March 15, 2002
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Wheat Production Disease Weed Control Insects Fertility Alfalfa and Hay Management Resources CropWatch AgNews
Assessing winter wheat stands and estimating yield potential
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There are several methods of estimating winter wheat yield potential. Two are discussed here. Each method relies on several assumptions that may not be accurate for every season or situation. These assumptions presume that soil moisture and nutrients are adequate, and that weeds, insects and disease are not affecting yields. Added to the uncertainty of yield estimates is wheat's ability to compensate for changes in the environment.
Method 1
Table 1 is easy to use; however, it relies on several assumptions that are required to make a yield estimate in the fall or early spring prior to extensive tillering or stem elongation. These assumptions include:
Method 2
Table 2 was developed using data from 1994 to 1998 as part of the Nebraska Wheat Quality
Tour. These tours were conducted near May 1, prior to head emergence in most of the state.
Factors such as heavy weed/disease/insect infestations or inadequate soil moisture at the time of
the tour may suggest fewer final heads and a lower yield potential than indicated in the table. In
addition, the table becomes unreliable in situations of extremely low or extremely high tiller
counts, or in years when crop development as of May 1 is well ahead or behind normal. For later
season yield estimates, yield predictions can be made by substituting the actual number of heads
per foot for tillers per foot.
To use Table 2, count the number of tillers per foot of row. Again, it is best to use at least 5 feet of row in at least five sites within the field and calculate the average number of plants per foot of row. Be sure you sample sites representative of the field. Locate the column in the table that corresponds to your average number of tillers per foot of row and then move down that column until it intersects with the row corresponding to your row spacing. This is the estimated yield. The table was developed using data collected in the Nebraska Panhandle. For other Nebraska locations, multiply the yield in the table by the following factor:
Southwest Nebraska - 0.9
Central and south central Nebraska -- 0.85
Southeast Nebraska - 0.75
Although these multipliers may appear to be in error - everyone knows that wheat fields in the semi-arid Panhandle usually yield less than fields to the east - on a per head basis the multiplier is correct. Wheat fields in the sub-humid portions of the state produce more heads/acre, but typically fewer kernels/head than in the Panhandle.
For example, if your winter wheat field is in southwest Nebraska and you have an average of 30 tillers per foot of row, and your row spacing is 10 inches, multiply the table results of 40 bushels/acre by 0.9 to get a yield estimate of 36 bushels/acre.
Robert N. Klein
Extension Cropping Systems Specialist
West Central REC
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Growers that are concerned about their wheat can check its health by digging plants and examining the roots and crowns. Remove the soil from the roots, check the color -- they should be white not brown. Slice through the crown; healthy crowns are white; infected ones are tan to brown. The greater the discoloration in the crown the less likely the plant is to survive. You can also check plants by placing them in a glass of water where they should produce new roots from the crown in four to five days. Of course diseased or dead plants will not initiate new roots in the water glass.
Don't be too quick to write off the field. Sometimes fields that look marginal in March can bounce back in April and ultimately produce a decent wheat crop. Refer to the "Assessing Winter Wheat Stands" article on pages 11, 13-14 for guidelines on assessing your stands. Regarding other wheat disease issues, reports from southern Texas indicate that leaf rust and stripe rust are at higher levels there than they were at this time in 2001. Be aware of this situation, but don't get overly alarmed since it is much too early to assess the rust potential for Nebraska. The development of both rusts in Texas, Oklahoma and Kansas will be monitored, and if necessary, growers in Nebraska will be alerted in May in time to treat their wheat.
John E. Watkins
Extension Plant Pathologist
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Another insect whose level of risk should be established early in the spring in western Nebraska is the Russian wheat aphid. This aphid did not survive well through the warm dry summer last year and was difficult to find in fall; however, because of the extended warm fall and winter, aphid populations may have regained a foothold in some areas. It's important to inspect plants for this insect now because of its potential for extreme damage. Early spring thresholds range from about 10-25% infested tillers, depending on yield potential and control costs.
