Ag Connection
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This Month in Ag Connection
Yield Monitors and Precision Farming
Grow Your Own -- Erosion and Weed Control
Electronic Resources on Crops
Determining a Fair Grain Bin Lease
Equilibrium Moisture Content for Shelled Corn
Warning!!! Per hour of use, grain augers are the most dangerous piece of equipment on the farm.
Allowable Storage Time for Shelled Corn
Keep Your Stored Grain in Good Condition
Meeting the Challenge of Volatile Grain Markets
September 1996
Volume 2, Number 9

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Publishing Information
Ag Connection is published monthly for Central Missouri Region producers and is supported by University Extension, the Commercial Agriculture program, the Missouri Agricultural Experiment Station and the College of Agriculture, Food and Natural Resources, UM-Columbia. Editorial board: Maryann Redelfs, Managing Editor; Parman Green, James Rogers, Mark Stewart, Melvin Brees, Don Day and Ron Alexander.

Comments or Suggestions?
Please send your comments and suggestions to Maryann Redelfs, Agronomy/Information Technology Specialist, University Outreach and Extension, 608 E. Spring Street, Boonville, MO 65233, call 660-882-5661, or send messages by e-mail to:

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

Yield Monitors and Precision Farming

Precision farming addresses variability in the field. If fields were uniform, it would be sufficient to measure the total crop removed and apply blanket rates of fertilizer and other crop inputs. However, considerable variability does exist within many fields. Precision farming tools provide methods for measuring, analyzing, and adjusting for that variability.

Measuring the total crop is the way to gauge productivity on a whole field. Yield monitoring provides a site-specific measurement of productivity. The feedback of a yield monitor allows you to better evaluate your fields and production practices and to become a more informed manager. Data from yield monitors can be used to generate yield maps, which reveal differences in fertility, management practices, rainfall, historical farming practices, abandoned building sites, drainage characteristics and pest infestations.

Adding a yield monitor to a combine requires a significant investment of time and money. There may be hidden costs: Will you be using other precision farming technologies? Will you need to invest in a computer and software for mapping or will someone provide that service for you? Can your local agribusiness suppliers provide precision application of chemicals and fertilizers?

A yield monitor alone will cost approximately $3300. A differential Global Positioning System (GPS) can cost considerably more, depending on features and accuracy. The rule of thumb for estimating costs is to spread the costs of a yield monitor and differential GPS over all harvested acres for a period of about 5 years. For example, a $7500 system for a farm of 500 acres would be spread over a total of 2500 acres during the 5 years. The annual amortized investment for this yield monitor and GPS would be about $3/acre.

To maintain accuracy, the GPS needs to be corrected periodically. Subscription to a differential corrections service for your GPS may be another cost. Differential corrections using the U.S. Coast Guard beacon are free. When selecting a differential correction service, you may want to ask for a demonstration or a trial period to see if that particular system will work in your area. Yield monitors have varying features, update policies and service agreements. Consider whether you have the patience to spend a day or two installing a yield monitor in your combine before you opt to 'do it yourself'.

Yield monitoring will add new responsibilities and challenges for the combine operator. The yield monitor will only measure grain as it is about to be introduced into the grain tank. Time lags of 10 to 15 seconds can be expected during operation. These time lags are corrected as the data is mapped. Yield monitors only give an estimate of what enters the header. The combine itself smooths out the flow of the crop as it passes through the various stages of threshing.

Yield monitoring is not perfect. It must be used within its means. It does not replace scales for small test plots. If research is done with yield monitors, that research must be designed within the capabilities of the particular yield monitor that is used.

