September 14, 2001
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Corn WheatSoybeansProduction Alfalfa Insects Equipment Resources AgNews
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Fusarium, Diplodia (Stenocarpella), and anthracnose are the primary stalk rots observed to date, however weather conditions have been favorable for other stalk rot diseases including charcoal rot (Macrophomina) and Bipolaris stalk rot. The most effective management practice at this point in the season is to monitor fields and determine the level of stalk rot in the field. Randomly walk each field and test stalk strength of 50-100 plants by squeezing the stalk at the lower two internodes. If the stalk collapses between the thumb and forefinger of 25 or more plants, stalk rot disease has advanced to problem levels. These fields are at high risk to wind damage and should be harvested first to preclude lost yield from unharvestable ears.
Stalk rot diseases continue to cause problems for Nebraska's producers. A re-examination of the factors responsible for the high incidences and severities of stalk rot over the last four years is warranted. Planting practices (e.g., minimum tillage, high planting densities, narrow row planting) are evolving and hybrids are being developed to place more energy into yield. This may require a novel management strategy to preclude increased and sustained losses to stalk rot diseases.
Additional information on stalk rot diseases in Nebraska can be found in the UNL Cooperative Extension NebGuide, Common Stalk Rot Diseases of Corn, G99-1385.
Jim Stack
Extension Plant Pathologist
South Central REC
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Three types of wheat crop insurance are available in Nebraska. The Multi-Peril Crop Insurance (MPCI) and the Crop Revenue Coverage (CRC) each are available in 82 counties and the Group Revenue Coverage (GRP) is available in 33 counties in the state. The base or planting time price for CRC is based on the average closing prices on the Kansas City Board of Trade for the July 2002 contract between August 15 and September 14. The average from Aug. 15 through September 10 is $3.35. The $3.35 price can be used to estimate the premium cost for CRC coverage and the revenue coverage the policy will provide.
The Risk Management Agency (RMA), the arm of the US Department of Agriculture that administers the crop insurance program, has set the MPCI price election at $3.15 per bushel. This is an increase from the $2.80 price set last year which means an increase in coverage but also an increase in premium cost for MPCI.
In the last few years the vast majority of wheat insurance coverage in Nebraska has shifted to revenue coverage. Of approximately 1,750,000 acres of wheat planted for all uses in 2000, 1,075,000 acres or about 60% of were covered by CRC, according to Jay Waechter, RMA risk management specialist. Another 381,000 acres were covered by multiperil insurance, Waechter said.
Doug Jose
Extension Ag Economist
Iowa State University developed the corn stalk nitrate test, and its usefulness has been verified in other states. A full explanation of the test can be found in the Iowa State University Extension Publication PM-1584, Cornstalk testing to evaluate nitrogen management, by A. M. Blackmer and A.P. Mallarino and published in September 2000.
What does the test show?
The results of the corn stalk nitrate test indicate whether the corn was over fertilized during the season. Blackmer and Mallarino have calibrated the test to show low, optimal and excess stalk nitrate values (Table 1). Low values indicate nitrogen may have been deficient. Excess values indicate that there was more nitrogen than needed in the plant to produce grain. The scientific basis for this test is the fact that corn will continue to accumulate nitrogen past the level at which grain yield is increased. Since corn does not show visible symptoms of excess nitrogen, analysis of the stalk tissue can determine when this occurs. This test is probably best used for finding excess nitrogen since deficiencies can be spotted visually by leaf yellowing. This season if the
test comes back in the optimum range, that indicates any reduction in nitrogen applied did not cause economic decreases in yield.
How to take the test?
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Remove the sheaths. Don't take diseased stalks or stalks damaged by hail or insects. Take 15 stalks per sample, keep cool and send to the laboratory immediately. Samples should be sent in paper wrapping and not plastic since plastic wrapped samples may mold. Have the samples analyzed for nitrates.
A recent article (Fox et al., July 2001) in the Agronomy Journal compared the stalk test, late season chlorophyll meter, and green leaf count techniques. (An abstract of the article is available below. A full text of the article is available on the Web.)
