October 18, 2002

Soybean harvest is well underway across much of the state with yields varying due to this year's conditions. Photo by Brett Hampton

In this week's Crop Watch:

"This is not a crisis, but it is a situation that needs to be monitored and managed," said Jim Stack, UNL plant pathologist and moderator of an October 9 videoconference on the topic. Much of the corn at issue is from dryland fields or irrigated fields that underwent stress during this year's drought.

This disease, which is caused by Cercospora kikuchii, is widely distributed in Nebraska and occurs every year at low levels. This year, however, conditions were excellent for its development. While this disease generally does not reduce yield, it will reduce seed quality and can impact seedling quality if planted next year.

Purple or pink streaks on the seed coat are the primary symptom of purple seed stain and discoloration can range from streaks to large blotches. The fungus grows into the pod and spreads though the hilum, resulting in seed discoloration being centered on the hilum. In some cases the entire seed may be discolored. The fungus overwinters on soybean residue. Spores are splashed onto plants during the growing season and the fungus grows into the pod.

Conditions that favor purple seed stain develop when wet weather delays harvest or warm, wet weather hits when plants have begun to reach maturity (growth stages R7 and R8) or when pods are completely brown. This has been the case in Nebraska in many fields. In some fields, stress conditions forced plants to mature prematurely. These plants did have pods with seed, many of which have purple seed stain. Rapid dry-down prevents seed infection and recent cool weather slows the rate of fungus growth, but if moisture continues into harvest I expect there to be an abundance of this discolored seed.

Treatment should begin after alfalfa has gone dormant. Winter annual weeds will have germinated by this time and alfalfa can be safely treated with the appropriate herbicide. Many useful herbicides can be used only while the alfalfa is dormant. There also is more time available in fall than in spring to make the applications.

When selecting a herbicide, consider target weed species and establishment stage of the alfalfa. Karmex, Sencor, and Velpar can be used only on dormant alfalfa established for one year or longer. All three herbicides are effective against most winter annual broadleaf weeds. Sencor and Velpar also are effective against downy brome. Some residual control of summer annual broadleaf weeds is also afforded by these herbicides.

Several herbicides can be used both on the current year's stands as well as on older stands of alfalfa. Poast, Pursuit, and Select are not restricted to dormant alfalfa. Poast and Select provide control only of emerged annual grasses. Pursuit controls primarily broadleaf weeds. Gramoxone Max will control emerged winter annual grass and broadleaf weeds in dormant alfalfa. MCP Amine will control emerged winter annual broadleaf weeds in dormant alfalfa.

Livestock eating frozen sorghum can get a sudden, high dose of prussic acid which may kill them. Fortunately, prussic acid soon turns into a gas and disappears. Waiting three to five days before allowing livestock to graze sorghums will lower the chance of poisoning.

Freezing slows metabolism in all plants. In some plants, especially grasses, this stress causes nitrates to accumulate. This build-up usually isn't hazardous to grazing animals, but green chop or hay cut right after a freeze can be more dangerous.

Alfalfa reacts two ways to a hard freeze. 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.

The annual conference, which is sponsored by the Nebraska AgRelations Council and the UNL Department of Agricultural Economics, will be held from 8:15 to 4:45 on Thursday, Nov. 7, at the UNL East Campus Union.

The keynote speaker, Susan Offutt, administrator of USDA's Economic Research Service, will speak on "Farm Households, Farm Policy and Rural Economics."

Ray Supalla, conference chair and UNL professor of agricultural economics, said Offut was likely to address how changing trends in the level and source of farm income are likely to have far reaching implications for future ag policy and commodity programs.

USDA statistics indicate that one-third of farm operators have worked off-farm essentially full-time since the 1970s. Not surprisingly, large farms -- USDA defines them as those with over $250,000 in annual sales -- showed a smaller percentage of their total income from off-farm sources, although that percentage has been increasing, according to a report in the September Agricultural Outlook, USDA's Economic Research Service publication.

In 2000 almost one-third (32.5%) of operator household income was from off-farm sources. The Outlook article, "Does Off-Farm Work Hinder 'Smart" Farming?' addresses how this trend may curb the adoption of "smart farming" practices which substitute management for capital. The trend also is likely affecting the quick adoption of "convenience agriculture" practices such as the using genetically engineer crops.