Warm dry conditions across much of the western wheat growing areas of Nebraska may increase populations of the brown wheat mite. These small, rusty-brown mites feed on wheat leaves, causing a yellowish discoloration and spotting. The mite is active through most of the winter and early spring when temperatures are favorable. As warm summer-like temperatures return in spring, they become less active. Brown wheat mites will be most numerous under extremely dry conditions and often are associated with drought-stressed wheat.
Any decision to treat is difficult. If rains don't occur, the stressed wheat will likely do poorly, but if significant rains occur, mite populations will be significantly reduced. Extreme mite populations may warrant treatment to keep plants alive until they can get adequate rainfall. Treatments with dimethoate or Lorsban 4E-SG should provide enough control to limit populations.
Gary Hein
Extension Entomologist
Panhandle REC
These weeds include field pennycress, blue mustard, tansy mustard, tumble mustard, and shepherdspurse. Fields should be checked early for these weeds since they are much easier to control when small and because the earlier they are controlled, the less impact they will have on crop yields. Once these weeds bolt or the stems elongate -- usually in late winter or very early spring, depending on weather and location -- they are very difficult to control.
Blue mustard is the most difficult to control because it bolts early. Applying an appropriate herbicide when the weed is still in the rosette stage provides good control. The most effective treatments have been Ally + 2,4-D, Amber + 2,4-D; and Peak + 2,4-D. Several other treatments also are effective when application is timely. Check page 58 of the 2002 Guide for Weed Management in Nebraska (Extension publication EC02-130) for weed response to postemergence herbicides in winter wheat. The Guide is available at Extension offices throughout the state or on the Web at http:/www.ianr.unl.edu/ pubs/fieldcrops/ec130.htm. Always check rotational restrictions before selecting a treatment. A newly revised and expanded table of replant options and rotational restrictions is on page 102 of the Guide.
2,4-D provides good control of many of the winter annual broadleaf weeds if application is timely, but only fair control of blue mustard. Adding a sulfonylurea herbicide improves control of many weeds and also provides residual control with most of the S.U.'s. This can help control early emerging summer annuals such as kochia if they aren't ALS-resistant.
The bottom line is that winter wheat growers need to scout their fields in late fall or winter to determine if they will need to control winter annual broadleaf weeds in late February or early March in the case of blue mustard, or in March or early April for other winter annual broadleaf weeds. Once plants begin flowering above the wheat crop, it's probably too late for this year. If timed correctly, 2,4-D (8 oz/acre of LV4 ester or 16 oz/acre of 4 lb/gal amine) provided low-cost and effective control of many weeds. Check the weed response table for your weeds. Be sure that wheat has at least four tillers before application.
If winter annual broadleaf weeds are a regular problem, change the crop rotation. Including a spring-seeded crop such as corn, sorghum, soybean, oat, proso millet, or sunflower in the rotation with winter wheat-fallow provides an additional year in which to prevent seed production and allows the soil seedbank to gradually decrease. Additional information or blue mustard can be found in the NU NebGuide, Blue Mustard Control.
Robert N. Klein
Extension Cropping Systems Specialist
West Central REC
Arapahoe accounted for 13% of the acreage and remained second after falling behind Alliance last year. The variety Pronghorn was third with 10.8% and the variety 2137 was fourth with 8% of the State total.
Hard white winter wheat varieties accounted for less than 1% of the 2002 acreage. Nebraska Wheat Varieties Report was made possible with wheat producer check off funds provided by the Nebraska Wheat Board.
An expanded report on 2002 varieties planted by region is available on the Web or by contacting the Nebraska Agricultural Statistics Service at: (402) 437-5541.
By district
Alliance was the most popular wheat variety in northwest Nebraska where over 44% of
Nebraska’s wheat acres are. It was a close second to Arapahoe in the southwest, but was hard to
find in the south, eastern and southeast reporting districts. Arapahoe was most popular in the
central, east and southwest districts and second most popular in the south. Variety 2137 topped
the list in the south while Karl was the most popular in the southeast. Pronghorn’s strong third
place showing was due to its popularity in the northwest and southwest. Buckskin was third
most popular in the northwest, keeping it sixth overall.
This wheat variety data was provided by the voluntary reports of approximately 600 Nebraska wheat producers who responded to the 2001 fall agricultural report. The summary included reports representing 10% of the state’s total planted acreage estimate.