Based on this article, I have summarized the results of their analysis in Table 2. The authors used experimental data to determine the error rate of using different critical levels to interpret the test results. Because the tests were conducted on corn grown in replicated experiments, they could determine if the diagnostic test level accurately matched the plant response. Their criteria for whether the test was valid was whether the yield was at 93% of maximum yield. For example, with the chlorophyll readings taken at one-fourth milk line they used a critical value meter reading of 52. They derived the 52 reading from their previous research. Once the criteria was set they determined if the treatment correctly predicted sufficient nitrogen or not.
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The data on the stalk nitrates also shows the change of error rates when the criteria for predicting deficiency changes. The Fox et al. data indicates that using 250 ppm would keep prediction errors to 5.7%. Using the 700 ppm critical value used by Iowa had a 0% error rate for falsely predicting nitrogen sufficiency.
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Charles Shapiro
Extension Soils Specialist
Haskell Ag Lab, Northeast REC
We compared six late-season diagnostic tests for determining nitrogen adequacy in corn (Zea mays L.) in a three-year study in Pennsylvania. The six tests were: (i) the NO-3-N concentration of stalk sections at black layer; (ii) the NO-3-N concentration of stalk sections at the one-fourth milk line growth stage (MLGS), which allows corn grown for silage to be tested; (iii) the chlorophyll meter (CM) test at the one-fourth MLGS; (iv) the relative CM test (normalized values) at the one-fourth MLGS; (v) a visual test based on the number of green leaves below and including the ear leaf at the one-fourth MLGS; and (vi) a relative visual test (normalized values at the one-fourth MLGS).
We found that with a critical level of 250 mg kg-1 NO-3-N, the stalk NO-3 test separated nitrogen-sufficient from nitrogen-deficient sites with approximately 93% accuracy when sampling was done at either the one-fourth MLGS or within several weeks after black-layer formation. It appears that the 250 mg kg-1 NO-3-N critical level can be used to accurately predict nitrogen adequacy for any sampling time between the one-fourth MLGS and a few weeks after black-layer formation.
When drought-stressed fields were excluded or the CM readings normalized with a high-N reference plot in the field, the accuracy of the CM test at the one-fourth MLGS was approximately 92%. The visual test at the one-fourth MLGS was an accurate predictor of corn nitrogen status only when visual readings were normalized with a high-N reference plot. These results demonstrate that there are several late-season nitrogen tests that are suitable for making relatively accurate assessments of nitrogen sufficiency for corn silage and grain yields.
Abstract reprinted with permission from the July 2001 Agronomy Journal (93:590-597), published by the American Society of Agronomy.
Storing grain requires informed and active management. Improper storage can result in a lower quality product, loss of grain mass, and sometimes spoiled or moldy grain. The two most important factors in grain storage are the grain's temperature and moisture content. A farmer has some control over temperature with aeration and careful attention. With higher airflow rates, moisture also can be removed.
Why aerate?
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Above the threshold temperature and moisture content, stored grain will respire, (carbohydrates in the grain combine with oxygen from the air releasing carbon dioxide, water, and heat). When grain respires, dry matter is lost. This dry matter loss is analogous to burning the grain in a fire (which also produces carbon dioxide, water .... and heat). Left unchecked, a runaway reaction can occur in a mass of wet grain. The heat produced by the respiration process warms the grain mass, which in turn results in higher respiration rates which causes greater dry matter loss and more heat production to continue the cycle.
Known as storage molds, various fungi species can grow on stored grain if it is above thethreshold moisture content and temperature. Like all aerobic organisms, storage molds also respire (they consume carbohydrates and oxygen and release carbon dioxide, water, and heat).
Molds also lower the grain quality by virtue of their presence in the grain by adding offensive odor, taste, and dust. Some mold species also produce toxins which can be harmful if consumed in sufficient quantity. The best way to prevent loss of dry matter and a reduction in grain condition from molds is tostore only dry grain (below 15% moisture). Alternatively, one can use aeration to keep the grain mass below 50oF and extend the storage life by reducing mold activity.