Conference registrations are required by 5 p.m. Monday, Nov. 4 To register, send your name and address and a check for $35 (non NAC members) to Nebraska AgRelations Council, 104 ACB, Box 830918, University of Nebraska, Lincoln, NE 68583-0918; call (402) 472-2821 or fax (402) 472-0025. Conference presentations are expected to be available via an archived webcast at a later date at marketjournal.unl.edu

Scheduled speakers

A schedule of topics and speakers follows. The afternoon will include two sets of concurrent sessions so participants can select among topics.

8:00	Registration, coffee and rolls
8:30	Welcome and introductions, Craig Buescher, NAC Vice President, Deweese
8:45	"Farm Households, Farm Policy and Rural Economies?", Susan Offutt, Administrator, USDA Economic Research Service
9:45	"Rural Development in Nebraska: Issues and Options", Sandy Scofield, director, Rural Development Initiative, UNL
10:30	Break
10:45	"Financing State and Local Government: Issues and Options", Senator Ronald Raikes, Lincoln
11:30	"Nebraska Water Policy: Conjunctive Use and Water Marketing Issues and Options", J. David Aiken, Agricultural and Water Law Specialist, UNL
12:00	"Drought Management in Nebraska", Mike Hayes, National Drought Mitigation Center, UNL
12:30	Lunch; Jeff Royer, Head, UNL Department of Agricultural Economics, presiding. Luncheon address: "Coping with Stress", Dr. Val Farmer, Fargo, North Dakota
2:00	First rotation of concurrent sessions
	Session 1: Rural Development, Sam Cordes, facilitator, Sandy Scofield, resource person
	Session 2: Public Finance, Bruce Johnson, professor, UNL ag economics, facilitator; resource persons: Senator Raikes and Senator Wehrbein
	Session 3: Water and Drought, Mike Jess, Acting Director Water Resources Center, UNL, facilitator; Dave Aiken and Mike Hayes, resource persons
3:15	Break
3:30	Second rotation of concurrent sessions
4:45	Adjourn

The onset of flowering and regional adaptation are controlled by length of the photoperiod. Soybeans are short-day plants, which means the plants will develop vegetatively until a critical day length is reached that triggers the flowering response. Southern U.S. varieties respond to long days and mature too late for northern climates while northern varieties respond to shorter days and mature too early in the south. In Nebraska flowering usually begins in early July as the day length decreases after the maximum day length on June 21.

Indeterminate vs. determinate

Soybean varieties differ in growth habit and maturity. Indeterminate types begin flowering at the middle to lower nodes and flowering progresses upward and downward on the plant. Plant height increases continue until R5.5 (seed fill). In contrast, maturity group II and III determinate varieties achieve 80% of their main stem growth by the flowering stage with 92-93% attained within one week after flowering. Determinate and semi-determinate varieties typically are shorter, have fewer nodes, have lower pod heights on the main stem, and lodge less than indeterminate varieties.

Freezing temperatures ended the growing season this week and soybean harvest increased across the state. As of Sunday, The Nebraska Agricultural Statistics Service reported that soybean harvest was 54% completed. Photo by Brett Hampton

Nearly all soybean varieties in maturity groups IV and lower are indeterminate types, with flowering activity spread over a three- to five-week period once the critical day length has occurred. In the early 1970s lodging was thought to be a yield-limiting factor of traditional tall indeterminate varieties. Subsequently many determinate varieties adapted for northern latitudes were released beginning in 1977. Maturity group 0-IV determinate varieties are largely products of public breeding programs, although a few semi-determinate varieties are available from private seed companies.

Determinate varieties have played an important role in Nebraska production since 1977. In high-yield environments determinate varieties (maturity groups II - III) have yielded better than indeterminate varieties and yielded similar to indeterminate varieties with stress during the late vegetative and reproductive stages.

A concern among producers is that shorter plants often have lower pods. Stress during vegetative stages can reduce pod heights of determinate varieties and increase potential harvest losses. Breeding efforts are underway to increase the lowest pod heights of determinate varieties.

Herbicide resistance

The development and 1994 release of varieties resistant to herbicides represented the beginning of a new era in cultivar selection and weed management systems. Sulfonylurea-tolerant (STS) soybean varieties were the first herbicide-resistant soybean varieties; they were selected and developed through conventional breeding practices. Subsequent herbicide-resistant releases included biotechnology-derived (transgenic), glyphosate and glufosinate varieties. Well over half of the U.S. soybean area is planted to glyphosate resistant (GR) soybean varieties with some states having more than 70% in these varieties. This new technology brings both advantages and disadvantages.