Countering wind erosion
in growing winter wheat
Countering wind erosion
in growing winter wheat
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How can we stop or reduce wind erosion in a field of growing winter wheat? There are several options. If we do nothing and the wind and soil erosion continue, it's likely that the wheat in some parts of the field will be killed. Soil will be lost from already vulnerable spots in the field and end up in fence rows and roadsides - not good environmental stewardship. Two better options are to apply livestock manure or to employ emergency tillage. A heavy application of coarse manure can very effectively stop soil erosion. Apply manure over and upwind from the eroded area.
If the soil surface is not frozen, emergency tillage is an option effectively used by many wheat growers. Use an implement with shanks spaced 48-60 inches apart. Use narrow chisel or shovel points that create small ridges and bring soil clods to the surface. Drive at a field speed and use a tillage depth that create surface clods. Drive perpendicular to the direction of the prevalent winds and begin upwind from the area of active soil erosion. If soil erosion continues days or weeks later, till deeper in the same shank marks to bring up new clods, or, as a last resort, make new shank marks between the first marks. Tillage will be more effective if started before soil erosion becomes severe.
Will emergency tillage damage the growing wheat? If the shank marks can be made at the appropriate spacing and at an angle to the rows of wheat, it will be far less damaging than doing nothing. Only a small percentage of wheat plants will be removed or covered deep enough to be killed. Data from a five-year study at two Kansas sites suggests this type of emergency tillage has minimal effect on potential yield while reducing damage to the growing wheat and reducing soil erosion in moderate erosion situations. This study found that emergency tillage caused the most damage to wheat yields when the wheat had just emerged. The least yield reduction was found when the tillage was in fields with wheat plants already tillered.
For more information on emergency wind erosion control, see University of Nebraska NebGuide G75-282, Emergency Wind Erosion Control, also available from your local Cooperative Extension office.
John A. Smith
Machinery Systems Engineer
Panhandle REC
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A synthetic drug, methamphetamine is a powerful stimulant of the central nervous system which has a high potential for dependence. While 85% of Nebraska's "meth" comes from outside the state, there has been a huge increase in the number of meth labs being found throughout the state in the last two years, according to Sgt. Glenn Elwell, clandestine lab coordinator for the Nebraska State Patrol.
Law enforcement control of the problem is particularly difficult, given that the value of the actual theft of ammonia is minor -- sometimes just a few dollars. However, the contributory impact of the theft can be quite costly in both human and financial losses.
While many of the ingredients for methamphetamine can be purchased in a local farm or discount store, one of the key ingredients - anhydrous ammonia - often is stolen from tanks at local distributors or farms.
For two months each spring, Elwell says the number of complaints of ammonia theft and tank tampering at co-ops drops dramatically. That's when thieves are likely accessing ammonia tanks at farm sites, he said.
"We need to become much more security minded with these tanks. We have to take on the responsibility of thinking about what has to be done to keep someone from stealing ammonia from this tank."
Information developed and distributed by Agriliance in cooperation with the Midwest High Intensity Drug Trafficking Area suggests several steps fertilizer dealers and farmers can take to reduce ammonia thefts. First of all, it's important to recognize the signs of theft and to report incidents. If a thief has been successful at a site once, he or she is apt to return. Tire or foot prints around tanks or leaking tanks indicate someone's been there, as well as buckets or coolers, duct tape, garden hoses or bicycle inner tubes, all of which may be used to drain ammonia and then discarded at the site.
To discourage theft, agribusinesses can:
Producers also can take steps to discourage theft:
Lisa Jasa
CropWatch Editor
If you're like most folks, you don't have much moisture in your soil and if there aren't some good early spring rains, pastures may not grow very fast. And, it's going to take a lot more rain to keep pastures growing through the summer.