In Nebraska cool air temperatures usually follow harvest. Given sufficient airflow rates and cool outside air temperatures, aeration can be used to cool grain in the bin. Depending on the airflow rate, one should expect a cooling front to take many days to a few weeks to move all the way through a bin of grain. A fan must run continuously until the grain is cooled to the proper temperature.
Experts discuss the shelf-life of corn as the point at which one-half of one percent of the dry matter has been lost. Corn at 16% moisture that went into storage at 50oF, followed by careful monitoring and periodic aeration to maintain a constant 50oF in the grain, will have a shelf life of about 186 days (six months). The shelf life drops dramatically at higher moisture contents. Corn at 18% moisture and a constant 50oF will have a shelf life of 128 days (four months). At 20% moisture and 50oF, the shelf life is only 63 days (two months). A rule of thumb is that shelf life drops about one month for every point of moisture above 16% when the grain is maintained at 50oF with aeration. Higher temperatures reduce shelf life even more dramatically. At any given moisture content, the "shelf life" is less than half as long for every 10oF increase in temperature above 50oF. For example, for corn at 16% moisture content, the shelf life (with aeration) is 186 days when held at 50oF, 81 days at 60oF, and 45 days at 70oF. NebGuide G87-862, Holding Wet Corn With Aeration, includes a chart showing the shelf life of grain over a range of moisture contents and temperatures.
Airflow rates
Airflow rates as low as 0.1 cubic foot per minute per bushel (cfm/bu) have been successfully used to hold grain that is at or less than 16% moisture during the cooler part of the year. Greater airflow rates (0.33 to 0.5 cfm/bu) are recommended to hold grain that is placed into storage at moisture contents above 17% or grain that goes into storage above 70oF. The fractional cfm/bu airflow rates that are used for aeration can only be expected to keep grain from heating and to very slowly cool grain when air temperatures that are cooler than the grain mass. Much higher airflow rates (2.0 cfm/bu or higher) are needed to remove appreciable moisture from the grain.
For more information on drying grain, refer to NebGuide G85-760, Natural Air Corn Drying. Further information, publications and resources on grain aeration and drying are available on the Lancaster County Extension web site on the Grain Storage page.
Tom Dorn
Extension Educator, Lancaster County
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You may see them in some counties bordering Kansas this year.
Kansas State University entomologists report that southwestern corn borers were seen in Jewell County Kansas in 2000. Jewell County is just south of Superior, Nebraska.
Historically, `southwestern corn borer have rarely been reported in Nebraska; however there were reports of the insect being found at low levels this summer in south central Nebraska. Winter temperatures are thought to influence their northern limits.
Southwestern corn borers, Diatraea grandiosella, belong to the same insect family as European corn borer, and share many similarities in their life cycle. In Kansas and Nebraska there are two generations a year, with timing similar to European corn borers.
Eggs are laid in masses and have an appearance similar to that of the European corn borer (flattened and overlapping like fish scales). One difference is that as southwestern corn borer eggs develop, three orange-reddish lines develop across each egg. Larvae are white with large raised black spots on each segment.
They are 1.0 - 1.25 inches long at maturity. The second generation of southwestern corn borer is most damaging, both from stalk boring activity and because it girdles the base of the corn stalk in preparation for overwintering. This weakens the stalk and makes stalk breakage more likely.
KSU entomologists recommend applying insecticides when 20% to 25% of the corn plants are infested with eggs or newly hatched larvae. Southwestern corn borer may survive in sorghum as well as corn.
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The soybean stem borer is a member of the beetle family Cerambycidae (long-horned beetles). It is a native insect which feeds on wild hosts including cocklebur, sunflowers, and common and giant ragweed, as well as soybeans. The adults are elongate, gray beetles, about 0.25-0.40 inch long, with the antennae longer than the body. Adults lay eggs in the upper leaf petioles of soybean during July and August. Newly hatched larvae feed in the petiole pith initially but soon tunnel to the main stem. The trifoliate leaf where the egg hatched and the larva began feeding will wilt and die. Larvae tunnel in the stalk until they complete their development. Soybean stem borer larvae are slender, legless, and creamy white in color, reaching 0.60 inch at maturity.
