Your local link to MU for ag extension and research information

To send a message to an author, click on the author's name at the end of the article.

Volume 6, Number 12 - December 2000

This Month in Ag Connection

This Month in Ag Connection | Ag Connection - Other Issues Online]

Building Confidence in Variety Testing

Variety testing performance guides are now available at Outreach and Extension Centers and it is worth every crop farmer’s time to look over the yield data. These are some of the best sources for selecting varieties for next year.

Most agricultural experiments such as the variety trials will have Least Significant Differences (LSD's) listed in the tables. LSD's can greatly benefit your decision making ability if you understand how they work.

Let's say you step off 1/100th of an acre of each of three corn rows in a field and measure the yield in each row. Yield differences are expected to occur between rows. For example: one row will yield 130 bushels per acre, the second 135 and the third 138. It may be that when you average the entire field it yields 115 bushels. Variations can result from soil type, poor drainage, weed infestation, fertility, planting depth or a host of other things. LSD helps to remove the normal variations in an experiment and enhances unbiased results of field treatments.

A common phrase in performance guides is "LSD at the 5% confidence level". This is simply another way of saying there are 95 chances in 100 that this yield variation was due to a variety difference and there are 5 chances in 100 that this was due to unidentified factors.

If the top yielding soybean variety in a test is 50 bushels and the LSD at 5% equals 5 bushels, you can be 95% confident that varieties yielding 44 bushels or less were lower because of variety, not field variations. Top yielding varieties inside the LSD are the ones that deserve the most attention.

Side-by-side strip trials are very common when comparing varieties on farms. The drawback is that they don't accurately account for field variations unless a check variety is used. A check is simply a single variety planted in between each variety in the test or sometimes between every other variety in the test. Final yield results are adjusted across a field based on the variation in the check strips.

Strip trials have a major place in on-farm testing but consider their limitations before putting a great amount of stock in their results. Some seed companies put a lot of stock in strip trials with no replications or checks, but their confidence comes from having many locations to compare. The fewer strip trials there are, the greater the importance of having checks to remove field variability.

Variation is normal, so look for the LSD and the confidence level in small plot tests or the presence of checks within strip trials when you are comparing a new product or farming practice. These will give you greater confidence in variety selection.

(Author: Tim Schnakenberg, Agronomy Specialist)

This Month in Ag Connection | Ag Connection - Other Issues Online]

Rotating Herbicides -- More Than a Name Change

Pesticide resistance was first detected with insect control. An early example was when the insecticide DDT become ineffective against several insects - most notably the housefly. Later, when synthetic pyrethroid insecticides were introduced it was expected that they would not have resistance problems for a long time since they were a different chemistry. Resistance began appearing relatively soon after pyrethroids were introduced. The reason was discovered to be that the mode of action was the same as DDT even though they were very different chemistries.

The same thing happens with herbicides. If the mode or site of action within the weed is the same, then resistance has a chance to build up more rapidly than with herbicides that attack different sites or have different modes of action.

The most common herbicide class involved with weed resistance is commonly known as ALS inhibitors. ALS inhibitors block the amino acid production of acetolactate synthase (ALS). Therefore, plant growth and development are stopped and the plant dies.

The ALS inhibitors come from the chemical groups, imidazolinones, sulfonylureas and sulfonamides. Using different products under these chemical groups is like using the same herbicide.

Herbicides By Mode of Action Include:

Since there are so many different products with the same mode of action, it is easy to repeatedly use ALS herbicides year after year. Farmers should rotate between herbicides based on modes of action rather than brand names. Choose herbicides that are not from the above list, a true herbicide rotation, to avoid weed resistance. As new products enter the market, be sure to identify mode of action.

Other herbicide modes of action include:

Source of modes of action, classes of herbicides, and herbicide names is from the Ohio Field Crops Weed Control Guide.

We may be inadvertently developing weed resistance by using the same herbicide year after year. Repeated plantings of Roundup-Ready soybeans and corn are recent examples of how this can occur. This year waterhemp tolerant to typical rates of Roundup (glyphosate) were detected in northeastern Missouri. This is the first sign that resistance is developing rapidly. Also, Touchdown (sulfosate) inhibits EPSP synthase just like Roundup. Switching between Roundup to Touchdown is not rotating herbicides. Even though tolerance to Roundup is not wide spread, it should be taken as a warning. Rotate herbicides voluntarily before it becomes a necessity.