For more information Roger Elmore, Extension crops specialist, and a team of specialists and researchers from the University of Nebraska Lincoln have written a NebFact reporting their research on yield effects from glyphosate resistant soybeans. The NebGuide, "Yield Suppressions Associated with Glyphosate-resistant (Roundup Ready) Soybeans" NF02-539, should be available in county Cooperative Extension offices in late October or early November.

The main advantage is good weed control. In addition, herbicide costs and soybean injury may be reduced and producers may have increased flexibility in timing herbicide applications and may have fewer weed control decisions. Net returns may be greater than those from conventional herbicide systems due in part to the relative prices of glyphosate and other herbicides.

Conversely, there also are disadvantages for the glyphosate resistant soybean weed management system. Timing glyphosate application is a balance between maximum, season-long weed management and controlling weeds before they suppress crop yields. High winds in spring may limit spray opportunities due to the potential for herbicide drift. Weed competition may become intense to the point of limiting yields before spraying is possible. In some situations, conventional herbicides and varieties are more profitable. Because of higher seed costs, lower seeding rates of herbicide-resistant varieties may be justified when compared with nonherbicide-resistant varieties.

In addition to these disadvantages, comparisons from side-by-side variety performance trials suggest a yield suppression may exist relative to nonherbicide-resistant soybeans. Yield suppressions may result from either variety genetic differences, the glyphosate-resistant gene/gene insertion process, or glyphosate. Grain yield of glyphosate-resistant soybeans, however, is probably not affected by glyphosate.

In a Nebraska study, five backcross-derived pairs of glyphosate-resistant and nonglyphosate-resistant soybean sister lines were compared along with three high-yield, non-herbicide-resistant varieties and five other herbicide-resistant varieties. In contrast to the unpublished Monsanto report, glyphosate-resistant sister lines yielded 5% (3 bu/acre) less than the nonglyphosate-resistant sisters. High-yield, non-herbicide-resistant varieties included for comparison yielded 5% more than the nonglyphosate-resistant sisters and 10% more than the glyphosate-resistant sister lines.

Considering costs and assuming a 5% yield suppression, conventional herbicides and varieties may be the most profitable weed management system if weeds are controlled. However, if the weeds are difficult to control with conventional herbicides, the glyphosate-resistant weed management system may be more profitable. Producers should consider the potential for 5-10% yield differentials between glyphosate-resistant and nonglyphosate-resistant varieties as they evaluate the overall profitability of producing soybean. Variety choices are best based on: 1) previous weed pressure and success of control measures in specific fields, 2) the availability and cost of herbicides, 3) availability and cost of herbicide-resistant varieties, and 4) yield, and not solely on whether varieties are herbicide resistant.

Specialty varieties

Soybean producers can select from among several specialty varieties when planning their 2003 production. The following describe some of the more popular speciality soybeans available for Nebraska.

1. High protein: High protein soybean varieties may improve competitiveness of U.S. livestock producers. Unfortunately the strong inverse relationship between seed protein and grain yield has limited breeding progress. High protein maturity group II to V lines are now available to produce over 46% seed protein and meal with more than 50% meal protein. Breeders are developing high-yield soybean varieties with higher protein.

2. Large andsmall seeded/vegetable soybeans: Markets are available for specialty soybeans of different sizes. Natto is a Japanese food made from mature, small-seeded, cooked, fermented soybean. Small-seeded varieties are also used for sprouting. Large-seeded speciality soybean varieties are used as edamame, or vegetable soybean. These are harvested before maturity when the seed fill 80% to 90% of the pod width. The pods are boiled and the seeds eaten as vegetables. These are especially popular in East Asia. Other products like tofu and miso also call for mature, large-seeded specialty soybean varieties. Small seeded varieties for natto and sprouts weigh less than 10 grams per 100 seed-1 (>4500 seeds pound-1); large seeded varieties for edamame etc. weigh more than 22 grams per 100 seed-1 (<2000 seeds pound-1). For comparison, seeds of normal varieties weigh from 12 to 18 grams per 100 seed-1 (3800 to 2500 seeds pound-1).

Grain yields of large- and small- seeded varieties are less than those of varieties with normal seed size. Large-seeded varieties yielded 82% of check varieties while small-seeded varieties yielded 72% of check varieties in a four-year University of Nebraska study. Seed weights were not greatly affected by either row spacing or seeding rate. Yield is a secondary consideration in production for specialty seeds because of their high value.

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