Larvae overwinter in the stalk, pupate in early summer, and adults emerge from June to September.
As they finish feeding, last stage larvae move down to the bottom of the stem, and girdle the inside of the stem 2-4.5 inches above the soil level. This predisposes the soybean plant to break at the girdled point during windy periods. Up to 10% yield reduction has been reported from the effects of larval tunneling but the greatest yield losses occur due to lodging. The borer girdles earlier-maturing varieties more severely and lodging is most severe on earlier-planted soybeans.
Insecticides are not recommended for control; they are ineffective for control of overwintering larvae. Adults can be controlled with foliar sprays, but because of their extended period of emergence treatment is not feasible.
Cultural practices suggested to reduce losses include harvest of infested fields as soon as maturity is reached, crop rotation, and control of weed hosts.
Additional information on both of these pests is available from the Kansas State University web site at:
Bob Wright
Extension Entomologist
South Central REC
Freezing slows down metabolism in all plants. Alfalfa reacts in two ways. Nitrate levels can increase, but rarely to hazardous levels. Freezing also causes alfalfa to be more likely to cause bloat for a few days after the frost. Then, several days later after plants begin to wilt or grow again, alfalfa becomes less likely to cause bloat. Waiting to graze alfalfa until well after a hard freeze is a good, safe management practice.
Bruce Anderson
Extension Forage Specialist
Bruce Anderson
Extension Forage Specialist
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Uneven stands may be caused by a variety of factors. While it may be difficult to determine at harvest exactly what caused uneven stands, there may be some clues. For example areas with smaller diameter stalks and longer internode distances may indicate a shallow planting depth where good moisture wasn't available for immediate emergence.
With corn it's good for all the plants in a field to emerge within one to two days to provide for equal competition. Plants emerging just four to five days later than other plants may act more like weeds, using resources, but contributing little to yield. If yields are less than expected in some "hot spots", take this opportunity to determine possible causes and look for amendments or practices to change for next year. First try to identify or mark the location of the problem. Yield monitors and GPS systems can make site identification easy. If these tools aren't readily available, keep a clipboard handy in the combine to make notes. Mark field ends with various colored flags or use farm landmarks to reference the site location.
After harvest, return to assess the situation. If yields were lower than expected, test the soil for organic matter, nutrients, pH and compaction. Try to determine the extent of the variance between that area and the rest of the field and whether it's economical to address the problem.
Low areas may need to be drained or amendments may need to be added to targeted areas. If organic matter is low, soil texture is coarse and/or the pH is high, herbicide rates may need to be reduced in the identified area next year to avoid crop injury. Similarly, if yields are higher than expected in specific areas, try to determine what's contributing to the increase and whether it's cost efficient to bring the rest of the field up to that level.
Some identified problems can be addressed in the fall; however there's no reason for fall tillage except to break up compaction.
Especially with corn, if doing fall field work such as cutting stalks, take steps to limit winter erosion. For example, leave six to eight rows of stalks standing at intermittent intervals to slow the wind and trap snow.
The combine seat also provides a vantage point for a season end evaluation of weed management. Field notes and maps of weed infestations made during harvest can be used in planning next year's weed management program. Every field is different so be sure to make a map with notes rather than relying soley on your memory.
Locate large patches of perennial weeds such as Canadian thistle and hemp dogbane, for example, and if time permits, treat this fall or prepare to treat in the spring. A weed patch present at harvest may be telling you something that is not so obvious.
Normally we may think that weed patches indicate a need for "stepping up" our weed management program a notch or two; however the problem may lie deeper than meets the eye. Weed patches may result when the crop canopy is thin in an area. A thin canopy could be the result of a reduced crop stand resulting from improper planter adjustment/operation or low crop vigor due to seed quality, low soil nutrients, or other soil related problems. Correcting these fundamental problems will increase crop yields and help with weed control.