(Author: Jim Jarman, Agronomy Specialist)

This Month in Ag Connection | Ag Connection - Other Issues Online]

Taxation Tidbits

Long-Term Care Insurance -- Deductibility

Longer life expectancies and escalation of medical and health care expenses have increased interest in long-term care insurance. The deductibility of long-term care insurance premiums can substantially influence the decision to purchase this type of insurance.

For farmers and other self-employed taxpayers, the premiums for a qualified long-term care insurance contract for yourself, your spouse, or your dependents are to be included (subject to the limits listed below) in the "health insurance deduction of the self-employed". The current deductible percentage (1999-2001) for self-employed health insurance is 60%. The deductible percentage increases to 70% for tax years beginning in 2002 and to 100% after 2002.

Limits on the annual deduction for long-term care insurance premiums are the lesser of:

  1. the amount you pay,
  2. the amount shown below opposite the age of the insured person:
    • age 40 or less $210
    • age 41 – 50 $400
    • age 51 – 60 $800
    • age 61 – 70 $2,120
    • age 71 and above $2,660
      (use the age at the end of the year

(Author: Parman R. Green, University Outreach & Extension Farm Business Management Specialist)

This Month in Ag Connection | Ag Connection - Other Issues Online]

Electronic Crop Trail Results


The University of Missouri Crop Performance Testing (Variety Trial) results are on the MU Ag Electronic Bulletin Board at:

Once at the site go to "Crop Performance Testing". Data is online for corn, soybean, grain sorghum, hard red winter wheat, soft red winter wheat and dry bean varieties. To reach the actual data, click on the crop of your choice, then another screen will appear giving you options on how to view the data.

Be sure the data represents the most current year. Information is updated upon completion of harvest and analysis of the data. Once the data is on the website, it stays until the next harvest. Typically, the data on the website is the first information available. The written reports are available about a week after the website is updated.

Although yield usually receives first consideration, other agronomic characteristics may be equally important when selecting a crop variety or hybrid.

Soybean Variety Selection
Standability, maturity, herbicide tolerance and disease resistance are among the characteristics that deserve careful consideration. Several diseases prevalent in Missouri can be devastating to susceptible varieties. Lodging may reduce yields and slow harvest. Poor seed quality is often associated with varieties which mature while temperatures are still high. Late maturing varieties are occasionally killed by frost. Selection of varieties from several maturity groups can be helpful in spreading out harvest dates. Increasingly, tolerance to specific herbicides is important. Therefore, information presented on disease reaction, lodging, herbicide tolerance, and maturity should also be considered when selecting a variety.

Corn Hybrid Selection
Characteristics that deserve careful consideration for selecting corn hybrids are: stalk strength, maturity and resistance to insects and diseases. Later maturing hybrids may require more drying. The maturity classification listed for each hybrid in this bulletin is based solely on information supplied by the entry's sponsor. A hybrid with an abnormally low or high moisture content within a maturity group may be incorrectly classified for Missouri conditions. Poor stalk strength and/or susceptibility to pests may decrease harvestable yield because of lodging or stand loss.

(Author: Tim Schnakenberg, Agronomy Specialist)

This Month in Ag Connection | Ag Connection - Other Issues Online]

Weather Resources on the Internet

At a recent commercial agriculture meeting, Pat Guianan, UMC Department of Atmospheric Science, presented information on weather resources on the Internet. There is not room here for all the sites, but here are some weather sites you might find useful:

(Author: Don Day, Ag. Engineer/Information Technology Specialist)

This Month in Ag Connection | Ag Connection - Other Issues Online

Publishing Information

Ag Connection is published monthly for Central Missouri Region producers and is supported by University of Missouri Extension, the Commercial Agriculture program, the Missouri Agricultural Experiment Station and the MU College of Agriculture, Food and Natural Resources. Managing Editor: Kent Shannon.