When buying software to compliment a yield monitor, buy what you need today - not what you might need several years from now. Software changes quickly and your needs will also change. As with any hardware and software, place an appropriate value on the service and support provided with the products. (Bill Casady, University Extension Commercial Agriculture Ag Engineer)

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Grow Your Own -- Erosion and Weed Control

Interest in cover crops is "growing." This interest has been increased by the popularity of no-tilling and the availability of burn-down herbicides. While research backed data is somewhat limited, the following are some well documented points for consideration

The use of cover crops is a well-recognized method of adding organic matter to soil, improving the soil's structure and tilth, providing soil erosion protection, and providing some weed suppression. In its latter stages of decay, organic matter releases nitrogen and other nutrients. Additionally, carbon dioxide from decaying organic matter helps bring minerals of the soil into solution, making them available to growing plants.

Reducing soil erosion and allowing more intensive cropping of highly erodible land are the more obvious benefits of utilizing cover crops on grain acres during the "idle" months. Erosion is reduced by providing surface protection to the soil, increasing its water holding capacity and improving internal drainage.

Some potential disadvantages of cover crops are:

"Covered" soil does not warm up as quickly as bare soil;
During excessively wet springs the "killed" cover can delay soil drying;
During dry springs the cover crop can remove too much moisture.

The uses of winter cover crops are of particular interest since these crops are usually seeded in the fall, normally immediately after harvest, and grow during the months the cropland is traditionally idled. Flying the cover crop on before harvest is another seeding alternative and may allow more time for establishment. Another issue gaining interest is the allelopathic (weed suppressing) effect exhibited by the decomposition of grass type cover crops. The choice of a cover crop depends on the seeding date and the time needed to establish a cover.

Don't forget - the most popular traditional cover crop is red clover seeded into the growing wheat crop. (Parman R. Green, Farm Management Specialist)

The following is a list of the more popular cover crops with suggested drilled seeding rates:
Winter Rye 1.5 bu/acre
Wheat 1.5 bu/acre
Oats 2 bu/acre
Hairy Vetch 20 lbs/acre
Red Clover 6-8 lbs/acre

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Electronic Resources on Crops

Following are listservs and web sites that grain producers may find useful. To subscribe to a listserv, send a message to the address indicated. For more details on listservs, see the June 1996 issue of Ag Connection or contact Don Day or Maryann Redelfs by e-mail, or by telephone at 573-445-9792. (Don Day, Agriculture Engineering Specialist)


CASHCROP A specialty crop discussion group aimed at promoting the exchange of ideas and information about specialty crops, markets, prices, and production around the world.
Subscription address:
Type: subscribe in the message body
NEWCROP New crops discussion list.
Subscription address:
Type: subscribe NEWCROP <your name> in the message body

World Wide Web Sites: - Agronomy Extension Web Page - University of Missouri. Includes the MU Agronomy Technical Report, Corn, Cropping Systems, Grain Sorghum, Soil Fertility, Soybean, Weather Maps, Weeds, Wheat and links to other agronomy sites. - Corn growers handbook, includes corn management information, people with corn expertise, other corny web sites, corny bits of wonder, and the written word of corn. - Includes resources that can be searched by keyword, a research database, and ask an expert.

Caution: Watch where information comes from. Be sure it is applicable to your area. Also, be cautious of the validity of information. Some information is based on some individual's opinion and some is based on research. Look for credentials of those who provide the information!!

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Determining a Fair Grain Bin Lease

What is a fair price for leasing grain bin storage? A common practice is to rent bins for approximately half of the cost of commercial storage. Unfortunately the answer is more complicated than quoting figures, since each leasing situation is unique.

Each situation should take into consideration the location, type of facility, age, size, and interest.

A lease should be based on fixed annual costs, plus variable costs. Following is an example of calculating annual fixed costs.

For example, assume the bin value is $10,000 and holds 10,000 bushels. Equipment (grain spreader, bin sweep auger, aeration fan and motor, unloading auger and motor, etc.) value is $3,000. Total Value of bin + equipment = $13,000. Interest = 9%.