Bob Klein
Extension Crops Specialist
West Central REC
Paul Jasa
Extension Engineer
Alex Martin
Extension Weeds Specialist
Now, back to 2001 . . . . This is a good time to dig plants and check for nodules so you can easily answer questions for future soybean plantings. A uniform crop canopy and color in your soybean fields now may simply signify high residual nitrogen and not necessarily whether the crop was well-nodulated. Get out the shovels and dig up plants. Carefully shake soil from the roots and inspect the tap root and lateral roots for nodules. Record your observations on your field maps or field reports. This will excellent information for you next time you intend to plant soybeans.
Roger Elmore
Extension Crops Specialist
A yield monitor consists of several sensors and a small computer to integrate, display, and save the information. On most yield monitors, the grain flow through the combine is estimated by measuring the force the grain exerts on a sensor at the top of the clean grain elevator. The greater the grain flow, the greater the force or displacement measured. The area harvested is determined from the measured travel speed and the known width of cut. Grain moisture content is also measured so that the grain yield can be corrected to a standard moisture content and estimated on a per acre basis.
In reality, the output from the sensors on the combine are not grain yield and moisture content but only millivolts. Proper calibration involves weighing the grain in a load using a scale and measuring the moisture content with a standard moisture tester. These numbers are entered into the yield monitor's computer, allowing the computer to assign mass flow rates and moisture contents to the millivolt readings sensed. This calibration must be performed separately for each crop. A Checklist for Yield Monitor Operation and Calibration can be found at a Ohio State University web site.
Unfortunately, many producers think that calibration consists of harvesting a truckload of grain, calling that a load on the yield monitor, and weighing that load on a scale to get the bushels harvested, using that as input to the yield monitor. Later they may harvest several truckloads, weighing them all as one load, and inputting that number into the monitor as another calibration point. They think they have entered two calibration loads, or more if they do more truckloads.
This procedure actually only provides one calibration point - based on the average mass flow through the combine at "normal" operating conditions, usually full load. The proper calibration procedure for most monitors usually consists of harvesting several loads, under various mass flow rates, to calibrate the mass flow sensor across the variety of flow rates that occur during harvest. The first load may be at normal operating conditions like the producer above. However, the next loads should be at reduced mass flow rates, like 1/2 speed (or 1/2 width of cut) and 3/4 speed (or 3/4 width of cut) and 1/4 speed (or 1/4 width of cut), and so on to get a variety of flow rates. This calibrates the mass flow sensor for the high and low flow rates that occur when harvesting high and low yielding areas in the field. Consult the yield monitor owner's manual for the proper procedure recommended, especially for the number of loads required for proper calibration. Follow the directions and don't skip the low flow rate calibration loads thinking it is waste of time to operate the combine at such reduced capacity.
Most yield monitors can show grain flow rate through the combine (in bushels per hour). Research and experience has shown that an improved calibration can be obtained by using this reading on the display to operate the combine during calibration. Rather than varying the speed or width of cut for each calibration load, the flow rate should be held constant within a load and varied between loads. This is achieved by using the hydrostatic drive to vary the ground speed to keep the flow rate constant for each load. For instance, if during normal operating conditions for harvest the grain flow rate is 1800 bushels per hour, calibration loads should be run at 600, 900, 1200, 1500, 1800, and 2100 bushels per hour. This method provides a better calibration of actual flow rate of grain across the sensor.
When comparing the scale weight of a load to that recorded by the yield monitor, producers should resist the temptation to input an "extra" load or two at full load conditions, trying to improve the calibration. For each load entered at full load conditions, the corresponding loads should be entered for all the reduced flow rates to keep the sensor calibrated across the full range of operation. Extra data points at full load conditions can skew the calibration curve so that values recorded at anything other than full load may not be accurate.
Even with the best calibration procedures, the yield monitor will still have some errors. They should not be used to determine the exact yield of a field or portions of a field. Rather, they are a valuable tool for exploring relative yield differences from various areas of the field, one of the many starting points for site specific crop management.