What do dry soils this early in the year mean for hay production this year? Forecasters are telling us the the new 'el Nino' developing in the Pacific may mean drier, hotter times for western Nebraska. That extra hay you were planning to sell might turn out to be a lifesaver if these forecasts come true. Only you know how much hay you should keep to protect your feed needs. Bruce Anderson
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If it is greater than 98oF, overwinter survival of flea beetles is expected to be high. If it is less than 80oF, survival is expected to be below normal. Based on the accompanying map for Nebraska, except for pockets of southern Nebraska, most areas of the state did not exceed 98oF. Although conditions in parts of southern Nebraska were favorable for overwinter survival of flea beetles, it does not necessarily mean that flea beetle numbers will be high, since flea beetle numbers were generally not economic in many areas of Nebraska in 2001.
Corn flea beetles overwinter as adults in protected areas near corn fields. They become active in April and feed on a variety of grasses before corn emerges. Corn flea beetles can directly injure corn by feeding on seedling plants; however, probably more importantly they vector the bacterium which causes Stewart's wilt (See NebFact 01-473 for more information on Stewart's wilt).
To minimize damage caused by flea beetle feeding:
Avoid hybrids or inbreds known to be more susceptible to Stewart's wilt (see seed catalog or
local seed company representative).
Avoid early planting dates if susceptible inbreds or hybrids are planted.Seed treatments containing imidacloprid (Gaucho, Gaucho Extra and Prescribe) are systemic and provide some protection from feeding by flea beetles and other early season soil insects. Scout for corn flea beetles on seedling corn. Treatment may be warranted on dent corn if 50% of plants show severe flea beetle injury (plants look silvery or whitish, or leaves begin to die), and five or more flea beetles per plant are found. If susceptible inbreds or hybrids are grown, an insecticide may be needed when two to three flea beetles per plant are present and 10% of the plants show severe flea beetle injury.
A variety of foliar insecticides are effective in controlling flea beetles (Lorsban 4E, 2-3 pt/acre; Sevin XLR Plus, 1-2 quarts per acre, Asana XL, 5.8-9.6 fl. oz per 1000 row-ft; Lannate LV 0.75-1.5 pt/acre; Pounce 3.2 EC 4-8 fl. oz per acre; Warrior T 2.56-3.84 fl. oz per acre).
Bob Wright
Extension Entomologist
South Central REC
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Soil pH is a measure of active acidity in the soil and is used to determine if there is a problem. Soil is tested for buffer pH to determine the amount of lime needed to correct the acidity problem.
Thresholds of soil pH for profitable response to lime application over a 7- to 10- year period are: 6.0 for alfalfa; 5.5 for soybean; and 5.1 for corn. Two or more years may be required to adjust soil pH. If alfalfa is to be established on acid soil, lime should be applied a couple of years before sowing, especially since alfalfa is sensitive to soil acidity during establishment. Liming is a long-term investment and seven to eight years is commonly required to recover the investment. In a trial conducted in Washington County, it took seven years to recover the investment with an 8% interest rate (Figure 1). Producers may not want to invest in lime use when land rental arrangements for eight or more years are insecure.
Because of the delay in payback on the investment, interest rates become very important as $100 obtained at 7% interest costs $197 over 10 years while the cost is $237 if the interest rate is 9%. The long-term effectiveness of all lime products is based on their effective calcium carbonate which is determined from the purity and the fineness of the product. Therefore, 100 lbs of 60% effective ag lime (60% ECC) is as effective as 67 lbs of 90% ECC pelleted lime, although the pelleted lime is expected to adjust pH more quickly than ag-lime. Typically, large amounts of ag lime are applied infrequently while small amounts of pelleted lime are applied every year or every other year to maintain soil pH. (See story comparing the economics of each type.)
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Lime materials need to be well mixed with the soil for quick adjustment of pH; however lime applied to no-till acres generally is not incorporated. It appears that the effect of non-incorporated lime moves downward at less than ˝ inch per year on fine-textured soils of eastern Nebraska (Table 1). For no-till, soil amendment with lime that is not incorporated is likely to be less costly and equally effective if the recommended amount of lime is applied in three applications over a 10- to 12-year period as compared to applying the full amount in the first year.
Charles Wortmann
Extension Nutrient Management Specialist
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There are three basic soil sampling strategies for determining lime requirement.
Traditional sampling is the least costly and grid sampling is the most costly method.