Annual Fixed Costs:
Depreciation -Bin (Value expected life) = (10,000 20 yr. life) = $ 500.00
Equipment (Value expected life) = (3,000 10 yr life) = 300.00
Interest on Investment (( * Total Value) * Interest Rate) = (( * 13,000) * 9%) = 585.00
Bin Repairs (bin value * 1%) = (10,000 * 1%) = 100.00
Insurance (Total Value * .5%) = (13,000 * .5%) = 65.00
Total Annual Fixed Costs = $ 1550.00
Total Fixed Costs / bushel / yr. (1550 10,000 bu.) = $0.155

The renter may be expected to pay the variable costs which include items such as electricity, drying and handling equipment repairs, and drying fuel. These items will vary somewhat farm to farm but following are a few general rules that may be helpful. Electricity (including aeration and augers) can be estimated at approximately 0.25 kwh per bushel. Equipment repairs normally are calculated at 1.5% of original cost.

These are just a few guidelines that may be helpful in trying to determine a fair lease amount for grain bins. Specific questions may be directed to your local University Extension farm management specialist. (Mary Sobba, Farm Management Specialist)

Resources -- Cost of Grain Storage, North Central Regional Publication #217; Determining Grain Storage Costs, North Dakota State University; On Farm Grain Storage: Does it Pay, Kansas State University; and Permanent Grain Storage: Construction and Leasing, South Dakota State University.

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Equilibrium Moisture Content for Shelled Corn*

Using natural air drying at a given air temperature and at a given relative humidity, shelled corn can dry only to a certain percent moisture.

Example: When air is at 50 degrees F and 70% relative humidity, shelled corn will dry to 15.4% moisture, but no more until either the temperature goes up or humidity falls.

*Developed from Chung-Pfost equation, ASAE paper 76-3520.

(Degrees F)
Relative Humidity (percent)
40 50 60 70 80 90
Equilibrium Moisture Content (percent)
35 12.3 13.5 14.8 16.3 18.2 20.8
40 11.9 13.1 14.5 16.0 17.9 20.5
45 11.5 12.8 14.1 15.7 17.6 20.5
50 11.2 12.5 13.8 15.4 17.3 20.2
55 10.9 12.2 13.5 15.1 17.0 20.0
60 10.6 11.9 13.3 14.8 16.8 19.7
65 10.3 11.6 13.0 14.6 16.5 19.5
70 10.0 11.4 12.7 14.3 16.3 19.3
75 9.8 11.1 12.5 14.1 16.1 19.1
80 9.6 10.9 12.3 13.9 15.9 18.9

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Per hour of use, grain augers are the most dangerous piece of equipment on the farm. Take the following precautions:

Replace all safety guards and shields after maintenance work and before going to the field or starting operations at the bin.
Keep all children away from harvesting and grain handling equipment.
Make sure all exposed auger flighting is guarded with grates or solid baffle style covers.
When transporting portable augers, make sure they are lowered and secured in a transporting position before moving.
Check for overhead power lines when positioning. Every year there are accidents involving portable augers and high voltage power lines.
Avoid sharp turns when transporting a portable auger and never transport in the raised position.

(Rick Clark, Ag Engineering Specialist)

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Allowable Storage Time for Shelled Corn

Given shelled corn at a certain moisture level and temperature, there is an associated number of days of safe storage before spoilage begins.

Example: Shelled corn at 60 degrees F and 24% moisture has 11 days of safe storage.

Grain Temperature (Degrees F) Corn Moisture, Percent
18 20 22 24 26 28 30
Days of Allowable Storage
30 648 321 190 127 94 74 61
35 432 214 126 85 62 49 40
40 288 142 84 56 41 32 27
45 192 95 56 37 27 21 18
50 128 63 37 25 18 14 12
55 85 42 25 16 12 9 8
60 56 28 17 11 8 7 5
65 42 21 13 8 6 5 4
70 31 16 9 6 5 4 3
75 23 12 7 5 4 3 2
80 17 9 5 4 3 2 2

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Keep Your Stored Grain in Good Condition

Store grain at 14% moisture or less (long term).

