high levels of SCN (more than 5,000 eggs/200 cc), 6% have moderate levels (2000-5000 eggs), 18% have low levels (200 - 2000 eggs) and 68% have none to trace levels (0 to 200 eggs). Soybean cyst nematode has become a more serious problem in Ohio because more and more fields are being planted to soybeans for multiple years and the nematode has been introduced into fields by machinery. In Ohio, in most years it is difficult to observe any symptoms on affected plants other than lower yields. When nematode populations are excessively high, or during years with drought, symptoms can include stunting and yellowing.

The best way to manage SCN is to know which fields have nematodes and how many nematodes are present. Fall is the best time to sample fields for soybean cyst nematodes. In the fall the nematodes have finished producing eggs. Sampling in the fall will give an estimation of the population level on which to base management decisions for planting next spring. Soil samples can be sent to some private labs or to The Ohio State University C. Wayne Ellett Plant and Pest Diagnostic Clinic. Fees for SCN testing will be: $15 per soil sample.

C. Wayne Ellett Plant and Pest Diagnostic Clinic
110 Kottman Hall
2021 Coffey Road
Ohio State University
Columbus, OH 43210-1087
614-292-5006
http://ppdc.osu.edu

SCN Soil Sampling Instructions:
1. Use a 1-inch diameter soil probe to collect soil samples (6-8 inches in depth)
2. Following a zig-zag pattern, collect 10-20 soil cores per 10-20 acres
3. Collect cores from areas of similar soil type and crop history
4. Dump cores from each 10 to 20 acre area into a bucket or tub and mix thoroughly
5. Place 1 pint (2 cups) of mixed soil in a soil sample bag or plastic zippered bag and label with a permanent marker
6. Store sample in cool, dark place until shipped to a lab doing SCN analysis.

At trace population levels, ranging from 40-200 eggs per 250 cc of soil, some yield loss may be detected when susceptible varieties are grown. If low populations are detected, ranging from 200-2000 eggs, it is recommended to plant a SCN resistant variety, but some yield loss may occur. Under moderate levels of 2000-5000 eggs of soil it is recommended to rotate to a non-host crop like corn, wheat or alfalfa next year and return with a cyst nematode resistant soybean variety the next time soybeans are planted in the field. When high levels of nematodes are encountered, such as 5000 or more eggs, the field should be rotated to a non-host crop for 2-3 years then the field should be re-sampled before planting a nematode resistant variety to ensure the nematode population has declined enough to successfully plant soybeans again.

Plot Statistics Made Easy

Authors: Alan Sundermeier

On-farm research test plot data can produce very valuable information that can help producers make good future management decisions. However, determining what field data really show can be difficult and in some cases, misleading. Personal biases and judgments made based upon appearances can cause a person to read more into test plot results than what is actually there or true. One may also have the tendency to ignore certain sets of the data because it did not turn out as well as one thought it should. These are some of the reasons why research specialists rely upon statistical analysis to examine data sets.

Unfortunately, statistical analysis is not something that is used by most people on an everyday basis, and statistical analysis computer programs can be expensive and daunting to understand how to use them. Fortunately, there is a relatively easy to use computer program called AGSTATS02, that can be used to statistically analyze on-farm research test plot data. This is a free software was developed by the Pacific Northwest Conservation Tillage Systems Information Source, which is a team of Extension professionals. The software can be downloaded from the following web site:
http://yolo.usda-ars.orst.edu/steep/AgStatsweb/

Some statistical terms with which one should be familiar include the following:

LSD - A common statistical tool for on-farm tests is an LSD, standing for Least Significant Difference. The LSD is a calculation based on the variability of treatment results within the trial and is used to help separate the effects of natural field variability from the treatment effects. If the differences between treatment means in a trial are equal to or larger than the LSD, the differences are statistically significant and believed to be due to the treatment effect and not natural field variability. On the other hand, if the differences between treatment means are smaller than the LSD, the differences are more likely due to natural field variability. The LSD is only used if the analysis determines that treatment differences are significant.

Probability Level - The subscript number following the LSD refers to the "probability level" at which the LSD was calculated. For example, if the differences between treatment means are equal to or larger than the LSD at 0.05 level, then you are 95% sure that the differences are due to treatment effects and not to natural variability. The smaller the probability level, the greater confidence you can have that differences between treatment means are due to treatment effects. A typical statistical probability level is 0.05, but it can feasibly range from 0.001 to 0.2 (0.1 - 20%). Which probability level one uses depends on the economic or environmental implication of choices between management options being tested, interactions with other management practices, the grower's experience and other factors.

WARNING!! To be able to use statistical analysis correctly, one needs to plan ahead and properly design one’s efforts to produce data that can be validly analyzed. Properly conducted on-farm research is not a single strip of a treatment compared to the rest of the field or a split field or field A compared to field B. These types of comparisons are unreliable, and only generate a single measurement of each treatment upon which statistical analysis can not be run. In single side-by-side comparisons, observed numeric differences in data (e.g. differences in germination, stand counts, disease establishment, insect damage, lodging, and yields) may be entirely due to chance because of where treatments were positioned within the field. Do you want to rely on chance to make your management decisions?

Reliable statistically and scientifically-valid on-farm testing must be replicated (minimum of 3 replications of each treatment) with field trials established and managed by the growers with field-scale equipment. Properly designed, grower on-farm tests can separate the effects of natural field variability from the effects of treatments being compared, and can provide an accurate basis for grower management decisions.

The following web sites have further information on conducting on-farm research:
http://ohioline.osu.edu/anr-fact/0001.html
http://sare.org/publications/research.htm

Preliminary CORN Survey Results on Soybean, Aphids and Weeds

Authors: Greg LaBarge

The 2005 growing season had aphids and weeds as primary pest problems. The CORN newsletter staff want to know about your experiences, so we can better prepare for next season. Preliminary results have 752,000 acre of soybeans reported with 74% sprayed for soybean aphids once and 5% sprayed twice. Insecticides for aphid control were sprayed at an average spray volume of 17 gallons per acre and spray pressure of 58 psi. Twenty four percent of the Roundup Ready soybean acres were sprayed with residual herbicides. An average of 1.8 Roundup applications was made during the fall through growing season period. A wide variety of weeds are being report as difficult to control. We will be closing this 10 minute long survey on November 5th. If you would like to add to our survey results please hit this link: http://www.zoomerang.com/recipient/survey-intro.zgi?p=WEB224LWXVCMXN

Archive Issue Contributors: 

State Specialists: Anne Dorrance, Pierce Paul and Dennis Mills (Plant Pathology), Bruce Eisley and Ron Hammond (Entomology), Robert Mullen (Soil Fertility) and Peter Thomison (Corn Production). Extension Agents: Ed Lentz (Seneca), Steve Foster (Darke), Howard Seigrist (Licking), Bruce Clevenger (Defiance), Dusty Sonnenberg (Henry), Greg LaBarge (Fulton), Roger Bender (Shelby), Steve Bartels (Butler), Glen Arnold (Putnam), Harold Watters (Champaign), Curtis Young (Allen), Alan Sundermeier (Wood) and Keith Diedrick (Wayne).

About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.