Several factors may cause variation in lime requirements and may provide a basis for zoning a field. Lime requirement may be greater if:
Once zones are defined and sampled, the soil test results need to be considered to determine if site specific application is justified.
The results of grid sampling need to be considered to determine if:
Charles Wortmann
Extension Nutrient Management Specialist
Oats and turnips are inexpensive to grow. At 120 pounds of oats and two pounds of turnip seed per acre, cost should be no more than $20 per acre. Plant as early as possible this spring. While oats can be seeded anywhere from zero to three inches deep, be careful with the turnip seed. Plant it only about one-eighth inch deep. Broadcasting the seed on the surface and packing it with press wheels or a roller works well.
Turnips and especially oats grow rapidly. In about four weeks they might be 3 to 4 inches tall and ready to graze. Continuous grazing, which we sometimes call set stocking, works well with an oats and turnip mix because cattle prefer oats until they start to head. This gives turnips a good chance to get started. Once seed sets on the oats the animals go back and forth in their grazing preference so the oats reseed and turnips continue to grow all the way into winter. Start grazing with about one-half animal per acre and increase the stocking rate as forage growth rate increases. On dryland you may get up to one cow/calf pair per acre; if irrigated, two or more per acre is likely. Growth will slow down in late summer, so have other feed available for that time. With fall moisture, good grazing will be available through December.
Bruce Anderson
Extension Forage Specialist
Roger Elmore, Extension Crops Specialist, South Central REC: Wheat in south central Nebraska had lots of fall growth and was in excellent shape as it went into dormancy last fall. It is too early to tell with any certainty how different cultivars survived the winter.
Noel Mues, Furnas County Extension Educator: Winter wheat went into dormancy last fall in good to excellent condition where it was planted into a well prepared, firm seedbed. Furnas County and much of the surrounding area received about 1 inch of rain last November, during Thanksgiving, and about 10-12 inches of snow on January 31. The snow came with very little wind and provided insulating cover and beneficial moisture. Varieties developed by the University of Nebraska have a high level of winter hardiness and can tolerate this dry, open winter weather much better than less hardy and less adapted varieties.
Larry Peterson, Keith-Arthur-Perkins County Extension Educator: There has been some wind erosion in a few fields, but overall most have withstood the winter winds so far. We did get 2-3 inches of snow March 1 in Perkins County which helped to protect the wheat from the sudden drop in temperature and high winds. Keith County did not get much snow at all so most of the fields there were exposed during the cold and wind. The winter has been very dry and we have had periods of above normal temperatures. Moisture was good at planting and most fields have good stands from good fall growth.
Nebraska Proso, Sunflower, Pulse Crop, Amaranth, Oat and Spring Wheat Variety Tests 2001,
NU Cooperative Extension EC01-107.
Manure Testing: What to Request, NF 507. This publication also includes a form which can
be copied and used to submit a manure sample to one of the labs listed.
Creating a Strong Family -- American Family Strengths Inventory, NF01-498
Nutrient Content and Sensory Characteristics of Bison Meat, NF01-502
For more information, contact Lowell Moser, NU agronomy professor, at (402) 472-1558 or email lmoser1@unl.edu.
Seed quality: Unlike last year, seed quality does not appear to be a problem for most corn or
soybean seed this year, according to Steve Knox, manager of the Nebraska Crop Improvement
Association. Germination percentages of seed tested over the winter were generally in the 90s,
he said. Last year these scores were almost unheard of, with seed often testing in the 70s and
80s.
"Backyard Farmer" moves to Thursday nights April 4: In its 49th season, the hour-long
program will air at 7 p.m. (CT) on Thursdays April 4 through Aug. 29 on the Nebraska
Educational Television Network. It also will be rebroadcast on NETV2 at 9 a.m. and 1:30 p.m.
Friday and 10:30 a.m. Sunday. "Backyard Farmer" features NU extension specialists and other experts discussing and demonstrating garden topics such as pest management, landscaping and other issues related to
the home landscape environment. A gardening calendar each week will help viewers prepare for
specific things that happen during the gardening season.
Individual departments, centers or researchers also have developed sites on particular topics. To locate them, use the IANR search engine.
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