Level the top surface of the grain.

Aerate in the fall to cool the grain to 40 degrees F (do not freeze).

Check and record grain temperatures every 21 days -- aerate when any increase in temperature is witnessed.

Warm grain to 65 degrees F in the spring with aeration fans.

Try to maintain less than 20 degrees temperature difference (degrees F) between average outdoor temperature and grain temperature.

Check for insects -- fall -- spring -- and summer.

(Rick Clark, Ag Engineering Specialist)

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Meeting the Challenge of Volatile Grain Markets

Tight supplies and strong demand describe the factors affecting the grain markets. Corn supplies are at very low levels resulting in the lowest stocks to use ratio in recent history and sending prices to record highs earlier in the year. Soybean ending stocks have also been reduced causing higher prices. To rebuild these grain stocks, a very large 1996 crop was needed. The weather hasn't cooperated and that won't happen. Supplies will remain tight and volatile prices are assured into 1997.

The higher prices are welcome to crop producers, but they also present marketing challenges. Many Central Missouri farmers sold out of last year's corn production at historically good prices above three dollars and then watched prices go over five dollars! A few market rules-of-thumb might help to make plans for the 1996 crop and avoid some of last year's mistakes.

Avoid harvest time sales. Prices are normally lowest at harvest. Even last year's three dollar plus corn prices turned out to be low. If harvest sales need to be made, early harvested crops sold in September typically bring higher cash prices than those sold during the peak harvest month of October. The normal price pattern is for prices to recover, after the lows in October, by late November or during December. These price patterns don't always occur, but the odds favor avoiding corn and soybean sales during October.

Don't sell everything at once. At any time in the market, there is always the risk of lower prices or the possibility for higher prices. By selling only a portion of the crop at any one time, a producer can take advantage of good prices and still have something left to sell if prices go higher. If prices go lower, then at least a portion of the crop was sold at the higher prices. There are a variety of market strategies that accomplish spreading out of sales. Using a scale-up pricing strategy, a producer makes a sale at a good price and then follows up with additional sales as higher price goals are reached when prices are moving up. A scale down pricing strategy requires more discipline since sales are made as prices break lower--the idea being to get some sold before prices break even lower. Other strategies include simply spreading out sales during the year (or a part of the year) at fixed time intervals in order to average prices and avoid selling all during a period of low prices.

Use flexible marketing strategies. This past year has shown that selling at historically good prices can be disappointing if prices go to record highs. However, not taking advantage of good prices is a bad decision if prices drop. Commodity options can provide the flexibility needed to deal with uncertain markets. A put option gives the right to sell futures (or hedge), without any obligation if prices go higher. It allows establishing a minimum price and still being able to take advantage of higher prices if they are offered. Another alternative is to go ahead with cash sales and then buy a call option to offset the sale. This sets the cash price and, if prices go up, the call option can capture some of the price increases. A cash market alternative, that many elevators offer, is the minimum price contract which provides similar benefits to the futures market put option strategy. There are costs associated with using any of these strategies, but understanding and learning how to use them can provide market flexibility.

Avoid letting non-marketing decisions limit marketing decisions. An example of a non-market decision that affects marketing is to delay sales until after December 31 because of income taxes. Tax management is important, but opportunities can be missed if marketing is driven by taxes. Forward cash contracts, futures hedges or put options can be used to make late year sales and take advantage of marketing opportunities while avoiding cash sales for tax purposes.

The grain markets are offering grain producers profit opportunities. Keeping up-to-date with market information, taking advantage of opportunities to learn more about marketing and becoming comfortable using different market tools will allow producers to meet the challenges and take advantage of these opportunities. (Melvin Brees, Farm Management Specialist)

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University Extension Ag Connection - September 1996 -- Revised: February 17, 1997