Paul Jasa
Extension Engineer
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Harvest is a perennially hectic season, but extraordinary risks shouldn't be taken to get a job done faster, an Institute of Agriculture and Natural Resources specialist said. Amid the rush, farmers should invest time on safety precautions.
Agriculture is the second most dangerous industry in the United States, with 770 deaths and 150,000 disabling injuries reported in 1999. In Nebraska in 2000 there were 20 farm fatalities and already in 2001 there have been 13.
Farmers work longer hours during harvest. This means they're working after dark with limited visibility and often don't get enough rest. If farmers aren't careful, either or both could lead to injury.
"At night, farmers work with machines and can't see moving belts and rotating shafts. With low visibility you need to be cautious of what's around you," said David Morgan, University of Nebraska safety engineer.
Fatigue takes both a psychological and physical toll on farmers, he said. It's important for farmers to take breaks throughout the day to reduce fatigue. Farmers should take 5 to 10 minute breaks every hour or longer 15- to 20-minute mid-morning and mid-afternoon breaks.
Handling grain also can be a health hazard. Whether moving grain or working in the grain bin,there's always a danger of suffocation or respiratory problems.
Farmers should wear filter masks if they're sensitive to organic dusts stirred up by handling grain or silage farming, Morgan said.
Check all equipment, including tire pressure and brakes, before going into the field. Morgan recommended cleaning tractor and combine cab glass so drivers can see clearly what is happening and who is around them.
"Make sure warning lights are functional so motorists can see the equipment when you're on the road when visibility is reduced," Morgan said.
Another common cause of injury during harvest season is falling off farm equipment. For more information, visit the National Safety Council's web site.
Harvest is a peak period for farm accidents. Taking a little extra time now to prepare can mean fewer injuries and fewer delays later. The Council reminds farmers to take these safety measures:
Dave Morgan
Extension Farm Safety Specialist
Doug Jose, NU ag economist and host of Market Journal, discussed the advantages and disadvantages of a new electronic trading system with Gene Kunda, senior economist with the Chicago Board of Trade, and Roy Huckabay, vice-president of the Linn Group. The Sept. 13 broadcast is available on the Market Journal web site for viewing and/or listening.
Members of the Chicago Board of Trade will decide whether to change the markets from the open outcry system to a computerized one.
"There's honestly a real question whether the electronic system could handle that volatility and volume whereas we've never been over-capacitated or over-taxed in open outcry," Kunda said.
"There's a lot of fat finger errors that can occur whereas if you have open outcry sometimes, there's still a human element."
Since the electronic system is technologically advanced, overtaxing it would be difficult, Kunda admits. An electronic system also can reduce problems with back logs and paper trails.
The Chicago Board of Trade has already established some electronic markets which are beneficial to retail-oriented customers, but most large commodity orders are still completed through the open outcry system.
Huckabay's trading group has found great success using an electronic system. "I'd say 70% to 75% of our orders end up in the pit electronically," Huckabay said.
Also appearing on the program are Roy Smith, Plattsmouth grain farmer and market analyst and Al Dutcher, NU state climatologist. Smith will give his thoughts on current and future market trends and Dutcher will discuss upcoming climate conditions.
The Sept. 27 edition of Market Journal will address how the 1998-1999 mandatory livestock pricing regulation affected marketing for livestock producers. All large packers were required to report prices paid for livestock, any movement of livestock and all meat to be exported.
Jose will host Leland Sutherland, senior economist for the USDA Economic Research Services (ERS), will discuss the act and a ERS pilot study. The study will look at retail prices, price spreads and movement of livestock markets. Data will be collected at various stages then analyzed and compared.
For more information about the ongoing Market Journal broadcasts, visit the Market Journal web site.
Paul Hay, Extension Educator in Gage County: Chinch bug and greenbug pressures were greater this year than some producers realized. Some preharvest checks of grain sorghum fields are indicating greater than expected damage. Generally, crops in southeast Nebraska look quite good. Some scattered areas of hail and high winds have taken the edge off yields. The earliest planted no-till corn fields are beginning to be harvested, providing dryland yields in excess of 100 bushels per acre.
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